rologie i - European Congress of Virology

5 th European Congress of VirologyRepeated infections by different Influenza A virus subtypes within pigfarms increase the risk of emergence of novel reassortant viruses. Theobjectives of this study were to characterise the epidemiology of recurrentinfections with swine influenza viruses for identification of main determinants.A follow up study was carried out in 3 selected farms known tobe affected by repeated Influenza infections. Three batches of pigs werefollowed within each farm from birth to slaughter, through a representativesample of 40 piglets per batch. Piglets were monitored individuallyon a monthly basis for serology and clinical parameters. Daily virologicaland clinical investigations took place for two weeks when a fluoutbreak occurred. Influenza outbreaks, confirmed by Influenza A virusdetection, were reported at least once in each followed batch. These outbreaksoccurred at constant ages within farms and were correlated withan increase in the frequency of sneezing and coughing fits. H1N1 andH1N2 viruses from European enzootic subtypes as well as reassortantviruses between these lineages were identified consecutively and sometimessimultaneously according to studied batches, suggesting virus cocirculations at the farm, batch and sometimes individual levels. The estimatedreproduction rate R of Influenza outbreaks ranged between 2.5 [1.92.9] and 6.9 [4.1 10.5] according to age at infection time and serologicalstatus of infected piglets. Duration of shedding was also influenced bythe age at infection time, the serological status of the dam and minglingpractices. An impaired humoral response was identified in piglets infectedat a time they still presented maternally derived antibodies.REF O66Different strategies of host infection by bovine respiratory virusesJana KIRCHHOFF 1 , Sabine UHLENBRUCK 1 , Günther KEIL 2 , GeorgHERRLER 11 Institute of Virology/University of Veterinary Medicine Hannover, Hannover,GERMANY; 2 Friedrich Loeffler Institut, Riems, GERMANYBovine respiratory disease complex (BRDC) is the major cause of seriousrespiratory tract infections in calves. The disease is multifactorial, witheither stress or reduced immunity allowing several pathogens to emerge.We investigated the susceptibility of bovine airway epithelial cells (BAEC)to infection by different viruses belonging to the BRDC: bovine respiratorysyncytial virus (BRSV), bovine herpes virus type 1 (BHV 1) and bovineparainfluenza virus type 3 (BPIV 3). For this purpose, two culture systemsfor well differentiated BAEC were established: the air liquid interface(ALI) system, where filter grown BAEC differentiate into a pseudostratifiedrespiratory epithelium and precision cut lung slices (PCLS) whereBAEC are maintained in the original tissue organisation. Comparativeinfection studies demonstrated that BPIV 3 specifically infected ciliatedcells at the apical surface of the epithelium whereas BHV 1 infection wasrestricted to basal cells. In case of ALI cultures, this was achieved bypretreatment of cells with EGTA or injury of the cell layer with a sterileneedle. In contrast, overall infection level of BRSV was low in well differentiatedBAEC. In PCLS, infected cells were predominantly present insubepithelial regions and primary observations suggest that dendritic cellsmay play a role in viral spread. Altogether, these results indicate that thethree viruses of the bovine respiratory disease complex follow differentstrategies to enter primary target cells of the respiratory epithelium.some time in 2011 and subsequently spread across the Netherlands, Belgiumand France into the UK – most likely via midges blown across theChannel, similar to the incursion of Bluetongue in 2007. While SBV isgenetically most closely related to Douglasvirus, Sathuperivirus and Shamondaviruskey features in the pathogenesis from Akabanevirus, such asfetal malformations in ruminants also apply.In January 2012 the first malformed fetuses were observed in sheep, soonfollowed by cattle with cases rapidly spreading across Southern England.Analysis of weather conditions, serology results and sheep gestation times,suggest one or two parallel incursions into England before the end ofSeptember 2011. However, molecular analysis of the M and S gene segmentsfrom both sheep and cattle over the first year was unable to showa pattern consistent with incursion or spread of the virus demonstratinga random nature of changes instead that may reflect the multiple hostchanges.As cases did not cease over summer of 2012 it became evident that SBVremained in the UK, spreading further across England and Wales. Bothserological results of animals naturally infected and the analysis of bullsused for breeding demonstrated that SBV may persist in some animalsat least, which in turn may shed the virus via semen for several monthsfollowing infection.REF O68Modulation of the interferon signalling pathway by bluetongue virusVirginie DOCEUL, Emilie CHAUVEAU, Estelle LARA, StéphanZIENTARA, Damien VITOURUMR 1161 Virologie ANSES INRA ENVA, Maisons Alfort, FRANCEBluetongue virus (BTV) is a double stranded RNA virus belonging to theOrbivirus genus and the Reoviridae family that affects domestic and wildruminants including sheep, cattle and goats. In 2006, a strain of serotype8 of BTV has emerged in the Netherlands and spread to Central and WesternEuropean countries, causing significant economical losses. BTV isa strong inducer of type I interferon (IFN I) both in vivo and in vitro inmultiple cell types derived from various tissues and species. Recently, weidentified RIG I and MDA5 helicases as sensors of BTV infection in nonhematopoietic cells and showed that these molecules displayed antiviralactivities against the virus. As IFN I is detrimental for viral replication,most viruses have evolved mechanisms to counteract the host antiviralresponse triggered by the infection. In this study, we aimed to investigatethe ability of BTV to modulate the induction of IFN I. Using a reporterassay, we found that BTV inhibits IFN promoter activity after stimulationof the RIG I like receptor (RLR) pathway. We identified the BTV nonstructural protein NS3 as a potent inhibitor of IFN synthesis and showedthat the viral protein interferes with the RLR pathway downstreamRIG I and upstream IKKe activation. We are now undertaking furtherstudies to characterise the mechanisms involved in this inhibition. We arealso currently investigating the ability of BTV to interfere with the IFNI response pathway and particularly the JAK/STAT signalling cascade. Abetter understanding of the strategies evolved by BTV to counteract thehost antiviral responses is essential to design new prophylactic agents andcontrol the virus.REF O67Schmallenberg virus – two years after the incursion into the UKFalko STEINBACH, Anna LA ROCCA, Akbar DASTJERDI, TrevorDREW, Christopher FINNEGAN, Julie PEAKE, Sarah MCGOWAN,Sylvia GRIERSON, Bhudipa CHOUDHURYVirology Dept., AHVLA, Addlestone, UNITED KINGDOMSchmallenberg virus (SBV) is a novel Orthobunyavirus first reported inGermany at the end of 2011. The virus incurred into continental EuropeREF O69Study of the virulence of Serotypes 4 and 9 of the Orbivirus Africanhorse sickness virus in two mouse modelsMaria Ana DE LA GRANDIÈRE 1 , William ZONTA 1 ,AxelMAUROY 1 , Fabiana DAL POZZO 2 , Etienne THIRY 11 University of Liège, Faculty of Veterinary Medicine, Veterinary Virologyand Viral Animal Diseases, Liège, BELGIUM; 2 University of Liège,Faculty of Veterinary Medicine,Epidemiology and risk analysis applied toveterinary sciences, Liège, BELGIUMVirologie, Vol 17, supplément 2, septembre 2013S65