Diagnostic value of anti-arc 5 IgG antibody and analysis of the IgG subclasses in sera of patients with cystic hydatid disease

Abstract

Serodiagnosis of cystic hydatid disease (CHD) due to the metacestode of Echinococcus granulosus depends on detecting antibodies specific to hydatid antigen, but cross-reactivity with other parasites is one of the major draw-backs. We used a commercially-available antigen that elicits the arc 5 in immunoelectrophoresis and analysed the immunoglobulin class and the IgG subclass response by an ELISA. We tested sera from patients with confirmed CHD, cystic mass/lesions (CML) of non-hydatid origin, cysticercosis and healthy controls. High levels of antibodies to the hydatid antigen in all three classes (IgG, IgM and IgA) were observed only in the CHD patients. Significantly, only IgG antibody levels were discriminative and of diagnostic value. Also discussed is the validity of reading the significant cut-off point in IgG-ELISA in relation to a clinically important group of patients such as those with a CML of non-hydatid origin rather than healthy controls. Analysis of the anti-arc 5 IgG subclass responses demonstrated high antibody responses in all subclasses among the hydatid patients, with IgG3 the most discriminatory. The significance of the elevation of all four subclasses and more specifically of IgG4 in CHD is discussed in relation to certain biological activities of these immunoglobulin molecules.