FIG. 6.

Gag-specific CD8⁺ T-cell responses were significantly enhanced by low levels of IFN-γ expression. CD4⁺-T-cell-depleted-splenocytes from animals (six animals per group) immunized with different constructs were stimulated with 15-mer peptide pools spanning SIV Gag, and IFN-γ-secreting cells were identified by using an ELISPOT analysis. A human T-lymphotropic virus Env peptide pool was used as a control and did not give rise to detectable numbers of SFC (result not shown). Bars represent the mean number of SFC for each group, and error bars represent SEM. Statistical analysis was performed using ANOVA. The significant difference (P < 0.05) between dSIV_LRγ-immunized and mock-immunized animals is marked by *, while the significant difference between dSIV_LRγ-immunized and dSIV_R immunized-animals is marked by +.