FIG. 7.

IFN-γ production by CD8⁺ and CD4⁺ T cells following a priming immunization with rSmeg-gp120 or DNA-gp120 and a boosting immunization with rAd-gp140. Mice were immunized either once (×1) or twice (×2), 10 weeks apart, with rSmeg-gp120 (5 × 10⁷ CFU) or DNA-gp120 (50 μg). Twenty weeks after the first immunization or 10 weeks after the second immunization, the mice were inoculated with 10⁶ particles of rAd-gp140. Splenocytes were harvested from individual mice 8 weeks after the immunization with rAd-gp140. IFN-γ production was evaluated by ELISPOT assay using total splenocytes incubated with p18 peptide (1 μg/ml) (A) or by CD8⁺ T-cell-depleted splenocytes stimulated with a peptide pool consisting of 158 overlapping 15-mer peptides spanning the HIV-1 HXB2/BaL Env protein at a concentration of 1 μg/ml (B). Data are presented as the mean numbers of antigen-specific spots per 10⁶ spleen cells ± SE, with five mice per group. *, P < 0.01 (one immunization versus two immunizations).