[Detection and analysis of the new kind of G743C and G743A point mutation of HBV P gene in hepatitis B virus infected patients resistant to lamivudine].

Objective: To explore the point mutation in hepatitis B virus polymerase (HBV P) gene in HBV-infected patients resistant to lamivudine.
Methods: HBV P gene was amplified by PCR and the products was sequenced to analyze the YMDD mutation. Then the variants were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with the following restriction enzymes: Fok I, Ssp I, Alw441 and were separated by 8.0% polyacrylamide gel electrophoresis.
Results: Comparing with the sequences of standard HBV genome, there were 16 patients with G743C mutation and 1 patient with G743A mutation, and the codon ATG turned to ATC and ATA, YMDD motif changed into YIDD. But this kind of YIDD mutation was not proved by PCR-RFLP assay in the 17 patients.
Conclusions: The G743C and G743A mutations in HBV P gene, resulting in YMDD motif changed into YIDD, are detected only by direct sequencing, not by PCR-RFLP. The new kind of G743C and G743A point mutations in HBV P gene is important for the detection of HBV P gene YMDD mutation.