A Study of Cross-Reactivity Between Recombinant EPC1 Antigen of Echinococcus granulosus in Serum from Patients with Confirmed Cystic Echinococcosis Infection and Other Parasitic Infections

A standardized test for the serodiagnosis of cystic echinococcosis (CE) remains an important challenge because of the problems in specificity and sensitivity of the available commercial kits and lack of proper evaluation of antigen. Using appropriate sources of antigenic material is crucial in improvement of the serological methods such as enzyme-linked immunosorbent assay (ELISA). This study was conducted to evaluate the performance of protein named Echinococcus protoscolex calcium binding protein EPC1 for the detection of antibodies in sera from patients with CE. Expressed and purified recombinant protein EPC1 (rEPC1) was used as antigen in ELISA method. Characterization of the rEPC1 antigen was evaluated using the serum of 25 patients with both surgical and imaging confirmed CE and 25 healthy donors as negative controls. Also, a panel of sera including chronic toxoplasmosis (IgG positive), strongyloidosis, fascioliasis, toxocariasis, and kala azar were used and patients with related parasites were confirmed by medical laboratories or clinically by research centers using microscopy or specific ELISA. rEPC1 showed relatively promising performance in total IgG ELISA for the detection of antibodies in sera from the negative controls, and the cut off value 0.4 units of optical density at 490 nm was calculated for ELISA. In this study, sensitivity of 100%, specificity of 93.7, positive predictive value of 92.6%, and negative predictive value of 100% were calculated for rEPC1. On the other hand, commercial ELISA kit based on the native antigen B of Echinococcus granulosus had sensitivity of 96.2% and specificity of 96.8%. No significant difference was found for sensitivity or specificity between the rEPC1 and commercial kit. However, rEPC1 may be a valuable antigen for diagnosis of human CE.