血清病毒检出核苷(酸)类似物耐药突变的慢性乙肝患者PBMCs中HBV cccDNA基因突变特点分析

Genetic mutation analysis of HBV covalently closed circular DNA in peripheral blood mononuclear cells from chronic hepatitis B patients with nucleos(t)ide analog-resistant mutations in serum virions

目的分析经核苷(酸)类似物治疗并已在血清病毒中产生耐药基因突变的慢性乙肝患者外周血单个核细胞(PBMCs)中HBV共价闭合环状DNA(cccDNA)反转录酶(RT)区的基因突变特点。方法收集2010年7月-2011年8月于解放军302医院住院的慢性乙肝患者30例,均经6个月以上的核苷(酸)类似物抗病毒治疗并已在血清中检测到耐药相关突变。采集与血清检测同一时间点的全血标本30份并分离PBMCs,提取总DNA,以不降解质粒的ATP依赖的DNA酶(PSAD)消化+滚环扩增+跨缺口PCR方法扩增HBV cccDNA的RT区,分析9个位点的核苷(酸)类似物耐药相关变异。结果 30份样本中,16例检出HBV cccDNA,检出率为53.3%,PBMCs中HBV cccDNA检出率与HBeAg阳性率、血清ALT水平及血清HBVDNA载量均无显著相关性。在16例HBV cccDNA检出者中,B基因型5例,占31.3%,C基因型11例,占68.8%,与血清HBV基因分型结果一致。但是,与血清HBV均检出耐药突变株不同,16例PBMCs cccDNA中检出的病毒均是无核苷(酸)类似物耐药相关突变的野生株。结论在经核苷(酸)类似物治疗的慢性乙肝患者血清中HBV DNA产生耐药突变的情况下,PBMCs中HBV cccDNA仍以原始野生株为优势种群,推测PBMCs可能是体内HBV野生株的"存储库"。

Objective To analyze the characteristics of genetic mutations in reverse-transcriptase（RT） domain of HBV covalently closed circular DNA（cccDNA） in peripheral blood mononuclear cells（PBMCs） obtained from chronic hepatitis B（CHB） patients with drug-resistant mutations in serum virions during nucleoside/nucleotide analog（NA） therapy.Methods A total of 30 CHB patients admitted to 302 Hospital of PLA from July 2010 to August 2011 were included in this study.All the patients were confirmed to harbor the drug-resistant mutations in serum virions during an NA therapy longer than 6 months.Total DNA was extracted from PBMCs isolated from 30 whole blood samples at the same time point as that of serum analysis.Plasmid-safe ATPdependent DNase（PSAD） digestion in combination with rolling circle amplification and gap-spanning semi-nested PCR were used to amplify the RT region of HBV cccDNA.NA-resistant-associated mutations were analyzed at nine sites.Results HBV cccDNA was efficiently amplified in 16 out of 30（53.3%） PBMC samples,and the detection rate was not correlated with HBeAg-positive rate,serum ALT level or HBV DNA load.Five of 16（31.3%） patients were sustained to have genotype B HBV infection,and 11 of 16 （68.8%） were of genotype C HBV infection,and the result was consistent with the genotyping results using serum HBV.Different from drug-resistant mutations detected in the serum virions,the viruses detected in HBV cccDNA of 16 PBMC samples were all wildtype viruses without NA-resistant-associated mutations in RT region.Conclusions During NA antiviral treatment,if drug-resistant mutations occur in serum HBV DNA of CHB patients,the dominant species of HBV cccDNA in PBMCs from the same patient is still the original wild-type strains.It is speculated that PBMCs might be the potential ＂repository＂ of HBV wild-type strain in vivo.