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The cytotoxicity of ultraviolet light irradiated reovirus

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Title:The cytotoxicity of ultraviolet light irradiated reovirus
Authors:Subasinghe, Don Henry Ariyadasa
Ultraviolet radiation
Date Issued:1971
Abstract:When reovirus type 2 was exposed to ultraviolet light (UV) for 2-5 minutes, it acquired a cytotoxic property to HeLa cells. Maximal toxicity was attained after 10 minutes irradiation and decreased to undetectable levels by 60 minutes. The incident photo energy dose at maximum cytotoxicity level was 6 x 10^7 ergs/cm^2. The production of UV-induced cytotoxicity was temperature dependent with a maximum at 37°C. The toxic factor was found to be associated with the virus proteins since it was demonstrated that the "empty" particles of reovirus exposed to ultraviolet light were also toxic to HeLa cells. In addition, studies with virus protein components produced by selective chemical degradation of the mature reovirus with urea showed that the cytotoxicity was associated with the outer capsid proteins. Virions in which the RNA polymerase enzyme was activated by brief heat treatment (70°C, 30 sec) were not toxic to HeLa cells. Extracted RNA exposed to UV-irradiation was also found not to be cytotoxic. Examination of the cytotoxic virus particle indicated no detectable alterations in the following properties: adsorption rates to HeLa cell monolayers, hemagglutination of human "0" erythrocytes, interferon inducing ability, RNA transcriptase activity, virus architecture, buoyant density in Cesium chloride, capsid protein components, viral double-stranded RNA and adenine-rich RNA. In contrast, upon continued irradiation for 60 minutes the loss of cytotoxic property was accompanied by the following: loss of viral hemagglutination, reduction in interferon inducing ability, derangement of the virus architecture, increase in buoyant density, change in electrophoretic mobility of the capsid protein components and alteration in the viral double-stranded RNA. The effect of pre-infecting HeLa cells with viable reovirus before treatment with an equivalent multiplicity of UV-irradiated virus was determined. Viral antigen synthesis and the production of infectious virus was not interfered with to any significant level. Furthermore, the induction of cytotoxicity was not interfered with by pre-infecting the cells with homologous or heterologous viable reovirus. Pre-treatment of mouse L cell cultures with interferon at concentrations which inhibited reovirus yields by 80-90% and vesicular stomatitis virus yields in excess of 99% failed to prevent the reovirus induced cytotoxicity. The toxic property of UV-irradiated reovirus was not dependent on the cell system in which the virus was passed, but was a specific property of the virus itself. All three serotypes of reovirus acquired this toxic property on exposure to ultraviolet light. On examination of the sensitivity of different cell types to the UV-irradiated reovirus induced toxicity, it was found that the established cell lines in general were more sensitive than the primary cell cultures.
Thesis (Ph. D.)--University of Hawaii, 1971.
Bibliography: leaves [159]-171.
ix, 171 l illus., tables
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Appears in Collections: Ph.D. - Microbiology

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