Lysergol exerts potent antiviral activity against the emerging Oropouche virus in vitro.

Oropouche virus (OROV) has caused a new outbreak, with thousands of cases of febrile disease in South and Central America, including regions where the virus was not detected before. Oropouche fever is a neglected mosquito-borne disease that still lacks options for antiviral treatment. We developed a high-throughput screening phenotypic assay using human hepatocyte-derived HuH-7.0 cells to screen over 7700 compounds against OROV infection. We identified 13 hit compounds that were protective against OROV-induced cytopathic effect in cell culture, of which 3 were confirmed: lysergol, amiloride hydrochloride, and pyridostatin TFA, with EC50 values below 2 μM. Orthogonal assays indicate that both lysergol and pyridostatin present antiviral activity against OROV in HuH-7.0 and T24 cell lines, but lysergol is far more potent, causing up to a 100,000-fold reduction in viral load in the low micromolar range. Mechanistic studies indicate that the antiviral effect of lysergol affects early stages of viral replication, and that lysergol is also active against a recently isolated OROV strain. In conclusion, our phenotypical screening campaign led to the identification of a first-in-class compound with potent antiviral activity against the emerging OROV in cell culture. We conclude that high-throughput screening assays can be implemented in response to the emergence of arboviruses and accelerate the discovery of candidate treatments.