The protein kinase C inhibitor H‐7 (2–20 μM) inhibited dose‐dependently the infectivity of the vesicular stomatitis virus on cultured human fibroblasts. Electron microscopy showed that H‐7 inhibited the viral entry. H‐7 also inhibited the infectivity of four other enveloped viruses, herpes simplex I, turkey herpes, vaccinia and Sindbis. Similar results were obtained using staurosporine (2.5 nM), tamoxifen (40 μM), phloretin (140 μM). or W‐7 (40 μM). However, the infectivity of non‐enveloped viruses (e.g. poliomyelitis I) was not inhibited by H‐7. These results show that protein kinase C is critically involved in the infectivity ofenveloped viruses, most probably at the level of viral entry (receptor‐mediated endocytosis).
