Immune sera were collected after boost immunization of BLAB/c mice (n= 5 per group) with N1 NA protein (A/Cal H1N1), N2 NA protein (A/Wis H3N2), M2e5x VLP, split vaccine (A/PR8 H1N1, A/Cal H1N1), or whole A/Phil H3N2 virus. Whole inactivated virus particles and M2e peptide were used as ELISA coating antigens: (A) A/Cal H1N1, (B) rgH5N1, (C) A/PR8 H1N1, (D) A/Wis H3N2, (E) A/Phil H3N2 or (F) M2e peptide. Sera were pooled and serially diluted.