SEQUENCE AND IMMUNOGENICITY OF THE TAENIA-SAGINATA HOMOLOG OF THE MAJOR SURFACE-ANTIGEN OF ECHINOCOCCUS SPP

A clone (R-Tso18) was isolated from a Taenia saginata encosphere cDNA library by screening with sera from rabbits immunised with oncosphere extract. It contained a full-length cDNA sequence of 1893 bp with an o pen reading frame of 1680 bp, corresponding to 559 amino acids with a deduced molecular mass of 65.173 kDa and an isoelectric point of 6.08. The R-Tso18 protein showed 80-84% nucleotide identity with the major protoscolex surface antigens of Echinococcus multilocularis (EM10) and E. granulosus (EG10). Preliminary immunogenicity studies employing th e radio-labeled R-Tso18 protein in immune co-precipitation assays indi cated sere-positivity for T. saginata-infected calf sera (6/13), T. so lium cysticercosis human (7/22) and pig (2/2) sera and E. multilocular is (6/10)- and E. granulosus (1/12)-infected human sera, whereas other helminth-infection sera were negative. As immuno-precipitation is a r elatively insensitive assay, it was concluded that further studies on the diagnostic potential of the purified recombinant R-Tso18 antigen, or its peptides, are merited.