Objective To study the protective immunity and antibody(IgG,IgG1 and IgG2a)response against adult and larva infection of T.spiralis Korean isolate in rats.Methods Fony-six rats were randomly divided into 7 groups.Group A(A1,A2,10 rats)was used for the determination of protective efficacy from adult stage infection,group B (B1,B2,14 rats)was for the protective efficacy from muscle larva stage infection,group C(C1,C2,17 rats)was for challenge control,and group D(5 rats)served as normal control.Rats in groups A,B and C were infected with 1000 T.spiralis muscle larvae,and the infected rats were treated with flubendazole(20 mg/ks,10 d)at day 7(A1,A2) and at day 30(B1,B2).Rats in groups A and B were re-infected with 500 T.spiralis muscle larvae at day 10 after treatment.Rats in groups A1 and B1 were killed at day 7 and day 30 to inspect the reduction of adult worms in the intestines.Rats in groups A2 and B2 were killed at day 30 to detect the reduction of muscle larvae in diaphragms.Rats in groups C and D were killed at the same time,and all rats were bled at the same time.Specific anti-Trichinella IgG,IsG1 and IgG2a were detected by ELISA.Results Adult stage infection induced protective efficacy by 100% against adult stage and by 99.96% against larva stage.Larval stage infection induced protective efficacy by 99.92% against adult stage and 99.89% against muscle larvae.Anti-muscle stage larval ES Ag(IgG 3.0,IgG1 2.2,IgG2a 0.8)and anti-adult crude Ag antibodies(IgG 1.9,IgG1 0.8,IgG2a 0.3) significantly increased in the muscle larval stage infection compared to normal control(IgG 0.5,IgG1 0.1,IgG2a 0.1)and adult stage infection(IgG 0.5,IgG1 0.09,IgG2a 0.09) (P<0.01).Higher specific IgG1 antibody(IgG1 2.2) in larva stage infection was shown than specific IgG2a antibody response(IgG2a 0.8)(P<0.01).Conclusion Protective immunity against both adult and larva worms has been induced from adult and muscle larva stage infections of T.spiralis.

[Objective] To study the synergic effect of praziquantel (PZQ) and host acquired immunity on Clonorchis sinensis. [Methods] Acquired immunity to C. sinensis was induced by immunization with crude adult worm antigen (AW Ag) and excretory-secretory antigen (ES Ag) or infection with C. sinensis metacercariae. The effect was assessed by the worm reduction rate compared with the control groups after challenge infection with 50 metacercariae and treated orally with a subcurative dose of praziquantel (50 mg/kg). Significant test was performed by analysis of variance (ANOVA) and Nparl way Kruskal-Wallis test. All calculations were performed by PC-SAS system. [Results] 1. PZQ was more effective against C. sinensis larvae than against adult worms in the control (P＜0. 001), ES Ag (P＜0.01) or crude AW Ag immunization group (P＜0. 001). 2. As compared with the control, the worm reduction rate after challenge infection was significantly higher (P＜0. 001) in ES Ag immunized group (35.60%) and metacercaria infection group (97.5 % ) and less in crude AW Ag group (23.4 %). The PZQ efficacy was significantly enhanced in ES Ag immunized group. [Conclusion] The efficacy of PZQ against C. sinensis could be synergically enhanced in rats by inducing host acquired immunity.