OBJECTIVETo determine the mutational profile and clinical implications of the viral reverse-transcriptase (rt)A 181T mutation in hepatitis B virus (HBV) through population-based analysis of clinical samples.

METHODSSerum samples from 3, 013 patients who visited The 302 Hospital (Beijing, China) were investigated.HBV DNA was extracted and HBV mutations and genotypes were determined by direct sequencing.Recombinant plasmids harboring the rtA181T/sW172* mutant or wild type sequence were constructed and transfected into the HepG2 cell line. The levels of HBsAg in culture supernatants were compared and statistically analyzed.

RESULTSThe incidence of rtA181T across the study population was 4.1% (165/3, 013), and most of the rtAl 81T-positive patients had received adefovir and/or lamivudine.Forty percent (66/165) of the rtA 181T cases were single mutants and treatment responsive, 46.1% (76/165) included the adefovir-resistant mutation rtA 181 V/N236T, 12.1% (20/165) included the lamivudine-resistant mutation rtM204V/rtM2041, and 1.8% (3/165) included multidrug-resistant mutations.Interestingly, 73.9% (122/165) of the rtA181T-positive samples were detected with co-existing wild-type nucleotides at the site. The rates of HBV/C to HBV/B were 92.1% to 7.9% in the rtA181T-positive patients, but 82.1% to 17.9% in the rtA181T-negative paticnts (P less than 0.01).Almost all (98.2%; 129/165) of the rtA181T led to sW172*, while only 1.8% of the rtA181T (3/165) led to sW172L or sW172S.HBsAg secretion in vitro was reduced from the rtA181T/ sW172* strain, but there was no significant difference observed in the average serum HBsAg and HBV DNA levels of patients who carried or did not carry the mutant.

CONCLUSIONThe HBV rtA181T mutation is closely associated with adefovir and lamivudine exposure.rtA181T may led to sW172*, culminating in suppression of HBsAg secretion.However, co-existence of the mutant with wild-type sequences was common among our patient population, suggesting that the mutation had little impact on serum HBsAg and HBV DNA levels across the clinical study population.