慢性HBV感染者肝脏HBV cccDNA含量相关因素分析

目的探讨慢性HBV感染者肝组织中HBV cccDNA含量与血清病毒标志物、HBV DNA及肝脏病理分级的关系,为临床评价抗病毒治疗效果及疗程确定提供理论依据。方法以2007年5月-2008年2月住院的30例慢性HBV感染者为研究对象,应用实时荧光定量聚合酶链反应（RT-PCR）方法检测患者肝组织中HBV cccDNA、肝组织总HBV DNA（HBV tDNA）和血清HBVDNA,同时用化学发光免疫分析法检测HBsAg、HBeAg定量,分析感染者肝组织内HBV cccDNA与肝组织内HBV DNA、血清HBVDNA、HBsAg及HBeAg定量水平之间的关系,并比较肝组织中HBV cccDNA含量与肝脏病理炎症和纤维化分级的关系。采用Pear-son简单相关和Spearman等级相关法进行相关性分析。结果 30例慢性HBV感染者肝组织中均可检出HBV cccDNA,范围在3.15×103～1.06×107拷贝/mg;肝组织cccDNA定量与肝组织总HBV DNA定量呈正相关（r=0.375,P〈0.05）,与血清HBV DNA无相关性（r=0.174,P〉0.05）;肝组织中HBV cccDNA水平与血清HBsAg定量呈高度正相关（r=0.562,P〈0.001）,而与血清HBeAg定量无相关性（r=0.152,P〉0.05）。肝组织cccDNA定量与肝组织炎症活动度（G）及纤维化程度（S）无相关性（r=0.082,P〉0.05）。结论慢性HBV感染者肝组织内HBV cccDNA成稳定的中等水平复制;血清HBV DNA载量不能直接代表其肝组织中的HBV cccDNA水平;血清HBsAg定量可作为反映肝组织中HBV cccDNA水平的指标。     

外周血单核细胞中HBV cccDNA检测的意义及进展

HBV在复制过程中存在着共价闭合环状DNA(cccDNA)形式,cccDNA是HBV复制的原始模板,是HBV持续感染的主要原因,也是HBV一个重要生物活性指标。HBV是嗜肝病毒,但可能存在肝外感染,有研究表明,外周血单核细胞(PBMC)中可以检测到HBV cccDNA。归纳了PBMC中HBV cccDNA在乙型肝炎患者肝移植术后及抗病毒治疗后HBV复发、HBV母婴传播中的预测作用,以及其参与HBV肝外感染的可能机制。由此可见,PBMC HBV cccDNA在HBV的治疗及研究中有重要意义。     

Intracellular levels of hepatitis B virus DNA and pregenomic RNA in peripheral blood mononuclear cells of chronically infected patients

Summary.  It remains uncertain whether hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) and pregenomic RNA (pgRNA) can be detected in the serum or peripheral blood mononuclear cells (PBMC) of patients with chronic hepatitis B (CHB) infection. We examined HBV cccDNA and pgRNA in the serum and PBMC, and investigated the effect of lamivudine therapy on the viral loads in the PBMC of CHB patients. Paired serum and PBMC samples from 50 treatment-naïve CHB patients [25 hepatitis B e antigen (HBeAg) positive and 25 HBeAg negative] were quantified for total HBV DNA, cccDNA and pgRNA by real time polymerase chain reaction. HBV cccDNA and pgRNA were below the lower detection limit in all serum samples, and in 84% of PBMC. HBV DNA ( r  = 0.889, P  <   0.001) and pgRNA ( r  = 0.696, P  <   0.001) in PBMC correlated with the HBV DNA in serum. In the longitudinal study, 30 patients treated with lamivudine therapy for a median duration of 34 weeks (range 12–48 weeks) were examined. The median HBV DNA reduction in PBMC before and after treatment was 1.318 (range −0.471 to 3.846) log units, which was significantly lower than serum HBV DNA reduction [3.371 (range −0.883 to 9.454) log units, P  <   0.05]. HBV cccDNA and pgRNA were undetectable in the serum of CHB patients. HBV viral loads in PBMC correlated with serum HBV DNA. Lamivudine therapy had less effect on the HBV viral loads in PBMC compared with the serum viral loads.     

慢性乙型肝炎新型治疗药物研究进展

慢性乙型肝炎(慢乙肝)治疗的理想目标是功能性治愈。目前药物抗病毒治疗可以抑制病毒复制,减轻或消除肝脏病理损害,有效阻止向肝硬化和肝癌的进展,但不能清除HBs Ag和病毒库,所以难以达到临床治愈(或功能性治愈)。因此,须要针对HBV生命周期以及调节免疫系统研发新型抗病毒药物。近年来,HBV受体的发现以及HBV感染细胞体外培养模型的初步建立有利于研发潜在的抗病毒表面抗原或提高病毒特异性细胞免疫等宿主抗病毒药物,包括抑制HBsAg合成和病毒库的清除等。由此相信未来慢乙肝的功能性治愈可以通过联合免疫调节、抗病毒(HBV DNA、HBsAg)和共价闭合环状DNA抑制剂等治疗方案来现实。     

乙型肝炎病毒cccDNA定量与乙型肝炎临床及病理关系

目的探讨慢性乙型肝炎（CHB）肝组织HBVcccDNA定量与乙型肝炎的关系。方法分别采用荧光定量PCR、酶联免疫吸附分析法（ELISA）检测48例CHB肝组织HBVcccDNA定量、肝组织和血清HB VDNA定量、乙型肝炎病毒标志物。同时用链霉菌抗生素蛋白-过氧化物酶连接法（SP）检测肝细胞中HBcAg表达。分析肝组织HBVcccDNA与组织和血清HBV DNA、HBeAg、肝细胞内HBcAg水平及肝脏炎症活动度的关系.结果1．肝组织HBVcccDNA定量与组织和血清HBV DNA定量呈正相关（r=0．837，P〈0．001；r=0．627，P〈0．005）；2．肝组织HBV cccDNA定量与肝细胞内HBcAg半定量呈正相关（r=0．618，P〈0．005）；3．肝组织HBV cccDNA定量与肝脏炎症活动度尤明显相关（P〉0．05）：4．HBeAg阳性较抗-HBe阳性患者肝组织HBV cccDNA定量、肝组织和血清HBV DNA定量高（P〈0．05）。结论荧光定量PCR法检测肝组织HBV cccDNA定量是评价HBV复制最直接可靠的指标，在CHB的诊断和抗病毒治疗中有重要意义。但与肝组织炎症无明显相关。     

Persistence of cccDNA during the natural history of chronic hepatitis B and decline during adefovir dipivoxil therapy

BACKGROUND & AIMS: Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) is a unique episomal replicative intermediate responsible for persistent infection of hepatocytes. Technical constraints have hampered the direct study of cccDNA maintenance and clearance mechanisms in patients. The aim of this study was to develop a sensitive and specific assay for quantifying cccDNA in biopsy samples from chronic hepatitis B patients during different natural history phases and in patients undergoing antiviral therapy. METHODS: Intrahepatic cccDNA levels were quantified by a specific real-time PCR assay. Ninety-eight liver biopsy samples from patients in the major phases of the natural history of chronic hepatitis B and 32 pairs of samples from patients receiving adefovir dipivoxil (ADV) therapy were assessed. RESULTS: cccDNA was detected, at levels ranging over 3 orders of magnitude, in patients in different phases of the natural history of chronic hepatitis B. cccDNA levels were strongly correlated with levels of total intracellular HBV DNA and serum HBV DNA. Forty-eight weeks of ADV therapy resulted in a significant 0.8 log decrease in cccDNA copies/cell. Changes in cccDNA were correlated with a similar reduction in serum HBsAg titer but not with a decrease in the number of HBV antigen-positive cells during ADV treatment.CONCLUSIONS: cccDNA persists throughout the natural history of chronic hepatitis B, even in patients with serologic evidence of viral clearance. Long-term ADV therapy significantly decreased cccDNA levels by a primarily noncytolytic mechanism.     

HBV持续感染及其机制的研究进展

HBV属嗜肝DNA病毒科,可引起人类急性和慢性肝炎,甚至肝硬化、肝癌。目前的抗病毒药物因不能彻底清除肝细胞内HBV,故很难达到治愈的效果。近年来,HBV持续感染的机制受到广泛关注,主要涉及宿主与病毒两方面,从病毒方面展开,主要阐述了cccDNA、HBV颗粒和HBV自身组分维持HBV持续感染的相关研究进展。     

Hepatitis B Virus DNA Integration and Clonal Expansion of Hepatocytes in the Chronically Infected Liver

Human hepatitis B virus (HBV) can cause chronic, lifelong infection of the liver that may lead to persistent or episodic immune-mediated inflammation against virus-infected hepatocytes. This immune response results in elevated rates of killing of virus-infected hepatocytes, which may extend over many years or decades, lead to fibrosis and cirrhosis, and play a role in the high incidence of hepatocellular carcinoma (HCC) in HBV carriers. Immune-mediated inflammation appears to cause oxidative DNA damage to hepatocytes, which may also play a major role in hepatocarcinogenesis. An additional DNA damaging feature of chronic infections is random integration of HBV DNA into the chromosomal DNA of hepatocytes. While HBV DNA integration does not have a role in virus replication it may alter gene expression of the host cell. Indeed, most HCCs that arise in HBV carriers contain integrated HBV DNA and, in many, the integrant appears to have played a role in hepatocarcinogenesis. Clonal expansion of hepatocytes, which is a natural feature of liver biology, occurs because the hepatocyte population is self-renewing and therefore loses complexity due to random hepatocyte death and replacement by proliferation of surviving hepatocytes. This process may also represent a risk factor for the development of HCC. Interestingly, during chronic HBV infection, hepatocyte clones detected using integrated HBV DNA as lineage-specific markers, emerge that are larger than those expected to occur by random death and proliferation of hepatocytes. The emergence of these larger hepatocyte clones may reflect a survival advantage that could be explained by an ability to avoid the host immune response. While most of these larger hepatocyte clones are probably not preneoplastic, some may have already acquired preneoplastic changes. Thus, chronic inflammation in the HBV-infected liver may be responsible, at least in part, for both initiation of HCC via oxidative DNA damage and promotion of HCC via stimulation of hepatocyte proliferation through immune-mediated killing and compensatory division.     

Hepatitis B in renal transplant recipients: An assessment of the relationship of viral replication to liver pathology

To determine the natural history of hepatitis B virus (HBV) infection in renal transplant recipients, 16 recipients who remained chronic HBsAg carriers were followed for 2–15 years by assaying hepatitis Be antigen (HBeAg) and hepatitis B viral DNA (HBV DNA). The results were compared with sequential liver biochemistry and histology. Similarly, nine HBsAg-negative renal transplant patients were studied for up to 10 years. It was found that different patterns of HBV replication were described in a majority of long-term HBsAg-positive renal transplant patients with intermittent virus replication being particularly common. A minority of patients with viral replication showed co-existing elevated transaminases. Development of liver disease was more common among HBsAg-positive patients, but when the various patterns of infection were correlated with long-term outcome, no one pattern was clearly more predictive of an adverse outcome.     

Recent Progress and Future Prospective in HBV Cure by CRISPR/Cas

Hepatitis B virus (HBV) infection remains an important issue of global public health. Although current antiviral therapy has dramatically reduced the mortality and morbidity of chronic hepatitis B (CHB), it fails to cure it. Rebound viremia often occurs after stopping antiviral therapy. Persistent HBV covalently closed circular DNA (cccDNA) and integrated DNA under antiviral therapy form the major barrier to eradication of HBV infection. CRISPR-mediated genome editing has emerged as a promising therapeutic approach to specifically destroy persistent HBV genomes, both cccDNA and integrated DNA, for HBV cure. However, the cleavage of integrated HBV DNA by CRISPR-Cas9 will cause double-strand break (DSB) of host genome, raising a serious safety concern about genome instability and carcinogenesis. The newly developed CRISPR-derived base editors (BEs), which fuse a catalytically disabled nuclease with a nucleobase deaminase enzyme, can be used to permanently inactivate HBV genome by introducing irreversible point mutations for generation of premature stop codons without DSBs of host genome. Although promising, CRISPR-mediated base editing still faces daunting challenges before its clinical application, including the base-editing efficacy, the off-target effect, the difficulty in finding conserved target HBV sequences, and in vivo delivery efficiency. Several strategies have been adopted to optimize the efficiency and specificity of CRISPR-BEs and to improve in vivo delivery efficacy through novel viral and non-viral delivery approaches. Particularly, the non-viral delivery of Cas9 mRNA and ribonucleoprotein by lipid nanoparticles exhibits attractive potential for liver-targeted delivery in clinical. Along with all progress above, the CRISPR-mediated gene therapy will ultimately achieve HBV cure.     

Role of viral factors in the natural course and therapy of chronic hepatitis B

Hepatitis B virus (HBV) infection is a global health problem that causes a wide spectrum of liver disease, including acute or fulminant hepatitis, inactive carrier state, chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). The pathogenesis of hepatocyte damage associated with HBV is mainly through immune-mediated mechanisms. On the basis of the virus and host interactions, the natural history of HBV carriers who are infected in early life can be divided into four dynamic phases. The frequency, extent, and severity of hepatitis flares or acute exacerbation in the second immune clearance and/or fourth reactivation phase predict liver disease progression in HBV carriers. In the past decade, hepatitis B viral factors including serum HBV DNA level, genotype, and naturally occurring mutants predictive of clinical outcomes have been identified. The higher the serum HBV DNA level after the immune clearance phase, the higher the incidence of adverse outcomes over time. In addition, high viral load, genotype C, basal core promoter mutation, and pre-S deletion correlate with increased risk of cirrhosis and HCC development. As to the treatment of chronic hepatitis B, patients with high HBV DNA level and genotype C or D infection are shown to have a worse response to interferon therapy. In conclusion, serum HBV DNA level, genotype, and naturally occurring mutants are identified to influence liver disease progression and therapy of chronic hepatitis B. More investigations are needed to clarify the molecular mechanisms of the viral factors involved in the pathogenesis of each stage of liver disease and the response to antiviral treatments.     

New therapies for chronic hepatitis B

Approximately 350 million people worldwide are chronically infected with hepatitis B virus (HBV), representing a significant public health challenge. Nucleos/tide analogues (NUCs) and interferon alpha (IFNα), the current standard of care for chronic infection, aim at preventing progression of the disease to cirrhosis, hepatocellular carcinoma (HCC) and death. However, in contrast to the case of hepatitis C virus infection, in which novel antiviral drugs cure the vast majority of treated patients, in regard to HBV, cure is rare due to the unusual persistence of viral DNA in the form of covalently closed circular DNA (cccDNA) within the nucleus of infected cells. Available therapies for HBV require lifelong treatment and surveillance, as reactivation frequently occurs following medication cessation and the occurrence of HCC is decreased but not eliminated, even after years of successful viral suppression. Progress has been made in the development of new therapeutics, and it is likely that only a combination of immune modulators, inhibitors of gene expression and replication and cccDNA‐targeting drugs will eradicate chronic infection. This review aims to summarize the state of the art in HBV drug research highlighting those agents with the greatest potential for success based on in vitro as well as on data from clinical studies.     

Guidelines for avoiding risks resulting from discontinuation of nucleoside/nucleotide analogs in patients with chronic hepatitis B

Nucleoside/nucleotide analogs (NUC) can lead to rapid reduction in hepatitis B virus (HBV) DNA levels in blood and normalization of alanine aminotransferase levels in many patients. They also provide histological improvement which results in a reduction in liver carcinogenesis. However, it is difficult to completely remove viruses even by NUC and there are some problems such as emergence of resistant strains and hepatitis relapse resulting from discontinuation of treatment. One of the reasons for this is that NUC reduce the HBV DNA level in blood but have almost no effects on the HBV cccDNA level in hepatocyte nuclei, which are the origins of HBV replication, and HBV cccDNA remains for a long period. For treatment with NUC in patients with hepatitis B, it is considered that NUC should not be easily discontinued because discontinuation often results in hepatitis relapse. However, it has not been clearly revealed when and how hepatitis relapses after discontinuation. Although some patients do not experience hepatitis relapse after discontinuation of NUC, or experience only mild relapse and finally achieve a stable condition, it has not been established how to identify such patients efficiently. We performed research to investigate characteristics of the course after discontinuation of treatment and definition of hepatitis relapse and estimate the relapse rate. “Guidelines for avoiding risks resulting from discontinuation of NUCs 2012” is summarized based on the study results. Because the guidelines are written in Japanese, we explain them in English as a review article.     

Hepatocellular carcinoma: The virus or the liver?

Hepatocellular carcinoma (HCC) represents a major public health problem being one of the most common causes of cancer-related deaths worldwide. Hepatitis B (HBV) and C viruses have been classified as oncoviruses and are responsible for the majority of HCC cases, while the role of hepatitis D virus (HDV) in liver carcinogenesis has not been elucidated. HDV/HBV coinfection is related to more severe liver damage than HBV mono-infection and recent studies suggest that HDV/HBV patients are at increased risk of developing HCC compared to HBV mono-infected patients. HBV is known to promote hepatocarcinogenesis via DNA integration into host DNA, disruption of molecular pathways by regulatory HBV x (HBx) protein and excessive oxidative stress. Recently, several molecular mechanisms have been proposed to clarify the pathogenesis of HDV-related HCC including activation of signalling pathways by specific HDV antigens, epigenetic dysregulation and altered gene expression. Alongside, ongoing chronic inflammation and impaired immune responses have also been suggested to facilitate carcinogenesis. Finally, cellular senescence seems to play an important role in chronic viral infection and inflammation leading to hepatocarcinogenesis. In this review, we summarize the current literature on the impact of HDV in HCC development and discuss the potential interplay between HBV, HDV and neighbouring liver tissue in liver carcinogenesis.