Clinical significance of IgA antibody to hepatitis B core antigen in patients with hepatitis B virus infection

IgA antibody to hepatitis B core antigen (IgA anti-HBc) was investigated in 85 patients with hepatitis B virus (HBV) infection. For the determination of IgA anti HBc, a sensitive method was devised utilizing an enzyme immunoassay kit for IgM anti-HBc (CORZYME-M kit). In addition, the molecular forms of IgA anti-HBc in sera and in cultured media of patients' peripheral blood lymphocytes (PBL) were analysed by high speed performance liquid chromatography and the above enzyme immunoassay kit. The following results were obtained: 1. IgA anti-HBc was only detected in sera of HBs antigen positive patients. 2. IgA anti-HBc was frequently present in patients with HBV infection, but the titer of IgA anti-HBc in asymptomatic carriers was significantly lower than that in other liver diseases. It was noteworthy that the titer of IgA anti-HBc was significantly higher in patients carrying HBe antigen than in HBe antigen-free patients. 3. During the clinical course of acute hepatitis (AH), IgA anti-HBc revealed a high titer at the initial phase and rapidly decreased like IgM anti-HBc in the convalescent phase. In contrast, the titer of IgA anti-HBc in patients with chronic active hepatitis (CAH) remained high during the observation period showing no relation to liver function tests. 4. With respect to the molecular profile of IgA anti-HBc, the polymeric form was predominant in sera from AH patients while the monomeric form was predominant in sera from CAH patients. 5. IgA anti-HBc was frequently produced in the cultured medium of PBL from patients. The molecular forms of IgA anti-HBc in these cultured media were predominantly of polymeric IgA in AH while prominently of monomeric IgA in CAH. From these results, IgA anti-HBc was found to be a new marker of HBV infection which may reflect the activity of liver cell damage. It is also worthy to note that the differentiation of AH from CAH will be possible by analyzing the molecular form of IgA anti HBc in sera and the cultured media of PBL.