Tobias Boettler

T Cells with a CD4+CD25+ Regulatory Phenotype Suppress In Vitro Proliferation of Virus-Specific CD8+ T Cells during Chronic Hepatitis C Virus Infection

ABSTRACT Chronic hepatitis C virus (HCV) infection is associated with impaired proliferative, cytokine, and cytotoxic effector functions of HCV-specific CD8+ T cells that probably contribute significantly to viral persistence. Here, we investigated the potential role of T cells with a CD4+CD25+ regulatory phenotype in suppressing virus-specific CD8+ T-cell proliferation during chronic HCV infection. In vitro depletion studies and coculture experiments revealed that peptide specific proliferation as well as gamma interferon production of HCV-specific CD8+ T cells were inhibited by CD4+CD25+ T cells. This inhibition was dose dependent, required direct cell-cell contact, and was independent of interleukin-10 and transforming growth factor beta. Interestingly, the T-cell-mediated suppression in chronically HCV-infected patients was not restricted to HCV-specific CD8+ T cells but also to influenza virus-specific CD8+ T cells. Importantly, CD4+CD25+ T cells from persons recovered from HCV infection and from healthy blood donors exhibited significantly less suppressor activity. Thus, the inhibition of virus-specific CD8+ T-cell proliferation was enhanced in chronically HCV-infected patients. This was associated with a higher frequency of circulating CD4+CD25+ cells observed in this patient group. Taken together, our results suggest that chronic HCV infection leads to the expansion of CD4+CD25+ T cells that are able to suppress CD8+ T-cell responses to different viral antigens. Our results further suggest that CD4+CD25+ T cells may contribute to viral persistence in chronically HCV-infected patients and may be a target for immunotherapy of chronic hepatitis C.

Expression of the Interleukin-7 Receptor Alpha Chain (CD127) on Virus-Specific CD8+ T Cells Identifies Functionally and Phenotypically Defined Memory T Cells during Acute Resolving Hepatitis B Virus Infection

ABSTRACT Virus-specific CD8+ T cells play a central role in the outcome of several viral infections, including hepatitis B virus (HBV) infection. A key feature of virus-specific CD8+ T cells is the development of memory. The mechanisms resulting in the establishment of T-cell memory are still only poorly understood. It has been suggested that T-cell memory may depend on the survival of virus-specific CD8+ T cells in the contraction phase. Indeed, a population of effector cells that express high levels of the interleukin-7 receptor alpha chain (CD127) as the precursors of memory CD8+ T cells has recently been identified in mice. However, very little information is currently available about the kinetics of CD127 expression in an acute resolving viral infection in humans and its association with disease pathogenesis, viral load, and functional and phenotypical T-cell characteristics. To address these important issues, we analyzed the HBV-specific CD8+ T-cell response longitudinally in a cohort of six patients with acute HBV infection who spontaneously cleared the virus. We observed the emergence of CD127 expression on antigen-specific CD8+ memory T cells during the course of infection. Importantly, the up-regulation of CD127 correlated phenotypically with a loss of CD38 and PD-1 expression and acquisition of CCR7 expression: functionally with an enhanced proliferative capacity and clinically with the decline in serum alanine aminotransferase levels and viral clearance. These results suggest that the expression of CD127 is a marker for the development of functionally and phenotypically defined antigen-specific CD8+ memory T cells in cleared human viral infections.

Comprehensive analysis of the α‐fetoprotein‐specific CD8+ T cell responses in patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide, with a poor prognosis and limited therapeutic options. Therefore, the development of novel therapeutic strategies is of high priority. α‐Fetoprotein (AFP) is overexpressed in the majority of HCCs. Priming of immune responses against AFP results in significant protective antitumoral T cell responses in the mouse model. Little information is available about the hierarchy, breadth, frequency, and peripheral versus intrahepatic distribution of AFP‐specific CD8+ T cell responses in patients with HCC. To address these important issues we comprehensively analyzed CD8+ T cell responses against full‐length AFP in peripheral blood, tumor liver tissue, and nontumor liver tissue from patients with HCC using overlapping AFP peptides. The AFP‐specific CD8+ T cell response was also tested in peripheral blood and liver from patients chronically infected with hepatitis C virus (HCV) and compared to the HCV‐specific CD8+ T cell response. The majority of patients with HCC showed AFP‐specific responses, with many responses directed against previously unreported epitopes. These responses were primarily detectable in the HCC tissue and mainly targeted the C‐terminus of AFP. Interestingly, AFP‐specific T cells were not only found in patients with HCC but also in patients with chronic HCV infection, other liver diseases, and less frequently in healthy subjects. Conclusion: In patients with HCC, a high frequency of AFP‐specific CD8+ T cells directed against different epitopes suggest that AFP has a strong and broad immunogenicity. Further, CD8+ T cells specific for the self‐antigen AFP are present in the normal T cell repertoire and are not centrally or peripherally deleted. Our results provide support for strategies to boost AFP‐specific CD8+ T cell responses in patients with HCC but also demonstrate a diversity of immune responses that may be needed for protection. (HEPATOLOGY 2008;48:1821‐1833.)

Adaptive immune responses to hepatitis C virus: from viral immunobiology to a vaccine

Abstract Hepatitis C virus (HCV) causes chronic infection in approximately two-thirds of cases, leading to chronic hepatitis, liver cirrhosis, liver disease, liver failure, and hepatocellular carcinoma in a substantial proportion of the 170 million HCV-infected individuals worldwide. It is generally accepted that the cellular immune response plays the most important role in determining the outcome of HCV infection. First, vigorous, multispecific and sustained CD4+ and CD8+ T-cell responses are associated with viral clearance. Second, depletion studies in chimpanzees, the only other host of HCV besides humans, have shown that both CD4+ and CD8+ T-cells are required for virus elimination. Third, the hosts human leukocyte antigen alleles, which restrict the repertoire of CD4+ and CD8+ T-cell responses, influence the outcome of infection. Of note, protective immunity has been demonstrated in population-based studies, as well as in experimentally infected chimpanzees. Thus, a detailed understanding of the mechanisms contributing to the failure of the antiviral immune response should allow successful development of prophylactic and therapeutic vaccination strategies.

Combined effects of the PNPLA3 rs738409, TM6SF2 rs58542926, and MBOAT7 rs641738 variants on NAFLD severity: a multicenter biopsy-based study

The PNPLA3 p.I148M, TM6SF2 p.E167K, and MBOAT7 rs641738 variants represent genetic risk factors for nonalcoholic fatty liver disease (NAFLD). Here we investigate if these polymorphisms modulate both steatosis and fibrosis in patients with NAFLD. We recruited 515 patients with NAFLD (age 16–88 years, 280 female patients). Liver biopsies were performed in 320 patients. PCR-based assays were used to genotype the PNPLA3, TM6SF2, and MBOAT7 variants. Carriers of the PNPLA3 and TM6SF2 risk alleles showed increased serum aspartate aminotransferase and alanine transaminase activities (P < 0.05). The PNPLA3 genotype was associated with steatosis grades S2–S3 (P < 0.001) and fibrosis stages F2–F4 (P < 0.001). The TM6SF2 genotype was associated with steatosis (P = 0.003) but not with fibrosis (P > 0.05). The MBOAT7 variant was solely associated with increased fibrosis (P = 0.046). In the multivariate model, variants PNPLA3 (P = 0.004) and TM6SF2 (P = 0.038) were associated with steatosis. Fibrosis stages were affected by the PNPLA3 (P = 0.042) and MBOAT7 (P = 0.021) but not by the TM6SF2 polymorphism (P > 0.05). The PNPLA3, TM6SF2, and MBOAT7 variants are associated with increased liver injury. The TM6SF2 variant seems to modulate predominantly hepatic fat accumulation, whereas the MBOAT7 polymorphism is linked to fibrosis. The PNPLA3 polymorphism confers risk of both increased steatosis and fibrosis.

Virus-specific CD4+ T Cells Have Functional and Phenotypic Characteristics of Follicular T-helper Cells in Patients With Acute and Chronic HCV Infections.

BACKGROUND & AIMS Follicular T-helper (Tfh) cells contribute to pathogen-specific antibody responses by providing maturation signals to B cells. In mice with viral infections, virus-specific Tfh cells expand and are required to contain the infection. However, less is known about human virus-specific Tfh cells or their functions during infection. We investigated whether virus-specific CD4+ T cells from patients with hepatitis C virus (HCV) infection had phenotypic or functional features of Tfh cells and contribute to the production of HCV-specific antibodies. METHODS We collected blood samples from patients with acute and chronic HCV infection and healthy individuals (controls). We performed MHC class II tetramer analyses, assays to detect intracellular cytokines in response to HCV exposure, and analyses to quantify HCV-specific antibodies. In addition, we collected liver tissues from patients with chronic HCV infection or nonviral liver disease to analyze markers of Tfh cells. RESULTS HCV-specific CD4+ T cells from patients with acute HCV infection expressed markers of Tfh cells and secreted interleukin 21 in response to HCV exposure. Longitudinal analyses of HCV-specific T-cell responses and antibody responses showed an association between expression of inducible T-cell co-stimulator and induction of virus-specific antibodies in patients with acute HCV infection. Markers of Tfh cells were barely detectable in the peripheral blood samples from patients with chronic HCV infection, but were detected in liver tissues. CONCLUSIONS Virus-specific Tfh cells can be detected in blood samples from patients with acute HCV infection; inducible T-cell co-stimulator expression correlates with production of HCV-specific antibodies. In patients with chronic infection, Tfh cells seem to disappear from the blood but are detectable in the liver.

Bridging basic science and clinical research: the EASL Monothematic Conference on Translational Research in Viral Hepatitis.

The EASL Monothematic Conference on Translational Research in Viral Hepatitis brought together a group of leading scientists and clinicians working on both, basic and clinical aspects of viral hepatitis, thereby building bridges from bench to bedside. This report recapitulates the presentations and discussions at the conference held in Lyon, France on November 29-30, 2013. In recent years, great advances have been made in the field of viral hepatitis, particularly in hepatitis C virus (HCV) infection. The identification of IL28B genetic polymorphisms as a major determinant for spontaneous and treatment-induced HCV clearance was a seminal discovery. Currently, hepatologists are at the doorstep of even greater advances, with the advent of a wealth of directly acting antivirals (DAAs) against HCV. Indeed, promising results have accumulated over the last months and few years, showing sustained virological response (SVR) rates of up to 100% with interferon-free DAA combination therapies. Thus, less than 25 years after its identification, HCV infection may soon be curable in the vast majority of patients, highlighting the great success of HCV research over the last decades. However, viral hepatitis and its clinical complications such as liver cirrhosis and hepatocellular carcinoma (HCC) remain major global challenges. New therapeutic strategies to tackle hepatitis B virus (HBV) and hepatitis D virus (HDV) infection are needed, as current therapies have undeniable limitations. Nucleoside/nucleotide analogues (NUC) can efficiently control HBV replication and reduce or even reverse liver damage. However, these drugs have to be given for indefinite periods in most patients to maintain virological and biochemical responses. Although sustained responses off treatment can be achieved by treatment with (pegylated) interferon-α, only about 10-30% of patients effectively resolve chronic hepatitis B. It was the goal of this conference to review the progress made over the last years in chronic viral hepatitis research and to identify key questions that need to be addressed in order to close the gap between basic and clinical research and to develop novel preventive and treatment approaches for this most common cause of liver cirrhosis and HCC.

Procedural and shunt-related complications and mortality of the transjugular intrahepatic portosystemic shunt (TIPSS).

The implantation of a transjugular intrahepatic portosystemic shunt (TIPSS) is a complex angiographic procedure performed in patients with end‐stage liver disease. Numerous case reports and narrative reviews have been published so far; however, studies systematically investigating procedural and shunt‐related complications are lacking.

Treatment with proton pump inhibitors is associated with increased mortality in patients with pyogenic liver abscess

Proton pump inhibitors (PPI) are often used in patients with gastro‐esophageal reflux and peptic ulcer disease. A higher risk for infectious diseases and for pyogenic liver abscess has been reported in patients with prolonged PPI intake. Although many patients have ongoing PPI treatment after diagnosis of liver abscess, there are no data available that focus on the prognostic impact of PPI treatment in these patients.

Antiviral Therapy in Hepatitis B Virus-Associated Liver Cirrhosis

Background: Chronic hepatitis B virus (HBV) infection is a major risk factor for the development of liver cirrhosis and hepatocellular carcinoma (HCC). Key Messages: In patients with advanced liver fibrosis or liver cirrhosis, antiviral therapy is mandatory to slow down, halt or reverse disease progression and possibly reduce the risk of HCC development. As in patients without advanced fibrosis, PEG-interferon and nucleoside/nucleotide analogues (NUCs) are available for antiviral therapy. NUC therapy should be performed indefinitely as the rates of HBs-Ag loss are low. Entecavir or tenofovir should be preferred due to their strong antiviral potency and their high barrier to resistance. PEG-interferon therapy can be administered to patients with compensated liver disease but should not be offered to patients with signs of hepatic decompensation. Conclusions: Antiviral therapy in chronic HBV infection can reduce liver fibrosis and even revert overt cirrhosis. Whether it also reduces the risk of HCC development in cirrhotic patients remains elusive and might vary in different countries and ethnicities.