Broadly cross-reactive monoclonal antibodies against HA2 glycopeptide of Influenza A virus hemagglutinin of H3 subtype reduce replication of influenza A viruses of human and avian origin.

The reactivity of monoclonal antibodies (MAbs) prepared to the HA2 glycopeptide (gp) of A/Dunedin/4/73 (H3N2) hemagglutinin was tested against influenza A viruses of H3, H4, and H7 subtypes. Only one (CF2) out of six MAbs reacted with influenza A viruses of all three subtypes (H3, H4 and H7). The inter-subtype reactivity of this MAb (CF2) is in accord with the highly conservative sequence in the previously defined MAb-binding site I, i.e. the aa 1-38 of N-terminus of HA2 gp. MAb CF2 as well as inter-subtype cross-reactive MAb IIF4, recognizing the binding site II of HA2 gp, were tested for their effect on replication of influenza A viruses. Both these MAbs reduced the number of plaques of viruses of homologous (H3) as well as heterologous (H4) virus subtypes, the latter less efficiently. The potential of these MAbs to influence in vivo replication of influenza A viruses of various subtypes is discussed.