Zinc salts inactivate clinical isolates of herpes simplex virus in vitro

Using a standard plaque assay and clinical isolates of herpes simplex virus (HSV), we have tested the ability of zinc salts to inactivate HSV, Virus w as treated by incubation at 37 degrees C with zinc salts in morpholinepropa ne-sulfonic acid-buffered culture medium and was then diluted and plated on to CV-1 cells for detection and quantitation of remaining infectious virus. Of 10 randomly chosen clinical isolates (five HSV type 1 [HSV-1] isolates and five HSV-2 isolates), seven were inactivated > 98% by treatment in vitr o with 50 mM zinc gluconate for 2 h and nine were inactivated >97% by treat ment with zinc lactate, The effect was concentration dependent. With an HSV -1 isolate, 50 mM zinc gluconate or zinc lactate caused 100% inactivation, 15 mM caused 98 to 99% inactivation, and 5 mM caused 63 to 86% inactivation . With an HSV-2 isolate, 50 and 15 mM zinc gluconate caused 30% inactivatio n and 5 and 1 mM caused less than 9% inactivation, whereas 50 and 15 mM zin c lactate caused greater than 92% inactivation and 5 and 1 mM caused 37 and 26% inactivation, respectively. The ability of the zinc salts to inactivat e HSV was not related to pH in the pH range of 6.1 to 7.6 since inactivatio n by zinc gluconate or zinc lactate in that pH range was 99.7 to 100% with a 2-h treatment with 50 mM zinc salt. Short (5-min) treatments of selected isolates with zinc gluconate, zinc lactate, zinc acetate, or zinc sulfate y ielded inactivation rates of 0 to 55%.