The Effect Of Intranasal Immunization With STAg And ESA On Vertical Transmission Of Toxoplasma Gondii In Mice

Objective The primary aim of this study was to establish the mouse model of vertical transmission by orally infected tachyzoites of Toxoplasma gondii RH strain.The next aim was to study the effects of intranasal immunization with STAg on vertical transmission of Toxoplasrna gondii.To study the effects of intranasal immunization with the combination of STAg and ESA on vertical transmission of Toxoplasma gondii.The aim of this study was providing the experimental evidence for developmemting the vaccine of vertical transmission of Toxoplasma gondii.Methods This study included three parts.The first part:Fifty-four pregnant mice were randomly divided into 6 groups(9 in each group),at the day 8 of gestation,the mice were orally infected with 0,1 000,2 000,4 000,8 000,16 000 tachyzoites of T.gondii RH strain, respectively.At the day 8 of gestation,the mice were killed and their uteri were anatomized for observing survival rate of embryos and the Toxoplasma antigene in pregnant mice livers, placentas and fetuses were detected by ELISA.The second part:One hundred and thirty 5-to 6-week-old virgins BALB/c mice were randomly divided into the PBS group(60 mice per group)and the STAg group(70 mice per group).In the STAg groups mice were immunized with 20ug STAg per mouse,while the PBS groups were immunized with 20μl PBS solution,twice at an internal of two weeks.The two virgins immunized mice were housed with one male after the last immunization.According to the different time of pregnancy,the mice were divided into three groups again.At the day 8 of gestation(the 11rd days,thel7th days and the 23th days respectively after last immunization), the mice were orally infected with 8 000 tachyzoites of T.gondii RH strain.At the day 18 of gestation,the mice were killed and computed the infectious rate and average live embryo rate. The thymus and spleen of pregnant mice were weighed.The specific sIgA antibodies in intestinal washes and the Toxoplasma antigene in livers,placentas and fetuses of the pregnant mice were detected by ELISA.The third part:BALB/c mice were randomly divided into four groups,10 mice per group. The first,second and third groups were immunized intranasally with 20μg STAg,20μgESA and 20μg combination of 10μg STAg and 10μg ESA per mouce,respectively.The forth group was selected as a control group(PBS-immunized).All mice were immunized intranasally twice at interval of 14 days.Females were mated with males in the 13th day after the last immunization. The mice were orally infected with 8000 tachyzoites of T.gondii RH strain at the day 8 of gestation.At the day 18 of gestation,the mice were killed and computed the infectious rate and average live embryo rate and tachyzoites of their spleens.The specific slgA antibodies in intestinal washes and Serum IgG and the Toxoplasma antigene in livers,placentas and fetuses of the pregnant mice were detected by ELISA.Results After the pregnant mice wre infected the different dose of tachyzoite,the mortality of the pregnant mice and the infectious rate of the placentas and embryos were a rise of the does of infected tachyzoite.The mice of 1 000 and 2 000 groups were not infected;the infectious rate of embryos in 4 000 group was lower(5.13%)and that of 16 000 group was the highest(20.00%);In a word,the survival rate and infectious rate of placentas and embryos of 8 000 group mice were higher than those of other groups.To study the effects of intranasal immunization with STAg at different time on vertical transmission of Toxoplasma gondii.The mortality and infectious rate of each group had no significant change.The average live embryo rate of the 3th group of STAg were higher than the group of PBS(P＜0.05).The weight of mice spleen had no significant changes.The thymic weight of 3th group of STAg mice had been decreasing after the last immunization(P＜0.05). The sIgA antibodies in the pregnant mice intestinal washes of the 3th group of STAg were higher than the others besides the 2th group of STAg(P＜0.05).With the a rise of the time of immunizition the infectious rate of the pregnant mice of STAg and the placentas and embryos were decreasing,but the average live embryo rate of the pregnant mice were rising.The placentas and embryos infectious rate of 3th group of STAg mice were higher than those of other groups.To study the effect of intranasal immunization with the combination of STAg and ESA on vertical transmission of Toxoplasma gondii.The mortality and infectious rate of each group had no significant change.The average live embryo rate of PBS were lower than the STAg and ESA group(P＜0.01).Compared with PBS group,the tachyzoite load in spleens in the immunized groups were significantly lower(P＜0.01).The level of sIgA in intestinal washes of the combination of STAg and ESA group and ESA group were higher than the PBS group(P＜0.01).The level of IgG in serum showed increasing tendence in the PBS,STAg,ESA and the combination of STAg and ESA group in order.The infectious rate of embryos of the combination of STAg and ESA group was lower than those of other groups.Conclusion Tachyzoites of 8 000 oral infection mice is a suitable dose which can be applied to establish the mouse model of vertical transmission.The mice were intranasally immunized with 20ug STAg twice at an internal of two weeks.After the 23th day of the last immunization,the mice were infected tachyzoites of 8 000 orally which can be decreased the infectious rate of pregnant mice and the placentas and embryos.The intransally immunity effect of the combination STAg and ESA was better than STAg or ESA alone.The BALB/c mice were intranasally immunized with 20ug the combination of STAg and ESA(1:1)twice at an internal of 2 weeks.After the 23th day of the last immunization,the mice were infected tachyzoites of 8 000 orally which can be decreased the infectious rate of pregnant mice and the placentas and embryos.