Application of a recombinant Echinococcus multilocularis antigen in an enzyme-linked immunosorbent assay for immunodiagnosis of human alveolar echinococcosis.

A highly antigenic polypeptide fragment of the recombinant Echinococcus multilocularis antigen II/3 was produced in Escherichia coli and purified for application in enzyme-linked immunosorbent assay (ELISA). The antigen II/3-encoding 1.0 kb DNA sequence was reduced by sonication into smaller DNA fragments which were subsequently cloned into lambda gt11. Three clones could be isolated from the sublibrary, all synthesizing a recombinant antigen as a stable beta-galactosidase fusion protein. In a further step, the 0.6-kb insert from one positive clone was subcloned into the plasmid pAR 3038, which directed efficient synthesis of the antigen fused to only 11 amino acids from the N-terminus of the phage T7 major capsid protein. The plasmid-encoded antigen (antigen II/3-10) was purified from a bacterial cell extract and then tested in an ELISA. Using sera from 88 patients with an E. multilocularis-infection, a high diagnostic sensitivity of 90% was demonstrated. Investigation of sera from 220 patients with various helminthic infections showed a specificity of 99%, suggesting the suitability of the antigen II/3-10 as an immunodiagnostic tool.