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Objectives: To study the evolution of HBV quasispecies under the pressures of lamivudine (LAM) - entecavir (ETV) sequential therapy and its clinical significance., Methods: Consecutive serum samples from 2 patients underwent LAM-ETV sequential therapy were extensively studied for HBV quasispecies composition and evolution, using PCR-cloning-sequencing method. Maximum likelihood trees were built to analyze the genetic relationship between representative sequences. Correlation between HBV quasispecies evolution and serological/virological data was analyzed to determined the clinical significance of the evolution of HBV quasispecies during prolonged nucleotide analog therapy., Results: Virological breakthrough was observed in both patients. Patient I acquired sustained virological response after switching to ETV rescue therapy, whereas Patient II suffered from virological breakthrough after 72 weeks of ETV therapy. Each virological breakthrough was accompanied with the replacement of previous drug susceptible dominant quasispecies with a drug resistant variant, indicating a close correlation between quasispecies composition and drug susceptibility. The rtL180M+S202G+M204V triple mutant, which was most likely a descendant of the LAM resistant rtL180M+M204V variant, was closely correlated with ETV resistant in Patient II., Conclusion: Quasispecies composition of HBV is closely correlated with nucleotide analog susceptibility. ETV resistant variant can emerge from a LAM resistant viral population. Dynamic monitoring of HBV quasispecies composition is of great importance during nucleotide analog therapy.

Objectives: To investigate the quasispecies dynamics of hepatitis B virus (HBV) during the course of exacerbation and resolution of chronic hepatitis B in a patients., Methods: Five serum samples were collected from a patient with two episodes of exacerbation and resolution of chronic hepatitis B. A method of PCR-TA cloning-conformation sensitive gel electrophoresis (CSGE)-sequencing was performed to study the dynamic changes of HBV quasispecies in basal core promoter (BCP), precore and core regions of HBV genome., Results: Quasispecies complexity was 10 and 12 at the points of exacerbations, and 14 and 17 at the points of resolutions (t = 3.133, P < 0.05). Ratio of dominant quasispecies in HBV population was high (42.4% and 51.5%) during exacerbations and low (30.3% and 21.2%) during resolutions (t = 3.295, P < 0.05). All dominant quasispecies, except the one during the second resolution, carried core P5T, L60V, S155T, and precore G1896A mutations., Conclusion: The composition of HBV quasispecies changes due to the change of host immune status, and immune pressure might lead to the selection of immune escape mutants.

Objective: To observe the evolution and differentiation of hepatic oval cells after transplanted into the spleens of homogenous rats, providing experimental data for treating hepatic failure with hepatic stem cells., Methods: A two-step perfusion procedure was used to separate hepatic parenchymal cells from nonparenchymal cells. Then the suspension of nonparenchymal cells was centrifuged in Percoll gradients. The isolated cells were cultured, identified, and then transplanted into the spleens of homogenous rats undergone 2/3 hepatectomy., Results: The obtained cells were various in size with ovoid nuclei and inadequate cytoplasm. After 12 hours' culture, they revealed the characteristics of epithelial cells. Both the freshly isolated and cultured cells showed positive staining for cytokeratin 19 (CK19), OV6, alpha fetal protein (AFP), but negative for leucocyte common antigen (LCA). After intraspleenic transplantation into homogenous rats undergone partial hepatectomy, hepatic oval cells were differentiated into liver tissue-like structure including hepatocyte cords and bile ducts, and formed hepaticized spleen. But this kind of structure was not observed in the controls., Conclusion: The isolated rat hepatic oval cells show the biological characteristics of hepatic stem cells and can differentiate into hepatocytes and biliary epithelial cells under appropriate circumstances.