FIG 4.

Dominant p11C epitope-specific IFN-γ expression by CD8⁺ T lymphocytes. (A) After BCG/rBCG priming immunization, only a few of the MHC class I allele Mamu-A*01-expressing rhesus macaques showed IFN-γ ELISpot responses upon stimulation with the CD8⁺ T lymphocyte-specific p11C peptide, in contrast to the very strong IFN-γ expression by CD8⁺ T lymphocytes in plasmid DNA-SIVgag-pol-nef-primed macaques. The data conform to a strong bias of the mycobacterial vaccines toward CD4⁺ T lymphocyte responses but indicate bias toward CD8 responses in Mamu-A*01-positive monkeys after 3 repeated rDNA vaccinations. (B) Following the rNYVAC-SIVgag-pol boost, IFN-γ expression upon p11C peptide stimulation showed a pattern of responses similar to those measured after SIV Gag pooled peptide stimulation. The results indicate that the boosting viral vector overrides the bias established at prime and changes the bias toward CD8-leaning responses (n = 5 for each of the 7 groups). Lines connect responses from individual animals over the time course of the study. Arrows indicate immunization time points.