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Priming of Antiviral CD8 T Cells without Effector Function by a Persistently Replicating Hepatitis C-Like Virus.

ABSTRACT: Immune-competent animal models for the hepatitis C virus (HCV) are nonexistent, impeding studies of host-virus interactions and vaccine development. Experimental infection of laboratory rats with a rodent hepacivirus isolated from Rattus norvegicus (RHV) is a promising surrogate model due to its recapitulation of HCV-like chronicity. However, several aspects of rat RHV infection remain unclear, for instance, how RHV evades host adaptive immunity to establish persistent infection. Here, we analyzed the induction, differentiation, and functionality of RHV-specific CD8 T cell responses that are essential for protection against viral persistence. Virus-specific CD8 T cells targeting dominant and subdominant major histocompatibility complex class I epitopes proliferated considerably in liver after RHV infection. These populations endured long term yet never acquired antiviral effector functions or selected for viral escape mutations. This was accompanied by the persistent upregulation of programmed cell death-1 and absent memory cell formation, consistent with a dysfunctional phenotype. Remarkably, transient suppression of RHV viremia with a direct-acting antiviral led to the priming of CD8 T cells with partial effector function, driving the selection of a viral escape variant. These data demonstrate an intrinsic abnormality within CD8 T cells primed by rat RHV infection, an effect that is governed at least partially by the magnitude of early virus replication. Thus, this model could be useful in investigating mechanisms of CD8 T cell subversion, leading to the persistence of hepatotropic pathogens such as HCV.IMPORTANCE Development of vaccines against hepatitis C virus (HCV), a major cause of cirrhosis and cancer, has been stymied by a lack of animal models. The recent discovery of an HCV-like rodent hepacivirus (RHV) enabled the development of such a model in rats. This platform recapitulates HCV hepatotropism and viral chronicity necessary for vaccine testing. Currently, there are few descriptions of RHV-specific responses and why they fail to prevent persistent infection in this model. Here, we show that RHV-specific CD8 T cells, while induced early at high magnitude, do not develop into functional effectors capable of controlling virus. This defect was partially alleviated by short-term treatment with an HCV antiviral. Thus, like HCV, RHV triggers dysfunction of virus-specific CD8 T cells that are vital for infection resolution. Additional study of this evasion strategy and how to mitigate it could enhance our understanding of hepatotropic viral infections and lead to improved vaccines and therapeutics.

SUBMITTER: Hartlage AS

PROVIDER: S-EPMC7199419 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Priming of Antiviral CD8 T Cells without Effector Function by a Persistently Replicating Hepatitis C-Like Virus.

Hartlage Alex S AS Walker Christopher M CM Kapoor Amit A

Journal of virology 20200504 10

Immune-competent animal models for the hepatitis C virus (HCV) are nonexistent, impeding studies of host-virus interactions and vaccine development. Experimental infection of laboratory rats with a rodent hepacivirus isolated from <i>Rattus norvegicus</i> (RHV) is a promising surrogate model due to its recapitulation of HCV-like chronicity. However, several aspects of rat RHV infection remain unclear, for instance, how RHV evades host adaptive immunity to establish persistent infection. Here, we ...[more]

PMID: 32102885

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Project description:Chronic viral hepatitis after infection with hepatotropic viruses like hepatitis B virus (HBV) affects 300 million persons worldwide, which as the result of chronic immune-mediated hepatic inflammation cause liver cirrhosis and cancer being responsible for 800.000 deaths per year3. Chronic viral hepatitis is maintained by failure of the host´s immune response to control viral infection, but the mechanisms for this inability of virus-specific CD8 T cells to eliminate HBV-infected hepatocytes remain unclear. Here, we demonstrate that during persistent experimental infection with hepatotropic viruses and HBV replication in hepatocytes all virus-specific CD8 T cells present in the liver expressed the tissue-residency markers CXCR6 and CD69. However, RNAseq analysis revealed that CXCR6+CD8 T cells during persistent hepatotropic infection were retained in the liver because of antigen-recognition rather than a transcriptional tissue-residency program, in contrast to canonical liver-resident memory CXCR6+CD8 T cells emerging after resolved infection. Whereas during persistent infection with a model virus like lymphocytic choriomeningitis virus with broad tissue and cell tropism exhausted CD8 T cells show graded loss of effector functions, hepatic virus-specific CXCR6+CD8 T cells during persistent infection with hepatotropic viruses were blinded and completely non-responsive to stimulation in absence of a canonical tox exhaustion signature. Rather, in blinded liver CXCR6+CD8 T cells, transcription factor network analysis revealed Crem, the cAMP-responsive-element-modulator, as the only transcription factor discreetly active in CD8 T cells with complete loss of effector function during persistent hepatotropic infection. Similarly, single cell RNA-sequencing of peripheral blood HBcore-specific CD8 T cells from chronic hepatitis B patients also revealed enhanced CREM activity. Notably, knock-out of the inhibitory CREM/ICER gene in T cells failed to rescue protective T cell immunity during persistent infection with hepatotropic viruses pointing towards post-translational mechanisms relevant for enhanced Crem activity and loss of effector function. Indeed, T cell receptor-associated signalling was blocked in blinded antigen-specific CXCR6+CD8 T cells, that in situ during persistent hepatotropic infection were in close proximity to liver sinusoidal endothelial cells producing high amounts of cAMP-inducing prostanoids. Inhibitory cAMP/PKA/CSK activity increased CREM activity and disconnected CXCR6+CD8 T cells from activation signalling through the T cell receptor. Thus, enhanced CREM expression identifies blinded liver CXCR6+CD8 T cells, but loss of effector functions is caused by post-translational prevention of signalling, which identifies novel molecular targets for immune monitoring and immune therapy of chronic hepatitis B.

Dataset Information

Priming of Antiviral CD8 T Cells without Effector Function by a Persistently Replicating Hepatitis C-Like Virus.

Publications

Priming of Antiviral CD8 T Cells without Effector Function by a Persistently Replicating Hepatitis C-Like Virus.

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