The association of HLA-DRB1 and HLA-DQB1 alleles with the development of factor VIII inhibitors in severe haemophilia A patients in India

HLA-DRB1*01:01, but not HLA-DRB1:1503 or HLA-DRB1*11, is associated with decreased inhibitor risk in Iranian hemophilia A patients

BACKGROUND/OBJECTIVE

Hemophilia A is a genetic disorder through which patients suffer from recurrent bleeding. This can be caused by a defect in human plasma coagulation factor VIII. High incidence of FVIII inhibitors in some severe hemophilia A patients after FVIII therapy is a considerable complication. Determination of good predictive factors can improve the safety of this treatment. HLA-II have been shown as a predictive element for inhibitor development. The goal of this study is to determine the association between HLA-DRB1*15:03, HLA-DRB1*11 and HLA-DRB1*01:01 alleles and FVIII inhibitors in severe hemophilia A patients in Iran.

MATERIALS/METHODS

HLA-DRB1 genotyping was performed using Multiplex sequences Specific Primers (PCR-SSP) in two groups of severe hemophilia A patients comprising 51 and 50 individuals with and without FVIII inhibitors respectively. The levels of inhibitor were determined through Nijmegen-modified Bethesda assay. HLA-DRB1 allele frequencies were compared between groups by using multiple logistic regression models.

RESULTS

HLA-DRB1*01:01 allele frequency was significantly higher in patients without inhibitor OR_adj: 2.7 (95%CI: 1.08, 6.97; P = 0.034). There wasn't any statistically significant difference in HLA-DRB1*11 allele frequency between groups OR_adj: 0.7 (95%CI: 0.27, 1.82; P = 0.47). There was no connection between HLA-DRB1*15:03 and inhibitor development OR_adj: 0.94 (95%CI: 0.38, 2.35; P = 0.94).

CONCLUSION

An association between HLA-DRB1*01:01 and paucity of FVIII inhibitor showed that this allele has probably a protective effect in severe hemophilia A patients in Iran. Determination of the predictive and protective alleles are beneficial in pre-treatment activities and decrease the risk of unsuccessful therapy with FVIII in each population.

Prevalence of FVIII inhibitors in severe haemophilia A patients: Effect of treatment and genetic factors in an Indian population

INTRODUCTION

Factor replacement therapy in treatment of haemophilia A is complicated by the production of neutralising antibodies known as inhibitors. The formation of inhibitors is multifactorial being associated with both genetic and environmental factors.

AIM

To document the prevalence of inhibitors in severe haemophilia in the community where most patients receive only infrequent episodic replacement therapy and evaluate the factors which could be contributing to it.

METHODS

Community based camps were conducted in different parts of the country. Patients were assessed through a structured questionnaire and blood samples were obtained for laboratory evaluation of inhibitors and defined immunological parameters.

RESULTS

Inhibitors were present in 87/447 (19.5%) of the evaluated patients. High-titre inhibitor (>5 Bethesda Units [BU]) was identified in 31 (35.6%) patients. HLA DRB1-13-positive cases (RR = 2.04; 95% CI 1.06-3.911; P = 0.033) had an increased risk of inhibitor formation which was retained in the high-titre subset. A decreased risk of inhibitor formation was noted with heterozygous IL4-590 C/T allele (RR = 0.22; 95% CI 0.108-0.442: P = 0.000). There were no significant correlations between any of the evaluated environmental factors and the development of inhibitors in this study.

CONCLUSION

The overall prevalence of inhibitors in patients with severe haemophilia A is similar to that reported among patients receiving regular replacement therapy. The data from this study, limited by its retrospective and cross-sectional study design, would suggest that genetic rather than environmental are more likely to impact the development of inhibitors.

Comparative profiling of HLA-DR and HLA-DQ associated factor VIII peptides presented by monocyte-derived dendritic cells

The development of anti-factor VIII antibodies is a major complication of the treatment of patients with hemophilia A. Generation of high affinity anti-factor VIII antibodies is dependent on help provided by CD4⁺ T cells that recognize factor VIII-derived peptides presented on class II major histocompatibility complex on the surface of antigen-presenting cells. In order to identify the immune-dominant epitopes that can be presented to CD4⁺ T cells, we previously developed a mass spectrometry-based method to identify factor VIII-derived peptides that are presented on human leukocyte antigen (HLA)-DR. In the present work, we compared the repertoire of FVIII-derived peptide presented on HLA-DR and HLA-DQ. Monocyte-derived dendritic cells from nine HLA-typed healthy donors were pulsed with recombinant factor VIII. HLA-DR and HLA-DQ molecules were purified using monoclonal antibodies. Our data show that HLA-DQ and HLA-DR present a similar repertoire of factor VIII-derived peptides. However, the number of peptides associated with HLA-DQ was lower than that with HLA-DR. We also identified a peptide, within the acidic a3 domains of factor VIII, which is presented with higher frequency on HLA-DQ. Interestingly, this peptide was found to have a higher predicted affinity for HLA-DQ than for HLA-DR. Taken together, our data suggest that HLA-DQ participates in the presentation of factor VIII peptides, thereby contributing to the development of inhibitory antibodies in a proportion of patients with severe hemophilia A.

F8 gene mutation profile in Indian hemophilia A patients: Identification of 23 novel mutations and factor VIII inhibitor risk association

'FVIII inhibitors', especially in severe hemophilia A (HA) patients, is a serious adverse effect that complicates their clinical management. Many genetic and non-genetic risk factors have been proposed for FVIII inhibitor development, diverse in different population groups. This is the first study in Indian hemophiliacs that analyzes inhibitor risk in relation to the complete F8 mutation profile, in a case-control study that included 145 Indian severe HA patients, i.e. 69 inhibitor positive (with 18 inhibitor concordant/discordant family members), and 58 inhibitor negative patients, after informed consent. While 53.54% (68/127) index cases were positive for intron 22 or intron 1 inversions, 55 causative F8 mutations were detected in the 59 inversion negative patients, of which 23 were novel mutations (in 24 patients) and 32 were reported earlier (in 35 patients). A higher incidence of mutations, in the C1 and C2 domains in inhibitor positive patients, and in the A1 domain in inhibitor negative patients was observed, though not significantly different. The study suggests that large F8 rearrangements (significantly higher in the inhibitor positive patients) pose the highest risk, while missense mutations (significantly higher in the inhibitor negative patients) pose the lowest risk of inhibitor development in Indian hemophilia A patients.

Antibody profile in Indian severe haemophilia A patients with and without FVIII inhibitors

Diagnosis and management of haemophilia patients with inhibitors is often tricky due to the heterogeneous nature of the antibodies with regard to their kinetics, as well as the co-existence of other interfering antibodies. Plasma samples from severe haemophilia A patients from India with and without FVIII inhibitors were analysed for the presence of possible co-existing antibodies such as lupus anticoagulants (LA), anti-cardiolipin antibodies (ACLA), anti-β2-glycoprotein-I (anti-β2-GP-I) antibodies, viral transfusion transmitted disease (HIV, HBsAg, HCV) related antibodies, anti-cyclic citrullinated peptides (anti-CCP), and anti-nuclear antibodies. A high incidence of LA and anti-HCV antibodies was detected in Indian haemophilia A patients similar to earlier reports. More importantly, a relatively high incidence of autoantibodies to nuclear antigens (18.62%) and anti-CCP antibodies (1.38%) associated with autoimmune disorders was also seen in these congenital haemophilia A patients with and without inhibitors. Knowledge on the antibody profile in these haemophilia patients especially in those with FVIII inhibitors along with correlation with the clinical manifestations and other risk factors for inhibitor development could possibly shed more light on the complex immune response in these patients.