Latently infected CD4 T cells represent a major barrier to HIV-1 cure efforts. The current “shock and kill” strategy relies upon the use of latency reactivating agents (LRAs) to selectively induce production of HIV-1 mRNA and proteins in resting CD4 T cells to make them visible to the adaptive immune system. Previous work has shown that treating primary latently infected cells with combinations of LRAs is more effective than single drug treatments. One such combination is bryostatin and romidepsin, the latter of which has further been shown to induce reactivation in vivo. However, romidepsin and other HDAC inhibitors have been associated with impaired CTL responses. Thus, we sought to examine the stimulated, primary effector CD8 T cell response of cART-treated HIV+ individuals to latently-infected CD4 T cells cultured with the LRAs bryostatin and romidepsin (B/R).
Resting, CD4 T cells from 6 cART-treated HIV+ chronic progressors were treated with the combination B/R to reactivate latently infected cells. To determine the ability of the CD8 effector response to identify and kill these cells, primary CD8 T cells that had been stimulated with overlapping Gag and Nef peptides and IL-2 for seven days were added to culture at 6 hours post-stimulation. Cell-associated and supernatant HIV mRNA from 24 hours post-stimulation was measured via qPCR to determine the efficacy of the CD8 effector response.
B/R treatment of primary, resting CD4 T cells resulted in a 12.3±3.0 fold increase in cell-associated HIV mRNA and a 30.4±10.7 fold increase in supernatant HIV mRNA. Despite the stimulation of the primary CD8 T cells, there was no significant difference in either cell-associated or supernatant HIV mRNA when B/R-treated CD4 T cells were incubated with CTL in 3 patients. However a 2-fold reduction in cell-associated mRNA was seen in the other 3 patients.
While the combined treatment of latently infected CD4 T cells with romidepsin and bryostatin induces upregulation of HIV mRNA, primary CD8 T cells stimulated with Nef and Gag peptides in the presence of high levels of IL-2 were unable to eliminate the reactivated cells in the majority of chronic progresses on ART. However effective responses were seen in several patients. The results suggest that in some cases, effective priming of the cytotoxic T lymphocyte responses may lead to elimination of reactivated latently infected CD4+ T cells.