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