The Toxic Effect of Vaccinia Virus on Leucocytes In Vitro

Suspensions of cells obtained from the peritoneal exudate of the white mouse and the cell population developing from the growth of such cells on glass were found to be rapidly destroyed by concentrated suspensions of vaccinia virus. A destructive effect of vaccinia virus on suspensions of human white blood cells was also observed. The cytopathic changes are not caused by virus multiplication but by a toxic principle which could not be separated from the virus particles by centrifugation. Virus preparations made noninfective by irradiation with ultraviolet light still possessed toxic qualities. It is suggested that the characteristic leucopenia observed in smallpox and vaccinia infection in man may be caused by a mechanism similar to that of the destruction of white blood cells by vaccinia virus demonstrated in vitro.