FIG 1.

Epitope-specific IFN-γ production by seasonal influenza virus-specific CD8⁺ T cells after stimulation with peptide-loaded BLCLs. Polyclonal CD8⁺ T cells were isolated from PBMCs in vitro stimulated with sH3N2, sH1N1, or pH1N1, as indicated. No pH1N1 in vitro stimulation was performed for subject 6, since those PBMCs were isolated in 2008, prior to the 2009 pandemic outbreak. The polyclonal CD8⁺ T cells were subsequently stimulated with peptide-loaded and untreated HLA class I-matched BLCLs. Stimulation with homologous peptides is indicated by black bars, stimulation with H7N9 variant peptides is indicated by gray bars, and control cells without peptide are indicated by white bars. The number of IFN-γ-producing cells per 10,000 polyclonal CD8⁺ T cells was determined by ELISpot assay. The results represent the averages of triplicate wells. Peptides were selected based on the variation in the H7N9 sequence and their compatibility with the HLA haplotypes of our study subjects. The error bars indicate standard deviations of results from the triplicate wells.