Hepatitis B infection of the liver in chronic hepatitis C without detectable hepatitis B virus DNA in serum

Hepatitis B virus (HBV) DNA may persist in the liver in the absence of serum HBV-DNA after a self-limited acute hepatitis B. This may also occur in patients with chronic hepatitis C virus (HCV) infection but its prevalence and its impact on liver histology is unknown. HBV-DNA was tested by polymerase chain reaction (PCR) and by in situ hybridisation in liver biopsies from 98 patients with chronic hepatitis C who were hepatitis B surface antigen negative and serum HBV-DNA negative by PCR. HBV-DNA resulted positive in the liver of 37/98 (37.7%) patients without serum HBV-DNA. To test whether these patients had serum HBV-DNA levels under the detection limit of the PCR assay used in this study (50 copies/ml), PCR products in which HBV-DNA was undetectable after visualization of agarose gels were analysed by dot-blot hybridisation. With this method, HBV-DNA was positive in serum of 12/37 patients with liver HBV-DNA. Thus, 25/98 (25.5%) patients have HBV-DNA detectable only in liver. This was confirmed by in situ hybridisation, the percentage of infected hepatocytes ranging from 0.1% to 12%. In patients in whom the HCV infection was shorter than 20 years, HBV infected patients had higher (P = 0.01) fibrosis score (1.64 +/- 1.21) than HBV negative cases (0.53 +/- 0.66). In conclusion, a significant proportion of patients with chronic HCV infection have HBV-DNA in the liver in the absence of viral DNA in serum. The impact of this finding on liver histology deserves further research.