Neutralizing human monoclonal antibody against H5N1 influenza HA selected from a Fab-phage display library

Identification of neutralizing antibodies with specificity away from the traditional mutation prone antigenic regions, against the conserved regions of hemagglutinin from H5N1 influenza virus has the potential to provide a therapeutic option which can be developed ahead of time in preparation for a possible pandemic due to H5N1 viruses. In this study, we used a combination of panning strategies against the hemagglutinin (HA) of several antigenic distinct H5N1 isolates to bias selection of Fab-phage from a naive human library away from the antigenic regions of HA, toward the more conserved portions of the protein. All of the identified Fab clones which showed binding to multiple antigenically distinct HA were converted to fully human IgG, and tested for their ability to neutralize the uptake of H5N1-virus like particles (VLP) into MDCK cells. Five of the antibodies which showed binding to the relatively conserved HA2 subunit of HA, exhibited neutralization of H5N1-VLP uptake in a dose dependant manner. The inhibitory effects of these five antibodies were similar to those observed with a previously described neutralizing antibody specific for the 140s antigenic loop present within HA1 and highlight the exciting possibility that these antibodies may be efficacious against multiple H5N1 strains.