HA2-specific monoclonal antibodies as tools for differential recognition of influenza A virus antigenic subtypes

Antigenic reactivity of a set of monoclonal antibodies (MAb) raised against the HA2 subunit of hemagglutinin of H3 subtype was characterized in a rapid culture assay. MAbs FC12 and FE1, known to recognize the same antigenic site (IV), cross-reacted with influenza viruses of H3 and H4 subtypes, regardless of their host origin. No cross-reactivity was detected with other antigenic subtypes tested (H1–H13). The involvement of conserved residues D160, N168, and F171 in the differential recognition of H3 and H4 subtypes is proposed. In contrast, MAb IIF4 that recognizes antigenic site II exhibited a broader inter-subtype reactivity including subtypes H3, H4, H5, H8 and some viruses of H2, H6 and H13 subtypes. The ability of HA2-specific antibodies to differentially react with distinct antigenic subtypes can be utilized in development of diagnostics and in the influenza virus surveillance.