Despite the success of antiretroviral therapy (ART), eradication of HIV-1 from brain reservoirs remains elusive. HIV-1 brain reservoirs include perivascular macrophages that are behind the blood-brain barrier and difficult to access by ART. Macrophages express transcription factor FOXO3a and the TNF superfamily cytokine TRAIL, which are known to target HIV-1-infected macrophages for viral suppression. ONC201 is a novel and potent FOXO3a activator capable of inducing TRAIL. It can cross the blood-brain barrier, and has shown an antitumor effect in clinical trials. We hypothesized that activation of FOXO3a/TRAIL by ONC201 will reduce the size of HIV-1 brain reservoirs. Using primary human monocyte-derived macrophages, we demonstrated that ONC201 dose-dependently decreased HIV-1 replication levels as determined by HIV-1 reverse transcriptase activity assay and Western blots for p24. Consistent with data on HIV-1 replication, ONC201 also reduced integrated HIV-1 DNA in infected macrophages in two-step Alu-based nested PCR. In addition, the antiviral effect of ONC201 is applicable to different natural HIV strains and to lymphocytes, microglia and latently infected cell line. A combination of ONC201 and AZT achieved a longer and synergistic viral suppression in HIV-1 infected macrophages. The anti-HIV-1 effect of ONC201 was further validated in vivo in NOD/scid-IL-2Rgcnull mice. After intracranial injection of HIV-1-infected macrophages into the basal ganglia, we treated the mice daily with ONC201 through intraperitoneal injection for 6 days. ONC201 significantly decreased p24 levels in both the macrophages and the brain tissues, suggesting that ONC201 suppresses HIV-1 in vivo. As for the mechanisms, ONC201 treatment activated FOXO3a and induced TRAIL expression in macrophages while blocking TRAIL or knockdown of FOXO3a with siRNA reversed ONC201-mediated HIV-1 suppression, suggesting that ONC201 inhibits HIV-1 through FOXO3a and TRAIL. Furthermore, the antiviral effect of ONC201 is associated with apoptosis and autophagy. Based on these in vitro and in vivo studies, ONC201 can be a promising drug candidate to combat persistent HIV-1 infection in the brain reservoirs
