Hepatitis B virus immunopathology

Differential Expression of Woodchuck Toll-Like Receptors 1-10 in Distinct Forms of Infection and Stages of Hepatitis in Experimental Hepatitis B Virus Infection

Woodchucks infected with woodchuck hepatitis virus (WHV) represent a highly valuable model of human hepatitis B virus (HBV) infection, chronic hepatitis (CH), and virus induced-primary liver cancer. Toll-like receptors (TLRs) are important mediators of immune responses playing pivotal roles in the pathogenesis of viral diseases; however, their expression profiles in different forms of infection and stages of hepatitis, and in healthy animals remain essentially unknown. In this study, woodchuck TLRs 1–10 exon fragments were identified and TLR genes transcription quantified in livers, primary hepatocytes, peripheral blood mononuclear cells (PBMC), and in selected organs during experimental WHV infection. Among others, liver biopsies from acute hepatitis (AH) and CH showed significantly augmented expression of the majority of TLRs when compared to healthy and woodchucks prior to AH, with resolved AH or primary occult infection. In contrast to the liver tissue, significant upregulation of TLR3, TLR4, and TLR10, but downregulation of TLR7, characterized hepatocytes derived from livers of animals with resolved AH accompanied by secondary occult infection. Hepatocytes from CH showed significantly lower expression or a trend toward suppression of several TLRs when compared to hepatocytes from healthy animals and woodchucks with other forms of infection or hepatitis, suggesting that hepatocyte innate immune response is downregulated during CH. Contrastingly, upregulated transcription of some TLRs characterized PBMC throughout CH. Our study uncovered that TLR expression significantly varies between different forms of hepadnaviral infection and whether infection is accompanied or not by hepatitis. The results showed that the profiles of TLRs’ expression in circulating lymphomononuclear cells do not mirror accurately those of livers and hepatocytes from infected animals. These findings are of importance to the understanding of immune process operating at different sites targeted by virus in the course of hepadnaviral infection and evaluation of future therapies modifying antiviral innate responses in the woodchuck model.

Viral DNA-Dependent Induction of Innate Immune Response to Hepatitis B Virus in Immortalized Mouse Hepatocytes

Hepatitis B virus (HBV) infects hundreds of millions of people worldwide and causes acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HBV is an enveloped virus with a relaxed circular (RC) DNA genome. In the nuclei of infected human hepatocytes, conversion of RC DNA from the incoming virion or cytoplasmic mature nucleocapsid (NC) to the covalently closed circular (CCC) DNA, which serves as the template for producing all viral transcripts, is essential to establish and sustain viral replication. A prerequisite for CCC DNA formation is the uncoating (disassembly) of NCs to expose their RC DNA content for conversion to CCC DNA. We report here that in an immortalized mouse hepatocyte cell line, AML12HBV10, in which RC DNA exposure is enhanced, the exposed viral DNA could trigger an innate immune response that was able to modulate viral gene expression and replication. When viral gene expression and replication were low, the innate response initially stimulated these processes but subsequently acted to shut off viral gene expression and replication after they reached peak levels. Inhibition of viral DNA synthesis or cellular DNA sensing and innate immune signaling diminished the innate response. These results indicate that HBV DNA, when exposed in the host cell cytoplasm, can function to trigger an innate immune response that, in turn, modulates viral gene expression and replication.

IMPORTANCE

Chronic infection by hepatitis B virus (HBV) afflicts hundreds of millions worldwide and is sustained by the episomal covalently closed circular (CCC) DNA in the nuclei of infected hepatocytes. Release of viral genomic DNA from cytoplasmic nucleocapsids (NCs) (NC disassembly or uncoating) is a prerequisite for its conversion to CCC DNA, which can also potentially expose the viral DNA to host DNA sensors and trigger an innate immune response. We have found that in an immortalized mouse hepatocyte cell line in which efficient CCC DNA formation was associated with enhanced exposure of nucleocapsid-associated DNA, the exposed viral DNA indeed triggered host cytoplasmic DNA sensing and an innate immune response that was able to modulate HBV gene expression and replication. Thus, HBV can, under select conditions, be recognized by the host innate immune response through exposed viral DNA, which may be exploited therapeutically to clear viral persistence.

Metabolism and function of hepatitis B virus cccDNA: Implications for the development of cccDNA-targeting antiviral therapeutics

Persistent hepatitis B virus (HBV) infection relies on the stable maintenance and proper functioning of a nuclear episomal form of the viral genome called covalently closed circular (ccc) DNA. One of the major reasons for the failure of currently available antiviral therapeutics to achieve a cure of chronic HBV infection is their inability to eradicate or inactivate cccDNA. In this review article, we summarize our current understanding of cccDNA metabolism in hepatocytes and the modulation of cccDNA by host pathophysiological and immunological cues. Perspectives on the future investigation of cccDNA biology, as well as strategies and progress in therapeutic elimination and/or transcriptional silencing of cccDNA through rational design and phenotypic screenings, are also discussed. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B."

Rethinking the pathogenesis of hepatitis B virus (HBV) infection

Chronic hepatitis B virus (HBV) infection affects approximately 375 million people worldwide. Current antiviral treatment effectively controls, but rarely clears chronic HBV infection. In addition, a significant portion of chronic HBV infected patients are not suitable for currently available antiviral therapy, and still face higher risk for cirrhosis and hepatocellular carcinoma. The poorly understood pathogenesis of HBV infection is the main barrier for developing more effective treatment strategies. HBV has long been viewed as non-cytopathic and the central hypothesis for HBV pathogenesis lies in the belief that hepatitis B is a host specific immunity-mediated liver disease. However, this view has been challenged by the accumulating experimental and clinical data that support a model of cytopathic HBV replication. In this article we systematically review the pathogenic role of HBV replication in hepatitis B and suggest possible HBV replication related mechanisms for HBV-mediated liver injury. We propose that a full understanding of HBV pathogenesis should consider the following elements. I. Liver injury can be caused by high levels of HBV replication and accumulation of viral products in the infected hepatocytes. II. HBV infection can be either directly cytopathic, non-cytopathic, or a mix of both in an individual patient depending upon accumulation levels of viral products that are usually associated with HBV replication activity in individual infected hepatocytes.

Micro-evolution of the hepatitis B virus genome in hepatitis B e-antigen-positive carriers: comparison of genotypes B and C at various immune stages

BACKGROUND AND AIM

Patients with hepatitis B virus (HBV) genotype B infection experience hepatitis B e-antigen (HBeAg) seroconversion at an earlier stage than do patients with genotype C infection. Therefore, this study investigated whether the differential phenotypes are related to HBV genomic evolution.

METHODS

Thirty-three HBeAg-positive patients with a mean follow-up of 3.1 years were enrolled: 16 at the immune tolerance stage (group I) and 17 at the immune clearance stage (group II). The evolution rates of paired viral genomes at enrollment and at the final follow-up in the full-length genome (μf), nonoverlapping regions (synonymous [μs] and nonsynonymous [μa]), and overlapping regions (μ) were calculated. The evolution rates were then compared according to serum alanine aminotransferase (ALT) levels and HBV genotype.

RESULTS

The overall μf evolution rate was lower in group I than in group II (1.4 × 10(-5)  ± 3.3 × 10(-5) vs 1.2 × 10(-3)  ± 1.2 × 10(-3) nucleotide substitution/site/year, P < 0.001). We observed similar results for the μs, μa, and μ evolution rates. All evolution parameters were comparable between genotypes B and C. We determined a positive correlation between μa/y and the area under the average ALT time curve in genotype B (R(2)  = 0.6935, P < 0.0001), but not in genotype C (R(2)  = 0.1606, P = 0.124).

CONCLUSION

The evolution rate of the HBV genome is higher at the immune clearance stage than at the immune tolerance stage. Host immune selection might play a role in triggering evolution of genotype B.

Targeted in vivo delivery of siRNA and an endosome-releasing agent to hepatocytes

The discoveries of RNA interference (RNAi) and short interfering RNAs (siRNAs) have provided the opportunity to treat diseases in a fundamentally new way: by co-opting a natural process to inhibit gene expression at the mRNA level. Given that siRNAs must interact with the cells' natural RNAi machinery in order to exert their silencing effect, one of the most fundamental requirements for their use is efficient delivery to the desired cell type and, specifically, into the cytoplasm of those cells. Numerous research efforts involving the testing of a large number of delivery approaches using various carrier molecules and inventing several distinct formulation technologies during the past decade illustrate the difficulty and complexity of this task. We have developed synthetic polymer formulations for in vivo siRNA delivery named Dynamic PolyConjugates™ (DPCs) that are designed to mimic the features viruses possess for efficient delivery of their nucleic acids. These include small size, long half-life in circulation, capability of displaying distinct host cell tropism, efficient receptor binding and cell entry, disassembly in the endosome and subsequent release of the nucleic acid cargo to the cytoplasm. Here we present an example of this delivery platform composed of a hepatocyte-targeted endosome-releasing agent and a cholesterol-conjugated siRNA (chol-siRNA). This delivery platform forms the basis of ARC-520, an siRNA-based therapeutic for the treatment of chronic hepatitis B virus (HBV) infection. In this chapter, we provide a general overview of the steps in developing ARC-520 and detailed protocols for two critical stages of the discovery process: (1) verifying targeted in vivo delivery to hepatocytes and (2) evaluating in vivo drug efficacy using a mouse model of chronic HBV infection.

Modeling T cell responses to antigenic challenge

T cell responses are a crucial part of the adaptive immune system in the fight against infections. This article discusses the use of mathematical models for understanding the dynamics of cytotoxic T lymphocyte (CTL) responses against viral infections. Complementing experimental research, mathematical models have been very useful for exploring new hypotheses, interpreting experimental data, and for defining what needs to be measured to improve understanding. This review will start with minimally parameterized models of CTL responses, which have generated some valuable insights into basic dynamics and correlates of control. Subsequently, more biological complexity is incorporated into this modeling framework, examining different mechanisms of CTL expansion, different effector activities, and the influence of T cell help. Models and results are discussed in the context of data from specific infections.

Mutations associated with occult hepatitis B in HIV-positive South Africans

Occult hepatitis B is characterized by the absence of hepatitis B surface antigen (HBsAg) but the presence of HBV DNA. Because diagnosis of hepatitis B virus (HBV) typically includes HBsAg detection, occult HBV remains largely undiagnosed. Occult HBV is associated with increased risk of hepatocellular carcinoma, reactivation to chronic HBV during immune suppression, and transmission during blood transfusion and liver transplant. The mechanisms leading to occult HBV infection are unclear, although viral mutations are likely a significant factor. In this study, sera from 394 HIV-positive South Africans were tested for HBV DNA and HBsAg. For patients with detectable HBV DNA, the overlapping surface and polymerase open reading frames (ORFs) were sequenced. Occult-associated mutations-those mutations found exclusively in individuals with occult HBV infection but not in individuals with chronic HBV infection from the same cohort or GenBank references-were identified. Ninety patients (22.8%) had detectable HBV DNA. Of these, 37 had detectable HBsAg, while 53 lacked detectable surface antigen. The surface and polymerase ORFs were cloned successfully for 19 patients with chronic HBV and 30 patients with occult HBV. In total, 235 occult-associated mutations were identified. Ten occult-associated mutations were identified in more than one patient. Additionally, 15 amino acid positions had two distinct occult-associated mutations at the same residue. Occult-associated mutations were common and present in all regions of the surface and polymerase ORFs. Further study is underway to determine the effects of these mutations on viral replication and surface antigen expression in vitro.

Role of proinflammatory cytokines (interferon gamma) and anti-inflammatory cytokine (interleukin-10) gene polymorphisms in chronic hepatitis B infection: an Indian scenario

Immune-mediated mechanisms have been found to play an important role in the progression of hepatitis B virus (HBV) infection. The outcomes of infection do not appear to be determined by viral strains. Instead, allelic variants in human genome are likely to affect the disease progression. Allelic variation of proinflammatory cytokines such as interferon gamma (IFN-γ) participates in the elimination of HBV, and interleukin-10 (IL-10) helps in inhibition of Th1 effector mechanisms for host defense. The aim of this study was to determine the influence of host genetic factors in chronic HBV infection and gene promoter polymorphism or single-nucleotide polymorphism analysis of IFN-γ+874 and IL-10 (-1082, -592, and -819) on disease progression and persistence. A total of 232 patients along with 76 healthy controls were included. Allele-specific primers for IFN-γ and restriction fragment length polymorphism for IL-10 were used. The study indicated that low IFN-γ expression probably impairs host immune response to HBV, rendering these subjects more prone to HBV infection. No significant differences were detected between the 2 groups in the distributions of IL-10 genotype at the -1082, -819, and -592 positions. Odds ratio indicated that heterozygosity of genotypes -819 CT and -592 AC was more strongly associated with liver chronicity. Significantly, AA homozygous genotype was dominant in chronic hepatitis B cases in IFN-γ+874 and IL-10 (-1082 and -592) and is associated with increased risk of persistent infection.

Association of human leukocyte antigen class I polymorphism with spontaneous clearance of hepatitis B surface antigen in Qidong Han population

AIM

To investigate whether HLA class I polymorphisms could influence the clearance of hepatitis B surface antigen (HBsAg) in Qidong Han population.

METHODS

We genotyped HLA-A, -B, and -C loci of 448 individuals with HBV persistent infection and 140 persons with spontaneous clearance of HBsAg by polymerase chain reaction with sequencing based typing (PCR/SBT). All the individuals were unrelated males enrolled from Qidong Han population and were followed up for 10 years.

RESULTS

The frequency of HLA-A∗33:03:01G was increased in persistent HBV infection group (P value is 0.028), while frequency of HLA-B∗13:01:01G was increased in HBsAg clearance group (P value is 0.0004).

CONCLUSION

These findings suggested that the host HLA class I polymorphism is an important factor in determining the outcomes of HBV infection.

A clinical study of HBsAg-activated dendritic cells and cytokine-induced killer cells during the treatment for chronic hepatitis B

We aim to study the therapeutic effects of HBsAg-activated DCs and cytokine-induced killer (CIK) cells as adoptive immunotherapy in patients with Chronic Hepatitis B (CHB). Autologous HBsAg-activated DC-CIK cells were infused into patients with CHB to evaluate their effect on HBV-DNA, HBsAg, ALT, etc. The viral load in the treatment group decreased significantly (P < 0.001), while that in the control group did not decrease (P > 0.05). Twenty-one patients (63.6% efficiency) in the treatment group had a viral response (≥2 log decrease in viral load), while four patients (14.8% efficiency) from the control group had a viral response. There were significant differences in the viral responses of the two groups (the control group 63.6% versus the control group 14.8%, P < 0.001). We concluded that the immunity was enhanced after HBsAg activation in DCs and CIK cells. Reinfusion of autologous HBsAg-activated DC-CIK cells inhibited HBV proliferation in 21 of 33 (63.6%) patients.

Serum tumor necrosis factor-alpha level in hepatitis E virus-related acute viral hepatitis and fulminant hepatic failure in pregnant women

AIM

The host response in hepatitis E virus (HEV)-related liver disease of pregnant women is unclear. This study was carried out to evaluate the serum concentration of tumor necrosis factor (TNF)-α in HEV-related acute viral hepatitis (AVH) and fulminant hepatic failure (FHF) in pregnant women in relation to pregnancy outcome.

METHODS

The study included 262 pregnant and 158 non-pregnant women with jaundice. There were 160 healthy asymptomatic pregnant women and 124 healthy asymptomatic non-pregnant women as controls. The jaundiced patients were classified as AVH or FHF. Serum TNF-α level was assayed by commercially available enzyme-linked immunoassay kits.

RESULTS

A significantly higher level of TNF-α was observed in HEV-infected pregnant women than non-HEV pregnant women (P < 0.001). TNF-α level was significantly higher in AVH and FHF of HEV-infected pregnant women compared with AVH and FHF of HEV infected non-pregnant women (P = 0.036 and P = 0.010, respectively). The HEV-infected pregnant FHF expired group had significantly higher levels of TNF-α than the non-pregnant FHF expired group (P = 0.025). TNF-α levels were significantly higher in AVH of HEV-infected pregnant women than healthy pregnant controls (P < 0.001). Higher TNF-α levels were observed in HEV-infected women having preterm delivery and low birthweight newborns compared with non-HEV and healthy pregnant women.

CONCLUSION

Higher serum concentration of TNF-α observed in HEV infected AVH and FHF pregnant cases shows that pregnancy with HEV infection increases TNF-α secretion. TNF-α may be an important factor in the outcomes of pregnancy due to HEV infection.

The Influence of Hepatitis B Viral Load and Pre-S Deletion Mutations on Post-Operative Recurrence of Hepatocellular Carcinoma and the Tertiary Preventive Effects by Anti-Viral Therapy

Background

Whether or not hepatitis B virus (HBV) genotypes, mutations, and viral loads determine outcomes for patients with HBV-induced hepatocellular carcinoma (HCC) remains controversial.

Aims

To study the influence of HBV viral factors on prognoses for patients with HBV-induced HCC after resection surgery and investigate if antiviral therapy could counteract the adverse effects of viral factors.

Methods

A total of 333 HBV-related HCC patients who underwent tumor resection were enrolled retrospectively. Serum HBV DNA levels, mutations, anti-viral therapy, and other clinical variables were analyzed for their association with post-operative recurrence.

Results

After a median follow-up of 45.9 months, 208 patients had HCC recurrence after resection. The 5-year overall survival and recurrence-free survival rates were 55.4% and 35.3%, respectively. Multivariate analysis showed indocyanine green retention rate at 15 minutes >10%, gamma-glutamyltransferase (GGT) level >60 U/L, macroscopic and microscopic venous invasion, and the absence of anti-viral therapy were significant risk factors for recurrence. Anti-viral therapy could decrease recurrence in patients with early stage HCC, but the effect was less apparent in those with the Barcelona-Clinic Liver Cancer stage C HCC. For patients without antiviral therapy after resection, serum HBV DNA levels >10⁶ copies/mL, GGT >60 U/L, and macroscopic and microscopic venous invasion were significant risk factors predicting recurrence. Among the 216 patients without anti-viral therapy but with complete HBV surface gene mapping data, 73 were with pre-S deletion mutants. Among patients with higher serum HBV DNA levels, those with pre-S deletion had significantly higher rates of recurrence. Moreover, multivariate analysis showed multi-nodularity, macroscopic venous invasion, cirrhosis, advanced tumor cell differentiation, and pre-S deletion were significant risk factors predictive of recurrence.

Conclusions

Ongoing HBV viral replication and pre-S deletion are crucial for determining post-operative tumor recurrence. Anti-viral therapy can help reduce recurrence and improve prognosis, especially for those with early stage HCC.

Telbivudine treatment is associated with high hepatitis B e antigen seroconversion and immune modulatory effects in chronic hepatitis B patients

Chronic hepatitis B (CHB) is characterized by an impaired immune response to hepatitis B virus. Among the nucleos(t)ides used in CHB treatment, telbivudine is associated with the highest rates of hepatitis B e antigen (HBeAg) seroconversion rates, which are similar to those observed with pegylated interferon (PegIFN). Besides direct antiviral effect, modulation of the immune system may be an additional benefit for telbivudine-treated patients. Indeed, there is much clinical data indicating an IFN-like behaviour for telbivudine in contrast to other oral nucleos(t)ides, such as high HBeAg seroconversion, similar hepatitis B surface antigen (HBsAg) decline and biphasic viral kinetics. Clinical studies, animal models and in vitro studies suggest that both the innate and adaptive immune system responses contribute to high HBeAg seroconversion during telbivudine treatment through modulation of the function and/or expression of CD4+/CD8+ T cells, Th1/Th2, Treg, PD-1/PD-L1, Th17, IL-21 and TFH. The results described in this review suggest that the antiviral effect of telbivudine may be attributable not only to direct suppression of hepatitis B virus, but also to immunoregulatory effects. Hypothetically, telbivudine shares some common signal pathways with IFN.

Immunization with a recombinant vaccinia virus that encodes nonstructural proteins of the hepatitis C virus suppresses viral protein levels in mouse liver

Chronic hepatitis C, which is caused by infection with the hepatitis C virus (HCV), is a global health problem. Using a mouse model of hepatitis C, we examined the therapeutic effects of a recombinant vaccinia virus (rVV) that encodes an HCV protein. We generated immunocompetent mice that each expressed multiple HCV proteins via a Cre/loxP switching system and established several distinct attenuated rVV strains. The HCV core protein was expressed consistently in the liver after polyinosinic acid–polycytidylic acid injection, and these mice showed chronic hepatitis C-related pathological findings (hepatocyte abnormalities, accumulation of glycogen, steatosis), liver fibrosis, and hepatocellular carcinoma. Immunization with one rVV strain (rVV-N25), which encoded nonstructural HCV proteins, suppressed serum inflammatory cytokine levels and alleviated the symptoms of pathological chronic hepatitis C within 7 days after injection. Furthermore, HCV protein levels in liver tissue also decreased in a CD4 and CD8 T-cell-dependent manner. Consistent with these results, we showed that rVV-N25 immunization induced a robust CD8 T-cell immune response that was specific to the HCV nonstructural protein 2. We also demonstrated that the onset of chronic hepatitis in CN2-29^(+/−)/MxCre^(+/−) mice was mainly attributable to inflammatory cytokines, (tumor necrosis factor) TNF-α and (interleukin) IL-6. Thus, our generated mice model should be useful for further investigation of the immunological processes associated with persistent expression of HCV proteins because these mice had not developed immune tolerance to the HCV antigen. In addition, we propose that rVV-N25 could be developed as an effective therapeutic vaccine.

Hepatitis B virus infection: pathogenesis, reactivation and management in hematopoietic stem cell transplant recipients

Hepatitis B virus (HBV) is a partially double stranded DNA virus that can integrate into host cell chromosomes as covalently closed circular DNA forms. HBV reactivation following hematopoietic stem cell transplantation in recipients with evidence of past HBV exposure, as well as exacerbation of a current HBV infection in HBV carrier recipients, secondary to chemotherapy and post-transplant immunosuppression that affect both humoral and cell-mediated control of HBV infection, are well documented in the literature. Management options include HBV-DNA screening and antiviral prophylaxis. Nucleos(t)ide analogues have been used at the start of chemotherapy and pretransplantation, with the course continuing for 6 months. However, depending on the serum HBV-DNA level, the antiviral agent might be given until a therapeutic end point is reached.

HIV/HBV Co-Infections: Epidemiology, Natural History, and Treatment: A Review Article

Hepatitis B virus (HBV) infection, one of the major health priorities, accounts approximately for 350 million chronic cases and a global total of 33 million people were living with human immunodeficiency virus (HIV) in the world.Co-infection with HIV and the HBV presents a significant challenge to health care providers, with different prevalence rates in different parts of the world. It is important to screen all HIV infected individuals for HBV infection and reverse. Infection with HBV becomes more violent in patients co-infected with human immunodeficiency syndrome. HIV/HBV co-infected individuals are at increased risk of chronic hepatitis, cirrhosis, and hepatocellular carcinoma, and of experiencing HAART toxicity. In this review, the latest statistics on epidemiology of HIV, HBV and their co-infection has been presented along with prominent characteristics of HBV. Transmission routes which are the common between HBV and HIV are described and the most important ones are described according to the regional and age features. Also, there is a series of actions being performed once HBV infections occur to prevent HIV or to diagnose if the HBV-infected individuals are also infected with HIV. As in treatment case, some of the frequent treatment methods including applying interferon and using nucleoside and nucleotide analogues have been discussed. Finally, we would explain the new recommendations for treating patients who were co-infected with HBV and HIV, including staging HBV and HIV treatment, based on the stage of each disease. It also outlines the optimal treatment options, whether the patient is treated for HBV first, HIV first, or HIV and HBV together.

Toll-like receptors signaling contributes to immunopathogenesis of HBV infection

Innate and adaptive immune systems have important role in the pathogenesis of acute and chronic infection with hepatitis B virus (HBV). These immune responses are mediated through complex interactions between the innate immune response and adaptive immune response. Toll-like receptors (TLRs) are a family of innate immune-recognition receptors that recognize the molecular patterns associated with microbial pathogens. So far, TLR1 to 13 were found in human or mice and investigated to detect the target molecules and the downstream mechanisms of these unique systems. Stimulation by their ligands initiates the activation of complex networks of intracellular signaling transduction and innate and adaptive immune-related cells (NK, NK-T, monocytes, dendritic cells, T cells, B cells, and Tregs, etc.). However, reports on such relationships between HBV and TLRs have been relatively rare in comparison to those on HCV and TLRs, but have recently been increasing. Thus, a review of TLRs involved in the pathogenesis of HBV infection may be needed toward better understanding of the immunopathogenesis of HBV infection.

Electroporation enhances immunogenicity of a DNA vaccine expressing woodchuck hepatitis virus surface antigen in woodchucks

The development of therapeutic vaccines for chronic hepatitis B virus (HBV) infection has been hampered by host immune tolerance and the generally low magnitude and inconsistent immune responses to conventional vaccines and proposed new delivery methods. Electroporation (EP) for plasmid DNA (pDNA) vaccine delivery has demonstrated the enhanced immunogenicity of HBV antigens in various animal models. In the present study, the efficiency of the EP-based delivery of pDNA expressing various reporter genes first was evaluated in normal woodchucks, and then the immunogenicity of an analog woodchuck hepatitis virus (WHV) surface antigen (WHsAg) pDNA vaccine was studied in this model. The expression of reporter genes was greatly increased when the cellular uptake of pDNA was facilitated by EP. The EP of WHsAg-pDNA resulted in enhanced, dose-dependent antibody and T-cell responses to WHsAg compared to those of the conventional hypodermic needle injection of WHsAg-pDNA. Although subunit WHsAg protein vaccine elicited higher antibody titers than the DNA vaccine delivered with EP, T-cell response rates were comparable. However, in WHsAg-stimulated mononuclear cell cultures, the mRNA expression of CD4 and CD8 leukocyte surface markers and Th1 cytokines was more frequent and was skewed following DNA vaccination compared to that of protein immunization. Thus, the EP-based vaccination of normal woodchucks with pDNA-WHsAg induced a skew in the Th1/Th2 balance toward Th1 immune responses, which may be considered more appropriate for approaches involving therapeutic vaccines to treat chronic HBV infection.

Association of hepatitis B virus pre-S deletions with the development of hepatocellular carcinoma in chronic hepatitis B

BACKGROUND

We aimed to determine whether hepatitis B virus (HBV) pre-S deletion was an independent factor for the development of hepatocellular carcinoma (HCC).

METHODS

Pre-S deletions were determined in HBV isolates from 115 chronic hepatitis B (CHB) patients with HCC. Sixty-nine patients were further matched with 69 CHB patients without HCC for age, sex, hepatitis B e antigen (HBeAg) status, and HBV genotype.

RESULTS

HBV pre-S deletions were clustered mainly in the 3' end of pre-S1 and 5' end of pre-S2 regions. Adjusted for confounding risk factors, patients with HCC had a higher prevalence of HBV with pre-S deletions than did patients without HCC (23 [33.3%] of 69 vs 11 [15.9%] of 69; P = .018; odds ratio [OR], 2.64). In particular, only pre-S2 deletions but not pre-S1 deletions were significantly associated with the development of HCC (P = .020). A higher prevalence of pre-S deletions was observed in HBV isolates from HCC patients under the age of 50 years than from those older than 50 years (10 [62.5%] of 16 vs 13 [24.5%] of 53; P = .012; OR, 5.13). Emergence of de novo pre-S deletions was documented before the development of HCC.

CONCLUSIONS

HBV pre-S2 deletions were an independent factor associated with the development of HCC. Its oncogenic role may be more important in young patients with HCC.

Tumor initiation and progression in hepatocellular carcinoma: risk factors, classification, and therapeutic targets

Hepatocellular carcinoma (HCC) is a major health problem worldwide responsible for 500 000 deaths annually. A number of risk factors are associated with either the induction of the disease or its progression; these include infection with hepatitis B or C virus, alcohol consumption, non-alcoholic steatohepatitis and certain congenital disorders. In around 80% of the cases, HCC is associated with cirrhosis or advanced fibrosis and with inflammation and oxidative stress. In this review we focus firstly on the different risk factors for HCC and summarize the mechanisms by which each is considered to contribute to HCC. In the second part we look at the molecular processes involved in cancer progression. HCC development is recognized as a multistep process that normally develops over many years. Over this period several mutations accumulate in the cell and that stimulate malign transformation, growth, and metastatic behavior. Over the recent years it has become evident that not only the tumor cell itself but also the tumor microenviroment plays a major role in the development of a tumor. There is a direct link between the role of inflammation and cirrhosis with this microenviroment. Both in vitro and in vivo it has been shown that tumor formation and metastatic properties are linked to epithelial-mesenchymal transition (EMT), a process by which facillitates the tumor cell's attempts to migrate to a more favourable microenviroment. Several groups have analyzed the gene expression in HCC and its surrounding tissue by microarray and this has resulted in the molecular classification into a distinct number of classes. Here we also found a role for hypoxia induced gene expression leading to a clinically more aggressive gene expression in HCC. Molecular analysis also helped to identify important cellular pathways and possible therapeutic targets. The first molecule that in this way has shown clinical application for liver cancer is the multikinase inhibitor sorafenib, others are currently in different stages of clinical studies like the mTOR inhibitor everolimus.

Can engineered "designer" T cells outsmart chronic hepatitis B?

More than 350 million people worldwide are persistently infected with human heptatitis B virus (HBV) and at risk to develop liver cirrhosis and hepatocellular carcinoma making long-term treatment necessary. While a vaccine is available and new antiviral drugs are being developed, elimination of persistently infected cells is still a major issue. Recent efforts in adoptive cell therapy are experimentally exploring immunotherapeutic elimination of HBV-infected cells by means of a biological attack with genetically engineered "designer" T cells.

Pre-acute hepadnaviral infection is associated with activation-induced apoptotic death of lymphocytes in the woodchuck (Marmota monax) model of hepatitis B

Woodchucks (Marmota monax) infected with woodchuck hepatitis virus (WHV) represent a highly valuable immunopathogenic model of hepatitis B virus (HBV) infection. Both WHV and HBV are noncytopathic hepadnaviruses which induce a strong but delayed virus-specific cellular immune response believed to be a cause of hepatitis. The reason behind this postponement is not well understood and its dissection in the woodchuck model has been hampered by the lack of appropriate research tools. In this study, we applied an assay for the simultaneous detection of cell apoptosis and proliferation to determine the fate of T lymphocytes after WHV infection leading to acute hepatitis. The results revealed that pre-acute WHV infection is associated with the significantly heightened susceptibility of T lymphocytes to activation-induced apoptotic death. This suggests that T lymphocyte function is compromised very early in the course of hepadnaviral infection and this may directly contribute to the postponement of virus-specific T cell response.

Subcellular proteome analysis unraveled annexin A2 related to immune liver fibrosis

It is important to study the mechanism of liver fibrogenesis, and find new non-invasive biomarkers. In this study, we used subcellular proteomic technology to study the plasma membrane (PM) proteins related to immune liver fibrosis and search for new non-invasive biomarkers. A rat liver fibrosis model was induced by pig serum injection. The liver fibrogenesis from stage (S) S0-1, S2, S3-4, and S4 was detected by Masson staining and HE staining in this rat model after 2, 4, 6, and 8 weeks of treatment. The liver PM was enriched and analyzed using subcellular proteomic technology. The differentially expressed proteins were verified by Western blotting, immunohistochemistry, and ELISA. PM with 149-fold purification was obtained and 22 differentially expressed proteins were identified. Of which, annexin A2 (ANXA2) was detected to be increased obviously in S4 compared with S0-1, and verified by Western blotting of rat liver tissue and immunohistochemistry of rat and human liver tissue. The expression of ANXA2 in human plasma with S1-2 was also found to be up-regulated for 1.4-fold than that in S0. Furthermore, ANXA2 was detected to translocate from nuclear membrane and cytosol to PM as HBV stimulation through immunocytochemical analysis in vitro. This study identified 22 differentially expressed proteins related to liver fibrosis, and verified a potential biomarker (ANXA2) for non-invasive diagnosis of immune liver fibrosis. To our knowledge, it was the first time to dynamically study the proteins related to liver fibrosis and select biomarkers for liver fibrosis diagnosis through PM proteome research.

Rapid immunity to vaccination with woodchuck hepatitis virus surface antigen using cationic liposome-DNA complexes as adjuvant

Complexes of cationic liposomes and non-coding DNA (CLDC) have shown promise as vaccine adjuvant. Using the woodchuck animal model of hepatitis B virus (HBV) infection, the immunogenic effects of CLDC were evaluated following vaccination with three doses of woodchuck hepatitis virus surface antigen (WHsAg) adjuvanted with either CLDC or conventional alum and administered intramuscularly (im) or subcutaneously (sc). IM vaccination with WHsAg and CLDC elicited antibodies earlier, in more woodchucks, and with higher titers than WHsAg and alum. After two vaccine doses, antibody titers were higher following im than sc administration. Woodchucks administered two vaccine doses sc received the third vaccine dose im, and antibody responses reached titers comparable to those elicited by im administration. Following the second vaccine dose, im vaccination with WHsAg and CLDC induced T cell responses to WHsAg and selected WHs peptides and expression of the leukocyte surface marker CD8 and of the Th1 cytokines interferon-gamma and tumor necrosis factor alpha in woodchucks. T cell responses and CD8/cytokine expression were diminished in woodchucks from the other groups suggesting that this vaccine regimen induced a skew toward Th1 immune responses. The present study in woodchucks demonstrates that CLDC-adjuvanted WHsAg vaccine administered im resulted in a more rapid induction of humoral and cellular immune responses compared to conventional, alum-adjuvanted WHsAg vaccine. While less rapid, the immune responses following sc administration can prime the im immune responses. This adjuvant activity of CLDC over alum may be beneficial for therapeutic vaccination in chronic HBV infection.

Multiepitope peptide-loaded virus-like particles as a vaccine against hepatitis B virus-related hepatocellular carcinoma

To develop a hepatitis B virus (HBV) therapeutic vaccine that can induce a broad but specific immune response and significant antitumor effects both in vivo and in vitro, we inserted HBV X protein (HBx)-derived epitopes HBx(52-60), HBx(92-100), and HBx(115-123); a novel subdominant cytolytic T lymphocyte (CTL) epitope HBx(140-148); and the universal T helper epitope pan human leukocyte antigen DR-binding epitope into HBV core protein to form multiepitope peptide-loaded virus-like particles (VLPs). CTL responses against epitope-loaded VLPs were elicited by priming with VLP-pulsed dendritic cells in both HLA-A*0201 transgenic (Tg) mice and peripheral blood lymphocytes from HLA-A2(+)/HBx(+) HBV-infected hepatocellular carcinoma (HCC) patients. The multiepitope peptide-loaded VLPs demonstrated significantly higher immunogenicity in Tg mice than any single responsive epitope. Significant antitumor effects were demonstrated both with primary cultured autologous HCC cells in vitro and tumor-bearing Tg mice in vivo in an HLA-A2-restricted and epitope-specific fashion.

CONCLUSION

The significant antitumor effects both in vivo and in vitro demonstrate the potential of multiepitope peptide-loaded VLPs as a vaccine against HCC.

Generation and characterization of high affinity humanized fab against hepatitis B surface antigen

5S is a mouse monoclonal IgG1 that binds to the 'a' epitope of the Hepatitis B surface antigen (HBsAg) and tested positive in an in vitro test for virus neutralization. We have earlier reported the generation of humanized single chain variable fragment (scFv) from the same. In this article we report the generation of a recombinant Fab molecule by fusing humanized variable domains of 5S with the constant domains of human IgG1. The humanized Fab expressed in E. coli and subsequently purified, retained a high binding affinity (K(D) = 3.63 nmol/L) to HBsAg and bound to the same epitope of HBsAg as the parent molecule. The humanized Fab also maintained antigen binding in the presence of various destabilizing agents like 3 M NaCl, 30% DMSO, 8 M urea, and extreme pH. This high affinity humanized Fab provides a basis for the development of therapeutic molecules that can be safely utilized for the prophylaxis and treatment for Hepatitis B infection.

Putative roles of hepatitis B x antigen in the pathogenesis of chronic liver disease

Under most circumstances, hepatitis B virus (HBV) is noncytopathic. However, hepatocellular regeneration that accompanies each bout of hepatitis appears to be associated with increased integration of HBV DNA fragments expressing the virus encoded hepatitis B x antigen (HBxAg). Intrahepatic HBxAg staining correlates with the intensity and progression of chronic liver disease (CLD), and additional work has shown that HBxAg blocks immune mediated killing by Fas and by tumor necrosis factor alpha (TNFalpha). This is not only associated with the blockage of caspase activities by HBxAg, but also by the constitutive stimulation of hepatoprotective pathways, such as nuclear factor kappa B (NF-kappaB), phosphoinositol 3-kinase (PI3K), and beta-catenin (beta-catenin). HBxAg also appears to promote fibrogenesis, by stimulating the production of fibronectin. HBxAg also stimulates the production and activity of transforming growth factor beta1 (TGFbeta1) by several mechanisms, thereby promoting the profibrogenic and tumorigenic properties of this important cytokine. In addition, HBxAg appears to remodel the extracellular matrix (ECM) by altering the expression of several matrix metalloproteinases (MMPs), which may promote tumor metastasis. Hence, HBxAg appears to promote chronic infection by preventing immune mediated apoptosis of infected hepatocytes, by promoting the establishment and persistence of fibrosis and cirrhosis preceding the development of HCC, and by promoting the remodeling of EMC during tumor progression.

Inhibition of woodchuck hepatitis virus gene expression in primary hepatocytes by siRNA enhances the cellular gene expression

Small interfering RNA (siRNA) has been shown to be active to inhibit the hepatitis B virus gene expression and replication in transient and stable transfection systems. Here in primary hepatocytes prepared from naturally woodchuck hepatitis virus (WHV)-infected woodchucks, four siRNAs targeting the WHV preS1, S, C, and X region led to a depletion of WHV transcripts and replicative intermediates with different kinetics and a decreased production of viral particles. Two siRNAs targeting WHV S and X region had the highest efficacy to deplete 70% of WHV transcripts and replicative intermediates. In addition, siRNA-mediated suppression of WHV enhanced the expression of cellular genes like MxA and MHC I. Specific siRNAs are able to inhibit the hepadnaviral replication and enhance the expression of cellular genes relevant for antiviral actions. Thus, siRNAs might be useful as novel antiviral agents for the treatment of chronic HBV infection.

Mapping and characterization of visna/maedi virus cytotoxic T-lymphocyte epitopes

CD8(+) cytotoxic T-lymphocyte (CTL) responses have been shown to be important in the control of human and simian immunodeficiency virus infections. Infection of sheep with visna/maedi virus (VISNA), a related lentivirus, induces specific CD8(+) CTL in vivo, but the specific viral proteins recognized are not known. To determine which VISNA antigens were recognized by sheep CTL, we used recombinant vaccinia viruses expressing the different genes of VISNA: in six sheep (Finnish LandracexDorset crosses, Friesland and Lleyn breeds) all VISNA proteins were recognized except TAT. Two sheep, shown to share major histocompatibility complex (MHC) class I alleles, recognized POL and were used to map the epitope. The pol gene is 3267 bp long encoding 1088 aa. By using recombinant vaccinia viruses a central portion (nt 1609-2176, aa 537-725) was found to contain the CTL epitope and this was mapped with synthetic peptides to a 25 aa region (aa 612-636). When smaller peptides were used, a cluster of epitopes was detected: at least three epitopes were present, at positions 612-623: DSRYAFEFMIRN; 620-631: MIRNWDEEVIKN; and 625-635: EEVIKNPIQAR. A DNA-prime-modified vaccinia virus Ankara (MVA)-boost strategy was employed to immunize four sheep shown to share MHC class I allele(s) with the sheep above. Specific CTL activity developed in all the immunized sheep within 3 weeks of the final MVA boost although half the sheep showed evidence of specific reactivity after the DNA-prime immunizations. This is the first report, to our knowledge, of induction of CTL by a DNA-prime-boost method in VISNA infection.

Human oncogenic viruses: hepatitis B and hepatitis C viruses and their role in hepatocarcinogenesis

Chronic infections caused by hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the main risk factors for the development of hepatocellular carcinoma (HCC) in humans. Both viruses cause a wide spectrum of clinical manifestations ranging from healthy carrier state to acute and chronic hepatitis, liver cirrhosis, and HCC. HBV and HCV belong to different viral families (Hepadnoviridae and Flaviviridae, respectively); they are characterized by different genetic structures. Clinical manifestations of these viral infections result from the interaction between these viruses and host hepatocytes (i.e. between viral and cell genomes). Proteins encoded by both viruses play an important role in processes responsible for immortalization and transformation of these cells. Chronic inflammation determined by host immune response to the viral infection, hepatocyte death and their compensatory proliferation, as well as modulation of expression of some regulatory proteins of the cell (growth factors, cytokines, etc.) are the processes that play the major role in liver cancer induced by HBV and HCV.

Transient FTY720 treatment promotes immune-mediated clearance of a chronic viral infection

For a wide variety of microbial pathogens, the outcome of the infection is indeterminate. In some individuals the microbe is cleared, but in others it establishes a chronic infection, and the factors that tip this balance are often unknown. In a widely used model of chronic viral infection, C57BL/6 mice clear the Armstrong strain of lymphocytic choriomeningitis virus (LCMV), but the clone 13 strain persists. Here we show that the Armstrong strain induces a profound lymphopenia at days 1-3 after infection, but the clone 13 strain does not. If we transiently augment lymphopenia by treating the clone-13-infected mice with the drug FTY720 at days 0-2 after infection, the mice successfully clear the infection by day 30. Clearance does not occur when CD4 T cells are absent at the time of treatment, indicating that the drug is not exerting direct antiviral effects. Notably, FTY720 treatment of an already established persistent infection also leads to viral clearance. In both models, FTY720 treatment preserves or augments LCMV-specific CD4 and CD8 T-cell responses, a result that is counter-intuitive because FTY720 is generally regarded as a new immunosuppressive agent. Because FTY720 targets host pathways that are completely evolutionarily conserved, our results may be translatable into new immunotherapies for the treatment of chronic microbial infections in humans.

The characteristics of the cell-mediated immune response identify different profiles of occult hepatitis B virus infection

BACKGROUND & AIMS

Hepatitis B virus (HBV) DNA detection in serum and/or in the liver of hepatitis B surface antigen (HBsAg)-negative patients with or without serologic markers of previous viral exposure is defined as occult HBV infection. Because the role of the adaptive response in keeping HBV replication under control in occult infection still is undefined, this study was performed to characterize the features of the HBV-specific T-cell response in this condition.

METHODS

HBV-specific T-cell frequency and function were tested ex vivo and after in vitro expansion in 32 HBsAg-negative patients undergoing diagnostic liver biopsy for chronic hepatitis C: 18 with occult HBV infection (11 anti-HBc-negative and 7 anti-HBc-positive patients) defined by the detection of intrahepatic HBV DNA by polymerase chain reaction; 14 without detectable intrahepatic HBV DNA (5 anti-HBc-positive and 9 anti-HBc-negative patients). Six patients with chronic hepatitis B and 7 HBsAg-inactive carriers were studied for comparison.

RESULTS

The presence or absence of serologic HBV markers defined 2 profiles of HBV-specific T-cell responses in occult infection. Anti-HBc-positive patients showed a T-cell response typical of protective memory, suggesting that this condition represents a resolved infection with immune-mediated virus control. In contrast, HBV-specific T cells in anti-HBc-negative patients did not readily expand and produce interferon-gamma in vitro, suggesting the possibility of a low-dose infection insufficient to allow maturation of protective memory.

CONCLUSIONS

Our results suggest different mechanisms of control of viral replication in seropositive and seronegative occult infections. Additional studies aimed at understanding possible different clinical implications are needed.

Neutralization of hepatitis B virus (HBV) by human monoclonal antibody against HBV surface antigen (HBsAg) in chimpanzees

The virus neutralizing efficacy of HB-C7A, a human monoclonal antibody raised against the surface antigen of hepatitis B virus (HBsAg), was proved using hepatitis B virus (HBV)-naïve chimpanzees. One control chimpanzee which received 100CID(50) of HBV, subtype adw, without HB-C7A antibody became infected by HBV as evidenced by the appearance of HBV DNA on week 10 and subsequent appearance of HBsAg, anti-HBc and anti-HBs in the serum. Two experimental chimpanzees were inoculated intravenously with same dose of HBV as the control chimpanzee, which was previously incubated with 0.1mg and 10mg of HB-C7A antibody prior to inoculation. HBV infection was not observed in the antibody-treated chimpanzees during 12 months of follow-up, exhibiting neither detectable HBsAg nor anti-HBc antibody. This work demonstrates the neutralization of HBV by HB-C7A monoclonal antibody and shows the possibility of prevention of HBV infection using this antibody in liver transplantation and exposure to HBV.

Screening of human antibody Fab fragment against HBsAg and the construction of its dsFv form

The objective of this study was to pursue the techniques involving the screening of the human antibody Fab fragment against hepatitis B virus surface antigen (HBsAg) and the construction of its disulfide-stabilized Fv fragment (dsFv). The phage antibody Fab fragments against HBsAg were screened from the human combinatorial immunoglobulin library. Sequence analysis revealed that its heavy chain gene was complete, but the light chain gene was lost. To improve the affinity of the antibody by chain shuffling, a human antibody light chain gene repertoire was generated by reverse transcriptase-polymerase chain reaction (RT-PCR) from the human peripheral blood lymphocytes. A phage antibody sub-library was then constructed by inserting the light chain gene repertoire into the phagmid that contained the Fd gene. Five clones with appreciably higher absorbance than that of the original clones were obtained, which indicated that the affinity of the light chain-shuffled phage antibodies was improved. Then, the mutated genes of dsFv against HBsAg were constructed by using PCR-based point mutagenesis method. Purified V_H and V_L proteins were folded into a 25-kDa protein, designated as anti-HBsAg dsFv. ELISA and competition ELISA revealed that the dsFv maintained the specificity of the Fab by binding to HBsAg, even through with a lower binding activity. These results have facilitated the undertaking of further functional analyses of the constructed dsFv, and may therefore provide an improved technique for the production and application of dsFvs against HBsAg.

T cells redirected against hepatitis B virus surface proteins eliminate infected hepatocytes

BACKGROUND & AIMS

The final goal in hepatitis B therapy is eradication of the hepatitis B virus (HBV) replication template, the so-called covalently closed circular DNA (cccDNA). Current antiviral treatment of chronic hepatitis B depends on interferon alpha or nucleoside analogues inhibiting the viral reverse transcriptase. Despite treatment, cccDNA mostly persists in the host cell nucleus, continues to produce hepatitis B surface antigen (HBsAg), and causes relapsing disease. We therefore aimed at eliminating persistently infected hepatocytes carrying HBV cccDNA by redirecting cytolytic T cells toward HBsAg-producing cells.

METHODS

We designed chimeric T-cell receptors directed against HBV surface proteins present on HBV-infected cells and used them to graft primary human T cells with antibody-like specificity. The receptors were composed of a single chain antibody fragment directed against HBV S or L protein fused to intracellular signalling domains of CD3xi and the costimulatory CD28 molecule.

RESULTS

Our results show that these chimeric receptors, when retrovirally delivered and expressed on the cell surface, enable primary human T cells to recognize HBsAg-positive hepatocytes, release interferon gamma and interleukin 2, and, most importantly, lyse HBV replicating cells. When coincubated with HBV-infected primary human hepatocytes, these engineered, antigen-specific T cells selectively eliminated HBV-infected and thus cccDNA-positive target cells.

CONCLUSIONS

Elimination of HBV cccDNA-positive hepatocytes following antiviral therapy is a major therapeutic goal in chronic hepatitis B, and adoptive transfer of grafted T cells provides a promising novel therapeutic approach. However, T-cell therapy may also cause liver damage and therefore needs further preclinical evaluation.

Rational design of a multiepitope vaccine encoding T-lymphocyte epitopes for treatment of chronic hepatitis B virus infections

Protein sequences from multiple hepatitis B virus (HBV) isolates were analyzed for the presence of amino acid motifs characteristic of cytotoxic T-lymphocyte (CTL) and helper T-lymphocyte (HTL) epitopes with the goal of identifying conserved epitopes suitable for use in a therapeutic vaccine. Specifically, sequences bearing HLA-A1, -A2, -A3, -A24, -B7, and -DR supertype binding motifs were identified, synthesized as peptides, and tested for binding to soluble HLA. The immunogenicity of peptides that bound with moderate to high affinity subsequently was assessed using HLA transgenic mice (CTL) and HLA cross-reacting H-2(bxd) (BALB/c x C57BL/6J) mice (HTL). Through this process, 30 CTL and 16 HTL epitopes were selected as a set that would be the most useful for vaccine design, based on epitope conservation among HBV sequences and HLA-based predicted population coverage in diverse ethnic groups. A plasmid DNA-based vaccine encoding the epitopes as a single gene product, with each epitope separated by spacer residues to enhance appropriate epitope processing, was designed. Immunogenicity testing in mice demonstrated the induction of multiple CTL and HTL responses. Furthermore, as a complementary approach, mass spectrometry allowed the identification of correctly processed and major histocompatibility complex-presented epitopes from human cells transfected with the DNA plasmid. A heterologous prime-boost immunization with the plasmid DNA and a recombinant MVA gave further enhancement of the immune responses. Thus, a multiepitope therapeutic vaccine candidate capable of stimulating those cellular immune responses thought to be essential for controlling and clearing HBV infection was successfully designed and evaluated in vitro and in HLA transgenic mice.

The hepatitis B x antigen effector, URG7, blocks tumour necrosis factor α-mediated apoptosis by activation of phosphoinositol 3-kinase and β-catenin

Hepatitis B x antigen (HBxAg) contributes significantly to the pathogenesis of chronic infection and development of hepatocellular carcinoma. To discern some of its operative pathways, HepG2 cells were stably transduced with HBx or the bacterial chloramphenicol acetyltransferase (CAT) gene. Differential gene expression has previously revealed an upregulated gene, clone 7 (URG7), that conferred resistance to anti-Fas killing on HepG2X cells. Given that tumour necrosis factor alpha (TNFα) is also an important mediator of chronic hepatitis, and partially shares signalling with Fas, experiments were designed to test whether URG7 blocks TNFα killing of HepG2X cells. HepG2X cells expressing URG7 and HepG2 cells overexpressing URG7 in the absence of HBxAg were resistant to TNFα killing compared with HepG2CAT cells. URG7 small interfering RNA restored the sensitivity of HepG2X cells to TNFα killing. Killing was associated with the activation of caspases 3 and 8, suggesting that URG7 blocked these caspases. This resistance was also associated with activation of phosphoinositol 3-kinase/Akt. Given that Akt and HBxAg also activate β-catenin, experiments were designed to determine whether URG7 blocked apoptosis via activation of β-catenin. Both HBxAg and URG7 activated fragments of the β-catenin promoter, and also promoted expression of β-catenin target genes. Hence, URG7 inhibits TNFα-mediated killing by blocking one or more caspases in the apoptotic pathway and by activating phosphoinositol 3-kinase and β-catenin, thereby overriding the apoptotic signalling of TNFα. This suggests that URG7 helps to protect virus-infected hepatocytes during chronic hepatitis B virus infection.

Atopy in children with chronic hepatitis B virus infection

AIM

To investigate whether immune responses against chronic HBV infection in children have an effect on prevalence of allergic diseases and atopy.

METHODS

Children with chronic HBV infection [HBV carriage (group 1) and chronic hepatitis (group 2)] were screened for allergic diseases. The results were compared with age-matched controls (group 3).

RESULTS

The frequencies of doctor-diagnosed 'asthma', 'allergic rhinitis' and 'eczema' were 29.4%, 7.8% and 7.8% in group 1; 7.8%, 5.2% and 5.2% in group 2 and 12.4%, 9% and 2.8% in group 3, respectively. 'History of ever wheezing', doctor-diagnosed 'asthma' and 'eczema' were more common in group 1 than group 3 (p < 0.05 for all parameters), and 'history of ever wheezing' and 'doctor-diagnosed asthma' were more common in group 1 than group 2 (p < 0.05 for al parameters). Atopy was more common in group 1 (35.2%) than both groups 2 (15.7%) and 3 (18%) (p < 0.05 for all parameters). Vertical transmission was more common in patients with versus without atopy in HBV carrier group (33.3% vs. 9%, p < 0.05).

CONCLUSION

Immune responses in chronic HBV infection associated with carrier state may also lead to allergic diseases, which suggests the necessity of following these patients for the allergic diseases along with their viral reactivation.

Human monoclonal antibody against Hepatitis B virus surface antigen (HBsAg)

Hepatitis B virus (HBV) is one of the main pathogens responsible for hepatitis and hepatocellular carcinoma. Human plasma-derived Hepatitis B immune globulin (HBIG) is being used for prophylactic and liver transplantation currently. However, it may be necessary to replace a HBIG with a recombinant one because of limited availability of human plasma with high anti-HBsAg antibody titer and possible contamination of human pathogens. A Chinese hamster ovary (CHO) cell line, HB-C7A, was established which produces a fully human IgG1 that binds HBsAg. The HB-C7A exhibits approximately 2600 units/mg of antibody. The affinity (K(a)) of HB-C7A is 1.1 x 10(8) M(-1) by Biacore analysis and estimated 6.7-fold higher than that of Hepabig (a plasma-derived HBIG from Green Cross Corp., Yongin, Korea) by competition ELISA. The HB-C7A recognizes the conformational "a" determinant of HBsAg and binds HBV particle more efficiently than the Hepabig. The HB-C7A binds to HBV-infected human liver tissue but does not bind to normal human tissues. This HB-C7A has several advantages compared to plasma-derived Hepabig such as activity, safety and availability.

Chemoimmunotherapy of chronic hepatitis B virus infection in the woodchuck model overcomes immunologic tolerance and restores T-cell responses to pre-S and S regions of the viral envelope protein

Treatment of chronic hepatitis B virus (HBV) infection could combine potent antiviral drugs and therapeutic vaccines to overcome immunological tolerance and induce the recovery phenotype to protect against disease progression. Conventional vaccination of woodchucks chronically infected with the woodchuck hepatitis virus (WHV) elicited differential T-cell response profiles depending on whether or not carriers were treated with the potent antiviral drug clevudine (CLV), which significantly reduces viral and antigen loads. The differential T-cell responses defined both CLV-dependent and CLV-independent epitopes of the pre-S and S regions of the WHV envelope protein. Only combined treatment involving CLV and conventional vaccine therapeutically restored the T-cell response profile of chronic WHV carrier woodchucks to that seen in prophylactic vaccination and in recovery from acute WHV infection. The results have implications for mechanisms of immunological tolerance operating in chronic HBV infection and suggest that such combined chemoimmunotherapy may be useful for treatment of humans with chronic HBV infection.

The woodchuck as an animal model for pathogenesis and therapy of chronic hepatitis B virus infection

This review describes the woodchuck and the woodchuck hepatitis virus (WHV) as an animal model for pathogenesis and therapy of chronic hepatitis B virus (HBV) infection and disease in humans. The establishment of woodchuck breeding colonies, and use of laboratory-reared woodchucks infected with defined WHV inocula, have enhanced our understanding of the virology and immunology of HBV infection and disease pathogenesis, including major sequelae like chronic hepatitis and hepatocellular carcinoma. The role of persistent WHV infection and of viral load on the natural history of infection and disease progression has been firmly established along the way. More recently, the model has shed new light on the role of host immune responses in these natural processes, and on how the immune system of the chronic carrier can be manipulated therapeutically to reduce or delay serious disease sequelae through induction of the recovery phenotype. The woodchuck is an outbred species and is not well defined immunologically due to a limitation of available host markers. However, the recent development of several key host response assays for woodchucks provides experimental opportunities for further mechanistic studies of outcome predictors in neonatal- and adult-acquired infections. Understanding the virological and immunological mechanisms responsible for resolution of self-limited infection, and for the onset and maintenance of chronic infection, will greatly facilitate the development of successful strategies for the therapeutic eradication of established chronic HBV infection. Likewise, the results of drug efficacy and toxicity studies in the chronic carrier woodchucks are predictive for responses of patients chronically infected with HBV. Therefore, chronic WHV carrier woodchucks provide a well-characterized mammalian model for preclinical evaluation of the safety and efficacy of drug candidates, experimental therapeutic vaccines, and immunomodulators for the treatment and prevention of HBV disease sequelae.

Perforin and Granzymes Have Distinct Roles in Defensive Immunity and Immunopathology

Successful control of viral infection requires the host to eliminate the infecting pathogen without causing overt immunopathology. Here we showed that perforin (Prf1) and granzymes (Gzms) have distinct roles in defensive immunity and immunopathology in a well-established model of viral infection. Both Prf1 and Gzms drastically affected the outcome of murine cytomegalovirus (MCMV) infection. Viral titres increased markedly in both Prf1(-/-) and Gzma(-/-)Gzmb(-/-) mice, but Gzma(-/-)Gzmb(-/-) mice recovered and survived infection, whereas Prf1(-/-) mice did not. Indeed, infected Prf1-deficient hosts developed a fatal hemophagocytic lymphohistiocytosis (HLH)-like syndrome. This distinction in outcome depended on accumulation of mononuclear cells and T cells in infected Prf1(-/-) mice. Importantly, blocking experiments that clearly identified tumor necrosis factor-alpha (TNF-alpha) as the principal contributor to the lethality observed in infected Prf1(-/-) mice provided support for the clinical potential of such an approach in HLH patients whose disease is triggered by viral infection.

Anti-Golgi complex antibodies during pegylated-interferon therapy for hepatitis C

BACKGROUND/AIM

Pegylated interferon (Peg-IFN) plus ribavirin is the standard therapy for hepatitis C. Peg-IFN has several antiviral mechanisms, but its role in hepatitis C treatment seems to be related to its immunomodulatory effect. Ribavirin, an antiviral agent, potentiates IFN activity when added to it. Both drugs are associated with adverse reactions of different magnitudes. Autoimmune phenomena have been reported with this treatment. In this paper, we describe cases of ALT/GGT flares during Peg-IFN plus ribavirin treatment, which related to the appearance of anti-Golgi antibody and disease progress.

METHODS

We investigated three patients with hepatitis C and severe ALT/GGT flares during Peg-IFN and ribavirin treatment coinciding with anti-Golgi complex antibody as the only marker of autoimmunity. We then reviewed the medical files and tested anti-Golgi antibody in stored sera from 25 patients treated with conventional IFN and in 14 patients treated with Peg-IFN.

RESULTS

The three patients were male, over 45 years of age; all were relapsers and non-responders. Anti-Golgi antibody was positive during treatment coinciding with ALT/GGT flares but with hepatitis C virus (HCV)-RNA negativity, disappearing after stopping treatment, with normalization of ALT/AST levels. One patient had progression of fibrosis from F2 to F3 despite negativity of HCV-RNA. In the last group, only two patients treated with Peg-IFN experienced ALT/GGT flares but without anti-Golgi antibody

CONCLUSIONS

The presence of anti-Golgi complex antibody could be a marker of a temporary autoimmune phenomenon and progressive disease.

Immune modulation by helminthic infections: worms and viral infections

Helminthic infections occur worldwide, especially in developing countries. About one-quarter of the world's population, 1.5 billion, are infected with one or more of the major soil-transmitted helminths, including hookworms, ascarids, and whipworms. Schistosomes infect more than 200 million people worldwide with 600 million at risk in 74 countries. The interaction between helminths and the host's immune system provokes particular immunomodulatory and immunoregulatory mechanisms that ensure their survival in the host for years. However, these changes might impair the immunological response to bystander bacterial, viral, and protozoal pathogens and to vaccination. Modulation of the immune system by infection with helminthic parasites is proposed to reduce the levels of allergic responses and to protect against inflammatory bowel disease. In this review, we summarize the immunological milieu associated with helminthic infections and its impact on viral infections, mainly hepatitis B virus, hepatitis C virus, and human immunodeficiency virus in humans and experimental animals.

Fas ligand-mediated lethal hepatitis after rapid lysis of a localized natural killer cell lymphoma

Natural killer (NK) cell malignancies have been associated with neutropenia and disturbances of liver function tests, thought to be related to high levels of soluble Fas ligand (FasL) in the circulation. We report a case of fulminant hepatitis occurring 3 weeks after the initiation of salvage therapy by arginine butyrate and ganciclovir for refractory Epstein-Barr virus-positive NK cell lymphoma. Pathologic examination revealed disappearance of the NK tumor and massive liver injury caused by apoptosis of virtually all hepatocytes. Immunohistochemistry revealed an intense staining for FasL. To our knowledge, this is the first description of the occurrence of FasL-mediated lethal hepatitis after lysis of a NK cell lymphoma.