Inhibitor titers and levels of regulatory T cell markers in patients with hemophilia at Moi Teaching and Referral Hospital

Abstract

Background: Development of inhibitors is one of the most serious complications in treatment of patients with hemophilia (PWH). Inhibitors render replacement therapy ineffective. Inhibitor testing is critical; however this has not been fully implemented at health facilities in resource restricted countries including Moi Teaching and Referral Hospital (MTRH) in Kenya. Several barriers have led to lack of data on the prevalence of inhibitors in these regions. Regulatory T cells (Tregs) have recently been identified as the main cells that control the response of B cells to both FVIII and FIX inhibitors. Typically, the formation of antibodies in response to proteins used as therapeutics is dependent on T-cells whereas active suppression has been suggested to promote tolerance when changing from Tregs activation to Tregs induction. Objective: To determine the prevalence of FVIII and FIX inhibitors and correlation between inhibitor titers and levels of Tregs (CD4+CD25+FOXP3+) in PWH at MTRH. Methods: This was a cross-sectional study involving PWH at MTRH. Convenient sampling technique was used to select the study participants between the months of Jan- Oct 2019. Demographic and clinical data were collected using data collection forms. Venous blood in sodium citrate tube (4mL) and EDTA tube (1mL) were collected by a skilled phlebotomist for factor, inhibitor, and flow cytometry assays respectively. The characteristics of the study participants were described using means, standard deviations and relative proportions. Fishers’ exact test was used to compare disease severity (%) and inhibitor titers (BU). Spearman’s rank correlation was used to determine the correlation between inhibitor titers (BU) and (%) levels of Tregs. P value < 0.05 was used a cut-off to assess the level of significance of the results. Results: A total of 88 participants were recruited; out of which hemophilia A (HA) were 71 (81%) and hemophilia B (HB) were 17 (19%). Out of the 71 HA patients 52 (73%) were severe, 10 (14%) moderate and 9 (13%) mild cases. Out of the 17 patients with HB, 14 (82%) were severe, 1 (6%) moderate and 2 (12%) mild cases. The overall prevalence of inhibitors was 14% (12 out of 88). All those who developed inhibitors were HA and their titers ranges were (0.6 BU – 69 BU). Out of the 12 patients who developed inhibitors, 10 of them were severe HA and only 2 were mild HA. The levels of Tregs ranges were between 0.25% and 6%. Inhibitor titers and Tregs were observed to correlate negatively (-0.3803), p value = 0.003. Alteration in levels of Treg markers had an effect on inhibitor titers; those with low levels of Treg markers showed high inhibitor titers and vice versa. Conclusion: The prevalence of inhibitors among PWH at MTRH during the study period was 14%, which was comparable to that reported in other parts of the world. Tregs may have the potential to serve as novel markers and therapeutic target for amelioration or prevention of inhibitor development among PWH. Recommendations: There is need for adoption of routine inhibitor testing for all PWH throughout the country. Secondly, there is need for further research to explore the potential of Tregs as novel markers and a therapeutic target for the prevention of inhibitor development.