Table I. Humoral and cellular immune mechanisms for M2e immunity.

M2e mAb, M2e specific monoclonal antibody; M2e-HBc, M2e-hepatitis B virus core fusion protein; M2 VLP, virus-like particles (VLP) presenting the wild type M2 protein; M2e5x VLP, VLP presenting a heterologous tandem repeat of M2e epitope sequences (M2e5x) of human, swine, and avian origin influenza A viruses; NK cells, natural killer cells; ADCC, antibody-dependent cellular cytotoxicity; CTA1-M2e-DD, M2e fusion protein vaccine to cholera toxin subunit A1 and a dimer of the D-fragment of Staphylococcus aureus protein A; AS04, adjuvant of alum plus monophosphoryl lipid A (MPL), Protection against body weight loss indicates significantly improved cross protection by preventing severe weight loss.