PARAMYOSIN OF ECHINOCOCCUS-GRANULOSUS - CDNA SEQUENCE AND CHARACTERIZATION OF A TEGUMENTAL ANTIGEN

A lambda ZAPII cDNA library of Echinococcus granulosus larvae was expr essed in Escherichia coli SURE cells. Screening of the library with a rabbit antiserum raised against total larval antigen yielded several i mmunoreactive clones. For analysis of the nucleotide sequence, in vivo excision into pBlueskript was carried out and the 3' end of the clone d insert was sequenced. Three of these clones exhibited identical nucl eotide sequences, suggesting expression of identical genes. The comple te nucleotide sequence of the largest clone, EG36, with a 3.4-kb inser t was determined, presenting an open reading frame of 2.59 kb. The pre dicted amino acid sequence showed 71.4% identity to the Schistosoma ma nsoni paramyosin and a significant homology to a 17 amino-acid peptide sequence from antigen B of Taenia solium. From these data we conclude that EG36 is the paramyosin of E. granulosus. For protein purificatio n, the coding sequence of the cDNA was amplified by polymerase chain r eaction and ligated in frame into the expression vector pGEX-3X. Affin ity-chromatography-purified GST fusion protein was used to induce a po lyclonal rabbit antiserum. Immunoblot analysis revealed the expression of a 97-kDa protein by the E. coli clone and that of a protein with a similar molecular weight in protoscolices from E. granulosus and E. m ultilocularis as well as in E. granulosus cyst fluid. Immunofluorescen ce studies showed that EG36 was localized throughout the tegument of E . granulosus and E. multilocularis larvae. Sera from patients sufferin g from echinococcosis, schistosomiasis, and neurocysticercosis reacted with the purified fusion protein when tested in an enzyme-linked immu nosorbent assay.