Annual Report on the Rare Diseases and Conditions Research Activities of the National Institutes of Health FY 2000
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National Heart, Lung, and Blood Institute (NHLBI)
Overview of NHLBI Rare Diseases Research Activities NHLBI provides leadership for a national program in the causes, diagnosis, treatment, and prevention of diseases of the heart, blood vessels, lungs, and blood, and sleep disorders; and in the uses of blood and the management of blood resources. Through research in its own laboratories and extramural research grants and contracts, NHLBI conducts and supports an integrated and coordinated program that includes basic investigations, clinical trials, epidemiological studies, and demonstration and education projects. While the major part of the research supported by NHLBI addresses common conditions such as hypertension, coronary heart disease, and chronic obstructive pulmonary disease, a significant amount of research is devoted to rare diseases in children and adults. NHLBI activities related to rare disease research in FY 2000 are described below. Recent Scientific Advances in Rare Diseases Research Heart and Vascular Diseases Program Abetalipoproteinemia Abetalipoproteinemia is a rare congenital disorder that prevents the body from producing low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and chylomicronsSlipoprotein complexes that carry dietary lipids (including cholesterol) from the lymph through the bloodstream. Individuals with abetalipoproteinemia are unable to digest fats properly. Other clinical findings include ataxia (lack of coordination), peripheral neuropathy, and several forms of nerve dysfunction. Genetic, biochemical, and metabolic approaches to studying this disease are supported by NHLBI at four institutions. In FY 2000, studies were directed at understanding abnormal synthesis of apolipoprotein B (apoB), the major protein in LDL, due to the absence of microsomal triglyceride transfer protein (MTP). Investigators have found that the amount of MTP may determine apoB levels. The region of apoB necessary for binding to MTP has been examined and a potential site identified. Inhibiting MTP-binding to apoB is associated with a marked decrease in the amount of apoB secreted from cells. Antiphospholipid Syndrome (APS) Patients with APS have circulating autoantibodies to certain phospholipids (lipids containing phosphorus), chiefly cardiolipin, as well as the lupus anticoagulant. APS manifests itself clinically by recurrent venous and arterial thrombosis, fetal deaths, and autoimmune thrombocytopenia. Many patients with APS have systemic lupus erythematosus (SLE), although patients may have APS in the absence of SLE. Further complicating the clinical picture is an increased incidence of atherosclerosis. Functional genomics has brought new focus to the study of APS. Research that will determine whether genetic factors predispose individuals to developing this unusual class of antibodies is under way . It is known that allelic variability in the genes for certain lipid carrier proteins also results in the generation of APS. NHLBI is supporting a study on the molecular genetics of one of these proteins, apolipoprotein H, in SLE patients to further our understanding of the link between SLE and the production of antiphospholipid antibodies. Several NHLBI grantees are engaged in efforts to develop more standardized imunoassays that will reliably detect individual antiphospholipids. Recent findings provide strong support for the involvement of antiphospholipid antibodies in atherogenesis. Autoreactive antibodies were found to form against phospholipid components of dead or dying (apoptotic) cells and were found to cross-react with normal vascular constituents that are produced in response to environmental stimuli, including bacteria. In other studies, small differences in a common lipid carrier protein appeared to be genetically linked to APS as well as to atherosclerosis. Arrhythmogenic Right Ventricular Dysplasia (ARVD) ARVD is a family of rare cardiomyopathies that result in sudden cardiac death and malignant heart rhythm disturbances, including fibrillation. Most forms are believed to be due to the inheritance of autosomal dominant mutations in genes with largely unknown identities, but which clearly affect myocardial integrity. ARVD is characterized by marked, selective, right ventricular dilatation, myocardial cell death, and cell replacement with fat cells and fibrous tissue. Expression in gene carriers is variable, but in those who display symptoms the outcome is frequently lethal. NHLBI is supporting work on ARVD at one of its Specialized Centers of Research (SCORs) in Sudden Cardiac Death and is providing guidance to another group on an amended application to study ARVD. The SCOR investigators have reported on the localization of a mutation to chromosome 10p12-14 in one family with a common congenital form of ARVD. Although the identity of the gene affected is not yet known, this is the first step in determining the molecular basis of this form of the disease. Bartter Syndrome Bartter syndrome, a rare autosomal recessive disease, typically manifests itself through salt imbalance and low blood pressure. Previous studies have shown that a single-gene mutation in the Na-K-Cl cotransporter is responsible for this disorder. One of the NHLBI SCOR programs in Molecular Genetics of Hypertension has found that the disease is genetically heterogeneous. In addition to the mutation on the Na-K-Cl co-transporter, mutations on potassium and chloride channels have been discovered, and there are indications that additional Bartter's genes remain to be found. The defect in salt homeostasis also has an impact on calcium handling, suggesting a strong linkage between salt and calcium homeostasis. The hypotensive state of Bartter syndrome suggests that these mutated genes protect against the development of high blood pressure. ß-Sitosterolemia ß-sitosterolemia is a rare genetic disease characterized by increased absorption of dietary cholesterol and plant and shellfish sterols. Patients with ß-sitosterolemia have a markedly increased risk of premature cardiovascular disease. An effective treatment for ß-sitosterolemia is not available, but ezitimibe, a cholesterol absorption inhibitor, is being evaluated as a new therapeutic. NHLBI's intramural Molecular Disease Branch is seeking to elucidate the genetic defect in ß-sitosterolemia and to develop a new approach to the treatment of the dyslipoproteinemia present in these patients. In FY 2000 the Branch established the genetic defect in ß-sitosterolemia as a defect in either the ABCG5 or ABCG8 transporters present in the enterocyte and liver. Brugada Syndrome Brugada syndrome is a rare inherited disorder characterized by cardiac electrophysiological abnormalities, specifically right bundle branch block and ST elevation in the precordial leads, and is associated with a high occurrence of sudden cardiac death. Brugada syndrome is currently believed to be similar in cause and potential treatment to some forms of long QT syndrome (LQTS). Both disorders appear to be caused by mutations at different locations in the SCN5A cardiac muscle sodium ion channel gene and resulting aberrations in depolarization of these cells. One group of NHLBI-supported investigators is studying the relationship between Brugada syndrome and another set of inherited arrhythmias known to be a major cause of sleeping deaths in young Asian and Indonesian men. A second group is studying new mutations of Brugada syndrome and potential modifiers of their variable expression in different family members. This group has identified a second site on chromosome 3 associated with Brugada syndrome and has extensively characterized cardiac electrical abnormalities in families with this mutation. Congenital Heart Disease Congenital heart disease affects about 8 in 1,000 live-born infants, or about 32,000 per year in the United States, making it the most common birth defect. Abnormal formation of the embryonic heart results in both structural and functional heart defects. Congenital heart disease is an important cause of infant mortality, pediatric and adult morbidity, and shortened adult life expectancy. About one-third of affected infants and children require open heart surgery or interventional cardiac catheterization to repair or improve their heart defects. Approximately the same proportion have extracardiac anomalies associated with the congenital heart defect, including chromosomal abnormalities and syndromes involving other organ systems. NHLBI has supported research in pediatric cardiovascular medicine since the Institute first funded heart research grants in 1949. Since that time, NHLBI-supported researchers have been instrumental in developing diagnostic imaging techniques, including fetal imaging; surgical techniques, including various operations and refinements in cardiopulmonary bypass; and medical therapies now used to ensure healthy survival for most affected children. NHLBI-supported researchers have made significant contributions to the epidemiology of congenital heart disease and to understanding the molecular and genetic basis of normal and abnormal heart development. This year, two NHLBI-supported researchers reported discovery of a genetic abnormality associated with congenital heart defects in mice. Although the defect has not yet been found in humans, understanding abnormal heart development in animal models will help to clarify the process in humans. Other researchers have been able to develop high-resolution ultrasound imaging for the characterization of hemodynamic function in the developing mouse embryo. Researchers funded through the SCOR Program in Pediatric Cardiovascular Disease have shown that mutations in a single human gene, Nkx2.5 , are responsible for a variety of structural congenital cardiovascular malformations, some of which are also associated with arrhythmias. DiGeorge Syndrome DiGeorge syndrome occurs with an estimated frequency of 1 in 4,000 live births. It is characterized by many abnormalities, including cardiac outflow tract anomalies, hypoplasia of the thymus and parathyroid glands, and cleft palate and facial dysmorphogenesis. It is usually caused by a heterozygous deletion of chromosomal region 22q11.2 (del22q11). NHLBI supports both human and animal studies of DiGeorge research through several grants, including two SCORs in Pediatric Cardiovascular Disease. Recent studies in mice implicate the transcription factor Tbx1 as a key candidate gene for the cardiac outflow tract defects seen in DiGeorge syndrome. Tbx1 is shown to be required for normal development of the pharyngeal arch arteries, parathyroid glands, and the conotruncal (outflow) region of the heart in mice. Mice missing one copy of this gene had problems analogous to those experienced in affected humans, and mice missing both copies had even more severe malformations. Doxorubicin (DXN) Cardiomyopathy DXN (brand name: Adriamycin) is a potent, broad-spectrum antitumor agent effective in treating a variety of cancers, including solid tumors and leukemia. Unfortunately, its clinical use is limited by dose-dependent cardiac side-effects that lead to degenerative cardiomyopathy, congestive heart failure, and death. In addition, patients treated with the drug many years ago when they were children are developing dilated cardiomyopathy. Endocardial biopsies from patients undergoing DXN therapy reveal a disruption of myofibrils, impairment of microtubule assembly, and a swelling of the endoplasmic reticulum. DXN cardiotoxicity is also characterized by a dose-dependent decline in mitochondrial oxidative phosphorylation and a decrease in high-energy phosphate pools. Several NHLBI-supported investigators have reported research advances in the past year. One investigator has focused on molecular genetic mechanisms involved in DXN cardiotoxicity in an in vivo rat model. The studies have demonstrated that DXN selectively deregulates the expression of cardiac-specific or cardiac-restricted genes by depleting the levels of tissue-specific transcription factors and cofactors, resulting in disruption of normal cardiomyocyte function. Another investigator has found that mitochondrial changes seem to contribute to the progressive inability of cardiac tissue to tolerate metabolic stress, particularly when associated with induction of the membrane permeability transition pore by DXN. That study is testing the hypothesis that DXN interacts with mitochondrial membranes to initiate a series of reactions that lead to increased rates of free radical generation. A third investigator is examining explicit pathways through which reactive oxygen species are involved in DXN-induced cardiomyopathy. Dysbetalipoproteinemia Dysbetalipoproteinemia is a rare disorder with a strong heritable component characterized by the presence of beta-migrating VLDL. Dysbetalipoproteinemia leads to formation of characteristic yellow skin plaque (xanthomas) and predisposes to early ischemic heart disease and peripheral vascular disease. Research into the genetics and the biochemical events underlying the etiology and pathophysiology of the disease is taking place under two investigator-initiated NHLBI grants. A mutant form of the protein apoprotein E (apoE2) has been identified as the primary molecular defect. Animal models are being developed to facilitate basic research on the disease. In FY 2000 these investigators used cell studies to demonstrate that apoE2 differs metabolically from other forms (apoE 3 and apoE4) in that its half-life (an indicator of the time the protein spends in the cell) is significantly higher. Familial Homozygous Hypercholesterolemia (FHH) FHH is a genetic defect in the LDL receptor that results in very high plasma levels of cholesterol and a marked increase in the risk of early heart disease. No effective treatment has been developed to treat these patients and definitively correct the molecular defect involved. NHLBI's intramural Molecular Disease Branch has a program directed toward the development of improved techniques for diagnosis, evaluation, and treatment of patients with FHH. New approaches are being studied to determine the extent of atherosclerosis in these patients. Both invasive and non-invasive techniques are being evaluated to establish which approach will be more effective in the selection of treatment programs to reduce the severe atherosclerosis characteristic of this disease. Familial Hypertrophic Cardiomyopathy (FHC) FHC is associated with myofibrillar disarray in the heart muscle, which leads to hypertrophy, or enlargement of the heart. Although patients can remain asymptomatic for some time, eventually shortness of breath, palpitations, and heart failure emerge, and sudden death ensues. Some patients die during childhood, whereas others survive for six or seven decades. FHC is associated with mutations in more than one protein, suggesting that the condition represents a heterogeneous group of disorders. During the past decade, scientists made significant progress in uncovering the genes associated with FHC. It is known, for instance, that FHC can be caused by various mutations in the contractile proteins that make up the heart wall. Understanding remains elusive, however, of who will die suddenly or whether certain factors such as high blood pressure or extreme stress will trigger sudden death. NHLBI supports research on the genetic basis and mechanisms involved through several investigator-initiated grants and in two SCORs in Heart Failure. Using a genetically engineered animal model for FHC, one NHLBI-supported investigator has shown decreased hypertrophy and a 36% reduction in fibrous tissue by using Losartan, an angiotensin II blocker. This is the first demonstration of a therapeutic effect on collagen and fibrous tissue. Until now, FHC in humans presenting without obstruction has been treated by using beta-blockers or calcium channel blockers, which serve only to ameliorate symptoms. By contrast, treating acquired heart failure with ACE inhibitors or angiotensin II receptor blockers has now been shown to prevent and/or reverse cardiac hypertrophy. These successful results in animal models lay the groundwork for clinical trials to evaluate such therapy for FHC. The same investigator has successfully used Doppler myocardial tissue imaging on the transgenic rabbit model of human hypertrophic cardiomyopathy (HCM) to detect those afflicted with FHC before hypertrophy develops. Studies are now under way in human families with FHC. Another investigator has produced two genetically engineered mouse models of FHC. Each model has a single-site mutation comparable to mutations observed in humans with FHC. The models will prove valuable in attempts to unravel the mechanism by which sarcomere protein gene mutations cause HCM. Familial Hypobetalipoproteinemia (FHBL) FHBL is an apparently autosomal dominant disorder of lipid metabolism characterized by very low levels of apoprotein B-containing lipoprotein cholesterol. NHLBI is supporting an investigator-initiated grant examining the genetic, biochemical, and metabolic aspects of this disease. FHBL is related to alterations in the apoB gene on chromosome 2p23-24. Specific mutations associated with FHBL have been identified and characterized. In hypobetalipoproteinemic patients with no detectable plasma signs of this defect, however, fewer than 5% have this particular apoB gene mutation. A genome-wide search has located other genes that may be responsible for FHBL. A newly identified genetic susceptibility for FHBL has been identified on chromosome 3 (p21.1-22), which has been narrowed down to an area containing three potential candidate genes. Infectious Myocarditis Infectious myocarditis, which affects both children and adults, is an inflammation of the heart muscle that sometimes leads to progressive heart failure and the need for heart transplantation. Post-mortem studies suggest that approximately 20% of the cases of this insidious, usually asymptomatic, disease result in sudden unexpected death in adults younger than age 40. Although many infectious agents have been linked to myocarditis, among the most common causes in the United States are Coxsackievirus and human immunodeficiency virus (HIV). Worldwide, the most common myocarditis is Chagas' disease, caused by the parasitic protozoan Trypanosoma cruzi . Animal studies have shown a causal link between viral myocarditis and the development of dilated cardiomyopathy. NHLBI supports basic studies on the cellular and molecular pathogenesis of infectious myocarditis. The studies include defining the role of the Coxsackievirus receptor in viral pathogenesis, studying if the innate immune response to Coxsackievirus influences whether the adaptive immune response leads to later development of autoimmune myocarditis, determining whether antimyosin antibodies and T cells in the disease are cross-reactive with viral or bacterial antigens, and examining the role of HIV and cocaine in infectious myocarditis. Using a primate model infected with simian immunodeficiency virus (SIV), a virus similar to HIV, an NHLBI-supported investigator has made a critical discovery regarding the pathogenesis of acquired immune deficiency syndrome- (AIDS-) related cardiac dysfunction; namely that cardiac myocytes are not the target for SIV. Instead, the virus may be infecting cardiac dendritic cells or monocytes, both of which bear the CD4 receptor required for viral infection. Studying the effects of a soluble viral regulatory factor called Tat, another investigator has found that Tat-mediated changes may create a pro-inflammatory stimulus, thereby increasing the morbidity of HIV infections. Liddle Syndrome Liddle's Syndrome is a rare autosomal dominant disorder of severe hypertension characterized by increased renal reabsorption of sodium resulting in hypokalemia, low plasma renin activity, and hypoaldosteronism. Liddle's Syndrome is ameliorated by amiloride, a drug that blocks sodium reabsorption and potassium excretion. Studies have shown that a mutation in the gene encoding the beta-subunit of the epithelial sodium channel in the distal renal tubule is responsible for this disorder. A diagnostic test for Liddle Syndrome is being developed by one of the NHLBI Specialized Centers of Research Programs on the Molecular Genetics of Hypertension. LQTS LQTS is characterized clinically by a prolonged QT segment on the cardiac electrocardiograph that is associated with syncope, ventricular arrhythmias, and frequently sudden cardiac death. This family of conditions is thought to be caused by alterations in the cardiac cell action potential induced by mutations in at least six cardiac ion channel genes. There are two principal forms of LQTS. The first occurs when cardiac symptoms spontaneously occur, as in the congenital autosomal dominant Romano-Ward syndrome and the autosomal recessive Jervell-Lange-Nielson syndrome, where affected individuals frequently have the same cardiac symptoms and congenital deafness. The second form is fiacquired LQTS,fl when individuals with normally silent mutations in some of these same cardiac ion channel genes are exposed to drugs that interact with one or more of the same ion channels involved in causing the unconditional congenital forms. In acquired LQTS following drug exposure, the symptoms and outcome are much the same as they are in the purely congenital, spontaneous form. NHLBI currently supports work through 1 SCOR on Sudden Cardiac Death grant and through at least 10 R01 grants that address the various molecular, clinical, and genetic bases of LQTS. One of these grants maintains an international registry of clinical and genetic data on 2,235 affected individuals in 936 families (104 of which were added this year). Researchers continue gene investigations worldwide to determine the numbers of affected individuals within the registry and to identify known and new mutations in registry members. LQTS researchers are also evaluating triggering factors for the malignant ventricular arrhythmias and are comparing these by genotype to ascertain if individuals with LQT1 have a different disease course than those with LQT2, LQT3, LQT4, or LQT5. In addition, another grant supports a small clinical trial of gene-directed pharmacotherapy for the LQT3 variant of the disease. NHLBI investigators recently summarized the functional and clinical consequences of the various ion channel deficiencies that have been discovered. Their report includes suggestions that mutations in calcium, sodium, and potassium channels may all cause similar cardiac electrical abnormalities, and that sodium channel inhibitors may be useful in treating patients with one form of the disease. Studies of clinical symptoms and their respective mutations are producing data that may be useful in identifying and treating patients with different forms of the disease. Pharmacogenetic studies on mutations involved in acquired LQTS have also provided information important in identifying and removing from the U.S. drug market a number of prescription and over-the-counter drugs that increase susceptibility to sudden death by these same mechanisms. Niemann-Pick Type C (NP-C) Disease NP-C disease is an autosomal recessive lipid storage disorder usually characterized by enlargement of the liver and spleen (hepatosplenomegaly) and severe progressive neurological dysfunction. Biochemical analyses of NP-C cells suggest an impairment in the intracellular transport of cholesterol to post-lysosomal destinations. The gene deficiency in Niemann-Pick disease types A and B has been identified as the acid sphingomyelinase. The gene deficiency in Niemann-Pick disease types C and D has been identified as the NP-C-1 protein, but few clues regarding its potential function(s) have been derived from its predicted amino acid sequence. The accumulation of cholesterol in NP-C results from an imbalance in the flow of cholesterol among membrane compartments. A putative cholesterol sensor in the plasma membrane that affects cholesterol trafficking into and out of cells was further characterized this year. The investigators are testing whether the cholesterol pool inside the cells is regulated by the plasma membrane sensor and whether the Golgi apparatus serves as an intermediary in cholesterol transport. Smith-Lemli-Opitz (SLO) Syndrome SLO syndrome is an inherited disorder caused by a defect in the enzyme involved in cholesterol biosynthesis. As a result, cholesterol synthesis is inadequate to meet biological demands for building cell membranes and bile acids. Newborns with SLO have a distinctive facial dysmorphism; suffer from numerous congenital anomalies, including cleft palate, congenital heart disease, genitourinary abnormalities, and malformed limbs; and have severe developmental delays, digestive difficulties, and behavioral problems. SLO syndrome is thought to account for many previously unexplained cases of mental retardation. Current NHLBI-supported research on SLO focuses on identification of relevant mutations, generation of animal models, development of sensitive and specific assays for screening newborns and verifying diagnoses in older individuals, clarification of aberrant biochemical pathways, and amelioration of behavioral and digestive problems through dietary and pharmacologic treatment. Some clinicians have posited that it may be necessary to add bile acids to the baby formula of SLO infants, but recent sterol balance findings in an NHLBI-supported study indicate that this is not a useful tack because bile acid synthesis occurs at normal levels. In another study, NHLBI-supported investigators improved the commonly used diagnostic and screening tests for SLO by improving the separation of accumulated unsynthesized cholesterol, thus achieving a more accurate determination of its concentrations in blood and other biological fluids such as amniotic fluid. Tangier Disease Tangier disease is a rare syndrome characterized by a deficiency of high-density lipoprotein (HDL), mild hypertriglyceridemia, neurologic abnormalities, and massive cholesterol ester deposits in various tissues such as the tonsils. Tangier disease is inherited as an autosomal co-dominant trait and appears to be due to excessive breakdown of HDL. Patients with Tangier disease have a defect in intracellular lipid trafficking that prevents removal of cholesterol from cells. The identification of a defective gene on chromosome 9 as causing Tangier disease has led to the concept of its product, the protein ABCA1 , as the gatekeeper for eliminating excess cholesterol from tissues and therefore a key determinant of the amount of cholesterol accumulating in the artery wall. NHLBI's intramural Molecular Disease Branch is systematically evaluating patients with low HDL to establish the frequency of genetic mutations in the ABCA1 transporter. Efforts by an NHLBI-supported investigator to understand the role of the protein in intracellular cholesterol trafficking recently led to the finding that the cellular location of ABCA1 was in areas distinct from the lipid-rich plasma membrane domains called rafts. Furthermore, the cholesterol transported out of the cell by ABCA1 does not appear to be from these lipid-rich rafts. Williams Syndrome (WMS) WMS is a rare genetic disorder characterized by a constellation of features such as mental retardation, aberrant cranial shape, unusually gregarious personality, premature wrinkling of the skin, dysmorphic facial features, short stature, colon and bladder diverticuli, dental maldevelopment, early joint laxity, late joint contractures, vocal cord abnormalities, and infantile hypercalcemia. It can also include supravalvular aortic stenosis (SVAS), a congenital vascular disorder generally diagnosed during infancy or childhood. It has been estimated that SVAS occurs in 1 in 20,000 live births. Narrowing of the ascending aorta is a dominant feature of SVAS, but other arteries (including the pulmonary arteries) are often affected. If not corrected through surgery, SVAS may lead to increased intracardiac pressure, myocardial hypertrophy, and heart failure. A NHLBI-supported study has established the elastin gene ( ELN ) as the locus for SVAS in both inherited and sporadic cases. Complete deletion of one form of the gene was found in more than 100 people with WMS. In mice missing one of the two copies of the ELN gene, the levels of gene products (messenger RNA and protein) were cut in half, even though their arterial functions remained near normal under usual blood pressure conditions. These mice showed increased numbers of elastic lamellae and smooth muscle cells (by 35%) as did humans (by 250%). These compensatory increases in muscular capability take place during arterial development. By contrast, the arterial pathology seen in mice missing both copies of the ELN gene is profoundly aberrant, with uncontrolled smooth muscle cell proliferation resulting in blockage of the artery. These findings occur in the absence of endothelial damage, thrombosis, or inflammation. This demonstration that hemodynamic stress is not a primary driving force of the pathology of SVAS/WMS suggests that elastin plays an important regulatory function in vascular smooth muscle cell development. Lung Diseases Program Advance Sleep Phase Syndrome (ASPS) ASPS is a genetically based sleep disorder characterized by early evening onset of sleep and spontaneous early awakening with normal sleep duration. NHLBI supports basic research to elucidate the biological clock mechanism, the neural pathways through which the clock regulates sleep, immune, and other functions; clinical research on the role of circadian factors and sleep-regulating hormones in sleep disorders and the timing of sleep; and applied research on the role of the biological clock in disturbed sleep and alertness of shift workers, school-age children, and drowsy drivers. ASPS has been linked to a variant of the biological clock gene, hPer2 (HL59596). This genetic basis of ASPS was determined by linkage analysis of a single family where many related individuals exhibited a large four-hour advance of sleep, temperature, and melatonin rhythms. Genetic studies identified a single base mutation that alters the ability of hPer2 to interact with other components of the biological clock. The hPer2 mutation linked to ASPS is hypothesized to advance the biological clock by accelerating the accumulation of other gene products composing the biological clock. Alpha-1-Antitrypsin (AAT) Deficiency AAT deficiency is an inherited deficiency of a circulating proteinase inhibitor that is manufactured primarily in the liver. Deficiency states (circulating serum AAT levels below 0.6 mg/ml) are associated with emphysema, presumably from inadequate protection against enzymatic destruction by neutrophil elastase. Fifteen percent of the AAT-deficient population also develop liver disease. NHLBI currently funds a variety of clinical and basic research on AAT deficiency, including study of the molecular mechanisms that impair secretion of AAT, methods of gene therapy delivery, and how to increase the availability of defective but partially active AAT. NHLBI-supported investigators are defining the abnormalities and degradation pathways of the AAT protein and the associated inflammation that leads to disease in various AAT-deficiency states. One new therapy in the early stages of investigation is the enhancement of partially active mutant protein transportation through the liver. In addition to research that specifically focuses on AAT, NHLBI supports related studies addressing the general causation of emphysema; the function, synthesis, secretion, and interaction of enzymes similar to AAT; animal models of other enzyme deficiencies; gene regulation and therapy; and cellular transport, signaling, injury, and repair. The Institute also continues to support an AAT patient registry. Asbestosis Asbestosis, an occupational lung disease, is the interstitial pneumonitis and fibrosis caused by exposure to asbestos fibers. In response to the deposition of asbestos fibers, macrophages and lymphocytes accumulate, type II alveolar epithelial cells and smooth muscle cells proliferate, fibrosis appears in the adjacent walls of respiratory airways, and septa thicken. NHLBI-supported researchers are investigating the molecular and cellular events that trigger cellular accumulation and proliferation and that regulate the remodeling of lung tissue that results in fibrotic lesions. Bronchopulmonary Dysplasia (BPD) BPD is a chronic lung disease characterized by disordered lung growth with changes in cell size and shape and a reduction in the number of alveolar structures available for gas exchange. It affects at least 10,000 very-low-birth-weight (VLBW) infants each year and is associated with neonatal intensive care costs of approximately $30,000 to $60,000 per individual. The incidence of this disease has increased in recent years due to the increased survival of smaller premature infants. NHLBI's program in developmental lung biology supports basic and clinical research to close the gaps in our understanding of BPD and identify treatment opportunities. The Collaborative Program for Research in BPD provides a well-characterized primate model of BPD for a multidisciplinary exploration of its etiology. This year NHLBI was able to support two new clinical trials to evaluate the role of nitric oxide (NO) in preventing and treating chronic lung disease in premature infants. This represents an opportunity to confirm findings from the SCOR Program in the Pathobiology of Lung Development that identified NO as an important regulator of lung circulation during development. Together, these clinical studies are expected to yield definitive information about NO's utility and "window of therapeutic opportunity" to prevent chronic lung disease in VLBW premature infants. Recent progress by the Collaborative Program for Research in BPD includes identification of a new marker (bombesin peptide) that is predictive for the development of BPD and will allow identification of infants at particular risk for BPD. An antibombesin antibody, long-used in cancer treatment, has already been shown to prevent development of BPD in an animal model of the disease and is scheduled for a clinical trial in high-risk human infants. This may ultimately provide a beneficial, cost-effective intervention to decrease the incidence of BPD. Other exciting results indicate that early delivery of a recombinant antioxidant enzyme to human infants at high risk for BPD reduces lung injury when infants are re-examined at age 1. Delivery of a synthetic antioxidant has also been found to be prophylactic against the development of BPD. The recent discovery that retinoic acid, a relative of vitamin A, can stimulate regeneration of alveoli in models of BPD suggests that at least some of the detrimental processes involved in aberrant lung development are reversible. Studies funded by a new RFA program, "Strategies to Augment Alveolization," are also expected to yield information essential to understanding the complex issues surrounding the role of vitamin A and corticosteroids in regulating lung growth. Churg-Strauss Syndrome Churg-Strauss syndrome is a rare disorder that was first reported in the 1950s. It is characterized by the formation and accumulation of an abnormally large number of certain white blood cells (eosinophils), inflammation of blood vessels (angiitis or vasculitis), and inflammatory nodular lesions (granulomatosis). Onset typically occurs from ages 15 to 70 years, and the disease affects both males and females. Patients with the syndrome are often affected by asthma. Churg-Strauss syndrome can be severely debilitating and even fatal if untreated, but patients usually respond well to corticosteroid treatment. More than 90 cases of Churg-Strauss syndrome have been reported in less than 2 years by physicians who had switched asthma patients from corticosteroid therapy to antileukotriene therapy. It is unclear whether the increased reports of Churg-Strauss are the result of an untoward effect of the antileukotriene therapy or a primary eosinophilic disease that had been clinically recognized and treated as asthma but was "uncovered" as Churg-Strauss after the corticosteroid therapy was withdrawn. NHLBI does not currently support research specifically investigating Churg-Strauss syndrome; however, it does support numerous investigator-initiated grants studying the basic mechanisms of asthma, including examination of the role of eosinophils. NHLBI also supports clinical studies of severe asthma and of medications used in asthma management, such as antileukotriene therapy. Congenital Diaphragmatic Hernia (CDH) CDH is a developmental disorder that occurs once in every 2,400 births. CDH often occurs in isolated fashion, i.e., it is not associated with other life-threatening anomalies or chromosomal aberrations. Neonates with the disorder typically die soon after birth because lung tissue compressed by the herniated viscera is inadequately developed, and hypoplasia of the pulmonary vascular bed leads to pulmonary hypertension or persistent fetal circulation syndrome. NHLBI supports an investigator-initiated clinical study that will test the efficacy of an in utero surgical technique to correct lung hypoplasia in a group of human fetuses with the most severe form of CDH. The goal of the study is to determine whether temporary tracheal occlusion at 24-28 weeks gestation enlarges the hypoplastic fetal lung and improves the odds ratios for survival and various quality-of-life indices. Cystic Fibrosis (CF) CF is a multisystem disease characterized by defective transport of chloride and sodium across the cell membrane. More than 25,000 Americans have CF, with an incidence of about 1 in 3,300 among Caucasian births. CF is the leading genetic cause of death for children and young adults, with 90% of the deaths due to pulmonary complications. The responsible gene, the CF transmembrane conductance regulator ( CFTR ), was identified in 1989. More than 800 mutations and DNA sequence variations identified in the CFTR gene contribute to a highly variable presentation and disease course. NHLBI supports a vigorous program of basic, clinical, and behavioral research focused on the etiology, pathophysiology, and treatment of CF, specifically in relation to pulmonary manifestations. Despite the promise of adeno-associated virus (AAV) as a delivery vehicle for human gene therapy, a major shortcoming has been its limited capacity to carry large genes such as the CFTR . Recent breakthroughs in the engineering of viral vectors allow larger genes to be delivered by splitting them into two parts and packaging the parts into separate, complementary AAV vectors, one containing the genetic information coding for the protein and the other containing the genetic material for the control elements that cause the therapeutic protein to be expressed. When the two parts of the virus simultaneously enter a cell, their genetic materials "join hands" and allow for high-level production of the therapeutic protein. This approach holds great promise for the future of gene therapy for CF. Pseudomonas aeruginosa is the main cause of chronic lung infection leading to lung failure in individuals with CF. NHLBI-supported studies are providing insight into how P. aeruginosa endures for long periods in the lung and how it can be controlled. The bacteria were recently shown to form, through a process called quorum-sensing, a protective outer layer, or biofilm, on the lungs of CF patients, serving to protect the bacteria from conventional antibiotics and the body's natural immune responses. The biofilm allows the bacteria to remain in the CF lungs, causing life-long P. aeruginosa infections. By studying the biofilm signaling process and how to interrupt it, scientists hope to be able to render the organism susceptible to traditional treatment methods. Importantly, these quorum-sensing signals may serve as a biomarker in screens to identify agents that interfere with cell-to-cell communication and biofilm development. When used in chewing gum or as a syrup, xylitol, a non-ionic osmolyte that lowers salt concentrations without providing an energy source for bacteria, has been reported to decrease or prevent dental caries and acute otitis media. NHLBI-supported research recently explored the effectiveness of xylitol in enhancing bacterial killing when applied to the airway surface. Xylitol was found to lower the airway surface liquid salt concentration in both CF and non-CF airway epithelia in vitro, enhancing the activity of endogenous airway antimicrobial substances and decreasing bacteria. Furthermore, in a controlled trial in nasal airway epithelia of normal subjects, xylitol was found to result in a significant decrease in the number of staphylococci present in the nasal passages. Although xylitol may be of little value in treating infections once established, these promising results suggest that it may provide an important new therapeutic to prevent or slow the onset of bacterial infection in CF. Idiopathic Pulmonary Fibrosis (IPF) IPF is a rare chronic lung disease of unknown cause affecting between 3 and 30 individuals per 100,000 population. Individuals with IPF develop abnormal, excessive scarring that can cause progressive shortness of breath and coughing. Currently available treatments, most commonly with corticosteroids in combination with other potent drugs, and less commonly with lung transplantation, do little to prevent a relatively rapid death in most patients. NHLBI-supported research on IPF is examining the molecular and cellular events that trigger the inflammation of alveoli seen in the early stages of the disease and that influence progression to the irreversible, fibrotic end-stage. Three NHLBI intramural observational clinical research protocols focusing on the natural history and pathogenesis of IPF are open for enrollment of subjects with familial and non-familial forms of IPF. NHLBI's intramural program has established collaborations with extramural sites and is working with the Pulmonary Fibrosis Association and other patient-support organizations to recruit patients. NHLBI-supported investigators comparing occupational exposures in 248 IPF patients with those in 491 control subjects reported this year on significant correlations with farming, livestock, hairdressing, metal dust, bird-raising, stone-cutting, stone-polishing, vegetable dust, and animal dust. The results confirm previous findings that dusty environments lead to an increased risk of IPF. Lymphangioleiomyomatosis (LAM) LAM is a rare lung disease that affects girls and women from puberty through menopause. Symptoms develop as the result of proliferation of atypical, non-malignant smooth muscle cells in the lungs. Diagnosis is usually made by lung biopsy or by specialized chest radiographs. Common symptoms include shortness of breath, cough, and sometimes coughing up blood. Patients often develop spontaneous pneumothorax (collapse of the lung) or chylous pleural effusion (collection of milky-looking fluid around the lung). Patients may present with abdominal tumors containing abnormal smooth muscle cells similar to those in the lungs. The clinical course of LAM is quite variable, but is usually slowly progressive, eventually resulting in death from respiratory failure. Although no treatment has been proven effective in halting or reversing LAM, lung transplantation is a valuable treatment for patients with end-stage lung disease. NHLBI supports research on LAM in both its intramural and extramural programs. As part of the intramural program, NHLBI has established a basic and clinical research laboratory at the NIH Clinical Center (CC) to learn more about the cause and progression of LAM at the clinical, cellular, and molecular levels. More than 225 patients have been enrolled in the study. Researchers are determining the characteristics of the unusual smooth muscle cells that damage the lungs of LAM patients. A prospective study within NHLBI's intramural program demonstrated that a large percentage of women with tuberous sclerosis complex (TSC), a genetically transmitted disease, develop lung lesions identical to those seen in LAM. In some cases, the clinical distinction between TSC and LAM may be difficult. Both men and women with TSC develop lung nodules due to the abnormal proliferation of pneumocytes. These nodules do not appear to be present in women with LAM but without TSC . Examining genetic mutations found in cells taken from the lungs and kidneys of LAM patients to determine how TSC and LAM are linked, one NHLBI-supported investigator, discovered that mutations in the tuberous sclerosis complex gene TSC2 can cause pulmonary LAM. This research may lead to new diagnostic and therapeutic strategies. An important focus of NHLBI's intramural research is learning how growth is regulated in LAM cells. Individual LAM cells isolated from patients have been expanded into colonies. These cells are clonal and have abnormalities in their tuberous sclerosis genes consistent with a role for the genes in the growth of abnormal smooth muscle cells. Although biomarkers have not been identified that predict the course of the disease in any individual patient, the natural history study has demonstrated that time to lung transplant can be estimated from specific pulmonary function tests, lung biopsy, and radiographs. In other scientific advances of note, an immunohistochemical analysis suggests that the production of proteins that inhibit cell death in LAM cells may be controlled by hormones. Down-regulation of estrogen and progesterone receptors has been reported following therapy. These studies may provide clues to understanding the imbalance that causes cell overgrowth. Also under investigation is how a family of destructive enzymes in the lung, known as matrix metaloproteinases, may lead to progression of LAM. NHLBI and ORWH support a national LAM Patient Registry that is coordinated by the Cleveland Clinic Foundation. Patients can be enrolled through six major centers (including the NIH CC) or by their personal physicians. By the end of FY 2000, the registry had enrolled more than 200 LAM patients. Persistent Pulmonary Hypertension of the Newborn (PPHN) PPHN affects approximately 1 in 1,250 live-born term infants. Due to inappropriate muscularization of fetal pulmonary vessels, the lung arteries of affected newborns fail to dilate after birth to allow for normal blood flow to the lung. These infants are poorly oxygenated and require costly and prolonged medical care, including intubation of the airway, inhalation of 100% oxygen, mechanical ventilation, and, often, heart/lung bypass (extracorporeal membrane oxygenation). Two NHLBI SCORs on the Pathobiology of Lung Development are focused on identifying the basic molecular mechanisms involved in the development of PPHN. A recently funded clinical study will address maternal risk factors such as cigarette smoking and antenatal exposure to the non-steroidal anti-inflammatory drugs aspirin and ibuprofen. Experimental evidence consistently suggests that maternal exposure to these agents plays a role in the etiology of PPHN and thus influences the incidence of the disorder in term infants. This multicenter, case-control study (560 infants with PPHN with 4 controls each) will also collect and store buccal cell specimens for future genetic analyses, should a relationship be demonstrated. One experimental therapy that offers promise of less invasive treatment is inhaled NO. Recent studies point to a critical role for endogenous NO as a modulator of levels of vasoactive mediators whose net balance determines pulmonary vascular tone and reactivity. There are three known isoforms of NO synthase (NOS) in mammals, all of which are developmentally regulated in the fetal lung. Understanding the molecular mechanisms by which NO is released under hypoxic conditions may have important implications for the treatment of PPHN. Other investigators supported by the program have demonstrated that treatment of neonatal rats with the synthetic adrenocortical steroid dexamethasone causes lung hypoplasia, decreases alveolization, and results in an increase in the development of subsequent pulmonary hypertension. Their results demonstrate the importance of temporo-spatial relationships in the coordination of vascularization and cardiopulmonary development and the limits of our understanding of those relationships. Primary Ciliary Dyskinesia (PCD) PCD, also known as Kartegener's syndrome or immobile ciliary syndrome, is an inherited disease characterized by defects in the cilia lining the respiratory tract. The result is impaired ciliary function, reduced or absent mucous clearance, and susceptibility to chronic, recurrent respiratory infections, including sinusitis, bronchitis, pneumonia, and otitis media. The disease typically affects children ages 0 to 18, but the defect associated with this condition also has variable clinical impact on disease progression in adults. Many patients experience hearing loss, male infertility is common, and situs inversus (having organs on the opposite side from usual) occurs in approximately 50% of PCD patients. Clinical progression of the disease is variable, with lung transplantation required in severe cases. For most patients, aggressive measures to enhance clearance of mucus, prevent respiratory infections, and treat bacterial superinfections are recommended. Although the true incidence of the disease is unknown, it is estimated to be 1 in 32,000 or higher. Although PCD has been the focus of many scientific investigations, little progress has been made in identifying its genetic cause. Recent advances in the areas of protein biochemistry and cell culture of airway epithelial cells may now enable new insights into the genetic basis of PCD and increased understanding of its pathogenesis. Several NHLBI-supported studies are seeking to identify defects in the cilia of PCD patients at the level of individual proteins and ultimately to identify mutations responsible for some cases of PCD. Another NHLBI-supported study is identifying and characterizing a regulatory protein, HFH-4 , expressed specifically in ciliated epithelial cells. Preliminary findings with a mutant mouse lacking this protein suggest that the protein has a role in the regulation of the early development of cilia (ciliogenesis) and that cilia function is critical in left-right body axis symmetry. Mice lacking HFH-4 did not have cilia and had situs inversus, thus providing the first genetic evidence that ciliogenesis and regulation of left-right symmetry are linked. Primary Pulmonary Hypertension (PPH) PPH is a rare progressive lung disorder characterized by a sustained elevation of pulmonary artery pressure. Although PPH can occur in either gender and begin at any age, it usually affects girls and women between puberty and menopause. Estimates of the prevalence of PPH range from 1 to 2 individuals per million population. PPH is associated with structural changes in the small pulmonary arteries and arterioles, resulting in resistance to blood flow. The process eventually leads to an enlarged, overworked right ventricle that is unable to pump enough blood to the lungs, resulting in heart failure and death, usually within 3 to 5 years of initial diagnosis. Although medical treatment for PPH has improved over the past decade, no therapeutic approach is uniformly accepted or successful. NHLBI supports basic research on the cellular and molecular events underlying the pathogenesis of PPH. The dominant themes of this research are: 1) isolation and characterization of a familial PPH gene, 2) better understanding of the structural aspects of the disease that cause proliferative and obliterative changes in the vasculature, 3) identification of genetic factors that affect functional and structural changes in the vasculature, and 4) identification and evaluation of more effective treatments. At least 6% of subjects diagnosed with PPH have a known family history of the disorder. Familial PPH (FPPH) segregates as an autosomal dominant trait with incomplete penetrance, meaning that individuals could inherit the gene but not display symptoms of the disease. Recently, two research groups independently identified germline mutations in the bone morphogenetic protein receptor II ( BMPR2 ) gene in patients with the disease. BPMR2 belongs to a family of proteins responsible for a wide variety of cellular functions in embryogenesis, vasculogenesis, angiogenesis, hematogenesis, immune regulation, and wound healing. The mutations were varied and distributed across the gene, and none of them were detected in control chromosomes. Familial and sporadic PPH share similar histopathological features and follow a similar clinical course, suggesting a common genetic basis. In some families, parental transmission was observed, showing that family members without the disease can harbor the mutations and suggesting that FPPH is under-diagnosed. Since not all patients with PPH have BMPR2 mutations, other genetic events may occur in their lungs. A recent study reported that endothelial cells from the lung tissue of sporadic PPH patients acquire somatic mutations from other genes involved in endothelial cell growth and apoptosis. Pulmonary Alveolar Proteinosis (PAP) PAP is a rare lung disease characterized by accumulation of lipoproteinaceous material within the alveoli. The congenital form of the disease is fatal and occurs in 1 per 100,000 live births. The pathophysiologic basis of congenital PAP is associated with a mutation in the gene for surfactant protein B, leading to synthesis of inadequate quantities of normally functioning surfactant protein B. The cause of adult onset PAP is not well-characterized and may be associated with the heterozygous condition for a mutation in SP-B , a deficiency of granulocyte-macrophage colony-stimulating factor, or a variety of conditions such as silicosis and certain types of malignancies. NHLBI supports investigator-initiated studies to determine the molecular basis for the development of PAP and the incidence of mutations responsible for congenital PAP. Molecular analyses of cord blood specimens collected by health departments in various states and abroad as components of birth and death certificate data are being analyzed to determine the frequency of relevant SP-B mutations among populations of varied ethnic composition. Sarcoidosis Sarcoidosis is a chronic, multisystem disease of unknown cause in which affected organs, especially the lungs, are invaded by different types of inflammatory cells that become organized into clusters of cells called granulomas. Sarcoidosis affects people of all ages, sexes, and races, although higher incidences are reported for young adults and African Americans. The illness can be self-limited or chronic with episodic outbursts and remissions. In some patients, the disease is characterized by a chronic interstitial pneumonitis accompanied by progressive deterioration of lung function associated with scarring, fibrosis, and permanent destruction of lung tissue. The estimated prevalence of patients with sarcoidosis ranges from 13,000 to 130,000, and the estimated incidence of new cases ranges from 2,600 to 27,000 per year. Corticosteroids are currently the primary treatment for active pulmonary sarcoidosis, but they often produce undesirable side-effects. NHLBI's intramural research program has initiated a randomized, double-blind, placebo-controlled clinical protocol to determine if pentoxifylline, a xanthine derivative that has been used for many years in the treatment of peripheral vascular disease, can be beneficial as an adjunct to corticosteroid therapy in patients with pulmonary sarcoidosis. The same group is also attempting to identify genetic polymorphisms and modifier/susceptibility genes that may be important in the development and/or clinical course of sarcoidosis. NHLBI's extramural program supports basic research on sarcoidosis designed to further understanding of granuloma formation, and clinical research intended to improve understanding of the initiating events and natural history of sarcoidosis and the contribution of susceptibility genes to its development. In recent studies, histologic and clinical similarities between tuberculosis and sarcoidosis have suggested a shared underlying pathophysiology. The NRAMP1 human protein has been associated with increased susceptibility to tuberculosis in some human populations. Its role in susceptibility to sarcoidosis was studied by comparing variations in the NRAMP1 gene in 157 African American sarcoidosis patients to variations in 111 African American control subjects. Contrary to the previous findings in tuberculosis patients, the less common gene variations were found more often in control subjects than in sarcoidosis patients, and one variation was actually found to have a protective effect. Sudden Infant Death Syndrome (SIDS) SIDS is the diagnosis given for sudden death of an infant younger than 1 year that remains unexplained after a complete investigation, including an autopsy, examination of the death scene, review of the symptoms or illnesses the infant had before death, and consideration of any other pertinent medical history. SIDS is also commonly known as crib death. Abnormalities in neural functions regulating breathing, blood pressure, and waking during sleep are thought in many cases to contribute to SIDS risk. Recent studies indicate that inheritable factors place infants with apneic parents or siblings at increased risk. NHLBI supports basic research on the development of fundamental neurobiological mechanisms regulating chemosensitivity, ventilatory rhythm, and blood pressure, and clinical research to identify genetic and epidemiological factors associated with SIDS risk. Blood Diseases and Resources Programs Acute Graft-versus-Host Disease (GvHD) Acute GvHD is a condition that typically occurs within 3 months after allogeneic hematopoietic stem cell transplantation, when donor T cells react against "foreign" tissue antigens in the recipient. Acute GvHD is characterized by skin rash, liver dysfunction, vomiting, and diarrhea, and often precedes development of chronic GvHD, which may require treatment with immunosuppressive drugs for several years. NHLBI supports basic and clinical research to understand the pathophysiology of GvHD, especially in unrelated transplants, with emphasis on the roles of both major and minor histocompatibility antigens in disease pathogenesis, development of tolerance, function of donor T cells in allogeneic hosts, and mechanisms of GvHD prevention, including depletion of donor T cells from the graft. NHLBI also supports two multicenter clinical studies: the Unrelated-Donor Marrow Transplant Trial of T-Cell Depletion and the Cord Blood Banking and Transplantation Study. Other studies are examining the variables that affect GvHD induction and severity, its effector mechanisms, and whether GvHD can be suppressed while other necessary immune responses are maintained. Answers to these questions may lead to the design of successful approaches for intervention. Combining data from their respective registries, the International Bone Marrow Transplant Registry and the Eurocord-Cord Blood Transplant Group compared results of sibling umbilical cord blood (UCB) and bone marrow transplantation for a group of patients younger than 15 years. Their study found that although engraftment (the time for new white blood cells and platelets to grow in the recipient) was longer in the UCB recipients, the incidence of GvHD was lower, and the overall survival was the same. The results suggest that unrelated umbilical cord blood compares favorably with unrelated donor marrow. Aplastic Anemia (AA) and Paroxysmal Nocturnal Hemoglobinuria (PNH) AA is a form of bone marrow failure in which hematopoietic cells are replaced by fat, resulting in low blood counts. In PNH, a clone derived from a single hematopoietic stem cell expands, leading to marrow failure, red blood cell destruction, and venous thrombosis. NHLBI's intramural Hematology Branch has a large clinical and laboratory program devoted to bone marrow failure syndromes, including AA and PNH. Bench studies include immunology, cell biology, virology, and molecular biology approaches to the failure to produce blood cells. Clinical studies include therapeutic interventions to reduce autoimmunity in patients with AA. Using sensitive flow cytometry, the Branch has established that an expanded PNH clone is present in a large proportion of patients with AA. In a randomized trial to compare conventional antithymocyte globulin immunosuppression to high-dose cyclophosphamide, the Branch established that the latter treatment is excessively toxic and leads to a high rate of severe fungal infections and increased mortality. Cooley's Anemia Cooley's anemia (also called beta-thalassemia, thalassemia major, or Mediterranean anemia) is a genetic blood disease that results in an inadequate production of hemoglobin. Individuals affected by Cooley's anemia require frequent and lifelong blood transfusions. Because the body has no natural means to eliminate iron, the iron contained in the transfused red blood cells builds up over many years and eventually becomes toxic to tissues and organ systems. In addition, many affected children have acquired other diseases such as hepatitis through years of transfusion exposure. NHLBI's extramural research efforts related to Cooley's anemia include:
Continued support of research protocols for efficient identification and targeting of hematopoietic stem cells, information on how ex vivo manipulation of stem cells alters their biologic properties, and improved vectors will significantly contribute to treatment of Cooley's anemia. NHLBI's strategic approach to the disease also includes programs in therapy development as well as a clinical research network to test new therapies. Another avenue of research is an ambitious study of sibling donor cord blood banking and transplantation for hemoglobinopathy families. FY 2000 has witnessed a number of important scientific advances in this area:
Creutzfeldt-Jakob Disease (CJD) CJD is a slow degenerative disease of the central nervous system characterized by motor dysfunction, progressive dementia, and vacuolar degeneration of the brain. The disease is rare but invariably fatal, and has been associated with a transmissible agent. A protease-resistant protein or prion is the hallmark of the transmissible spongiform encephalopathies (TSEs) to which CJD belongs, thus leading to the term "prion diseases" for this group of neurodegenerative illnesses that include bovine spongiform encephalopathy (BSE or "mad cow disease"), scrapie in sheep, and chronic wasting disease in deer and elk. Prion diseases may cross the species barrier, the most notable example being the recent cases of new-variant CJD in humans caused by consumption of beef contaminated with BSE. Classic CJD occurs worldwide at a rate of 1 to 2 cases per million per year. In FY 1999, NHLBI initiated a high-priority program to address the lack of a rapid, sensitive, and specific assay for TSE infectivity. Such assays could form the bases of a blood/tissue donor screening test and could additionally provide a diagnostic test for neurologists, since currently there is no way of detecting disease in the preclinical stage. The assays could also be useful in testing for TSE in animals, especially in domestic animals used for human consumption. Fanconi Anemia (FA) FA is an autosomal recessive bone marrow failure syndrome characterized by a decrease in blood cells and platelets (pancytopenia), developmental defects, and cancer susceptibility. Approximately 75% of FA patients can be identified at birth because of congenital anomalies, while the remaining 25% have no birth defects. FA is a clinically heterogeneous disorder and can currently be divided into at least eight different complementation groups, designated A through G. Two FA genes, FAC and FAA , have been cloned and account for an estimated 75% of all FA patients worldwide. As noted above, eight distinct complementation groups (designated FAA-FAG) have been reported, suggesting that at least eight genes are involved in the manifestations of FA. Localization and functional studies to delineate the interrelationship of FA proteins and their functions are a high-priority research area for NHLBI. The Institute supports research on the identification and cloning of the remaining FA genes, protocols for efficient identification and targeting of hematopoietic stem cells, studies of how ex vivo manipulation of stem cells alters their biologic properties, and development of improved vectors to enhance the potential for a cure. NHLBI is currently supporting an investigatorinitiated cooperative agreement to conduct sibling donor cord blood banking and transplantation. With the indications for bone marrow transplant of FA patients continually growing and with new evidence of the benefits of cord blood transplants, this promises to be an important endeavor. NHLBI's intramural Hematology Branch program in FA has three foci: 1) development of hematopoietic stem cell gene therapy for FAC and FAA, 2) analysis of transgenic and knockout mice in order to gain an understanding of the pathophysiology of bone marrow failure and cancer predisposition, and 3) characterization of the molecular function of the cloned FA gene. A number of studies over the past year have further defined the FA complex of proteins and provided insight into their potential function. Exciting developments include cellular localization of the functional complex and determination of the role of the complex in DNA repair and prevention of mutagenesis. Recent transplantation protocols using Fludarabine have provided new hope that stem cell transplantation may become a therapeutic option for patients with FA. Hemophilia Hemophilia is a hereditary bleeding disorder that results from a deficiency in either blood coagulation factor VIII or factor IX. About 20,000 individuals are affected in the United States, all of whom are dependent on lifelong treatment to control periodic bleeding episodes. Approximately 20% of severe hemophilia patients develop antibody inhibitors that specifically neutralize the replacement factor and complicate treatment. The adult hemophilia population has been severely affected by blood-borne infectious agents in plasma-derived replacement products. More than 80% of them have been infected with hepatitis virus, and approximately 20% of them have been infected with HIV. NHLBI supports a broad spectrum of activities on blood coagulation and its disorders. The research addresses viral and non-viral approaches for gene therapy, mechanisms of antibody inhibitor formation, modification of factors for improved therapeutics, safety of plasma-derived products, and blood product-associated infections. In addition, basic genetic, molecular biology, and protein biochemistry studies of factor VIII and factor IX are supported to improve understanding of their mechanism and regulation. Gene therapy studies by NHLBI-supported scientists have shown sustained expression of factor IX in mice and hemophilic dogs after muscle injection or intraportal administration of AAV vector-containing factor IX. Preliminary results of the first phase I clinical study for AAV-mediated muscle directed gene transfer of factor IX indicate that the procedure is well-tolerated and show evidence of protein expression. On the basis of pre-clinical safety and efficacy data, a clinical study for intrahepatic delivery of AAV vector-expressing factor IX has been proposed. Hereditary Hemorrhagic Telangiectasia (HHT) HHT, also called Osler-Weber-Rendu disease, is a bleeding disorder that is due to weakness of the vascular support structure. HHT's most common manifestations are red spots on the lips and bleeding from mucosal membranes such as in the nose. In an advanced stage, there are often arterio-venous malformations in the lung, brain, gut, and liver. Two gene defects have been identified in patients with HHT. One is in the gene associated with the protein endoglin, and the other is in a gene related to activin receptor-like kinase. A correlation between the gene defect and organ susceptibility to the disease may exist. Diagnosis of patients with HHT, particularly at an early age, is difficult because multiple organs are affected. Establishment of a genetic linkage may allow earlier diagnosis and improved treatment. NHLBI supports a broad spectrum of research in hemostasis and thrombosis that is focused in part on understanding the biology of platelet activation, the mechanism of clotting, and the interaction of blood with the vascular surface. Progress has been made in determining the underlying molecular basis of HHT, which appears to be a mutation in the genes of two TGF beta-receptor family members on the endothelial cell. The type I receptor (Alk-1) and the type III receptor (endoglin) have been identified, while a rare type II receptor remains unknown. Eight mutations in endoglin leading to HHT have been identified, and a database on genetic mutations related to HHT has been established. This suggests a critical role for the TGF-beta signal transduction pathway in capillary morphogenesis and the pathology of this disease. Immune Thrombocytopenic Purpura (ITP) ITP is an autoimmune disease manifested by production of antibodies that react with specific proteins on the surface of platelets. The reaction results in rapid clearance or destruction of the platelets (thrombocytopenia) and clinically significant bleeding. The underlying cause is unknown, but ITP is associated with other autoimmune diseases. Acute (temporary) thrombocytopenic purpura is most commonly seen in young children. About 85% of children recover within 1 year and the problem does not return. Thrombocytopenic purpura is considered chronic when it has lasted more than 6 months. Its onset may occur at any age, adults more often have the chronic disorder, and females are affected two to three times more than males. Most adult patients respond at least transiently to standard therapies, including steroids and splenectomy, but a majority eventually relapse, and some develop very severe chronic refractory ITP. Part of the NHLBI research program on thrombosis and hemostasis is directed toward understanding the biology of platelet production from megakaryocytes, the function of the growth factor thrombopoietin, and the structure and function of platelet surface glycoprotein antigens. Research in FY 2000 showed that the transcription factor GATA-1 is necessary for megakaryocyte maturation and platelet production. Subtractive hybridization experiments between megakaryocytes lacking GATA-1 and controls show that the 4-Ptase I enzyme is essential for this process. Application of phage display technology has led to progress in the identifying genetic mechanisms involved in the formation of antibodies to platelets. A transgenic mouse model of thrombocytopenia has been developed and should be useful in research and development of drugs for ITP. NHLBI's intramural Hematology Branch has enrolled 14 adult patients with severe ITP in a transplantation protocol that consists of intensive immunosuppression using high-dose chemotherapy (cyclophosphamide) followed by autologous peripheral blood stem cell rescue. Although a significant minority of patients experienced durable complete remissions, further long-term follow-up is needed to assess the general utility and risk/benefit ratio for autologous transplantation in patients with ITP. Lymphedema Lymphedema is an accumulation of lymphatic fluid in interstitial tissue that causes swelling, most often in the arm(s) and/or leg(s), and occasionally in other parts of the body. Lymphedema can develop when lymphatic vessels are missing or impaired (primary or congenital), or when lymph vessels are damaged or lymph nodes removed (secondary). When the impairment becomes so great that the lymphatic fluid exceeds the lymphatic transport capacity, an abnormal amount of protein-rich fluid collects in the tissues of affected areas. Left untreated, this stagnant, protein-rich fluid not only causes tissue channels to increase in size and number, but also reduces oxygen availability in the transport system, interferes with wound healing, and provides a culture medium for bacteria that can result in lymphangitis (infection). The incidence of primary lymphedema has been estimated to be between 1 in 6,000 and 1 in 300 live births, so it may be a rare disease, or it may be a more common disease that predisposes to the secondary type and is under-recognized. NHLBI investigator-initiated projects are seeking to identify the developmental, molecular, and cellular defects that contribute to lymphedema and are seeking to design effective therapeutic interventions to treat both primary and secondary lymphedemas. Myelodysplasia Myelodysplasia or myelodysplastic syndrome (MDS) is a group of disorders in which the bone marrow overproduces cells that do not mature normally, due in part to an autoimmune suppression of blood cell production and in part to an intrinsic defect in blood cell production. Most patients with MDS are anemic and many have low platelet counts and low numbers of infection-fighting white blood cells (neutrophils). The only curative therapy is allogeneic bone marrow transplantation. The standard treatment for MDS is supportive care, i.e., transfusions and antibiotics as needed. MDS commonly affects older adults. More than 20,000 new cases of MDS are diagnosed per year in the United States and its incidence is increasing. About half of MDS patients die from the consequences of marrow failure, and half die following transformation to a refractory acute leukemia. NHLBI's intramural Hematology Branch is exploring two treatment approaches for MDS. The first involves immunosuppressive treatment to improve bone marrow function and reverse transfusion dependence. Patients receive two immunosuppressive agents, antithymocyte globulin (ATG) and cyclosporine, and are monitored for transfusion requirements. In the second approach, selected MDS patients up to age 75 are entered into allogeneic stem cell transplant protocols to evaluate curative approaches. The International Aplastic Anemia and Myelodysplasia Foundation has collaborated with NHLBI to recruit patients. Renal Cell Carcinoma (RCC) Metastatic RCC is an uncontrolled growth of renal cells, the cells that normally exist in the kidney. These cancerous cells can spread (metastasize) from the original kidney tumor site to other organs such as the bones, lymph nodes, liver, lungs, and brain. Once these organs become involved, the uncontrolled growth of cells can lead to organ failure and death. While there are several treatments available for RCC that can be successful, RCC is rarely curable once it has spread to other organs. Surgery can be used to treat RCC, but in many patients the disease has spread too much to be removed by surgery. Likewise, chemotherapy can be used to treat RCC, but it has been relatively unsuccessful for patients whose cancer has spread to other organs. Bone marrow transplants (BMTs) have been used to treat cancers of the blood and bone marrow. BMTs are usually combined with powerful doses of chemotherapy and radiation therapy. These additional treatments are associated with toxic side-effects, often making BMTs too dangerous to attempt in many patients. The effectiveness of BMT on solid tumors like RCC has not been well-evaluated. NHLBI's intramural Hematology Branch is interested in learning more about the potential benefits of modified BMT (allogeneic stem cell transplantation) for patients with advanced RCC. In a current study, the Branch is treating advanced RCC patients with transplanted stem cells from a genetically matched brother or sister. After the stem cells are transplanted, they help to make new blood cells. In addition, immune factors found in the transplant can work to destroy cancerous cells. In order to avoid the toxic side-effects normally associated with BMT, the stem cell transplant is combined with low- intensity chemotherapy. The majority of the cancer-killing effect will be the responsibility of the stem cell transplant rather than the chemotherapy. Sickle Cell Disease (SCD) SCD is an inherited disorder that is most common among people whose ancestors come from Africa, the Middle East, the Mediterranean basin, and India. In the United States, SCD affects primarily African Americans, about 72,000 of whom have SCD. As such, SCD is the most common genetic blood disorder in the United States, affecting approximately 1 in 500 African American newborns and 1 in 1,000 Hispanic newborns each year. SCD occurs when an infant inherits the gene for sickle hemoglobin from both parents (sickle cell anemia [SCA]) or the gene for sickle hemoglobin from one parent and the gene for another abnormal hemoglobin from the other parent (SCD types Hb SC, Hb S-Beta thalassemia, etc.) One in 12 blacks carries the sickle cell trait (Hb AS). In SCD patients, the hemoglobin molecules in the red blood cells that carry oxygen throughout the body tend to damage the red cell walls, causing them to stick to blood vessel walls. This leads to sickle cell crises, the painful episodes considered the hallmark of the disease. Chronic end-organ damage occurs to the brain, lungs, kidneys, spleen, and liver and leads to premature death, with death for severely affected individuals occurring between 42 and 48 years. The current NHLBI SCD research portfolio includes projects to:
Research published in the past year confirmed that adhesive interactions between individual blood components and between blood components and cells that line blood vessels (endothelium) are likely to be important initiators of sickle cell vaso-occlusive crises. The sticky, stiff, sickle red blood cells provoke inflammation as they obstruct blood flow. Investigators have been able to induce inflammatory responses in sickle mice but not normal mice by removing and then providing oxygen. This was correlated in the sickle mice with oxidant production by vascular endothelial cells and could be completely prevented by prior infusion into mice of an antibody directed toward the P-selectin molecule expressed on vascular endothelium. These reports have set the stage for development of human therapies, e.g., monoclonal antibodies, designed to interfere with specific adhesion molecules such as P-selectin in order to decrease leukocyte-endothelial cell interactions. Systemic Lupus Erythematosus (SLE) SLE (or lupus) is an autoimmune disorder in which the body produces antibodies that harm its own cells and tissues. Typical symptoms of SLE are fatigue, arthritis, fever, skin rashes, and kidney problems. SLE affects more women than men. Patients with SLE have a higher incidence of thrombosis and spontaneous loss of pregnancy. Its cause is unknown and there is no known cure, but the symptoms can be controlled with appropriate treatment and most patients can lead an active life. Recent NHLBI-supported studies have found that some lupus antibodies have catalytic properties and can specifically convert prothrombin to thrombin, thereby creating a hypercoagulable condition that may explain the high incidence of thrombosis in patients with SLE. Thrombotic Thrombocytopenic Purpura (TTP) TTP is a potentially fatal disease characterized by low blood platelet levels and widespread platelet thrombi in arterioles and capillaries. Relapse is not uncommon in those who survive the acute phase. Both endothelial cell damage and intravascular platelet aggregation have been suggested in its pathogenesis. Microscopic examination of the thrombi has revealed an abundance of the plasma protein von Willebrand factor (vWf). Despite advances in basic sciences, treatment options and mortality associated with TTP remain unacceptable. NHLBI supports studies on the biology of platelet function, mechanisms of blood coagulation, and the interaction of blood with the vascular surface. An interaction between vWf and the platelet surface glycoprotein complex I (GP I) is believed to be essential for the formation of a thrombus. vWf is synthesized as large polymers and is then cleaved into smaller units by a plasma protease. The presence of inhibitory antibodies to the protease was confirmed in some patients with TTP. Inhibition of the protease results in large amounts of vWf in plasma that can spontaneously aggregate platelets. Understanding the biosynthesis and processing of vWf may offer an opportunity to develop new treatments for TTP. Rare Diseases Research Initiatives Ongoing Initiatives
Initiatives Started in FY 2000 Cellular and Molecular Mechanisms of PPH A renewal of a PA encourages efforts to continue important research in PPH with the emphasis on a mechanistic understanding of the disease. Further studies are encouraged that address, at the cellular and molecular level, mechanisms involved in pulmonary vascular remodeling, pulmonary vascular tone, and the genetic basis of PPH. Priority will be given to research to identify novel genes or vasoactive mediators important in PPH pathology and determine their functional effects on pulmonary vascular cells, on extracellular matrix, and on pulmonary vascular tone. Further, research integrating the relationship between mediators of vasoconstriction and pulmonary vascular remodeling is strongly encouraged. The ultimate goal is to develop new and effective therapies. Programs of Excellence in Gene Therapy (PEGT) A new RFA establishes up to five multidisciplinary, collaborative research environments that promote rapid translation of basic, preclinical studies of gene therapy for cardiovascular, pulmonary, and/or hematologic diseases into human pilot experiments. The 5-year awards, using the U01 cooperative agreement grant mechanism, will provide shared access to specialized services such as preclinical toxicology testing, generation of vectors for preclinical and clinical use, large-scale production of biological reagents (e.g., cytokines), and biostatistical support. In addition, the programs will provide training to NHLBI-supported physician-scientists in translational (basic science to clinical application) research for gene therapy. Each program will have a minimum of two clinical projects under way at any one time and four to six training positions. One PEGT will serve as the Coordinating Center and Data Core. A one-time competitive renewal for the existing awardees may be awarded for an additional 5 years. SCORs in Hematopoietic Stem Cell Biology A renewal of an RFA extends for a second 5-year period the SCOR program to advance knowledge of basic stem cell biology in areas of stem cell isolation, quantitation by in vivo assay, in vitro and in vivo growth and expansion, gene insertion and long-term expression, and engraftment. This basic knowledge will be applied clinically to develop hematopoietic stem cell therapy that cures both genetic and acquired diseases and to perform successful gene therapy using the hematopoietic stem cell as the target for gene transfection and for lifelong expression of normal genes. The SCOR mechanism is uniquely designed to support a spectrum of multidisciplinary basic and clinical research in a synergistic fashion such that major therapeutic advances will be realized in the next decade in both gene therapy and stem cell transplantation. Initiatives Planned for the Future Blood and Marrow Transplant Clinical Research Network A new RFA organizes a network in FY 2001 to accelerate research on management of hematopoietic stem cell transplantation, standardize existing treatments, and evaluate new treatments. The network of 16 to 20 clinical centers and a data-coordinating center would provide a coordinated, flexible mechanism to accept ideas and build consensus from the transplant community; develop protocols; expeditiously perform multi-center phase II and phase III clinical trials; provide information to physicians, scientists, and the public; and improve stem cell transplantation therapy for diseases such as leukemia, SCD, thalassemia, and FA. Genetic Modifiers of Single-Gene Defect Diseases A new RFA encourages investigators in FY 2001 to identify and characterize the genes responsible for modifying the clinical progression and outcome of heart, lung, and blood diseases due to single-gene defects. Examples of such single-gene defect diseases are CF, SCD, hemophilia, AAT deficiency, glucocorticoid remediable aldosteronism (GRA), Liddle syndrome, and cardiac myopathies, dysplasias, and arrhythmias that result in sudden cardiac death. The modifier genes are likely to encode a wide variety of proteins that either interact directly with the disease gene, influence pathways involving the disease gene, or affect metabolic processes altered as a result of the disease gene defect. Identification of the genes responsible for these differences should lead to a better understanding of disease pathogenesis, early diagnosis, and improved treatment. Pathogenesis and Treatment of Lymphedema A new PA encourages efforts in FY 2001 to investigate the pathogenesis of, and new treatments for, primary and secondary lymphedema, the swelling of subcutaneous tissues caused by a breakdown in the regulation of lymphatic drainage. Lymphedema results from fluid accumulation and may arise congenitally or from surgery, radiation, or the presence of a tumor in the area of the lymph nodes. This trans-NIH program announcement seeks to stimulate research on the biology of the lymphatic system; to characterize at the molecular, cellular, tissue, organ, and intact organism levels and the pathophysiologic mechanisms that cause the disease; and to discover new therapeutic interventions. Such knowledge will help to improve early diagnosis of affected individuals, the choice and timing of treatment, and genetic counseling. Pediatric Heart Disease Clinical Research Network A new RFA establishes in FY 2001 a network of interactive pediatric clinical research centers to promote efficient evaluation of new treatment methods and management strategies that may benefit children with structural congenital heart disease, inflammatory heart disease, heart muscle disease, and arrhythmias. Therapeutic trials and studies may involve investigational drugs, drugs already approved but not currently used, devices, interventional procedures, and surgical techniques. The network approach, consisting of five to six clinical centers and a data-coordinating center, is an effective, flexible way to study adequate numbers of patients with rare diseases such as congenital cardiovascular malformations. Efficiencies will be achieved through a common infrastructure for recruiting, monitoring, and following patients whose conditions will be characterized in a standard fashion. Approximately 2,000 patients are expected to participate in 6 to 12 different protocols over the 5-year project period. The network will also serve as a platform to train junior investigators in pediatric clinical research and as a vehicle for rapid and widespread dissemination of findings. Comprehensive Sickle Cell Centers A renewal of an RFA in FY 2003 to operate a nationwide network of collaborative comprehensive centers in basic and translational research focused on the development of cures or significantly improved treatments for SCD. The network of 10 centers and a statistics and data management core will carry out basic research, inter-center collaborative clinical research, and local clinical research focused on the most promising biomedical and behavioral therapeutic modalities. The centers will also support career development of young investigators in SCD research and will support services such as patient education and counseling, community outreach, and hemoglobin diagnosis. This is the eighth re-competition of a program established by a presidential initiative and congressional mandate in 1972. Rare Diseases Program Activities AAT Deficiency A June 2000 conference on "Alpha-1 Antitrypsin Deficiency and Other Conformational Diseases," organized by the Alpha One Foundation and co-sponsored by NHLBI and NIDDK, enabled researchers on these related diseases to exchange scientific information. BPD A "Workshop on Bronchopulmonary Dysplasia" was organized by NICHD, NHLBI, and ORD to review the definition of BPD and lung injury in very preterm infants, identify gaps in knowledge of lung development, select the best indicators of outcome for infants with BPD, and prioritize areas for future research. A report of the meeting will appear in the Spring 2001 issue of the Journal of Respiratory and Critical Care Medicine . Churg-Strauss Syndrome NHLBI, NIAID, and ORD co-sponsored a September 2000 workshop on "The Relationship of Asthma Therapy and Churg-Strauss Syndrome." More than 20 scientists with expertise in immunology, pharmacotherapy, epidemiology, allergy, asthma pathogenesis and management, vasculitic and eosinophilic diseases, and asthma clinical research met to explore the nature and magnitude of the association between anti-leukotriene therapy and Churg-Strauss syndrome and to identify possible mechanisms. The workshop participants made recommendations for future research directions to shed light on the pathogenesis of asthma and eosinophilic syndromes. Publication of the workshop summary is expected in 2001. Cooley's Anemia A "Working Group on Stem Cell Plasticity" met in March 2000 and developed RFA-HL-01-007, Hematopoietic Stem Cell Plasticity, issued in November 2000. FA NHLBI's Hematology Branch participated in the fiSymposium on Fanconi Anemiafl at the Annual Scientific Meeting of the International Society for Experimental Hematology in Tampa, Florida; and in the Annual International Fanconi Anemia Scientific Symposium in Amsterdam, The Netherlands. GvHD A "Forum on Allogeneic Unrelated Cord Blood Banking and Transplantation," co-sponsored by FDA, met in August 2000. Leaders in cord blood banking and transplantation from around the world discussed requirements for collecting, processing, storing, and transplanting unrelated allogeneic umbilical cord blood. The recommended practices included infectious disease screening and testing, determining the number of viable cells post-processing, collecting donor family histories, and maintaining a sample attached to the frozen cord blood unit for follow-up testing. Transplant outcome data suggested that human leukocyte antigen- (HLA-) mismatched transplants result in less GvHD than expected and that larger cell doses tend to result in better engraftment. LAM NHLBI and the LAM Foundation co-sponsored the "International LAM Symposium" held at Columbia University in November 1999. Lymphedema A May 2000 meeting on "Conquering Lymphatic Disease: Setting the Research Agenda," co-sponsored with the Lymphatic Research Foundation, ORD, and four other NIH Institutes, resulted in PA-01-035, Pathogenesis and Treatment of Lymphedema, released in December 2000. PPH NHLBI and the Pulmonary Hypertension Association (PHA) have agreed to joint sponsorship of a program to train clinicians to perform biomedical research related to pulmonary hypertension. The training will be supported by the Mentored Clinical Scientist Development Award (K08) mechanism. SCD At the September 2000 "Workshop on Nitric Oxide as a Potential Therapeutic Agent for Sickle Cell Disease and Other Vascular Diseases," a discussion was held on the promise of NO as a possible therapy for SCD-associated acute chest syndrome, respiratory distress in premature infants, and other severe vascular problems. Pilot data in animals and humans were presented that suggest that NO provides a promising therapeutic option for these complex clinical problems. A September 2000 "Workshop on Central Nervous System Disease in Children with Sickle Cell Disease" was held at NHLBI to discuss current understanding of the effects of SCD on the central nervous system (CNS), contemporary methods of evaluation of the CNS, prophylactic and therapeutic interventions that may alleviate brain damage, and future directions for research. Workshop participants discussed the age that screening for CNS disease should begin; studies needed for screening for CNS disease; the role of continuing blood transfusions versus hydroxyurea in secondary stroke prevention as patients age; the use of anti-platelet drugs and anti-inflammatory drugs as possible therapeutic options for clinical trial testing in stroke prevention; identification by HLA typing and other risk modifiers of subjects who may be at risk for SCD; establishment of a registry of stroke patients; and establishment of a clinical network to plan various protocols for future studies. After 20 years and more than 40 publications, the Cooperative Study of Sickle Cell Disease has ended. In September 2000, the investigators met to discuss manuscripts still to be written based on the database and the stored genetic and sera samples. At the STOP Trial Steering Committee Meeting in September 2000, the STOP investigators met to discuss the STOP II Trial protocol to be submitted for review by the Data and Safety Monitoring Board. The STOP II Trial will attempt to ascertain if it is safe to stop transfusing children for stroke prevention after 30 months. At the MSH Patients' Follow-up Steering Committee Meeting in September 2000, the investigators met to discuss follow-up of the study cohort for the next 5 years. A paper summarizing survival over the past 8 years is planned. Data from the study suggest that survival is improved if fetal hemoglobin levels are elevated by continuing hydroxyurea therapy. At the first BABY HUG Steering Committee Meeting in September 2000, investigators discussed plans for protocol development and recruitment. The objective of the clinical trial is to determine if hydroxyurea therapy is effective in preventing chronic end-organ damage in young pediatric patients with SCA. The clinical trial will involve pediatric clinical centers with expertise in treating SCA and a medical coordinating center to supervise drug distribution, central laboratory functions, and data collection. TTP At a July 2000 "Workshop on von Willebrand factor and Thrombotic Thrombocytopenic Purpura," TTP investigators gained a clearer understanding of worldwide efforts to address the disorder and laid the groundwork to develop new collaborations. A summary of the workshop is planned for publication. Problem Areas Related to Rare Diseases AAT Deficiency Treatment options for patients with AAT deficiency are limited. Only one product has been approved by FDA, and its approval was based on increased levels of AAT in the blood without evidence of clinical benefit. New products are in various phases of evaluation and there is much debate about whether a clinical trial is needed to assess the clinical efficacy of these new products before they are approved. AA and PNH The viral agent in post-hepatitis AA, which is probably the same agent that is responsible for seronegative acute hepatitis and fulminant hepatitis of childhood, needs to be identified using samples of blood, liver, and stool from patients with acute hepatitis. Better immunosuppressive treatment of AA requires large clinical trials, and patients must be recruited to specified research centers rather than treated haphazardly in private practice. To elucidate the relationship between an autoimmune disease (AA) and clonal expansion of mutated cells (PNH), large numbers of patients must be available for study. ARVD A concerted multi-laboratory program combining basic, clinical, and genetic approaches is needed to identify the causes of this highly lethal form of cardiomyopathy so that a rational search for therapies can begin. Additional clinical centers, and perhaps a national registry, would be useful to investigators who are already studying its origins and potential treatments. CJD Standardized reference materials to validate assay systems to detect TSEs such as CJD are urgently needed. In April 1999, the WHO recommended the establishment of international reference materials for TSE diagnosis. Standards proposed would include human brain tissue, human blood, animal tissues, and animal blood. These materials would be used to calibrate the in-house reference materials of individual laboratories to the same single, international standard. The need for blind panel validation of all assaysSi.e., the validation of the sensitivity, reproducibility, and predictive abilities of any given candidate assaySis emphasized. Without standardized reference materials, it is not possible to evaluate the relative merits of any assay developed or even to know for sure whether they are more sensitive than existing Western blots or ELISAs. FA The eight distinct complementation groups represent a high degree of locus heterogeneity, which complicates molecular diagnosis of FA and may make screening cumbersome. However, certain complementation groups prevail in specific populations (FA-C in Ashkenazi Jews, FA-A in Afrikaansspeaking people and Italians), which helps to set priorities for mutation screens. The FA-A and FA-C proteins have no sequence homologs in the current databases, although structural homologs may exist. Thus, resolution of difficulties in FA protein purification and pursuit of the X-ray crystallographic structure of FA proteins is considered a high priority. The function of FA proteins and the nature of their interaction with other proteins in the Fanconi Protein Complex as well as their relation to DNA repair are areas of current study. GvHD The nature of the responding cells in GvHD and reliable methods to predict and ameliorate the problem remain elusive. A challenge remains in fostering graft-versus-leukemia or graft-versus-tumor effect while avoiding GvHD. In addition, the basic immunology, biology, and tissue specificities of the response require further definition. Infectious Myocarditis A non-invasive test for infectious myocarditis having appropriate sensitivity and specificity is needed. At present, the endomyocardial biopsy, which is invasive and has limited specificity and sensitivity, is the gold standard for diagnosis. LAM Scarcity of data and LAM tissue has hindered learning about the etiology and pathogenesis of LAM. The small number of patients makes it difficult to learn about important aspects of the disease such as its prevalence, prognosis, and clinical course, or the effects of various treatments. A lack of animal models makes it necessary to obtain human cells or tissue to do LAM research. The registry will facilitate collection of clinical data and tissue and will identify a cohort of LAM patients who might be contacted in the future if opportunities for clinical studies arise. The LAM Foundation continues to facilitate collection of LAM tissue at the time of lung transplantation. Progress in LAM research has increased demand for this scarce resource. A NHLBI LAM Tissue committee is establishing procedures and guidelines for LAM tissue collection and distribution. LQTS Access and identification of sufficient numbers of new patients for studies remain a constant problem. Identification of mutant gene carriers would be greatly facilitated by accurate means of screening individuals in afflicted families for specific founder mutations. Improved means of identifying new mutations in the various genes involved would also be helpful. Investigators are working to increase the visibility of the registry in the African American medical community. It is not known whether this disease is less common in this group or whether African Americans are referred to the registry with less frequency than the Caucasian population. Lymphedema As with other rare disease, the main problem is how to interest biotechnology and pharmaceutical companies in undertaking research to find the genetic bases of the disorder and develop treatments, given that the potential profits are small. |
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