Immunization with M2e-MAP K2 protects against challenge with M2e-variant viruses.

<p>(<b>A</b>) Amino acid sequence comparison of M2e from influenza A/PR8 (P10) or M2e-escape mutant viruses (P10H and P10L) as described in Ref. 9. (<b>B</b>) Sera from BALB/c mice immunized i.n. three times with K2 peptide and adjuvants were assayed in an ELISA on peptides with M2e sequences as shown in (<b>A</b>) or control peptide cysBB: cysteine back-bone. (<b>C</b>) Pooled sera (1∶250 dilution) from BALB/c mice (n = 5 mice) immunized as in (<b>B</b>) were assayed in an ELISA for binding to MDCK cells infected with influenza virus A/PR/8, the M2e-escape mutants P10H and P10L, A/FM and B/Lee. The monoclonal anti-M2e Ab 14C2 (1 µg/mL) is shown as control. (<b>D</b>) BALB/c mice (n = 5 mice/group) immunized i.n. with K2 peptide and adjuvants were challenged with 1000 TCID₅₀/50 µL influenza virus A/PR/8, P10H and P10L three weeks after the third vaccine administration. Infectious virus in the lungs was determined 5 days after challenge.