Reduction of herpes simplex virus-type 2 plaque formation by urea

The effect of urea on plaque formation by herpes simplex virus type 2 (HSV-2) was examined in two systems at concentrations within or approximating the range found in human urine. Approximately 7--10 mg urea/ml, added 2, 4, or 8 hours after infection, reduced plaque formation by 50% in African green monkey kidney cells. The growth of this system was affected slightly by continuous treatment with urea at 7--10 mg/ml. Plaque formation was reduced in the monkey kidney system, albeit diminishingly, even after addition of urea 12 hours after infection. In the human lung fibroblast system, urea at 10 mg/ml reduced plaque numbers by 50% but depressed the growth of cells completely.