Comparison of the Utility of Recombinant B8/2 Subunit of the Antigen B, Native Antigen, and a Commercial ELISA Kit in the Diagnosis of Human Cystic Echinococcosis

ABSTRACT

Background: Cystic echinococcosis (CE) is a helminthic disease caused by the larval form of Echinococcus granulosus. In the present study, the B8/2 subunit of antigen B (AgB) of E. granulosus was expressed in E. coli host and then applied in a diagnostic ELISA set up. Methods: The DNA sequence of AgB8/2 subunit from E. granulosus was extracted from the GenBank and codon-optimized according to E. coli codon usage. The target sequence was cloned in an expression vector (pGEX-4T-1). The produced antigen was used in an ELISA system, and its performance for the diagnosis of human hydatid cyst was evaluated, using sera from CE and non-CE patients, along with the sera from healthy subjects. Moreover, the diagnostic value of the recombinant protein was compared with native AgB, as well as with a commercial kit. Results: Antibodies to hydatid cyst were detected in 27 out of 30 patients corresponding to a sensitivity of 90% (95% CI 73-98%). Cross-reaction with sera of non-CE subjects was seen in two cases resulted in a specificity of 93.5% (95% CI 82-98%) for the test. A sensitivity of 87% and specificity of 90% were found for the native form of the antigen, while the ELISA commercial kit had a sensitivity of 97% and specificity of 95%. Conclusion: Our data show that rEgAgB8/2 is an appropriate source of antigen for the serological diagnosis of human hydatid cyst. Co-expression of the rEgAgB/2 along with other subunits of AgB may enhance the performances of these antigens for the serodiagnosis of human CE.