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

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

Schmallenberg virus experimental infection of sheep

International audienceSince late 2011, a novel orthobunyavirus, named Schmallenberg virus (SBV), has been implicated in many cases of severely malformed bovine and ovine offspring in Europe. In adult cattle, SBV is known to cause a mild transient disease; clinical signs include short febrile episodes, decreased milk production and diarrhoea for a few days. However, the knowledge about clinical signs and pathogenesis in adult sheep is limited. In the present study, adult sheep of European domestic breeds were inoculated with SBV either as cell culture grown virus or as virus with no history of passage in cell cultures. Various experimental set-ups were used. Sampling included blood collection at different time points during the experimental period and selected organ material at autopsy. Data from this study showed, that the RNAemic period in sheep was as short as reported for cattle; viral genome was detectable for about 3-5 days by real-time RT-PCR. In total, 13 out of 30 inoculated sheep became RNAemic, with the highest viral load in animals inoculated with virus from low cell culture passaged or the animal passaged material. Contact animals remained negative throughout the study. One RNAemic sheep showed diarrhoea for several days, but fever was not recorded in any of the animals. Antibodies were first detectable 10-14 days post inoculation. Viral RNA was detectable in spleen and lymph nodes up to day 44 post inoculation. In conclusion, as described for cattle, SBV-infection in adult sheep predominantly results in subclinical infection, transient RNAemia and a specific antibody response. Maintenance of viral RNA in the lymphoreticular system is observed for an extended period