C3b binding and IgG binding onto platelets in hepatitis B virus infection

Abstract

Sera from patients with acute hepatitis B, hepatitis B surface antigen (HBsAg)-positive chronic hepatitis, and from asymptomatic HBsAg carriers were evaluated by enzyme-linked immunosorbent assay and by platelet 125I-labeled staphylococcal protein A test for the presence of C3b-binding IgG, IgM, and IgA activity (immunoconglutinins and circulating immune complexes of IgG, IgM, and IgA classes), and for the presence of IgG binding onto platelets, respectively. Significantly elevated C3b-binding IgG, IgM, and IgA activity ( P < 0.001) was found in patients with acute hepatitis B, C3b-binding IgG activity ( P < 0.01) in chronic hepatitis patients, but normal C3b-binding Ig activity in HBsAg carriers and controls. Similarly, platelet-bound IgG was significantly elevated in patients with acute hepatitis B and HBsAg-positive chronic hepatitis ( P < 0.001). Serial studies in acute hepatitis B demonstrated that C3b-binding IgG and IgA activity significantly correlated with serum aspartate transaminase and bilirubin ( P < 0.01) and platelet-bound IgG with aspartate transaminase values ( P < 0.05). In addition, a significant association of C3b-binding IgG activity with platelet-bound IgG was found ( P < 0.01). The results suggest that C3b-binding ELISA and PIPA tests may have clinical and immunopathogenic importance in studies on hepatitis B infection.