Abstract
BackgroundToxoplasma gondii is an opportunistic protozoan apicomplexan and obligate intracellular parasite that infects a wide range of animals and humans. Rhoptry proteins 5 (ROP5), ROP16, ROP18 and dense granules 15 (GRA15) are the important effectors secreted by T. gondii which link to the strain virulence for mice and modulate the host’s response to the parasite. Little has been known about these molecules as well as GRA3 in type Chinese 1 strains that show polymorphism among strains of archetypical genotypes. This study examined the genetic diversity of these effectors and its correlated virulence in mice among T. gondii isolates from China.ResultsTwenty-one isolates from stray cats were detected, of which 15 belong to Chinese 1, and 6 to ToxoDB #205. Wh6 isolate, a Chinese 1 strain, has an avirulent phenotype. PCR-RFLP results of ROP5 and ROP18 presented few variations among the strains. Genotyping of GRA15 and ROP16 revealed that all the strains belong to type II allele except Xz7 which carries type I allele. ROP16 amino acid alignment at 503 locus demonstrated that 17 isolates are featured as type I or type III (ROP16I/III), and the other 4 as type II (ROP16II). The strains investigated may be divided into four groups based on GRA3 amino acid alignment, and all isolates of type Chinese 1 belong to the μ-1 allele except Wh6 which is identical to type II strain.ConclusionsPCR-RFLP and sequence alignment analyses of ROP5, ROP16, ROP18, GRA3, and GRA15 in T. gondii revealed that strains with the same genotype may have variations in some of their key genes. GRA3 variation exhibited by Wh6 strain may be associated with the difference in phenotype and pathogenesis.
Highlights
Toxoplasma gondii is an opportunistic protozoan apicomplexan and obligate intracellular parasite that infects a wide range of animals and humans
Genotyping of T. gondii isolates at ROP18, Rhoptry proteins 5 (ROP5), ROP16 and granules 15 (GRA15) loci by PCR-RFLP method We genotyped the ROP18, ROP5, ROP16 and GRA15 loci of 21 isolates collected from animals and compared the results with the reference strains
In order to confirm the allele of ROP16 and GRA15, we analyzed the polymorphism of GRA15 and ROP16 through PCR-RFLP, and the results showed that all of the isolates contained the allele 2 GRA15 and ROP16 except for the Xz7 strain
Summary
Toxoplasma gondii is an opportunistic protozoan apicomplexan and obligate intracellular parasite that infects a wide range of animals and humans. Rhoptry proteins 5 (ROP5), ROP16, ROP18 and dense granules 15 (GRA15) are the important effectors secreted by T. gondii which link to the strain virulence for mice and modulate the host’s response to the parasite. This study examined the genetic diversity of these effectors and its correlated virulence in mice among T. gondii isolates from China. Toxoplasma gondii is an obligate intracellular protozoon that can infect a broad spectrum of vertebrate hosts including humans. Genotyping results of the strains collected from human and animals around the world show a rich genetic diversity [7] which points to the fact that the distribution of T. gondii genotypes varies greatly with geographical locations [8]. More than 200 genotypes have been recorded in the T
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