M2e-specific monoclonal antibody cocktails against influenza A virus are superior to individual monoclonal antibody treatments, universally effective, and viral escape mutant resistant

ABSTRACT Influenza, a negative sense single-strand RNA virus of the genus Orthomyxoviridae, causes respiratory illness in humans and animals and significant morbidity and mortality worldwide. While exposure to a specific influenza A strain causes homologous protection, two immune-dominant influenza A virus (IAV)-encoded epitopes - Hemagglutinin (HA) and Neuraminidase (NA) - undergo antigenic shift and drift, resulting in IAVs to which humans lack pre-existing immunity. Without a universal vaccine or therapeutic agent, influenza virus infections will significantly threaten human health. The extracellular domain of the Matrix protein 2-ion channel (M2e) is an ideal antigenic target for a universal influenza therapy: it is highly conserved across influenza A serotypes, has a low mutation rate, and is essential for viral entry and replication. However, less than 20% of humans generate M2e-specific antibodies in response to IAV exposure, thus lacking the benefits of M2e-MAb-mediated immunity. To therapeutically address this deficit, we generated several non-neutralizing M2e-specific monoclonal antibodies (M2e-MAbs) with strong universal IAV treatment potential. Using three MAbs that bind to M2e differentially and competitively, we developed a low-dose M2e-MAb triple cocktail as an effective universal prophylactic and therapeutic agent. We identified the low-dose M2e-MAb triple cocktail’s optimal antibody-clone combination, isotype, minimum effective dosage, and administration time points in mouse models challenged with human and zoonotic BSL-2 and BSL-3 IAV strains, demonstrating its universal potential. Using the IgG2a isotype, which had proven most effective, we established FcγRI, FcγRIII, and FcγRIV as required for M2e-MAb-mediated protection of IAV-challenged mice. Importantly, we established individual M2e-MAbs and the resulting triple cocktail as effective and viral escape mutant-resistant treatments in immunocompetent and immunodeficient mice. These unique qualities provide precedence for prioritizing our M2e-MAbs for therapeutic development. CONFLICT OF INTEREST STATEMENT SP serves on the scientific advisory board for Shoreline Biosciences, Qihan Biotechnology and is a Scientific Consultant for Qihan Biotechnology and the Genomics Institute of the Novartis Research Foundation. The remaining authors declare no competing interests.