Cells In Hepatitis B Virus Infection Research Articles

Clinical implications of hepatitis B virus core antigen-mediated immunopathologic T cell responses in chronic hepatitis B.

Hepatitis B virus (HBV) infection significantly impacts Asian populations. The influences of continuous HBV antigen and inflammatory stimulation to T cells in chronic hepatitis B (CHB) remain unclear. In this study, we first conducted bioinformatics analysis to assess T-cell signaling pathways in CHB patients. In a Taiwanese cohort, we examined the phenotypic features of HBVcore -specific T cells and their correlation with clinical parameters. We used core protein overlapping peptides from the Taiwan prevalent genotype B HBV to investigate the antiviral response and the functional implication of HBV-specific T cells. In line with Taiwanese dominant HLA-alleles, we also evaluated ex vivo HBVcore -specific T cells by pMHC-tetramers targeting epitopes within HBV core protein. Compared to healthy subjects, we disclosed CD8 T cells from CHB patients had higher activation marker CD38 levels but showed an upregulation in the inhibitory receptor PD-1. Our parallel study showed HBV-specific CD8 T cells were more activated with greater PD-1 expression than CMV-specific subset and bulk CD8 T cells. Moreover, our longitudinal study demonstrated a correlation between the PD-1 fluctuation pattern of HBVcore -specific CD8 T cells and liver inflammation in CHB patients. Our research reveals the HBV core antigen-mediated immunopathologic profile of CD8 T cells in chronic HBV infection. Our findings suggest the PD-1 levels of HBVcore -specific CD8 T cells can be used as a valuable indicator of personal immune response for clinical application in hepatitis management.

Function and autophagy of monocyte-derived dendritic cells is affected by hepatitis B virus infection

BackgroundThe role of dendritic cells and the autophagy state of dendritic cells in the immune response of hepatitis B virus (HBV) infection was still controversial. In this study, we carefully examined the phenotype, function and autophagy pathway of dendritic cells in HBV infection.MethodsMonocyte-derived dendritic cells from healthy blood donors and patients with chronic HBV infection were stimulated by lipopolysaccharide, supernatant of HepG2.2.15 cells or supernatant of HepG2 cells respectively. Phenotype of dendritic cells was examined by flow cytometry and cytokines secretion was detected by enzyme-linked immunosorbent assay. Autophagy related proteins were detected by western blot and immunofluorescence analysis.ResultsOur results showed that the expression of both major histocompatibility complex II molecules and co-stimulated molecules including cluster of differentiation antigen 80, cluster of differentiation antigen 86 in the monocyte-derived dendritic cells from patients with chronic HBV infection was significantly higher than that from healthy donors when cultured with supernatant of HepG2.2.15 cells. The amount of cytokines, including tumour necrosis factor-α, interleukin-10 and interleukin-12, secreted by monocyte-derived dendritic cells from patients with chronic HBV infection was also significantly higher than that from healthy donors when stimulate by HBV. Interestingly, the expression level of autophagy-related proteins including autophagy-related protein5 and associated protein 1 light chain in dendritic cells from patients with chronic HBV infection was significantly increased when compared with that from healthy donors when re-exposed to HBV.ConclusionsOur results indicated that dendritic cells from patients with chronic HBV infection could intensively present antigen and express co-stimulatory molecules. The increased activation of dendritic cells might be related to the enhanced autophagy of dendritic cells in HBV infection.

The Multiple Facets and Disorders of B Cell Functions in Hepatitis B Virus Infection

Chronic hepatitis B virus (HBV) infection continues to be a global public health burden. B cells play a pivotal role in mediating HBV clearance and can participate in the development of anti-HBV adaptive immune responses through multiple mechanisms, such as antibody production, antigen presentation, and immune regulation. However, B cell phenotypic and functional disorders are frequently observed during chronic HBV infection, suggesting the necessity of targeting the disordered anti-HBV B cell responses to design and test new immune therapeutic strategies for the treatment of chronic HBV infection. In this review, we provide a comprehensive summary of the multiple roles of B cells in mediating HBV clearance and pathogenesis as well as the latest developments in understanding the immune dysfunction of B cells in chronic HBV infection. Additionally, we discuss novel immune therapeutic strategies that aim to enhance anti-HBV B cell responses for curing chronic HBV infection.

Phenotypic CD8 T cell profiling in chronic hepatitis B to predict HBV-specific CD8 T cell susceptibility to functional restoration in vitro

ObjectiveExhausted hepatitis B virus (HBV)-specific CD8 T cells in chronic HBV infection are broadly heterogeneous. Characterisation of their functional impairment may allow to distinguish patients with different capacity to control...

Diverse Functions of γδ T Cells in the Progression of Hepatitis B Virus and Hepatitis C Virus Infection.

Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are primary risk factors for a wide spectrum of liver diseases that severely affect human health. The liver is an immunological organ that has an abundance of immune cells. Thus, various innate or adaptive immune cells are involved in the progression of HBV or HCV infection. Among those cells, a unique kind of immune cell, the γδ T cell, contributes to promoting or inhibiting the progression of liver diseases. To reveal the diverse roles of γδ T cells in HBV or HCV infection, the properties and functions of these cells in human and mouse models are analyzed. Here, we briefly describe the characteristics and functions of γδ T cells subsets in liver diseases. Then, we fully discuss the diverse roles of γδ T cells in the progression of HBV or HCV infection, including stages of acute infection, chronic infection, liver cirrhosis, and hepatocellular carcinoma. Finally, the functions and existing problems of γδ T cells in HBV or HCV infection are summarized. A better understanding of the function of γδ T cells during the progression of HBV and HCV infection will be helpful for the treatment of virus infection.

Mucosal-Associated Invariant T Cells: Diplomatic Front-Runners in the Fight against Hepatitis B Virus Infection.

Mucosal-associated invariant T (MAIT) cells are a unique subset of innate-like T cells that bridge between innate and adaptive immunity. MAIT cells act like a 'biliary firewall' protecting the epithelial lining of the liver against pathogenic intruders. MAIT1 and MAIT17 subsets respond rapidly to pathogenic presence both in the liver as well as in the peripheral circulation. In addition to chronic hepatitis B virus (HBV) infection, MAIT cells also appear to serve as potential therapeutic targets in several other chronic ailments. Evidence indicates that MAIT cells have tissue repair functions also paving way for fibrotic changes during chronic HBV infection. Observations also suggest that HBV-hepatitis delta virus (HDV) co-infection disease progression is closely associated with loss of MAIT cells. Furthermore, reduction in the number of hepatic MAIT cells in patients with cirrhotic non-alcoholic fatty liver disease and HBV-associated primary liver cancer has also been reported. Given their concrete role against HBV disease progression, and has also become evident that the tumor microenvironment can cause functional impairment of MAIT cells. Here, we reviewed the protective and the pathological role of MAIT cells in chronic HBV infection and certain other related medical conditions based on the understanding that an optimal functioning of the MAIT cell arsenal is key to a "host-friendly" immune defense against HBV disease progression.

The Multiple Functions of B Cells in Chronic HBV Infection.

Chronic hepatitis B virus (HBV) infection is one of the main causes of liver diseases, of which the natural history and clinical outcomes are associated with the role of B cells. As humoral immune cells, B cells play a critical role in the process of anti-HBV antibody production. In addition, some studies have also characterized other B cell subsets involved in antigen presentation and regulating the immune response beyond antibody secretion. However, not all B cell subsets play a positive role in the immune response to chronic HBV infection, and various B cell subsets jointly mediate persistent HBV infection, tolerance, and liver damage. Thus, we further sought to elucidate the multiple functions of B cells to gain novel insight into the understanding of chronic hepatitis B (CHB) pathogenesis. We also reviewed the current immunotherapies targeting B cells to explore novel therapeutic interventions for the treatment of chronic HBV infection.

Evaluation of Forkhead Box P3 gene polymorphisms in chronic HBV infection.

Hepatitis B virus (HBV) infection causes liver failure, liver cirrhosis and hepatocellular carcinoma. The FOXP3 gene polymorphisms, the rs2232365 A/G and the rs3761548 A/C, were identified to be associated with regulatory T cell-mediated immunosuppression. The response to HBV infection may be affected by FOXP3 polymorphisms. The present study aimed to assess the relationship between FOXP3 gene polymorphisms and chronic HBV infection risk. FOXP3 gene polymorphisms were explored in 237 chronic HBV patients and in 237 individuals with HBV spontaneous clearance using a real-time polymerase chain reaction. The patients with rs2232365 AG and rs3761548 AC genotype had a 1.20- and a 1.58-fold greater HBV risk than non-carriers patients, although they were not significant. Moreover, the AA genotypes of both polymorphisms in the males and females had an increased the persistent HBV risk, although this also was not statistically significant. In conclusion, the present study is the first report to demonstrate that these polymorphisms have no effect on the risk of chronic HBV infection. This results suggest that FOXP3 gene polymorphisms and FOXP3 expression should be evaluated together with frequency of regulatory T cells in HBV infection.

NKG2D modulates aggravation of liver inflammation by activating NK cells in HBV infection

Hepatitis B virus (HBV) infection is thought to be an immune-mediated liver disease. The mechanisms underlying natural killer (NK) cell group 2D receptor (NKG2D) that activates NK cells and participates in anti-HBV immunity and immunopathology has not been thoroughly elucidated. Peripheral NKG2D+ and IFN-γ+ NK cells frequencies and intrahepatic NKG2D and IFN-γ mRNA and protein expressions were determined in HBV-infected patients. Levels of NKG2D and IFN-γ mRNA and protein in NK cells, co-cultured with HBV-replicating HepG2 cells with or without NKG2D blockade, were analyzed. Serum and supernatant IFN-γ, TNF-α, perforin and granzyme B were measured. In results, peripheral NKG2D+ and IFN-γ+ NK cells frequencies, intrahepatic NKG2D and IFN-γ mRNA and protein levels, and serum IFN-γ, TNF-α, perforin and granzyme B levels were all highest in HBV-related acute-on-chronic liver failure group, followed by chronic hepatitis B and chronic HBV carrier groups. In vitro, NKG2D and IFN-γ mRNA and protein levels were higher in NK cells with IFN-α stimulation than without stimulation. Supernatant IFN-γ, TNF-α, perforin and granzyme B levels were increased under co-culture or IFN-α stimulating conditions, but were partially blocked by NKG2DmAb. In conclusion, NKG2D regulates immune inflammation and anti-viral response partly through activation of NK cells during HBV infection.

Notch Signaling Contributes to Liver Inflammation by Regulation of Interleukin-22-Producing Cells in Hepatitis B Virus Infection.

The mechanism of hepatitis B virus (HBV) induced liver inflammation is not fully elucidated. Notch signaling augmented interleukin (IL)-22 secretion in CD4+ T cells, and Notch-IL-22 axis fine-tuned inflammatory response. We previously demonstrated a proinflammatory role of IL-22 in HBV infection. Thus, in this study, we analyzed the role of Notch in development of IL-22-producing cells in HBV infection by inhibition of Notch signaling using γ-secretase inhibitor DAPT in both hydrodynamic induced HBV-infected mouse model and in peripheral blood cells isolated from patients with HBV infection. mRNA expressions of Notch1 and Notch2 were significantly increased in livers and CD4+ T cells upon HBV infection. Inhibition of Notch signaling in vivo leaded to the reduction in NKp46+ innate lymphoid cells 22 (ILC22) and lymphoid tissue inducer 4 (LTi4) cells in the liver. This process was accompanied by downregulating the expressions of IL-22 and related proinflammatory cytokines and chemokines in the liver, as well as blocking the recruitment of antigen-non-specific inflammatory cells into the liver and subsequent liver injury, but did not affect HBV antigens production and IL-22 secretion in the serum. Furthermore, IL-22 production in HBV non-specific cultured CD4+ T cells, but not HBV-specific CD4+ T cells, was reduced in response to in vitro inhibition of Notch signaling. In conclusion, Notch siganling appears to be an important mediator of the liver inflammation by modulating hepatic ILC22. The potential proinflammatory effect of Notch-mediated ILC22 may be significant for the development of new therapeutic approaches for treatment of hepatitis B.

The Role of Immune Cells in Chronic HBV Infection.

Hepatitis B virus (HBV) infection is a major cause of chronic liver diseases that may progress to liver cirrhosis and hepatocellular carcinoma. Host immune responses are important factors that determine whether HBV infection is cleared or persists. After infection, viral replication occurs inside hepatocytes, and the secretion of infectious virions can take place at high rates for decades. Consequently, HBV DNA and viral proteins, like HBV early antigen (HBeAg) and HBV surface antigen (HBsAg), can be easily detected in serum. Chronic infection with HBV is the result of an ineffective antiviral immune response towards the virus. In this review, we discuss the role of immune cells in chronic HBV infection.

Editorial: Recent Advances in HBV and HCV Immunology.

Viral hepatitis is a major public health problem. While a prophylactic vaccine is now available for hepatitis B virus (HBV), an estimated 240–350 million people worldwide are persistently infected with HBV (1–3). There is not yet an approved vaccine to prevent hepatitis C virus (HCV) infection, and between 130 and 200 million people are believed to be chronically infected worldwide (4–6). Untreated, HBV and HCV can each cause liver inflammation, fibrosis, and cirrhosis, and predispose patients to liver failure and hepatocellular carcinoma (2, 5). These infections are difficult and expensive to treat. Therapy for HBV infection may be lifelong, and a true cure with loss of HBV cccDNA from the liver is rarely achieved (2). IFNα-based therapy was the only option for chronic HCV infection until recently; these regimens were often poorly tolerated and frequently ineffective. An array of direct-acting antiviral drugs has greatly improved the outlook for HCV therapy since 2011 (7), but the expense of the new drugs may limit the number of people who benefit. We still do not understand the immunologic mechanisms leading to chronic HBV and HCV infection, how the immune system controls these viruses, and how the immune system contributes to disease pathogenesis. These topics must be understood in order to develop improved therapies and, at least in the case of HCV, an effective vaccine. Our goal in this Research Topic is to cover advancements toward this understanding. The immune response in the liver – where HBV and HCV each flourish – is incompletely understood. Many of our insights into the immune responses to HBV and HCV have come from studies of human peripheral blood, with limited comparisons to the cells in the liver. The liver is believed to constitute a tolerogenic environment as it receives portal venous blood rich in microbial products from the gut (8, 9). During persistent infection with either HCV or HBV, virus-specific T cells may decrease in number. The virus-specific T cells that can be found tend to have an exhausted phenotype including expression of inhibitory co-receptors, such as PD-1, CTLA-4, or Tim3 (10). Age at the time of exposure is an important predictor of the outcome of HBV infection: those infected in the perinatal period or early in childhood are likely to experience chronic infection, while those infected as adults often mount a successful immune response, with elimination of the template cccDNA from the liver (2). Antiviral immune responses wax and wane during chronic HBV infection. In this Topic, Schuch and colleagues review the roles of CD8+ T cells and natural killer cells in HBV infection (11). Sharma and colleagues present a study of Treg cells in HBV-associated hepatocellular carcinoma (12). Rajoriya and colleagues review the roles of γδ T cells in HBV or HCV infection as well as other conditions (13). HCV causes persistent infection in an estimated 50–85% of those exposed (14). Innate and adaptive immune responses can drive spontaneous clearance of HCV infection. In this Topic, Abdel-Hakeem and Shoukry review the role of the immune response in resolution of HCV infection (15). Sung and colleagues focus on the roles played by CD8+ T cells during acute HCV (16). Genome-wide association studies have highlighted a role for IFNλ in determining the outcome of HCV infection and IFNα-based antiviral therapy; this issue is reviewed by Laidlaw and Dustin (17). Cashman and colleagues discuss the roles of humoral immunity in acute and persistent HCV infection (18). Chronic HCV infection is also associated with extrahepatic disease; Sidharthan and colleagues present gene expression study showing a role for monocytes in HCV-associated mixed cryoglobulinemic vasculitis (19). Because of shared modes of transmission, up to 30% of individuals with HIV infection may also be infected with HCV; co-infected individuals have increased inflammation and accelerated liver damage (14). Cho and colleagues present a study of T cell phenotype, activation, and function in HCV–HIV co-infected patients, highlighting distinct changes in T cell function during co-infection – even when HIV is well controlled with highly active antiretroviral therapy (20).

Expression profiles of circulating cytokines, chemokines and immune cells in patients with hepatitis B virus infection.

Background:Immune cells and molecules play a vital role in initiating, maintaining, regulating immunological homeostasis and inflammation in many pathological and physiological processes; however, the changes on expressions and functions of these cells and molecules in hepatitis B virus (HBV) infection have not been elucidated well.Objectives:The current study aimed to determine the expression pattern of different cytokines, chemokines, immune cells in HBV infection and their association with disease progression.Patients and Methods:Sixty-nine patients with chronic HBV infection were enrolled. Five immune cell subsets and 46 cytokines and chemokines were analyzed by flow cytometry and Luminex 200.Results:In comparison to healthy individuals and asymptomatic HBV carriers, expression of CXCL9, CXCL10, CXCL11, and IL-10 were elevated in patients with chronic active HBV and had positive correlation with ALT levels. In contrast, G-CSF, MCP-3, and IFN-γ levels were significantly decreased in patients with chronic active HBV infection in contrast to carriers and healthy individuals; however, these down regulations did not show any correlation with either virological findings or liver inflammation. Although the proportion of CD4+ CD25 high regulatory T cells (Tregs) was higher in patients with HBV infection than in healthy controls, no correlations were found between Tregs and other cytokines or chemokines.Conclusions:CXCR3-associated chemokines might contribute to liver inflammation in chronic hepatitis B, while MCP-3 and G-CSF were inhibited by HBV infection. Host immune response was suppressed as manifested by an increase in CD4+ CD25high Tregs and IL-10 as well as a decrease in IFN-γ. Exploiting the expression pattern of cytokine and chemokine may help to develop a better understanding of chronic HBV infection pathogenesis.

Modeling the effects of covalently closed circular DNA and dendritic cells in chronic HBV infection

The contribution of covalently closed circular DNA (cccDNA) and dendritic cells (DCs) to the progression of chronic hepatitis B virus (HBV) infection remains largely unknown. A dynamic model with seven cell types was proposed based on the biological mechanisms of viral replication and the host immune response. The cccDNA self-amplification rate was found to be closely related to both the basic reproduction number of the virus and the immune response. The combination of the cccDNA self-amplification rate and the initial activated DC count induces rich dynamics. Applying our model to the clinical data of untreated patients, we found that chronic patients have a high cccDNA self-amplification rate. For antiviral treatment, an overall drug effectiveness was introduced and the critical drug effectiveness was obtained. The model predicts that timely long-term therapy is needed to reduce the symptoms of HBV and to maintain the benefits of treatment.

Natural Killer Cells Are Characterized by the Concomitantly Increased Interferon-γ and Cytotoxicity in Acute Resolved Hepatitis B Patients

Natural killer (NK) cells are abundant in the liver and have been implicated in inducing hepatocellular damage in patients with chronic hepatitis B virus (HBV) infection. However, the role of NK cells in acute HBV infection remains to be elucidated. We comprehensively characterized NK cells and investigated their roles in HBV clearance and liver pathology in 19 chronic hepatitis B (CHB) patients and 21 acute hepatitis B (AHB) patients as well as 16 healthy subjects. It was found that NKp46+ NK cells were enriched in the livers of AHB and CHB patients. We further found that peripheral NK cells from AHB patients expressed higher levels of activation receptors and lower levels of inhibitory receptors than those from CHB patients and HC subjects, thus displaying the increased cytolytic activity and interferon-γ production. NK cell activation levels were also correlated positively with serum alanine aminotransferase levels and negatively with plasma HBV DNA levels in AHB patients, which is further confirmed by the longitudinal follow-up of AHB patients. Serum pro-inflammatory cytokine and chemokine levels were also increased in AHB patients as compared with CHB and HC subjects. Thus, the concomitantly increased interferon-γ and cytotoxicity of NK cells were associated with liver injury and viral clearance in AHB patients.

Hepatitis B Virus Infection triggers AP–1 dependent CD95Ligand expression in HepG2 cells

An acute Hepatitis B Virus (HBV)-infection is characterized by a vigorous, polyclonal and multi-specific CD8+ T cell response. CD8+ T cells are the main effector cells responsible for viral clearance and disease pathogenesis during an acute HBV-infection. CD95 Ligand (CD95L) expression is generally restricted to a few cell types, e.g. T cells, macrophages and NK cells. We have previously shown that an intact CD95 signalling pathway is required for elimination of HBV-infected hepatocytes. Furthermore, we have identified an AP–1 element in the CD95L promoter which is essential for the transactivation of the CD95L gene. The aim of this study was to analyze CD95L transactivation and -expression in HBV-infected hepatocytes. Adenoviral transfer of HBV constructs into the hepatoma cell line HepG2 resulted in the transactivation, transcription and expression of CD95L. Four different CD95L promoter constructs (CD95L –36, –220, –536, and –1204/+100) have been used to identify the binding site responsible for CD95L transactivation in HBV-infected hepatocytes. However, there was no particular difference in the induction of the different constructs. This led to the hypothesis that no binding site between –36 and –1204 functions as the major binding site responsible for CD95L transactivation in HBV-infected hepatocytes. Instead, inhibition of JNK resulted in a significant inhibition of CD95L transactivation. Since HBV infection resulted in the phosphorylation of JNK (Jun-NH2 kinase) and the subsequent activation of the transcription factor AP–1, we postulate that CD95L transactivation is triggered by Thr183/Tyr185 phosphorylation of JNK. We characterized the molecular mechanisms resulting in CD95L expression in HBV-infected hepatocytes. In this study we provide evidence that HBV infection leads to the phosphorylation of JNK, AP–1 dependent transactivation of CD95L and finally CD95L expression, suggesting a potential CD95L activation independent of CD8+ T cells in HBV infection.

Hierarchy of inhibitory receptor expression by Hepatitis B Virus (HBV)-specific CD8+ T cells in chronic HBV infection

Virus-specific CD8+ T cells are thought to play a crucial role in the immunobiology of HBV infection. In chronic HBV infection, up-regulation of several inhibitory signaling pathways by HBV-specific CD8+ T cells is thought to contribute to viral persistence. However, the relative contribution of the individual inhibitory pathways has not been addressed so far. In this study, we determined the coexpression of multiple inhibitory receptors (PD–1, 2B4, CD160, KLRG1 and Tim–3) ex vivo by HBV-specific CD8+ T cells from 17 patients (16 HBeAg neg., 1 HBeAg pos.) with significant HBV-specific T cell frequencies and compared it to CD8+ T cells specific for other viruses (FLU, CMV, HCV). The differentiation stage of virus-specific CD8+ T cells was analyzed by CCR7, CD27 and CD45RA expression. We found that the coexpression of inhibitory receptors was associated with intermediate T cell differentiation stages. Further, HBV-specific CD8+ T cells expressed higher amounts of PD–1 and 2B4 compared to CD160, KLRG1 and Tim–3. PD–1+2B4+ HBV-specific CD8+ T cells were enriched intrahepatically compared to the peripheral blood. The expression pattern of inhibitory receptors clearly differed between HBV-specific (high PD–1 and 2B4 expression) and Influenza- (high Tim–3 expression) or CMV-specific CD8+ T cells (high 2B4 and KLRG1 expression) but showed a similarly high expression of PD–1 and 2B4 with HCV-specific CD8+ T cells, suggesting a common hierarchy of inhibitory receptor expression between CD8+ T cells specific for hepatitis B and C viruses. These results suggest a hierarchy of inhibitory receptor expression by HBV-specific CD8+ T cells dominated by PD–1 and 2B4. They also suggest a rationale for the therapeutic targeting of these inhibitory receptor pathways in chronic HBV infection.

Frequencies of epitope-specific cytotoxic T lymphocytes in active chronic viral hepatitis B infection by using MHC class I peptide tetramers

Hepatitis B virus (HBV)-specific cytotoxic T lymphocytes (CTLs) are thought to play key roles in viral control and liver damage. We have used HLA-A ∗02 tetramer complex to human HBV core 18–27 (Tc 18–27), envelope 183–191 (Te 183–191), envelope 335–343 (Te 335–343), and polymerase 575–583 (Tp 575–583) epitopes to characterize HLA class I-restricted CD8+ T cells in active chronic HBV infection. The frequencies of specific epitopes circulating tetramer+ cells were determined in whole-blood samples by analysis of flow cytometry. The correlation of HBV epitope-specific CTL, between viral replication and liver damage, was analyzed by multiple regression. Our data shown that HBV-specific CD8+ T cells can be easily detected in peripheral blood of active chronic HBV infections. No significant correlation was found between either the frequency of HBV-specific CD8+ T cells and the viral load, or the frequency of HBV-specific CD8+ T cells and the levels of alanine transaminase. These results suggest that the existence of epitope-specific HBV CTLs are not directly correlated to hepatocyte injury, and the frequencies of HBV-specific T cells are not determinant of immune-mediated protection in chronic HBV infection.

HBV viral load within subpopulations of peripheral blood mononuclear cells in HBV infection using limiting dilution PCR

Extrahepatic viral load in peripheral blood mononuclear cells (PBMCs) of patients with hepatitis B virus (HBV) is still under debate. In this study, HBV infection rates and viral titers were examined within all PBMC subpopulations using limiting dilution-PCR (LD-PCR). PBMCs of patients with acute or chronic hepatitis B were separated by magnetic beads in monocytes, B-cells, CD4+ T-cells, CD8+ T-cells, and NK cells. Using two-round nested PCR, HBV-DNA sequences were detected in all patients examined within each PBMC subpopulation. The frequencies of HBV-positive cells and viral loads were calculated by Poisson analysis of HBV PCR results from serial dilutions of cells and cell lysates. Highest infection rates were found in monocytes and B-cells followed by CD8+ T-cells, NK cells, and CD4+ T-cells. Concerning all subsets, frequencies of HBV-positive cells were 50- to 500-fold higher in chronic than in acute hepatitis B. Viral loads were mostly estimated at about one HBV genome per HBV-positive cell. Moreover, slightly elevated HBV titers were seen in B-cells, CD4+ T-cells, and NK cells in both acute and chronic hepatitis B. It was demonstrated that beside a generally more latent HBV infection in PBMCs, elevated HBV titers point to replication or selective viral uptake within particular PBMC subsets. Therefore, the data suggest that HBV-infected PBMCs may participate in persistence of HBV.

Hepatitis B virus (HBV)-transgenic mice as an investigative tool to study immunopathology during HBV infection.

An overview is given regarding the use of hepatitis B virus (HBV) transgenic mice as an animal model of the HBV-carrier state. Initially, we show how HBV-transgenic mice have contributed insights into the immunopathobiological processes during HBV infection and later, we show how this new information from the experiments with HBV-transgenic mice could be used to develop new methods to combat HBV infection. By microinjecting the full or selected parts of the HBV-genome into the fertilized eggs of inbred mice, different laboratories have developed different lines of HBV-transgenic mice, which express products of the HBV genome and also show signs of HBV replication. Studies in HBV-transgenic mice have provided insights into the process of destruction of hepatocytes, the critical role of cytokines in controlling HBV replication and gene expression, mechanisms underlying the immune response defect in chronic HBV-carriers and the critical role of antigen presenting cells (APC), especially that of antigen presenting dendritic cells in persistent HBV infection. All this new information has given us a better understanding about HBV immunopathobiology, and has led to the development of new therapeutic approaches to combat HBV infection.