Figure 4.

Rhesus macaque CD4⁺ T cells infected with the mutant SIV_mac239 Nef TW9 virus fail to elicit IFN-γ production in a WT SIV Nef IW9-specific CD8⁺ T-cell clone. CD4⁺ T cells infected with either WT SIV_mac239 (Nef IW9) or the mutant Nef TW9 virus were used as APC to stimulate an autologous SIV Nef IW9-specific CTL clone at a CD8⁺:CD4⁺ T cell ratio of 1:1. To allow for optimal numbers of infected target cells, day 8 post infection CD4⁺ T cells were used as stimulator cells. The frequency of IFN-γ-expressing CTL was determined by flow cytometry. An autologous SIV Gag CM9-specific CTL clone was included as a positive control.