HBV primary drug resistance in newly diagnosed HIV-HBV-coinfected individuals in Spain.

Background: The wide use of lamivudine (3TC) as oral therapy for chronic HBV infection has favoured the selection and circulation of 3TC-resistant HBV strains worldwide. Although transmission of 3TC-resistant HBV variants has been reported only sporadically, few studies have been conducted in the HIV population where exposure to 3TC has been greater forming part of antiretroviral therapy (ART) regimens. Methods: All individuals positive for serum hepatitis B surface antigen (HBsAg), newly diagnosed with HIV-1 infection, naive to ART and enrolled in the Spanish HIV cohort (CoRIS) since 2004 were identified. The HBV polymerase gene was sequenced and drug resistance mutations were characterized retrospectively in stored frozen plasma specimens. Results: From 4,419 ART-naive HIV-1-infected individuals, 223 (5.1%) were positive for serum HBsAg. Baseline stored sera were available for 84 patients, of whom 73 could be characterized virologically. This population was mainly represented by men who had sex with men (52.1%), native Spaniards (65.7%) and Latin Americans (16.4%). The mean age was 36 years, mean CD4 + T-cell count 375 cells/mm 3 and mean plasma HIV RNA 4.5 log 10 copies/ml. The HBV genotype distribution was 64% A, 20% F, 12% D and 4% others. Drug-resistant mutations in the HBV polymerase were found in four (5.5%) patients: two harboured rtL180M, one rtL80V and one rtV173L. Conclusions: The rate of primary drug resistance in HBV among newly diagnosed HIV-HBV-coinfected patients in Spain is currently low (5.5%) and restricted to 3TC. Thus, HBV drug resistance testing before prescription of oral antiviral therapy is not warranted, although periodic surveillance might be recommended.