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

Our results showed that the H5N1-M2e tetrameric peptide vaccine, together with either FA or SAS, induced a high antibody response that was able to effectively cross-react with H7N9-M2e (Figure 2) . The vaccinations thus protected the mice from a lethal challenge with the H7N9 virus ( Figure 3) . The survival rate of H5N1-M2e-vaccinated mice against a H7N9 lethal challenge was 80%, which was the same as that of H5N1-M2e-vaccinated mice against a H5N1 lethal challenge. 20 Consistently, viral load and lung damage in H5N1-M2e-vaccinated mice were much lower and less severe than that in adjuvant-or PBSinjected mice (Figure 4) . Although T-cell responses induced by an M2e-based vaccine have been reported previously, the protection by the M2e vaccination was mainly attributed to the induced antibodies but not the T cells. 19 Similarly, our results showed that the crossprotection of the H5N1-M2e vaccination was directly related to the levels of cross-reactive antibodies toward the M2e of challenge viruses. Unlike vaccinations with inactivated viruses, HA-subunit vaccines and VLP vaccines, which may provide complete protection against infection by homogenous viruses but poor cross-protection against infection by heterogeneous viruses, our results illustrate that the H5N1-M2e tetrameric peptide vaccine can provide satisfactory cross-protection against infection with a novel influenza virus that has newly emerged in humans.