The pathogenesis of Vaccinia virus toxicity. I. The role of virus-platelet interaction

When mice are injected intravenously with a large dose of vaccinia virus, prepared in the Ehrlich ascites carcinoma of the mouse, there is a precipitous loss of plasma fibrinogen and blood platelets. Death occurs usually within 24 hours. A specific role of the virus in this toxic syndrome can be demonstrated when heparin is employed to circumvent intravascular coagulation and fibrinogen loss. Heparin does not prevent a profound thrombocytopenia from occurring, but it modifies the rate of platelet loss. Toxicity is prevented when heparinized virus preparations are pretreated with beta-propiolactone or specific antibody, although a mild thrombocytopenia occurs. Thrombocytopenia does not occur in mice injected with heparinized material prepared from uninfected tumors. These studies indicate that the basic mechanism of vaccinia virus toxicity is an early interaction between infectious virus and blood platelets, with marked thrombocytopenia and consequential pathophysiologic changes.