Fine-epitope mapping of an antibody that binds the ectodomain of influenza matrix protein 2

Our previous work found that the monoclonal antibody 8C6, which recognized the epitope EVETPIRN on influenza A virus M2 protein, conferred protection against influenza virus challenge. In this study, 8C6 was used to screen the 7-mer phage peptide library in order to identify the crucial amino acid residues on the protective epitope EVETPIRN. Nine positive phage clones were selected by a test of dose-dependent binding activity to 8C6 after three rounds of panning. The phage clones exhibited a consensus motif (TXXR), which was found on the epitope EVETPIRN. Site-directed mutation analysis indicated that Thr and Arg on the epitope EVETPIRN played a key role in the recognition by 8C6. Furthermore, sequence alignment and analysis revealed that Thr and Arg on the epitope were highly conserved. Our results could provide useful information for influenza vaccine design based on M2 mimotope.