Higher detection rates of amino acid substitutions in HBV reverse transcriptase/surface protein overlapping sequence is correlated with lower serum HBV DNA and HBsAg levels in HBeAg-positive chronic hepatitis B patients with subgenotype B2.

OBJECTIVES

Hepatitis B virus (HBV) subgenotype B2 is prevalent in China and some other parts of Asia. This study aimed to carry out a subgenotype B2 specific mutation analysis on important amino acid (AA) sites in overlapping reverse transcriptase (RT) and surface (S) protein coding regions of HBV.

MATERIALS AND METHODS

A total of 143 hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB) patients with HBV subgenotype B2 infection were enrolled. HBV RT/S regions were sequenced focusing on 43 RT resistance AA sites and 31 S AA sites with functional/structural/conformational importance.

RESULTS

According to the consensus AA sequence for subgenotype B2, 49.7% (71/143) of RT and 33.6% (48/143) of S protein sequences contained detectable substitutions at 58.1% (25/43) of studied AA sites in RT and 51.6% (16/31) of AA sites in S proteins, respectively. The most frequently detected substitutions were rtN134D/S (44/143, 30.8%) and sT126A/S (22/143, 15.4%), which were located in the RT A-B interdomain region and the corresponding antigenicity determinant region of S protein, respectively. In addition, two patients harboring drug resistance mutations rtL80V+rtM204I and rtL180M+rtM204V were found. Interestingly, the patients with detectable AA substitutions at any of the 74 sites in either/both of RT/S sequences had significantly lower serum HBV DNA and HBsAg levels than that in patients without detectable RT/S AA substitutions (P<0.05). A trend Chi-squared test indicated that a negative association of serum HBsAg level with S protein sequence substitution rate was statistically significant (P=0.047).

CONCLUSION

This subgenotype B2 specific mutation analysis revealed some naturally occurring hot spot substitutions at important AA sites of HBV RT/S proteins, which together might influence the serum HBV DNA and HBsAg levels in HBeAg-positive CHB patients.