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A cystatin capture enzyme-linked immunosorbent assay (ELISA) using recombinant Fasciola gigantica cathepsin L1 antigen was developed to detect specific immunoglobulin G (IgG) subclass antibodies (IgG1, IgG2, IgG3, and IgG4) and was evaluated for its diagnostic potential for human fasciolosis. In an analysis of the sera of 13 patients infected with F. gigantica, 209 patients with other parasitic infections, 32 cholangiocarcinoma patients, and 42 healthy controls, the IgG4-ELISA gave the highest diagnostic values. The sensitivity, specificity, accuracy, and positive and negative predictive values of this method based on the detection of IgG4 antibody were 100%, 99.3%, 99.3%, 86.7%, and 100%, respectively. The results revealed that restricting the ELISA to the detection of specific IgG4 antibody enhanced the specificity and accuracy for the serodiagnosis of human fasciolosis.

A peptide-based enzyme-linked immunosorbent assay (ELISA) was developed and evaluated for its diagnostic ability to detect human IgG antibodies against Fasciola gigantica cathepsin L1. Two previously identified B-cell epitopes of cathepsin L1 were synthesized as single synthetic peptides (acetyl-DKIDWRESGYVTEVKDQGNC-carboxamide and acetyl-DKIDWRESGYVTELKDQGNC-carboxamide) and their diagnostic potential was evaluated. The peptide-based ELISA was compared with an indirect ELISA with crude excretory-secretory products or with partially purified specific 27-kDa (FG27) antigen from adult F. gigantica. In an analysis of the sera of 13 patients infected with F. gigantica, 212 patients with other parasitic infections, 32 patients with cholangiocarcinoma, and 57 healthy controls, the sensitivity, specificity, accuracy, and positive and negative predictive values of this peptide-based ELISA with both peptides had the same performance and were shown to be 100%, 97.3%, 97.5%, 61.9%, and 100%, respectively. When 4 different ELISAs were compared, the results revealed that the specificity, sensitivity, accuracy, and negative predictive values of all antigens were similar except for the positive predictive value that was highest in the ELISA with the FG27 antigen. These results demonstrated that peptide antigens can be used in the serodiagnosis of human fascioliasis with the additional advantage that they are relatively cheap and easy to produce. This rapid, highly sensitive and specific peptide-ELISA has the potential to be used in future large-scale prevalence surveys throughout Southeast Asia.