Reoviridae

Le présent travail est une étude bibliographique des principaux agents incriminés lors d’entérites virales chez le poulet et la dinde notamment : les rotavirus, les entérovirus-like, les astrovirus, les coronavirus, les réovirus et les adénovirus.

Background As well as inducing direct oncolysis, reovirus treatment of melanoma is associated with activation of innate and adaptive anti-tumour immune responses. Results Here we characterise the effects of conditioned media from reovirus-infected, dying human melanoma cells (reoTCM), in the absence of live virus, to address the immune bystander potential of reovirus therapy. In addition to RANTES, IL-8, MIP-1α and MIP-1β, reovirus-infected melanoma cells secreted eotaxin, IP-10 and the type 1 interferon IFN-β. To address the mechanisms responsible for the inflammatory composition of reoTCM, we show that IL-8 and IFN-β secretion by reovirus-infected melanoma cells was associated with activation of NF-κB and decreased by pre-treatment with small molecule inhibitors of NF-κB and PKR; specific siRNA-mediated knockdown further confirmed a role for PKR. This pro-inflammatory milieu induced a chemotactic response in isolated natural killer (NK) cells, dendritic cells (DC) and anti-melanoma cytotoxic T cells (CTL). Following culture in reoTCM, NK cells upregulated CD69 expression and acquired greater lytic potential against tumour targets. Furthermore, melanoma cell-loaded DC cultured in reoTCM were more effective at priming adaptive anti-tumour immunity. Conclusions These data demonstrate that the PKR- and NF-κB-dependent induction of pro-inflammatory molecules that accompanies reovirus-mediated killing can recruit and activate innate and adaptive effector cells, thus potentially altering the tumour microenvironment to support bystander immune-mediated therapy as well as direct viral oncolysis.

Eleven viral isolates derived mostly in Aedes cells from mosquito pools collected in Southeast Asia and the Americas between 1966 and 2014 contained particles with electron microscopy morphology typical of reoviruses. Metagenomics analysis yielded the near complete genomes of three novel reoviruses, Big Cypress orbivirus, Ninarumi virus, and High Island virus and a new tetravirus, Sarawak virus. Strains of previously characterized Sathuvarachi, Yunnan, Banna and Parry's Lagoon viruses (Reoviridae), Bontang virus (Mesoniviridae), and Culex theileri flavivirus (Flaviviridae) were also characterized. The availability of these mosquito virus genomes will facilitate their detection by metagenomics or PCR to begin to determine their geographic range, extent of host tropism, and possible association with arthropod or vertebrate disease.

When MA104 cells were infected with SA11 rotavirus, 12 protein classes, absent in mock-infected cells, could be distinguished by polyacrylamide gel electrophoresis. At least two of these proteins were glycosylated, and their synthesis could be blocked with tunicamycin. The oligosaccharides of both glycoproteins were cleaved by endo-beta-N-acetylglucosaminidase H, suggesting that they were residues of the "high-mannose" type. Of the 12 viral polypeptides observed in infected cells, 1 was probably the apoprotein of one of these glycoproteins; 5, including 1 glycoprotein, were structural components of the virions, whereas the other 6, including a second and possibly third glycoprotein, were nonstructural viral proteins. When the 11 double-stranded RNA genome segments of SA11 were translated, after denaturation, in an RNA-dependent cell-free translation system, at least 11 different polypeptides were synthesized. Ten of these polypeptides had electrophoretic migration patterns...

A reovirus was isolated from juvenile Moellendorff's ratsnakes (Elaphe moellendorffi) and beauty snakes (Elaphe taenuris) that died soon after importation into the USA. Viper heart (VH2) cells inoculated with tissue homogenates showed cytopathic effects consisting of large syncytia formation followed by cell detachment from the monolayer. Tissue culture supernatants failed to hemagglutinate guinea pig and chicken erythrocytes at room temperature. Electron microscopy of purified virions revealed spherical to icosahedral particles measuring 70-85 nm in diameter with a double capsid layer. Preparations of the viral genome contained ten segments of dsRNA when analyzed by polyacrylamide gel electrophoresis. A juvenile black ratsnake (Elaphe obsoleta obsoleta) was experimentally inoculated with the isolate and was found dead 26 days post inoculation. Necropsy revealed diffuse subacute interstitial pneumonia with respiratory epithelial cell hyperplasia and syncytia. Reovirus isolated from this snake was used to inoculate another juvenile black ratsnake which was euthanized 40 days post inoculation. Pneumonia and multifocal subacute proliferative tracheitis were found on necropsy. Reovirus was isolated from the lung of this snake and was demonstrated by transmission electron microscopy. This is the first documentation of a pathogenic reptile reovirus and the first report of experimental transmission of a reovirus in snakes.

Replication of the Dearing strain of reovirus serotype 3 in mouse L cells was decreased 17- to 100-fold when a saturating dose of beta interferon (1,000 IU/ml) was used. Replication of the Lang strain of reovirus serotype 1 was inhibited only two- to threefold under similar conditions. It therefore appears that closely related strains of reovirus differ in their sensitivities to beta interferon treatment of mouse L cells.

Transcripts encoding ADAR1, a double-stranded, RNA-specific adenosine deaminase involved in the adenosine-to-inosine (A-to-I) editing of mammalian RNAs, can be alternatively spliced to produce an interferon-inducible protein isoform (p150) that is up-regulated in both cell culture and in vivo model systems in response to pathogen or interferon stimulation. In contrast to other tissues, p150 is expressed at extremely low levels in the brain and it is unclear what role, if any, this isoform may play in the innate immune response of the central nervous system (CNS) or whether the extent of editing for RNA substrates critical for CNS function is affected by its induction. To investigate the expression of ADAR1 isoforms in response to viral infection and subsequent alterations in A-to-I editing profiles for endogenous ADAR targets, we used a neurotropic strain of reovirus to infect neonatal mice and quantify A-to-I editing in discrete brain regions using a multiplexed, high-throughput sequencing strategy. While intracranial injection of reovirus resulted in a widespread increase in the expression of ADAR1 (p150) in multiple brain regions and peripheral organs, significant changes in site-specific A-to-I conversion were quite limited, suggesting that steady-state levels of p150 expression are not a primary determinant for modulating the extent of editing for numerous ADAR targets in vivo.

A combination of biologic and economic factors have led to an increased interest in the culture of several species of marine fishes. In eastern Canada the choice for development is halibut because of its high market value, abundance of suitable habitat for culture and the ...

Endoplasmic reticular (ER) membrane modifications play an important role in viral RNA replication and virion assembly but little is known about the involvement of ER-membrane remodeling in the infection cycle of fijiviruses in plant cells. The subcellular localization of Rice black-streaked dwarf virus outer capsid P10 was therefore examined using live-cell imaging. P10 fused to eGFP formed vesicular structures associated with ER membranes in Nicotiana benthamiana epidermal cells and in rice protoplasts. Subcellular fractionation experiments confirmed that P10 is an integral membrane protein. Three predicted transmembrane domains and two less-well-defined domains were each able to target eGFP to the ER. Disruption of the actin cytoskeleton with LatB, indicated that the maintenance of P10-induced membrane structures required the intact actin cytoskeleton. P10 induced the expression of ER stress marker genes, including ER stress-related chaperones and transcription factor, indicating ...

Isometric reolike virions were found in all the examined Drosophila simulans flies from two strains (SimES-st and Israel-st) presenting the S phenotype, a maternally inherited morphological trait (abnormalities of bristles). Normal flies of both strains appeared virus-free. Virions were found in the cytoplasm of male and female gonads and epidermal cells, including the bristle-forming cells, which appeared disorganized. Steps of virogenesis were described. A positive correlation was demonstrated between expressivity of the S phenotype and degree of viral infection. This hereditary reolike virus seems to be responsible for the S character of D. simulans and was named DSV (Drosophila S virus).

Rice dwarf virus (RDV), a member of the Reoviridae family, is a double-stranded RNA virus. Infection of rice plants with RDV reduces crop production significantly and can pose a major economic threat to Southeast Asia. A 25-A three-dimensional structure of the 700-A-diameter RDV capsid has been determined by 400-kV electron cryomicroscopy and computer reconstruction. The structure revealed two distinctive icosahedral shells: a T=13l outer icosahedral shell composed of 260 trimeric clusters of P8 (46 kDa) and an inner T=1 icosahedral shell of 60 dimers of P3 (114 kDa). Sequence and structural comparisons were made between the RDV outer shell trimer and the two crystal conformations (REF and HEX) of the VP7 trimer of bluetongue virus, an animal analog of RDV. The low-resolution structural match of the RDV outer shell trimer to the HEX conformation of VP7 trimer has led to the proposal that P8 consists of an upper domain of beta-sandwich motif and a lower domain of alpha helices. The l...