A study of risk factors for the development of FVIII inhibitors in Indian severe haemophilia A patients

Abstract

Background: Development of 'FVIII Inhibitors' or alloantibodies to Factor VIII in patients with congenital haemophilia A is a serious complication of FVIII replacement therapy. It prevents the efficient clinical management of these patients, particularly those with severe haemophilia A, and leads to a substantial increase in mortality, as well as in the frequency and cost of management of bleeds among these patients, especially post-operatively. Inhibitor development in haemophilia A patients is thought to be complex and influenced by various genetic and non-genetic risk factors. Associations with various risk factors have been suggested in different populations. In earlier studies in Indian haemophilia A patients, IL10 haplotypes and TNFA rs1799724 promoter polymorphisms have been found to be significantly associated with inhibitor development, while four exonic nonsynonymous FVIII SNPs, G1679A [R484H], A2554G [R776G], C3951G [D1241E], and A6940G [M2238V], whose haplotypes encode six wild-type FVIII proteins (H1 - H6) have not been found significant. Aim: The aim of this study was to analyse the association of other genetic (HLA) and non-genetic (treatment-related) risk factors with inhibitor development in Indian severe haemophilia A patients. Methods: One Hundred Indian severe hemophilia A patients, (40 consecutive inhibitor positive patients and 20 concordant/discordant family members, as well as 40 consecutive inhibitor negative control patients (over 10 years of age with > 10 exposures to treatment products) were included in the study after their informed consent. The study was approved by the Institutional Ethics Committee for Research on Human Subjects of the National Institute of Immunohaematology (ICMR), Mumbai. A clinical proforma was designed to record patient details. HLA- DRB1 and DQB1 alleles were genotyped by PCR with Sequence Specific Primers (SSP), using the AllSet+TM Gold SSP HLA-DQ and HLA-DR Low Resolution kits (Invitrogen, USA). The results were analysed for statistical significance by Fisher's exact test. Results: The mean age of the inhibitor positive patients was 24.57 (6- 55 years) and mean lifetime exposures to treatment products was 19.22 (4-43); and the mean age of the inhibitor negative patients was 28.30 (12-65 years) with 43.625 (15-220) mean lifetime exposures. Among the inhibitor positive patients, 31/40 (77.5%) patients were high-responders (> 5 BU/ml). The HLA-DRB1∗13 allele (P: 0.048) and the HLA-DQB1∗05/∗06 (P: 0.025) genotype were found to be significantly higher in the inhibitor positive samples as compared to the controls, in the samples studied so far. Treatment-related risk factors such as type of treatment product and exposure to treatment products before the first year of life (22.5% inhibitor positive patients vs. 12.5% inhibitor negative patients) were not significantly different. Conclusion: The association of these factors with other risk factors such as FVIII mutations also, could provide useful insights into the FVIII immune response, and possibly influence timely prediction, prevention and treatment of FVIII inhibitors.