Aspectos clínicos, genéticos e imunológicos dos pacientes com hemofilia A grave e moderadamente grave com anticorpos inibitórios contra o fator VIII

Abstract

Hemophilia A (HA) is a hereditary bleeding disoder characterized by deficiency of coagulation factor VIII (FVIII) resulting from mutations in the gene F8. Bleeding is the main clinical manifestation of the disease and is inversely proportional to the level of residual FVIII activity. Replacement of deficient FVIII is indicated for bleeding control of episodic and prophylaxis of bleeding. In 20-35% of patients with severe HA, exposure to exogenous FVIII can trigger the development of neutralizing alloantibodies against FVIII (inhibitors). Inhibitor eradication is possible in 60-80% of patients through immunotolerance induction (ITI). The risk factors for the development of inhibitors and the biological mechanisms involved in their genesis are not completely known. The present study is a subproject of the HEMFIL Study, a multicenter prospective cohort, and aimed to identify new risk factors for inhibitors against FVIII in patients with HA, analyzing clinical, genetic and immunological variables. Patients with residual FVIII activity < 2% were included from October, 2013 to December, 2021. Clinical data were obtained from standardized questionnaires applied at patient inclusion before any infusion or up to a maximum of five days of exposure (DE) to FVIII (T0) and during follow-up until inhibitor development (INB+) or until reaching 75 DE without inhibitor development (INB-) (T1). INB+ patients who underwent ITI were followed until completion of ITI (T2). The immunological profile (IgG1, IgG4, total IgG, cytokines and chemokines) was analyzed in blood samples collected at times T0, T1 and T2. Inheritance of HA, evaluation of F8 variants and HLA typing were determined and related to inhibitor development. The associations between immunological biomarkers and the developmentof inhibitors were analysed using Pearson's Chi-square test or Fischer's exact test. Group effects were compared using the Wilcoxon or Kruskal-Wallis test. Longitudinal effects were compared with the Wilcoxon exact rank test. The correction for multiple tests was performed using the false discovery rate (q values). The significance level was set at 0.05. A total of 108 patients were included. Eight patients (7.5%) were excluded, of whom 4 (3.7%) due to loss to follow-up and 4 (3.8%) for not reaching T1 at the time of this analysis. Thus, 100 patients were enrolled, of whom 80 (80%) had no exposure to FVIII and 20 (20%) were minimally exposed. Thirty-seven (34.0%) patients developed an inhibitor, and 32 (86.5%) high response (all 32 were referred to ITI). By October 2023, 11 (34.3%) patients had achieved a complete response, 6 (18.7%) a partial response, 6 (18.7%) had failure and 9 (28.3%) were still on ITI. The median age at inhibitor development was 0.8 years. High-risk mutations were more prevalent in INB+. The immunological profile analysis showed no difference between INB+ and INB- patients at T0. In contrast, in T1, INB+ patients who failed ITI presented higher medium levels of interleukin (IL) 2 (3.50; IC 95% 2.42-14.60 vs 0.85; IC 95% 0.77-1.14; p = 0.016), IL-10 (3.46; IC 95% 2.24-14.14 vs 0.74; IC 95% 0.52-1.43; p = 0.035), tumor necrosis factor (TNF) (11.18; IC 95% 7.03-37.18 vs 0.93; IC 95% 0.59-1.56; p = 0.016), interferon-gama (INF (98.57; IC 95% 76.46-664.86 vs 3.57; IC 95% 1.63-5.88; p = 0.035) and chemokine CCL5 (5,245.11; IC 95% 4,554.02-5,554.62 vs 3,107.86 (IC 95% 2,148.74 – 3,589.40; p = 0.037) in comparison with PwHA who who achieved a complete response, respectively. The analysis of HA inheritance demonstrated that the percentage of sporadic HA increased of the studied population in the 2020s. No association was found between HLA class II DRB1, DQA1 and DQB1 and the presence of an inhibitor. We conclude that IL-2, IL-10, TNF, INF and CCL5 could be potential predictors of IT outcome,although these findings require confirmation in other studies.