Antigen-specific immunotherapy with apitopes suppresses generation of FVIII inhibitor antibodies in HLA-transgenic mice

• Published in: Blood advances Vol. 6; no. 7; pp. 2069 - 2080
• Main Authors: Pletinckx, Katrien, Nicolson, Kirsty S., Streeter, Heather B., Sanderson, William J., Schurgers, Evelien, Jansson, Lotta, Wraith, David C.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 12.04.2022; American Society of Hematology
• Subjects: Animals; Hemophilia A - genetics; Humans; Immune Tolerance; Immunobiology and Immunotherapy; Immunologic Factors; Immunotherapy; Mice; Mice, Transgenic
• ISSN: 2473-9529; 2473-9537
• DOI: 10.1182/bloodadvances.2021004451

Hemophilia A (HA) is a blood clotting disorder that is caused by various genetic deficiencies in the factor VIII (FVIII)-encoding F8 gene. Patients receiving FVIII-replacement therapy are at risk for developing neutralizing antibodies (FVIII inhibitors), rendering the FVIII-replacement therapy ineffective. Immunological tolerance toward FVIII can be achieved through immune tolerance induction protocols in some patients, but this is a lengthy and costly desensitization program. Long-term eradication of inhibitors in patients with HA could be achieved by antigen-specific immunotherapy targeting CD4+ T-cells, because formation of FVIII inhibitors is T-cell dependent. Here, we report a peptide-based antigen-specific immunotherapy that is designed to specifically reestablish immune tolerance to FVIII through the development of antigen-processing-independent epitopes (apitopes). We identified 2 FVIII immunodominant peptides in immunized HLA-DRA*0101/DRB1*1501 transgenic (HLA-DR2tg) mice that were optimized for tolerogenicity. These modified peptide analogs were initially screened for recognition using FVIII-specific T-cell hybridoma clones from FVIII-immunized HLA-DR2tg mice. The FVIII apitopes were promiscuous and bound common human HLA-DRB1* allelic variants. The combination of these 2 FVIII apitopes (ATX-F8-117), administered according to a dose-escalation protocol, promoted T-cell tolerance toward FVIII in HLA-DR2tg mice. Furthermore, treatment with ATX-F8-117 significantly reduced FVIII inhibitor formation. ATX-F8-117 regulates anti-FVIII T-cell and B-cell responses, specifically the generation of FVIII inhibitors, revealing peptide-based antigen-specific immunotherapy as a promising approach to suppress and treat inhibitor formation in susceptible patients with HA. •ATX-F8-117 induces tolerance toward FVIII, thereby suppressing neutralizing antibody formation.•ATX-F8-117 has the potential to treat inhibitor formation in susceptible patients with HA. [Display omitted]