AIM:To evaluate the covalently closed circle DNA (cccDNA)level of hepatitis B virus (HBV) in patients’ liver and sera.METHODS:HBV DNA was isolated from patients’ liverbiopsies and sera.A sensitive real-time PCR method,whichis capable of differentiation of HBV viral genomic DNA andcccDNA,was used to quantify the total HBV cccDNA.Thetotal HBV viral DNA was quantitated by real-time PCR usinga HBV diagnostic kit (PG Biotech,LTD,Shenzhen,China)described previously.RESULTS:For the first time,we measured the level of HBVDNA and cccDNA isolated from ten HBV patients’ liver biopsiesand sera.In the liver biopsies,cccDNA was detected from allthe biopsy samples.The copy number of cccDNA ranged fromfrom 0.03 to 173.1 per cell,the copy number of total HBVDNA ranged from 0.08 to 3 717 per cell.The ratio of totalHBV DNA to cccDNA ranged from 1 to 3 406.In the sera,cccDNA was only detected from six samples whereas HBVviral DNA was detected from all ten samples.The ratio ofcccDNA to total HBV DNA ranged from 0 to 1.77%.To furtherinvestigate the reason why cccDNA could only be detected insome patients’ sera,we performed longitudinal studies.ThecccDNA was detected from the patients’ sera with HBVreactivation but not from the patients’ sera without HBVreactivation.The level of cccDNA in the sera was correlatedwith ALT and viral load in the HBV reactivation patients.CONCLUSION:HBV cccDNA is actively transcribed andreplicated in some patients’ hepatoo/tes,which is reflectedby a high ratio of HBV total DNA vs cccDNA.Detection ofcccDNA in the liver biopsy will provide an end-point for theanti-HBV therapy.The occurrence of cccDNA in the sera isan early signal of liver damage,which may be anotherimportant clinical parameter. AIM: To evaluate the covalently closed circle DNA (cccDNA) level of hepatitis B virus (HBV) in patients ’liver and sera. METHODS: HBV DNA was isolated from patients’ liver biopsies and sera. A sensitive real-time PCR method, whichis capable of differentiation of HBV viral genomic DNA andcccDNA, was used to quantify the total HBV cccDNA.The total HBV viral DNA was quantitated by real-time PCR usinga HBV diagnostic kit (PG Biotech, LTD, Shenzhen, China) described previously.RESULTS: For the first time, we measured the level of HBVDNA and cccDNA isolated from ten HBV patients’ liver biopsies and sera. in the liver biopsies, cccDNA was detected from all the biopsy samples. copy number of cccDNA ranged fromfrom 0.03 to 173.1 per cell, the copy number of total HBVDNA ranged from 0.08 to 3 717 per cell. The ratio of total HBV DNA to cccDNA ranged from 1 to 3 406. In the sera, cccDNA was only detected from six samples inclusive. HBV viral DNA was detected from all ten samples. to total HBV DNA ranged from 0 to 1.77% .To further investigated the the reason why cccDNA could only be detected insome patients’ sera, we performed longitudinal studies. theccDNA was detected from the patients’ sera with HBVreactivation but not from the patients’ sera without HBVreactivation. The level of cccDNA in the sera was correlated with ALT and viral load in the HBV reactivation patients. CONCLUSION: HBV cccDNA is actively transcribed and replicated in some patients’ hepatoo / tes, which is reflected by a high ratio of HBV total DNA vs cccDNA. Detection of cccDNA in the liver biopsy will provide an end-point for the anti-HBV therapy. the occurrence of cccDNA in the sera isan early signal of liver damage, which may be an onrimportant clinical parameter.