Novel ex vivo approaches distinguish effective and ineffective single agents for reversing HIV-1 latency in vivo

HIV-1 persists in a latent reservoir (LR) despite antiretroviral therapy (ART)1–5. This reservoir is the major barrier to HIV-1 eradication6,7. Current approaches to purging the LR involve pharmacologic induction of HIV-1 transcription and subsequent killing of infected cells by cytolytic T lymphocytes (CTL) or viral cytopathic effects8–10. Agents that reverse latency without activating T cells have been identified using in vitro models of latency. However, their effects on latently infected cells from infected individuals remain largely unknown. Using a novel ex vivo assay, we demonstrate that none of the latency reversing agents (LRAs) tested induced outgrowth of HIV-1 from the LR of patients on ART. Using a novel RT-qPCR assay specific for all HIV-1 mRNAs, we demonstrate that LRAs that do not cause T cell activation do not induce significant increases in intracellular HIV-1 mRNA in patient cells; only the PKC agonist bryostatin-1 caused substantial increases. These findings demonstrate that current in vitro models do not fully recapitulate mechanisms governing HIV-1 latency in vivo. Further, our data indicate that non-activating LRAs are unlikely to drive the elimination of the LR in vivo when administered individually. HIV-1 cure is hindered by viral persistence in a small fraction (~1/106) of resting CD4+