T1764G1766 core promoter double mutants are restricted to Hepatitis B virus strains with an A1757 and are common in genotype D

To investigate the role of pre-core and basal core promoter (BCP) mutants in hepatitis B e antigen (HBeAg)-negative chronic hepatitis B (e-CHB) in Iran, Hepatitis B virus strains from 30 patients and 42 anti-HBe-positive asymptomatic carriers (ASCs) were characterized. G 1896 A pre-core stop mutants, detected in 77 % of e-CHB patients and 85 % of ASCs, showed no association with virus load or aminotransferase levels. Twenty per cent of e-CHB patients and 31 % of ASCs harboured T 1762 A 1764 mutants. When this double mutation was associated with G 1757 , it was linked to a higher virus load in patients than when it was associated with A 1757 (10 5·2±1·8 vs 10 3·2±0·8  copies ml −1 ; P =0·004). Interestingly, the most common BCP mutations were T 1764 and G 1766 , which were present in 33 % of e-CHB patients and 29 % of ASCs. These were associated with higher virus load and aminotransferase levels compared with patients lacking core promoter mutations, although this was not significant. The T 1764 G 1766 double mutation was only present in strains with A 1757 ( P <0·001), which is more frequent in strains of genotype D than in those belonging to other genotypes. On the other hand, the T 1762 A 1764 double mutation was found more frequently in association with G 1757 than with A 1757 . The T 1762 A 1764 double mutation forms a binding site for hepatocyte nuclear factor 1 (HNF1), which is constrained by A 1757 . However, the T 1764 G 1766 double mutant may form a binding site for HNF3. Thus, position 1757 affects the emergence of promoter double mutants and would predict a relative genotypic restriction of both the T 1762 A 1764 and the T 1764 G 1766 double mutants.