Comparative analysis of full-length antigen II/3 fromEchinococcus multilocularisandE. granulosus

Abstract

SUMMARY: The recombinantEchinococcus multilocularisantigen ll/3–10 is one of the most promising tools for immunodiagnosis of alveolar echinococcosis in human patients. Its nucleic acid sequence represents a part of theE. multilocularisgene encoding the metacestode antigen II/3, the former being basically present and expressed in bothE. multilocularisandE. granulosus. Most (94%) patients with alveolar echinococcosis respond to infection with a marked anti-II/3–10 IgG synthesis; in contrast, most of the cystic echinococcosis patients do not, for some reason, recognize the recombinant antigen. We tackled this problem by generating cDNA derived from bothE. granulosusandE. multilocularisfull length II/3 genes, performed by reverse transcription and PCR amplification. Sequence analysis revealed a very high degree of conservation of the primary sequence of the antigen II/3 in bothEchinococcusspecies. cDNA fragments were subcloned and expressed inE. colias fusion proteins withSchistosoma japonicumglutathione S-transferase. Recombinant proteins were affinity purified and comparatively assessed by ELISA with respect to antibody-binding characteristics. Sera from patients suffering from cystic echinococcosis showed no significant differences in reactivity with the antigens derived from eitherE. multilocularisorE. granulosus. Therefore, parameters other than some minor differences in the primary sequence seem to be responsible for the lack of antigen II/3 recognition in cystic echinococcosis.NoteNucleotide sequence data reported in this paper have been submitted to the GenBank^®data base with the accession numbers U05573 and U05574.