FIG. 5.

Functional recall memory of Gag-specific CD8⁺ T cells in response to IL-15 plasmid injection. A longitudinal study using the procedure described in the legend to Fig. 2 was performed to monitor macaque AL49 from week 28 to week 45 p.i. At this time, the Gag-specific CD8⁺ T-cell responses became repeatedly undetectable. We then injected 5 mg of IL-15 plasmid DNA intramuscularly and monitored the weekly IR monitoring up to 49 weeks p.i. (A) The proportion of cells producing IFN-γ (contour plot, upper number) and proliferating (CFSE dilution; contour plot, lower number) in response to Gag peptides is presented at the time of undetectable response (W45 p.i.) and 2 weeks after plasmid IL-15 injection (W47 p.i.). Backgrounds obtained with medium after 5 days [medium(5d)] and Gag after 6 h [Gag(6h)] were subtracted from the reported values shown in Results. (B) Summary of the frequency of proliferating-only (CFSE low; top) as well as proliferating and IFN-γ-producing (CFSE low IFN-γ⁺; bottom) Gag-specific CD8⁺ T cells detected from week 28 to week 49 p.i.