CHS Research Grants for 2009
The role of X-inactivation in the expression of hemophilia A in women
Dr. Wenda L. Greer, FCCMG
Professor, Department of Pathology
Dalhousie University - Halifax, Nova Scotia
Second year funding
Co-investigators: Dr. Sue Robinson, Dr. Sarah Dyack
Hemophilia A (HA) is an X-linked bleeding disorder resulting from mutations in the F8 gene. One functional F8 gene is sufficient for normal clotting. Thus, typically XY males who interit one mutated F8 gene are affected while heterozygous XX females are not. Rarely, heterozygous females with HA have been described. These can arise due to unfavourably skewed X chromosome inactivation (XCI). This is a dosage compensation mechanism that causes one X in every female cell to be inactivated early in development. In most females, approximately half of their cells inactivate their maternal and half their paternal X. In rare cases, XCI is skewed. If it is skewed toward the activation of a mutated gene, a heterozygous female can be affected. A family has presented with several males and several females affected with HA. In the females, most cells were expressing the mutated paternal X chromosome. It is unlikely that chance could account for the dramatic skewing of XCI leading to 3 affected females.
Our objective is to understand why these females are expressing HA. Our hypothesis is that is is due to skewed XCIR resulting from an inherited predisposition for the mutated X-chromosome to remain active. Our aims are to:
- determine XCI patterns and correlate these with disease expression
- determine whether XCIR skewing is more consistent with genetically influenced or random XCI.
- delineate, through microsatellite analysis, a region of the X-chromosome that is associated with varied susceptibility of XCI
- consider potential candidate genes from this region.
- identify the clinical symptoms and standards of care of carrier females, and their experiences with medical treatment by interviewing carrier females and healthcare professionals.
We believe that this family provides a unique opportunity to study XCI and its role in the expression of HA in heterozygous females. It also provides an opportunity to document the clinical phenotype of female carriers who differ in their factor VIII activities according to their respective XCIR.This project was extended until August 31, 2011.
An evaluation of the prevalence and functional significance of non-neutralizing antibodies to factor VIII
Dr. David Lillicrap
Department of Pathology and Molecular Medicine
Queen’s University – Kingston, Ontario
Second year funding
Co-investigators: Dr. Jerome Teitel, Dr. Georges-Étienne Rivard, Dr. Irwin Walker
Funded through an unrestricted research grant to the Canadian Hemophilia Society from Bayer HealthCare
The development of antibodies to factor VIII (FVIII) represents the main treatment-related complication of current therapies for hemophilia A. For the past 30 years, this complication has been evaluated by a laboratory test that detects only those antibodies that interfere with FVIII’s clotting function. There is growing evidence to suggest that in addition to antibodies that inhibit the functional activity of FVIII, some “non-neutralizing” antibodies are also generated by FVIII exposure. The prevalence of these antibodies, their overlap with neutralizing inhibitors and their clinical significance are all factors that are very poorly characterized and form the basis for the studies proposed in this research project. In this project, we will establish a laboratory test to detect and quantify the levels of antibodies that bind to FVIII in plasma. The test plasma samples have already been characterized with a functional antibody test (the Bethesda assay) and thus overlapping patterns of reactivity will be apparent. Finally, when detected, we will attempt to correlate the presence of non-neutralizing antibodies with in vivo FVIII recovery and half-life.
Phenotypic Characterization of Three Candidate Type 2B von Willebrand Disease Missense Mutants
Dr. Maha Othman
Adjunct Assistant Professor, Department of Pathology and Molecular Medicine
Queen’s University - Kingston, Ontario
One year funding
Co-investigator: Dr. David Lillicrap
Type 2B von Willerband disease (VWD) is a unique bleeding disorder among all types of VWD where there is an enhanced interaction between blood platelets and the VWF protein. The disease is known to result from mutations in certain area of the VWF gene producing an abnormally adhesive VWF protein leading to excessive mucocutaneous bleeding. Not all patients with type 2B VWD show similar clinical picture and/or labaoratory features. In addition, some of the confirmatory laboratory testing are not available in all laboratories or are poorly applied. This infuences the diagnostic certainity of the disease with an implication on treatment decisions. A conclusive evidence towards the clinical diagnosis can be provided by identification of the genetic mutations responsible for the disease and to functionally study these mutations to prove its link to the clinical/ laboratory picture. In this project we aim to study three novel candidate mutations that we have identified in patients with type 2B VWD through the Canadian PT-VWD project. This study will prove whether or not these mutations are responsible for the clinical and laboratory features observed in these patients and will validate the treatment decsisions.
Use of amphipathic helical peptides coupled to nanofibrous microspheres to control hemorrhagic external bleeding in hemophiliacs
Dr. Mark Blostein
Lady Davis Institute for Medical Research
McGill University – Montreal, Quebec
First year funding
Co-investigator: Dr. Jake Baralet
The hereditary hemophilias are the most common inherited severe bleeding disorders and are characterized by lifelong bleeding, both spontaneous, internal bleeding as well external bleeding due to injury, most commonly from surgical procedures. The current research grant proposes to develop a new biocompatible matrix employing nanotechnology that is hemostatic by incorporating a peptide that accelerates blood coagulation and will therefore stop bleeding. This peptide was discovered in my laboratory and reduces bleeding in animal models of hemorrhage. Therefore, attaching this peptide to „nanotechnology‟ based materials has great promise as a novel agent to reduce bleeding from external hemorrhagic injuries. The methodology will include utilizing standard biochemical techniques to characterize the material followed by the testing of the biocompatible material in animal models. The development of this product is especially relevant to the goals of the Canadian Hemophilia Society by discovering new materials to control external bleeding in hemophiliacs particularly after surgical procedures.
Risk of Ischemic Heart Disease in Hemophilia: Evaluating Endothelial Function and the Development of Atherosclerotic Vascular Disease in Hemophilia
Dr. Shannon Jackson
Department of Medicine and Hematology
University of Calgary – Calgary, Alberta
One year funding
Co-investigators: Dr. Man Chiu Poon, Dr. Robert Card
The deposition of cholesterol and inflammatory cells within arteries is termed atherosclerosis and is the leading cause of death in Canada. The endothelium is a protective surface on the arteries that if disturbed can increase the risk of developing atherosclerosis and its complications including heart attacks and strokes. Early studies suggest that haemophiliacs are less likely to die from heart attacks and strokes than the average person. However, that has not been proven and research is needed to find out. In this study, function of endothelium will be tested with a specialized ultrasound and finger probe. Abnormal function of the endothelium is felt to represent early disease of the arteries which may develop into atherosclerosis and cause heart attack or stroke. In this study, an interview will be completed to collect information on general medical history, risk factors for heart disease and stroke, hemophilia history, dietary and activity habits, quality of life, and family history. A physical examination will be performed and fasting laboratory testing completed (including collection of blood for storage so that in the future we can examine the DNA for genetic factors that may affect endothelial function and/or the development of heart disease). Finally, each subject will be followed for 5 or more years to see what the rate of developing heart disease and strokes is. This and the above data will be compared to a control group of male firefighters who have participated in a study called Firefighters and Their Endothelium (FATE). This study will start in Calgary with approximately 30 subjects with hemophilia and eventually be expanded to at least one other hemophilia centre in Canada and include a total of approximately 100 subjects with hemophilia.
Use of Ports in Canadian Hemophilia Prophylaxis Study (CHPS)
Lab work studentship
Ms. Samatha Chait
University of Western Ontario
Under the supervision of Dr. Brian Feldman
Hospital for Sick Children in Toronto
Summer 2009 funding
Funded through a research grant to the Canadian Hemophilia Society from Bayer Health Care
Preventative treatment with blood clotting factor for severe hemophilia A is likely to be more effective than treatment given only when joint bleeding occurs. However, preventative treatment is very expensive. For the past 11 years we have been studying 55 boys on an ongoing basis to determine whether preventative treatment using a “tailored” approach can help prevent some of the problems associated with hemophilia, while at the same time minimizing frequency and cost of treatment. At the beginning of the study, patients are given weekly treatments of clotting factor. If an unacceptable amount of bleeding occurs, the frequency of factor infusions is increased to twice a week. If unacceptable bleeding continues, infusions are increased to alternate day frequency. In order to determine how well the patients are doing, we are recording the number of joint bleeds, number of joints with recurrent bleeding, as well as physiotherapy assessments. In addition, we are collecting data on the cost of tailored prophylaxis. We are also following the use of ports in patients, as our experience with ports in this study is noticeably better than that in the published literature. Enrollment onto the study is now closed, with continuing follow-up of those enrolled. The cohort will be followed for an additional 5 years.