Differences in HCV-specific T cell responses between chronic HCV infection and HIV/HCV co-infection

SILVI, an open-source pipeline for T-cell epitope selection

High-throughput screening of available genomic data and identification of potential antigenic candidates have promoted the development of epitope-based vaccines and therapeutics. Several immunoinformatic tools are available to predict potential epitopes and other immunogenicity-related features, yet it is still challenging and time-consuming to compare and integrate results from different algorithms. We developed the R script SILVI (short for: from in silico to in vivo), to assist in the selection of the potentially most immunogenic T-cell epitopes from Human Leukocyte Antigen (HLA)-binding prediction data. SILVI merges and compares data from available HLA-binding prediction servers, and integrates additional relevant information of predicted epitopes, namely BLASTp alignments with host proteins and physical-chemical properties. The two default criteria applied by SILVI and additional filtering allow the fast selection of the most conserved, promiscuous, strong binding T-cell epitopes. Users may adapt the script at their discretion as it is written in open-source R language. To demonstrate the workflow and present selection options, SILVI was used to integrate HLA-binding prediction results of three example proteins, from viral, bacterial and parasitic microorganisms, containing validated epitopes included in the Immune Epitope Database (IEDB), plus the Human Papillomavirus (HPV) proteome. Applying different filters on predicted IC50, hydrophobicity and mismatches with host proteins allows to significantly reduce the epitope lists with favourable sensitivity and specificity to select immunogenic epitopes. We contemplate SILVI will assist T-cell epitope selections and can be continuously refined in a community-driven manner, helping the improvement and design of peptide-based vaccines or immunotherapies. SILVI development version is available at: github.com/JoanaPissarra/SILVI2020 and https://doi.org/10.5281/zenodo.6865909.

Restoration of HCV-Specific Immune Responses with Antiviral Therapy: A Case for DAA Treatment in Acute HCV Infection

Worldwide, 71 million individuals are chronically infected with Hepatitis C Virus (HCV). Chronic HCV infection can lead to potentially fatal outcomes including liver cirrhosis and hepatocellular carcinoma. HCV-specific immune responses play a major role in viral control and may explain why approximately 20% of infections are spontaneously cleared before the establishment of chronicity. Chronic infection, associated with prolonged antigen exposure, leads to immune exhaustion of HCV-specific T cells. These exhausted T cells are unable to control the viral infection. Before the introduction of direct acting antivirals (DAAs), interferon (IFN)-based therapies demonstrated successful clearance of viral infection in approximately 50% of treated patients. New effective and well-tolerated DAAs lead to a sustained virological response (SVR) in more than 95% of patients regardless of viral genotype. Researchers have investigated whether treatment, and the subsequent elimination of HCV antigen, can reverse this HCV-induced exhausted phenotype. Here we review literature exploring the restoration of HCV-specific immune responses following antiviral therapy, both IFN and DAA-based regimens. IFN treatment during acute HCV infection results in greater immune restoration than IFN treatment of chronically infected patients. Immune restoration data following DAA treatment in chronically HCV infected patients shows varied results but suggests that DAA treatment may lead to partial restoration that could be improved with earlier administration. Future research should investigate immune restoration following DAA therapies administered during acute HCV infection.

A Comprehensive Analysis of the Impact of HIV on HCV Immune Responses and Its Association with Liver Disease Progression in a Unique Plasma Donor Cohort

Objective

Human Immunodeficiency Virus (HIV) and Hepatitis C virus (HCV) co-infection is recognized as a major cause of morbidity and mortality among HIV-1 infected patients. Our understanding of the impact of HIV infection on HCV specific immune responses and liver disease outcome is limited by the heterogeneous study populations with genetically diverse infecting viruses, varying duration of infection and anti-viral treatment.

Methods

Viral-specific immune responses in a cohort of 151 HCV mono- and HIV co-infected former plasma donors infected with a narrow source of virus were studied. HCV and HIV specific T cell responses were correlated with clinical data.

Results

HIV-1 accelerated liver disease progression and decreased HCV specific T cell immunity. The magnitude of HCV specific T cell responses inversely correlated with lower HCV RNA load and reduced liver injury as assessed by non-invasive markers of liver fibrosis. HIV co-infection reduced the frequency of HCV specific CD4⁺ T cells with no detectable effect on CD8⁺ T cells or neutralizing antibody levels.

Conclusion

Our study highlights the impact of HIV co-infection on HCV specific CD4+ T cell responses in a unique cohort of patients for both HCV and HIV and suggests a crucial role for these cells in controlling chronic HCV replication and liver disease progression.

Natural history of liver disease and effect of hepatitis C virus on HIV disease progression

PURPOSE OF REVIEW

Due to high prevalence rates, the hepatitis C virus (HCV) and the HIV cause two viral infections of global importance. Shared routes of transmission lead to a high number of dually infected individuals especially in specific populations such as intravenous drug users or people from highly endemic regions for both viruses. Treatment progress made in the field of HIV in the past three decades diminished the number of HIV patients who die from opportunistic infections and enabled a rise of HCV-associated liver disease in the HIV-HCV-coinfected population.

RECENT FINDINGS

An HIV-HCV coinfection is mainly characterized by a faster progression to liver cirrhosis that may lead to hepatic decompensation or the development of hepatocellular carcinoma (HCC). The treatment of HIV with highly active antiretroviral therapy (HAART) may only partly reverse this effect by the restoration of the immune system. Although no clear deleterious effect of HCV on the course of HIV infection is described, an increased HIV-associated and non-HIV-associated mortality has been described in patients not cured from their HCV infection.

SUMMARY

In this article, we review the latest knowledge on the natural course of HCV in the HIV-infected population, the role of HIV treatment, and the possible effects of HCV on HIV disease progression.

Natural history and treatment of HCV/HIV coinfection: Is it time to change paradigms?

Evidence over the past decades have shown that HIV/HCV coinfected patients did not respond as well to HCV therapy as HCV mono-infected patients. However, these paradigms are being recently reassessed with the improvements of care for HIV and HCV patients. This article reviews these original paradigms and how the new data is impacting upon them. Treatment efficacy now appears comparable for HIV/HCV coinfected and HCV mono-infected patients, while liver fibrosis progression is increasingly similar in optimally managed patients. Additional importance of therapy is directed to drug-drug interactions and the impact of HCV reinfection, as well as the possibility of transmitted drug resistance.

Expression of inhibitory markers is increased on effector memory T cells during hepatitis C virus/HIV coinfection as compared to hepatitis C virus or HIV monoinfection

OBJECTIVE

Hepatitis C virus (HCV)/HIV coinfection is associated with rapid progression of hepatic fibrosis and liver disease. T-cell response has been implicated in the pathophysiological outcome of the disease.

DESIGN

This study sought to evaluate the role of memory T-cell exhaustion in enhancing immune dysfunction during coinfection.

METHODS

Sixty-four patients were included in the study; HCV monoinfected (n = 21), HIV monoinfected (n = 23), HCV/HIV coinfected (n = 20), and healthy controls (n = 20). Peripheral blood mononuclear cells (PBMCs) were isolated; immunophenotyped and functional assays were performed.

RESULTS

A significant increase in the naive T cells and central memory T cells and a marked reduction in effector memory T cells (TEM) were observed with coinfection as compared to monoinfection. Inhibitory markers programmed death 1 (PD-1) and T-cell immunoglobulin and mucin domain containing molecule 3 (TIM3) were highly upregulated on TEM in coinfection and functionally, these TEM cells displayed lowered proliferation. Increased expression of PD-1 and TIM3 correlated with decreased levels of CD8+CD107a+ TEM cells in coinfection. Pro-inflammatory cytokines interferon-γ and interleukin-2 (IL-2) secretion by TEM cells were also reduced during chronic viral infection. Secretion of IL-10, a human cytokine synthesis inhibitory factor, was significantly upregulated in CD4 TEM with HCV/HIV coinfection in comparison to HCV monoinfection.

CONCLUSION

TEM cells play an important role during viral infection and enhanced expression of inhibitory markers is associated with decreased proliferation and cytotoxicity and increased IL-10 production, which was pronounced in HCV/HIV coinfection. Thus, decreased TEM functionality contributes to diminished host immune responses during HCV/HIV coinfection as compared to HCV or HIV monoinfection.

HIV and co-infections

Despite significant reductions in morbidity and mortality secondary to availability of effective combination anti-retroviral therapy (cART), human immunodeficiency virus (HIV) infection still accounts for 1.5 million deaths annually. The majority of deaths occur in sub-Saharan Africa where rates of opportunistic co-infections are disproportionately high. In this review, we discuss the immunopathogenesis of five common infections that cause significant morbidity in HIV-infected patients globally. These include co-infection with Mycobacterium tuberculosis, Cryptococcus neoformans, hepatitis B virus, hepatitis C virus, and Plasmodium falciparum. Specifically, we review the natural history of each co-infection in the setting of HIV, the specific immune defects induced by HIV, the effects of cART on the immune response to the co-infection, the pathogenesis of immune restoration disease (IRD) associated with each infection, and advances in the areas of prevention of each co-infection via vaccination. Finally, we discuss the opportunities and gaps in knowledge for future research.

Hepatitis C Virus and HIV Type 1 Co-Infection

Around 33 million people worldwide are living with Human Immunodeficiency Virus (HIV) infection, and approximately 20-30% of HIV-infected individuals are also infected with Hepatitis C virus (HCV). The main form of HCV transmission is via the blood borne route; high rates of co-infection are found in intravenous drug users with HCV prevalence rates as high as 90%. Introduction of effective antiretroviral therapy (ART) has led to a significant decline in HIV-related morbidity, but at the same time the incidence of HCV related liver disease is increasing in the co-infected population. Meta analysis has revealed that individuals who are co-infected with HIV/HCV harbor three times greater risk of progression to liver disease than those infected with HCV alone. Increased risk of progression to Acquired Immunodeficiency Syndrome (AIDS) and AIDS-related deaths is shown among the co-infected patients by some studies, suggesting that HCV infection may accelerate the clinical course of HIV infection. HCV may also affect the incidence of liver toxicity associated with ART, affecting the management of HIV infection. There is a lack of optimal therapeutic approaches to treat HCV infection in HIV co-infected patients. This review discusses recent literature pertaining HIV/HCV co-infection, in addition to providing a snapshot of impact of co-infection on human genome at the level of gene expression and its regulation by microRNAs (miRNAs).

Complementary role of HCV and HIV in T-cell activation and exhaustion in HIV/HCV coinfection

Objectives

To investigate whether T-cell activation and exhaustion is linked to HCV- and HIV disease parameters in HIV/HCV infected individuals, we studied T-cell characteristics in HIV/HCV coinfected patients and controls.

Methods

14 HIV/HCV coinfected, 19 HCV monoinfected, 10 HIV monoinfected patients and 15 healthy controls were included in this cross-sectional study. Differences in expression of activation and exhaustion markers (HLA-DR, CD38, PD-1, Tim-3 and Fas) and phenotypic markers on CD4⁺ and CD8⁺ T-cells were analysed by flow cytometry and were related to HCV disease parameters (HCV-viremia, ALT and liver fibrosis).

Results

Frequencies of activated CD4⁺ and CD8⁺ T-cells were higher in HIV/HCV-coinfected compared to healthy controls and HCV or HIV mono-infected individuals. Coinfected patients also showed high expression of the exhaustion marker PD-1 and death receptor Fas. In contrast, the exhaustion marker Tim-3 was only elevated in HIV-monoinfected patients. T-cell activation and exhaustion were correlated with HCV-RNA, suggesting that viral antigen influences T-cell activation and exhaustion. Interestingly, increased percentages of effector CD8⁺ T-cells were found in patients with severe (F3–F4) liver fibrosis compared to those with no to minimal fibrosis (F0–F2).

Conclusions

HIV/HCV coinfected patients display a high level of T-cell activation and exhaustion in the peripheral blood. Our data suggest that T-cell activation and exhaustion are influenced by the level of HCV viremia. Furthermore, high percentages of cytotoxic/effector CD8⁺ T-cells are associated with liver fibrosis in both HCV monoinfected and HIV/HCV coinfected patients.

Transient liver injury associated with the early recovery of HCV-specific T-cell responses and HCV rebound in HIV-1/HCV coinfected patients undergoing highly active antiretroviral therapy

OBJECTIVES

HIV-1/hepatitis C virus (HCV) coinfection accelerates the progression of liver disease to cirrhosis, particularly in individuals with low CD4 T-cell counts. Highly active antiretroviral therapy (HAART) can significantly increase HCV-specific T-cell responses; however, it remains unclear whether the restoration of HCV-specific T cells by HAART is associated with liver injury in these coinfection patients.

METHODS

A total of 32 HIV-1/HCV coinfected patients and 14 HCV monoinfected patients were enrolled, and 13 coinfected patients were initialized HAART and followed up for 6 months. HCV-specific interferon-γ responses to HCV core and NS3A proteins were examined by enzyme-linked immunosorbent spot.

RESULTS

HCV-specific interferon-γ responses to HCV core and NS3A proteins were impaired in HIV-1/HCV-coinfected patients as compared with those in HCV monoinfected patients. The impaired HCV-specific T-cell responses could be efficiently restored during the early phase of HAART, independent of HCV status, and were positively associated with increased CD4 T-cell counts. In addition, this recovery of HCV-specific T-cell responses occurred simultaneously with elevated serum alanine aminotransferase levels in HCV viremic patients and in patients with HCV rebound, but not in HCV nonviremic patients after 6 months of HAART.

CONCLUSIONS

The recovery of HCV-specific T-cell responses by HAART may lead to transient liver injury in patients with HIV-1/HCV coinfection, suggesting that early anti-HCV therapy before HAART may reduce the risk of liver injury and therefore may be beneficial to HIV-1/HCV-coinfected patients.

Challenges for HCV vaccine development in HIV-HCV coinfection

It is estimated that 4-5 million HIV-infected patients are coinfected with HCV. The impact of HIV on the natural course of HCV infection is deleterious. This includes a higher rate of HCV persistence and a faster rate of fibrosis progression. Coinfected patients show poor treatment outcome following standard HCV therapy. Although direct antiviral agents offer new therapeutic options, their use is hindered by potential drug interactions and toxicity in HIV-infected patients under HAART. Overtime, a large reservoir of HCV genotype 1 patients will accumulate in resource poor countries where the hepatitis C treatment is not easily affordable and HIV therapy remains the primary health issue for coinfected individuals. HCV vaccines represent a promising strategy as an adjunct or alternative to current HCV therapy. Here, the authors review the pathogenesis of hepatitis C in HIV-infected patients, with a focus on the impact of HIV on HCV-specific immune responses and discuss the challenges for vaccine development in HIV-HCV coinfection.

Lack of TGF-β production by hepatitis C virus-specific T cells during HCV acute phase is associated with HCV clearance in HIV coinfection

BACKGROUND & AIMS

Immunity and genetic factors govern the recovery from acute hepatitis C virus (HCV) infection. No predictive factors have been yet identified in patients coinfected with the human immunodeficiency virus (HIV). We investigated whether early T cell responses to HCV producing transforming-growth-factor beta (TGF-β) predict the outcome of acute HCV coinfection, independently of the IL-28B gene polymorphism.

METHODS

Intracellular cytokine staining assays against HCV-core, E1, NS2, and NS4 overlapping peptides were used for the analysis of peripheral HCV-specific TGF-β-producing T cells. Patients were genotyped for IL-28B polymorphisms. Healthy donors' samples were tested as controls. Twenty-four acute hepatitis C-HIV+ patients were followed-up for 15 months defining two groups: (A) Recovered (n=16, 5 spontaneous recoveries, 11 sustained virologic response after treatment), (B) Chronic HCV (n=8, 4 spontaneous chronic course, 4 therapeutic failures).

RESULTS

During the acute pretreatment phase, core/NS2-specific TGF-β-producing CD4+ and/or CD8+ T cells were detected in 8/24 (33%) patients. Lack of anti-HCV TGF-β+ cells was characteristic of healthy donors and Group A, except for 2 cases, with frequencies significantly lower than in Group B (p=0.04 and 0.01), and was associated with recovery in 14/16 cases. Presence of anti-HCV TGF-β+ cells was associated with persistent viremia in 6/8 cases (p=0.005). This profile remained stable over time. Such TGF-β production was independent of the rs129679860 SNP (p=1.0) which was not associated with recovery (p=1.0).

CONCLUSIONS

During acute hepatitis C, pre-therapeutic HCV-specific TGF-β-producing T cells are a new marker independent of the IL-28B gene polymorphism, predicting the lack of spontaneous or therapeutic HCV clearance.

Update on hepatitis C virus-specific immunity

PURPOSE OF REVIEW

The goal of this study is to review key recent findings related to the immunopathogenesis of hepatitis C virus (HCV) infection, especially in regards to T lymphocytes. It aims to complement other reviews in this issue on the roles of host genetics (IL-28B), acute HCV infection (when disease outcome is determined) and other factors that may influence fibrosis progression (microbial translocation). The main focus is on specific immunity and T cells in the context of success and failure to control viral infection.

RECENT FINDINGS

This review focuses on two areas of intense interest in the recent literature: the relationship between the human leukocyte antigen (HLA), class I-restricted T-cell responses and the evolution of the virus and the role of inhibitory markers on T cells in the immunopathogenesis of HCV. When appropriate, we compare findings from studies of HIV-specific immunity.

SUMMARY

From examining the virus and the mutational changes associated with T-cell responses and from analyzing the markers on T cells, there have been numerous advances in the understanding of immune evasion mechanisms employed by HCV.

Immunopathogenesis of HIV/hepatitis C virus coinfection

As a result of shared infection routes, approximately 25% of individuals infected with HIV in North America are also infected with hepatitis C virus (HCV). In the setting of HIV coinfection, the course of HCV disease is more aggressive, resulting in higher HCV viral loads and a more rapid progression of liver pathology. With the success of HAART, HCV-related end-stage liver disease has become a leading cause of morbidity and mortality in HIV/HCV-coinfected patients. In this article, we will discuss recent studies examining the immune response during HIV and HCV coinfection, focusing on alterations or dysfunctions in virus-specific T-cell responses that may play a role in the immunopathogenesis of HIV/HCV coinfection. Summarizing the impact of HIV coinfection on HCV-specific T-cell immunity and highlighting some of the proposed mechanisms of T-cell dysfunction in HIV/HCV-coinfected individuals may uncover information that could lead to new treatment strategies for these patients experiencing accelerated liver disease and generally poorer outcomes than their HCV-monoinfected counterparts.

HCV-specific T-cell responses in HIV/hepatitis C virus-coinfected patients on highly active antiretroviral therapy are comparable to those observed in hepatitis C virus-monoinfected individuals

BACKGROUND

Cellular responses against hepatitis C virus (HCV) are impaired in HIV/HCV-coinfected patients showing uncontrolled viral replication and immune suppression. Very few studies have explored to what extent HCV-specific response improves as a consequence of control of HIV replication by highly active antiretroviral therapy. We compared HCV-specific T-cell responses between HIV/HCV-coinfected patients, showing complete viral suppression, and HCV-monoinfected patients.

METHODS

HCV-specific T-cell responses were examined in 50 interferon-naive patients with chronic hepatitis C: 27 HCV-mono-infected and 23 HIV/HCV-coinfected on highly active antiretroviral therapy and undetectable HIV load. Production of interferon-γ and tumor necrosis factor-α was simultaneously measured in response to genotype-matched overlapping peptides spanning the whole HCV proteome by flow cytometry. Differences between groups were tested using nonparametric tests.

RESULTS

More than half of patients presented CD4+ (60%) or CD8+ (57%) response to at least one HCV protein with no significant differences between both groups. Intensity and breadth of response were also similar between groups. The functional profile of response was represented, in both groups, mainly by monofunctional subsets, although there were some differences between CD4+ and CD8+ T-cell response. CD8+ response was mediated almost exclusively by monofunctional interferon-γ+ cells, whereas bifunctional interferon-γ+ tumor necrosis factor-α+ cells showed a moderate contribution to CD4+ response. Most of the CD8+ response was mediated by interferon-γ, whereas tumor necrosis factor-α was the highest contributor to CD4+ response.

CONCLUSIONS

Our study demonstrates that in HIV/HCV-coinfected patients with maximal HIV suppression under highly active antiretroviral therapy, several characteristics of anti-HCV T-cell response are similar to those found in HCV-monoinfected patients, suggesting that control of HIV replication might improve HCV-specific T-cell response in HIV/HCV-coinfected patients.

Stronger hepatitis C virus-specific CD8+ T-cell responses in HIV coinfection

Hepatitis C virus (HCV) is a widespread chronic infection that shares routes of transmission with human immunodeficiency virus (HIV). Thus, coinfection with these viruses is a relatively common and growing problem. In general, liver disease develops over years with HIV coinfection, when compared to decades in HCV monoinfection. The role of the immune system in the accelerated pathogenesis of liver disease in HIV/HCV coinfection is not clear. In this study, we compared the frequency, magnitude, breadth and specificity of peripheral blood CD4+ and CD8+ T-cell responses between HCV-monoinfected and HCV/HIV-coinfected individuals and between HIV/HCV-coinfected subgroups distinguished by anti-HCV antibody and HCV RNA status. While HIV coinfection tended to reduce the frequency and breadth of anti-HCV CD8+ T-cell responses in general, responses that were present were substantially stronger than in monoinfection. In all groups, HCV-specific CD4+ T-cell responses were rare and weak, independent of either nadir or concurrent CD4+ T-cell counts of HIV-infected individuals. Subgroup analysis demonstrated restricted breadth of CD8+ HCV-specific T-cell responses and lower B-cell counts in HIV/HCV-coinfected individuals without anti-HCV antibodies. The greatest difference between HIV/HCV-coinfected and HCV-monoinfected groups was substantially stronger HCV-specific CD8+ T-cell responses in the HIV-coinfected group, which may relate to accelerated liver disease in this setting.

Elevated TGF-β1 levels might protect HCV/ HIV-coinfected patients from liver fibrosis

BACKGROUND

HIV accelerates hepatitis C virus (HCV)-induced liver fibrosis by mechanisms not well understood. As HIV dysregulates transforming growth factor-β1 (TGF-β1) and T regulatory (Treg) cells, both of which are involved in hepatic fibrogenesis, herein we describe their influence on liver fibrosis staging in patients with chronic hepatitis C with and without HIV coinfection.

METHODS

Eighty-eight subjects (42 HIV/HCV co-infected patients, 20 HCV-monoinfected patients, and 26 healthy controls) were examined. Treg cells (CD4+Foxp3+) were measured in peripheral blood using flow cytometry. An enzyme immunoassay was used to measure TGF-β1 in plasma. Liver fibrosis staging was estimated using elastometry and advanced liver fibrosis was considered for ≥ 9·5 kPa (F3-F4 Metavir estimates).

RESULTS

Treg cells were increased in HIV/HCV-coinfected patients compared with HCV-monoinfected patients (P = 0·004), whereas TGF-β1 levels were similar in both groups of patients. While Treg cells levels were similar in both null-mild and advanced liver fibrosis patients, a high level of TGF-β1 was found in patients with low levels of liver fibrosis compared with those with advanced liver fibrosis [14·9 ng mL(-1) (5·6-37·9) vs. 5·5 ng mL(-1) (1·9-7·9) respectively P = 0·007]. In a multivariate logistic regression model, elevated TGF-β1 levels were significantly associated with not having advanced liver fibrosis [OR: 0·13 (95% CI: 0·02-0·71), P = 0·019].

CONCLUSIONS

While Treg cells do not influence liver fibrosis staging, elevated TGF-β1, probably through its anti-inflammatory effects, might protect HCV/HIV-coinfected patients from liver fibrosis.

PD-1 expression on peripheral CD8+ TEM/TEMRA subsets closely correlated with HCV viral load in chronic hepatitis C patients

BACKGROUND

Tight correlation between host circulating CD8+ T cell-mediated immune response and control of viral replication is classical characteristic of long-term HCV infection. CD8+ T cell maturation/activation markers are expected to be associated with viral replication and disease progression in chronic HCV infection. The aim of the present study was to explore novel markers on CD8+ T cells with ability to evaluate HCV viral replication and disease progression.

METHODS

PBMCs were isolated from 37 chronic HCV-infected patients and 17 healthy controls. Distributed pattern of CD8+ T cells subsets and expression of PD-1, CD38, HLA-DR and CD127 were analyzed by flow cytometry. The correlation between expression of surface markers and HCV viral load or ALT was studied.

RESULTS

Declined naïve and increased TEMRA CD8+ T subsets were found in HCV-infected individuals compared with healthy controls. Percentage and MFI of PD-1, CD38 and HLA-DR on all CD8+ T cell subsets were higher in HCV-infected patients than healthy controls. In contrast, CD127 expression on CD8+ TCM showed an opposite trend as PD-1, CD38 and HLA-DR did. In chronic HCV infection, MFI of PD-1 on CD8+ TEM (p < 0.0001) and TEMRA (p = 0.0015) was positively correlated with HCV viral load while HLA-DR expression on non-naive CD8+ T cell subsets (p < 0.05) was negatively correlated with HCV viral load.

CONCLUSION

PD-1 level on peripheral CD8+ TEM/TEMRA was highly correlated with HCV viral load in chronic HCV-infected patients, which made PD-1 a novel indicator to evaluate HCV replication and disease progression in chronic hepatitis C patients.

Pathogenesis of HIV-HCV Coinfection

Hepatitis C virus (HCV) and HIV-1 are often harbored in the same host, establishing chronic infections typically characterized by persistent viremia. HIV-1 has deleterious effects on the course of HCV infection by increasing the rate of HCV viral persistence, quantitative HCV RNA levels, and ultimately the liver fibrosis progression rate. Conversely, HCV may blunt the effectiveness of immune reconstitution following antiretroviral therapy in HIV-infected individuals. Better understanding of the pathogenic mechanisms underlying these clinical observations may facilitate novel and effective therapeutic interventions that tackle the clinical conundrums raised by HIV/HCV coinfection.

Hepatitis virus immune restoration disease of the liver

PURPOSE OF REVIEW

Co-infection of HIV with hepatitis B virus or hepatitis C virus is common. Hepatotoxicity (grade 3 or 4 transaminitis) after highly active antiretroviral therapy occurs more frequently in either hepatitis B virus or hepatitis C virus co-infection. The cause of abnormal alanine aminotransferase following the initiation of highly active antiretroviral therapy is often multifactorial, and may include immune restoration disease. Since the widespread use of highly active antiretroviral therapy, liver disease secondary to viral hepatitis has become one of the most common causes of death in HIV infected individuals. A better understanding of the immunopathogenesis, diagnosis and treatment of hepatitis immune restoration disease is urgently needed, therefore.

RECENT FINDINGS

Our current understanding of the immunopathogenesis of hepatitis immune restoration disease is limited but it is likely that hepatic damage is secondary to recruitment of both antigen-specific and nonantigen-specific mononuclear cells to the liver, possibly mediated by IFN-gamma. HIV-hepatitis B virus co-infected individuals with low CD4 T-cells and elevated hepatitis B virus DNA and alanine aminotransferase prior to initiation of highly active antiretroviral therapy are at increased risk of hepatitis B virus immune restoration disease. Risk factors for hepatitis C virus immune restoration disease are less well defined. Although clinical deterioration can occur, hepatitis immune restoration disease has also been associated with successful clearance of both hepatitis B virus and hepatitis C virus.

SUMMARY

Further randomized clinical trials are needed to develop improved management strategies for hepatitis immune restoration disease.

Acute hepatitis C in HIV-infected patients: rare spontaneous clearance correlates with weak memory CD4 T-cell responses to hepatitis C virus

OBJECTIVES

To explore the parameters of specific immunity to hepatitis C virus (HCV) associated with virus clearance during acute HCV infection in HIV coinfection.

METHODS

HIV-infected patients without prior HCV infection were prospectively enrolled for acute hepatitis C and followed up over 15 months. HCV-specific T cells were assessed by proliferation, ELISpot, intracellular cytokine staining and pentamer assays. Pegylated-interferon-alpha and ribavirin were proposed if HCV persisted at M3.

RESULTS

Thirty eight acutely HCV-infected HIV-positive patients were enrolled. HCV genotypes were predominantly 4 and 1. Five patients (13%) showed spontaneous clearance and 20 initiated treatment, of whom 13 (65%) showed sustained virologic responses. Before M3, HCV-specific proliferative responses observed in 35% cases, were associated with lower HCV viral load (P = 0.04) and predictive of spontaneous clearance (P = 0.02), particularly anti-NS4 responses (P = 0.03). These HCV-specific proliferative responses were associated with HIV-p24-specific responses (P = 0.002) independently from the HIV stage. Interferon-gamma-producing T cells specific for HCV were detectable ex vivo in 81% cases but at low intensity (<150 spot forming cells/10 peripheral blood mononuclear cells) and were independent of the HCV outcome. Low frequencies of pentamer-positive HCV-specific CD8 cells (0.01-0.05%) detected in nine of 12 patients were mainly effector-memory PD-1-negative T cells. Twelve days of HCV-specific in-vitro culture induced amplification of CD4 T cells coproducing interleukin-2 and interferon-gamma but rarely of CD8 T cells.

CONCLUSION

Acute HCV infection in HIV-coinfected patients is characterized by a low rate of spontaneous clearance and weak HCV-specific memory T cells, not strictly related to HIV-induced immune defects, and which correlate with virus clearance.

Coinfection with HIV-1 and HCV--a one-two punch

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease, cirrhosis, and death; it is estimated that 180 million persons are infected with HCV worldwide. The consequences of HCV are worse in those who are coinfected with human immunodeficiency virus 1 (HIV-1), which is unfortunately a common scenario because of shared risk factors of the viruses. More studies into effects of HCV/HIV-1 coinfection are needed, but efforts have been hampered by limitations in our understanding of the combined pathogenesis of the 2 viruses. Gaining insight into the mechanisms that underlie the immunopathogenesis of these persistent viral infections could lead to new therapeutic strategies for patients with HCV/HIV-1 coinfection.

[Role of tenofovir in HIV and hepatitis C virus coinfection]

Chronic hepatitis C virus (HCV) infection is common in HIV-infected individuals, especially if the route of infection is intravenous (e.g. intravenous drug use or blood transfusion). Prognosis is poorer in patients with HCV and HIV coinfection than in those with HCV monoinfection, mainly due to the immunodepression caused by HIV infection and probably also to a direct effect of HIV on the liver. Moreover, although antiretroviral therapy can cause liver damage, there is little doubt about the net benefits obtained with triple therapy in coinfected individuals, since suppression of HIV replication and immune recovery help to halt liver damage. However, not all antiretroviral agents are equal and those with the lowest hepatotoxicity and best metabolic profile should be used in coinfected patients, since hepatic steatosis accelerates progression of hepatic fibrosis and insulin resistance hampers the success of treatment with interferon and ribavirin. Tenofovir is currently one of the safest nucleos(t)ide analogues, due to its low hepatotoxicity and its lack of negative interference on treatment of HCV infection.

Comprehensive longitudinal analysis of hepatitis C virus (HCV)-specific T cell responses during acute HCV infection in the presence of existing HIV-1 infection

The aim of this study was to study the development of HCV-specific T cell immunity during acute HCV infection in the presence of an existing HIV-1 infection in four HIV-1 infected men having sex with men. A comprehensive analysis of HCV-specific T cell responses was performed at two time points during acute HCV infection using a T cell expansion assay with overlapping peptide pools spanning the entire HCV genome Three patients with (near) normal CD4+ T cell counts (range 400-970 x 10(6)/L) either resolved (n=1) or temporary suppressed HCV RNA. In contrast, one patient with low CD4+ T cell counts (330 x 10(6)/L), had sustained high HCV RNA levels. All four patients had low HCV-specific CD8+ T cell responses, and similar magnitudes of CD4+ T cell responses. Interestingly, individuals with resolved infection or temporary suppression of HCV-RNA had HCV-specific CD4+ T cell responses predominantly against nonstructural (NS) proteins. While the individual with high HCV RNA plasma concentrations had CD4+ T cell responses predominantly directed against Core. Our data show that an acute HCV infection in an HIV-1 infected person can be suppressed in the presence of HCV-specific CD4+ T cell response targeting non-structural proteins. However further research is needed in a larger group of patients to evaluate the role of HIV-1 on HCV-specific T cell responses in relation to outcome of acute HCV infection.

Polyfunctional HCV-specific T-cell responses are associated with effective control of HCV replication

HCV infection has a severe course of disease in HIV/HCV co-infection and in liver transplant recipients. However, the mechanisms involved remain unclear. Here, we evaluated functional profiles of HCV-specific T-cell responses in 86 HCV mono-infected patients, 48 HIV/HCV co-infected patients and 42 liver transplant recipients. IFN-gamma and IL-2 production and ability of CD4 and CD8 T cells to proliferate were assessed after stimulation with HCV-derived peptides. We observed that HCV-specific T-cell responses were polyfunctional in HCV mono-infected patients, with presence of proliferating single IL-2-, dual IL-2/IFN-gamma and single IFN-gamma-producing CD4+ and dual IL-2/IFN-gamma and single IFN-gamma-producing CD8+ cells. In contrast, HCV-specific T-cell responses had an effector profile in HIV/HCV co-infected individuals and liver transplant recipients with absence of single IL-2-producing HCV-specific CD4+ and dual IL-2/IFN-gamma-producing CD8+ T cells. In addition, HCV-specific proliferation of CD4+ and CD8+ T cells was severely impaired in HIV/HCV co-infected patients and liver transplant recipients. Importantly, "only effector" T-cell responses were associated with significantly higher HCV viral load and more severe liver fibrosis scores. Therefore, the present results suggest that immune-based mechanisms may contribute to explain the accelerated course of HCV infection in conditions of HIV-1 co-infection and liver transplantation.

Cellular and molecular interactions in coinfection with hepatitis C virus and human immunodeficiency virus

Coinfection with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) is associated with increased HCV replication and a more rapid progression to severe liver disease, including the development of cirrhosis and hepatocellular carcinoma. In this review, we discuss the current understanding of the pathogenesis of HCV/HIV coinfection and the cellular and molecular mechanisms associated with the accelerated course of liver disease. The strength and breadth of HCV-specific T-cell responses are reduced in HCV/HIV-coinfected patients compared with those infected with HCV alone, suggesting that the immunosuppression induced by HIV compromises immune responses to HCV. HCV is not directly cytopathic, but many of the pathological changes observed in the liver of infected patients are a direct result of the intrahepatic antiviral immune responses. Apoptosis also has a role in HCV-mediated liver damage through the induction of apoptotic pathways involving the host immune response and HCV viral proteins. This review summarises the evidence correlating the role of cell-mediated immune responses and apoptosis with liver disease progression in HCV/HIV-coinfected patients.

HIV-specific T-cells accumulate in the liver in HCV/HIV co-infection

Background and Aims

Hepatitis C Virus (HCV)-related liver disease progresses more rapidly in individuals co-infected with Human Immunodeficiency Virus-1 (HIV), although the underlying immunologic mechanisms are unknown. We examined whether HIV-specific T-cells are identified in the liver of HCV/HIV co-infected individuals and promote liver inflammation through bystander immune responses.

Methods

Ex-vivo intra-hepatic lymphocytes from HCV mono-infected and HCV/HIV co-infected individuals were assessed for immune responses to HIV and HCV antigens by polychromatic flow cytometry.

Results

HCV/HIV liver biopsies had similar frequencies of lymphocytes but lower percentages of CD4⁺ T-cells compared to HCV biopsies. In co-infection, intra-hepatic HIV-specific CD8⁺ and CD4⁺ T-cells producing IFN-γ and TNF-α were detected and were comparable in frequency to those that were HCV-specific. In co-infected individuals, viral-specific CD8⁺ T-cells produced more of the fibrogenic cytokine, TNF-α. In both mono- and co-infected individuals, intra-hepatic HCV-specific T-cells were poorly functional compared to HIV-specific T-cells. In co-infection, HAART was not associated with a reconstitution of intra-hepatic CD4⁺ T-cells and was associated with reduction in both HIV and HCV-specific intra-hepatic cytokine responses.

Conclusion

The accumulation of functional HIV-specific T-cells in the liver during HCV/HIV co-infection may represent a bystander role for HIV in inducing faster progression of liver disease.

Impaired hepatitis C virus (HCV)-specific effector CD8+ T cells undergo massive apoptosis in the peripheral blood during acute HCV infection and in the liver during the chronic phase of infection

A majority of patients infected with hepatitis C virus (HCV) do not sustain an effective T-cell response, and viremia persists. The mechanism leading to failure of the HCV-specific CD8(+) T-cell response in patients developing chronic infection is unclear. We investigated apoptosis susceptibility of HCV-specific CD8(+) T cells during the acute and chronic stages of infection. Although HCV-specific CD8(+) T cells in the blood during the acute phase of infection and in the liver during the chronic phase were highly activated and expressed an effector phenotype, the majority was undergoing apoptosis. In contrast, peripheral blood HCV-specific CD8(+) T cells during the chronic phase expressed a resting memory phenotype. Apoptosis susceptibility of HCV-specific CD8(+) T cells was associated with very high levels of programmed death-1 (PD-1) and low CD127 expression and with significant functional T-cell deficits. Further evaluation of the "death phase" of HCV-specific CD8(+) T cells during acute HCV infection showed that the majority of cells were dying by a process of cytokine withdrawal, mediated by activated caspase 9. Contraction during the acute phase occurred rapidly via this process despite the persistence of the virus. Remarkably, in the chronic phase of HCV infection, at the site of infection in the liver, a substantial frequency of caspase 9-mediated T-cell death was also present. This study highlights the importance of cytokine deprivation-mediated apoptosis with consequent down-modulation of the immune response to HCV during acute and chronic infections.

Strong EBV-specific CD8+ T-cell response in patients with early multiple sclerosis

Epstein-Barr virus (EBV) has been associated with multiple sclerosis (MS), however, most studies examining the relationship between the virus and the disease have been based on serologies, and if EBV is linked to MS, CD8+ T cells are likely to be involved as they are important both in MS pathogenesis and in controlling viruses. We hypothesized that valuable information on the link between MS and EBV would be ascertained from the study of frequency and activation levels of EBV-specific CD8+ T cells in different categories of MS patients and control subjects. We investigated EBV-specific cellular immune responses using proliferation and enzyme linked immunospot assays, and humoral immune responses by analysis of anti-EBV antibodies, in a cohort of 164 subjects, including 108 patients with different stages of MS, 35 with other neurological diseases and 21 healthy control subjects. Additionally, the cohort were all tested against cytomegalovirus (CMV), another neurotropic herpes virus not convincingly associated with MS, nor thought to be deleterious to the disease. We corrected all data for age using linear regression analysis over the total cohorts of EBV- and CMV-infected subjects. In the whole cohort, the rate of EBV and CMV infections were 99% and 51%, respectively. The frequency of IFN-gamma secreting EBV-specific CD8+ T cells in patients with clinically isolated syndrome (CIS) was significantly higher than that found in patients with relapsing-remitting MS (RR-MS), secondary-progressive MS, primary-progressive MS, patients with other neurological diseases and healthy controls. The shorter the interval between MS onset and our assays, the more intense was the EBV-specific CD8+ T-cell response. Confirming the above results, we found that EBV-specific CD8+ T-cell responses decreased in 12/13 patients with CIS followed prospectively for 1.0 +/- 0.2 years. In contrast, there was no difference between categories for EBV-specific CD4+ T cell, or for CMV-specific CD4+ and CD8+ T-cell responses. Anti-EBV-encoded nuclear antigen-1 (EBNA-1)-specific antibodies correlated with EBV-specific CD8+ T cells in patients with CIS and RR-MS. However, whereas EBV-specific CD8+ T cells were increased the most in early MS, EBNA-1-specific antibodies were increased in early as well as in progressive forms of MS. Our data show high levels of CD8+ T-cell activation against EBV--but not CMV--early in the course of MS, which support the hypothesis that EBV might be associated with the onset of this disease.

Disease progression in chronic hepatitis C: modifiable and nonmodifiable factors

The hepatic complications of chronic hepatitis C (CHC) usually occur only after progression to cirrhosis has taken place. Progression to cirrhosis, however, is extremely variable and depends on a broad set of host and viral factors that modify the rate at which fibrosis develops in a given individual. Despite their inherent limitations, studies of the natural history of CHC have identified several nonmodifiable factors associated with disease progression. These include age at acquisition of infection, sex, and race. More recent reports suggest important roles for host genetic polymorphisms and viral factors. Of greater immediate relevance to patients and their clinicians are the potentially modifiable factors, which include excessive alcohol consumption; smoking (tobacco and marijuana); insulin resistance; and coinfection with hepatitis B virus, human immunodeficiency virus type 1, or schistosomiasis. Unfortunately, to date, there are no reliable predictive models that can accurately estimate the risk of CHC disease progression.

CD4+ CD25+ regulatory T cells: a therapeutic target for liver diseases

BACKGROUND

Regulatory T cells (Tregs) have been shown to play an important role in maintaining peripheral immune homeostasis by suppressing autoreactive and allergen-specific T cells and turning off the immune response after the pathogen has been cleared. However, in certain situations Tregs can impair effective immunity to some pathogens and tumour cells.

OBJECTIVE

To review the role of Tregs in liver pathology and to assess the potential to enhance or inhibit their function as applied to the treatment of liver disease.

METHODS

The literature was reviewed using standard indexing terms and incorporating publications up to and including those published in 2007.

RESULTS/CONCLUSIONS

Tregs are therapeutic targets for modulation in autoimmune disease and may provide new opportunities for application to human liver conditions.

Low Current and Nadir CD4+ T-Cell Counts are Associated with Higher Hepatitis C virus RNA Levels in the Swiss HIV Cohort Study

Background

The aim of this study was to evaluate the effect of CD4+ T-cell counts and other characteristics of HIV-infected individuals on hepatitis C virus (HCV) RNA levels.

Methods

All HIV–HCV-coinfected Swiss HIV Cohort Study participants with available HCV RNA levels and concurrent CD4+ T-cell counts before starting HCV therapy were included. Potential predictors of HCV RNA levels were assessed by multivariate censored linear regression models that adjust for censored values.

Results

The study included 1,031 individuals. Low current and nadir CD4+ T-cell counts were significantly associated with higher HCV RNA levels ( P=0.004 and 0.001, respectively). In individuals with current CD4+ T-cell counts <200/μl, median HCV RNA levels (6.22 log10 IU/ml) were +0.14 and +0.24 log10 IU/ml higher than those with CD4+ T-cell counts of 200-500/μ l and >500/μl. Based on nadir CD4+ T-cell counts, median HCV RNA levels (6.12 log10 IU/ml) in individuals with <200/μl CD4+ T-cells were +0.06 and +0.44 log10 IU/ml higher than those with nadir T-cell counts of 200-500/μ l and >500/μ l. Median HCV RNA levels were also significantly associated with HCV genotype: lower values were associated with genotype 4 and higher values with genotype 2, as compared with genotype 1. Additional significant predictors of lower HCV RNA levels were female gender and HIV transmission through male homosexual contacts. In multivariate analyses, only CD4+ T-cell counts and HCV genotype remained significant predictors of HCV RNA levels.

Conclusions

Higher HCV RNA levels were associated with CD4+ T-cell depletion. This finding is in line with the crucial role of CD4+ T-cells in the control of HCV infection.

Intrahepatic mRNA expression in hepatitis C virus and HIV/hepatitis C virus co-infection: infiltrating cells, cytokines, and influence of HAART

OBJECTIVE

Liver disease is more progressive in HIV/hepatitis C virus (HCV) co-infection than in HCV infection alone. This accelerated pathogenesis is probably influenced by differences in the composition of infiltrating inflammatory cells and the local release of inflammatory and profibrogenic cytokines.

METHODS

Using quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) we studied intrahepatic messenger RNA levels of cytokines and cellular markers defining distinct subsets of inflammatory cells in liver biopsies from 33 HCV-mono-infected and 40 HIV/HCV-co-infected patients.

RESULTS

Despite their well preserved peripheral blood CD4 cell counts (median 598 cells/microl), HIV/HCV-co-infected patients displayed significantly lower CD4 mRNA levels than HCV-mono-infected patients, whereas increased mRNA levels of CD3epsilon, TCRalpha, CD8alpha and CD8beta suggested intrahepatic enrichment of CD8 T cells in HIV co-infection. Intrahepatic mRNA levels of the inflammatory cytokines interferon gamma (IFN-gamma), regulated upon activation, normal T-cell expressed and secreted (RANTES, CCL5), macrophage inflammatory protein 1 alpha (CCL3) and interferon-inducible protein 10 (CXCL10) were significantly higher in HIV-positive than in HIV-negative patients, whereas mRNA levels of the profibrogenic cytokines macrophage chemoattractant protein 1 (CCL2), secondary lymphochemokine (CCL21) and stroma-derived factor 1 (CXCL12) did not differ between the two groups. All changes were less pronounced in the subgroup of HIV-positive patients receiving antiretroviral treatment (HAART) than in untreated HIV-positive patients.

CONCLUSION

The accelerated liver disease observed in HIV/HCV-co-infected patients might reflect enhanced intrahepatic inflammatory responses rather than increased local transcription of directly profibrogenic cytokines.

Using evolutionary tools to refine the new hypervariable region 3 within the envelope 2 protein of hepatitis C virus

The envelope 2 protein of hepatitis C virus (HCV) presents three hypervariable regions, named HVR1, HVR2 and HVR3, in which the presence of antigenic sites has been described. Genetic variability in these regions may reflect the generation of escape mutants as a consequence of the immune response. Therefore, these regions would tend to accumulate amino acid changes along the infection process, an effect that could be accelerated by antiviral treatments. In this study, we have analyzed the E1-E2 region of 23 HCV patients non-responders to antiviral treatment, 7 of which were infected with subtype 1a, 15 with subtype 1b, and 1 with a new HCV-1 subtype, before and after 6 and/or 12 months of peg-interferon+ribavirin treatment. We have sequenced about 100 clones from each sample, analyzing a total of 4906 sequences. A detailed analysis of the evolutionary forces acting along the genome region studied confirmed the existence of the three hypervariable regions, characterized by significant changes in amino acid composition between samples taken at different times from the same patient and a high number of sites evolving under positive selection. Moreover, for the recently described HVR3, our results suggest that its location could be restricted to residues 434-450, instead of the originally postulated 431-466.

Suppression of acute anti-friend virus CD8+ T-cell responses by coinfection with lactate dehydrogenase-elevating virus

Friend virus (FV) and lactate dehydrogenase-elevating virus (LDV) are endemic mouse viruses that can cause long-term chronic infections in mice. We found that numerous mouse-passaged FV isolates also contained LDV and that coinfection with LDV delayed FV-specific CD8(+) T-cell responses during acute infection. While LDV did not alter the type of acute pathology induced by FV, which was severe splenomegaly caused by erythroproliferation, the immunosuppression mediated by LDV increased both the severity and the duration of FV infection. Compared to mice infected with FV alone, those coinfected with both FV and LDV had delayed CD8(+) T-cell responses, as measured by FV-specific tetramers. This delayed response accounted for the prolonged and exacerbated acute phase of FV infection. Suppression of FV-specific CD8(+) T-cell responses occurred not only in mice infected concomitantly with LDV but also in mice chronically infected with LDV 8 weeks prior to infection with FV. The LDV-induced suppression was not mediated by T regulatory cells, and no inhibition of the CD4(+) T-cell or antibody responses was observed. Considering that most human adults are carriers of chronically infectious viruses at the time of new virus insults and that coinfections with viruses such as human immunodeficiency virus and hepatitis C virus are currently epidemic, it is of great interest to determine how infection with one virus may impact host responses to a second infection. Coinfection of mice with LDV and FV provides a well-defined, natural host model for such studies.

HCV-HIV coinfection: simple messages from a complex disease

The authors discuss our current understanding of the immunopathogenesis of HCV-HIV coinfection.

[Adaptive cell immune response against the hepatitis C virus infection]

Hepatitis C virus (HCV) infects around 175 million people worldwide and is one of the leading causes of chronic liver disease. Less than one third of patients infected with HCV are able to spontaneously clear the virus during acute infection, while most patients evolve to chronic infection. Control of viral replication has been associated to the cellular component of the host immune response. It is not fully understood what distinguish a successful cellular immune response. An integral interpretation of the numerous experimental findings may allow a better understanding of the immune mechanisms involved in the inability of the immune system to successfully control chronic HCV infection.

Influence of HCV genotype and co-infection with human immunodeficiency virus on CD4(+) and CD8(+) T-cell responses to hepatitis C virus

The role of T-cells in clearance of hepatitis C virus (HCV) during acute infection is critical. The relevance of the immunological response in the control of HCV replication is less clear in chronic HCV infection. HCV-specific T-cell responses were examined in 92 interferon-naive individuals with chronic hepatitis C. A panel of 441 overlapping peptides spanning all expressed HCV proteins was used to measure HCV-specific T-cell responses, using flow cytometry after stimulating peripheral blood mononuclear cells (PBMCs) with different pools of these peptides. Most patients showed responses to at least one HCV protein, with NS5B for CD8(+) responses and E2 for CD4(+) responses identified most frequently. Both the prevalence and breadth of CD4(+) and CD8(+) responses were lower in co-infected patients, independently of the HCV genotype.

Evolution of T-cell Responses to Hepatitis C Virus (HCV) during Pegylated Interferon plus Ribavirin treatment in HCV-Monoinfected and in HCV/HIV-Coinfected Patients

Background

The role of T-cell immunity in chronic hepatitis C virus (HCV) infection remains controversial. As in HIV infection, virus replication could drive or be contained by T-cell immunity. We have examined the effect of HIV coinfection and of suppression of HCV replication with therapy on HCV-specific T-cell responses.

Patients and Methods

Thirty-five patients with chronic hepatitis C (17 coinfected with HIV) initiating anti-HCV therapy were analysed. HCV-specific responses were assessed at different time points using intracellular interferon-γ staining in response to a panel of overlapping peptides comprising E2, NS3, NS5a and NS5b HCV proteins.

Results

At baseline, HCV-specific responses were significantly lower in HIV-coinfected patients. At week 12 of therapy, CD8+ T-cell responses against all HCV proteins significantly decreased in HCV-monoinfected patients and this was maintained throughout the follow-up period. Although the same trend occurred in the HIV-coinfected group, differences were not significant. CD4+ T-cell responses against NS3 significantly diminished in the HCV-monoinfected group, whereas in coinfected patients CD4+ T-cell responses were low at baseline and did not experience any significant variation.

Conclusions

HCV-specific T-cell responses are lower in HIV-coinfected patients and vanish following complete suppression of HCV replication under successful HCV therapy, suggesting that they are dependent on continuous antigenic stimulation.

Study on the blood-borne virus co-infection and T lymphocyte subset among intravenous drug users

AIM: To investigate the features of various blood-borne virus infections and co-infection in intravenous drug users (IDUs), and to examine the correlation of T lymphocyte subsets with virus co-infection.

METHODS: Four hundred and six IDUs without any clinical manifestation of hepatitis and 102 healthy persons were enrolled in this study. HBV-DNA and HCV-RNA were detected by fluorescence quantitative PCR. HBsAg, HBeAg, anti-HBc, anti-HCV, HDV-Ag, anti-HGV, anti-HIV, and HCMV-IgM were assayed by enzyme-linked immunosorbent assay (ELISA) and immunochromatographic tests. The levels of Th1 and Th2 cytokines were measured by ELISA and radioactive immune assay (RIA). The T lymphocyte subpopulation was detected by using fluorescence immunoassay. The similar indices taken from the healthy persons served as controls.

RESULTS: The viral infection rate among IDUs was 36.45% for HBV, 69.7% for HCV, 47.3% for HIV, 2.22% for HDV, 1.97% for HGV, and 3.45% for HCMV. The co-infection rate of blood-borne virus was detected in 255 of 406 (62.81%) IDUs. More than 80% (161/192) of subjects infected with HIV were co-infected with the other viruses, such as HBV, HCV. In contrast, among the controls, the infection rate was 17.65% for HBV and 0% for the other viruses. Our investigation showed that there was a profound decrease in the proportion of CD4/CD8 and the percentage of CD3 and CD4, but not in the percentage of CD8. The levels of PHA-induced cytokines (IFN-γ and IL-4) and serum IL-2 were obviously decreased in IDUs. On the other hand, the level of serum IL-4 was increased. The level of IFN-γ and the percentage of CD4 were continuously decreased when the IDUs were infected with HIV or HIV co-infection. IDUs with HIV and HBV co-infection was 15.1% (29/192). Of those 29 IDU with HIV and HBV co-infection, 51.72% (15/29) and 37.93% (11/29) were HBV-DNA-positive and HBeAg-positive, respectively. But, among IDUs without HIV infection, only 1.68% (2/119) of cases were HBV-DNA-positive.

CONCLUSION: HCV, HBV and HIV infections are common in this population of IDU, leading to a high incidence of impaired Th1 cytokine levels and CD4 lymphocyte. IDUs with HIV and HBV/HCV co-infection have lower expression of Th1 cytokine with enhancement of the Th2 response. HIV may be causing HBV replication by decreasing Th1 function.

Defining target antigens for CD25+ FOXP3 + IFN-gamma- regulatory T cells in chronic hepatitis C virus infection

The mechanism behind the apparent lack of effective antiviral immune responses in chronic hepatitis C virus (HCV) patients is poorly understood. It remains unclear if natural regulatory T cells (Treg) contribute to the induction and maintenance of HCV persistence. We herein report for the first time that CD25(high)IFN-gamma(-)FOXP3(high) Tregs can be rapidly induced by culturing peripheral blood mononuclear cells (PBMCs) of HCV-positive patients with HCV protein-derived peptides. The HCV-specific Tregs, generally CD4(+)CD45RO(+), did not proliferate in response to HCV peptide and failed to produce interferon (IFN)-gamma, in distinct contrast to antiviral effector cells. Stimulation of healthy donor PBMCs with HCV peptides did not result in CD25 and FOXP3 upregulation above non-antigen background. To further investigate the antigen specificity of these potentially disease-associated natural Tregs, CD25(+) cells were isolated from PBMCs, labeled with carboxyfluorescein diacetate succinimidylester and added back to CD25-depleted PBMCs, and the co-cultures were then stimulated with individual peptides derived from the HCV core protein. We found that the actual peptide that can stimulate Treg varied between patients, but within any given subject only a small number of the peptides were able to stimulate Treg, suggesting the existence of dominant Treg epitopes. Although functional experiments for these peptides are ongoing in our laboratory, data presented here suggests that HCV-specific natural Tregs are abundant in infected individuals, in contrast to the extremely low frequency of anti-HCV effector T cells, supporting the view that natural Treg may be implicated in host immune tolerance during HCV infection.

Measurement of antigen specific immune responses: 2006 update

Measuring antigen-specific immune responses (MASIR) is essential for basic immunological research and in the clinical setting. Numerous techniques have been used and the recent years have witnessed a flourishing of flow cytometry based methods for the identification of antigen specific T cells, in addition to other methodologies. The second MASIR conference held in Santorini, Greece, from 14 to 18 June 2006 has been a forum for the discussion of methodological issues and for research or clinical applications of these techniques, as reviewed here. In addition to flow cytometry based techniques, other emerging techniques with different degrees of complexity can be applied. These novel methods are highly promising in numerous conditions to look for correlates of protection, to test responses to natural infections or to vaccination trials, to evaluate the immune status of immunocompromised patients and to monitor persistence and function of specific T cells administered as adoptive therapy.

Impaired hepatitis C virus-specific T cell responses and recurrent hepatitis C virus in HIV coinfection

BACKGROUND

Hepatitis C virus (HCV)-specific T cell responses are critical for spontaneous resolution of HCV viremia. Here we examined the effect of a lymphotropic virus, HIV-1, on the ability of coinfected patients to maintain spontaneous control of HCV infection.

METHODS AND FINDINGS

We measured T cell responsiveness by lymphoproliferation and interferon-gamma ELISPOT in a large cohort of HCV-infected individuals with and without HIV infection. Among 47 HCV/HIV-1-coinfected individuals, spontaneous control of HCV was associated with more frequent HCV-specific lymphoproliferative (LP) responses (35%) compared to coinfected persons who exhibited chronic HCV viremia (7%, p = 0.016), but less frequent compared to HCV controllers who were not HIV infected (86%, p = 0.003). Preservation of HCV-specific LP responses in coinfected individuals was associated with a higher nadir CD4 count (r(2) = 0.45, p < 0.001) and the presence and magnitude of the HCV-specific CD8(+) T cell interferon-gamma response (p = 0.0014). During long-term follow-up, recurrence of HCV viremia occurred in six of 25 coinfected individuals with prior control of HCV, but in 0 of 16 HIV-1-negative HCV controllers (p = 0.03, log rank test). In these six individuals with recurrent HCV viremia, the magnitude of HCV viremia following recurrence inversely correlated with the CD4 count at time of breakthrough (r = -0.94, p = 0.017).

CONCLUSIONS

These results indicate that HIV infection impairs the immune response to HCV-including in persons who have cleared HCV infection-and that HIV-1-infected individuals with spontaneous control of HCV remain at significant risk for a second episode of HCV viremia. These findings highlight the need for repeat viral RNA testing of apparent controllers of HCV infection in the setting of HIV-1 coinfection and provide a possible explanation for the higher rate of HCV persistence observed in this population.

Functional signatures of protective antiviral T-cell immunity in human virus infections

The most common human viruses have different abilities to establish persistent chronic infection. Virus-specific T-cell responses are critical in the control of virus replication and in the prevention of disease in chronic infection. A large number of phenotypic markers and a series of functions have been used to characterize virus-specific CD4+ and CD8+ T-cell responses, and these studies have shown great phenotypic and functional heterogeneity of the T-cell responses against different viruses. The heterogeneity of the T-cell response has been proposed to be specific to each virus. However, over the past 2 years, several studies have provided evidence that the phenotypic and functional heterogeneity of CD4+ and CD8+ T-cell responses is predominantly regulated by the levels of antigen load. The levels of antigen load modulate the phenotypic and functional patterns of the T-cell response within the same virus infection. Furthermore, the functional characterization of virus-specific CD4+ and CD8+ T-cell responses has identified signatures of protective antiviral immunity. Polyfunctional, i.e. interleukin-2 and interferon-gamma (IFN-gamma) secretion and proliferation, and not monofunctional, i.e. IFN-gamma secretion, CD4+ and CD8+ T-cell responses represent correlates of protective antiviral immunity in chronic virus infections.

Coinfection with hepatitis C virus increases lymphocyte apoptosis in HIV-infected patients

To test the role of hepatitis C virus (HCV) in CD4 cell depletion in human immunodeficiency virus (HIV)-coinfected patients, T cell apoptosis was measured by annexin V labeling in 31 HIV-infected and 30 HIV-HCV-coinfected patients who were not receiving antiretroviral therapy. Apoptosis in naive CD4(+) T cells and in naive and memory CD8(+) T cells was significantly higher in HIV-HCV-coinfected than in monoinfected patients.