Acute virulence in mice is associated with markers on chromosome VIII in Toxoplasma gondii

Abstract

Toxoplasma gondii has an unusual population structure consisting of three widely distributed clonal lineages. Acute virulence in mice is strictly observed in type I strains, indicating that a genetic determinant(s) unique to this lineage controls acute pathogenesis. We have analyzed several naturally occurring recombinant strains of T. gondii that carry allele 1 at the SAG1 locus; this allele is characteristic of the type I strains and was previously found to be 100% correlated with the acute virulence phenotype. Recombinant strains G622-M and ROD both had a predominantly type III genotype, with the significant exception of allele 1 at the SAG1 locus. Although these two strains had virtually identical multilocus genotypes, they differed in their virulence in mice. Strain ROD was virulent whereas strain G622-M was nonvirulent, thus demonstrating that the presence of

Targeted Disruption of theGRA2Locus inToxoplasma gondiiDecreases Acute Virulence in Mice

“…Seropositive survivors were sacrificed 6 weeks after injection, and one half of the brain was homogenized and inoculated into a single female outbred CD1 mouse. After 6 to 8 days, the peritoneal fluid was harvested and inoculated onto HFF monolayers to recover parasites in culture (22). The other half of the brain was fixed in 4% formalin in PBS, rinsed, dehydrated, and embedded in paraffin.…”

“…Serial sections were rehydrated, stained with either a rabbit serum recognizing the bradyzoitespecific antigen BAG5 (dilution of 1:1,000; provided by L. Weiss, Albert Einstein College of Medicine, New York, N.Y.) or the rabbit serum anti-SAG1 (dilution of 1:1,000; provided by L. H. Kasper, Dartmouth Medical School, Hanover, N.H.), detected by using a Vectastain Elite ABC kit (Vector Laboratories, Burlingame, Calif.), and counterstained with hematoxylin. Sections of a mouse brain chronically infected with the type III strain CEP (22) were used as positive controls for the presence of cysts. Slides were mounted in PBS-glycerol (50/50) and examined on a Zeiss Axioscope.…”

Protozoal coinfection in horses with equine protozoal myeloencephalitis in the eastern United States

“…Future work should include a larger population of horses from additional geographical regions.Diagnostic tests for T. gondii have not been validated for use with horse samples 31. Therefore, Western blot was used to detect antibodies against T. gondii, which is consistent with prior studies investigating T. gondii infection in several other species, including humans, ruminants, and mice [22][23][24][25][26]. Western blot is not a quantitative test, which prevents its use for establishing an end-point titer.…”

Assays for monitoringToxoplasma gondiiinfectivity in the laboratory mouse

“…Type III strains are relatively common in animals in North America and yet they are rarely encountered in human cases of toxoplasmosis (4, 19, 20). Type III strains are highly avirulent in laboratory mice, with high challenge doses leading to low levels of lethal infection (21). The Type III strain CTG (aka CEP) has been used to study sexual phase transmission in the cat and to develop genetic mapping strategies for T. gondii (22, 23).…”