Recall antibody responses in lung and serum.

<p>Lung IgG (A) and IgA (B), and serum IgG (C) and IgA (D) antibody responses to A/California/04/2009 virus were determined before (week 6.5 post immunization) and after challenge (day 4 post challenge) with the homologous virus A/California/04/2009. Lung and serum samples before and after challenge were collected at the same time (n = 6) and analyzed under the same assay condition (week 6.5 post-vaccination). Lung IgA (B) before and after challenge: P<0.05. Serum IgG (C) and IgA (D) responses before and after challenge from the A/California/04/2009 virus challenge: P<0.001. Low and moderate naïve backgrounds were observed in the serum and lung samples respectively and these values have been subtracted from the immune samples.