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Although occult hepatitis B virus (HBV) infection (HBV-DNA in serum in the absence of hepatitis B surface antigen [HBsAg]) is common in chronic hepatitis C, its characteristics are not well known. In this work, the presence of HBV-DNA (by polymerase chain reaction; PCR) and its distribution (by in situ hybridization) in liver biopsies and peripheral blood mononuclear cells (PBMCs) from 32 patients with chronic hepatitis C and occult HBV infection and in 20 HBsAg chronic carriers were determined. The results showed that serum HBV-DNA levels were statistically lower (P = 0.001) in patients with occult HBV infection than in HBsAg chronic carriers. The HBV infection pattern in liver cells was identical between patients with occult HBV infection and those with chronic hepatitis B. However, the mean percentage of HBV-infected hepatocytes was significantly lower (P = 0.001) in patients with occult HBV infection (5 +/- 4.44%) than in HBsAg chronic carriers (17.99 +/- 11.58%). All patients with chronic hepatitis B have HBV-DNA in their PBMCs while this occurred in 50% of the cases with occult HBV infection. In conclusion, patients with occult HBV infection have a low number of HBV-infected hepatocytes and this fact could explain the lack of HBsAg detection and low viremia levels found in these cases.

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.

Although occult hepatitis B virus (HBV) infection (HBV-DNA in serum in the absence of hepatitis B surface antigen [HBsAg]) is common in chronic hepatitis C, its characteristics are not well known. In this work, the presence of HBV-DNA (by polymerase chain reaction; PCR) and its distribution (by in situ hybridization) in liver biopsies and peripheral blood mononuclear cells (PBMCs) from 32 patients with chronic hepatitis C and occult HBV infection and in 20 HBsAg chronic carriers were determined. The results showed that serum HBV-DNA levels were statistically lower (P = 0.001) in patients with occult HBV infection than in HBsAg chronic carriers. The HBV infection pattern in liver cells was identical between patients with occult HBV infection and those with chronic hepatitis B. However, the mean percentage of HBV-infected hepatocytes was significantly lower (P = 0.001) in patients with occult HBV infection (5 +/- 4.44%) than in HBsAg chronic carriers (17.99 +/- 11.58%). All patients with chronic hepatitis B have HBV-DNA in their PBMCs while this occurred in 50% of the cases with occult HBV infection. In conclusion, patients with occult HBV infection have a low number of HBV-infected hepatocytes and this fact could explain the lack of HBsAg detection and low viremia levels found in these cases.