Induction and modulation of type I interferon synthesis upon BTV infection

Bluetongue virus (BTV) is an arthropod-borne virus belonging to the Reoviridae family. It causes an haemorrhagic disease in ruminants that induces important economic losses. BTV infection triggers type I interferon (IFN-α/β) synthesis in vivo and in vitro, which is crucial to mount an efficient cellular antiviral response. This event requires viral replication since a UV inactivate virus is unable to induce IFN-β synthesis. We also showed that RNA helicases RIG-I and MDA5 are both involved in IFN-α/β production upon BTV infection. As this response is deleterious for viral replication, most of viruses have developed strategies to circumvent IFN action. We found that the non structural NS3 protein of BTV is a potent IFN-α/β inhibitorLe virus de la fièvre catarrhale ovine (FCO ; Bluetongue virus, BTV) est un arbovirus appartenant à la famille des Reoviridae. Il est responsable d’une maladie hémorragique chez les ruminants qui provoque d’importantes pertes économiques. L’infection par le BTV induit la production des interférons de type I (IFN-α/β) in vivo et in vitro, événement essentiel pour l’établissement d’une réponse cellulaire antivirale. Cette production requiert la réplication virale puisqu’un virus inactivé aux UV a perdu la capacité d’induire la synthèse d’IFN-β. Nous avons aussi pu démontrer que les ARN hélicases RIGI et MDA5 étaient impliquées dans la production d’IFN-α/β en réponse au BTV. Cette réponse étant délétère pour la multiplication virale, la plupart des virus ont développé des stratégies pour limiter l’action de l’interféron. Nous avons ainsi pu montrer que la protéine non structurale NS3 de BTV était un puissant antagoniste de la voie des IFN-α/

The nonstructural protein NSs of Schmallenberg virus is targeted to the nucleolus and induces nucleolar disorganization

Schmallenberg virus (SBV) was discovered in Germany in late 2011 and then spread rapidly to many European countries. SBV is an orthobunyavirus that causes abortion and congenital abnormalities in ruminants. A virus-encoded nonstructural protein, termed NSs, is a major virulence factor of SBV, and it is known to promote the degradation of Rpb1, a subunit of the RNA polymerase II (Pol II) complex, and therefore hampers global cellular transcription. In this study, we found that NSs is mainly localized in the nucleus of infected cells and specifically appears to target the nucleolus through a nucleolar localization signal (NoLS) localized between residues 33 and 51 of the protein. NSs colocalizes with nucleolar markers such as B23 (nucleophosmin) and fibrillarin. We observed that in SBV-infected cells, B23 undergoes a nucleolus-to-nucleoplasm redistribution, evocative of virus-induced nucleolar disruption. In contrast, the nucleolar pattern of B23 was unchanged upon infection with an SBV recombinant mutant with NSs lacking the NoLS motif (SBVΔNoLS). Interestingly, unlike wild-type SBV, the inhibitory activity of SBVΔNoLS toward RNA Pol II transcription is impaired. Overall, our results suggest that a putative link exists between NSs-induced nucleolar disruption and its inhibitory function on cellular transcription, which consequently precludes the cellular antiviral response and/or induces cell death

Colostral antibody induced interference of inactivated bluetongue serotype-8 vaccines in calves

Since its introduction into northern Europe in 2006, bluetongue has become a major threat to animal health. While the efficacy of commercial vaccines has been clearly demonstrated in livestock, little is known regarding the effect of maternal immunity on vaccinal efficacy. Here, we have investigated the duration and amplitude of colostral antibody-induced immunity in calves born to dams vaccinated against bluetongue virus serotype 8 (BTV-8) and the extent of colostral antibody-induced interference of vaccination in these calves. Twenty-two calf-cow pairs were included in this survey. The median age at which calves became seronegative for BTV was 84 and 112 days as assayed by seroneutralisation test (SNT) and VP7 BTV competitive ELISA (cELISA), respectively. At the mean age of 118 days, 13/22 calves were immunized with inactivated BTV-8 vaccine. In most calves vaccination elicited a weak immune response, with seroconversion in only 3/13 calves. The amplitude of the humoral response to vaccination was inversely proportional to the maternal antibody level prior to vaccination. Thus, the lack of response was attributed to the persistence of virus-specific colostral antibodies that interfered with the induction of the immune response. These data suggest that the recommended age for vaccination of calves born to vaccinated dams needs to be adjusted in order to optimize vaccinal efficacy

Exploration of binary protein-protein interactions between tick-borne flaviviruses and Ixodes ricinus

International audienceBackground : Louping ill virus (LIV) and tick-borne encephalitis virus (TBEV) are tick-borne flaviviruses that are both transmitted by the major European tick, Ixodes ricinus . Despite the importance of I. ricinus as an arthropod vector, its capacity to acquire and subsequently transmit viruses, known as vector competence, is poorly understood. At the molecular scale, vector competence is governed in part by binary interactions established between viral and cellular proteins within infected tick cells. Methods : To investigate virus-vector protein–protein interactions (PPIs), the entire set of open reading frames for LIV and TBEV was screened against an I. ricinus cDNA library established from three embryonic tick cell lines using yeast two-hybrid methodology (Y2H). PPIs revealed for each viral bait were retested in yeast by applying a gap repair (GR) strategy, and notably against the cognate protein of both viruses, to determine whether the PPIs were specific for a single virus or common to both. The interacting tick proteins were identified by automatic BLASTX, and in silico analyses were performed to expose the biological processes targeted by LIV and TBEV. Results : For each virus, we identified 24 different PPIs involving six viral proteins and 22 unique tick proteins, with all PPIs being common to both viruses. According to our data, several viral proteins (pM, M, NS2A, NS4A, 2K and NS5) target multiple tick protein modules implicated in critical biological pathways. Of note, the NS5 and pM viral proteins establish PPI with several tumor necrosis factor (TNF) receptor-associated factor (TRAF) proteins, which are essential adaptor proteins at the nexus of multiple signal transduction pathways. Conclusion : We provide the first description of the TBEV/LIV- I. ricinus PPI network, and indeed of any PPI network involving a tick-borne virus and its tick vector. While further investigation will be needed to elucidate the role of each tick protein in the replication cycle of tick-borne flaviviruses, our study provides a foundation for understanding the vector competence of I. ricinus at the molecular level. Indeed, certain PPIs may represent molecular determinants of vector competence of I. ricinus for TBEV and LIV, and potentially for other tick-borne flaviviruses

Emergence and re-emergence of two major diseases in France (bluetongue) and in Mauritius (foot-and-mouth)

L’émergence en France continentale de la fièvre catarrhale ovine (FCO) causée en 2006 par le virus de sérotype 8 (BTV-8) puis en 2007, par le virus de sérotype 1 (BTV-1) a constitué une surprise totale. Fin 2012, six ans après l’introduction de la FCO, la France a été déclarée indemne de cette maladie. Pourtant, fin août 2015, le BTV-8 a fait sa réapparition dans le centre de la France. En 2016 notre laboratoire a isolé à nouveau ce virus. En Corse, un virus de sérotype 4 (BTV-4) fut identifié le 1er décembre 2016 à partir de prélèvements de moutons. D’autre part, en 2016, nous avons identifié un virus de la fièvre aphteuse de sérotype O à Maurice. Cette présentation décrira les conditions de détection de ces virus ainsi que les résultats des analyses phylogénétiques.The emergence of Bluetongue (BT) in continental France (caused by virus of serotype 8 (BTV-8) in 2006 and virus of serotype 1 (BTV-1) in 2007) was a total surprise. End of 2012, six years after the introduction of BT, France was declared free from this disease. However, at the end of August 2015, the BTV-8 made its reappearance in the center of France. In 2016, our laboratory re-isolated this virus. In Corsica, a virus of serotype 4 was identified on 1st December 2016 from sheep samples. On another hand, in 2016, we identified a virus of Foot-and-Mouth disease serotype O in Mauritius. This presentation will describe the conditions of the detection of these viruses as well as the results of phylogenetic analyzes

Different viral genes modulate virulence in model mammal hosts and Culex pipiens vector competence in Mediterranean basin lineage 1 West Nile virus strains

West Nile virus (WNV) is a single-stranded positive-sense RNA virus (+ssRNA) belonging to the genus Orthoflavivirus. Its enzootic cycle involves mosquito vectors, mainly Culex, and wild birds as reservoir hosts, while mammals, such as humans and equids, are incidental dead-end hosts. It was first discovered in 1934 in Uganda, and since 1999 has been responsible for frequent outbreaks in humans, horses and wild birds, mostly in America and in Europe. Virus spread, as well as outbreak severity, can be influenced by many ecological factors, such as reservoir host availability, biodiversity, movements and competence, mosquito abundance, distribution and vector competence, by environmental factors such as temperature, land use and precipitation, as well as by virus genetic factors influencing virulence or transmission. Former studies have investigated WNV factors of virulence, but few have compared viral genetic determinants of pathogenicity in different host species, and even fewer have considered the genetic drivers of virus invasiveness and excretion in Culex vector. In this study, we characterized WNV genetic factors implicated in the difference in virulence observed in two lineage 1 WNV strains from the Mediterranean Basin, the first isolated during a significant outbreak reported in Israel in 1998, and the second from a milder outbreak in Italy in 2008. We used an innovative and powerful reverse genetic tool, e.g., ISA (infectious subgenomic amplicons) to generate chimeras between Israel 1998 and Italy 2008 strains, focusing on non-structural (NS) proteins and the 3′UTR non-coding region. We analyzed the replication of these chimeras and their progenitors in mammals, in BALB/cByJ mice, and vector competence in Culex (Cx.) pipiens mosquitoes. Results obtained in BALB/cByJ mice suggest a role of the NS2B/NS3/NS4B/NS5 genomic region in viral attenuation in mammals, while NS4B/NS5/3′UTR regions are important in Cx. pipiens infection and possibly in vector competence

Interaction de la protéine non structurale NSP3 de Rotavirus avec la protéine cellulaire RoXaN

Avec environ 500 000 décès annuels, les rotaviroses représentent l'une des causes majeures de gastroentérites infectieuses dans le monde. L'agent étiologique virale de ces infections, le rotavirus, code pour six protéines structurales (VP) et six protéines non structurales (NSP). Parmi celles-ci, la protéine NSP3 interagit avec l'ARN viral et le facteur de traduction eIF4G, et joue un rôle central dans la traduction des ARNm viraux. Un nouveau partenaire pour NSP3, la protéine cellulaire RoXaN (Rotavirus X protein associated with NSP3), a été identifiée. Ce travail avait pour objet l'étude de l'interaction NSP3-RoXan et la caractérisation des propriétés de la protéine RoXan. Les domaines d'interaction ont été identifiés sur les deux protéines. Ils impliquent la région centrale de NSP3 (aa 170-234), prédite en coiled-coil, et un domaine putatif Ld présent dans la région amino-terminale de RoXan (aa 255-279). RoXan a une distribution nucléo-cytoplasmique dans la cellule. Par ailleurs, nous avons pu montrer qu'elle était phosphorylable et que l'extrémité amino-terminale (aa 1-174), qui contient un domaine tétratricopeptidique (TPR), co-localisait partiellemnt avec le réseau de vimentine. L'existence, enfin, d'un complexe ternaire RoXan-NSP3-eIF4G, et la co-immunoprécipitation ARN-dépendante de la poly(A)-binding protein (PABP) avec la région carboxy-terminale de RoXan suggèrent un rôle traductionnel pour cette dernière. Cette hypothèse requirt cependant des investigations supplémentaires et ne permet pas d'écarter une ou plusieurs autres fonctions pour la protéine.CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Vaccination against two vector-borne diseases bluetongue and West Nile

National audienceIn 1999 and 2006, two viral diseases emerged massively and unexpectedly in the United States (West Nile disease) and northern Europe (bluetongue disease). Control of infectious diseases transmitted by insect vectors is based on a variety of approaches (including sanitary measures), but primarily on vaccination. Vaccination is more efficient and less expensive than monitoring of insect vectors. The dynamics and epidemiology of two arboviral diseases (West Nile and bluetongue) are described, together with the different vaccines and vaccination methods

Vaccination against two vector-borne diseases bluetongue and West Nile

National audienceIn 1999 and 2006, two viral diseases emerged massively and unexpectedly in the United States (West Nile disease) and northern Europe (bluetongue disease). Control of infectious diseases transmitted by insect vectors is based on a variety of approaches (including sanitary measures), but primarily on vaccination. Vaccination is more efficient and less expensive than monitoring of insect vectors. The dynamics and epidemiology of two arboviral diseases (West Nile and bluetongue) are described, together with the different vaccines and vaccination methods