To investigate the immune protective effect induced by superoxide dismutase(SOD)of the Toxocara canis(T.canis)in mice,in this experiment,seventy-five Kunming mice of six-week-age were randomly divided into 5 groups for the immune protection experiment,the mice were subcutaneously immunized with 50,75 and 125 mg/L Tc-SOD(0.1 mL)on days 0,14 and 28,re-spectively.In the blank group,mice did not receive any treatment,while the PBS group was injected with equal amounts of sterility PBS.A total of three immunizations and each immunization interval of 14 days.14 days after the third immunization,the 3 000 infected worm eggs were given orally in all groups.Before each immunization,14 days after the third immunization,and after the T.canis attack on the 7th day,the blood was sampled from the tail vein and sera were separated,while the IgG levels in serum were detected by indirect ELISA.The proliferation ability of splenic lympho-cytes and the mRNA expression levels of Th1(IFN-γ,IL-2)and Th2 cytokines(IL-4,IL-10)were analyzed with CCK-8 and qRT-PCR.The larvae reduction rates were calculated on the 7th day after the T.canis attack,and the pathological changes in the livers and lungs were observed using H&E staining.The results showed that compared with the PBS group,the serum IgG antibody levels increased with the frequency and duration of Tc-SOD immunization.It remained at a high level af-ter the T.canis attack,and the differences were very significant(P＜0.001).The mRNA expres-sion levels of IFN-γ,IL-2,IL-4,and IL-10 were dramatically increased(P＜0.01),while IL-4 andIL-10 were significantly higher than IFN-γ and IL-2 on the 14th day after the third immunization(P＜0.05),showing the Th2 type predominant immune response.And induce the proliferation of spleen lymphocytes in vitro(P＜0.01).The reduction rates of larvae of 50,75 and 125 mg/L Tc-SOD immune groups were 18.7％,24.9％and 37.6％,respectively,with significant differences in the 125 mg/L Tc-SOD group(P＜0.05),and had better immune protection effect.Moreover,the H&E staining results indicated that three Tc-SOD immune groups reduce the inflammatory cell infiltration(neutrophils,eosinophils,and macrophages)and hemorrhagic lesions in the livers and lungs of mice.The above results indicated that Tc-SOD could induce humoral and cellular immune responses in mice,mainly Th2 immune response,and provide immune protection against T.canis infection.

To investigate the immune protective effect induced by superoxide dismutase(SOD)of the Toxocara canis(T.canis)in mice,in this experiment,seventy-five Kunming mice of six-week-age were randomly divided into 5 groups for the immune protection experiment,the mice were subcutaneously immunized with 50,75 and 125 mg/L Tc-SOD(0.1 mL)on days 0,14 and 28,re-spectively.In the blank group,mice did not receive any treatment,while the PBS group was injected with equal amounts of sterility PBS.A total of three immunizations and each immunization interval of 14 days.14 days after the third immunization,the 3 000 infected worm eggs were given orally in all groups.Before each immunization,14 days after the third immunization,and after the T.canis attack on the 7th day,the blood was sampled from the tail vein and sera were separated,while the IgG levels in serum were detected by indirect ELISA.The proliferation ability of splenic lympho-cytes and the mRNA expression levels of Th1(IFN-γ,IL-2)and Th2 cytokines(IL-4,IL-10)were analyzed with CCK-8 and qRT-PCR.The larvae reduction rates were calculated on the 7th day after the T.canis attack,and the pathological changes in the livers and lungs were observed using H&E staining.The results showed that compared with the PBS group,the serum IgG antibody levels increased with the frequency and duration of Tc-SOD immunization.It remained at a high level af-ter the T.canis attack,and the differences were very significant(P＜0.001).The mRNA expres-sion levels of IFN-γ,IL-2,IL-4,and IL-10 were dramatically increased(P＜0.01),while IL-4 andIL-10 were significantly higher than IFN-γ and IL-2 on the 14th day after the third immunization(P＜0.05),showing the Th2 type predominant immune response.And induce the proliferation of spleen lymphocytes in vitro(P＜0.01).The reduction rates of larvae of 50,75 and 125 mg/L Tc-SOD immune groups were 18.7％,24.9％and 37.6％,respectively,with significant differences in the 125 mg/L Tc-SOD group(P＜0.05),and had better immune protection effect.Moreover,the H&E staining results indicated that three Tc-SOD immune groups reduce the inflammatory cell infiltration(neutrophils,eosinophils,and macrophages)and hemorrhagic lesions in the livers and lungs of mice.The above results indicated that Tc-SOD could induce humoral and cellular immune responses in mice,mainly Th2 immune response,and provide immune protection against T.canis infection.