An H5N1-based matrix protein 2 ectodomain tetrameric peptide vaccine provides cross-protection against lethal infection with H7N9 influenza virus

Leung, Ho-Chuen; Chan, Chris Chung-Sing; Poon, Vincent Kwok-Man; Zhao, Han-Jun; Cheung, Chung-Yan; Ng, Fai; Huang, Jian-Dong; Zheng, Bo-Jian

As shown in Figure 1 , a difference of five amino acids was observed between the sequences of H5N1-M2e and H7N9-M2e. To examine whether these variations would affect the reaction of the antibody induced by the H5N1-M2e vaccine and H7N9-M2e, we tested the antibody titers in serum samples collected from H5N1-M2e-vaccinated mice using ELISA with plates coated with H5N1-M2e and H7N9-M2e, respectively. The titers of immunoglobulin G antibody specific to H7N9-M2e ( Figure 2A ) and H5N1-M2e ( Figure 2B ) were gradually increased in mouse serum samples collected after each vaccination, reaching very high levels (.1:10 5 ) 10 days after the last booster vaccination. By contrast, M2e-specific antibody was undetectable in serum samples collected from mice vaccinated with FA, SAS, or PBS alone. The adjuvant effect of SAS seemed to be better than that of FA because H5N1-M2e plus SAS induced a higher level of antibody responses. Importantly, the antibody titers specific to H5N1-M2e and H7N9-M2e were similar (P . 0.05). These results indicate that H5N1-M2e vaccination induced a high level of M2e-specific antibody that effectively cross-reacted with H7N9-M2e, although a difference of approximately 21% (5/24) amino acids was identified between the sequences of H5N1-M2e and H7N9-M2e.