FIG. 2.

MVA-HIV-infected cells directly present antigens to HS CTLs. (A) Experimental procedure. APCs were loaded (1 h) with MVA-HIV, UV-inactivated MVA-HIV (at the indicated MOI), or peptide (1 μg/ml) or mock treated and then were washed, seeded for 5 h to allow HIV antigen expression, and cocultured for at least 8 h with HS T cells. T-cell activation was monitored by IFN-γ ELISPOT assay. (B) The CTL clone EM40-F21, specific for Gag, was used to test the capacity of diverse MVA-HIV-infected cell types to present HIV Gag-derived antigens. (C) MVA-HIV-infected APCs present Pol- and Nef-derived epitopes, leading to CTL activation. The CTL lines IV9 and P1, specific for Pol aa 476 to 484 and Nef aa 73 to 82, respectively, were cocultured with autologous B-cell lines, and T-cell activation was monitored by IFN-γ ELISPOT assay. Background IFN-γ production by target cells alone was subtracted and was at least three times lower than that with HS T cells. For each panel, data are means ± SD for triplicates and are representative of at least 2 independent experiments. Percentages of HIV Gag⁺ APCs, determined by flow cytometry at the end of the coculture period, are indicated.