A monoclonal antibody recognizes a highly conserved neutralizing epitope on hemagglutinin of H6N1 avian influenza virus

•A conserved epitope on the H6 HA was identified by the EB2 mAb.•EB2-defined epitope was located at R198p fragment on the globular head of HA.•Alignment results showed that the epitope was conserved and specific to H6.•EB2 mAb showed neutralizing activity against two strains of H6N1 AIV from Taiwan.•The epitope inducting mice pAb showed neutralizing activity similar to EB2.

Neutralizing antibodies on the globular head of the hemagglutinin (HA) of avian influenza virus (AIV) are crucial for controlling this disease. However, most neutralizing antibodies lack cross reaction. This report describes the identification of a hemagglutinin epitope on the globular head near the receptor binding site of the H6N1 AIV. A monoclonal antibody named EB2 was prepared against the H6N1 AIV HA. Flow cytometry of AIV-infected chicken embryo fibroblast, DF-1 cells and specific-pathogen-free embryonated eggs were used to verify the neutralizing activity of this mAb. To narrow down the binding region, partially overlapping HA fragments and synthetic peptides were used to map the epitope by immune-blotting. The linear motif RYVRMGTESMN, located on the surface on the globular head of the HA protein, was identified as the epitope bound by EB2 mAb. Alignment of the EB2-defined epitope with other H6 AIVs showed that this epitope was conserved and specific to H6. We propose that this motif is a linear B-cell epitope of the HA protein and is near the receptor binding site. The identified epitope might be useful for clinical applications and as a tool for further study of the structure and function of the AIV HA protein.