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Bystander hyperactivation of preimmune CD8+ T cells in chronic HCV patients.

ABSTRACT: Chronic infection perturbs immune homeostasis. While prior studies have reported dysregulation of effector and memory cells, little is known about the effects on naïve T cell populations. We performed a cross-sectional study of chronic hepatitis C (cHCV) patients using tetramer-associated magnetic enrichment to study antigen-specific inexperienced CD8(+) T cells (i.e., tumor or unrelated virus-specific populations in tumor-free and sero-negative individuals). cHCV showed normal precursor frequencies, but increased proportions of memory-phenotype inexperienced cells, as compared to healthy donors or cured HCV patients. These observations could be explained by low surface expression of CD5, a negative regulator of TCR signaling. Accordingly, we demonstrated TCR hyperactivation and generation of potent CD8(+) T cell responses from the altered T cell repertoire of cHCV patients. In sum, we provide the first evidence that naïve CD8(+) T cells are dysregulated during cHCV infection, and establish a new mechanism of immune perturbation secondary to chronic infection.

SUBMITTER: Alanio C

PROVIDER: S-EPMC4752008 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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Bystander hyperactivation of preimmune CD8+ T cells in chronic HCV patients.

Alanio Cécile C Nicoli Francesco F Sultanik Philippe P Flecken Tobias T Perot Brieuc B Duffy Darragh D Bianchi Elisabetta E Lim Annick A Clave Emmanuel E van Buuren Marit M MM Schnuriger Aurélie A Johnsson Kerstin K Boussier Jeremy J Garbarg-Chenon Antoine A Bousquet Laurence L Mottez Estelle E Schumacher Ton N TN Toubert Antoine A Appay Victor V Heshmati Farhad F Thimme Robert R Pol Stanislas S Mallet Vincent V Albert Matthew L ML

eLife 20151114

Chronic infection perturbs immune homeostasis. While prior studies have reported dysregulation of effector and memory cells, little is known about the effects on naïve T cell populations. We performed a cross-sectional study of chronic hepatitis C (cHCV) patients using tetramer-associated magnetic enrichment to study antigen-specific inexperienced CD8(+) T cells (i.e., tumor or unrelated virus-specific populations in tumor-free and sero-negative individuals). cHCV showed normal precursor frequen ...[more]

PMID: 26568315

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Project description:HCV-specific CD8 cells are deeply exhausted in chronic hepatitis C and their function can only be partially corrected by modulation of up-regulated inhibitory pathways, suggesting a more complex molecular interplay. With the aim of identifying more suitable molecular targets to correct T cell dysfunction, we compared the transcriptome profile of HCV-specific CD8 cells of acute and chronic patients with the reference profile of HCV- and Flu-specific CD8 cells from patients able to resolve HBV infection spontaneously and from healthy subjects. First, the gene-expression profile of HCV-specific CD8 T cells from patients with chronically-evolving acute infection, that correspond to early but not established T exhausted cells, is consistent with a substantial functional impairment at the energetic and metabolic levels that leads to the accumulation of reactive oxygen species that contributes to the activation of stress sensor signaling pathways. A specific inhibition of the hyperactivated signaling downstream effectors elicits a functional metabolic T cell reconstitution in the majority of the tested patients early during HCV infection. Second, a predominant feature of late exhausted HCV specific T cells is a global downregulation of gene expression that affects multiple core processes, ranging from proteasome-dependent protein turnover to DNA repair, transcription, metabolism and cell cycle, that is presumably a consequence of precocious and dysregulated activity of histone methyltransferases (e.g. G9a and EZH2 HMTs). Third, a functional inhibition of HMTs leads to a T cell function reconstitution both as anti-viral cytokine production and as proliferative capacity and to a metabolic restoration specifically for late exhausted CD8 T cells with a strongly preferential effect on HCV-specific T cells. Virus-specific CD8+ T cells were isolated and sorted from early acute self-limited (5 patients), early chronic (8 patients), late resolved (4 patients), late chronic (7 patients) and from five healthy donors. RNA from sorted CD8+ T cells was processed, amplified, labeled, and hybridized to Agilent microarrays.

Project description:Background & aimsThe hepatitis D virus (HDV) causes the most severe form of chronic hepatitis, often progressing to cirrhosis within 5 to 10 years. There is no curative treatment, and the mechanisms underlying the accelerated liver disease progression are unknown.MethodsInnate and adaptive immune responses were studied in blood and liver of 24 patients infected with HDV and 30 uninfected controls by multiparameter flow cytometry in correlation with disease severity and stage.ResultsThe 2 main intrahepatic innate immune-cell populations, mucosal-associated invariant T cells and natural killer (NK) cells, were reduced in the livers of patients infected with HDV compared with those of uninfected controls but were more frequently activated in the liver compared with the blood. Most intrahepatic cluster of differentiation (CD) 8-positive (CD8+) T cells were memory cells or terminal effector memory cells, and most of the activated and degranulating (CD107a+) HDV-specific and total CD8+ T cells were liver-resident (CD69+C-X-C motif chemokine receptor 6+). Unsupervised analysis of flow cytometry data identified an activated, memory-like, tissue-resident HDV-specific CD8+ T-cell cluster with expression of innate-like NK protein 30 (NKp30) and NK group 2D (NKG2D) receptors. The size of this population correlated with liver enzyme activity (r = 1.0). NKp30 and NKG2D expression extended beyond the HDV-specific to the total intrahepatic CD8+ T-cell population, suggesting global bystander activation. This was supported by the correlations between (i) NKG2D expression with degranulation of intrahepatic CD8+ T cells, (ii) frequency of degranulating CD8+ T cells with liver enzyme activity and the aspartate aminotransferase-to-platelet ratio index score, and by the in vitro demonstration of cytokine-induced NKG2D-dependent cytotoxicity.ConclusionAntigen-nonspecific activation of liver-resident CD8+ T cells may contribute to inflammation and disease stage in HDV infection.

Dataset Information

Bystander hyperactivation of preimmune CD8+ T cells in chronic HCV patients.

Publications

Bystander hyperactivation of preimmune CD8+ T cells in chronic HCV patients.

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