FIG 3.

Intranasal NLP:NP boost elicits a higher frequency of NP-specific CD4 T cells in the lung than does an LAIV boost. (A to F) Thirty days postimmunization with LAIV, CD4 T cell responses were assayed in lung, mLN, and spleen via IFN-γ (A to C) and IL-2 (D to F) cytokine ELISpot to characterize the immune response prior to intranasal boost with NLP:NP. At 10 days post intranasal immunization with NLP:NP, the extent of CD4 T cell boosting in lung (A and D), mLN (B and E), and spleen (C and F) was quantified by IL-2 and IFN-γ cytokine ELISpot. Results are presented as the mean number of cytokine-producing spots per million CD4 T cells with the standard deviation shown. The mean is representative of three to five independent experiments of five pooled mice each.