The cytotoxic effect of fowlpox virus on primary human amniotic cell cultures

Summary This report describes a cytotoxic effect of fowlpox virus on human amnion cells. Changes began after 48 hours and were complete within a week following inoculation. The infective property and the cytotoxic property were compared. Suspensions which were cytotoxic nearly always contained at least 10³ PFU/ml. Titers of both properties fell to undetectable levels during 30 days in human amnion cell culture. Titers of both properties were reduced by centrifugation, filtration, heat, ultraviolet light, acid, chloroform, and ether. Exposure to ultraviolet light reduced infectivity more rapidly than cytotoxicity. Treatment with ultrasound regularly increased cytotoxicity titer; infectivity increased to a much smaller and less predictable degree. Cytotoxicity-neutralizing serum antibodies developed in guinea pigs inoculated with fowipox virus. Cytotoxicity was identical in normal and IDUR-treated human amnion cells, but no plaques appeared in IDUR-treated chick embryo cells. The data suggest a mechanism of cytotoxicity that requires contact between virus and cell that does not require assembly of infectious viral particles.This investigation was supported by research grant AI-01023 and by training grant AI-177 from the National Institute of Allergy and Infectious Diseases, U.S. Public Health Service.