Purification of HBV virions.

Virions from serum of HBV patients were prepared as described previously (47). Briefly, patient serum was centrifuged to remove cell debris and precipitated with polyethylene glycol 8000 (PEG 8000). The precipitated virions were resuspended in TNE (10 mM Tris, pH 8.0, 100 mM NaCl, 1 mM EDTA) buffer and then digested with DNase I. The digested virions were subjected to 10 to 50% OptiPrep (catalog number D1556; Sigma) separation by ultracentrifugation. The virions from the core protein peak fraction were reprecipitated with PEG 8000 and lysed by resuspension in TNE buffer. The resuspended virions were then treated with 0.5 μg/μl proteinase K (catalog number 19133; Qiagen) to remove nonencapsidated proteins. The reactions were detected by Western blotting. These experiments were approved by the Institutional Review Board (IRB) (WIVH02201801) at Wuhan Institute of Virology, Chinese Academy of Sciences (CAS).