1a.Objectives (from AD-416):
Define molecular basis of toxoplasmosis.
1b.Approach (from AD-416):
T. gondii strains of different genetic background will be isolated and cultured.
Toxoplasma gondii is a widespread parasite of animals that causes zoonotic infections in humans. Previous studies have revealed a strongly clonal population structure in North America and Europe, while strains from South America are genetically separate and more diverse. However, the composition within North America has been questioned by recent descriptions of genetically more variable strains from this region. Genetic crosses conducted under this aim have demonstrated that differences between the highly virulent type I strain and intermediate virulent type II are independent of ROP18, but are due to allelic differences in ROP5, although the molecular basis for this difference was not known. To expand the genetic backgrounds where virulence traits can be studied, we have initiated crosses between members of the virulent type IV or VI lineages and intermediate virulent type II strain. Genetic crosses are being conducted using standard methods of co-infecting cats with tagged lines of the parasite followed by isolation of recombinant progeny in cell culture. These studies will address whether ROP kinases also contribute to acute virulence in other lineages, or whether this trait is due to other genes.