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Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression.

ABSTRACT: Antimicrobial factors are efficient defense components of the innate immunity, playing a crucial role in the intestinal homeostasis and protection against pathogens. In this study, we report that upon infection of polarized human intestinal cells in vitro, virulent Shigella flexneri suppress transcription of several genes encoding antimicrobial cationic peptides, particularly the human beta-defensin hBD-3, which we show to be especially active against S. flexneri. This is an example of targeted survival strategy. We also identify the MxiE bacterial regulator, which controls a regulon encompassing a set of virulence plasmid-encoded effectors injected into host cells and regulating innate signaling, as being responsible for this dedicated regulatory process. In vivo, in a model of human intestinal xenotransplant, we confirm at the transcriptional and translational level, the presence of a dedicated MxiE-dependent system allowing S. flexneri to suppress expression of antimicrobial cationic peptides and promoting its deeper progression toward intestinal crypts. We demonstrate that this system is also able to down-regulate additional innate immunity genes, such as the chemokine CCL20 gene, leading to compromised recruitment of dendritic cells to the lamina propria of infected tissues. Thus, S. flexneri has developed a dedicated strategy to weaken the innate immunity to manage its survival and colonization ability in the intestine.

SUBMITTER: Sperandio B

PROVIDER: S-EPMC2373844 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression.

Sperandio Brice B Regnault Béatrice B Guo Jianhua J Zhang Zhi Z Stanley Samuel L SL Sansonetti Philippe J PJ Pédron Thierry T

The Journal of experimental medicine 20080421 5

Antimicrobial factors are efficient defense components of the innate immunity, playing a crucial role in the intestinal homeostasis and protection against pathogens. In this study, we report that upon infection of polarized human intestinal cells in vitro, virulent Shigella flexneri suppress transcription of several genes encoding antimicrobial cationic peptides, particularly the human beta-defensin hBD-3, which we show to be especially active against S. flexneri. This is an example of targeted ...[more]

PMID: 18426984

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Project description:Subversion of innate immunity by oncoviruses, such as human papillomavirus (HPV), favors carcinogenesis because the mechanism(s) of viral immune evasion can also hamper cancer immunosurveillance. Previously, we demonstrated that high-risk (hr) HPVs trigger simultaneous epigenetic silencing of multiple effectors of innate immunity to promote viral persistence. Here, we expand on those observations and show that the HPV E7 oncoprotein upregulates the H3K9-specific methyltransferase, whose action shuts down the host innate immune response. Specifically, we demonstrate that SUV39H1 contributes to chromatin repression at the promoter regions of the viral nucleic acid sensors RIG-I and cGAS and the adaptor molecule STING in HPV-transformed cells. Inhibition of SUV39H1 leads to transcriptional activation of these genes, especially RIG-I, followed by increased beta interferon (IFN-β) and IFN-λ1 production after poly(dA·dT) or RIG-I agonist M8 transfection. Collectively, our findings provide new evidence that the E7 oncoprotein plays a central role in dampening host innate immunity and raise the possibility that targeting the downstream effector SUV39H1 or the RIG-I pathway is a viable strategy to treat viral and neoplastic disease.IMPORTANCE High-risk HPVs are major viral human carcinogens responsible for approximately 5% of all human cancers. The growth of HPV-transformed cells depends on the ability of viral oncoproteins to manipulate a variety of cellular circuits, including those involved in innate immunity. Here, we show that one of these strategies relies on E7-mediated transcriptional activation of the chromatin repressor SUV39H1, which then promotes epigenetic silencing of RIG-I, cGAS, and STING genes, thereby shutting down interferon secretion in HPV-transformed cells. Pharmacological or genetic inhibition of SUV39H1 restored the innate response in HPV-transformed cells, mostly through activation of RIG-I signaling. We also show that IFN production upon transfection of poly(dA·dT) or the RIG-I agonist M8 predominantly occurs through RIG-I signaling. Altogether, the reversible nature of the modifications associated with E7-mediated SUV39H1 upregulation provides a rationale for the design of novel anticancer and antiviral therapies targeting these molecules.

Project description:UnlabelledDengue virus (DENV) is the most common mosquito-borne virus infecting humans and is currently a serious global health challenge. To establish infection in its host cells, DENV must subvert the production and/or antiviral effects of interferon (IFN). The aim of this study was to understand the mechanisms by which DENV suppresses IFN production. We determined that DENV NS4A interacts with mitochondrial antiviral signaling protein (MAVS), which was previously found to activate NF-κB and IFN regulatory factor 3 (IRF3), thus inducing type I IFN in the mitochondrion-associated endoplasmic reticulum membranes (MAMs). We further demonstrated that NS4A is associated with the N-terminal CARD-like (CL) domain and the C-terminal transmembrane (TM) domain of MAVS. This association prevented the binding of MAVS to RIG-I, resulting in the repression of RIG-I-induced IRF3 activation and, consequently, the abrogation of IFN production. Collectively, our findings illustrate a new molecular mechanism by which DENV evades the host immune system and suggest new targets for anti-DENV strategies.ImportanceType I interferon (IFN) constitutes the first line of host defense against invading viruses. To successfully establish infection, dengue virus (DENV) must counteract either the production or the function of IFN. The mechanism by which DENV suppresses IFN production is poorly understood and characterized. In this study, we demonstrate that the DENV NS4A protein plays an important role in suppressing interferon production through binding MAVS and disrupting the RIG-I-MAVS interaction in mitochondrion-associated endoplasmic reticulum membranes (MAMs). Our study reveals that MAVS is a novel host target of NS4A and provides a molecular mechanism for DENV evasion of the host innate immune response. These findings have important implications for understanding the pathogenesis of DENV and may provide new insights into using NS4A as a therapeutic and/or prevention target.

Dataset Information

Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression.

Publications

Virulent Shigella flexneri subverts the host innate immune response through manipulation of antimicrobial peptide gene expression.

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