Effect of drugs which inhibit cholesterol synthesis on syncytia formation in vero cells infected with measles virus.

We found that nontoxic doses of two inhibitors of cholesterol synthesis, namely W-7 and cerulenin, delayed syncytia formation in vero cells infected with measles virus. To correlate syncytia formation and lipidic membrane changes induced by these drugs, we labelled cell lipids with [14C]acetate. Measles virus infection increased the incorporation of radiolabel into fatty acids, triacylglycerol, cholesterol ester, and decreased its incorporation into cholesterol and 1,2-diacylglycerol. The ratios phosphatidylcholine/sphingomyelin and free cholesterol/lanosterol-dihydrolanosterol also decreased during the infection. W-7 and cerulenin greatly altered lipid metabolism. Both decreased the phosphatidylcholine to sphingomyelin and the cholesterol to lanosterol-dihydrolanosterol ratios. Z-D-Phe-L-Phe-L-Gly, a tripeptide which corresponds to the N-terminal sequence of the viral fusion protein (responsible for syncytia formation) and which inhibits virus-induced cell fusion without affecting virus synthesis also perturbed cholesterol metabolism. The tripeptide reversed the phosphatidylcholine to sphingomyelin ratio in infected cells. At non-toxic doses, W-7 inhibited the synthesis of infectious virus. Cerulenin which inhibited strongly the lipid synthesis did not. Finally, the well characterized inhibitors of cholesterol synthesis, mevinolin, ketoconazole and miconazole were shown to inhibit the syncytia formation. We conclude that the inhibition of syncytia by W-7 and cerulenin is associated with their capacity to alter the cholesterol metabolism, whereas the antiviral effect of W-7 does not seem related to this capacity.