Intranasal immunization with ESA and STAg protects mice against Toxoplasma gondii infection

Objective To study the protective immunity against Toxoplasma gondii induced by intranasal immunization with excreted/secreted antigens(ESA)and soluble tachyzoite antigen(STAg)in mice.Methods Sixty-four BALB/c mice were randomly divided into four groups.The control group was in tranasally treated with 20μl PBS permouse and the test groups treated with 20μg ESA in vitro(ESAv),ESA from peritoneal fluids(ESAm)or STAg permouse,respectively,twice at an internal of 2 weeks.Eightmice of each group were killed on day 14 th after the last immunization.Serum IgG and slgA in intestinal washes were detected by ELISA.Eightmice were challenged intragastrically with 1×10⁴ tachyzoites permouse on day 14 th after the last immunization.Mice were killed on the 30 th day after the challenge,the tachyzoites in their spleens and brains were counted.Results Mice in ESA from peritoneal fluids group appeared slight piloerection and lassitude,while mice in other groups were healthy.The level of serum IgG in all antigen groups was higher than that of PBS group on 14 day after immunization(P<0.001).The levels of slgA in ESAv group(P<0.05),ESAm group(P<0.001) and STAg group(P<0.001)was higher than that of PBS group,and the levels in ESAm group(P<0.001)and STAg group(P<0.05)were higher than that of ESAv group.The tachyzoite load in spleens and brains in all antigen groups was significantly lower than that of PBS group(P<0.05).Compared with PBS group,The tachyzoite load in spleens of ESAv group,ESAm group and STAg groupd decreased with a percentages of 49.2%,49.52% and 51.94% in the spleens,respectively,and 46.83%,50.81% and 51.18% in the brains,respectively.Conclusion Intranasal immunization with ESA in vitro,ESA from peritoneal fluids or STAg can effectively induce immune responses against Toxoplasma gondii.ESA from peritoneal fluids has toxic side effect on mice.ESA in vitro and STAg may be attractive candidate for Toxop lasma gondii vaccine.