The pattern of antibody response to Sj23HD in mice and rabbits infected with Schistosoma japonicum and its immunodiagnostic value

Objectives To investigate the pattern of antibody response to a large hydrophilic domain of a 23-ku membrane protein in mice and rabbits infected with Schistosoma japonicum and determine the value of the recombinant fusion protein Sj23HD-HSA in diagnosing schistosomiasis japonica and evaluating its treatments.Methods Animal models were established using mice and rabbits infected with schistosome cercariae.The sera of mice and rabbits infected with S.japonicum were collected at different times before infection,during infection,and after treatment with PZQ.To observe the pattern of antibody response to Sj23HD in mice and rabbits infected with S.japonicum and evaluate the potential therapeutic effectiveness of a fusion protein in treating schistosomiasis,an indirect enzyme-linked immunosorbent assay(ELISA) was used to determine the dynamics of antibody response to Sj23HD at different times before infection,during infection,and after treatment with PZQ.To evaluate the immunodiagnostic value of recombinant Sj23HD-HSA,ELISA was performed on 132 serum specimens from patients with schistosomiasis,30 serum specimens from patients with clonorchiasis,10 serum specimens from patients with paragonimiasis,and 80 serum specimens from healthy individuals.As a control,antibodies(IgG) to soluble egg antigens(SEA) in sera were detected using indirect ELISA.Results The antibody response to Sj23HD increased as the duration of infection increased.It continued to rise and peaked 2-4 wks after PZQ treatment.It then gradually declined.The level of antibody response in some mice and rabbits reached the negative cut-off value 16 wks after PZQ treatment,but the extent of the decline in antibody response differed in different animals.There was a slight decline in the antibody response to SEA in treated mice and rabbits,but there was no decline in the antibody response to Sj23HD and SEA in untreated mice and rabbits.The 132 serum specimens from patients with schistosomiasis tested positive for antibody IgG against Sj23HD-HSA at a rate of 88.64% and against SEA at a rate of 97.73%.The 10 serum specimens from patients with paragonimiasis had a cross-reaction rate of antibody IgG against Sj23HD-HSA of 50% or against SEA of 90%.The 30 serum specimens from patients with clonorchiasis had a cross-reaction rate of antibody IgG against Sj23HD-HSA of 0% or against SEA of 16.7%.The 80 serum specimens from healthy individuals resulted in no false positives for antibody IgG against both Sj23HD-HSA and SEA.Conclusion Antibody response to the Sj23HD protein in mice and rabbits infected with S.japonicum was shorted-lived.Antibodies involved in this short-lived antibody response to Sj23HD-HSA have the potential to diagnose schistosomiasis japonica and evaluate the effectiveness of treatments.Compared to SEA,recombinant Sj23HD-HSA is a more specific way to diagnose schistosomiasis,but care must still be taken to distinguish schistosomiasis from other parasitic diseases in patients from areas where paragonimiasis is endemic.