Induction of specific T-cell responses in HTLV-1–infected rhesus monkeys (Macaca mulatta) by rVVs. (A-B) The antigen-specific T-cell response in the monkeys designated (A) MM557 and (B) MM558 was measured in CD4- or CD8-depleted PBMCs by IFN-γ ELISPOT assay. Cells were stimulated with Tax or HBZ pooled peptides (P1-P4). (C-E) IFN-γ and TNF-α production by Tax- or HBZ-specific CD8⁺ T cells induced by (C) rVV. For IFN-γ and TNF-α production, PBMCs from (D) MM557 and (E) MM558 were isolated 39 weeks after vaccination. Cells were preactivated with pooled peptides and restimulated with peptide-pulsed auto PBMCs, which were labeled with a tracer dye to discriminate between responder and stimulator cells. Cytokine production in CD8⁺ T cells was measured in the tracer dye–negative population. The percentage of cytokine-producing cells is shown in the dot plots. Phorbol myristate acetate (PMA) and ionomycin (P/I) were used as a positive control of the stimulus.