Occurrence of occult hepatitis B virus infection associated with envelope protein mutations according to anti-HBs carriage in blood donors.

ABSTRACT

OBJECTIVES: Occult hepatitis B virus infection (OBI) carries a risk of hepatitis B virus (HBV) transmission and hepatocellular carcinoma. As previous studies have had a limited sample size, the characteristics of OBI with genotype B and C (OBIB and OBIC) mutations relating to hepatitis B surface antibody (anti-HBs) elicited by vaccination or a limited host immune response to HBV have not been fully explored. METHODS: In this study, the occurrence of OBIB or OBIC strains associated with envelope protein (pre-S/S) amino acid substitutions obtained from 99 blood donors stratified according to anti-HBs carriage were characterized extensively. RESULTS: According to the presence of anti-HBs within each genotype, the number and frequency of substitution sites specific for anti-HBs(-) OBIB were higher than those specific for anti-HBs(+) OBIB strains (67 vs 31; 117 vs 41), but the reverse pattern was found in OBIC strains (3 vs 24; 3 vs 26). Mutations pre-s1T68I and sQ129R/L were found uniquely in 15-25% of anti-HBs(+) OBIB carriers and mutation pre-s1A54E was found preferentially in anti-HBs(+) OBIC, while 17 substitutions were found preferentially in 11-38% of anti-HBs(-) OBIB strains. In the major hydrophilic region (MHR) region, mutations sS167 in OBIB, sT118 in OBIC, and sA166 in both genotypes were possibly immune-induced escape mutation sites. CONCLUSIONS: Several mutations in pre-S/S of OBI appeared to be associated with carrier anti-HBs pressure, which might be risk factors for potential reactivation of viruses under anti-HBs selection in OBI carriers.