比较不同血清型AAV携带HBV基因组建立乙肝小鼠模型效果

近年来,用8型腺相关病毒携带1.3拷贝HBV(Hepatitis B virus)基因组建立的HBV持续感染小鼠模型受到越来越多的关注。本研究比较了除AAV8之外的其他4种血清型重组腺相关病毒(Recombinant adeno-associated virus,rAAV)建立乙肝小鼠模型效果。首先,将携带1.3拷贝ayw亚型HBV基因组的1型、2型、5型、8型、9型腺相关病毒分别以1×10~(11) vg/只(Viral genome,vg)的剂量尾静脉注射C57BL/6J小鼠;利用ELISA方法监测小鼠血清中HBeAg和HBsAg表达水平;用定量PCR方法检测小鼠血清和肝脏中HBV DNA拷贝数;用免疫组化方法检测小鼠肝脏中HBc Ag的表达;用HE染色检测小鼠肝脏病理变化。结果显示,在持续8周中,5组小鼠血清中都检测到HBeAg和HBsAg的表达,血清和肝脏中均检测到HBV DNA的存在。HBeAg、HBsAg、HBV DNA表达水平高低依次为AAV8AAV9AAV1AAV5AAV2。5组小鼠用免疫组化方法都检测到肝脏中HBcAg表达,HE染色病理检测均观察到不同程度的肝损伤。本研究扩大了能用于建立乙肝小鼠持续感染模型可选择的AAV载体种类,发现虽然AAV1、2、5、9的建模效果不如AAV8,但它们都可以介导建立持续感染的乙肝小鼠模型,建模效果依次为AAV8AAV9AAV1AAV5AAV2。其中AAV9介导的建模效果与AAV8载体最为接近,可以替代AAV8载体用于有效地建立HBV持续感染的小鼠模型。     

Characterization of RNA transcripts and virally coded proteins synthesized in mouse fibroblasts transfected with hepatitis B DNA: HBeAg synthesis in HBcAg-negative cells with active core-antigen genes

A line of mouse cells expressing hepatitis B virus (HBV) surface and ‘e’ antigens identical in their physico-chemical properties to antigens from patients infected with HBV was isolated after transfection of 3T3 ceils with cloned HBV DNA. The studies reported here indicate that the ceils contain uninterrupted copies of the entire HBV genome which are unmethylated on CCGG sites and have no gross deletions or rearrangements. The entire core region is transcribed into polyadenylated RNAs large enough to serve as messengers for production of viral core antigen (HBcAg) yet no HBcAg can be detected. This suggests that the ceils produce a primary translation product copied from the HBcAg messenger which either cannot assume the proper configuration for display of HBcAg determinants or is rapidly converted to HBeAg by proteolysis.     

Two approaches to construct mammalian expression vector of shRNA to reduce expression and replication of HBV in vitro

Two approaches have been developed to construct plasmids that mediate RNA interference to inhibit the replication and expression of HBV in 2.2.15 cell. The overlapping PCR extension and restriction enzyme-digestion were used to generate DNA fragments encoding designed shRNA based on sequences of ORF C of HBV genome. The pU6 derived vectors were constructed to develop plasmid based shRNA delivery systems termed pU6/HBVi. There were significant reductions in the expression of HBsAg and HBeAg between cells transfected with pU6/HBVi and control groups (as to HBsAg: P < 0. 01; and HBeAg: P < 0. 01). Consistently, the HBV DNA copies were reduced from 2.71 x 10(7) to <5 x 10(2) copies with or without pU6/HBVi. These results suggested that shRNA delivery by recombinant plasmids harboring shRNA encoding DNA fragment of interest generated either by overlapping PCR extension or restriction enzyme-digestion, could inhibit expressions of viral proteins and reduce viral replications. The pU6 derived plasmids might be a useful shRNA delivery system in mammalian cells. In addition, we found siRNA based on stealth 2311 was a potent RNAi target of HBV genome.     

Stable expression and integrated hepatitis B virus genome in a human hepatoma cell line

HepG2.2.15 cell is a widely used cell model for studying HBV (hepatitis B virus) in vitro. In these cells, the HBV genome is integrated in several sites of HepG2 cellular DNA. These multiple copies may have some influence on the cellular processes. We constructed a new plasmid, pSEH-Flag-HBV, and transfected it into HepG2 cells, and then screened it with hygromycin. We then used ELISA, PCR, and RT-PCR to detect the expression of HBV in these cell lines. A cell line that stably expressed hepatitis B e antigen (HBeAg) and hepatitis B surface antigen (HBsAg) was established. Using Southern blotting analysis, we found that the HBV genome was integrated as a single copy in the cellular DNA. This cell line will be a useful alternative model for HBV studies.     

用重组8型腺相关病毒载体介导的乙型肝炎病毒持续感染小鼠模型评价核苷类似物的抗病毒效果

探索用重组8型腺相关病毒载体携带1.3拷贝乙型肝炎病毒(rAAV8-1.3HBV)介导的HBV持续感染小鼠模型评价核苷酸类似物抗病毒药物的抗病毒效果.首先,通过将rAAV8-1.3HBV经尾静脉注射到30只C57BL/6小鼠体内,建立HBV持续感染模型并对模型成功率进行检测,将建模成功的27只小鼠随机分成6组.然后采取灌胃的方式给予不同剂量的抗病毒药物恩替卡韦(ETV)及拉米夫定(LAM),每日1次,连续l0d,后停药15d,同时设置生理盐水及空白对照组.其中ETV分为高剂量(1.0 mg/(kg·d))和低剂量(0.1 mg/(kg·d) 两组;LAM分为高剂量(500 mg/(kg·d)) 和低剂量(100 mg/(kg·d)) 两组.检测给药前后和停药前后小鼠模型血清中HBV DNA、HBeAg和HBsAg表达水平并比较变化情况.结果发现连续给药10d后,各给药组与生理盐水组相比,血清中HBV DNA水平均显著下降,具有统计学差异(P＜0.05).停药15d后,低剂量的ETV与LAM两组血清HBV DNA水平出现反弹,差异存在统计学意义(P＜0.05).在整个实验过程中,各组小鼠血清中HBeAg和HBsAg表达水平均未出现明显变化.上述结果表明,ETV和LAM能有效抑制模型小鼠中HBV病毒的复制,而对HBeAg和HBsAg表达水平无明显影响;提示AAV8-1.3HBV介导的HBV持续感染小鼠模型制备简单,成模率高,可有效体现出ETV和LAM抗HBV的作用效果,从而用于核苷酸类似物抗HBV药物的筛查.     

Immunocytochemical investigation of hepatitis B virus-associated antigens in cases of liver cirrhosis and HBsAg antigenemia and their relationship to development of hepatocellular carcinoma

Summary Using light and ultrastructural immunoperoxidase techniques, we examined the distribution of hepatitis B virus (HBV)-associated antigens and the subcellular localization of hepatitis B surface antigen (HBsAg) in liver biopsies of HBsAg—positive patients with cirrhosis. The localization patterns of HBsAg in hepatocytes were membranous, cytoplasmic, festoon and inclusion body types. Cytoplasmic and festoon types were seen more often than the membranous type in pseudolobules, and hepatitis B core antigen (HBcAg)—positive cells with cytoplasmic type were distributed in the periphery of pseudolobules with active inflammation. Immunoelectron microscopy in the cytoplasmic or festoon type of HBsAg showed immunoreaction in the cisternae and on virus-like particles in the cisternae in patients with hepatitis B e antigen (HBeAg) antigenemia. Simultaneous staining of HBsAg and HBcAg revealed that hepatocytes with cytoplasmic or festoon type of HBsAg contained HBcAg—immunoreactivity. The inclusion body type of HBsAg was characteristic of liver cirrhosis with hepatocellular carcinoma (HCC); the subcellular localization of HBsAg was seen in clusters of the endoplasmic reticulum around the nucleus, and HBsAg—immunoreactivity was observed on many virus-like particles in most of the cisternae in those with HBeAg antigenemia. These findings suggest that the synthesis of HBsAg is active in patients with liver cirrhosis and that the formation of HBV is also active in those with HBeAg antigenemia and that HBV may be retained more in cirrhotic livers with hepatocellular carcinoma after proliferation than in those without it.     

Rearrangement of the surface antigen gene of hepatitis B virus integrated in the human hepatoma cell lines.

The rearrangement of integrated HBV DNA sequences in three different hepatoma cell lines, huH-1, huH-2, KG-55-T from Japanese patients, were studied by blot hybridization using whole HBV genome or a HBsAg or HBcAg DNA as a probe. The characteristic existence of multiple integration sites of HBV DNA sequences in each HindIII-restricted hepatoma cell DNA was revealed by the HBV genome probe. Detection of the isolated HBsAg gene in the HindIII fragment indicates that the integration of HBV DNA was not always related to the maintenance of the whole viral genome, and that movement of the HBsAg gene to another location occurred by rearrangement. On the other hand, the presence of the HBV DNA sequence without the intact HBcAg gene was shown in some of the HindIII fragments, when the HBcAg gene, probe was used, but a HindIII fragment, containing only the HBcAg gene, was not detected so far. The absence of the intact HBcAg gene suggests that the viral genome may lose a part of the HBcAg gene in the process of integration. This is consistent with recent findings of Ogston et al. (1982) that in Woodchuck hepatocellular carcinoma viral sequences are extensively rearranged.     

用rAAV8-1.3HBV制备两种品系小鼠乙型肝炎病毒感染模型的比较研究

我们先前用rAAV8-1.3HBV静脉注射C57BL/6小鼠成功地制备了慢性乙型肝炎病毒(Hepatitis B virus,HBV)感染模型。为了探讨不同品系的小鼠对rAAV8-1.3HBV静脉注射是否具有不同反应,本研究比较了C57BL/6和BALB/c小鼠静脉注射重组病毒后外周血中HBV抗原和抗体水平、病毒载量和肝脏组织HBcAg表达情况,以及不同剂量重组病毒注射与这些指标的关系。将低(4×109 Viral genome,vg)、中(4×1010vg)和高(4×1011vg)三种剂量的rAAV8-1.3HBV通过尾静脉注射至C57BL/6和BALB/c小鼠,分别利用ELISA和荧光定量PCR方法检测血清中的HBV抗原、抗体水平以及HBV DNA,利用免疫组化检测肝脏组织HBcAg的表达。结果发现,对于C57BL/6小鼠,三种不同剂量rAAV8-1.3HBV注射均可造成100%小鼠出现HBV持续感染;血清HBsAg、HBeAg和HBV DNA以及肝组织HBcAg稳定表达超过8个月,其表达水平随重组病毒注射剂量的增加而升高,高剂量注射时可造成超过40%的肝细胞感染HBV,血清中HBV DNA可达105 IU/mL以上;未检测到针对HBV的抗体。对于BALB/c小鼠,三种不同剂量rAAV8-1.3HBV注射也可造成100%小鼠出现HBV持续感染;血清HBeAg和HBV DNA以及肝组织HBcAg稳定表达超过8个月,但是血清HBsAg在重组病毒注射2周之后显著下降甚至消失;在中剂量注射组的BALB/c小鼠血清中检测到低水平的Anti-HBs;血清HBeAg和肝组织HBcAg的表达水平随重组病毒注射剂量的增加而增高,并且各剂量组表达水平均高于C57BL/6小鼠,高剂量注射时可造成超过50%的肝细胞感染HBV。本研究表明,低至4×109 vg剂量的rAAV8-1.3HBV注射即可造成C57BL/6和BALB/c两种品系小鼠出现HBV持续感染,并且HBV复制水平随重组病毒注射剂量增加而增高;BALB/c小鼠对HBV的免疫反应强于C57BL/6小鼠,可以产生针对HBsAg的体液免疫反应而使血清HBsAg转阴,但无法清除携带HBV的肝细胞。     

Enhanced HBsAg Synthesis Correlates with Increased Severity of Fibrosis in Chronic Hepatitis B Patients

Background and Aims

Little is known about whether low serum HBsAg levels result from impaired HBsAg synthesis or a reduced number of hepatocytes caused by advanced liver fibrosis. Therefore, we investigated the capacity for HBsAg synthesis in a cross-sectional cohort of treatment-naïve chronic hepatitis B patients.

Methods

Chronic hepatitis B patients (n = 362) were enrolled; liver biopsies were performed and liver histology was scored, and serum HBsAg and HBV DNA levels were investigated. In the enrolled patients, 183 out of 362 have quantitative serum HBsAg levels. Tissue HBsAg was determined by immunohistochemistry.

Results

A positive correlation between serum HBsAg and HBV DNA levels was revealed in HBeAg(+) patients (r = 0.2613, p = 0.0050). In HBeAg(+) patients, serum HBsAg and severity of fibrosis were inversely correlated (p = 0.0094), whereas tissue HBsAg levels correlated positively with the stage of fibrosis (p = 0.0280). After applying the mean aminopyrine breath test as a correction factor, adjusted serum HBsAg showed a strong positive correlation with fibrosis severity in HBeAg(+) patients (r = 0.5655, p<0.0001). The adjusted serum HBsAg values predicted ‘moderate to severe’ fibrosis with nearly perfect performance in both HBeAg(+) patients (area under the curve: 0.994, 95% CI: 0.983–1.000) and HBeAg(−) patients (area under the curve: 1.000, 95% CI: 1.000–1.000).

Conclusions

Although serum HBsAg levels were negatively correlated with fibrosis severity in HBeAg(+) patients, aminopyrine breath test-adjusted serum HBsAg and tissue HBsAg, two indices that are unaffected by the number of residual hepatocytes, were positively correlated with fibrosis severity. Furthermore, adjusted serum HBsAg has an accurate prediction capability.     

DNA immunization with fusion of CTLA-4 to hepatitis B virus (HBV) core protein enhanced Th2 type responses and cleared HBV with an accelerated kinetic

Background

Typically, DNA immunization via the intramuscular route induces specific, Th1-dominant immune responses. However, plasmids expressing viral proteins fused to cytotoxic T lymphocyte antigen 4 (CTLA-4) primed Th2-biased responses and were able to induced effective protection against viral challenge in the woodchuck model. Thus, we addressed the question in the mouse model how the Th1/Th2 bias of primed immune responses by a DNA vaccine influences hepatitis B virus (HBV) clearance.

Principal Findings

Plasmids expressing HBV core protein (HBcAg) or HBV e antigen and HBcAg fused to the extracellular domain of CTLA-4 (pCTLA-4-HBc), CD27, and full length CD40L were constructed. Immunizations of these DNA plasmids induced HBcAg-specific antibody and cytotoxic T-cell responses in mice, but with different characteristics regarding the titers and subtypes of specific antibodies and intensity of T-cell responses. The plasmid pHBc expressing HBcAg induced an IgG2a-dominant response while immunizations of pCTLA-4-HBc induced a balanced IgG1/IgG2a response. To assess the protective values of the immune responses of different characteristics, mice were pre-immunized with pCTLA-4-HBc and pHBc, and challenged by hydrodynamic injection (HI) of pAAV/HBV1.2. HBV surface antigen (HBsAg) and DNA in peripheral blood and HBcAg in liver tissue were cleared with significantly accelerated kinetics in both groups. The clearance of HBsAg was completed within 16 days in immunized mice while more than 50% of the control mice are still positive for HBsAg on day 22. Stronger HBcAg-specific T-cell responses were primed by pHBc correlating with a more rapid decline of HBcAg expression in liver tissue, while anti-HBs antibody response developed rapidly in the mice immunized with pCTLA-4-HBc, indicating that the Th1/Th2 bias of vaccine-primed immune responses influences the mode of viral clearance.

Conclusion

Viral clearance could be efficiently achieved by Th1/Th2-balanced immune response, with a small but significant shift in T-cell and B-cell immune responses.     

从乙型肝炎病毒表面抗原阳性母亲流产的胎儿查出乙型肝炎病毒标志

应用Southern blot杂交试验检测HBsAg及HBeAg均阳性母亲流产的9例胎儿肝细胞中HBV DNA的存在状态,并与其HBV血清学、免疫电镜及肝脏免疫组织化学的结果相比较。结果在3例胎肝高分子DNA中检出了整合的HBV DNA顺序,且此3例HBV DNA整合到胎肝细胞基因组并无特定部位,提示为随机整合。3例中2例的血清及肝匀浆都检出HBsAg颗粒,其胎肝细胞胞浆HBsAg也阳性;另1例受HBV感染的唯一标志是在胎肝细胞中存在着整合的HBVDNA。此外,另1例则仅胎肝细胞中HBsAg阳性而无整合的HBV DNA。在胎肝细胞中检出整合的HBV DNA进一步证实HBV子宫内传播途径的存在。     

Persistence of the Recombinant Genomes of Woodchuck Hepatitis Virus in the Mouse Model

Hydrodynamic injection (HI) with a replication competent hepatitis B virus (HBV) genome may lead to transient or prolonged HBV replication in mice. However, the prolonged HBV persistence after HI depends on the specific backbone of the vector carrying HBV genome and the genetic background of the mouse strain. We asked whether a genetically closely related hepadnavirus, woodchuck hepatitis virus (WHV), may maintain the gene expression and replication in the mouse liver after HI. Interestingly, we found that HI of pBS-WHV1.3 containing a 1.3 fold overlength WHV genome in BALB/c mouse led to the long presence of WHV DNA and WHV proteins expression in the mouse liver. Thus, we asked whether WHV genome carrying foreign DNA sequences could maintain the long term gene expression and persistence. For this purpose, the coding region of HBV surface antigen (HBsAg) was inserted into the WHV genome to replace the corresponding region. Three recombinant WHV-HBV genomes were constructed with the replacement with HBsAg a-determinant, major HBsAg, and middle HBsAg. Serum HBsAg, viral DNA, hepatic WHV protein expression, and viral replication intermediates were detected in mice after HI with recombinant genomes. Similarly, the recombinant genomes could persist for a prolonged period of time up to 45 weeks in mice. WHV and recombinant WHV-HBV genomes did not trigger effective antibody and T-cell responses to viral proteins. The ability of recombinant WHV constructs to persist in mice is an interesting aspect for the future investigation and may be explored for in vivo gene transfer.     

重组8型腺相关病毒介导HBV急性感染树鼩模型建立

目的利用重组8型腺相关病毒介导1.3拷贝HBV基因组（1.3HBV,ayw亚型）在树鼩肝脏表达,建立HBV急性感染树鼩模型。方法通过大腿内侧静脉注射将携带有1.3 HBV的重组8型腺相关病毒（recombi-nant adeno-associated virus 8,rAAV8-1.3HBV）导入树鼩肝脏,通过ELISA检测树鼩血清中HBsAg、HBeAg、HBsAb、HBeAb、HBcAb,荧光定量PCR检测树鼩肝脏和血清中HBV DNA,全自动生化分析仪检测血清中ALT水平,并观察感染后肝脏的病变情况。结果 HBV感染主要血清标志物1～2周内均检测阳性;30 d后肝组织仍可检测到病毒抗原阳性细胞;55 d时肝组织HBV DNA拷贝数仍可达到104～105;树鼩血清中HBV DNA拷贝数持续一个月高于正常组;肝组织炎细胞略增多,血清ALT水平持续升高。结论 rAAV8所携带的HBV基因组高效专一导入树鼩肝细胞并复制表达,成功建立HBV急性感染树鼩模型,为进一步探索rAAV8树鼩慢性感染模型打下一定的基础。     

Inhibition of HBV gene expression and replication by stably expressed interferon-alpha1 via adeno-associated viral vectors

Background

Interferon‐α2 (IFNα2) is routinely used for anti‐hepatitis B virus (HBV) treatment. However, the therapeutic efficiency is unsatisfactory, particularly in East Asia. Such inefficiency might be a result of the short half‐life, relatively low local concentration and strong side‐effects of interferons. Frequent and repeated injection is also a big burden for patients. In the present study, a single dose of vector‐delivered IFNα1 was tested for its anti‐HBV effects.

Methods

Adeno‐associated viral vector (AAV‐IFNα1) was generated to deliver the IFNα1 gene into hepatocytes. IFNα1, hepatitis B surface (HBsAg) and e (HBeAg) antigens were measured by enzyme‐linked immunosorbent assay and/or western blotting. The level of viral DNA was measured by quantitative real‐time polymerase chain reaction.

Results

AAV‐IFNα1 effectively transduced HBV‐producing cells (HepAD38) and mouse hepatocytes, where IFNα1 was expressed in a stable manner. Both intracellular and extracellular HBsAg and HBeAg were significantly reduced in vitro. In the HBV‐producing mice, the concentration of IFNα1 in the liver was eight‐fold higher than that in plasma. Compared with control groups, HBeAg/HBsAg antigen levels were reduced by more than ten‐fold from day 1–5, and dropped to an undetectable level on day 9 in the AAV‐IFNα1 group. Concurrently, the level of viral DNA decreased over 30‐fold for several weeks.

Conclusions

A single dose administration of AAV‐IFNα1 viral vector displayed prolonged transgene expression and superior antiviral effects both in vitro and in vivo. Therefore, the use of AAV‐IFNα1 might be a potential alternative strategy for anti‐HBV therapy. Copyright © 2008 John Wiley & Sons, Ltd.

     

Dried Blood Spot Sampling for Hepatitis B Virus Serology and Molecular Testing

Background & Aims

Dried blood spots (DBS) on filter paper have been successfully used to diagnose and monitor several infectious diseases. The aim was to investigate the performance of DBS in hepatitis B virus (HBV) diagnosis using commercial tests in comparison to standard methods.

Methods

Paired DBS and plasma samples were collected from 200 patients: 100 patients with HBsAg negative status and 100 patients with HBsAg positive status. In the latter patient, HBeAg reactivity was tested. Ten samples of anti-HBs were collected from people vaccinated against HBV. We also studied 50 patients with positive HBV DNA viral load in plasma and 10 HBV DNA negative patients. HBV genotypes and gene polymerase mutations were determined in 10 randomly selected HBV-infected patients. The DBS sample consisted of 50 µL of whole blood, i.e. a 12-mm paper card.

Results

The sensitivity thresholds of HBsAg and anti-HBs antibody were 0.30±0.08 IU/mL and 18.11±6.05 IU/mL, respectively, for DBS with 98% sensitivity and 100% specificity. Sensitivity was 98% and specificity 100% for the detection of HBV DNA on a blotter, considering an HBV DNA threshold of 914.1±157.8 IU/ml. Ten patients had an HBeAg positive status in plasma, all were detected positive using DBS. HBV genotyping and mutation detection were successfully performed on DBS, with full concordance between the 10 paired DBS and plasma samples.

Conclusion

This study shows DBS is a reliable alternative to plasma specimens for quantifying and detecting HBsAg, anti-HBs, HBeAg and genotyping. DBS may increase the opportunities for HBV testing and treatment follow-up in hard-to-reach individuals.