Intranasal vaccination with M2e5x virus-like particles induces humoral and cellular immune responses conferring cross-protection against heterosubtypic influenza viruses

Current influenza vaccines do not provide broad cross-protection. Here, we report that intranasal vaccination with virus-like particles containing the highly conserved multiple ectodomains of matrix protein 2 (M2e5x VLP) of influenza virus induces broad cross-protection by M2-specific humoral and cellular immune responses. M2e5x VLP intranasal vaccination prevented severe weight loss, attenuated inflammatory cytokines and cellular infiltrates, and lowered viral loads, and induced germinal center phenotypic B and plasma cells. In addition, depletion studies demonstrate the protective roles of CD4 and CD8 T cells induced by M2e5x VLP intranasal vaccination. Thus, this study provides evidence that mucosal delivery of M2e5x VLP vaccine provides cross-protection by inducing humoral and cellular immune responses.