IgA and IgG antibodies in serum. (A) Influenza IgA and (B) IgG anti-NP antibodies in serum were analyzed by ELISA at day 0, 21 and 28 PI. White squares, white rhomboids, white triangles and black circles represent mean values from animals belonging to Mock/Mock (□), SwH1N1/Mock (◊), Mock/pH1N1 (Δ) and SwH1N1/pH1N1 (●) groups, respectively. Error bars represent one SD above and below the mean.