Analysis of host components in hydatid cyst fluid and immunoblot diagnosis of human Echinococcus granulosus infection.

To improve serodiagnosis of cystic hydatidosis, immunoblotting studies were performed to look for a highly specific parasite antigen(s). First, commercially available hydatid cyst fluid antigen preparations were characterized by SDS-PAGE and by immunoblotting with sera specific for parasite and host animal proteins. One preparation, designed for use in complement fixation tests, did not appear to be suitable for immunoblotting because of the low concentrations of parasite antigens. Several host proteins, including serum albumin and IgG, were detected in the cyst fluid. Sera from patients with Echinococcus granulosus infections and other parasitic diseases were examined by immunoblotting for antibodies against specific cyst fluid parasite antigens. Several parasite antigens were variably recognized. Only one antigen, a 40 kDa protein, was recognized by all E. granulosus-infected patients. Reactivity against this antigen was also observed in all sera from E. multilocularis, cysticercosis, and schistosomiasis patients as well as in some filariasis cases. Two E. granulosus antigens, molecules of 12.5 and approximately 17 kDa, were only recognized by antibodies from some E. granulosus patients.