Genotyping and virulence analysis of Toxoplasma gondii isolates from a dead human fetus and dead pigs in Jiangsu province, Eastern China

Abstract

AbstractToxoplasma gondiiis an obligate intracellular parasite with worldwide distribution. Virulence ofT.gondiiis a multigenic trait. Genetic and virulence data forT.gondiiisolates from humans and animals in China have been reported. However, almost all biological materials used for genotyping ofT.gondiifrom humans and pigs were DNA samples prepared from tissues, andT. gondiistrains used for virulence analysis were isolated mainly from cats. In this study, one isolate from a dead human fetus was identified as type I (ToxoDB #10) while the two isolates from dead pigs were type Chinese I (ToxoDB #9) with PCR-restriction fragment length polymorphism using 10 markers (SAG1,SAG2,SAG3,BTUB,GRA6,c22–8,c29–2,L358,PK1and Apico). Three isolates were comfirmed as virulent strains in mice. By cloning and sequences analysis, all isolates contained aPvuII restriction site (572–577 bp) in the KHB fragment and five tandem repeats in the 5′ UTR region ofSAG1, which were associated withT.gondiivirulence. The type Chinese I isolates contained two deletions of 15 and 3 bp at positions 635 to 649 and 658 to 660 in theGRA6, which were correlated with genotype, but not with virulence. To our knowledge, this is the first report on the systematic analysis of murine virulence of type Chinese I strain from pigs, and the associations of sequences of the KHB fragment andSAG1with virulence of type Chinese I strain. The Chinese I genotype was more closely related to type II strains.