Elevated CD4+/CD25+ T-cell frequency and function during hepatitis C virus recurrence after liver transplantation

IFN-α-based treatment of patients with chronic HCV show increased levels of cells with myeloid-derived suppressor cell phenotype and of IDO and NOS

INTRODUCTION

Hepatitis C virus (HCV) infection causes chronic hepatitis, which is often associated with suppressed anti-HCV immune responses. We have recently reported accumulation of myeloid-derived suppressor cells (MDSCs) and suppressed immunity in cancer patients.

AIM

The main aim of this study was to determine whether chronic HCV patients harbor high of MDSCs in general and in nonresponders to IFN-based therapy in particular as well as to analyze the immune suppressive molecules.

METHODS

Peripheral blood samples withdrawn from 154 patients with chronic HCV infection and were categorized into responders and nonresponders based on viral titer upon IFN-α treatment.

RESULTS

The relative and absolute numbers of MDSCs defined as Lin^-/HLA-DR^-/CD33⁺/CD11b⁺ increased in all HCV patients, where they were higher in nonresponders than in responders. Additionally, the levels of MDSCs after 4-6 months of treatment in responders were lower than during the course of treatment. The responders also showed higher levels of IL-2 coincided with increased numbers of dendritic cells (DCs), CD4⁺ and CD8⁺ T cells. The levels of total NOS and IDO were also higher in nonresponders as compared to responders and healthy controls, while the expression levels of CD3ζ was lower in responders as compared to nonresponders and healthy volunteers.

CONCLUSION

Chronic HCV patients harbor high numbers of MDSCs, which are higher in nonresponders than in responders. The higher numbers of MDSCs associated with increases in the suppressing factors.

Significance of CD4+CD25+CD127low/- regulatory T cells in hepatitis C

AIM: To investigate the diagnostic and therapeutic significance of CD4⁺CD25⁺CD127^low/- regulatory T (Treg) cell ratio in peripheral blood of patients with chronic hepatitis C.

METHODS: Ninety-six chronic hepatitis C patients undergoing polyethylene glycol interferon (PEG-IFN) and ribavirin (RBV) therapy at Yucheng People's Hospital were assigned to an observation group, and 65 healthy volunteers were included in a control group. CD4⁺CD25⁺CD127^low/-Treg ratio was detected at baseline and 24 wk after treatment. The changes of CD4⁺CD25⁺CD127^low/- Treg ratio with different viral levels and liver injury were analyzed. According to whether the patients achieved a virologic response in 24 wk after withdrawal, they were divided into a sustained virologic response (SVR) group or a non-SVR group. The differences between the two groups in CD4⁺CD25⁺CD127^low/-Treg ratios were analyzed at baseline and 24 wk after treatment.

RESULTS: The proportion of CD4⁺CD25⁺CD127^low/- Treg cells at baseline in the observation group was significantly higher than that at baseline in the control group and that at the end of treatment in the observation group (P < 0.05). CD4⁺CD25⁺CD127^low/- Treg cell ratios of patients with different load of HCV RNA were different. With the increase in HCV RNA load, CD4⁺CD25⁺CD127^low/- Treg cell proportion continued to rise significantly (P < 0.05). At 24 wk after withdrawal, the rate of SVR in the observation group was 78.3%. The proportion of CD4⁺CD25⁺CD127^low/- Treg cells in SVR patients was significantly lower than that of patients without SVR (P < 0.05) no matter whether at baseline or at 24 wk after treatment. Correlation analysis showed that the baseline CD4⁺CD25⁺CD127^low/- Treg cell proportion was positively correlated with the liver function index AST/ALT (P < 0.05).

CONCLUSION: CD4⁺CD25⁺CD127^low/- Treg cells may be involved in the pathogenesis of chronic hepatitis, and clinical detection of CD4⁺CD25⁺CD127^low/- Treg cell ratio may be helpful for disease diagnosis and prognosis evaluation.

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.

Distinct dictation of Japanese encephalitis virus-induced neuroinflammation and lethality via triggering TLR3 and TLR4 signal pathways

Japanese encephalitis (JE) is major emerging neurologic disease caused by JE virus. To date, the impact of TLR molecules on JE progression has not been addressed. Here, we determined whether each TLR modulates JE, using several TLR-deficient mouse strains (TLR2, TLR3, TLR4, TLR7, TLR9). Surprisingly, among the tested TLR-deficient mice there were contrasting results in TLR3(-/-) and TLR4(-/-) mice, i.e. TLR3(-/-) mice were highly susceptible to JE, whereas TLR4(-/-) mice showed enhanced resistance to JE. TLR3 ablation induced severe CNS inflammation characterized by early infiltration of inflammatory CD11b(+)Ly-6Chigh monocytes along with profoundly increased viral burden, proinflammatory cytokine/chemokine expression as well as BBB permeability. In contrast, TLR4(-/-) mice showed mild CNS inflammation manifested by reduced viral burden, leukocyte infiltration and proinflammatory cytokine expression. Interestingly, TLR4 ablation provided potent in vivo systemic type I IFN innate response, as well as ex vivo type I IFN production associated with strong induction of antiviral PRRs (RIG-I, MDA5), transcription factors (IRF-3, IRF-7), and IFN-dependent (PKR, Oas1, Mx) and independent ISGs (ISG49, ISG54, ISG56) by alternative activation of IRF3 and NF-κB in myeloid-derived DCs and macrophages, as compared to TLR3(-/-) myeloid-derived cells which were more permissive to viral replication through impaired type I IFN innate response. TLR4 ablation also appeared to mount an enhanced type I IFN innate and humoral, CD4(+) and CD8(+) T cell responses, which were mediated by altered immune cell populations (increased number of plasmacytoid DCs and NK cells, reduced CD11b(+)Ly-6C(high) monocytes) and CD4(+)Foxp3(+) Treg number in lymphoid tissue. Thus, potent type I IFN innate and adaptive immune responses in the absence of TLR4 were closely coupled with reduced JE lethality. Collectively, these results suggest that a balanced triggering of TLR signal array by viral components during JE progression could be responsible for determining disease outcome through regulating negative and positive factors.

Post-liver transplant hepatitis C virus recurrence: an unresolved thorny problem

Hepatitis C virus (HCV)-related cirrhosis represents the leading cause of liver transplantation in developed, Western and Eastern countries. Unfortunately, liver transplantation does not cure recipient HCV infection: reinfection universally occurs and disease progression is faster after liver transplant. In this review we focus on what happens throughout the peri-transplant phase and in the first 6-12 mo after transplantation: during this crucial period a completely new balance between HCV, liver graft, the recipient's immune response and anti-rejection therapy is achieved that will deeply affect subsequent outcomes. Nearly all patients show an early graft reinfection, with HCV viremia reaching and exceeding pre-transplant levels; in this setting, histological assessment is essential to differentiate recurrent hepatitis C from acute or chronic rejection; however, differentiating the two patterns remains difficult. The host immune response (mainly cellular mediated) appears to be crucial both in the control of HCV infection and in the genesis of rejection, and it is also strongly influenced by immunosuppressive treatment. At present no clear immunosuppressive strategy could be strongly recommended in HCV-positive recipients to prevent HCV recurrence, even immunotherapy appears to be ineffective. Nonetheless it seems reasonable that episodes of rejection and over-immunosuppression are more likely to enhance the risk of HCV recurrence through immunological mechanisms. Both complete prevention of rejection and optimization of immunosuppression should represent the main goals towards reducing the rate of graft HCV reinfection. In conclusion, post-transplant HCV recurrence remains an unresolved, thorny problem because many factors remain obscure and need to be better determined.

Frequency of regulatory T-cell and hepatitis C viral antigen-specific immune response in recurrent hepatitis C after liver transplantation

INTRODUCTION

Regulatory T (Treg) and type 1 regulatory T (Tr1) cells facilitate hepatitis C virus (HCV) recurrence after orthotopic liver transplantation (OLT). However, their frequencies and effects on HCV-specific immune responses have not been well investigated.

METHODS

We determined Treg and Tr1 frequencies in OLT patients with hepatitis C and assessed their associations with HCV-specific T cell responses. These patients comprised the following groups: an early post-transplantation group (n=14); an OLT-chronic active hepatitis C group (n=14) with active hepatitis C (alanine aminotransferase of>upper limit of normal/positive for HCV-RNA); an OLT-persistently normal alanine aminotransferase group (n=12) without active hepatitis C (not interferon/positive for HCV-RNA); and an OLT-sustained viral response group (n=6) with sustained viral responses using interferon treatment (negative for HCV-RNA). The frequencies of HCV-specific CD4+ T cells that secreted interferon-γ were determined by enzyme-linked immunosorbent spot assay (except for the OLT early group).

RESULTS

Treg and Tr1 frequencies were low during the early post-transplantation period. OLT patients with sustained viral responses had lower Treg frequencies than those with chronic hepatitis C, whereas Tr1 frequencies were significantly reduced in OLT patients with persistently normal alanine aminotransferase levels compared to those with chronic hepatitis C (p<0.05). Treg frequencies positively correlated with HCV NS3 antigen-specific interferon-γ responses, which corresponded to HCV clearance.

CONCLUSIONS

Increased Treg frequencies and reduced HCV-NS3 antigen-specific responses recovered after viral eradication in post-OLT chronic hepatitis C patients. Reduced Tr1 frequencies were associated with hepatitis activity control, which may facilitate controlling chronic hepatitis C in patients after OLT.

Major challenges limiting liver transplantation in the United States

Liver transplantation is the gold standard of care in patients with end-stage liver disease and those with tumors of hepatic origin in the setting of liver dysfunction. From 1988 to 2009, liver transplantation in the United States grew 3.7-fold from 1713 to 6320 transplants annually. The expansion of liver transplantation is chiefly driven by scientific breakthroughs that have extended patient and graft survival well beyond those expected 50 years ago. The success of liver transplantation is now its primary obstacle, as the pool of donor livers fails to keep pace with the growing number of patients added to the national liver transplant waiting list. This review focuses on three major challenges facing liver transplantation in the United States and discusses new areas of investigation that address each issue: (1) the need for an expanded number of useable donor organs, (2) the need for improved therapies to treat recurrent hepatitis C after transplantation and (3) the need for improved detection, risk stratification based upon tumor biology and molecular inhibitors to combat hepatocellular carcinoma.

Regulatory T cells in HBV and HCV liver diseases: implication of regulatory T lymphocytes in the control of immune response

IMPORTANCE OF THE FIELD

Hepatic cirrhosis is a frequent consequence of chronic hepatitis infection (HBV and HCV) or alcohol abuse and the most common cause of hepatocellular carcinoma (HCC). Currently, liver transplantation remains the only effective therapeutic approach for cirrhosis-related HCC patients. The evolution of the pathology strongly depends on immunological mechanisms.

AREAS COVERED IN THIS REVIEW

Despite the presence of specific T cells, viral chronic infection and continuous tumor growth suggest a failure of immune control. It appears that direct suppression of antiviral or antitumor effector cells by regulatory T cells plays a pivotal role in the impairment of immune response. Several types of regulatory T cells have been described, natural regulatory T cells (nTreg) and induced-type 1 regulatory T cells (Tr1) being the best characterized.

WHAT THE READER WILL GAIN

Currently, there is no evidence for a direct implication of regulatory T cells in the evolution of hepatitis, especially concerning chronic infection, cirrhosis late stage and HCC progress. However, recent studies show that regulatory T cells are implicated in the modulation of HBV- and HCV-associated immune response, thus, promoting HCC progress.

TAKE HOME MESSAGE

Therefore, nTreg and Tr1 cells seem to play an important role in the control of immune response leading to chronic hepatitis infection and progression of the pathology to cirrhosis and HCC.

Management of posttransplant hepatitis C infection

PURPOSE OF REVIEW

Chronic hepatitis C virus (HCV) infection is the leading cause of liver transplantation. Outcome of HCV-associated liver transplantation has been worse than transplantation from other causes. This is mostly related to universal recurrence of HCV in the allograft leading to graft and patient loss or retransplantation. Current antiviral therapies (AVTs) are inadequate and ineffective in the vast majority of the patients with intolerable side effects in most. However, a sustained virologic response (SVR) is associated with improved graft and patient survival. New specifically targeted AVTs for HCV (STAT-C) agents in development will significantly improve the success of AVT. This review focuses on recent data in peritransplant management of HCV with special emphasis on predictors of outcome, diagnosis, prevention and control of reinfection with newer treatments on the horizon.

RECENT FINDINGS

In the immediate pretransplant setting, AVT should be considered in select patients to eradicate the virus. Careful donor selection, immunosuppression (IMS) modulation with steroid and calcineurin inhibitor (CNI) minimization, avoidance of T-cell-depleting treatments and acute rejection episodes, and control of metabolic syndrome can improve allograft outcomes and improve the response to AVT. AVT prior to significant damage to the allograft is strongly recommended.

SUMMARY

With modified novel IMS protocols, careful donor selection, and AVT prior to significant damage to the allograft we can improve the outcome of posttransplant hepatitis C infection. Albeit there are no available data on new antiviral agents, STAT-Cs will have a significant impact in this setting in the near future.