乙型肝炎病毒共价闭合环状DNA与松弛环状DNA对核苷（酸）类药物耐药变异的比较

Comparison of drug resistance mutations associated with hepatitis B virus covalently closed circular DNA and relaxed circular DNA

目的了解肝细胞内HBV共价闭合环状DNA（HBV cccDNA）核苷（酸）类药物耐药变异的情况，并比较其与松弛环状DNA（rcDNA）耐药变异的异同。方法取40例慢性HBV感染肝移植患者的部分肝组织，采用十二烷基硫酸钠一蛋白质沉淀法结合DNA提取试剂盒分离提取肝内的HBV cccDNA和rcDNA。将抽提产物用不降解质粒的ATP依赖DNA酶酶切纯化后，用跨HBV基因组双链缺口并涵盖常见核苷类耐药位点（rt169～rt250）的引物行单轮PCR或套式PCR选择性扩增cccDNA。另用不跨双缺口的引物PCR扩增肝组织内的HBV rcDNA和患者肝移植术前的血清HBVrcDNA。用直接测序法对上述扩增产物进行基因测序并分析核苷（酸）类药物耐药位点的检出情况。结果40例患者中，31例肝组织内检测到HBVcccDNA，35例肝组织检测到HBVrcDNA，21例肝移植术前血清中检测到HBVrcDNA。测序结果显示，2例肝组织内cccl）NA、rcDNA和血清rcDNA均检测到rtM204I变异；有2例患者肝内cccDNA、rcDNA分别存在rtM204I、rtQ215H变异，而血清rcDNA未检测到相应变异；3例血清中分别存在rtM204V、rtM204V、rtV173L＋rtL180M＋rtM204V变异，而肝内cccDNA和rcDNA未检测到相应变异。结论慢性HBV感染者肝细胞内cccDNA可出现核苷（酸）类药物耐药变异，且肝组织内的cccDNA、rcDNA耐药变异株与血清中的rcDNA耐药变异株不完全一致。

Objective To detect nucleos（t）ide-resistance mutations in hepatitis B virus （HBV） covalently closed circular DNA （cccDNA） isolated from hepatocytes of patients with chronic HBV infection and to analyze the correlation between the mutations found in cccDNA and relaxed circular DNA （rcDNA）. Methods Forty patients with chronic HBV infection were investigated. Pre- operation serum samples and non-tumor liver tissues were collected. Intrahepatic HBV cccDNA and rcDNA were selectively extracted by co-precipitation of sodium dodecyl sulphate-protein and QIAamp DNA Mini Kit, and further purification with plasmid-safe ATP-dependent DNase （PSAD）. Thereafter, cccDNA were amplified by selective polymerase chain reaction （PCR） or nested PCR using the primers spanning both the two gaps in HBV genome and covering the common mutations associated with nucleoside analogues resistance （rt169- rt250）. Intrahepatic HBV rcDNA and pre-operation serum HBV rcDNA were also extracted and then amplified by PCR. The PCR products were then purified and sequenced. Results Among the 40 patients, intrahepatic HBV cccDNA were detected in 31 patients, and HBV rcDNA were detected in liver samples of 35 patients and pre-operation serum samples of 21 patients. The PCR products amplified from these samples were all successfully sequenced, rtM204I mutation was detected in intracellular HBV cccDNA, reDNA and serum HBV rcDNA in 2 patients. Both rtM204I and rtQ215H were detected in intrahepatic HBV cceDNA and rcDNA in 2 patients, while no corresponding mutation was observed in serum HBV rcDNA of these two patients. Three variants including rtM204V, rtM204V and rtV173Lq-rtL180Mq-rtM204V were detected in serum HBV rcDNA in 3 patients, while corresponding mutants were not detected in intracellular HBV cccDNA or rcDNA of these patients. Conclusions The results suggest that antiviral nucleos（t） ide resistance mutations can be found in HBV cccDNA in chronic hepatitis B patients. The dominant resistant mutation found in intrahepatic HBV cceDNA/rcDNA may be different from that in serum HBV rcDNA.