Expression And Characterization Of A Monoclonal Iga Isotype Antibody Against Group 1 And Group 2 Influenza Of The Hv1-18 Qxxv Class

Examining cross-reactive influenza-specific human monoclonal antibodies can inform the rational design of universal flu vaccines. The vast majority of monoclonal antibodies studied to-date are of the IgG isotype or cloned into IgG vectors for expression. However, IgA isotype antibodies are also of interest, especially given their increased concentrations in the respiratory tract where the influenza virus replicates. To acquire anti-influenza monoclonal antibodies that are of both IgG and IgA isotypes, we used a fluorescently labeled hemagglutinin (HA) for fluorescence-activated cell sorting on memory B cells 14 days post-influenza vaccination. We then sequenced paired heavy and light chains with the 10× Genomics platform and chose relevant sequences to synthesize for expression and characterization. An IgA1 antibody of the HV1-18 QxxV class demonstrated binding to both group 1 and group 2 HA subtypes in enzyme-linked immunosorbent assays. Although Hemagglutinin inhibition assays were negative, neutralizing activity was positive in a microneutralization activity, at levels comparable to other published stalk-binding and neutralizing monoclonal antibodies, FI6v3 and CR9114. By testing the antibody against a panel of HA mutants, we found that the antibody bound to a region of the HA stalk previously reported for IgG1 antibodies of this class. Studies are on-going, but thus far demonstrate a broadly cross-reactive and neutralizing IgA antibody that recognizes the HA stalk of both group 1 and group 2 influenza viruses.