Significance of detection of immune-complexed 8 kDa hydatid-specific antigen for immunodiagnosis of hydatidosis.

Three micro-enzyme-linked immunosorbent assay (micro-ELISA) systems were developed and evaluated for detection of specific free circulating antigen and circulating immune-complexes (CICs) of 8 kDa antigen in the sera of patients with hydatidosis. All (100%) the sera of 30 confirmed positive cases of hydatidosis had detectable levels of antigen in the acid-treated sera. However, 23 (77%) and 26 (87%) sera of 30 confirmed cases had free as well as CICs of 8 kDa antigen in the untreated and in the polyethylene glycol (PEG) precipitated sera, respectively. None of the sera from other patients with parasitic infections or viral hepatitis had any detectable levels of 8 kDa antigen in the untreated, acid-treated or PEG-precipitated serum samples. The investigations, therefore, suggested that the demonstration of circulating antigen employing monospecific antibodies to affinity purified 8 kDa antigen in acid-treated sera is more efficient as compared to detection of free circulating antigen or CICs in the untreated or in the PEG-precipitated sera which could provide a specific immunodiagnostic tool for ongoing hydatid infection.