Selective expansion of myeloid and NK cells in humanized mice yields human-like vaccine responses

Mice engrafted with components of a human immune system have become widely-used models for studying aspects of human immunity and disease. However, a defined methodology to objectively measure and compare the quality of the human immune response in different models is lacking. Here, by taking advantage of the highly immunogenic live-attenuated yellow fever virus vaccine YFV-17D, we provide an in-depth comparison of immune responses in human vaccinees, conventional humanized mice, and second generation humanized mice. We demonstrate that selective expansion of human myeloid and natural killer cells promotes transcriptomic responses akin to those of human vaccinees. These enhanced transcriptomic profiles correlate with the development of an antigen-specific cellular and humoral response to YFV-17D. Altogether, our approach provides a robust scoring of the quality of the human immune response in humanized mice and highlights a rational path towards developing better pre-clinical models for studying the human immune response and disease.National Institute of General Medical Sciences (U.S.) (Award T32GM007753)Searle Scholars ProgramArnold and Mabel Beckman Foundation (Young Investigator Program)National Institutes of Health (U.S.) (1DP2OD020839)National Institutes of Health (U.S.) (5U24AI118672)National Institutes of Health (U.S.) (1U54CA217377)National Institutes of Health (U.S.) (1R33CA202820)National Institutes of Health (U.S.) (2U19AI089992)National Institutes of Health (U.S.) (21R01HL134539)National Institutes of Health (U.S.) (2RM1HG006193)National Institutes of Health (U.S.) (2R01HL095791)National Institutes of Health (U.S.) (P01AI039671)Bill & Melinda Gates Foundation (OPP1139972

Up-regulation of the ATP-binding cassette transporter A1 inhibits hepatitis C virus infection.

International audienceHepatitis C virus (HCV) establishes infection using host lipid metabolism pathways that are thus considered potential targets for indirect anti-HCV strategies. HCV enters the cell via clathrin-dependent endocytosis, interacting with several receptors, and virus-cell fusion, which depends on acidic pH and the integrity of cholesterol-rich domains of the hepatocyte membrane. The ATP-binding Cassette Transporter A1 (ABCA1) mediates cholesterol efflux from hepatocytes to extracellular Apolipoprotein A1 and moves cholesterol within cell membranes. Furthermore, it generates high-density lipoprotein (HDL) particles. HDL protects against arteriosclerosis and cardiovascular disease. We show that the up-regulation of ABCA1 gene expression and its cholesterol efflux function in Huh7.5 hepatoma cells, using the liver X receptor (LXR) agonist GW3965, impairs HCV infection and decreases levels of virus produced. ABCA1-stimulation inhibited HCV cell entry, acting on virus-host cell fusion, but had no impact on virus attachment, replication, or assembly/secretion. It did not affect infectivity or properties of virus particles produced. Silencing of the ABCA1 gene and reduction of the specific cholesterol efflux function counteracted the inhibitory effect of the GW3965 on HCV infection, providing evidence for a key role of ABCA1 in this process. Impaired virus-cell entry correlated with the reorganisation of cholesterol-rich membrane microdomains (lipid rafts). The inhibitory effect could be reversed by an exogenous cholesterol supply, indicating that restriction of HCV infection was induced by changes of cholesterol content/distribution in membrane regions essential for virus-cell fusion. Stimulation of ABCA1 expression by GW3965 inhibited HCV infection of both human primary hepatocytes and isolated human liver slices. This study reveals that pharmacological stimulation of the ABCA1-dependent cholesterol efflux pathway disrupts membrane cholesterol homeostasis, leading to the inhibition of virus-cell fusion and thus HCV cell entry. Therefore besides other beneficial roles, ABCA1 might represent a potential target for HCV therapy

Formation option "Conférence" !

Florian Douam, doctorant à l’ENS de Lyon et président du bureau exécutif de l’association ConférENS, revient sur l’histoire de cette association étudiante qui met en place chaque année une dizaine de conférences sur des sujets scientifiques, sociétaux ou littéraires. Il dévoile les coulisses de cette belle organisation, revient sur les motivations des participants et précise l’intérêt de la démarche. Une initiative à forte valeur ajoutée pour les étudiants !   Un manque à combler… Encore en M..

Pourquoi la science a plus que jamais besoin du web - Par Florian Douam, doctorant en biologie

Florian Douam propose un retour d'expérience, suite à la soirée “Médiation culturelle des sciences sur le web”, organisée par le service Science & Société de l’Université de Lyon à l’Atelier des Médias, dans le cadre des off du www2012, en partenariat avec le collectif Le Grand Mix, et faisant suite à la journée de rencontre et de réflexion organisée en mars 2011 (vidéos en ligne). Vous pouvez retrouver en ligne un compte-rendu multimédia (Storify) de cette soirée, effectué par l’équipe de Kn..

Les réseaux de co-évolution au sein des protéines E1 et E2 du Virus de l'Hépatite C révèlent leurs dialogues fonctionnels et proposent de nouvelles stratégies thérapeutiques

Hepatitis C Virus (HCV) infects more than 170 million people worldwide but no vaccine is available yet. HCV entry may represent a promising target for therapies and is mediated by two envelope glycoproteins, E1 and E2, assembled as heterodimer onto the virus surface. However, how E1 and E2 dialog, structurally rearrange and act together during these steps remain poorly defined. In this work, we aimed to clarify the interrelation of E1E2 during virus entry, thus opening ways to potential new therapeutic strategies. We first investigated whether a strong genetic divergence between E1E2 heterodimers may highlight distinct functions. We observed that B-cell derived E1E2 were specialized for B-cell infection, suggesting that new functions can emerge from the E1E2 conformational plasticity. In a second approach, we identified a conserved dialog between E1 and the domain III of E2 that was critical for virus binding and fusion. Moreover, a computational model predicted a strong co-evolution between E1 and E2 as well as potential structural rearrangements, suggesting that HCV E2 is likely a fusion protein able to fold over via its domain III through the mediation of E1. Altogether, these different works highlight that E1 and E2 are involved in complex dialogs that regulate the heterodimer folding and functions, suggesting that E1E2 heterodimer is more likely a single functional protein entity than an association of two proteins with specific functions.Le Virus de l’Hépatite C (VHC) infecte 170 millions de personnes dans le monde mais aucun vaccin n’est encore disponible. Le processus d’entrée du VHC dans les hépatocytes représente une cible prometteuse pour le développement de stratégie thérapeutique et est finement régulé par un nombre par les deux glycoprotéines d’envelope du VHC, E1 et E2, assemblé sous la forme d’un hétérodimère incorporé à la surface des particules virales. Cependant, comment E1 et E2 dialoguent, modifient leurs conformations et se coordonnent mutuellement au cours de l’entrée reste encore à être définit. Dans ce travail, nous avons souhaité clarifier l’interrelation entre E1 and E2 au cours de l’entrée afin d’ouvrir la voie à de potentiels stratégies thérapeutiques. Nous avons tout d’abord examiné si une importante divergence génétique entre des hétérodimères E1E2 pouvait être liée à l’existence de fonctions particulières. Nous avons observé une spécialisation des E1E2 isolé des Lymphocytes B pour l’infection de ces mêmes cellules mais pas des hépatocytes, suggérant que de nouvelles fonctions peuvent émerger de la plasticité conformationel de E1E2. Dans un second temps, nous sommes parvenus à identifier un dialogue conservé entre E1 et le domaine III de E2 (E2 DIII), critique pour les processus d’attachement et de fusion du VHC. Nous avons aussi montré grâce à une approche bio-informatique l’existence d’une co-évolution très importante entre E1 et E2. Cette approche a également prédit de potentiel changement de conformations au sein de l’hétérodimère, suggérant que E2 est sans doute une protéine de fusion capable de se replier sur elle-même via le repliement de son domaine III et l’aide de E1. Ainsi, ces différents travaux soulignent l’implication de E1 et E2 au sein de dialogues fins et complexes, qui régulent à la fois les conformations et les fonctions de l’hétérodimère. Ainsi, cela suggère que l’hétérodimère E1E2 représente plutôt une unité fonctionnelle et structurale unique, plutôt que l’association de deux protéines aux fonctions distinctes

Pourquoi la science a plus que jamais besoin du web - Par Florian Douam, doctorant en biologie

Florian Douam propose un retour d'expérience, suite à la soirée “Médiation culturelle des sciences sur le web”, organisée par le service Science & Société de l’Université de Lyon à l’Atelier des Médias, dans le cadre des off du www2012, en partenariat avec le collectif Le Grand Mix, et faisant suite à la journée de rencontre et de réflexion organisée en mars 2011 (vidéos en ligne). Vous pouvez retrouver en ligne un compte-rendu multimédia (Storify) de cette soirée, effectué par l’équipe de Kn..

The use of humanized mice for studies of viral pathogenesis and immunity.

Humanized mice, i.e. animals engrafted with human tissues and/or expressing human genes, have been instrumental in improving our understanding of the pathogenesis and immunological processes that define some of the most challenging human-tropic viruses. In particular, mice engrafted with components of a human immune system (HIS) offer unprecedented opportunities for mechanistic studies of human immune responses to infection. Here, we provide a brief overview of the current panel of HIS mouse models available and cite recent examples of how such humanized animals have been used to study immune responses and pathogenesis elicited by human-tropic viruses. Finally, we will outline some of the challenges that lay ahead and strategies to improve and refine humanized mice with the goal of more accurately recapitulating human immune responses to viral infection

Proteomic approaches to analyzing hepatitis C virus biology

Hepatitis C virus (HCV) is a major cause of liver disease worldwide. Acute infection often progresses to chronicity resulting frequently in fibrosis, cirrhosis, and in rare cases, in the development of hepatocellular carcinoma (HCC). Although HCV has proven to be an arduous object of research and has raised important technical challenges, several experimental models have been developed all over the last two decades in order to improve our understanding of the virus life cycle, pathogenesis and virus-host interactions. The recent development of direct acting-agents (DAAs), leading to considerable progress in treatment of patients, represents the direct outcomes of these achievements. Proteomic approaches have been of critical help to shed light on several aspect of the HCV biology such as virion composition, viral replication, and virus assembly and to unveil diagnostic or prognostic markers of HCV-induced liver disease. Here, we review how proteomic approaches have led to improve our understanding of HCV life cycle and liver disease, thus highlighting the relevance of these approaches for studying the complex interactions between other challenging human viral pathogens and their host

Yellow Fever Virus: Knowledge Gaps Impeding the Fight Against an Old Foe.

Yellow fever (YF) was one of the most dangerous infectious diseases of the 18th and 19th centuries, resulting in mass casualties in Africa and the Americas. The etiologic agent is yellow fever virus (YFV) and its live-attenuated form, YFV-17D, remains one of the most potent vaccines ever developed. During the first half of the 20th century, vaccination combined with mosquito control eradicated YFV transmission in urban areas. However, the recent 2016–2018 outbreaks in areas with historically low or no YFV activity have raised serious concerns for an estimated 400– 500 million unvaccinated people who now live in at-risk areas. Once a forgotten disease, we highlight here that YF still represents a very real threat to human health and economies. As many gaps remain in our understanding of how YFV interacts with the human host and causes disease, there is an urgent need to address these knowledge gaps and propel YFV research forward

Humanized Mice for Live-Attenuated Vaccine Research: From Unmet Potential to New Promises

Live-attenuated vaccines (LAV) represent one of the most important medical innovations in human history. In the past three centuries, LAV have saved hundreds of millions of lives, and will continue to do so for many decades to come. Interestingly, the most successful LAVs, such as the smallpox vaccine, the measles vaccine, and the yellow fever vaccine, have been isolated and/or developed in a purely empirical manner without any understanding of the immunological mechanisms they trigger. Today, the mechanisms governing potent LAV immunogenicity and long-term induced protective immunity continue to be elusive, and therefore hamper the rational design of innovative vaccine strategies. A serious roadblock to understanding LAV-induced immunity has been the lack of suitable and cost-effective animal models that can accurately mimic human immune responses. In the last two decades, human-immune system mice (HIS mice), i.e., mice engrafted with components of the human immune system, have been instrumental in investigating the life-cycle and immune responses to multiple human-tropic pathogens. However, their use in LAV research has remained limited. Here, we discuss the strong potential of LAVs as tools to enhance our understanding of human immunity and review the past, current and future contributions of HIS mice to this endeavor