rologie i - European Congress of Virology

5 th European Congress of VirologyWednesday 11 th September 2013,16h15 – 18h15WORKSHOP 3: “INNATE IMMUNITY AGAINST VIRUSES”KEYNOTE:Chairpersons: Denis GERLIER (Paris, FRANCE) &Maria-Carla SALEH (Paris, FRANCE)Room Gratte-Ciel 1, 2, 3Manipulation of autophagy by measles virusMathias FAURECentre de Recherche International en Infectiologie (CIRI), INSERMU1111, UCBL-1, CNRS UMR5308, ENS-Lyon, FRANCEMacroautophagy, referred to as autophagy, is a lysosomal catabolicpathway, which allows the sequestration of portions of the cytoplasmwithin vesicles called autophagosomes, leading to their ultimate degradationwithin autolysosomes. In mammalian cells, regulation of autophagyinvolves dozens of proteins including those of the ATG (AuTophaGyrelated)family. Essential for the maintenance of cellular homeostasis,autophagy is also a cell-autonomous defense mechanism that allows thetargeting of pathogens, including viruses, towards lysosomes. In addition,autophagy may potentiate innate and adaptive antiviral immune responses.However, several viruses have evolved strategies in order to escape orhijack autophagy to facilitate their replication.Infection with measles virus leads to a paradox: despite the developmentof an effective immune response, which eliminates the virus and leads tothe development of a lifelong immunity, immunosuppression occurs. Wehave shown that CD46, the receptor of the attenuated strains of measlesvirus, is directly connected to autophagy via a specific molecular pathway.Furthermore, we found that, during infection, two other pathways lead tothe induction of autophagy, which are both independent of CD46 and fromeach other. These pathways contribute to the ability of measles virus toexploit the autophagic process in order to replicate, through the delay ofvirus-induced cell death. Thus, subtle relationships between measles virusand autophagy could contribute to either control the infection or to increaseinfectivity.The antiviral pathogen recognition receptor RIG I is known to bind nakeddsRNA containing a triphosphate (ppp) 5 ′ terminus. It remained unclear,however, whether RIG I can also recognize RNAs packaged into nucleocapsids,the first viral structure to enter the host cell. We show that incomingnucleocapsids of viruses containing a 5 ′ ppp dsRNA “panhandle” structuretrigger an antiviral signaling cascade that commences with RIG I and terminateswith activation of the transcription factor IRF 3. Independent ofmammalian cofactors or of viral polymerase activity, RIG I interacted withthe viral nucleocapsids, underwent a conformational switch, and homooligomerized. Enzymatic probing, as well as super resolution GSDIMmicroscopy (Ground State Depletion Microscopy followed by IndividualMolecule return) suggest that RIG I associates with the 5 ′ ppp panhandlestructure on the viral nucleocapsids.These results define the entry of nucleocapsids into the cytoplasm as thefirst RIG I sensitive step in infection, and establish viral nucleocapsids witha5 ′ ppp dsRNA panhandle as a pathogen associated molecular pattern forRIG I (Weber et al., Cell Host and Microbe, 2013).REF 002Sensing of infected cells in absence of virus particles by plasmacytoiddendritic cells is inhibited by the ribonuclease Erns of classical swinefever virusNicolas RUGGLI, Sylvie PYTHON, Markus GERBER, Rolf SUTER,Artur SUMMERFIELDInstitute of Virology and Immunology, Mittelhäusern, SWITZERLANDPlasmacytoid dendritic cells (pDC) have been shown to sense efficientlyhepatitis C virus infected cells using a virion free pathway. We found thatpDC can also sense infection with classical swine fever virus (CSFV),another member of the Flaviviridae, by direct contact with infected cells,a process that is independent of virus particles. This process is much moreefficient in terms of interferon alpha induction when compared to directstimulation by virus particles. By employment of virus replicon particlesor infectious RNA that can replicate but not form de novo virions, a transferof virus from the donor cell to the pDC was excluded. Activation ofpDC by infected cells is mediated by a contact dependent RNA transfer topDC, which is sensitive to a TLR7 inhibitor. Interestingly, the Erns proteinof CSFV does efficiently prevent this process, which requires intactribonuclease function of Erns in intracellular compartments. The presentstudy underlines the importance of pDC activation by infected cells andidentifies a novel pathway of viral escape from the interferon system.ORAL COMMUNICATIONSREF 001Activation of RIG I by incoming RNA virus nucleocapsids containinga5 ′ triphosphorylated genomeMichaela WEBER 1 , Ali GAWANBACHT 2 , Matthias HABJAN 2 ,Andreas RANG 3 , Christoph BORNER 4,5 , Anna Mareike SCHMIDT 2,5 ,Sophie VEITINGER 6 , Ralf JACOB 6 , Stéphanie DEVIGNOT 1 , GeorgKOCHS 2 , Adolfo GARCÍA SASTRE 7,8,9 , Friedemann WEBER 1,2,51 Philipps University Marburg, Institute for Virology, Marburg,GERMANY; 2 University Freiburg, Department of Virology, Freiburg,GERMANY; 3 University Hospital Charité, Institute of Virology, Berlin,GERMANY; 4 University Freiburg, Institute of Molecular Medicine,Freiburg, GERMANY; 5 Albert Ludwigs University Freiburg, Centre forBiological Signalling Studies (BIOSS), Freiburg, GERMANY; 6 PhilippsUniversity Marburg, Department of Cell Biology and Cell Pathology,Marburg, GERMANY; 7 Mount Sinai School of Medicine, Department ofMicrobiology, New York, USA; 8 Mount Sinai School of Medicine, Departmentof Medicine, Division of Infectious Diseases, New York, USA; 9 MountSinai School of Medicine, Global Health and Emerging Pathogens Institute,New York, USAREF 003Integrins synergize with TLRs to initiate a specific branch of the innateresponse to herpes simplex virusGabriella CAMPADELLI FIUME, Tatiana GIANNIDepartment of Experimental Diagnostic and Specialty Medicine, AlmaMater Studiorum – University of Bologna, Bologna, ITALYIntegrins are exquisite signaling molecules that regulate a number of cellularprocesses. They are also very popular among viruses as cellularreceptors. We have discovered that the av3 integrin serves the additionalfunction of sensor of herpes simplex virus (HSV) and initiator of abranch of the innate response which culminates in the secretion of a specificset of cytokines, including IFNa and . This function is exerted throughinteraction and synergy with TLR2.Here we report that av3 integrin is not the only one integrin that servesthe function of innate response sensor. We found that av6 and av8 canserve as HSV receptors, each independently of the other, via interactionwith gH/gL. av6 but not av8 integrins can activate specific branches ofthe innate response. Further yet, integrins synergize also with TLR4. Thesignalling activity which culminates in the innate response involves theVirologie, Vol 17, supplément 2, septembre 2013S39