Mutation profile of hemophilia a patients with inhibitors and association of interleukin and cytokine gene polymorphisms with inhibitor development

Abstract

Hemophilia A (HA) is an X linked recessive bleeding disorder characterized by qualitative and quantitative deficiency in the factor VIII (FVIII) protein, mainly caused by Factor 8 (F8) gene mutations. A severe complication in the replacement therapy of HA patients is the development of allo-antibodies (inhibitors) against FVIII which neutralize the substituted FVIII. Genetic risk factors along with F8 gene mutations influence the development of inhibitors. Interleukins and cytokines such as IL4, IL5, IL10, TGFB1 and IFNG that are involved in the regulation of B lymphocyte development are possible targets as other genetic risk factors. The aim of this dissertation was to reveal the F8 gene mutation profile of severe HA patients who developed inhibitors using various methods to assess the possible associations between 9 selected interleukin and cytokine gene polymorphisms with inhibitor development in HA patients with a null mutation in the F8 gene. The most prevalent mutation in inhibitor patients was intron 22 inversion followed by nonsense mutations and large deletions with major effects on FVIII function. Therefore, severe HA patients were screened for intron 22 inversion to constitute inhibitor (+) and inhibitor (–) patient subgroups to carry out a case-control association study. A significant association with the T-allele of rs2069812 located in IL5 gene promoter and patients with inhibitors was found with a p-value of 0.0251. The TT genotype was also significantly associated with the inhibitor (+) patient group with a p-value of 0.0082 and OR of about 7, suggesting that the T-allele as the recessive susceptibility allele and C-allele was the dominant protective allele. The present findings are highly informative about the role played by the polymorphisms in genes involved in B lymphocyte development as genetic risk factors in antibody development in severe HA patients with null mutations and paves the way for furthe studies in the field.