The epitope recognized by a monoclonal antibody in influenza A virus M2 protein is immunogenic and confers immune protection

Based on our previous study that the monoclonal antibody (mAb) 8C6 recognizing the extracellular domain of influenza A virus M2 protein (M2e) could passively induce protective immunity in mice, epitope mapping was performed in this study. A series of eight mutated M2e were constructed and expressed. It was found in immunoblotting assay that 8C6 could not bind to two of the mutated M2e proteins, which suggested the VETPIR epitope (aa7-12) in M2e for mAb 8C6. More important, EVETPIRN-peptide (aa6-13) conjugated immunogen induced high M2e specific antibody titer (1:25,600) in mice after booster immunization, and provided mice significantly 40% higher survival rate compared with the control group in challenge assay (p=0.0215), which suggested the EVETPIRN-epitope was immunogenic and actively conferred immune protection to some extent. In addition, sequence comparison suggested the EVETPIRN sequence (aa6-13) was highly conserved in all human influenza A strains. All these data suggested the EVETPIRN sequence in M2e could be one new target for influenza vaccine design.