The combination of romidepsin and bryostatin has

The combination of romidepsin and bryostatin-1 has been shown to be one of the best inducers of latent HIV-1 in primary CD4+ T purchase AM251 (Laird et al., 2015). However, bryostatin-1 has been showed to be involved in the modulation of NFkB and NFAT (Williams et al., 2004) and romidepsin is known to affect the function of NK cells and CD8+ T cells (Kelly-Sell et al., 2012; Jones et al., 2014). Other HDAC inhibitors have furthermore been known to induce Treg cells in vitro (Akimova et al., 2010; Tao et al., 2007). The immunomodulatory activity of the two drug classes thought to be most promising in cure efforts therefore needs to be further studied in the context of CD8+ T cell elimination of reactivated latently infected CD4+ T cells. In this study, we sought to determine the ability of HIV-specific CD8+ T cells from patients with progressive HIV-1 disease on ART (chronic progressors) to kill HIV-infected CD4+ T cells after treatment with LRAs. To elucidate the contribution of the drug treatments the HIV-specific response, suppression of infection was examined with elite suppressor CD8+ T cells that had been pre-treated with different LRAs, including an HDAC inhibitor, a bromodomain-containing protein 4 inhibitor, and multiple PKC agonists. Finally, we examined the mechanisms that may have contributed to the effects of drug treatment on CD8+ T cell function. Our results have implications for the HIV-1 cure agenda.
Methods
Results
Discussion Current HIV-1 cure strategies seek to eliminate the latent reservoir by specifically activating HIV-1 so the immune system can clear the latently infected cells. The most promising latency reactivating agent (LRA) regimens in vitro thus far appear to be combinations of HDAC inhibitors (HDACi) and PKC agonists (Laird et al., 2015). However, some of these drugs have previously been suggested to have immunomodulatory effects (Jones et al., 2014; reviewed in Akimova et al., 2012, and Remoli et al., 2012). In this study, we confirm that the combination of bryostatin-1 and romidepsin is effective in reversing latency, however we found that even following stimulation with high concentrations of IL-2 and Gag and Nef consensus peptides, CD8+ T cells from fully suppressed chronic progressors were unable to reduce the amount of HIV-1 mRNA associated with CD4+ T cells or prevent release of virions from these cells in the context of bryostatin-1 and romidepsin treatment. One limitation of our study is that we did not measure actual viral protein production or antigen presentation following latency reversal. It is possible that some of the mRNA we measured is defective and did not lead to the synthesis of functional proteins that could be recognized by CD8+ T cells. Another possibility is that the effects of the LRAs may be short lived in vivo since HIV-specific CD8+ T cells from patients treated with vorinostat (Sung et al., 2015) and romidepsin (Søgaard et al., 2015) appeared to be functional in ex vivo studies, but even a short term effect could be important for viral clearance. Another limitation is the relatively small number of patients studied in this manuscript. In a prior study, autologous ex vivo expanded virus-specific cytototoxic T lymphocytes, but not unexpanded CD8+ T cells, from HIV infected patients were able to significantly reduce the number of latently infected cells following reversal with vorinostat (Sung et al., 2015). The discrepancy between that study and our findings could potentially be explained by the fact that vorinostat has much less of an effect of on CD8+ T cells than did romidepsin, bryostatin-1 and the combination of the 2 drugs. Chronic progressors\' primary CD8+ T cells are generally not effective in controlling HIV-1 replication (reviewed in Migueles and Connors, 2015), which may also partially account for observed results. In order to determine other potential causes, we examined the effect of four separate LRAs alone and in combination on the HIV-specific CD8+ T cell response of elite suppressors.