Finally, to determine if the M2e-NSP4 vaccine could protect against infection with a heterosubtypic influenza virus, two groups of mice were immunized three times s.c. with either 10 μg of M2e or 10 μg of M2e-NSP4, and in two separate experiments these mice were challenged with a lethal dose of H7N7, differing from the M2e consensus sequence by 5 amino acids. This evidence concerns the gene PRSS57 and infection.