Ex Vivo and in Vivo HIV-1 Latency Reversal by “mukungulu,” a Protein Kinase C-activating African Medicinal Plant Extract

Current HIV latency reversing agents (LRAs) have had limited success in clinic, indicating the need for new strategies that can reactivate and/or eliminate HIV reservoirs. “Mukungulu,” prepared from the bark of Croton megalobotrys Müll. Arg., is traditionally used for HIV/AIDS management in Northern Botswana despite containing an abundance of protein kinase C (PKC)-activating phorbol esters (“namushens”). Here we show that Mukungulu is tolerated in mice at up to 12.5 mg/kg while potently reversing latency in antiretroviral therapy (ART)-suppressed HIV-infected humanized mice at 5 mg/kg. In peripheral blood mononuclear cells (PBMC) and isolated CD4+ T-cells from ART-suppressed people living with HIV-1, 1 µg/mL Mukungulu reverses latency on par with or superior to anti-CD3/CD28 positive control, as measured by HIV gag-p24 protein expression, where the magnitude of HIV reactivation in PBMC corresponds to intact proviral burden levels in CD4+ T-cells. Bioassay-guided fractionation identifies 5 namushen phorbol ester compounds that reactivate HIV expression, yet namushens alone do not match Mukungulu’s activity, suggesting additional enhancing factors. Together, these results identify Mukungulu as a robust natural LRA which may warrant inclusion in future LRA-based HIV cure and ART-free remission efforts. ### Competing Interest Statement C.C., G.W., and P.Z. are current employees of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc. Rahway, NJ, USA and may hold stock in Merck & Co., Inc. Rahway, NJ, USA. All other authors declare no competing interests.