The present invention relates generally to the field of Hepatitis B
variants exhibiting a reduced sensitivity to nucleoside analogues, both
in vivo and in vitro. More in particular, reverse transcriptase mutant
rtA181S is provided. Present invention provides assays and methods for
detecting such variant, which assays are useful in monitoring anti-viral
therapeutic regimes and adjusting patient therapy. A diagnostic kit for
detecting the presence of an HBV variant in a biological sample has also
been described.