Cellular immune responses after vaccination. (A) SIVmne Gag, HIV-1 Tat Oyi and SIVsmE543-3 Nef-specific, IFN-γ-secreting cells (spot-forming units (SFU) / 106 PBMC) as determined by ELISPOT assay at different time points. (B & C) Ex vivo proliferation of CD4+ and CD8+ T cells after stimulation with SIVmne Gag, or HIV-1 Tat Oyi peptides. The assay was performed after the final immunization, i.e., on the day of the first SHIV-C challenge. The RM ROb-12 (boxed) remained aviremic after all heterologous SHIV-C challenges. *, Mamu A*001+ RMs.