Abstract
The rate of polykaryocyte formation was used to study the effects of thyroxine on the adsorption and penetration of the herpes simplex virus (HSV) into HEp-2 cells. Cells pretreated with 3 to 24 hours with thyroid extract adsorbed HSV and affected its penetration more rapidly than untreated cells. The thyroid hormone affects the rate of adsorption and penetration; it does not alter the titer of the virus. The effect of the thyroid hormone is exactly opposite of the effect of parathyroid hormone.