Atovaquone, a hydroxynaphthoquinone, FDA Pregnancy category C, used for the treatment and prevention of pneumocysits jirovecii pneumonia (PCP), toxoplasmosis, babesiosis and malaria has in-vitro activity against Zika virus (ZIKV). The mechanism of action against plasmodium spp. and other parasites is based in the inhibition of mitochondrial cytochrome bc1 complex which further collapses parasite-mitochondrial membrane potential. But to date, antiviral activity of this drug has not been described.
Vero cells (monkey kidney epithelial cells) were seeded. At 24h of incubation the cells were pre-treated with ribavirin and brequinar (known antiviral drugs) and atovaquone at different concentrations for 1h and then infected with ZIKV Brazilian strain and Ugandan strain, and subsequently treated with drugs again. After incubation for 72h virus antigen Env-protein production was quantified by immunodetection. The concentration of atovaquone that decreased the level of Env-protein production by 50% was calculated by non-linear regression analysis (CC50). Cell viability was measured using the CellTiter 96 aqueous one solution cell proliferation assay (Promega, Madison, WI), according to the manufacturers protocol. Viral infection was rescued adding uracil to Vero cells pre-treated with ribavirin, brequinar and atovaquone. Experiment was repeated with Chikungunya virus (CHIKV).
We found that atovaquone inhibits ZIKV infection in Vero cells at smaller concentration (CC50 = 0.52uM) than those used for parasitic killing. The effect is more prominent in the Brazilian strain when compared to the Ugandan strain. No cytotoxic effect was found in Vero cells up to 15uM; above this concentration atovaquone formed crystals. Uracil rescues ZIKV infection after treatment with atovaquone. Atovaquone also inhibited CHIKV infection in Vero cells.
Atovaquone has antiviral activity against ZIKV likely via depletion of nucleotides blocking pyrimidine biosynthesis. Furthermore, the antiviral effect is applicable to other arboviruses which makes atovaquone a broad-spectrum antiviral drug and a potential attractive candidate for the treatment of ZIKV infection in vulnerable population such pregnant women and children.
K. Stapleford, None