Demonstration of a specific Echinococcus multilocularis antigen in the supernatant of in vitro maintained protoscolices.

Serodiagnosis of echinococcosis is still often met with difficulties resulting from unspecific reactions due to crude antigens which contain numerous host-derived proteins. In order to eliminate host protein contamination we produced Echinococcus multilocularis antigen by methods of in vitro technique: Evaginated protoscolices of Echinococcus multilocularis isolated from experimentally infected Mongolian gerbils (Meriones unguiculatus) were maintained in RPMI 1640 medium. Although no serum proteins were added, protoscolices could be kept alive for more than 2 weeks. The supernatants harvested from protoscolices cultures were tested for their immunoreactivity against sera of patients with confirmed alveolar or cystic echinococcosis, cysticercosis, schistosomiasis or fascioliasis by means of SDS-PAGE and immunoblotting. A polypeptide band at about 62,000 mol. mass was identified which proved to be specifically immunoreactive with sera from patients with alveolar echinococcosis, whereas sera from patients with cystic echinococcosis or with other helminthic infections as well as sera from healthy blood-donors did not react with this polypeptide band. Thus, the use of supernatant antigen in immunoblotting technique allows a serological differentiation between infections with Echinococcus multilocularis and those with Echinococcus granulosus and provides an accurate diagnosis of alveolar echinococcosis.