In vitro antiviral activity of polyoxotungstate (PM-19) and other polyoxometalates against herpes simplex virus

Polyoxotungstates with Keggin-type structure were found to demonstrate marked antiherpetic activity. K7[TiW10PO40].6H2O (PM-19) caused a decrease in plaque formation by several strains of herpes simplex virus (HSV) type 1, including acyclovir-resistant (thymidine kinase-negative) strains, at concentrations which were not toxic to the host cells. The 50% plaque-inhibiting concentration (EC50) for the different strains was between 20 and 50 micrograms/ml. Single-cycle HSV growth was also inhibited by PM-19. PM-19 inhibited viral DNA synthesis in HSV-infected cells at a concentration of 5 micrograms/ml but did not exhibit a virucidal effect, and pretreatment of the host cells with PM-19 did not provide resistance to herpes infection. Yet, virus adsorption to the cells was markedly affected at PM-19 concentrations higher than 25 micrograms/ml. PM-19 was also effective against human cytomegalovirus, but not against adenoviruses and varicella-zoster virus, although it did delay the development of the cytopathic effect of these viruses.