HBsAg has been proved extremely effective in inducing protective antibodies (anti-HBs) and thus has been used as the prophylactic vaccine. Thus far, most studies on HBsAg have focused on the development of hepatitis B vaccines (41), identification of HBsAg-interacting membrane proteins as potential Crizotinib ROS1 host HBV receptors (9, 13), and characterization of the impact of naturally occurring HBsAg mutations on its antigenicity (12, 43). However, specific interactions between HBsAg and host intracellular factors have not been extensively studied. To address this issue, SHBs-secreting cell lines and lineages of HBV transgenic mice persistently expressing HBsAg were used in our previous studies (28, 34, 44). We found that the level of cyclophilin A (CypA) decreased markedly in the livers of HBsAg transgenic mice but increased significantly in their sera (44).

CypA is a multifunctional cellular protein. It is the major binding protein for the immunosuppressive drug cyclosporine (Cs) (14) and exhibits peptidyl-prolyl cis-trans isomerase activity (35). Recently, it was found CypA played important roles in regulating inflammatory responses and viral infections. Regarding these newly recognized physiological functions, CypA was speculated to be involved in HBV infection. In the present study, the mechanism and clinical implications of elevated secretion of CypA induced by SHBs were explored in detail, including studies in cell cultures, hydrodynamic injected mouse models, and chronic hepatitis B patients.

Our findings indicate that expression and secretion of SHBs can trigger the secretion of CypA, which may induce liver inflammation and contribute to the pathogenesis of HBV infection. MATERIALS AND METHODS Plasmids. The SHBs gene (nucleotides [nt] 157 to 837) and the LHBs gene were amplified from a full-length Entinostat genotype C HBV isolate C8 (GenBank accession no. “type”:”entrez-nucleotide”,”attrs”:”text”:”AF461363″,”term_id”:”18252573″,”term_text”:”AF461363″AF461363) and cloned into the pcDNA3 vector (Invitrogen, Carlsbad, CA) with an N-terminal tag of hemagglutinin (HA) under the control of cytomegalovirus (CMV) promoter to construct the plasmid HA-SHBs and HA-LHBs. A secretion-deficient SHBs construct (N77) that contains R169P mutation and its corresponding wild-type SHBs expression construct (N65) were constructed as reported by Khan et al. (16). The HBV replicon plasmid C8-1.3 harboring 1.3 U of HBV genome was constructed in pUC19 vector as previously reported (36). Cell culture and HBV transgenic mice. Huh7 cells were maintained in Dulbecco modified Eagle medium supplemented with 10% fetal bovine serum, 100 U of penicillin/ml, 100 ��g of streptomycin/ml, 2 mM glutamine, 25 mM HEPES solution, and 1 mM sodium pyruvate. HepG2.2.