Objective: To isolate the cross-reactive antibodies against hemagglutinin of influenza virus and identify its biological function. Methods: The antibodies gene reservoir of cross-reactive and H5N1 pseudotype particles neutralizing B cell circulating in peripheral blood of a human H5N1 case was recovered by in vitro B cell culture, screening, RT-PCR and expression vector cloning techniques. The Ab gene pairing was screened by transient transfection of human kidney 293T cells and detected using ELISA and neutralization test. The heterosubtypic antibodies were prepared and characterized. Results: We discovered the VH1-2-based heterosubtypic antibodies from two B cell lineages could neutralize GX-H5N1 pseudotype particles and have broader binding with Group 1 (including H1, H5, H6 and H9) and H7 subtype. Conclusions Cross-reactive antibodies can be induced by H5N1 infection.

Objective: To develop the chimeric antibodies against neuraminidase (NA) of H7N9 and to identify their biological activity and function. Methods: The genes of variable regions of the light chain (VL) and heavy chain (VH) obtained by mouse hybridoma technology were cloned respectively into the expression VH and VL vectors bearing human-derived Cγ1, and Cκ1 and co-transfected into 293T cells. The chimeric antibodies were purified and their functions were investigated. Results: Two chimeric antibodies, 1E2 and 3E3 against neuraminidase (NA) of H7N9 were obtained. Both antibodies recognized similar antigenic epitopes. MAb 1E2 and 3E3 could prevent the infectivity with H7N9 and H11N9 virus and reduce their size of viral plaque. Conclusions The chimeric antibodies specific for N9 could prevent the infection of N9 subtype influenza virus as well as the NAI-resistant mutants and could be a potential immunotherapy approach for H7N9 treatment.