COMPARATIVE-ANALYSIS OF FULL-LENGTH ANTIGEN II 3 FROM ECHINOCOCCUS-MULTILOCULARIS AND E-GRANULOSUS/

The recombinant Echinococcus multilocularis antigen II/3-10 is one of the most promising tools for immunodiagnosis of alveolar echinococcosi s in human patients. Its nucleic acid sequence represents a part of th e E. multilocularis gene encoding the metacestode antigen II/3, the fo rmer being basically present and expressed in both E. multilocularis a nd E. granulosus. Most (94%) patients with alveolar echinococcosis res pond to infection with a marked anti-II/3-10 IgG synthesis; in contras t, most of the cystic echinococcosis patients do not, for some reason, recognize the recombinant antigen. We tackled this problem by generat ing cDNA. derived from both E. granulosus and E. multilocularis full l ength II/3 genes, performed by reverse transcription and PCR amplifica tion. Sequence analysis revealed a very high degree of conservation of the primary sequence of the antigen II/3 in both Echinococcus species . cDNA fragments were subcloned and expressed in E. coli as fusion pro teins with Schistosoma japonicum glutathione S-transferase. Recombinan t proteins were affinity purified and comparatively assessed by ELISA with respect to antibody-binding characteristics. Sera from patients s uffering from cystic echinococcosis showed no significant differences in reactivity with the antigens derived from either E. multilocularis or E. granulosus. Therefore, parameters other than some minor differen ces in the primary sequence seem to be responsible for the lack of ant igen II/3 recognition in cystic echinococcosis. Note: Nucleotide seque nce data reported in this paper have been submitted to the GenBank(TM) data base with the accession numbers U05573 and U05574.