Accumulation of dysfunctional effector CD8+T cells in the liver of patients with chronic HCV infection
National Institute for Infectious Diseases IRCCS L. Spallanzani, Via Portuense 292, 00149 Rome, Italy. Journal of Hepatology
(Impact Factor: 11.34).
04/2006; 44(3):475-83. DOI: 10.1016/j.jhep.2005.10.023
Hepatitis C virus (HCV) causes a chronic infection that can lead to fibrosis and carcinoma. Immune responses mediated by cytotoxic T lymphocytes (CTLs) could be involved in viral clearance or persistence, and therefore in determining the course of the disease.
Intrahepatic and peripheral blood CD8+T cells were obtained from 32 HCV-chronically infected patients and analysed by flow-cytometry for surface markers of differentiation, IFNgamma and TNFalpha production, degranulation capacity and perforin content, after CD3 triggering. Results were compared with those obtained from 13 patients with a non-viral liver disease.
Intrahepatic CD8+T cells of HCV-infected patients, despite their phenotype of pre-terminally and terminally differentiated effectors (CCR7-CD45RA-/+), are poorly responsive to T cell receptor (TCR)-mediated stimulation compared with those obtained from uninfected subjects. This defect correlates with the severity of fibrosis, is more pronounced in patients with ALT<1.5xN than with ALT>1.5xNU/ml, and is not evident after mitogen stimulation.
The present study describes the accumulation of hypo-responsive CD8+T cells in the liver of patients with chronic HCV infection. Understanding the mechanisms underlying this impairment may be helpful in the design of innovative strategies for HCV treatment.
Available from: Donald D. Anthony
- "Dolganiuc et al found that mDC induced more Tregs in HCV infected individuals, which could hamper T helper responses . Nisii et al found an accumulation of dysfunctional CD8+ T cells in livers of subjects with chronic HCV suggesting global T cell defects may be present . Defects in CD4+ helper T cells have not been reported. "
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ABSTRACT: Individuals with chronic HCV infection have impaired response to vaccine, though the etiology remains to be elucidated. Dendritic cells (DC) and monocytes (MN) provide antigen uptake, processing, presentation, and costimulatory functions necessary to achieve optimal immune responses. The integrity of antigen processing and presentation function within these antigen presenting cells (APC) in the setting of HCV infection has been unclear. We used a novel T cell hybridoma system that specifically measures MHC-II antigen processing and presentation function of human APC. Results demonstrate MHC-II antigen processing and presentation function is preserved in both myeloid DC (mDC) and MN in the peripheral blood of chronically HCV-infected individuals, and indicates that an alteration in this function does not likely underlie the defective HCV-infected host response to vaccination.
Available from: Sang-Jun Ha
- "However, the efficacy of such strategies has so far been disappointing (6–9). Recent work suggests that the decreased proliferative potential of virus-specific CD8+ T cells generated during chronic infection, and high viral load at the time of vaccination might explain the inefficient responses to therapeutic vaccination (6, 8, 10–12). Thus, it is important to develop a therapeutic vaccine strategy to more effectively boost endogenous T cell responses to control persistent viral infections. "
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ABSTRACT: Therapeutic vaccination is a potentially promising strategy to enhance T cell immunity and viral control in chronically infected individuals. However, therapeutic vaccination approaches have fallen short of expectations, and effective boosting of antiviral T cell responses has not always been observed. One of the principal reasons for the limited success of therapeutic vaccination is that virus-specific T cells become functionally exhausted during chronic infections. We now provide a novel strategy for enhancing the efficacy of therapeutic vaccines. In this study, we show that blocking programmed death (PD)-1/PD-L1 inhibitory signals on exhausted CD8(+) T cells, in combination with therapeutic vaccination, synergistically enhances functional CD8(+) T cell responses and improves viral control in mice chronically infected with lymphocytic choriomeningitis virus. This combinatorial therapeutic vaccination was effective even in the absence of CD4(+) T cell help. Thus, our study defines a potent new approach to augment the efficacy of therapeutic vaccination by blocking negative signals. Such an approach may have broad applications in developing treatment strategies for chronic infections in general, and perhaps also for tumors.
Available from: jid.oxfordjournals.org
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ABSTRACT: Polychromatic flow-cytometric assays were used to analyze paired intrahepatic and peripheral lymphocyte samples from 37 patients
with chronic hepatitis C. Compared with peripheral cells, intrahepatic T cells were selectively enriched with CD45RO+ memory T cells but had a lower percentage of CD4+ T cells expressing the differentiation markers CD27 and CD28. The percentage of intrahepatic CD45RO+ and CD28+ T cells correlated with the degree of liver inflammation, which suggests that memory T cells at relatively early stages of
differentiation are directly involved in liver inflammation. Despite their memory phenotype, intrahepatic T cells were defective
in proliferation capability, produced less interferon-γ in response to stimulation by T cell receptor, and contained less
perforin but expressed higher levels of Fas and Fas ligand, compared with their counterparts in peripheral blood. The distinct
characteristics of intrahepatic T cells suggest that they play an important role in the immunopathogenesis of chronic hepatitis
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