Differential, serodiagnosis for cystic and alveolar echinococcosis using fractions of Echinococcus granulosus cyst fluid (antigen B) and E-multilocularis protoscolex (EM18)

Echinococcus granulosus cyst fluid and E. multilocularis protoscolex extrac t were fractionated by a single step of preparative isoelectric focusing, r esulting in an antigen B-rich fraction (S-WC)) and an Em18-rich fraction, r espectively. The usefulness of both fractions for differential serodiagnosi s of cystic (CE) and alveolar (AE) echinococcosis was evaluated by a large- scale immunoblot analysis on a battery of 354 serum samples. These included 66 from AE patients originating from four different endemic areas, 173 fro m CE patients originating from seven different endemic areas, 71 from patie nts with other parasitic diseases, 15 from patients with hepatomas, and 29 from healthy individuals, In an immunoblot with the antigen B-rich fraction , 92% (158 of 173) of the CE sera as well as 79% (52 of 66) of the AE sera reacted with the 8-kD subunit. No cross-reactivity occurred with any sera f rom patients with cysticercosis, other parasitic diseases, or with hepatoma s, or from healthy controls. In an immunoblot with the Em18-rich fraction, all but two sera from AE patients (64 of 66, 97%) recognized Em18, and only nine of 34 CE sera from China reacted with it. All other (139) CE sera fro m six other countries were negative as were all (115) other non-echinococco sis sera. These findings indicate that antigen B (8-kD) is not species-spec ific for E, granulosus but is genus-specific for Echinococcus and that the Em18 antigen is a reliable serologic marker for species-specific differenti ation of AE from CE.