Effects of thyroid-stimulating hormone on the replicative cycle of vesicular stomatitis virus in primary cultured sheep thyroid cells

Sheep thyroid cells in primary culture are highly sensitive to thyroid stim ulating hormone (TSH). We infected thyroid cells with vesicular stomatitis virus (VSV) in the course of studies on cell polarity, and we found that TS H augmented the speed of the replicative cycle of VSV but did not affect th e final yield of the virus. Three hours post-infection, at a multiplicity o f infection of 10, the Virus was detected in the cell layer of the cultures incubated with TSH but not in those without TSH. Five hours post-infection , there was a 100-fold increase in the medium in the yield of VSV and a 60- fold increase in the cell-associated virus in the TSH-treated cells compare d with the cells without TSH. We found that the early stages of infection w ere accelerated by TSH. This effect appears to be due, at least in part, to increased processing in the lysosomes, thus allowing deposition of the tra nscriptionally-active nucleocapsid into the cytoplasm. These studies show t hat TSH is critically involved in the infectivity of VSV and that by manipu lating cell culture conditions, an increased rate of virus production can b e achieved. (C) Societe francaise de biochimie et biologie moleculaire / El sevier, Paris.