rologie i - European Congress of Virology

5 th European Congress of Virologythree amino acids in the nectin 4 V domain F G loop crucial for functionalinteractions with MV H; in addition, residues in other two loops influencethese interactions. Thus MV appropriates the adhesive surface of nectinsto infect the respiratory epithelium.REF 162Different sensitivity of primary chicken oviduct epithelial cells for thecoronavirus IBV strains QX, B1648 and Beaudette is not related tothe binding properties of their spike proteinsAnn Kathrin MORK 1 , Sahar ABD EL RAHMANN 2 , GeorgHERRLER 1 , Christine WINTER 11 University of Veterinary Medicine, Hannover, Institute of Virology,Hannover, GERMANY; 2 Mansoura University, Department of Virology,Mansoura, EGYPTAs a member of the family Coronaviridae, Infectious bronchitis virus(IBV) is a one of the most important pathogens within the poultry industry.A characteristic of IBV is the occurrence of many different strainsbelonging to different serotypes, which makes a complete control of thedisease by vaccines challenging. Reasons for differences in the tissue tropismand pathogenicity of the IBV strains, as e.g. a predilection to thekidneys or the oviduct are still an open question. The QX strain has beena major pathogen in poultry flocks in Asia, Europe and other parts of theworld. It is the cause of severe problems with kidney disease and reproductivetract disorders. We analyzed infectivity and binding properties of theQX strain and compared it with the nephropathogenic IBV strain B1648and the apathogenic IBV Beaudette strain. We observed that the analyzedstrains infected primary oviduct epithelial cells with different intensity.Epithelial cells of the oviduct showed a high sensitivity to the QX strain, alower sensitivity to the Beaudette strain and were nearly not sensitive to thenephropathogenic B1648 strain. In contrast, binding tests on cryosectionsand FACS analysis with isolated primary oviduct epithelial cells and thecorresponding soluble spike proteins revealed that all tested spike proteinsbound with high affinity to these cells. Our results show that the differentsensitivity of primary chicken oviduct epithelial cells for the tested IBVstrains cannot be explained with a different affinity of the spike proteinsto host epithelial cells.presence of H. H specific monoclonal antibodies as well as a mutationin H interfering with H/F co operation, blocked cell entry. The particlesmediated stable and specific transfer of reporter genes into Her2 positivehuman tumor cells also in vivo, while exhibiting improved infectivity andhigher titers as compared to Her2 targeted vectors displaying the targetingdomain on H. Extending the current model of MV cell entry, the datasuggest that receptor binding of H is not required for its fusion helperfunction but particle cell contact in general may be sufficient to inducethe conformational changes in the H/F complex and activate membranefusion.REF 164Integrins modulate the entry efficiency of West Nile Virus into cellsKatja SCHMIDT 1 , Markus KELLER 1 , Martin H. GROSCHUP 1Friedrich Loeffler Institut, Greifswald Insel Riems, GERMANYThe underlying mechanisms allowing West Nile virus (WNV) to replicatein a large variety of different arthropod, mammal and bird speciesare largely unknown, but are believed to rely on highly conserved proteinsrelevant for viral entry and replication. A previous study had postulatedearlier that integrin av3 functions as the receptor for WNV; however,its involvement has been doubted recently. The present study was designedto clarify the involvement of integrins in WNV entry. A cell culturemodel was established based on specific integrin knock out cell lines with aspecific modification in the particular integrin subunit genomic sequence.Wild type and specifically integrin deficient mouse fibroblasts lackingthe integrin subunits av, 1 or3, respectively, allowed (i) studying theinvolvement of integrins, (ii) identifying the integrin subunit involved and(iii) addressing their function in WNV entry. Additional questions wereaddressed as to the extent to which they participate in virus entry and to possibledifferences in the entry efficiencies in distinct WNV strains. All celllines were permissive but differences between integrin expressing and nonexpressing cells were seen. Results clearly demonstrate that the expressionof 1 and 3 integrins positively affected virus yields significantly,as seen in integrin 3 rescue and integrin 1 floxed cells in comparison tothe corresponding integrin deficient cell line. However, integrins obviouslydo not function at the level of WNV binding to the cell surface but ratherdownstream during entry or in post entry stages.REF 163The receptor attachment function of measles virus hemagglutinincan be replaced with an autonomous protein that binds Her2 whilemaintaining its fusion helper functionAnke RASBACH 1 , Tobias ABEL 1 , Robert MÜNCH 1 , Klaus BOLLER 1 ,Jürgen SCHNEIDER SCHAULIES 2 , Christian BUCHHOLZ 11 Paul Ehrlich Institut, Langen, GERMANY; 2 University of Würzburg,Würzburg, GERMANYCell entry of enveloped viruses is initiated by attachment to the virusreceptor followed by fusion between the virus and host cell membranes.Measles virus (MV) attachment to its receptor is mediated by the hemagglutinin(H), which is thought to produce conformational changes in themembrane fusion protein (F) that trigger insertion of its fusion peptideinto the target cell membrane. Here, we uncoupled receptor attachmentand fusion helper function of H by introducing Y481A, R533A, S548L,and F549S mutations into the viral attachment protein that made it blindto its normal receptors. An artificial attachment protein specific for Her2was incorporated into pseudotyped lentivirus particles as a separate transmembraneprotein along with the F protein. Surprisingly, these particlesentered efficiently into Her2 positive SK OV 3 as well as CHO Her2 cells.Cell entry was independent of endocytosis, but strictly dependent on theREF 165Stem anchor interactions of the fusion protein E in flavivirusmembrane fusionKarin STIASNY, Janja BLAZEVIC, Iris MEDITS, Victoria BRADT,Franz X. HEINZMedical University of Vienna, Vienna, AUSTRIAViral membrane fusion proceeds through a sequence of steps that are drivenby structural changes of viral envelope proteins (fusion proteins). Weattempt to define intermediate stages of this process using the class IIfusion protein E of the flavivirus tick borne encephalitis virus as a model.After virus uptake by endocytosis, fusion is triggered by the acidic pHin endosomes which leads to a conversion of the E homodimers on thevirion surface into more stable trimers. The crystal structures of truncatedE proteins in their pre and post fusion forms lack the so called ‘stem’region and the double membrane anchor. Since these elements are hypothesizedto have crucial functions in fusion, we investigated their roleby mutagenesis of infectious viruses as well as recombinant E proteins.The stem connects the ectodomain to the membrane anchor and is predictedto ‘zipper’ along the trimer core during E conformational changes,thus providing part of the energy required for fusion. We identifiedS164 Virologie, Vol 17, supplément 2, septembre 2013