• hepatitis B virus;
  • mutations;
  • occult infection;
  • surface antigen;
  • transfection

Aim:  To determine the prevalence of occult hepatitis B virus (HBV) infection in a group of human immunodeficiency virus (HIV)-infected Brazilian patients and to investigate its association with biochemical, virological and molecular features.

Methods:  Sera from 43 patients positive for HBV core antibody and negative for HBV surface antigen (HBsAg) were tested for HBV DNA positivity by semi-nested PCR. HBV loads were assessed by real-time PCR. S gene was cloned and sequenced for HBV isolates from 3 patients. HBsAg expression of these cases was performed in HuH7 cells.

Results:  HBV DNA was found in 6/43 (14%) samples, all except one associated with low viral loads. Occult HBV infection was further correlated with anti-hepatitis C virus (anti-HCV) antibodies positivity, but not with alanine aminotransferase (ALT) elevated levels. S gene sequences derived from three patients were determined. Two of them displayed mutations that may explain HBsAg negativity. In the first one, a stop codon mutation was found at position 216 in the C-terminal end of HBsAg. In the second patient, E164D and I195M substitutions in HBsAg, associated with lamivudine-resistance mutations in the polymerase were identified. As expected, all clones showing those mutations displayed undetectable or very low levels of HBsAg.

Conclusion:  Occult HBV infection was frequent in HIV-infected patients, was not associated with ALT elevation but significantly correlated with HCV seropositivity. The low viremia and the detection of HBsAg mutants confirm that multifactorial mechanisms are involved in occult HBV infection. HBV molecular monitoring should be employed for an adequate management of HBV/HIV co-infected patients.