To determine the conservation of the identified epitopes among IAVs, the aa sequences of P3, P5, and P31 were aligned with the corresponding aa sequences of all the 16 subtype HAs available in the GenBank. Fig. 4 is a representative of the alignment analysis, showing that P5 is identical to HA of H1 subtype strains. P3 is identical to HA of the H1 subtype, as well as highly identical to HA of the H2, H5, and H6 subtypes. These data are consistent with the specificity analysis by Western blot (Fig. 3A) . Although anti-P31 antibody only recognizes the H1-subtype HA, it is similar to multiple subtypes.