title: Killing of Toxoplasma gondii oocysts by irradiation and protective immunity induced by vaccination with irradiated oocysts.
abstract: Toxoplasma gondii oocysts are highly resistant to environmental influences. To study the effect of alpha-irradiation on the viability of T. gondii oocysts, 1 million sporulated oocysts of the VEG strain were irradiated to absorbed doses of 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, or 0.50 kGy at 5 C with a 137Cs gamma-irradiation source. Treated oocysts were bioassayed for viable T. gondii in mice. Viable T. gondii was not found in brains of mice 2 mo after oral inoculation with oocysts irradiated at levels > or = 0.25 kGy. Therefore, alpha-irradiation is an effective means of killing T. gondii oocysts. Mice inoculated orally with oocysts irradiated at 0.20 and 0.40 kGy were partially protected when challenged orally with lethal doses of nonirradiated oocysts.
authors.affiliation: Parasite Biology and Epidemiology Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705-2350, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Dubey
authors.forename: M C
authors.initials: MC
authors.lastname: Jenkins
authors.forename: D W
authors.initials: DW
authors.lastname: Thayer
authors.forename: O C
authors.initials: OC
authors.lastname: Kwok
authors.forename: S K
authors.initials: SK
authors.lastname: Shen
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000096:biosynthesis; D001681:Biological Assay; D002415:Cats; D004307:Dose-Response Relationship, Radiation; D005260:Female; D051379:Mice; D014122:Toxoplasma / Q000276:immunology* / Q000472:pathogenicity / Q000528:radiation effects*; D014123:Toxoplasmosis / Q000517:prevention & control*; D014611:Vaccination; D014774:Virulence
chemical_list: D000913:Antibodies, Protozoan