Understanding the immunopathogenesis of chronic hepatitis B virus: an Asian prospective

Immune response pattern varies with the natural history of chronic hepatitis B

BACKGROUND

Chronic hepatitis B is a highly heterogeneous disease that can be divided into four phases: Immune tolerant (IT), immune active (IA), inactive carrier (IC) and hepatitis B envelope antigen (HBeAg)-negative hepatitis (ENEG).

AIM

To investigate the immune status of natural killer (NK) and T cells in different phases of chronic hepatitis B.

METHODS

The frequency, phenotype and function of circulating NK cells, as well as nonantigen-specific and hepatitis B virus (HBV)-specific T cell responses were detected by flow cytometry in healthy and HBV-infected subjects.

RESULTS

The ability of NK cells to produce IFN-γ was markedly attenuated in HBV-infected patients overall but was less compromised in IC patients. Patients in the IT and IA phases also displayed significantly lower TNF-α production compared to healthy subjects. NK cells were phenotypically activated in the IA and ENEG phases, as evidenced by the upregulation of NKp44 in CD56^bright NK cells and CD69 in CD56^dim NK cells. Furthermore, global T-cells from the ENEG phase displayed a proinflammatory cytokine profile with upregulated IFN-γ and TNF-α expression, while this profile was suppressed in IT and IA patients. Finally, core and S antigen-specific T cell responses were significantly stronger after in vitro expansion in the IC phase compared to other phases.

CONCLUSION

Our findings demonstrate the changes in immune response pattern during the natural history of HBV infection. Both NK and T cells are functionally impaired in the IT and IA phases. With the spontaneous clearance of HBeAg and hepatitis B surface antigen decline, NK cell cytokine production and HBV-specific T responses are partially restored in IC phase, and the ENEG phase is dominated by nonantigen-specific T cell responses.

Taiwan consensus statement on the management of chronic hepatitis B

The experts of Taiwan Association for the Study of Liver (TASL) have actively participated and led the guidelines on hepatitis B virus (HBV) management by Asian Pacific Association for the Study of Liver (APASL) which is the first international association for the study of liver to publish the statement on HBV management before. However, there are more and more new data on the natural history and treatment of HBV infection in the past decade. These include new application of an old biomarker (quantitative HBsAg), clinical significance of HBV genotype and naturally occurring mutations, the role of non-invasive examination in evaluating severity of hepatic fibrosis, clinical significance of outcome calculators, new drug or new combination strategies towards more effective therapy and organ transplantation including liver and non-liver transplantation. It is time to publish the guidelines on HBV management of Taiwan. Hence, TASL have conducted an expert meeting to review, to discuss and to debate the relevant literatures, followed by draft the manuscript of HBV management guidelines and recommendations. The guidelines include general management, indications for fibrosis assessment, time to start or stop drug therapy, choice of drug to initiate therapy, when and how to monitor the patients during and after stopping drug therapy. Recommendations on the therapy of patients in special circumstances, including women in childbearing age, patients with antiviral drug resistance, concurrent viral infection, hepatic decompensation, patient receiving immune suppression or chemotherapy and patients in the setting of liver transplantation and hepatocellular carcinoma, are also included.

HBV-Derived Synthetic Long Peptide Can Boost CD4+ and CD8+ T-Cell Responses in Chronic HBV Patients Ex Vivo

Background

Vaccination with synthetic long peptides (SLP) is a promising new treatment strategy for chronic hepatitis B virus (CHB). SLP can induce broad T-cell responses for all HLA types. Here we investigated the ability of a prototype HBV-core (HBc)-sequence-derived SLP to boost HBV-specific T cells in CHB patients ex vivo.

Methods

HBc-SLP was used to assess cross-presentation by monocyte-derived dendritic cells (moDC) and BDCA1+ blood myeloid DC (mDC) to engineered HBV-specific CD8+ T cells. Autologous SLP-loaded and toll-like receptor (TLR)-stimulated DC were used to activate patient HBc-specific CD8+ and CD4+ T cells.

Results

HBV-SLP was cross-presented by moDC, which was further enhanced by adjuvants. Patient-derived SLP-loaded moDC significantly increased autologous HBcAg18-27-specific CD8+ T cells and CD4+ T cells ex vivo. HBV-specific T cells were functional as they synthesized tumor necrosis factor-alpha and interferon-gamma. In 6/7 of patients blockade of PD-L1 further increased SLP effects. Also, importantly, patient-derived BDCA1+ mDC cross-presented and activated autologous T-cell responses ex vivo.

Conclusions

As a proof of concept, we showed a prototype HBc-SLP can boost T-cell responses in patients ex vivo. These results pave the way for the development of a therapeutic SLP-based vaccine to induce effective HBV-specific adaptive immune responses in CHB patients.

Human leukocyte antigen (HLA-F) polymorphism is associated with chronic HBV infection

Human leukocyte antigen (HLA)-F has been involved in immune regulation of infectious diseases. However, the role of HLA-F polymorphisms in hepatitis B infection outcomes remains unclear. Here, we aimed to determine HLA-F polymorphism implication in chronic HBV. Genotype analysis was performed for three single nucleotide polymorphisms (SNPs) of HLA-F and one SNP of HLA-E using PCR-SSP, in 252 Tunisian patients with chronic HBV infection stratified according to their HBV DNA levels (140 patients with low HBV DNA levels < 2000 IU/mL and 112 patients with high HBV DNA levels ≥ 2000 IU/mL) and 240 healthy controls (CTRL). The three HLA-F SNPs (HLA-F*01:02, -F*01:03 and -F*01:04) have the same allelic and genotypic frequencies in patients and in CTRL. We reported a low HLA-F*01:02 and F*01:04 allelic frequencies in the Tunisian population; however, high HLA-F*01:03 allele frequencies were observed (17%). A significant association was found between the HLA-F*01:03 allele and decreased level of HBV DNA (P = 0.02 OR 0.56, 95% CI 0.35-0.92). No significant differences were observed in haplotype distribution between patients and CTRL. A significant association of HLA-F*01:03 with the level of HBV DNA suggests an important role of HLA-F in HBV replication control.

New horizon for radical cure of chronic hepatitis B virus infection

About 250 to 350 million people worldwide are chronically infected with hepatitis B virus (HBV), and about 700000 patients per year die of HBV-related cirrhosis or hepatocellular carcinoma (HCC). Several anti-viral agents, such as interferon and nucleos(t)ide analogues (NAs), have been used to treat this disease. NAs especially have been shown to strongly suppress HBV replication, slowing the progression to cirrhosis and the development of HCC. However, reactivation of HBV replication often occurs after cessation of treatment, because NAs alone cannot completely remove covalently-closed circular DNA (cccDNA), the template of HBV replication, from the nuclei of hepatocytes. Anti-HBV immune responses, in conjunction with interferon-γ and tumor necrosis factor-α, were found to eliminate cccDNA, but complete eradication of cccDNA by immune response alone is difficult, as shown in patients who recover from acute HBV infection but often show long-term persistence of small amounts of HBV-DNA in the blood. Several new drugs interfering with the life cycle of HBV in hepatocytes have been developed, with drugs targeting cccDNA theoretically the most effective for radical cure of chronic HBV infection. However, the safety of these drugs should be extensively examined before application to patients, and combinations of several approaches may be necessary for radical cure of chronic HBV infection.

Prolonged suppression of HBV in mice by a novel antibody that targets a unique epitope on hepatitis B surface antigen

OBJECTIVE

This study aimed to investigate the therapeutic potential of monoclonal antibody (mAb) against HBV as a novel treatment approach to chronic hepatitis B (CHB) in mouse models.

METHODS

Therapeutic effects of mAbs against various epitopes on viral surface protein were evaluated in mice mimicking persistent HBV infection. The immunological mechanisms of mAb-mediated viral clearance were systematically investigated.

RESULTS

Among 11 tested mAbs, a novel mAb E6F6 exhibited the most striking therapeutic effects in several HBV-persistent mice. Single-dose administration of E6F6 could profoundly suppress the levels of hepatitis B surface antigen (HBsAg) and HBV DNA for several weeks in HBV-transgenic mice. E6F6 regimen efficiently prevented initial HBV infection, and reduced viral dissemination from infected hepatocytes in human-liver-chimeric mice. E6F6-based immunotherapy facilitated the restoration of anti-HBV T-cell response in hydrodynamic injection (HDI)-based HBV carrier mice. Immunological analyses suggested that the Fcγ receptor-dependent phagocytosis plays a predominant role in E6F6-mediated viral suppression. Molecular analyses suggested that E6F6 recognises an evolutionarily conserved epitope (GPCK(R)TCT) and only forms a smaller antibody-viral particle immune complex with limited interparticle crosslinking when it binds to viral particles. This unique binding characteristic of E6F6 to HBV was possibly associated with its effective in vivo opsonophagocytosis for viral clearance.

CONCLUSIONS

These results provided new insight into understanding the therapeutic role and mechanism of antibody against persistent viral infection. The E6F6-like mAbs may provide a novel immunotherapeutic agent against human chronic HBV infection.

Enhanced functions of peripheral γδ T cells in chronic hepatitis B infection during interferon α treatment in vivo and in vitro

BACKGROUND

γδ T cells play an important role in infectious, autoimmune, or neoplastic diseases. Here, a study was conducted to investigate the dynamic changes in phenotype and function of peripheral γδ T cells in patients with chronic hepatitis B (CHB) during pegylated-interferon (pegIFN)-α treatment, and to explore their roles in IFN-α therapy.

METHODS

Total 15 CHB patients with pegIFN-α therapy and 6 healthy controls (HC) were enrolled in this study. Flow cytometry was used for the study of frequency of peripheral γδ T cells, subtypes, effector or memory γδ T cells, and also the IFN-γ+, TNF-α+, CD107a+ or Granzyme B+ γδ T cells in 10 patients at week 0, 4, 8, 12, 24, 36 and 48 of treatment. Another 5 CHB patients and 6 HC were recruited for the γδ T cell isolation, and gene expression in γδ T cells was evaluated before or after IFN-α treatment in vitro.

RESULTS

Although γδT cells decreased in CHB patients during pegIFN-α therapy, their capacities to produce TNF-α and to express CD107a were enhanced. More effector γδT cells (CD27-CD45RA+) were found in the response group than in non-response group. Furthermore, IFN-α boosted the expression of Mx2 and cytokine genes in γδT cells from CHB patients in vitro.

CONCLUSION

IFN-α could enhance the cytokine production or cytotoxicity potential of γδT cells in vivo and in vitro. The enhanced function of γδT cells might contribute to the effect of IFN-α treatment.

Circumventing failed antiviral immunity in chronic hepatitis B virus infection: triggering virus-specific or innate-like T cell response?

Therapeutic vaccination for the treatment of chronic hepatitis B has thus far been unsatisfactory. In this review, we discuss potential new therapeutic vaccination strategies and other immunotherapeutic approaches that aim to achieve efficient restoration of HBV immunity in chronically infected patients.

Kinetics of hepatitis B surface antigen loss in patients with HBeAg-positive chronic hepatitis B treated with tenofovir disoproxil fumarate

BACKGROUND & AIMS

In a study of 266 chronic hepatitis B e antigen (HBeAg)-positive patients, 23 experienced hepatitis B surface antigen (HBsAg) loss with up to 5 years of tenofovir disoproxil fumarate (TDF) treatment. HBsAg kinetics in patients with and without HBsAg loss and predictors of HBsAg loss were evaluated.

METHODS

HBsAg levels were quantified every 12 weeks. A multivariable regression analysis, involving prespecified baseline characteristics and on-treatment response parameters, was performed; a stepwise procedure identified independent predictors of HBsAg loss.

RESULTS

Among patients with HBsAg loss, 14 (61%), 1 (4%), 0 and 7 (30%) were genotypes A through D, respectively; 1 (4%) was genotype F. HBsAg loss was preceded by viral suppression (HBV DNA <29 IU/ml; n=23) and HBeAg loss (n=19). Among treated patients the strongest independent predictors of HBsAg loss were Caucasian race with genotype A/D and ⩽4 years of infection (HR=14.3, 95% confidence interval [CI] 4.7-43.4; p<0.0001) and an HBsAg decline of ⩾1 log10 IU/ml at week 24 (HR=13.7, 95% CI 5.6-33.7; p<0.0001). Among TDF-treated patients, a reduction in HBsAg level of ⩾1-log10 by week 12 or 24 had a positive predictive value of 35%-45%, respectively, and a negative predictive value of 94%-97%, respectively.

CONCLUSIONS

HBsAg loss in HBeAg-positive patients receiving TDF involves a chronology of virologic and serologic responses; patients with HBV genotypes A or D and a rapid early decline in HBsAg are more likely to lose HBsAg.

CD8+ T cell responses specific for hepatitis B virus core protein in patients with chronic hepatitis B virus infection

BACKGROUND

Chronic hepatitis B virus (HBV) infection includes a set of heterogeneous clinical patterns, and core-protein-specific T cell response is important for virus control and disease progression, yet is not well elucidated.

OBJECTIVES

To analyze the phenotypic and functional profiles of HBV-core-protein-specific CD8+ T cells in different clinical patterns of chronic HBV infection.

STUDY DESIGN

A total of 46 HBV patients were recruited and classified according to their clinical status. CD8+ T cell responses in different patterns of chronic HBV infections were tested with flow cytometry using overlapping 15-mer peptides covering HBV core protein. Meanwhile, the CCR7/CD27 phenotypes of these CD8+ T cells were also determined.

RESULTS

Frequencies of gamma interferon (IFN-γ) positive CD8+ T cells in inactive HBV surface antigen (HBsAg) carriers in response to the core protein peptide pools were generally stronger than those of chronic HBV carriers and resolved individuals, especially with regards to peptide pool C13-C24. Moreover, phenotypic studies further highlighted the group of CD8+ CCR7-CD27+ T memory cells, which showed significantly higher levels of IFN-γ secretion in inactive HBsAg carriers than those in chronic hepatitis B patients, chronic HBV carriers and resolved individuals.

CONCLUSIONS

Core-protein-specific T cell response plays an important role in chronic HBV infection. Inactive HBsAg carriers showed a much stronger core-protein-specific cytotoxic T cell response than other types of chronically infected patients. CD8+ CCR7-CD27+ T memory lymphocytes may be crucial in the immune pathogenesis of chronic HBV infection.

Hepatitis B virus lineages in mammalian hosts: Potential for bidirectional cross-species transmission

The hepatitis B virus (HBV) is a cosmopolitan infectious agent currently affecting over 350 million people worldwide, presently accounting for more than two billion infections. In addition to man, other hepatitis virus strains infect species of several mammalian families of the Primates, Rodentia and Chiroptera orders, in addition to birds. The mounting evidence of HBV infection in African, Asian and neotropical primates draws attention to the potential cross-species, zoonotic transmission of these viruses to man. Moreover, recent evidence also suggests the humans may also function as a source of viral infection to other mammals, particularly to domestic animals like poultry and swine. In this review, we list all evidence of HBV and HBV-like infection of nonhuman mammals and discuss their potential roles as donors or recipients of these viruses to humans and to other closely-related species.

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.

Cumulative viral evolutionary changes in chronic hepatitis B virus infection precedes hepatitis B e antigen seroconversion

OBJECTIVE

To examine viral evolutionary changes and their relationship to hepatitis B e antigen (HBeAg) seroconversion.

DESIGN

A matched case-control study of HBeAg seroconverters (n = 8) and non-seroconverters (n = 7) with adequate stored sera before seroconversion was performed. Nested PCR, cloning and sequencing of hepatitis B virus (HBV) precore/core gene was performed. Sequences were aligned using Clustal X2.0, followed by construction of phylogenetic trees using Pebble 1.0. Viral diversity, evolutionary rates and positive selection were then analysed.

RESULTS

Baseline HBV quasispecies viral diversity was identical in seroconverters and non-seroconverters 10 years before seroconversion but started to increase approximately 3 years later. Concurrently, precore stop codon (PSC) mutations appeared. Some 2 years later, HBV-DNA declined, together with a dramatic reduction in HBeAg titres. Just before HBeAg seroconversion, seroconverters had HBV-DNA levels 2 log lower (p = 0.008), HBeAg titres 310-fold smaller (p = 0.02), PSC mutations > 25% (p < 0.001), viral evolution 8.1-fold higher (p = 0.01) and viral diversity 2.9-fold higher (p < 0.001), compared to non-seroconverters, with a 9.3-fold higher viral diversity than baseline (p = 0.011). Phylogenetic trees in seroconverters showed clustering of separate time points and longer branch lengths than non-seroconverters (p = 0.01). Positive selection was detected in five of eight seroconverters but none in non-seroconverters (p = 0.026). There was significant negative correlation between viral diversity (rs = -0.60, p < 0.001) and HBV-DNA or HBeAg (rs = -0.58, p = 0.006) levels; and positive correlation with PSC mutations (rs = 0.38, p = 0.009). Over time, the significant positive correlation was viral diversity (rs = 0.65, p < 0.001), while negative correlation was HBV-DNA (rs = -0.627, p < 0.001) and HBeAg levels (rs = -0.512, p =0.015).

CONCLUSIONS

Cumulative viral evolutionary changes that precede HBeAg seroconversion provide insights into this event that may have implications for therapy.

The effect of HLA-DQB1 alleles on virologic breakthroughs during chronic hepatitis B treatment with genetically low barrier drugs

BACKGROUND

Chronic hepatitis B treatment with oral antiviral drugs is a long course. During this course, antiviral resistance is a serious issue, particularly, if genetically low barrier drugs are in use. Host immunity is accepted to have an effect on antiviral resistance development. The earliest clinical sign of drug resistance is virologic breakthrough. In this study, we aimed to investigate the relation between HLA-DQB1 alleles and virologic breakthrough events.

SUBJECTS AND METHODS

The patient records at single institution hepatology clinic were reviewed. Local institution ethics committee approval was taken. The patients' demographic data, virologic parameters, treatment statues were noted. Patients who had received lamivudine or adefovir were recruited and grouped into two according to virologic breakthrough occurrence. Patients who were not compliant to the given treatment were excluded. Blood samples were taken for DNA extraction. HLA-DQB1 alleles were determined at high level by sequence-specific primers-polymerase chain reaction. The distribution of DQB1 alleles among groups was analyzed.

RESULTS

One hundred ninety-eight patients were eligible for the study. Ninety-six of them had virologic breakthrough where 102 did not have. DQB1 0503 allele was more frequent in patients without breakthrough (28.4% vs. 12.4%, P=0.006). In univariate analysis, HBeAg seropositivity (P<0.001), absence of cirrhosis (P=0.007), younger age (P=0.002) and higher pretreatment logDNA (P<0.001) were related to breakthrough events. However, in multivariate analysis only logDNA (P<0.001) and DQB1*0503 (P=0.02) allele revealed statistically significant relation with breakthrough events.

CONCLUSION

Host immunity may have an effect on outcome during treatment with oral antiviral drugs. A patient with better immunologic profile may suppress the viral replication better and this may cause less resistance occurrence during treatment with genetically low barrier drugs.

Repeated exposure to trace amounts of woodchuck hepadnavirus induces molecularly evident infection and virus-specific T cell response in the absence of serological infection markers and hepatitis

Exposure to multiple small doses of hepatitis B virus (HBV) is a frequent occurrence in high-risk groups, including close relatives of infected individuals, primary care givers, and intravenous drug users. It remains uncertain whether such repeated contact may culminate in a symptomatic infection coinciding with hepatitis in individuals not immunoprotected. In this study, we evaluated consequences of multiple exposures to small, liver-nonpathogenic amounts of infectious hepadnavirus in the woodchuck model of hepatitis B. Virus-naïve animals were intravenously injected with 6 weekly doses of 110 DNase digestion-protected virions of woodchuck hepatitis virus (WHV), injected again with 6 weekly 110-virion doses after 7.5 months, and then challenged or not with a liver-pathogenic dose of 1.1 × 10(6) virions of the same inoculum. The data revealed that two rounds of such repeated exposure did not result in serologically evident infection or hepatitis. However, a low-level WHV DNA-positive infection accompanied by a WHV-specific T cell response in the absence of antiviral antibody reactivity was established. The kinetics of the virus-specific and mitogen-induced (generalized) T cell responses and the inability to induce immunoprotection against challenge with a large, liver-pathogenic virus dose were closely comparable to those previously reported for occult infection initiated by a single liver-nonpathogenic dose of WHV. Thus, repeated exposures to small quantities of hepadnavirus induce molecularly evident but serologically silent infection that does not culminate in hepatitis or generate immune protection. The findings imply that the HBV-specific T cell response encountered in the absence of serological markers of infection likely reflects ongoing occult infection.

Skewed T-cell receptor beta chain variable gene (TCRBV) usage among different clinical types of patients with chronic HBV infection

This study aimed to determine the degree of clonal expansion of T cells in peripheral blood mononuclear cells (PBMCs) isolated from patients suffering from different clinical types of hepatitis B (HB) infection and to analyse the clinical relevance of the skewed T-cell receptor beta variable (TCRBV). Sera and PBMCs were collected from 90 HB patients. Gene melting spectral pattern (GMSP) analysis was used to determine the distribution and expansion of populations expressing specific TCRBV complementary determined region 3 (CDR3) genes. TCRBV genes associated with monoclonal expansion were sequenced. TCRBV families from the majority of patients (80/90) displayed skewed T-cell expansion. Furthermore, TCRBV11, BV12 and BV13.1 were more frequent than other TCRBV genes; the sequence of TCRBV11 CDR3 was expressed as 'VYNEQ' in all patients and was accompanied by the BJ2.1 fragment. In patients with chronic HB, the frequency of skewed TCRBV was inversely correlated with hepatitis B virus (HBV) DNA levels. The persistently skewed TCRBV gene families in HB patients may be associated with the development and maintenance of hepatitis. GMSP analysis of TCRBV gene families may be helpful in estimating disease status, and BV11 may be associated with HBV replication in patients with chronic HBV infection.

Persistent hepatitis B viral replication in a FVB/N mouse model: impact of host and viral factors

The mechanism underlying the chronicity of hepatitis B virus (HBV) infection has long been an interesting question. However, this mechanism remains unclear largely due to the lack of an animal model that can support persistent HBV replication and allow for the investigation of the relevant immune responses. In this study, we used hydrodynamic injection to introduce HBV replicon DNA into the livers of three different mouse strains: BALB/c, C57BL/6, and FVB/N. Interestingly, we found that an HBV clone persistently replicated in the livers of FVB/N mice for up to 50 weeks but was rapidly cleared from the livers of BALB/c and C57BL/6 mice. Flow cytometric analysis and quantitative reverse transcription PCR analysis of the mouse livers indicated that after DNA injection, FVB/N mice had few intrahepatic activated cytotoxic T lymphocytes (CTLs) and produced low levels of alanine aminotransferase, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, and the CXCL9 and CXCL10 chemokines. These findings were in sharp contrast with those observed in BALB/c and C57BL/6 mice, reflecting a strong correlation between the degree of liver inflammation and viral clearance. Mutational analysis further demonstrated that a change of Asn-214 to Ser-214 in the HBV surface antigen rendered the persistent HBV clone clearable in FVB/N mice, which was accompanied by increased levels of activated CTL and upregulated expression of IFN-γ, CXCL9, and CXCL10 in the livers. These results indicate that the heterogeneity of the host factors and viral sequences may influence the immune responses against HBV. An inadequate activation of immune or inflammatory responses can lead to persistent HBV replication in vivo.

Heat shock protein gp96 enhances humoral and T cell responses, decreases Treg frequency and potentiates the anti-HBV activity in BALB/c and transgenic mice

More than 350 million people worldwide are chronically infected with hepatitis B virus (HBV). Broad repertoire and strong magnitude of HBV-specific T cell responses are thought to play key roles for virus control and clearance. Previous studies together with ours showed that heat shock protein gp96 as adjuvant induces antigen specific T cell responses, yet little is known for its anti-viral properties. Here, we investigated the role of gp96 mediated cellular and humoral immunity in antiviral effects in HBV transgenic mice. Immunization with HBV surface (HBsAg) and core (HBcAg) antigens combined formulation along with gp96 induced robust antiviral T-cell and antibody immunity against HBsAg and HBcAg. Compared with non-immunized control, immunization with gp96 adjuvant vaccine led to decrease of serum HBs level and HBc expression in hepatocyte by 45% and 90% at maximum, respectively, and decreased serum HBV-DNA level to below or close to the detection limit 4 weeks after the last immunization, suggesting the therapeutic effect. A significant enhancement in cellular responses towards HBcAg and increased infiltration of CD8+ T cells in liver of transgenic were observed under treatment with gp96 compared with no treatment (P<0.05 or 0.01). Treatment with gp96 was capable of reducing Tregs by overall 30-40%. The superior immune responses induced with the aid of gp96 correlated with improved antiviral effect by vaccination with HBsAg and HBcAg. We conclude that gp96 may contribute to enhanced antiviral immunity in transgenic mice at least partly by Treg down-regulation. HBcAg may act as potent adjuvant for Th1 response. Our study reveals the novel property of gp96 in immune modulation and its potential use for breaking immunotolerance in immunotherapy of chronic HBV infection.

Kinetics of immune responses to hepatitis B virus infection

The pathogenesis of hepatitis B is mainly triggered by the host's cellular immune responses to hepatitis B virus (HBV) infection, and the immune responses against the virus depends on the interaction of various immune cells. Current research of immunity to hepatitis B infection mainly focuses on understanding the differences between patients who can control HBV infection and those with persistent infection. In this paper, we analyze how immunological events influence the development of innate and adaptive immunity needed to control HBV infection and explore the mechanisms by which high levels of viral antigens, CD4⁺ T cells, programmed death 1 (PD-1), the presence of regulatory T cells, and impaired dendritic cell functions maintain the HBV-specific immunological failure.

Evolution of hepatitis B genotype C viral quasi-species during hepatitis B e antigen seroconversion

BACKGROUND & AIMS

Although the evolution of viral quasi-species may be related to the pathological status of disease, little is known about this phenomenon in hepatitis B, particularly with respect to hepatitis B e antigen (HBeAg) seroconversion.

METHODS

Nucleotide sequences of the hepatitis B virus (HBV) X/precore/core region was analyzed at five time-points in four groups of chronic hepatitis B patients, interferon-induced seroconverters (IS, N = 9), interferon non-responders (IN, N = 9), spontaneous seroconverters (SS, N = 9), and non-seroconverters (SN, N = 9) followed during 60 months on an average. Only patients with genotype C were studied.

RESULTS

Analysis of 1800 nucleotide sequences showed that there was no statistical difference between the nucleotide genetic distances of seroconverters (IS and SS; 6.9 × 10⁻³ substitutions (st)/site and 6.7 × 10⁻³ st/site, respectively) and those of non-seroconverters (IN and SN; 5.3 × 10⁻³ st/site and 3.8 × 10⁻³ st/site, respectively) before seroconversion. Compared to non-seroconverters (IN and SN; 5.1 × 10⁻³ st/site and 5.9 × 10⁻³ st/site, respectively), the sequence diversity of seroconverters (IS and SS; 10.9 × 10⁻³ st/site and 9.9 × 10⁻³ st/site, respectively) was significantly higher after seroconversion (p < 0.05), and was higher in seroconverters after seroconversion than before seroconversion (p < 0.05), while this changed very little in non-seroconverters during the observation period. Phylogenetic trees showed greater complexity in secoconverters than non-seroconverters. Parsimony-based estimation of the direction of sequence change between descendants and ancestors before HBeAg seroconversion, revealed higher frequencies of transversional A to T substitution in seroconverters (0.06 vs. 0.02, p = 0.0036) that coincided with the dynamics of quasi-species possessing A1762T mutation.

CONCLUSIONS

The distinctly greater viral diversity in HBeAg seroconverters after seroconversion could be related to escape mutants resulting from stronger selection pressure.

Role of HLA allele polymorphism in chronic hepatitis B virus infection and HBV vaccine sensitivity in patients from eastern Turkey

Human leukocyte antigen (HLA) alleles have been associated with the clinical outcomes of hepatitis B virus (HBV) infection, which range from spontaneous recovery to hepatocellular carcinoma. In this study involving subjects from eastern Turkey, the frequencies of HLA-B35, HLA-CW4, HLA-DQ2, and HLA-DQ8 were markedly higher in the chronic HBV group than those in the spontaneously recovered group; the frequencies of HLA-A11 and HLA-A24 in the nonresponsive HBV vaccine group were markedly higher than those in the responsive HBV vaccine group; and the frequency of HLA-CW6 in the nonresponsive HBV vaccine group was significantly lower than in the responsive group. A complete understanding of HLA types associated with the progression to chronic HBV infection and their effects within the cell at the molecular level will be an important contribution in the development of new HBV vaccines and new treatment strategies for chronic HBV infection.

Inhibitory KIR and specific HLA-C gene combinations confer susceptibility to or protection against chronic hepatitis B

Antiviral activity of natural killer (NK) cells is regulated partially through inhibitory and activating killer cell immunoglobulin-like receptors (KIR) interacting with human leukocyte antigen C (HLA-C) ligands. The highly polymorphic nature of HLA-C and KIR genes endows individuals with diverse HLA-C/KIR combinations, which may confer susceptibility to or protection against a certain challenge. We analyzed the genes encoding KIR receptors and HLA-C ligands and HLA-C/KIR combinations in patients with chronic hepatitis B and healthy subjects. We found that inhibitory receptor KIR2DL1 in combination with HLA-C2 ligand confers susceptibility to chronic hepatitis B (CHB), whereas inhibitory receptor KIR2DL3 or KIR2DL3 homozygote in the presence of HLA-C1C1 genotype shows protection against CHB. Our data reveal that inhibitory NK cell interactions are important in determining antiviral immunity and that distinct affinity inhibitory responses will exert different impact on the development of CHB.

miR-122-induced down-regulation of HO-1 negatively affects miR-122-mediated suppression of HBV

As the most abundant liver-specific microRNA (miRNA), miR-122 has been extensively studied for its role in the regulation of lipid metabolism, hepatocarcinogenesis and hepatitis C virus (HCV) replication, but little is known regarding its role in the replication of Hepatitis B virus (HBV), a highly prevalent hepatotropic virus that can cause life-threatening complications. In this study we examined the effects of antisense inhibition of miR-122 and transfection of a miR-122 mimic on HBV expression in hepatoma cells. The over-expression of miR-122 inhibited HBV expression, whereas the depletion of endogenous miR-122 resulted in increased production of HBV in transfected cells. We further found that the down-regulation of Heme oxygenase-1 (HO-1) by miR-122 plays a negative role in the miR-122-mediated inhibition of viral expression. Our study demonstrates the anti-HBV activity of miR-122, suggesting that therapies that increase miR-122 and HO-1 may be an effective strategy to limit HBV replication.

On-treatment monitoring of chronic hepatitis B virus infection: an Asian-Pacific perspective

Chronic infection with hepatitis B virus (HBV) is a major global health problem and an important cause of morbidity and mortality from sequelae of liver cirrhosis and hepatocellular carcinoma. In the past decades, better understanding of the natural history and immunopathogenesis of chronic HBV infection and of the development of many powerful antiviral agents has allowed us to improve therapeutic efficacy. Among these agents, nucleos(t)ide analogs are important and potent viral suppressors. However, when administered alone, they are not able to permanently eradicate HBV, and long-term maintenance therapy is required for therapeutic efficacy. Additionally, prolonged treatment is frequently associated with the emergence of drug-resistant HBV mutants. Before an 'ideal' drug(s), or drug combination, with optimal antiviral efficacy and negligible rates of drug resistance becomes available, the on-treatment monitoring approach using serum HBV DNA level as a predictor for therapeutic efficacy and drug resistance is useful. However, most countries in the Asia-Pacific region have low income economies, insufficient medical care systems, and low awareness of the disease among the general population and government officers. The easy approach of the road-map concept using an affordable drug to treat chronic HBV infection is more important in this region. There is already evidence that the long-term outcomes of chronic HBV infection can be improved under well-managed antiviral therapy. Profound and long-lasting suppression of HBV replication, either maintained on-therapy or sustained after stopping therapy, has been identified as the key determinant for achieving the goals of therapy, for reducing liver damage, and for preventing development of cirrhosis and/ or hepatocellular carcinoma.

Toward elimination and eradication of hepatitis B

Hepatitis B virus (HBV) causes important human health problems. It has infected one-third of the world's population and approximately 360 million people are chronic carriers. Worldwide, 0.5-1.2 million deaths are attributed to HBV infection annually. Therefore, global control of HBV infection is important. HBV infection can be intervened by interrupting routes of transmission, treating the chronically infected, and preventing the susceptibles with immunoprophylaxis. All these measures are effective. Nevertheless, although pegylated interferons or nucleos(t)ide analogs are effective for the treatment of chronic hepatitis B, chronic carriage of HBV is not easy to eliminate, as revealed by the frequent persistence of hepatitis B surface antigen, despite satisfactory responses to these treatments. On the other hand, hepatitis B vaccination has been shown to preclude HBV infection effectively. This is particularly true for pre-exposure prophylaxis. Worthy of note is the universal vaccination of newborn infants. This is the most effective means of preventing HBV infection, especially for those born to HBV carrier mothers. To eliminate and eradicate hepatitis B, first, HBV in the chronically infected should be eradicated or strongly and efficiently suppressed, so that the infection does not spread rampantly. Second, all the transmission routes should be interrupted. Lastly, but most effectively, is to immunize all susceptibles. The difficulties and possible solutions of each approach are discussed. In conclusion, the existing means to prevent and treat HBV infection render our goal toward eliminating and eradicating hepatitis B possible, although it will take much time and effort to achieve this objective.

Correlation of circulating TLR2/4 expression with CD3+/4+/8+ T cells and Treg cells in HBV-related liver cirrhosis

Toll-like receptors (TLRs) 2 and 4 play a key role in chronic hepatitis B virus (HBV) infection. However, the role of TLRs in the pathogenesis of HBV-related liver cirrhosis and their regulation of the innate immune response of patients with liver cirrhosis remain unknown. To assess the contribution of TLR2/4 in HBV-related liver cirrhosis, we examined the expression of circulating TLR2 and TLR4 on peripheral blood mononuclear cells (PBMCs), CD4(+)CD25(+)CD127(low/-) Treg proportions, and CD3(+)/CD4(+)/CD8(+) T-cell counts in 30 liver cirrhosis patients, 21 chronic hepatitis B (CHB) patients, and 16 normal controls (NC). Furthermore, we analyzed the relationship between TLR2/4 expression and Treg proportions and T-cell counts. We show that the expression of TLR2 and TLR4 was significantly upregulated in patients with liver cirrhosis compared to NC. TLR4 expression was significantly increased in patients with liver cirrhosis compared to patients with CHB, and for TLR2 expression there were no differences between them. TLR4 expression showed a significant positive correlation with the frequency of Tregs in liver cirrhosis patients. TLR2 expression negatively correlated with CD3(+)/CD4(+)/CD8(+) T-cell counts and HBV viral load in patients with liver cirrhosis. These findings indicate that TLR may be involved in the pathogenesis of HBV-related liver cirrhosis, and may interact with Tregs and CD3(+)/CD4(+)/CD8(+) T cells in the immune response during HBV-related liver cirrhosis.

Host immunity influences disease progression and antiviral efficacy in humans infected with hepatitis B virus

Hepatitis B virus (HBV) infection can lead to several severe liver diseases, including hepatitis, cirrhosis and hepatocellular carcinoma, although the underlying mechanisms responsible for the clinical outcome have not been well characterized. In this review, we retrospectively examine the history of immunological responses to HBV infection and summarize the current understanding of innate and adaptive immunity in the context of HBV-associated liver disease. Recent data indicate that the interaction between HBV and the host immune response not only substantially drives disease progression, but also significantly influences antiviral efficacy in HBV-infected individuals. Advances in the field have provided insight into the immunopathology of HBV infection. Based on the characteristics of host immune responses in patients with HBV infection, a 'climbing slope hypothesis' is proposed to suggest that therapeutic strategies aimed at modulating the immune activity of the host may represent a complementary approach to antiviral drug treatment for the management of chronically HBV-infected patients.

Profile of tumor antigen-specific CD8 T cells in patients with hepatitis B virus-related hepatocellular carcinoma

BACKGROUND & AIMS

Tumor and viral antigens are expressed by hepatocellular carcinoma (HCC) in patients with chronic hepatitis B, but little is known about the immunodominance and function of tumor- and virus-specific CD8+ T cells in these patients.

METHODS

HLA-A2-restricted T-cell responses to 16 tumor antigens and hepatitis B virus (HBV) proteins were tested using 49 previously described epitopes. Cells from 30 HLA-A2+, HBV-infected patients (10 with HCC, 10 with HBV cirrhosis, and 10 HBV but no cirrhosis) were analyzed, after expansion, by enzyme-linked immunosorbent spot (ELISPOT). Interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-2 production, as well as expression of the degranulation marker CD107a on tumor-specific CD8+ T cells, were evaluated.

RESULTS

Cells from all groups had tumor-specific responses. The tumor antigens NY-ESO-1 and SSX-2 were most frequently targeted and were immunogenic in the HLA-A2 subtypes that are characteristic of Asian ethnicity. Tumor-specific T cells had low affinities; T cells from non-HCC patients were polyfunctional (IFN-gamma+, TNF-alpha+, CD107a+) and those from HCC patients displayed an exhausted phenotype (IFN-gamma+, CD107a+). Programmed Death 1 (PD-1) was expressed at higher levels on T cells from tumor and liver than peripheral blood from HCC patients and might contribute to T-cell exhaustion. Blocking PD-1/PD-L1 increased the frequency of tumor-specific T cells in HCC patients but did not restore T cell function.

CONCLUSIONS

Patients with or without HCC have a quantitative and functional hierarchy of tumor-specific T cells. HLA-A2-restricted T cells from HCC patients target NY-ESO-1, but exist in an exhausted state that might require additional activation to restore function.

Dynamic decrease in PD-1 expression correlates with HBV-specific memory CD8 T-cell development in acute self-limited hepatitis B patients

BACKGROUND/AIMS

Programmed death-1 (PD-1) upregulation can impair virus-specific CD8 T-cell responses during chronic viral infection. Whether and how PD-1 affects virus-specific memory CD8 T cells in humans with acute viral infection, however, remains largely undefined.

METHODS

The association between PD-1 expression and HBV-specific memory CD8 T-cell responses were longitudinally analyzed in eighteen patients with acute hepatitis B virus (HBV) infection, including ten patients with human leucocyte antigen (HLA)-A201 and eight with other HLA-A2 subtypes.

RESULTS

At clinical onset, PD-1 was significantly up-regulated and subsequently led to the functional suppression of HBV-specific effector CD8 T cells, as blocking PD-1/PD-L1 interactions in vitro enhanced their proliferation and IFN-gamma production. Following disease resolution, HBV-specific effector CD8 T cells developed into memory T cells. During this period, the dynamic PD-1 decrease was numerically correlated with the reduction of HBV-specific CD8 T-cell frequency, phenotypically with an acquisition of CCR7, CD45RA and CD127 expressions, and functionally with the increase in proliferation and IFN-gamma production of the memory T cells.

CONCLUSIONS

PD-1-mediated inhibitory signaling not only attenuates HBV-specific CD8 T-cell effector function during the acute phase of infection but also correlates with the development of HBV-specific memory CD8 T cells following disease resolution.