Thioredoxin peroxidase from Echinococcus granulosus: a candidate to extend the antigenic panel for the immunodiagnosis of human cystic echinococcosis

The currently available tests for the diagnosis of cystic echinococcosis (CE), enzyme-linked immunosorbent assay (ELISA), and immunoblotting (IB) lack sensitivity and specificity, and antigen panels need standardizing. By screening an Echinococcus granulosus cDNA library with IgG1 from patients with CE, we identified E. granulosus thioredoxin peroxidase (EgTPx). Although IB and ELISA achieved the same specificity (92%), ELISA showed higher sensitivity than IB (83% versus 42%) in determining total immunoglobulin G (IgG) specific to EgTPx in CE sera. The percentage of total IgG- and IgG1-positive sera in ELISA was equally distributed in patients with active, transitional, and inactive disease. Conversely, the percentages of IgG4-positive sera were significantly higher in sera from patients with active than inactive disease (P = 0.03). Our data suggest that adding this highly specific recombinant antigen to the standard diagnostic panel of antigens used in ELISA would increase diagnostic sensitivity. Antibodies specific to EgTPx are of potential interest in the host–parasite relationship.