OBJECTIVETo explore the biological and clinical significance of the double mutations of C1673T/C1799G in HBV C promoter (CP).

METHODSTotally 136 patients were enrolled, including 25 asymptomatic carriers (AsC), 38 patients with chronic hepatitis B (CHB), 24 patients with chronic severe hepatitis B (CSHB), 36 cases with liver cirrhosis (LC) and 13 cases with hepatocellular carcinoma (HCC). HBV subgenotypes and mutations in CP of all samples were determined by nested-PCR and direct nucleotide sequence analysis. The C to T mutation at nucleotide 1673 and C to G at nucleotide 1799 were analyzed in different subgenotypes, and the relationships of C1673T/C1799G double mutations with HBV replication, the expression of HBeAg, and with the severity of liver disease after chronic HBV infection were studied.

RESULTSOf the 136 patients, 110 were subgenotype Ba, 1 was Bj, 7 were C1, and 18 were C2. C1673T/C1799G double mutations in Ba were determined in 106 (96. 4%) samples, which was significantly higher than in C1 (14.3%) and C2 (12.5%) subgenotype (P < 0.0001). In contrast to non-mutation group, HBV DNA content in mutation group had no significant difference (P > 0.05). The prevalence of the mutation was lower in HBeAg positive patients (71.4%) than in HBeAg negative patients (87.5%) (P < 0.05). The frequencies of the double mutations were not significantly different among ASC, CHB, CSHB, LC and HCC groups (P > 0.05).

CONCLUSIONIn Ba subgenotype, double mutations of C1673T/C1799G is much popular than in C1 and C2; the mutation has no effect on HBV replication, and may not be associated with the outcome of chronic HBV infection.