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Host cell invasion by Lassa virus

English title Host cell invasion by Lassa virus
Applicant Kunz Stefan
Number 170108
Funding scheme Project funding
Research institution Institut de Microbiologie - CHUV Faculté de Biologie et Médecine Université de Lausanne
Institution of higher education University of Lausanne - LA
Main discipline Medical Microbiology
Start/End 01.01.2017 - 30.11.2020
Approved amount 474'000.00
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Keywords (6)

Receptor; Signaling; Cell entry; Lassa fever; hemorrhagic fever; Uncoating

Lay Summary (German)

Lead
Lassavirus ist endemisch in Westafrika und verursacht ein schweres virales hämorrhagisches Fieber mit hoher Sterberate. Lassafieber ist ein grosses Gesundheitsproblem in betroffenen Regionen da derzeit weder eine zugelassene Impfung noch eine effiziente anti-virale Therapie existieren. Die Entwicklung neuer wirksamer Medikamente gegen Lassavirus ist deshalb von grosser Wichtigkeit.
Lay summary

Der erste und wichtigste Schritt jeder viralen Infektion ist der Eintritt des Virus in die Wirtszelle. Diese Etappe definiert nicht nur das Wirtsspektrum des Virus sondern stellt auch ein wichtiges Ziel therapeutischer Intervention dar. Als obligatorische intrazelluläre Parasiten sind Viren dabei weitgehend von Faktoren der Wirtszelle abhängig. In unserem Projekt werden wir eine Kombination von modernen biochemischen und mikroskopischen Techniken einsetzen um zelluläre Faktoren zu identifizieren welche für den Eintritt des Lassavirus in menschliche Zellen notwendig sind. In einer ersten Etappe unseres Projektes haben wir zelluläre Rezeptoren identifiziert, welche das Andocken an die Zelloberfläche ermöglichen und die Mechanismen ergründet durch die das Virus daraufhin internalisiert wird. Als nächste Schritte werden wir die zellulären Signale identifizieren, welche in die Aufnahme und den intrazellulären Transport des Virus involviert sind. In einer folgenden Etappe werden wir dann die Mechanismen untersuchen welche es dem Virus ermöglichen seine genetische Information ins Innere der Wirtszelle freizusetzen. Die Resultate unseres Projektes werden aufzeigen mittels welcher Mechanismen das hochpathogene Lassavirus menschliche Zellen effizient infizieren kann und zu einem tieferen Verständnis dieser wichtigen Krankheit beitragen. Die Verwertbarkeit unserer Resultate für die Entwicklung neuer wirksamer antiviraler Medikamente würde einen Nutzen für die gesamte Gesellschaft darstellen.    

Direct link to Lay Summary Last update: 25.10.2016

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
183376 Biocontained Confocal Microscopy Platform Lausanne University Hospital 01.10.2019 R'EQUIP
160780 Viral Plasticity Underlying Tropism And Pathogenesis/ Innate Immune Evasion Of Emerging Viruses 01.11.2015 Sinergia
149746 Host cell invasion by Lassa virus 01.01.2014 Project funding
149746 Host cell invasion by Lassa virus 01.01.2014 Project funding

Abstract

The Old World arenavirus Lassa (LASV) is an emerging pathogen that causes a severe viral hemorrhagic fever with high mortality in humans. The virus is currently endemic in large parts of Western Africa where it causes several hundred thousand infections per year with thousands of deaths. Human LASV infection is caused mainly by transmission from infected rodent hosts via aerosols of excreta or by contaminated food. Due to its transmissibility via aerosol and high lethality, LASV has been characterized as a Category A agent by the Centers of Disease Control and Prevention. The lack of a licensed vaccine and limited treatment options make the development of novel therapeutic strategies against LASV an urgent needed. Our project investigates host cell attachment and entry by LASV that represent the first and most fundamental steps of infection. Our goal is an in-depth understanding of the mechanisms underlying LASV host cell invasion and the identification of crucial cellular factors that will then be evaluated as possible targets for therapeutic intervention. Previous work on the present project uncovered that binding of the virus to its major cellular receptor dystroglycan (DG) induces receptor-mediated signaling, phosphorylation of the receptor, and changes in DG’s interaction with cellular proteins. Upon receptor engagement, we found that the virus enters the host cell via an unusual pathway of macropinocytosis that causes only minimal perturbation of the host cell and critically depends on cellular kinases. In the present renewal, we will continue and extend this research. In a first aim, we will combine high-resolution confocal light microscopy with cell biological approaches to track the virus from its internalization to the site of fusion at the level of the late endosome. These studies will reveal if productive virus entry requires maturation of macropinosomes and identify novel viral entry factors. Using “shotgun” proteomics combined with sensitive label-free quantification, we started to unravel the complex “interactome” of the LASV receptor DG and assessed virus-induced changes in receptor-protein interactions. In our project prolongation, we will add a complementary approach, applying highly sensitive phosphoproteomics to identify signaling pathways that are modulated by the virus during cell entry. This analysis will identify virus-induced receptor signaling that may serve as a “knock on the door” to promote viral entry, but could also “re-program” cellular pathways to facilitate post-entry steps of viral multiplication. Candidate kinases and “virus-responsive” phosphoproteins will be integrated with other data on LASV entry to develop a “LASV entry map” of cellular factors required for productive host cell invasion. Kinases at key positions within this map will be evaluated as “druggable” targets for therapeutic anti-viral intervention, Viral entry and uncoating are considered distinct processes that are however closely linked. In our last aim, we will start to investigate the largely unknown mechanisms of arenavirus uncoating. As all viruses, arenaviruses face the “assembly-disassembly” problem: the virus particle needs to assemble during budding to form a stable extracellular virion, but has to rapidly disassemble upon host cell entry to release the viral ribonucleoprotein into the cytosol. Inspired by recent ground-breaking work on different viruses, we will try to identify cellular factors that facilitate release of the arenaviral ribonucleoprotein from the capsid upon fusion and try to define the viral “unpacking signals”. These studies will shed light on a largely unknown aspect of arenavirus host cell invasion and reveal possible convergent evolution of uncoating mechanisms between different viral families. Together, these studies will provide a deeper understanding of the fundamental mechanisms underlying LASV host cell invasion, which is a key determinant for the host range, tissue tropism, and disease potential of the virus. Cellular factors involved may provide novel drug targets that will then be evaluated for therapeutic intervention.
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