Immunoblot evaluation of the species-specificity of Em18 and Em16 antigens for serodiagnosis of human alveolar echinococcosis.

An immunoblot study to confirm the species-specificity of the diagnostic antigens Em18 and Em16 of Echinococcus multilocularis protoscolex extract showed that both antigens cross-reacted with sera from cystic echinococcosis (CE) patients. The 18 kDa component was detectable by 75% of the sera from active alveolar echinococcosis (AE) patients, while only 31% detected Em16. Western blot analysis also showed that AE sera recognized a band in the 18 kDa region of E. granulosus protoscolex extract, which was different from the 16/17 kDa subunit of antigen B. The results suggested that Em18 antigen is present in E. granulosus as well as E. multilocularis, and that some CE patients may have serum antibody against this antigen.