THE HEPATITIS-B VIRUS M539V POLYMERASE VARIATION RESPONSIBLE FOR 3TC RESISTANCE ALSO CONFERS CROSS-RESISTANCE TO OTHER NUCLEOSIDE ANALOGS

A variant of hepatitis B virus (HBV) containing a Met-to-Val substitut ion (M539V) in the YMDD motif of the polymerase nucleoside-binding dom ain exhibited resistance to the cytosine analogue lamivudine (3TC). To determine if the mutation responsible for the M539V polymerase varian t affected the sensitivity of the virus to other nucleoside analogues, we constructed a tetracycline-responsive cell line, HepAD79. This cel l line is stably transfected with a cDNA copy of the pregenomic RNA of an HBV genome containing an A-to-G mutation in the first position of the polymerase gene codon 539. This mutation results in a Met-to-Val s ubstitution at amino acid conditions, HepAD79 cells produced HBV RNA, contained HBV DNA associated with immature core particles and released core-associated HBV DNA into the medium. The M539V polymerase variant produced in this cell line was approximately 26-fold less sensitive t o the antiviral effects of 3TC than wild-type virus. In addition, this variant demonstrated decreased sensitivity to the cytosine analogues FTC and ddC, as well as the thymidine analogue AZT.