Biochemical adaptation of camelids during periods where feed is withheld

Biochemical changes during fasting or the withholding of feed for 5 day were studied in serum of camelids (dromedary camel, llama) and ruminants (sheep, steers). Camels maintained low levels of 13-hydroxybutyrate (BHB) and high levels of glucose but showed some increased levels of non-esterified fatty acid (NEFA) and urea when fasting. Sheep and steers showed a rise in serum BHB and much higher increases of NEFA than camels and llamas. Sheep showed decreased serum glucose. The llama showed some increase in BHB but NEFA was lower than the other three species. The results indicate that camelids have a unique ability to control lipolytic and gluconeogenic activity to prevent or postpone the state of ketosis. Understanding and manipulation of these metabolic mechanisms in cattle and sheep could have great benefit to the livestock industry

Discovery of a small arterivirus gene that overlaps the GP5 coding sequence and is important for virus production

The arterivirus family (order Nidovirales) of single-stranded, positive-sense RNA viruses includes porcine respiratory and reproductive syndrome virus and equine arteritis virus (EAV). Their replicative enzymes are translated from their genomic RNA, while their seven structural proteins are encoded by a set of small, partially overlapping genes in the genomic 3′-proximal region. The latter are expressed via synthesis of a set of subgenomic mRNAs that, in general, are functionally monocistronic (except for a bicistronic mRNA encoding the E and GP2 proteins). ORF5, which encodes the major glycoprotein GP5, has been used extensively for phylogenetic analyses. However, an in-depth computational analysis now reveals the arterivirus-wide conservation of an additional AUG-initiated ORF, here termed ORF5a, that overlaps the 5′ end of ORF5. The pattern of substitutions across sequence alignments indicated that ORF5a is subject to functional constraints at the amino acid level, while an analysis of substitutions at synonymous sites in ORF5 revealed a greatly reduced frequency of substitution in the portion of ORF5 that is overlapped by ORF5a. The 43–64 aa ORF5a protein and GP5 are probably expressed from the same subgenomic mRNA, via a translation initiation mechanism involving leaky ribosomal scanning. Inactivation of ORF5a expression by reverse genetics yielded a severely crippled EAV mutant, which displayed lower titres and a tiny plaque phenotype. These defects, which could be partially complemented in ORF5a-expressing cells, indicate that the novel protein, which may be the eighth structural protein of arteriviruses, is expressed and important for arterivirus infection

Discovery of a small arterivirus gene that overlaps the GP5 coding sequence and is important for virus production

The arterivirus family (order Nidovirales) of single-stranded, positive-sense RNA viruses includes porcine respiratory and reproductive syndrome virus and equine arteritis virus (EAV). Their replicative enzymes are translated from their genomic RNA, while their seven structural proteins are encoded by a set of small, partially overlapping genes in the genomic 3′-proximal region. The latter are expressed via synthesis of a set of subgenomic mRNAs that, in general, are functionally monocistronic (except for a bicistronic mRNA encoding the E and GP2 proteins). ORF5, which encodes the major glycoprotein GP5, has been used extensively for phylogenetic analyses. However, an in-depth computational analysis now reveals the arterivirus-wide conservation of an additional AUG-initiated ORF, here termed ORF5a, that overlaps the 5′ end of ORF5. The pattern of substitutions across sequence alignments indicated that ORF5a is subject to functional constraints at the amino acid level, while an analysis of substitutions at synonymous sites in ORF5 revealed a greatly reduced frequency of substitution in the portion of ORF5 that is overlapped by ORF5a. The 43–64 aa ORF5a protein and GP5 are probably expressed from the same subgenomic mRNA, via a translation initiation mechanism involving leaky ribosomal scanning. Inactivation of ORF5a expression by reverse genetics yielded a severely crippled EAV mutant, which displayed lower titres and a tiny plaque phenotype. These defects, which could be partially complemented in ORF5a-expressing cells, indicate that the novel protein, which may be the eighth structural protein of arteriviruses, is expressed and important for arterivirus infection

Comparative studies on the pathogenicity and tissue distribution of three virulence variants of classical swine fever virus, two field isolates and one vaccine strain, with special regard to immunohistochemical investigations

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to compare the tissue distribution and pathogenicity of three virulence variants of classical swine fever virus (CSFV) and to investigate the applicability of various conventional diagnostic procedures.</p> <p>Methods</p> <p>64 pigs were divided into three groups and infected with the highly virulent isolate ISS/60, the moderately virulent isolate Wingene'93 and the live attenuated vaccine strain Riems, respectively. Clinical signs, gross and histopathological changes were compared in relation to time elapsed post infection. Virus spread in various organs was followed by virus isolation, by immunohistochemistry, applying monoclonal antibodies in a two-step method and by <it>in situ </it>hybridisation using a digoxigenin-labelled riboprobe.</p> <p>Results</p> <p>The tissue distribution data are discussed in details, analyzing the results of the various diagnostic approaches. The comparative studies revealed remarkable differences in the onset of clinical signs as well as in the development of the macro- and microscopical changes, and in the tissue distribution of CSFV in the three experimental groups.</p> <p>Conclusion</p> <p>The present study demonstrates that in the case of highly and moderately virulent virus variants the virulence does not affect the pattern of the viral spread, however, it influences the outcome, the duration and the intensity of the disease. Immunohistochemistry has the advantage to allow the rapid detection and localisation of the virus, especially in cases of early infection, when clinical signs are still absent. Compared to virus isolation, the advantage of this method is that no cell culture facilities are required. Thus, immunohistochemistry provides simple and sensitive tools for the prompt detection of newly emerging variants of CSFV, including the viruses of very mild virulence.</p

Emergence of Fatal PRRSV Variants: Unparalleled Outbreaks of Atypical PRRS in China and Molecular Dissection of the Unique Hallmark

Porcine reproductive and respiratory syndrome (PRRS) is a severe viral disease in pigs, causing great economic losses worldwide each year. The causative agent of the disease, PRRS virus (PRRSV), is a member of the family Arteriviridae. Here we report our investigation of the unparalleled large-scale outbreaks of an originally unknown, but so-called “high fever” disease in China in 2006 with the essence of PRRS, which spread to more than 10 provinces (autonomous cities or regions) and affected over 2,000,000 pigs with about 400,000 fatal cases. Different from the typical PRRS, numerous adult sows were also infected by the “high fever” disease. This atypical PRRS pandemic was initially identified as a hog cholera-like disease manifesting neurological symptoms (e.g., shivering), high fever (40–42°C), erythematous blanching rash, etc. Autopsies combined with immunological analyses clearly showed that multiple organs were infected by highly pathogenic PRRSVs with severe pathological changes observed. Whole-genome analysis of the isolated viruses revealed that these PRRSV isolates are grouped into Type II and are highly homologous to HB-1, a Chinese strain of PRRSV (96.5% nucleotide identity). More importantly, we observed a unique molecular hallmark in these viral isolates, namely a discontinuous deletion of 30 amino acids in nonstructural protein 2 (NSP2). Taken together, this is the first comprehensive report documenting the 2006 epidemic of atypical PRRS outbreak in China and identifying the 30 amino-acid deletion in NSP2, a novel determining factor for virulence which may be implicated in the high pathogenicity of PRRSV, and will stimulate further study by using the infectious cDNA clone technique

The M/GP5 Glycoprotein Complex of Porcine Reproductive and Respiratory Syndrome Virus Binds the Sialoadhesin Receptor in a Sialic Acid-Dependent Manner

The porcine reproductive and respiratory syndrome virus (PRRSV) is a major threat to swine health worldwide and is considered the most significant viral disease in the swine industry today. In past years, studies on the entry of the virus into its host cell have led to the identification of a number of essential virus receptors and entry mediators. However, viral counterparts for these molecules have remained elusive and this has made rational development of new generation vaccines impossible. The main objective of this study was to identify the viral counterparts for sialoadhesin, a crucial PRRSV receptor on macrophages. For this purpose, a soluble form of sialoadhesin was constructed and validated. The soluble sialoadhesin could bind PRRSV in a sialic acid-dependent manner and could neutralize PRRSV infection of macrophages, thereby confirming the role of sialoadhesin as an essential PRRSV receptor on macrophages. Although sialic acids are present on the GP3, GP4 and GP5 envelope glycoproteins, only the M/GP5 glycoprotein complex of PRRSV was identified as a ligand for sialoadhesin. The interaction was found to be dependent on the sialic acid binding capacity of sialoadhesin and on the presence of sialic acids on GP5. These findings not only contribute to a better understanding of PRRSV biology, but the knowledge and tools generated in this study also hold the key to the development of a new generation of PRRSV vaccines