Quantitative detection of hepatitis B virus cccDNA in infected hepatocytes / 中华传染病杂志

ABSTRACT

Objective To establish a method for quantitative detection of hepatitis B virus covalently closed circular DNA(HBV cccDNA ) in infected cells. Methods The transfected cell line HepG2.2.15 which can consistently produce Dane particles was maintained in DMEM containing 380 ?g/ml G418 and 10% fetal bovine serum. Cells in the exponential period were harvested from flasks, then intracellular HBV cccDNA was extracted from pellet containing 1?10~6 cells with mini plasmid extraction kit (QIAGEN).The extraction product was further purified by mung bean nuclease to remove HBV relaxed circular DNA possibly remained. HBV cccDNA was quantitatively detected by fluorescent PCR with selective primer set and Taqman MGB probe. Culture medium before exponential period, HBV DNA positive and negative serum samples from patients with chronic hepatitis B (mild) were amplified simultaneously to test the specificity of the fluorescent PCR method. Plasmids containing whole HBV genome were amplified with the same primer set and fluorescent probe to determine the sensitivity of the method. Results HBV cccDNA was detectable in HepG2.2.15, and the average quantity was 18 copies per cell approximately. No detectable fluorescent signal was observed when culture and serum samples were amplified. The detectable HBV cccDNA was as low as 10~3 copies per ml at least by this method. Conclusions This method is convenient, highly specific and highly sensitive. It can be utilized in the quantitative detection of intracellular HBV cccDNA as well as in the screening and evaluation of antiviral agents.