Correlation between hepatitis B virus core-related antigens and intrahepatic covalently closed circular DNA levels

Abstract

BACKGROUND: The hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is postulated to be a persistent source of viral replication. However, the measurement of intrahepatic cccDNA requires liver biopsies as well as assays which are not generally available. A relatively easy and sensitive chemiluminescence enzyme immunoassay has been recently developed for the detection of HBV core-related antigens (HBcrAg). Its concentration has been demonstrated to correlate positively to HBV viral load (Rokuhara et al, J Viral Hep (2003) 10:324-330). Since HBcrAg is generated from pregenomic transcripts, which are produced from cccDNA, this study aimed to investigate the correlation between intrahepatic cccDNA and serum HBcrAg levels. METHODS AND PATIENTS: Liver biopsy and serum samples from 16 hepatitis B e antigen (HBeAg)-positive and 36 antibody-to-HBeAg (anti-HBe)-positive chronic hepatitis B patients were collected. Total intrahepatic HBV DNA and cccDNA were measured by the Invader® assay (Wong et al, Hepatology (2004) 40:727-73). Serum HBcrAg was detected by a chemiluminescence enzyme immunoassay. The detection limit of the assay is 1 KU/mL. RESULTS: HBcrAg was detected in sera of all HBeAg-positive patients and 31/36 anti-HBe-positive patients. The median HBcrAg concentration in sera was higher in HBeAg-positive patients (38,700 KU/mL) than anti-HBe-positive patients (185 KU/mL; P < 0.0001). While HBcrAg levels did not correlate well to ALT levels (r = 0.186, P > 0.05), there was a positive correlation between serum HBcrAg concentration and serum HBV DNA (r = 0.810, P < 0.0001). Serum HBcrAg levels were also found to correlate positively with both intrahepatic total HBV DNA levels (r = 0.700, P < 0.0001) and cccDNA levels (r = 0.664, P < 0.0001). Patients with higher degree of fibrosis had higher serum HBcrAg concentration than patients with no or mild degree of fibrosis (P = 0.025), but there was no direct correlation between the degree of necroinflammation and HBcrAg concentration (P 0.05). CONCLUSION: This pilot study showed that serum HBcrAg measurement correlated positively to viral load. In particular, serum HBcrAg concentration provides a reflection of the degree of fibrosis and levels of intrahepatic total HBV DNA and cccDNA. The usefulness of HBcrAg measurement as an alternative viral marker deserved to be further studied.