A Comparision Study Of Toxoplasma Strain Virulence And Pathogenecity Of Type Chinese 1 Prevalent In China

Background Toxoplasma gondii is a kind of obligate intracellular parasite,which could infect almost all nucleated cells in vertebrate hosts,including human beings.T.gondii infection could cause servere lesions in hosts,which may lead to animal death.The target organs of T.gondii is eyes,brain,heart,liver and lymph nodes.The world-wide prevalent strains of T.gondii are Type I,Type II,Type III and Type12.In north america and erop,most of T.gondii isolated from human and animals are Type II.Currently,virulence and pathogenesis of typical strains mentioned above have been studied intensively,domestrating that virulence of Type I is significantly higher than that of other two strains.However,little information is available about the virulence of China prevalent strain(Wh3 and Wh6).Objectives:Through in vivo experiments,to study the virulence and pathogenesis of different strains of T.gondii(Wh3,Wh6,RH,PRU),to measure the pathological lesions caused by these parasites.Methods1.Tachyzoites passaging,harvesting and freezing;2.In experimental set A,125 mice were randomly divided into 5 groups and infected with given parasites.The clinical manifestations and survival rates were detected for virulence deternimation.3.In experimental set B,100 mice were divided into 5 groups and infected with parasites as described in set A.In different time points,mice were killed and their liver,lung,brain,lymph nodes were obtained for HE staining.4.Parasite burden was estimated by detecting DNA of T.gondii in all samples.5.The transcriptional level of IL-12,INF-?,IL-4 and IL-10 were evaluated by RT-PCR.Results1.The results of acute infection experiments showed that the virulence of RH was slightly higher than that of Wh3,while the virulence of Wh6 and PRU was significantly lower than that of RH and Wh3.2.Histochemically,infection of T.gondii could lead to pathological lesions of different organs.And the virulence results was similar to that of acute infection experiments.3.Application q RT-polymerase chain reaction(PCR)to detect lung,liver,brain,testis each viscera arched bug charge quantity of RH close to Wh3 > Wh6 > PRU.Through four groups of independent sample t-test worm load data shows RH group and Wh3 group,the PRU and Wh6 worm load without statistical significance;RH group with PRU group and the worm load Wh6 group were statistically significant,Wh3 with PRU group and worm load Wh6 group were statistically significant.4.According to the existing q RT-polymerase chain reaction(PCR)to detect the spleen cell cytokines data,draw Wh6 group with PRU INF-? and IL-4 was statistically difference,PRU above Wh6 group;Wh6 group with PRU IL-10 no statistical significance.Conclusions1.From acute infection experiments,we found that the survival rates of mice infected with Wh3 or Wh6 parasites were much lower.Wh3 infection caused more severepathological lesions in mouse liver,brain,lung,testis and lymph nodes.2.The virulence of RH was slightly higher than that of Wh3,while the virulence of Wh6 and PRU was significantly lower than that of RH and Wh3.