rologie i - European Congress of Virology

5 th European Congress of VirologyFriday 13 th September 2013, 8h30 – 10h30WORKSHOP 6: “RESTRICTION FACTORS OF VIRALINFECTION, INTERFERING RNA & IMMUNE RESPONSE”KEYNOTE:Chairpersons: Santo LANDOLFO (Turin, ITALY)& Soren PALUDAN (Aarhus, DENMARK)Room Prestige Gratte-CielRestriction Factors are key determinants of viral susceptibilityMonsef BENKIRANEInstitut de Génétique Humaine (CNRS-UPR1142), Montpellier, FRANCEThe outcome of viral infection results from complex interactions betweenviral proteins and host cell factors. Viruses have evolved to establish acomplex network of interactions with host facilitating factors required forthe achievement of the viral life cycle and to evade intracellular defensemechanisms which otherwise sense the virus and establish an antiviralstate. Indeed, upon entry in the human host, viruses are confronted withnumerous blocks that oppose their replication. The first line of defenseto be triggered is the so-called “intrinsic” immune system. The intrinsicimmune system includes proteins that detect the presence of the assailant(Pattern Recognition Receptors [PRRs]) and initiate a subsequentimmune response, as well as proteins referred to as restriction factors thatare directly devoted to arresting the replication cycle of the virus. We willuse primate lentiviruses and host restriction factors that block their replicationas examples to highlight their role in determining host susceptibilityand disease.ORAL COMMUNICATIONSREF 077Defining the relationship between miRNAs and cytoplasmic virusesSimone BACKES, Ryan LANGLOIS, Benjamin TENOEVERIcahn School of Medicine at Mount Sinai, New York, USAMicroRNAs (miRNAs) regulate gene expression through sequence specificbinding to target mRNAs, resulting in translational repression andsubsequent deadenylation. We have previously shown that poxvirusesinduce the overall degradation of host miRNAs through the virally encodedpoly(A) polymerase VP55 subunit. The discovery of a miRNA antagonizingfunction encoded by poxviruses suggests that miRNAs may aid inrestricting virus replication. In an effort to expand our knowledge aboutthe impact of host miRNAs on gene expression and replication of differentviruses, we are utilizing poxviral VP55 as a tool to investigatethe interplay between viruses, host miRNAs and the cellular responseto infection. To this end, we engineered Vesicular stomatitis virus (VSV)to express poxvirus VP55 (VSV VP55) in an effort to determine whetherloss of host miRNAs confered a replicative advantage. VSV VP55displayed high expression levels of poxvirus VP55 and was also capableof inducing polyadenylation of miRNAs. Currently, we are performingparallel infections both ex vivo and in vivo in the context of either wildtype and interferon defective genotypes in order to compare viral mRNAlevels, protein expression capacity and viral replication kinetics. As VP55induces overall degradation of host miRNAs in infected cells, this newtool will allow studying the impact of host miRNAs on the pathogenesisof different viruses.REF O78Regulation of virus endocytosis by miRNAsPierre Yves LOZACH 1 , Roger MEIER 2 , Andrea FRANCESCHINI 3 ,Peter HORVATH 2 , Marilou TETARD 1 , Christian VON MERING 3 , AriHELENIUS 21 INRS Institut Armand Frappier, Laval, CANADA; 2 Swiss Federal Instituteof Technology (ETH), Zurich, SWITZERLAND; 3 University of Zurich,Zurich, SWITZERLANDThe Bunyaviridae constitute a large family of enveloped animal viruses,many of which cause serious diseases in humans. Currently there areno available vaccines or treatments approved for human use. The strategiesemployed by these viruses for transmission and infection remainpoorly understood. To investigate into early bunyavirus host interactions,we screened siRNA libraries from two providers against the whole humangenome for their ability to block infection. These screens revealed morethan 500 cellular proteins with a potential role in bunyavirus entry andreplication. Our data support the view that some siRNAs act like miRNAsto down regulate gene expression. Therefore, we assessed miRNAs, withsequences identical to those of siRNA seed regions found in the screens(6 7 nucleotides), for their capacity to inhibit infection. Within these miR-NAs, we identified the miRNA 142.3p as blocking infection at the levelof virus entry. A DNA microarray screen shown that many genes regulatedby this miRNA have functions related to endocytosis. Within thissymposium, the confirmation of hits will be illustrated with the analysisof the cellular factor v SNARE VAMP 3 by state of the art fluorescencebased techniques in fixed and living cells. The prospects and challengesof future work on the cell biology of bunyavirus entry will be thendiscussed.REF O79Host microRNA molecular signatures associated with humaninfluenza A virus infections reveal an unanticipated antiviral activityfor miR 146aOlivier TERRIER 1 , Julien TEXTORIS 2 , Coralie CARRON 1 , VirginieMARCEL 3 , Jean Christophe BOURDON 3 , Manuel ROSACALATRAVA 11 Laboratoire de Virologie et Pathologie Humaine VirPath, Equipe VirCell,Université Claude Bernard Lyon 1, Université de Lyon, Lyon, FRANCE;2 Laboratoire d’Immunologie, UMR CNRS 7278, INSERM U1095, Facultéde Médecine Timone, Marseille, FRANCE; 3 Division of Medical Sciences,Centre for Oncology and Molecular Medicine, University of Dundee,Ninewells Hospital, Dundee, UNITED KINGDOMWhile post transcriptional regulation of gene expression by miRNAs havebeen shown to be involved in influenza virus replication cycle, only afew studies have further investigated this aspect in a human cellular modelinfected with human influenza viruses. In this study, we performed miRNAglobal profiling in human lung epithelial cells (A549) infected by differentsubtypes of human influenza A viruses. We identified a common miRNAsignature in response to infection by the different strains, highlighting apool of five miRNAs commonly deregulated, which are known to be involvedin the innate immune response or apoptosis. Among the five miRNAhits, the only up regulated miRNA in response to influenza infection correspondedto miR 146a. Based on a previously published gene expressiondataset, we extracted inversely correlated miR 146a target genes and determinedtheir first level interactants. This functional analysis revealed 8distinct biological processes strongly associated with these interactants:TLR pathway, innate immune response, cytokine production and apoptosis.To better understand the biological significance of miR 146a upregulation, using a reporter assay and a specific anti miR 146a inhibitor,we confirmed that infection increases the endogenous miR 146a promoteractivity and that inhibition of miR 146a significantly increased viralS70 Virologie, Vol 17, supplément 2, septembre 2013