Viral variants

A method for determining the potential for an HBV to exhibit reduced sensitivity to a nucleoside analogue, said method comprising isolating DNA or corresponding mRNA from said HBV and screening for one or more mutation(s) in the nucleotide sequence encoding HBV DNA polymerase resulting in at least one amino acid substitution in the D domain of said DNA polymerase wherein the presence of such a mutation is an indication of the likelihood of resistance to said nucleoside analogue, wherein said one or more mutation(s) is selected from the group consisting of N584S, N584K, S/H584N/K, R588K, N/Q 584H, K587R in the following sequence:

• Z47Z48GIHLNPZ49KTKR (SEQ ID NO:9)
• wherein Z47 is S or D;
• Z48 is L or V, and Z49 is N or Q, wherein the notation defines a codon number position of HBV genotype with reference to codon 550 being methionine in the YMDD motif, the letter(s) proceeding the number in the notation of the mutation being at least one wild-type or permutation amino acid at said codon number position, and the letter(s) subsequent to the number in the notation being at least one post-mutation amino acid at said codon number position, wherein Z47 is codon number position 576 of the HBV genotype.