Liver monocytes and kupffer cells remain transcriptionally distinct during chronic viral infection

Due to the scarcity of immunocompetent animal models for chronic viral hepatitis, little is known about the role of the innate intrahepatic immune system during viral replication in the liver. These insights are however fundamental for the understanding of the inappropriate adaptive immune responses during the chronic phase of the infection. We apply the Lymphocytic Choriomenigitis Virus (LCMV) clone 13 mouse model to examine chronic virus-host interactions of Kupffer cells (KC) and infiltrating monocytes (IM) in an infected liver. LCMV infection induced overt cli

Cytosolic 5'-triphosphate ended viral leader transcript of measles virus as activator of the RIG I-mediated interferon response.

International audienceBACKGROUND: Double stranded RNA (dsRNA) is widely accepted as an RNA motif recognized as a danger signal by the cellular sentries. However, the biology of non-segmented negative strand RNA viruses, or Mononegavirales, is hardly compatible with the production of such dsRNA. METHODOLOGY AND PRINCIPAL FINDINGS: During measles virus infection, the IFN-beta gene transcription was found to be paralleled by the virus transcription, but not by the virus replication. Since the expression of every individual viral mRNA failed to activate the IFN-beta gene, we postulated the involvement of the leader RNA, which is a small not capped and not polyadenylated RNA firstly transcribed by Mononegavirales. The measles virus leader RNA, synthesized both in vitro and in vivo, was efficient in inducing the IFN-beta expression, provided that it was delivered into the cytosol as a 5'-trisphosphate ended RNA. The use of a human cell line expressing a debilitated RIG-I molecule, together with overexpression studies of wild type RIG-I, showed that the IFN-beta induction by virus infection or by leader RNA required RIG-I to be functional. RIG-I binds to leader RNA independently from being 5-trisphosphate ended; while a point mutant, Q299A, predicted to establish contacts with the RNA, fails to bind to leader RNA. Since the 5'-triphosphate is required for optimal RIG-I activation but not for leader RNA binding, our data support that RIG-I is activated upon recognition of the 5'-triphosphate RNA end. CONCLUSIONS/SIGNIFICANCE: RIG-I is proposed to recognize Mononegavirales transcription, which occurs in the cytosol, while scanning cytosolic RNAs, and to trigger an IFN response when encountering a free 5'-triphosphate RNA resulting from a mislocated transcription activity, which is therefore considered as the hallmark of a foreign invader

Induction et amplification de la réponse Interferon par le virus de la rougeole

Le virus de la rougeole induit une réponse interféron par la cellule-hôte. J'ai étudié son déclenchement, sachant qu'il repose sur la transcription de l'ARN leader codé à l'extrémité 3' du génome viral. Cet ARN est détecté par RIG-I, une ARN hélicase à boîte DExD/H. J'ai contribué à montrer que le leader est reconnu par son extrémité 5'-triphosphate libre dans le cytoplasme. RIG-I semble cependant capable de lier tous les ARN. Avec Sonia Longhi, j'ai montré que la Q299 est impliquée dans la liaison des ARN par RIG-I.J'ai alors étudié l'impact de la fusion intercellulaire, caractéristique du VR, sur la réponse IFN. La fusion entraîne l'amplification de cette réponse, indépendamment des voies associées au récepteur IFNAR, mais dépendant d'une induction soutenue dans le temps. L'amplification varie aussi selon le type cellulaire, la souche virale et des facteurs individuels.J'ai enfin observé que les syncytia sont des entités métaboliquement actives, mobiles, vivant >= 60 h post formationLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Cellular receptors, differentiation and endocytosis requirements are key factors for type I IFN response by human epithelial, conventional and plasmacytoid dendritic infected cells by measles virus

While the antiviral response during measles virus (MeV) infection is documented, the contribution of the hosting cell type to the type I interferon (IFN-α/β) response is still not clearly established. Here, we report that a signature heterogeneity of the IFN-α/β response according to the cell type. The MeV tropism dictated by the expression of appropriate cellular receptor appeared to be crucial for epithelial cells. For conventional DCs (cDCs), the maturation state played a prominent role. In response to both wild type MeV isolates and laboratory/vaccine strains, immature cDCs produced higher levels of IFN-α than mature cDCs, despite the reduced expression levels of both CD46 and CD150 receptors by the former ones. While in epithelial cells and cDCs the MeV transcription was required to activate the IFN-α/β response, plasmacytoid DCs (pDCs) rapidly produced large amounts of IFN-α mostly independently of the viral infection cycle. This argues for a significant contribution of pDCs in response to MeV infection and/or vaccination

The engagement of activating FcgammaRs inhibits primate lentivirus replication in human macrophages.

We previously reported that the stimulation of monocyte-derived macrophages (MDM) by plate-bound i.v. Igs inhibits HIV-1 replication. In this study, we show that IgG immune complexes also suppress HIV-1 replication in MDMs and that activating receptors for the Fc portion of IgG-FcgammaRI, FcgammaRIIA, and FcgammaRIII-are responsible for the inhibition. MDM stimulation through FcgammaRs induces activation signals and the secretion of HIV-1 modulatory cytokines, such as M-CSF, TNF-alpha, and macrophage-derived chemokine. However, none of these cytokines contribute to HIV-1 suppression. HIV-1 entry and postintegration steps of viral replication are not affected, whereas reduced levels of reverse transcription products and of integrated proviruses, as determined by real-time PCR analysis, account for the suppression of HIV-1 gene expression in FcgammaR-activated MDMs. We found that FcgammaR-dependent activation of MDMs also inhibits the replication of HIV-2, SIVmac, and SIVagm, suggesting a common control mechanism for primate immunodeficiency lentiviruses in activated macrophages

Liver Monocytes and Kupffer Cells Remain Transcriptionally Distinct during Chronic Viral Infection

<div><p>Due to the scarcity of immunocompetent animal models for chronic viral hepatitis, little is known about the role of the innate intrahepatic immune system during viral replication in the liver. These insights are however fundamental for the understanding of the inappropriate adaptive immune responses during the chronic phase of the infection. We apply the Lymphocytic Choriomenigitis Virus (LCMV) clone 13 mouse model to examine chronic virus-host interactions of Kupffer cells (KC) and infiltrating monocytes (IM) in an infected liver. LCMV infection induced overt clinical hepatitis, with rise in ALT and serum cytokines, and increased intrahepatic F4/80 expression. Despite ongoing viral replication, whole liver transcriptome showed baseline expression levels of inflammatory cytokines, interferons, and interferon induced genes during the chronic infection phase. Transcriptome analyses of sorted KC and IMs using NanoString technology revealed two unique phenotypes with only minimal overlap. At the chronic viral infection phase, KC showed no increased transcription of activation markers <i>Cd80</i> and <i>Cd86</i>, but an increased expression of genes related to antigen presentation, whereas monocytes were more activated and expressed higher levels of <i>Tnf</i> transcripts. Although both KCs and intrahepatic IM share the surface markers F4/80 and CD11b, their transcriptomes point towards distinctive roles during virus-induced chronic hepatitis.</p></div

Clinical Scoring of LCMV infected mice.

<p>Clinical Scoring of LCMV infected mice.</p