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Host cell invasion by Lassa virus

English title Host cell invasion by Lassa virus
Applicant Kunz Stefan
Number 132844
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 01.01.2011 - 31.12.2013
Approved amount 375'000.00
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Keywords (9)

hemorrhagic fever; Lassa fever; Receptor; Cell entry; Dendritic cells; Arenavirus; Cellular transport; Immune evasion; Immune cells

Lay Summary (English)

Lead
Lay summary
Old World arenaviruses include the prototypic lymphocytic choriomeningitis virus (LCMV) and the highly pathogenic Lassa virus (LASV) that causes a severe hemorrhagic fever in humans and infects several thousand individuals per year in Western Africa. There is currently no vaccine available and therapeutic intervention is limited resulting in a mortality of 15-30% among hospitalized Lassa fever patients. Considering the number of people affected and the unaddressed need for better therapeutics, Lassa fever is arguably one of the most neglected tropical diseases. Cell entry of a virus is the first step of every virus infection and represents a promising target for therapeutic intervention. To invade host cell, viruses can hijack the cellular machinery that is normally responsible for the transport of nutrients and cellular cargo like membrane lipids and proteins. We and others have shown that LCMV and LASV attach to a cellular receptor, followed by internalization via a novel and unusual pathway. In this project we will investigate the largely unknown molecular mechanisms of cell entry of LASV and LCMV with the goal to identify host cell factors involved. In our first aim we will study the role of cellular proteins that are involved in the host cells' transport mechanisms to identify factors hijacked by the virus. Since cellular transport mechanisms are subject to tight regulation, we will identify signaling molecules required for viral entry. Among the first targets of LASV are antigen-presenting cells of the host's immune system, in particular dendritic cells. Infection of this crucial immune-regulatory cell population is a key event early in disease. Instead of being taken up and presented as a foreign antigen, the virus can escape from immune detection and degradation and establish a productive infection in dendritic cells, perturbing their function. Using a combination of state-of-the art methods, we will investigate how viruses can evade from the mechanisms of pathogen recognition in dendritic cells and how they manage to invade the cell without being degraded by the antigen-processing machinery. The results of our studies will illuminate basic aspects of the host cell interaction of these important human pathogens. Cellular factors essential for host cell invasion discovered in our studies will then be evaluated as novel targets for therapeutic intervention.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Role of DC-SIGN in Lassa virus entry into human dendritic cells.
Goncalves Ana-Rita, Moraz Marie-Laurence, Pasquato Antonella, Helenius Ari, Lozach Pierre-Yves, Kunz Stefan (2013), Role of DC-SIGN in Lassa virus entry into human dendritic cells., in Journal of virology, 87(21), 11504-15.
Binding of Lassa virus perturbs extracellular matrix-induced signal transduction via dystroglycan.
Rojek Jillian M, Moraz Marie-Laurence, Pythoud Christelle, Rothenberger Sylvia, Van der Goot F Gisou, Campbell Kevin P, Kunz Stefan (2012), Binding of Lassa virus perturbs extracellular matrix-induced signal transduction via dystroglycan., in Cellular microbiology, 14(7), 1122-34.
Old world arenaviruses enter the host cell via the multivesicular body and depend on the endosomal sorting complex required for transport.
Pasqual Giulia, Rojek Jillian M, Masin Mark, Chatton Jean-Yves, Kunz Stefan (2011), Old world arenaviruses enter the host cell via the multivesicular body and depend on the endosomal sorting complex required for transport., in PLoS pathogens, 7(9), 1002232-1002232.
Cell entry of Lassa virus induces tyrosine phosphorylation of dystroglycan.
Moraz Marie-Laurence, Pythoud Christelle, Turk Rolf, Rothenberger Sylvia, Pasquato Antonella, Campbell Kevin P, Kunz Stefan, Cell entry of Lassa virus induces tyrosine phosphorylation of dystroglycan., in Cellular microbiology.

Collaboration

Group / person Country
Types of collaboration
Howard Hughes Medical Institute United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Scripps Research Institute La Jolla United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
EPFL Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Institutional Seminar, Department of Molecular Physiology & Biophysics, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa Individual talk 04.09.2013 Iowa City, United States of America Kunz Stefan;
Institutional Seminar “Friday@Noon” Institute of Virology, Vetsuisse, Zürich Individual talk 01.03.2013 Zurich, Switzerland Kunz Stefan;
Institutional Seminar TWINCORE Hannover Individual talk 02.11.2012 Hannover, Germany Kunz Stefan;
“Schauinsland” Conference in Viral Hepatitis Individual talk 31.05.2012 Freiburg, Germany Kunz Stefan;
Institutional Seminar Institute de Recherches Cliniques de Montréal Individual talk 22.03.2012 Montreal, Canada Kunz Stefan;
Gordon Conference Viruses and Cells Poster 06.06.2011 Il Ciocco Ilalien, Italy Kunz Stefan;


Associated projects

Number Title Start Funding scheme
120250 Targeting the processing of arenavirus glycoprotein for anti-viral therapy 01.04.2008 Project funding
143754 Immunoengineering a synthetic vaccine against emerging human pathogenic viruses 01.10.2012 Interdisciplinary projects
135536 Targeting the processing of arenavirus glycoprotein for anti-viral therapy 01.04.2011 Project funding
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 arenavirus Lassa virus (LASV) is endemic to West Africa from Senegal to Cameroon and infects several hundred thousand individuals each year with thousands of deaths. There is currently no vaccine available and therapeutic intervention is limited resulting in a mortality of 15-30% among hospitalized Lassa fever patients. Considering the number of people affected and the unaddressed need for better therapeutics, Lassa fever is arguably one of the most neglected tropical diseases. Virus cell entry is the first step of every viral infection and represents a promising target for therapeutic intervention that allows blocking the pathogen before it can take control over the host cell for replication. Upon attachment to its cellular receptor a-dystroglycan (a-DG), LASV enters the cell by an unusual route that is independent of clathrin- and caveolin and delivers the virus to acidified endosomes bypassing classical routes of incoming vesicular trafficking to the early endosome. Our present project aims at the characterization of the cellular mechanisms of LASV entry and the identification of cellular proteins and signaling pathways involved. In our preliminary studies, we uncovered that LASV entry into prototypic human cells involves sorting in the host cells multivesicular body (MVB) involving the endosomal sorting complex required for transport (ESCRT). These studies gave the first hints that LASV may enter cells via a pathway that may be linked to the degradation of its cellular receptor. We hypothesize that the use of an unusual pathway of endocytosis may allow LASV to avoid detection by some of the pathogen recognition receptors of the host cell and to escape the host cell’s innate anti-viral defenses. We will test this hypothesis by designing variants of the LASV receptor that will target the virus to clathrin-mediated endocytosis and the classical routes of incoming endosomal trafficking. In this proof-of-concept study we will infect cells expressing these mutant receptors with LASV and examine activation of the host cell’s innate anti-viral defense. In a next phase, we aim at the identification of the cellular signaling pathways involved LASV host cell entry. To this end, we will use a two-pronged approach: 1) monitoring the activation of cellular kinases during LASV host cell attachment and entry, and 2) a focussed RNAi silencing screening of known and putative protein and lipid kinases that have been implicated endocytosis. Hits will be validated using firmly established methods to measure virus cell entry. Cellular kinases specifically required for pathogen entry would represent promising targets for therapeutic intervention. Early and preferred targets of LASV are antigen-presenting cells of the patient’s immune system, in particular dendritic cells (DC). Instead of being recognized and presented as a foreign antigen by DC, LASV subverts the normal mechanisms of pathogen recognition and establishes a productive infection that blocks the ability of DC to activate T cells. Considering their crucial role in the development of an anti-viral immune response, the mechanisms by which LASV invades DCs is of particular interest to understand viral pathogenesis. Human DC express not only the ubiquitous LASV receptor a-DG, but also pathogen recognition receptors of the C-type lectin family, in particular DC-SIGN and the mannose receptor used by other viruses to invade DC. Using well-characterized cell culture systems for human DC combined with established biochemical and cell biological assays, we will define the roles these receptors in LASV infection of DCs. In contrast to other cells, human DC have specialized mechanisms of pathogen internalization, in particular phagocytosis and constitutively active forms of macropinocytosis. The role of these mechanisms in LASV infection of DC is currently unknown. We will use specific pharmacological inhibitors and well-characterized dominant negative (DN) mutants of regulatory proteins to characterize the endocytotic pathway(s) that LASV uses to productively infect human DC. These studies will illuminate how LASV avoids the machinery of antigen processing to establish productive infection.
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