5% experienced single adefovir, 12.0% experienced single lamivudine, 49.4% experienced both adefovir and lamivudine, and 15.8% experienced adefovir/lamivudine plus telbivudine/entecavir). Only four patients with rtA181T were antivirals-naive. HBV genotype C/B were 93.0%/7.0% for rtA181T positive patients, and 84.6%/15.4%

for rtA181T negative patients (P <0.01), suggesting there was a positive link between rtA181T with genotype C HBV. Most but not all rtA181T led to sW172* (stop codon) mutation on overlapping S-gene and coexistence of rtA181T/sW172* with wild-type sequence was frequently detected (22.0% presented as sW172* alone, 69.9% presented AZD2014 ic50 as sW172* concomitant with the wild-type, 5.7% presented as sW1 72* with sW1 72/L or sW172S, etc). Phenotypic analysis of representative rtA181T/sW172* strains showed that the 50% effective concentration (EC50) values of adefovir for the mutants were 1.8-fold to 2.9-fold higher than that of wild-type strain. By contrast, the EC50 of adefovir for rtA1 81V or rtN236T mutants was at least 3.5-fold higher than that of wild-type strain. A defect in HBsAg secretion and a decreased replication capacity of rtA181T PLX4032 chemical structure (sW172*) strain were observed in comparison with wild-type strain in vitro; while no significant difference in average serum HBsAg and HBV DNA levels was observed between patients with and without rtA181T/sW172*. Conclusions: The emergence of HBV rtA181T mutation is closely

associated with adefovir and lamivudine exposure, but it may not directly cause adefovir resistance. The clinical significance of rtA181T should be properly interpreted. Disclosures: The following people have nothing to disclose: Xiaodong Li, Yan Liu, Liming Liu, Pan Zhao, Jiuzeng Dai, Zengtao Yao, Shaojie Xin, Dongping Xu Introduction: in chronic Hepatitis B (CHB), loss of hepatitis B surface antigen (HBsAg) and seroconversion to anti-HBs is generally considered as the ultimate goal of antiviral therapy. New combination therapy of Pegylated

interferon (PegIFN) with potent HBV Inhibitors such as tenofovir (TDF) is assessed in order to Rolziracetam improve the rate of HBsAg loss. The HBsAg gene contains the “a determinant” epitope located within the major hydrophilic region (MHR). In this study we investigate the S-gene variability of patients at baseline of PegIFN plus TDF combination therapy in order to determine the role of HBsAg variants on response to treatment. Methods: CHB patients received 180 μg of Peg-IFN/week plus 300 mg of TDF /day during 48 week. Patients were seen every 3 months. Sustained virologic response (SVR) was defined as HBV DNA< 2000UI/mL 48 weeks after end of therapy. Non-sustained virologic response (N-SVR) was defined as HBV DNA > 2000 UI/mL 48 weeks after end of therapy. HBs Ag-encoding gene from each patient’s serum at baseline was PCR-amplified, cloned and sequenced. At mean of 17 clones per patient were analysed. Results: Forty CHB patients were included in this study.