The influenza matrix protein 2 as a vaccine target.

Matrix protein (M)2 is an Influenza A, type III membrane protein with an extracellular domain (ectodomain of M2 [M2e]) of 23 amino acid residues, which is strongly conserved across virus strains. M2 fulfills an important biological function in the life cycle of the Influenza A virus and has been a target of antiviral drugs. M2e has generated much interest as a potential vaccine target, and a clinical M2e vaccine trial was initiated in 2007. The advantage of M2e compared with hemagglutinin, the prime antigen target in conventional influenza vaccines, is that its sequence is conserved. This means that a stable, efficacious and easily produced M2e-based vaccine would provide protection not only against drifting seasonal influenza epidemic strains, but would also make it possible to vaccinate in anticipation of an emerging pandemic. Furthermore, most reported M2e-based vaccines are produced by economical and safe technologies. IgG subtype antibodies directed against M2e can prevent death from influenza and reduce morbidity in animal models for influenza disease. The immunological mechanism that mediates protection by anti-M2e antibodies is not completely understood, but it probably involves antibody-mediated cellular cytotoxicity. This review summarizes the findings on M2e vaccine candidates and addresses some of the key unanswered questions about this promising Influenza A vaccine target: what is its likely mechanism of action? Which measurable parameters correlate with protection? And what can be expected from clinical use of an M2e-based vaccine? [ABSTRACT FROM AUTHOR]