Enhanced Production of Virus‐Inhibiting Factor (Interferon) in Human Diploid Cells by Ultraviolet Irradiation and Temperature Shift‐Down after Stimulation with Newcastle Disease Virus

Abstract

The production of the virus-inhibiting factor or interferon (IF) was highest in cells incubated at 37 C after inoculation with Newcastle disease (ND) virus and decreased as the incubation temperature was lowered. Shift-down of incubation temperature to 32 C or 34 C after incubation at 37 C for 4-7 hr enhanced IF production in cell cultures stimulated with ND virus, as compared. with cultures incubated continuously at 37 C. Shift-down to 32 C after incubation at 37 C for 6 hr. was optimal for this enhancement of IF yield. Enhanced IF production was also observed in cell cultures irradiated by ultraviolet light 4-7 hr after stimulation with ND virus.Recent results of clinical studies (7) and considerable experimental evidence (4) have produced potent IF in human diploid cells by the superinduction process, in which IF production with synthetic double-stranded RNA, polyinosinate-polycytidylate, is enhanced by the use of metabolic inhibitors (3, 9, 10).In the present study we have investigated the production of IF in human diploid cells by stimulation with Newcastle disease (ND) virus to define more optimal conditions for IF preparation. The production of IF in these cells stimulated with ND virus was enhanced by shift-down of the incubation temperature to 32 C or 34 C after incubation at 37 C for 4-7 hr, as compared with cultures incubated continuously at 37 C. Enhanced IF production was also observed in cell cultures irradiated by ultraviolet light 4-7 hr after stimulation with ND virus. This paper presents these observations. 907

Production of interferon in human diploid cells at different population doubling levels

“…Mter adsorption at 37 ° C for 1 hour, the inoeulum was removed, and the cultures were washed, fed with 10 ml of MEM, and incubated at 37 ° C for 23 hours in a COa incubator. The ND virus used was the I-3 strain grown in the Mlantoic cavity of 11-day-old chicken embryos (7).…”

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