Modulating immunogenicity of factor IX by fusion to an immunoglobulin Fc domain: a study using a hemophilia B mouse model.
Essentials Fc-fusion increases a therapeutic's half-life, but FcγR interactions may impact immunogenicity. Species-specific Fc-FcγR interactions allow for mechanistic in vivo studies using mouse models. Fc fusion modulates the immune response to factor IX in hemophilia B mice by eliciting Th1 bias. This model could inform future studies of IgE-associated anaphylaxis in hemophilia B patients.



Background Fc fusion is a platform technology used to increase the circulating half-life of protein and peptide therapeutics. However, there are potential immunological consequences with this approach, such as changes in the molecule's immunogenicity as well as possible interactions with a repertoire of Fc receptors (FcR) that can modulate immune responses. Objectives/Methods Using a mouse hemophilia B (HB) model, we compared the immune responses to infusions of recombinant human factor IX (hFIX) and hFIX fused to mouse IgG2a-Fc (hFIX-mFc). The mFc was employed to allow species-specific Fc-FcγR interactions. Results Although treatment with hFIX-mFc altered the early development of anti-FIX IgG, no significant differences in anti-FIX antibody titers were observed at the end of the treatment regimen (5 weeks) or upon anamnestic response (5 months). However, treatment with hFIX-mFc elicited higher FIX-neutralizing antibody levels and resulted in reduced IgE titers compared with the hFIX-treated group. Additionally, differences in plasma cytokine levels and in vitro CD4+T-cell responses suggest that whereas hFIX treatment triggered a Th2-biased immune response, hFIX-mFc treatment induced Th1-biased CD4+T cells. We also show that hFIX-mFc bound to soluble FcγRs and engaged with FcγRs on different cell types, which may impact antigen presentation. Conclusions These studies provide a model system to study how Fc-fusion proteins may affect immune mechanisms. We used this model to demonstrate a plausible mechanism by which Fc fusion may modulate the IgE response to hFIX. This model may be appropriate for investigating the rare but severe IgE-mediated anaphylaxis reaction to hFIX infusions in HB patients.
Hemostasis Branch, Division of Plasma Protein Therapeutics, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
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Levin
Hemostasis Branch, Division of Plasma Protein Therapeutics, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
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Lagassé
Department of Otorhinolaryngology-Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
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Burch
Department of Otorhinolaryngology-Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD, USA.
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Strome
CRISPR Therapeutics, Cambridge, MA, USA.
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Tan
Editas Medicine, Cambridge, MA, USA.
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Jiang
Hemostasis Branch, Division of Plasma Protein Therapeutics, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
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Sauna
Plasma Derivatives Branch, Division of Plasma Protein Therapeutics, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
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Golding
D000818:Animals; D017951:Antigen Presentation; D001780:Blood Coagulation Tests; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D004195:Disease Models, Animal; D005164:Factor IX / Q000235:genetics / Q000276:immunology*; D005260:Female; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D002836:Hemophilia B / Q000235:genetics / Q000628:therapy*; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007141:Immunoglobulin Fc Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D017452:Receptors, IgG / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000276:immunology; D020349:Surface Plasmon Resonance
D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D007073:Immunoglobulin E; D005164:Factor IX
Fc receptors; Th1-Th2 balance; factor IX; hemophilia B; immunoglobulin Fc fragment