The present invention provides an isolated polynucleotide acid comprising a polynucleotide sequence having a substantial amount of sequence identity to the entire length of the polynucleotide sequence as set forth in SEQ ID NO: 1 or its complementary strand (SEQ ID NO: 2), the sequence is derived from RT domain of HBV polymerase gene. The present invention also provides a polypeptide and related compositions, as well as methods for using the same.