FIG. 2.

In vitro recognition of escape variant viruses by epitope-specific CD8⁺ T-cell lines. We mixed polyclonal epitope-specific cell lines with CD4⁺ T cells infected with either WT SIVmac239 or SIVmac239 with the indicated mutation(s) in the epitope being tested. We then performed an intracellular cytokine staining assay to identify cells secreting IFN-γ and TNF-α. The percentages of CD4⁻ CD8⁺ cells that were IFN-γ and/or TNF-α positive following stimulation are displayed. We intracellularly stained infected target cells for the expression of Gag p27 in parallel to ensure that comparable percentages were infected with the different viruses (data not shown). Results are representative of at least two independent experiments per epitope, using cell lines cultured from at least two different animals. Mutations that we selected for use in the challenge virus are indicated with arrows.