FOXP3 expression in hepatitis C virus-specific CD4+ T cells during acute hepatitis C

Adaptive Immune Response against Hepatitis C Virus

A functional adaptive immune response is the major determinant for clearance of hepatitis C virus (HCV) infection. However, in the majority of patients, this response fails and persistent infection evolves. Here, we dissect the HCV-specific key players of adaptive immunity, namely B cells and T cells, and describe factors that affect infection outcome. Once chronic infection is established, continuous exposure to HCV antigens affects functionality, phenotype, transcriptional program, metabolism, and the epigenetics of the adaptive immune cells. In addition, viral escape mutations contribute to the failure of adaptive antiviral immunity. Direct-acting antivirals (DAA) can mediate HCV clearance in almost all patients with chronic HCV infection, however, defects in adaptive immune cell populations remain, only limited functional memory is obtained and reinfection of cured individuals is possible. Thus, to avoid potential reinfection and achieve global elimination of HCV infections, a prophylactic vaccine is needed. Recent vaccine trials could induce HCV-specific immunity but failed to protect from persistent infection. Thus, lessons from natural protection from persistent infection, DAA-mediated cure, and non-protective vaccination trials might lead the way to successful vaccination strategies in the future.

Regulatory T Cell and Forkhead Box Protein 3 as Modulators of Immune Homeostasis

The transcription factor forkhead box protein 3 (FOXP3) is an essential molecular marker of regulatory T cell (Treg) development in different microenvironments. Tregs are cells specialized in the suppression of inadequate immune responses and the maintenance of homeostatic tolerance. Studies have addressed and elucidated the role played by FOXP3 and Treg in countless autoimmune and infectious diseases as well as in more specific cases, such as cancer. Within this context, the present article reviews aspects of the immunoregulatory profile of FOXP3 and Treg in the management of immune homeostasis, including issues relating to pathology as well as immune tolerance.

Indoleamine 2,3-dioxygenase: As a potential prognostic marker and immunotherapeutic target for hepatocellular carcinoma

Tumor cells induce an immunosuppressive microenvironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase (IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma (HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immunosuppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.

Hepatitis C-specific effector and regulatory CD4 T-cell responses are associated with the outcomes of primary infection

Clearance of primary hepatitis C virus (HCV) infection has been associated with strong and broadly targeted cellular immune responses. This study aimed to characterize HCV-specific CD4+ effector and regulatory T-cell numbers and cytokine production during primary infection. Antigen-specific CD4+ T-cell responses were investigated in a longitudinal cohort of subjects from pre-infection to postoutcome, including subjects who cleared [n=12] or became chronically infected [n=17]. A cross-sectional cohort with previously cleared, or chronic infection [n=15 for each], was also studied. Peripheral blood mononuclear cells were incubated with HCV antigens and surface stained for T-effector (CD4+CD25^high CD134+CD39-) and T-regulatory (CD4+CD25^high CD134+CD39+) markers, and culture supernatants assayed for cytokine production. Contrary to expectations, the breadth and magnitude of the HCV-specific CD4+ T-cell responses were higher in subjects who became chronically infected. Subjects who cleared the virus had HCV-specific CD4+ T-cell responses dominated by effector T cells and produced higher levels of IFN-γ, in contrast to HCV-specific CD4+ T-cell responses dominated by regulatory T cells and more IL-10 production in those who became chronically infected. Better understanding of the role of antigen-specific CD4+ T-cell responses in primary HCV will further define pathogenesis and help guide development of a preventative vaccine.

Immune responses and immunopathology in acute and chronic viral hepatitis

Hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV) are responsible for most cases of viral hepatitis. Infection by each type of virus results in a different typical natural disease course and clinical outcome that are determined by virological and immunological factors. HCV tends to establish a chronic persistent infection, whereas HAV does not. HBV is effectively controlled in adults, although it persists for a lifetime after neonatal infection. In this Review, we discuss the similarities and differences in immune responses to and immunopathogenesis of HAV, HBV and HCV infections, which may explain the distinct courses and outcomes of each hepatitis virus infection.

Role of regulatory T-cells during hepatitis C infection: From the acute phase to post-transplantation recurrence

Hepatitis C viral infection persists and becomes chronic in a majority of affected individuals. Numerous factors have been described to explain how the virus manages to escape the host immune system. One important escape mechanism is the increase in regulatory T cells induced by the virus. In this review, we will focus on the status of regulatory T cells throughout the natural history of hepatitis C infection and after liver transplantation. The molecular mechanisms involved in increasing the number of regulatory T cells are also discussed, as are data regarding the impact of regulatory T-cells on hepatic fibrosis in the context of hepatitis C viral infection.

Therapeutic DNA vaccination using in vivo electroporation followed by standard of care therapy in patients with genotype 1 chronic hepatitis C

Clearance of infections caused by the hepatitis C virus (HCV) correlates with HCV-specific T cell function. We therefore evaluated therapeutic vaccination in 12 patients with chronic HCV infection. Eight patients also underwent a subsequent standard-of-care (SOC) therapy with pegylated interferon (IFN) and ribavirin. The phase I/IIa clinical trial was performed in treatment naive HCV genotype 1 patients, receiving four monthly vaccinations in the deltoid muscles with 167, 500, or 1,500 μg codon-optimized HCV nonstructural (NS) 3/4A-expressing DNA vaccine delivered by in vivo electroporation (EP). Enrollment was done with 2 weeks interval between patients for safety reasons. Treatment was safe and well tolerated. The vaccinations significantly improved IFN-γ-producing responses to HCV NS3 during the first 6 weeks of therapy. Five patients experienced 2-10 weeks 0.6-2.4 log10 reduction in serum HCV RNA. Six out of eight patients starting SOC therapy within 1-30 months after the last vaccine dose were cured. This first-in-man therapeutic HCV DNA vaccine study with the vaccine delivered by in vivo EP shows transient effects in patients with chronic HCV genotype 1 infection. The interesting result noted after SOC therapy suggests that therapeutic vaccination can be explored in a combination with SOC treatment.

Intrahepatic IL-8 producing Foxp3⁺CD4⁺ regulatory T cells and fibrogenesis in chronic hepatitis C

BACKGROUND & AIMS

Regulatory CD4(+) T cells (Tregs) are considered to affect outcomes of HCV infection, because they increase in number during chronic hepatitis C and can suppress T-cell functions.

METHODS

Using microarray analysis, in situ immunofluorescence, ELISA, and flowcytometry, we characterised functional differentiation and localisation of adaptive Tregs in patients with chronic hepatitis C.

RESULTS

We found substantial upregulation of IL-8 in Foxp3(+)CD4(+) Tregs from chronic hepatitis C. Activated GARP-positive IL-8(+) Tregs were particularly enriched in livers of patients with chronic hepatitis C in close proximity to areas of fibrosis and their numbers were correlated with the stage of fibrosis. Moreover, Tregs induced upregulation of profibrogenic markers TIMP1, MMP2, TGF-beta1, alpha-SMA, collagen, and CCL2 in primary human hepatic stellate cells (HSC). HSC activation, but not Treg suppressor function, was blocked by adding a neutralizing IL-8 antibody.

CONCLUSIONS

Our studies identified Foxp3(+)CD4(+) Tregs as an additional intrahepatic source of IL-8 in chronic hepatitis C acting on HSC. Thus, Foxp3(+)CD4(+) Tregs in chronic hepatitis C have acquired differentiation as regulators of fibrogenesis in addition to suppressing local immune responses.

CD4+ T-cell engagement by both wild-type and variant HCV peptides modulates the conversion of viral clearing helper T cells to Tregs

AIM

To determine whether modulation of T-cell responses by naturally occurring viral variants caused an increase in numbers of Tregs in HCV-infected patients.

PATIENTS MATERIALS & METHODS

Human peripheral blood mononuclear cells, having proliferative responses to a wild-type HCV-specific CD4⁺ T-cell epitope, were used to quantify, via proliferative assays, flow cytometry and class II tetramers, the effects of naturally occurring viral variants arising in the immunodominant epitope.

RESULTS

In combination, the wild-type and variant peptides led to enhanced suppression of an anti-HCV T-cell response. The variant had a lower avidity for the wild-type-specific CD4⁺ T cell. Variant-stimulated CD4⁺ T cells had increased Foxp3, compared with wild-type-stimulated cells.

CONCLUSION

A stable viral variant from a chronic HCV subject was able to induce Tregs in multiple individuals that responded to the wild-type HCV-specific CD4⁺ T-cell epitope.

Divergent contributions of regulatory T cells to the pathogenesis of chronic hepatitis C

Hepatitis C virus, a small single-stranded RNA virus, is a major cause of chronic liver disease. Resolution of primary hepatitis C virus infections depends upon the vigorous responses of CD4(+) and CD8(+) T cells to multiple viral epitopes. Although such broad CD4(+) and CD8(+) T-cell responses are readily detected early during the course of infection regardless of clinical outcome, they are not maintained in individuals who develop chronic disease. Purportedly, a variety of factors contribute to the diminished T-cell responses observed in chronic, virus-infected patients including the induction of and biological suppression by CD4(+)FoxP3(+) regulatory T cells. Indeed, a wealth of evidence suggests that regulatory T cells play diverse roles in the pathogenesis of chronic hepatitis C, impairing the effector T-cell response and viral clearance early during the course of infection and suppressing liver injury as the disease progresses. The factors that affect the generation and biological response of regulatory T cells in chronic, hepatitis C virus-infected patients is discussed.

Dendritic cells, regulatory T cells and the pathogenesis of chronic hepatitis C

Hepatitis C virus (HCV) is a small, enveloped RNA virus and a major cause of chronic liver disease. Resolution of primary HCV infections depends upon the vigorous responses of CD4⁺ and CD8⁺ T cells to multiple viral epitopes. Although such broad-based responses are readily detected early during the course of infection regardless of clinical outcome, they are not maintained in individuals who develop chronic disease. Ostensibly, a variety of factors contribute to the diminished T cell responses observed in chronic, HCV-infected patients including impaired dendritic cell function and the induction of CD4⁺FoxP3⁺ regulatory T cells. Overwhelming evidence suggests that the complex interaction of dendritic cells and regulatory T cells plays a critical role in the pathogenesis of chronic hepatitis C.

Reversal of nonstructural protein 3-specific CD4(+) T cell dysfunction in patients with persistent hepatitis C virus infection

Hepatitis C virus (HCV)-specific T cell responses are essential for HCV control, and chronic infection is characterized by functionally altered antigen-specific T cells. It has been proposed that the early inactivation of specific CD4(+) T cell responses may be involved in establishment of HCV persistence. We have investigated whether HCV-specific CD4(+) T cells dysfunction can be reversed in vitro. Nonstructural protein 3 (NS3) and core-specific CD4(+) T cells from eight chronically infected and eight spontaneously resolved HCV individuals were selected through transient CD154 (CD40 ligand) expression, and their functional profile (IFN-γ, IL-2, TNF-α, IL-10 and IL-4 production by enzyme-linked immunospot assay, cytometric bead array and intracellular cytokine staining, and proliferation by carboxy-fluorescein diacetate succinimidyl ester dilution assay) was determined both ex vivo and after in vitro expansion of sorted CD154-expressing cells in the absence of specific antigen in IL-7/IL-15-supplemented medium. Ex vivo bulk CD4(+) T cells from chronic patients expressed CD154 in most cases, albeit at lower frequencies than those of resolved patients (0.11%vs 0.41%; P = 0.01), when stimulated with NS3, but not core, although they had a markedly impaired capacity to produce IL-2 and IFN-γ. Antigen-free in vitro expansion of NS3-specific CD154(+) cells from chronic patients restored IFN-γ and IL-2 production and proliferation to levels similar to those of patients with spontaneously resolved infection. Hence, NS3-specific CD4(+) T cell response can be rescued in most chronic HCV patients by in vitro expansion in the absence of HCV-specific antigen. These results might provide a rationale for adoptive immunotherapy.

The ambiguity in immunology

In the present article, we discuss the various ambiguous aspects of the immune system that render this complex biological network so highly flexible and able to defend the host from different external invaders. This ambiguity stems mainly from the property of the immune system to be both protective and harmful. Immunity cannot be fully protective without producing a certain degree of damage (immunopathology) to the host. The balance between protection and tissue damage is, therefore, critical for the establishment of immune homeostasis and protection. In this review, we will consider as ambiguous, various immunological tactics including: (a) the opposing functions driving immune responses, immune-regulation, and contra-regulation, as well as (b) the phenomenon of chronic immune activation as a result of a continuous cross-presentation of apoptotic T cells by dendritic cells. All these plans participate principally to maintain a state of chronic low-level inflammation during persisting infections, and ultimately to favor the species survival.

Different aspects of CD4 T cells that lead to viral clearance or persistence of HCV infection

More than 170 million people worldwide are infected with hepatitis C virus (HCV). A characteristic of this virus is a high tendency toward chronic infection. Several factors affect the viral outcome after infection. Among them, HCV-specific CD4 T cells are thought to play a crucial role in controlling viremia. Cumulative data showed that spontaneously resolved individuals have vigorous CD4 T-cell responses to a broad spectrum of HCV antigens and maintain these responses over a long period of time, whereas chronically infected patients lose their CD4 T-cell responses in the acute phase of infection. Although several possibilities of why CD4 T cells lose their function have been proposed, the mechanisms are not completely understood. Moreover, there is another subset of CD4 T cells called regulatory T cells (Tregs). These cells suppress immune reaction of T cells, B cells, and antigen-presenting cells, and are thought to protect organs from immune overreaction and autoimmunity. An increasing amount of data supports the possibility that Tregs participate in the mechanism of HCV persistence. It is obvious that CD4 T cells are the main effectors controlling HCV outcome. To achieve a better prognosis, we need to understand the mechanism of how HCV earns its chronicity by escaping from host cellular immune attacks. In this review, we will focus on the role of HCV-specific T cells in controlling viremia, particularly the aspects of these cells being either inhibitors or propellers of chronic infection.

Inhibitory molecules that regulate expansion and restoration of HCV-specific CD4+ T cells in patients with chronic infection

BACKGROUND & AIMS

Inhibitory receptors such as programmed death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen (CTLA)-4 mediate CD8+ T-cell exhaustion during chronic viral infection, but little is known about roles in dysfunction of CD4+ T cells.

METHODS

We investigated the functions of inhibitory molecules on hepatitis C virus (HCV)-, influenza-, and Epstein-Barr virus (EBV)-specific CD4+ T cells in patients with chronic infections compared with patients with resolved HCV infection and healthy donors. Expression of PD-1, CTLA-4, CD305, and CD200R were analyzed on HCV-specific CD4+ T cells, isolated from peripheral blood using major histocompatibility complex class II tetramers. We investigated the effects of in vitro inhibition of various inhibitory pathways on proliferation and cytokine production by CD4+ T cells, and we compared these effects with those from inhibition of interleukin (IL)-10 and transforming growth factor (TGF)-β1.

RESULTS

PD-1 and CTLA-4 were up-regulated on virus-specific CD4+ T cells from patients with chronic HCV infections. PD-1 expression was lower on influenza- than on HCV-specific CD4+ T cells from subjects with chronic HCV infection, whereas CTLA-4 was expressed at similar levels, independent of their specificity. CD305 and CD200R were up-regulated in HCV resolvers. Blockade of PD-L1/2, IL-10, and TGF-β1 increased expansion of CD4+ T cells in patients with chronic HCV, whereas inhibition of IL-10 and TGF-β1 was most effective in restoring HCV-specific production of interferon gamma, IL-2, and tumor necrosis factor α.

CONCLUSIONS

We characterized expression of inhibitory molecules on HCV-, influenza-, and EBV-specific CD4+ T cells and the effects of in vitro blockade on CD4+ T-cell expansion and cytokine production. Inhibition of PD-1, IL-10, and TGF-β1 is most efficient in restoration of HCV-specific CD4+ T cells.

Redistribution of regulatory T-cells across the evolving stages of chronic hepatitis C

BACKGROUND

Hepatitis C virus infection frequently leads to chronic hepatitis, possibly evolving to end-stage liver disease and hepatocellular carcinoma. Regulatory T cells can affect antiviral immune response thus influencing the outcome of the disease.

AIM

To determine numeric and functional distribution of regulatory T cells expressing CD4+CD25hiFoxp3+ (T-regs) during the different stages of hepatitis C virus-related liver disease.

METHODS

90 hepatitis C viraemic patients and 50 healthy controls were included. Surface and intracellular (Foxp3) T-reg markers were evaluated by flow cytometry. Target cell proliferation and interferon-gamma production were evaluated in 37 HCV patients. In 16 cases intrahepatic distribution of Foxp3 by immuno-histochemistry was assessed.

RESULTS

T-regs were increased in hepatitis C virus infected patients and correlated inversely with aminotransferases and directly with MELD score and disease duration. A preserved inhibitory ability of interferon-gamma production was distinctive of patients with normal aminotransferases. Circulating T-regs did not correlate with intrahepatic distribution of Foxp3.

CONCLUSIONS

In chronic hepatitis C, selective expansion of peripheral T-regs in patients with normal aminotransferases and advanced disease suggests that, though a continual low level inflammation does not prevent liver disease progression, once cirrhosis has developed it may represent an attempt to prevent immuno-mediated decompensation.

A humanized mouse model to study hepatitis C virus infection, immune response, and liver disease

BACKGROUND & AIMS

Studies of hepatitis C virus (HCV) infection, immunopathogenesis, and resulting liver diseases have been hampered by the lack of a small animal model. We developed humanized mice with human immune system and liver tissues to improve the studies of hepatitis C virus pathogenesis and treatment.

METHODS

To promote engraftment of human hepatocytes, we expressed a fusion protein of the FK506 binding protein (FKBP) and caspase 8 under control of the albumin promoter (AFC8), which induces liver cell death, in Balb/C Rag2(-/-) γC-null mice. Cotransplantation of human CD34(+) human hematopoietic stem cells (HSC) and hepatocyte progenitors into the transgenic mice led to efficient engraftment of human leukocytes and hepatocytes. We then infected these humanized mice (AFC8-hu HSC/Hep) with primary HCV isolates and studied HCV-induced immune responses and liver diseases.

RESULTS

AFC8-hu HSC/Hep mice supported HCV infection in the liver and generated a human immune T-cell response against HCV. HCV infection induced liver inflammation, hepatitis, and fibrosis, which correlated with activation of stellate cells and expression of human fibrogenic genes.

CONCLUSIONS

AFC8-hu HSC/Hep mice are a useful model of HCV infection, the immune response, and liver disease because they contain human immune system and liver cells. These mice become infected with HCV, generate a specific immune response against the virus, and develop liver diseases that include hepatitis and fibrosis. This model might also be used to develop therapeutics for HCV infection.

Adaptive immunity to the hepatitis C virus

The hepatitis C virus (HCV) is a global public health problem affecting approximately 2% of the human population. The majority of HCV infections (more than 70%) result in life-long persistence of the virus that substantially increases the risk of serious liver diseases, including cirrhosis and hepatocellular carcinoma. The remainder (less than 30%) resolves spontaneously, often resulting in long-lived protection from persistence upon reexposure to the virus. To persist, the virus must replicate and this requires effective evasion of adaptive immune responses. In this review, the role of humoral and cellular immunity in preventing HCV persistence, and the mechanisms used by the virus to subvert protective host responses, are considered.

Hepatitis C virus induces regulatory T cells by naturally occurring viral variants to suppress T cell responses

Regulatory T cell markers are increased in chronically infected individuals with the hepatitis C virus (HCV), but to date, the induction and maintenance of Tregs in HCV infection has not been clearly defined. In this paper, we demonstrate that naturally occurring viral variants suppress T cell responses to cognate NS3_358-375 in an antigen-specific manner. Of four archetypal variants, S370P induced regulatory T cell markers in comparison to NS3_358-375-stimulated CD4 T cells. Further, the addition of variant-specific CD4 T cells back into a polyclonal culture in a dose-dependent manner inhibited the T cell response. These results suggest that HCV is able to induce antigen-specific regulatory T cells to suppress the antiviral T cell response in an antigen-specific manner, thus contributing to a niche within the host that could be conducive to HCV persistence.

Hepatitis C virus infection: a "liaison a trois" amongst the virus, the host, and chronic low-level inflammation for human survival

This review covers the various aspects of the immune system that allows the relationship between the hepatitis-C virus, the host and chronic low-level inflammation, to be highly flexible and able to defend the host from persistent infections. This ambiguity mainly stems from the property of the immune system that can be both protective and harmful. Immunity cannot be fully protective without producing a certain degree of damage (acute hepatitis resulting in resolving HCV infection). In addition, the balance between protection and tissue damage is critical for the development of chronic HCV infection. The establishment of a state of chronic low-level inflammation is instrumental to limit liver immunopathology, to limit viral spread, and ultimately to ensure a long-lasting survival of the host. It is dictated by a fine equilibrium maintained by multiple immunologic mechanisms, including: sensory perception of innate immunity, virus-specific T and B cell functions, control of immune responses, and finally the balance between immunity and immunopathology that has principally evolved to favor the survival of the species.

Core-specific adaptive regulatory T-cells in different outcomes of hepatitis C

CD4+ Treg-cells (regulatory T-cells) probably contribute to the impaired virus-specific T-cell responses in chronic HCV (hepatitis C virus) infection; however, their antigen-specificity has remained elusive. In the present study, we analysed peripheral blood CD4+ Treg-cells in patients with chronic hepatitis C and subjects with self-limited HCV infection and characterized individual Treg-cell clones obtained from both groups at the phenotypic and functional level. Foxp3 (forkhead box p3)+CD25+CD4+ Treg-cells were detected more frequently in patients with chronic hepatitis C than self-limited HCV infection, which responded to HCV core stimulation and inhibited proliferation of reporter cells. Cloning under limiting dilution conditions resulted in 14 and six hypoproliferative Foxp3+CD25+CD127-CD4+ T-cell clones from patients with chronic hepatitis C and subjects with self-limited HCV infection respectively. All clones expressed Treg-cell markers and produced IL (interleukin)-10 upon mitogen stimulation. However, exclusively Treg-cell clones from chronic hepatitis C produced IL-10 in response to HCV core and inhibited proliferation of reporter T-cells. These core-specific Treg-cell clones recognized epitopes in two regions of HCV core (amino acids 1-44 and 79-113). Co-culture inhibition assays demonstrated Treg-cells to inhibit reporter T-cells via secretion of IL-10 and IL-35 rather than cell-contact-dependent mechanisms. Finally, the HCV-specific Treg-cell clones lost their functional capacity, along with Foxp3 expression, if kept in culture without HCV core exposure. In conclusion, we identified functionally active HCV core-specific Treg-cells in patients with chronic hepatitis C, which share their epitopes with conventional T-cells and require the continued presence of antigen to maintain their functional differentiation. Thus HCV core-specific Treg-cells may contribute to the immunoregulatory balance in chronic hepatitis C.

Analysis of FOXP3+ regulatory T cells that display apparent viral antigen specificity during chronic hepatitis C virus infection

We reported previously that a proportion of natural CD25(+) cells isolated from the PBMC of HCV patients can further upregulate CD25 expression in response to HCV peptide stimulation in vitro, and proposed that virus-specific regulatory T cells (Treg) were primed and expanded during the disease. Here we describe epigenetic analysis of the FOXP3 locus in HCV-responsive natural CD25(+) cells and show that these cells are not activated conventional T cells expressing FOXP3, but hard-wired Treg with a stable FOXP3 phenotype and function. Of approximately 46,000 genes analyzed in genome wide transcription profiling, about 1% were differentially expressed between HCV-responsive Treg, HCV-non-responsive natural CD25(+) cells and conventional T cells. Expression profiles, including cell death, activation, proliferation and transcriptional regulation, suggest a survival advantage of HCV-responsive Treg over the other cell populations. Since no Treg-specific activation marker is known, we tested 97 NS3-derived peptides for their ability to elicit CD25 response (assuming it is a surrogate marker), accompanied by high resolution HLA typing of the patients. Some reactive peptides overlapped with previously described effector T cell epitopes. Our data offers new insights into HCV immune evasion and tolerance, and highlights the non-self specific nature of Treg during infection.

Overexpression of Toll-like receptor 2/4 on monocytes modulates the activities of CD4(+)CD25(+) regulatory T cells in chronic hepatitis B virus infection

The significance of TLR expression and Tregs in HBV infection has not been clearly described. In this report, flow cytometry was performed to assess TLR2/4 expression on monocytes and circulating CD4(+)CD25(+)CD127(low/-) Tregs frequency of 16 acute hepatitis B (AHB), 42 chronic hepatitis B (CHB), 22 asymptomatic HBV carriers (AsC), and 20 normal controls (NC). We found that TLR2 and TLR4 were overexpressed on CD14(+) monocytes in HBV-infected patients as compared with NCs. Upregulation of TLR2 in NCs and TLR4 in CHBs was observed following HBeAg incubation. However, TLR2 and TLR4 expression decreased after HBcAg stimulation. The difference in the proportion of Tregs between NCs and CHBs was significant. Both Pam3Csk4 (TLR2 agonist)- and lipopolysaccharide (TLR4 agonist)-activated CD4(+)CD25(+) Tregs showed enhanced suppression function in CHBs. These results suggest that overexpression of TLR2 and TLR4 may modulate the suppressive function of Tregs, which contribute to the immunotolerance of chronic HBV infection.