High rate of viral replication and lacking of proofreading activity in hepatitis B virus (
HBV) polymerase lead to the generation of mutations in HBV virus. Mutations in the
reverse transcriptase (RT) region of
HBV polymerase are demonstrated to be strongly associated with drug resistance during
antiviral treatment. However, the presence of mutations as well as its clinical significance in treatment-naïve
hepatitis patients (defined as pre-existing mutations) need to be further investigated. In the present study, a total of 168 serum samples from treatment-naive
chronic hepatitis B (CHB) patients were collected, and the RT region of
HBV polymerase was sequenced. The results showed that pre-existing mutations in the RT region of
HBV polymerase were detected in 43 of 168 (25.6%) treatment-naive CHB patients within which there were no well-characterized primary
nucleotide analogs (
NAs) resistance sites. Three dominant sites at rt191, rt207 and rt226 were found mutant in 7(16.28%), 8(18.60%), and 14(32.56%) samples respectively among these 43 patients. No significant correlation was found between pre-existing mutations and gender, age, HBV genotype, ALT,
HBeAg or HBV
DNA loads. However, patients with pre-existing RT mutations under
HBeAg sero-negative status exhibited decreased HBV
DNA loads, which contributed to the decreased HBV
DNA loads in the total
HBeAg sero-negative patients. The above investigation indicated that there was a prevalence of pre-existing mutations in RT region of
HBV polymerase which might affect the serum HBV
DNA level in treatment-naive CHB patients. Its effects on the occurrence of
NAs resistance and the prognosis
after treatment need to be further investigated.