IL-15 increases the frequency of effector memory CD8+ T cells in rhesus monkeys immunized with HIV vaccine

Several studies have suggested that interleukin (IL)-15 is a promising adjuvant that promotes cellular immunity when administered with human immunodeficiency virus (HIV) vaccine. Here we evaluated the effect of IL-15 plasmid on HIV-specific immune responses, especially cellular immunity, in eight rhesus monkeys. These monkeys were immunized three times with HIV DNA vaccine with or without IL-15 plasmid and boosted with recombinant Tiantan strain vaccinia virus-based HIV vaccine (rTV) 22 weeks after the first immunization. Although we did not detect any significant differences in the HIV-specific CD8(+) T-cell response between monkeys with IL-15 coimmunization and monkeys with HIV vaccine alone, our results showed that the frequency of effector CD8(+) memory T cells in the peripheral blood was significantly higher in monkeys with IL-15 coimmunization than those with HIV vaccine alone at almost all of the time points examined. Furthermore, the titers of anti-HIV antibodies were higher in Group T than those in Group C after rTV boosting. These findings in rhesus monkeys suggest that IL-15 may be useful as a cytokine adjuvant for HIV vaccine.