Hemagglutinin Immunoglobulin M (IgM) Monoclonal Antibody that Neutralizes Multiple Clades of Avian H5N1 Influenza A Virus

Abstract

The hemagglutinin (HA) of influenza A virus plays an essential role in mediating the entry of the virus into host cells. In this study, 4 HA monoclonal antibodies (MAbs) of immunoglobulin M (IgM) isotype were generated by using recombinant full-length HA protein, which was expressed and purified from the baculovirus-insect cell system, from a H5N1 isolate (A/chicken/hatay/2004(H5N1)). Western blot analysis showed that these IgM MAbs bind the HA1 subunit and prevent HA-induced agglutination of erythrocytes. Consistently, the IgM MAbs inhibits the entry of HA pseudotyped lentiviral particles into Madin-Darby Canine Kidney (MDCK) cells. The most potent MAb, MAb 4F3, was further shown to efficiently neutralize multiple clades of H5N1 influenza A virus. To our knowledge, there are few studies documenting the properties of H5N1 neutralizing antibodies of IgM isotype. Thus, this panel of MAb adds diversity to the repertoire of broadly neutralizing monoclonal antibodies that are useful for developing novel therapeutics for combating future outbreaks of H5N1.