High levels of anti-FVIII IgG4 and IgG total are associated with immune tolerance induction failure in people with congenital haemophilia A and high-responding inhibitors

Background Immune tolerance induction (ITI) is the treatment of choice to eradicate neutralizing anti-factor VIII (FVIII) alloantibodies (inhibitors) in people with inherited haemophilia A (PwHA). However, it is not successful in 10%-40% of the cases. The biological mechanisms and biomarkers associated with ITI outcome are largely unknown. Objectives The aim of this study was to investigate the association of plasma cytokines (INF-γ, TNF, IL-2, IL-4, IL-5, IL-6, IL-10, and IL-17A), chemokines (IL-8/CXCL8, RANTES /CCL5, MIG/CXCL9, MCP-1/CCL2 and IP-10/CXCL10) and anti-FVIII immunoglobulin (Ig)G total, IgG1 and IgG4 with ITI outcome. Methods In this cross-sectional analysis of the BrazIT Study, we assessed plasma levels of anti-FVIII IgGs using an enzyme-linked immunosorbent assay (ELISA) with plasma-derived FVIII (pdFVIII) and recombinant FVIII (rFVIII) as target antigens, immobilized in microplates. Results We assayed 98 plasma samples of moderately-severe and severe (FVIII activity < 2%) PwHA after completion of a first ITI course. Levels of anti-rFVIII IgG total and IgG4 were higher in PwHA who failed ITI (IgG total optical density [OD], 0.37; interquartile range [IQR] 0.15-0.73; IgG4 OD, 2.19; IQR 0.80-2.52) compared with those who had partial (IgG total OD, 0.03; IQR 0.00-0.14; IgG4 OD, 0.39; IQR 0.09-1.11; p < 0.0001 for both) and complete success (IgG total OD, 0.04; IQR 0.00-0.07; IgG4 OD, 0.07; IQR 0.06-0.40; p < 0.0001 for both). Plasma cytokines, chemokines and anti-FVIII IgG1 were not associated with ITI outcome. Conclusions Our results showthat high levels of plasma anti-FVIII IgG4 and IgG total are associated with ITI failure.