A chronic carrierlike state is established in nude mice injected with cloned hepatitis B virus DNA.

BALB/c nude mice were injected intrahepatically with hepatitis B virus (HBV) DNA prepared from recombinant plasmids. Hepatitis B surface antigen appeared in the circulation in 19 of 23 mice (82%) 3 to 20 weeks postinjection and persisted for more than 6 months in most animals. Hepatitis B e antigen appeared transiently in the circulation in 12 of the 23 mice (52%) within a few weeks after the appearance of hepatitis B surface antigen. Antibodies to the core, X, and/or polymerase gene products of HBV have also been observed in 14 (61%) of the mice. Histopathological examination of the livers at 7 months postinjection demonstrated that nearly half had characteristics consistent with chronic hepatitis. HBV DNA appeared to be integrated into host liver DNA. No evidence of viral replication was observed in sera or livers from these mice at 7 months postinjection. These results demonstrate that an HBV chronic carrierlike state can be established in mice and that such a model could be used to study host and virus factors important in the establishment and maintenance of HBV-associated chronic liver disease.     

Small rodent models of hepatitis B and C virus replication and pathogenesis

The narrow host range of infection supporting the long-term propagation of hepatitis B and C viruses is a major limitation that has prevented a more thorough understanding of persistent infection and t...     

HBV转基因小鼠--乙型肝炎研究的重要工具

HBV感染具有严格的种属特异性和组织亲嗜性,所以可用于研究的动物模型很少。随着转基因技术的出现和发展,人们通过研制转基因动物模型来研究病毒致病机理。把HBV的DNA或其片段转入小鼠受精卵建立起来的HBV转基因小鼠,已被广泛地应用于乙型肝炎的研究中,主要体现在以下3个方面：研究HBV的致病机制、与肝细胞癌的关系及寻找、评价治疗乙肝的方法。     

Hepatitis B virus splice-generated protein induces T-cell responses in HLA-transgenic mice and hepatitis B virus-infected patients

Hepatitis B virus splice-generated protein (HBSP), encoded by a spliced hepatitis B virus RNA, was recently identified in liver biopsy specimens from patients with chronic active hepatitis B. We investigated the possible generation of immunogenic peptides by the processing of this protein in vivo. We identified a panel of potential epitopes in HBSP by using predictive computational algorithms for peptide binding to HLA molecules. We used transgenic mice devoid of murine major histocompatibility complex (MHC) class I molecules and positive for human MHC class I molecules to characterize immune responses specific for HBSP. Two HLA-A2-restricted peptides and one immunodominant HLA-B7-restricted epitope were identified following the immunization of mice with DNA vectors encoding HBSP. Most importantly, a set of overlapping peptides covering the HBSP sequence induced significant HBSP-specific T-cell responses in peripheral blood mononuclear cells from patients with chronic hepatitis B. The response was multispecific, as several epitopes were recognized by CD8(+) and CD4(+) human T cells. This study provides the first evidence that this protein generated in vivo from an alternative reading frame of the hepatitis B virus genome activates T-cell responses in hepatitis B virus-infected patients. Given that hepatitis B is an immune response-mediated disease, the detection of T-cell responses directed against HBSP in patients with chronic hepatitis B suggests a potential role for this protein in liver disease progression.     

Immunopathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) infection is a non-cytopathic hepatotropic virus that can lead to severe liver disease including acute hepatitis, cirrhosis and hepatocellular carcinoma. Successful clearance of the virus as well as the establishment of liver disease is largely driven by a complex interaction between the virus and the host immune response. In this review, the immunological events, including both the innate and adaptive immune response are discussed in the setting of both acute and chronic HBV infection and liver disease.     

Genetic vaccination. Perspectives for the prevention and treatment of hepatitis B

Genetic vaccination by intramuscular injection of a plasmid vector encoding the hepatitis B virus surface antigen (HBsAg) induces antibodies in mice that are specific for the hepatitis B virus envelope proteins. The antibody titres were very high and remained constant for more than 6 months after a single injection. Transgenic (Tg) mice that constitutively express the HBsAg in the liver were used as a model for hepatitis B virus chronic carriers. Intramuscular injection of a plasmid encoding the HBsAg in Tg mice resulted in the complete clearance of circulating HBsAg and in the long-term control of transgene mRNA expression in hepatocytes. Genetic vaccination appears therefore as a promising method for both prevention and treatment of hepatitis B.     

Antibody to hepatitis B core antigen in chronic active hepatitis.

Antibody to hepatitis B core antigen (anti-HBc), which has been assumed to be a more sensitive indicator of hepatitis B virus replication than hepatitis B surface antigen (HBsAg), was detected in the sera of 26 of our 65 patients with HBsAg-negative chronic active hepatitis. Thus despite the absence of HBsAg the liver disease could be the consequence of chronic infection with hepatitis B virus in these patients. They differed, however, from a group of 35 patients with HBsAg-positive hepatitis in being older on average and having less active liver lesions. The two groups could represent either two stages of chronic infection with hepatitis B virus or two types of response to it.     

Aggravation of viral hepatitis by platelet-derived serotonin

More than 500 million people worldwide are persistently infected with hepatitis B virus or hepatitis C virus. Although both viruses are poorly cytopathic, persistence of either virus carries a risk of chronic liver inflammation, potentially resulting in liver steatosis, liver cirrhosis, end-stage liver failure or hepatocellular carcinoma. Virus-specific T cells are a major determinant of the outcome of hepatitis, as they contribute to the early control of chronic hepatitis viruses, but they also mediate immunopathology during persistent virus infection. We have analyzed the role of platelet-derived vasoactive serotonin during virus-induced CD8(+) T cell-dependent immunopathological hepatitis in mice infected with the noncytopathic lymphocytic choriomeningitis virus. After virus infection, platelets were recruited to the liver, and their activation correlated with severely reduced sinusoidal microcirculation, delayed virus elimination and increased immunopathological liver cell damage. Lack of platelet-derived serotonin in serotonin-deficient mice normalized hepatic microcirculatory dysfunction, accelerated virus clearance in the liver and reduced CD8(+) T cell-dependent liver cell damage. In keeping with these observations, serotonin treatment of infected mice delayed entry of activated CD8(+) T cells into the liver, delayed virus control and aggravated immunopathological hepatitis. Thus, vasoactive serotonin supports virus persistence in the liver and aggravates virus-induced immunopathology.     

Importance of markers of hepatitis B virus in alcoholic liver disease.

To determine the importance of the presence of serological markers of hepatitis B virus infection in patients with alcohol related liver disease we compared cumulative alcohol intake and clinical and histological features in patients with markers of hepatitis B virus infection and in those without. Hepatitis B surface antigen (HBsAg) was detected in five (2%) out of 285 patients studied and antibody to HBsAg (anti-HBs) in 41 (14%); one patient had antibody to hepatitis B core antigen alone. The combined prevalence of markers of hepatitis B virus infection was similar in patients with alcoholic cirrhosis (18%) and precirrhotic liver disease (13%). Two patients positive for HBsAg had histological features of both alcoholic liver disease and chronic active hepatitis, with stainable HBsAg. Patients with anti-HBs were, however, histologically indistinguishable from patients without markers, and the mean cumulative alcohol intake of patients with anti-HBs was similar to or even higher than that of patients with liver disease of comparable severity who had no evidence of previous infection. The presence of markers of hepatitis B virus infection was related to former residence in countries with a high prevalence of the infection and to previous parenteral treatment and blood transfusions. Infection with hepatitis B virus does not enhance the development of chronic liver disease in heavy drinkers, except in the small number who remain positive for HBsAg.     

慢性病毒性肝炎研究进展

近年,慢性病毒性肝炎研究领域有较大进展,慢性乙型肝炎病毒（HBV）感染,虽然有了应用广泛、历史较久、且效果较好的疫苗,但迄今仍是世界范围肝硬化和肝癌的主要诱因。传染途径可经产道、性接触和非肠道途径（包括静脉吸毒、血制品等）。成年病人有少有变慢性,但一岁以下患儿90％变成慢性肝炎。慢性肝损伤的临床表现可以是轻微的炎症重到晚期肝硬化,程度不等。α干扰素（IFNα）是治疗活动性肝炎的产宰药物,单核苷酸类药物（lamivudine和adefovir）也具有同样的疗效。晚期肝病和肝癌患者可进行移植,但异常伴发移植物的感染。乙型肝炎免疫球蛋白和新型抗病毒药物联合应用,可降低移植物感染的严重性。丙型肝炎病毒（HCV）在20世纪后期感染了大约1％的世界人口。这中RNA病毒非经口传播,绝大多数病人变成慢性肝炎,约20％逐渐演变成肝硬化或肝癌。用IFNα和病毒唑（Ribavirin）联合治疗,约40％病人的病理表现有所改善。肝移植对某些病例是适宜的,但移植物感染仍是悬而未决的问题,新发现的庚型肝炎病毒（HGV）和TT病毒目前认为并不引起严重的肝损害。     

Antibody Responses during Hepatitis B Viral Infection

Hepatitis B is a DNA virus that infects liver cells and can cause both acute and chronic disease. It is believed that both viral and host factors are responsible for determining whether the infection is cleared or becomes chronic. Here we investigate the mechanism of protection by developing a mathematical model of the antibody response following hepatitis B virus (HBV) infection. We fitted the model to data from seven infected adults identified during acute infection and determined the ability of the virus to escape neutralization through overproduction of non-infectious subviral particles, which have HBs proteins on their surface, but do not contain nucleocapsid protein and viral nucleic acids. We showed that viral clearance can be achieved for high anti-HBV antibody levels, as in vaccinated individuals, when: (1) the rate of synthesis of hepatitis B subviral particles is slow; (2) the rate of synthesis of hepatitis B subviral particles is high but either anti-HBV antibody production is fast, the antibody affinity is high, or the levels of pre-existent HBV-specific antibody at the time of infection are high, as could be attained by vaccination. We further showed that viral clearance can be achieved for low equilibrium anti-HBV antibody levels, as in unvaccinated individuals, when a strong cellular immune response controls early infection.     

Hepatitis B Virus: From Diagnosis to Treatment

Hepatitis B infection is still a global concern progressing as acute-chronic hepatitis, severe liver failure, and death. The infection is most widely transmitted from the infected mother to a child, with infected blood and body fluids. Pregnant women, adolescents, and all adults at high risk of chronic infection are recommended to be screened for hepatitis B infection. The initial analysis includes serological tests that allow differentiation of acute and chronic hepatitis. Molecular assays performed provide detection and quantification of viral DNA, genotyping, drug resistance, and precore/core mutation analysis to confirm infection and monitor disease progression in chronic hepatitis B patients. All patients with chronic hepatitis B should be treated with antiviral medications and regularly monitored for efficient treatment. The current treatment is based on nucleos(t)ide analogs and pegylated interferons that save lives by decreasing liver cancer death, liver transplant, slow or reverse the progression of liver disease as well as the virus infectivity.Key words: hepatitis B virus (HBV), serology, nucleic acid testing, antiviral treatment     

A mathematical model of the intracellular replication and within host evolution of hepatitis type B virus: Understanding the long time course of chronic hepatitis

Hepatitis B virus (HBV) causes acute and chronic liver disease. Especially, chronic hepatitis is a major risk factor of liver cirrhosis and hepatocellular carcinoma. Viral kinetics of HBV observed in peripheral blood is quite different depending on the clinical course of hepatitis. But the relationship between the intracellular replication dynamics and clinical course of HBV infection is unclear. Further it is very difficult to predict the long time course of hepatitis because the nature of HBV is changed by mutation within host with high mutation rate. We investigate the intracellular replication dynamics and within host evolution of HBV by using a mathematical model. Two different intracellular replication patterns of HBV, “explosive” and “arrested”, are switched depending on the viral gene expression pattern. In the explosive replication, prominent growth of HBV is observed. On the other hand, the virion production is restricted in the arrested replication. It is suggested that the arrested and explosive replication is associated with chronic hepatitis and exacerbation of hepatitis respectively. It is shown by our evolutionary simulation that the exacerbation of hepatitis is caused by the emergence of explosive genotype of HBV from arrested genotype by mutation during chronic hepatitis. It is also shown that chronic infection without exacerbation is maintained by short waiting time for virion release and superinfection with arrested genotype. It is suggested that extension of waiting time for virion release and existence of uninfected hepatocyte in the liver may become risk factors for the exacerbation of hepatitis.     

Underwhelming the immune response: effect of slow virus growth on CD8+-T-lymphocyte responses

The speed of virus replication has typically been seen as an advantage for a virus in overcoming the ability of the immune system to control its population growth. Under some circumstances, the converse may also be true: more slowly replicating viruses may evoke weaker cellular immune responses and therefore enhance their likelihood of persistence. Using the model of lymphocytic choriomeningitis virus (LCMV) infection in mice, we provide evidence that slowly replicating strains induce weaker cytotoxic-T-lymphocyte (CTL) responses than a more rapidly replicating strain. Conceptually, we show a "bell-shaped" relationship between the LCMV growth rate and the peak CTL response. Quantitative analysis of human hepatitis C virus infections suggests that a reduction in virus growth rate between patients during the incubation period is associated with a spectrum of disease outcomes, from fulminant hepatitis at the highest rate of viral replication through acute resolving to chronic persistence at the lowest rate. A mathematical model for virus-CTL population dynamics (analogous to predator [CTL]-prey [virus] interactions) is applied in the clinical data-driven analysis of acute hepatitis B virus infection. The speed of viral replication, through its stimulus of host CTL responses, represents an important factor influencing the pathogenesis and duration of virus persistence within the human host. Viruses with lower growth rates may persist in the host because they "sneak through" immune surveillance.     

Personalized therapy in chronic viral hepatitis

Chronic carriers of major hepatitis viruses (i.e., hepatitis B and C viruses, HBV and HCV) account for at least 600 millions people worldwide. About 50% of them are at risk for chronic hepatitis and 20-30% of patients with chronic hepatitis develop progressive liver disease and symptomatic life-threatening liver lesions. Therefore, the identification of the carrier at risk is mandatory to prevent progressive liver disease, avoiding non-appropriate treatments. The decision making has three major steps. The 1st is the identification of the patient who needs to be treated; the 2nd is the choice of the best therapeutic strategy and the most appropriate drugs and timing during the phase of infection and disease; the 3rd is the treatment optimization to reduce non effective therapy and avoid drug resistance virus mutants. This careful evaluation takes into account the individual variability, the host/virus interplays and the drug impact on viral replication with the risk of selection of resistant mutants. The complexity of the virus/host interactions, however, cannot be managed by simple mean of probabilistic statistics and/or step-wise algorithms based on population statistics. A better answer for personalized antiviral therapy may come from the combined use of molecular biology and bio-mathematical modeling that can help the medical doctor to follow the dynamic of viral infection during therapy, like the flight simulator helps the pilot. We provide a concise review of the potentials of this approach in clinical practice.     

丙型肝炎病毒受体SR-BⅠ的研究进展

丙型肝炎病毒（HCV）是经血液传播而引起急、慢性肝炎的主要致病因子之一,是导致肝硬化、肝细胞癌等终末期肝病的主要原因。位于HCV包膜E2蛋白N端的第1高变区（HVR1）,是介导E2蛋白与B族I型清道夫受体（SR-BⅠ）结合及HCV感染细胞的关键肽段。研究表明,HCV可能利用了SR-BⅠ受体的某些生理功能入侵细胞,进行细胞-细胞间传播。因此,HVR1与SR-BⅠ相互作用的研究除了能深入了解HCV吸附和入侵细胞机制,同时也为治疗和预防HCV感染提供了新的靶点。     

乙型肝炎病毒DNA疫苗的研究进展

预防与控制乙型肝炎发病的乙型肝炎病毒(HBV)疫苗,是有重大的社会和经济意义。HBV的持续感染可引起慢性肝脏疾患,并逐步发展为肝硬化和肝细胞癌(HCC)。目前的乙肝重组亚单位疫苗可以使90％的接种产生保护性抗体;但是对慢性HBV携带,由于其机体对HBsAg蛋白产生耐受,不能产生体液和细胞免疫,因此它只能作为一种预防性的疫苗。DNA疫苗(基因疫苗)是一种新的疫苗技术,通过向体内递送编码抗原的细菌质粒,刺激产生特异的体液和细胞免疫反应。在小鼠和其他的肝炎病毒感染动物模型中,HBV DNA疫苗可以特异性地引起体液和细胞免疫,清除HBV转基因动物血循环中的HBsAg颗粒和HBV DNA。如果加入各种免疫调节细胞因子的基因,可以进一步提高HBV DNA疫苗的免疫效果,因此它不仅可作为预防性疫苗,也可作为治疗型疫苗。     

Mechanisms of viral hepatitis induced liver injury

Among seven human hepatitis viruses (A to E, G and TT virus), hepatitis B (HBV) and C (HCV) viruses are able to persist in the host for years and principally contribute to the establishment of chronic hepatitis. During the course of persistent infection, continuous intrahepatic inflammation maintains a cycle of liver cell destruction and regeneration that often terminates in hepatocellular carcinoma (HCC). While the expression and retention of viral proteins in hepatocytes may influence the severity and progression of liver disease, the mechanisms of liver injury in viral hepatistis are defined to be due not to the direct cytopathic effects of viruses, but to the host immune response to viral proteins expressed by infected hepatocytes. In the process of liver injury, hepatocellular death (apoptosis) induced by the proapoptotic molecules of T cells activated following antigen recognition triggers a cascade of antigen nonspecific effector systems and causes necroinflammatory disease. Accordingly, the regulation of the immune response, e.g., via the cell death pathways, in chronically infected patients should prevent the development of HCC.     

Immunology of hepatitis B virus and hepatitis C virus infection

More than 500 million people worldwide are persistently infected with the hepatitis B virus (HBV) and/or hepatitis C virus (HCV) and are at risk of developing chronic liver disease, cirrhosis and hepatocellular carcinoma. Despite many common features in the pathogenesis of HBV- and HCV-related liver disease, these viruses markedly differ in their virological properties and in their immune escape and survival strategies. This review assesses recent advances in our understanding of viral hepatitis, contrasts mechanisms of virus-host interaction in acute hepatitis B and hepatitis C, and outlines areas for future studies.