Protection against influenza virus rechallenge appears to be independent of magnitude of virus-specific CD8+ T cell response.

<p>A) C57BL/6 mice were primed with either X31-GP33 i.n. or LCMV Armstrong i.n. These mice, as well as a naïve control group, were rechallenged with 3 LD₅₀ influenza PR8-GP33 virus on day 30+ following primary infection. Weight loss after rechallenge and lung function (as measured by pulse oximetry) were assessed. Mice were sacrificed on day 0, 4, 6, and 9 post rechallenge and viral titers were determined in the lungs. Data are representative of 9 mice per group with three mice sacrificed at each time point for viral load determination. B) The lung, spleen and BAL were collected on day 6 to assess the influenza virus-specific CD8+ T cell response. Following isolation, cells were stimulated using peptide pools from the influenza proteins HA, NA, NS1/2, PA, PB, NP, as well as the LCMV GP33 peptide. Intracellular staining (ICS) for IFNγin the lung, BAL, and spleen assessed the total virus-specific CD8+ T cell response. Mice were anaesthetized using avertin. <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003207#s2" target="_blank">Results</a> are representative of two independent experiments.