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PubMed1980

Swine vesicular disease viruses isolated from healthy pigs in non-epizootic period. I. Isolation and identification.

A total of 524 fecal samples were collected from healthy swine of 36 hog farms scattered all over Japan from which had been detected neutralizing antibody against swine vesicular disease (SVD) virus. A virus was isolated from 21 of them. It was neutralized by antiserum against SVD virus. Of the 21 samples, 19 were derived from six farms, in areas which remained to be free from SVD in the past years and two from a farm where SVD broke out 18 months before. The cross-neutralization test was carried out with seven strains of SVD virus isolated from healthy pigs (SVDV-H) and five strains of SVD virus isolated from diseased pigs (SVDV-D). There was, however, no significant difference in antigenicity between the two groups. Some strains of SVDV-H were antigenically close to the Faulkner strain of Coxsackie B5 virus, and others to the freshly isolated strain of this virus. Neutralizing antibody of low titer against SVD virus was detected from pigs kept in areas free from SVD. It was presumed to have been produced in these pigs involved in silent infection with this virus.

Age Factors↗
PubMed1998

Reduction of singleton reactors against swine vesicular disease virus by a combination of virus neutralisation test, monoclonal antibody-based competitive ELISA and isotype specific ELISA.

Pigs which are serologically positive for swine vesicular disease virus (SVDV) but which show no clinical signs and for which there is neither a relevant history of the disease on the holding nor contact with a known outbreak are considered as singleton reactors. False positive serological results for an epizootic disease, like SVD, in a non-vaccinated population or in imported animals are of great concern to international trade. For the virus neutralisation test, the gold standard for SVD, singleton reactors are found at a level of 1-3/1000. Singleton reactors also occur when other serological testing methods are used. The number of animals finally considered as singleton reactors can be reduced considerably by performing three different serological tests (virus neutralisation test, monoclonal antibody-based competitive ELISA and isotype specific ELISA) on the same serum. A serological profile of the animal can be derived by analysing the results in greater detail. This procedure can reduce considerably the number of pig holdings on which a prohibition of movement and trade needs to be imposed without requiring analysis of supplementary samples.

Animals↗
PubMed1993

Characterization of a bicistronic retroviral vector composed of the swine vesicular disease virus internal ribosome entry site.

We cloned the 5' nontranslated region (NTR) from the genome of swine vesicular disease virus (SVDV), a member of the family Picornaviridae, and used it to construct a bicistronic retroviral vector. The vector is characterized by coexpression of two genes from a single transcript. We found that inclusion of the 5' NTR of SVDV did not negate the viral vector titer. Protein analysis indicated that the 5' NTR could efficiently direct internal initiation, thus allowing the downstream gene to be translated. Translation of the internally initiated porcine growth hormone gene was about 30-fold less than that when the porcine growth hormone gene was at the upstream position in NIH 3T3 cells but was about equivalent to that in HeLa cells, implying that some cellular factors that stimulated internal initiation of the SVDV 5' NTR are present in HeLa cells. However, in G418-selected clones, the Neor-encoding gene was expressed with equivalent efficiency either at a downstream position or at an upstream position in either NIH 3T3 or HeLa cells. Compared with the conventional double-gene vector or the U3-based vector, the bicistronic vector coexpressed two genes much more efficiently, owing to elimination of promoter interference. Furthermore, this type of vector infected and expressed the target genes efficiently in two primary cell lines, rat embryo and human skin fibroblast cells, which we tested. These experimental data suggest a better design for the retroviral vector and provide evidence that internal initiation of the SVDV 5' NTR was stimulated cell specifically.

3T3 Cells↗
PubMed1976

A survey for swine vesicular disease antibody in pigs in Northern Ireland.

One thousand pig sera from Northern Ireland were tested using the radial immuno-diffusion (RID) test for antibody to swine vesicular disease (SVD) virus. Sera showing precipitation in RID were further tested by serum neutralisation (SN) and double immuno-diffusion (DID) tests. The results of the RID test showed low levels of antibody present. However, SN and DID tests did not prive the specificity of this antibody. It was concluded that the low levels of antibody detected by the RID tests were not caused by subclinical levels of SVD in the pig population in Northern Ireland.

Animals↗
PubMed2005

Sequence analysis of the 5' untranslated region of swine vesicular disease virus reveals block deletions between the end of the internal ribosomal entry site and the initiation codon.

Swine vesicular disease virus (SVDV) is a picornavirus closely related to the human pathogen coxsackievirus B5. In common with other picornaviruses, the 5' untranslated region (5' UTR) of SVDV contains an internal ribosomal entry site (IRES) that plays an important role in cap-independent translation. The aim of this study was to use RT-PCR and sequencing to characterize a fragment of the 5' UTR encompassing the entire IRES. Sequence analysis demonstrated high nucleotide identities within the IRES between 33 representative SVDV isolates. These data support the choice of this region as a diagnostic target and provide information for the improvement of laboratory-based molecular assays to detect SVDV. In contrast to the relative conservation of the IRES element, there was considerable nucleotide variability in the spacer region located between the cryptic AUG at the 3' end of the IRES and the initiation codon of the polyprotein. Interestingly, 11 SVDV isolates had block deletions of between 6 and 125 nt in this region. Nine of these isolates were of recent European origin and were phylogenetically closely related. In vitro growth studies showed that selected isolates with these deletions had a significantly reduced plaque diameter and grew to a significantly lower titre relative to an isolate with a full-length 5' UTR. Further work is required to define the significance of these deletions and to assess whether they impact on the pathogenesis of SVD.

5' Untranslated Regions↗
PubMed2002

In vivo studies on cytokine involvement during acute viral respiratory disease of swine: troublesome but rewarding.

The early cytokines interferon-alpha (IFN-alpha), tumour necrosis factor-alpha (TNF-alpha), interleukin-1, -6 and -8 (IL-1, -6, -8) are produced during the most early stage of an infection. The activities of these cytokines have been studied extensively in vitro and in rodents, but in vivo studies on the role of these cytokines in infectious diseases of food animals are few. This review concentrates on in vivo studies of cytokine involvement in infectious respiratory diseases of swine, with an emphasis on viral infections. First evidence for the role of early cytokines in pneumonia in swine came from experimental infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae. The role of TNF-alpha and IL-1 in the symptoms and pathology of porcine pleuropneumonia has recently been proven by use of an adenovirus vector expressing the anti-inflammatory IL-10. In the authors' laboratory, studies were undertaken to investigate the relationship between viral respiratory disease and bioactive lung lavage levels of IFN-alpha, TNF-alpha, IL-1 and IL-6. Out of three respiratory viruses-porcine respiratory coronavirus (PRCV), porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza virus (SIV)-only SIV induced acute respiratory disease and severe lung damage by itself. Disease and lung pathology were tightly associated with the simultaneous production of IFN-alpha, TNF-alpha, IL-1 and IL-6. In challenge studies of SIV-vaccinated pigs, levels of IFN-alpha, TNF-alpha and IL-6, but not IL-1 were correlated with clinical and virological protection. Multifactorial respiratory disease was reproduced by combined inoculations with PRCV or PRRSV followed by LPS from Escherichia coli. In comparison with the respective single inoculations, which were subclinical, there was a true potentiation of disease and production of TNF-alpha, IL-1 and IL-6. TNF-alpha and IL-6 were best correlated with disease. In further studies, we will use more specific strategies to dissect the role of cytokines during viral infections.

Acute Disease↗
PubMed1978

[Possible methods of control of virus disease in swine today and in the future. II. Specific applications (author's transl)].

The four alternatives discussed in the previous paper (5), are applied to a number of virus infections which are common in pigs. The enzootic state of SMEDI enteroviruses, vomiting and wasting virus and parvovirus should be promoted by bringing the young gilts into close contact with the older sow population at a sufficiently early stage. There should preferably not be a change of herd for primiparous sows during pregnancy. In parvovirus infection, maternal immunity may be so prolonged that gilts will only be infected after the time of breeding. Therefore, mating should preferably be postponed until they are nine months of age, unless previous serological tests have shown that they are in a state of active immunity. Considering the present disease situation of swine fever in several continental West European countries and consequently they high number of existing virus sources, compulsory vaccination of sows and fattening piglets is recommended against this virus on an international scale for at least three years. This vaccination can be omitted only after the number of outbreaks has been reduced to a very low level. Vaccination is the only possible alternative left in the combat against Aujezky's disease. Caution is undoubtedly indicated in using live vaccines in these cases. So far, methods have not become available for the effective control of transmissible gastroenteritis and prospects are not encouraging. The possibility of eradication of transmissible gastroenteritis is discussed.

Animals↗
PubMed1998

Viruses produced from complementary DNA of virulent and avirulent strains of swine vesicular disease viruses retain the in vivo and in vitro characteristics of the parental strain.

A full-length cDNA copy of the genome of the pathogenic strain, J1'73, of swine vesicular disease virus (SVDV) was constructed and inserted into the plasmid pSVL to generate a recombinant plasmid pSVLSJ1. Infectious virus was produced following transfection of cultured mammalian cells with the plasmid. The recovered virus had the same in vitro properties as the parental strain with regard to antigenicity, plaque size on IBRS-2 cells and single-step growth. Pigs were experimentally infected with the parental virus, J1'73 strain, and viruses recovered from cells transfected with the plasmids pSVLSJ1 and pSVLS00 [Inoue T, Yamaguchi S, Saeki T, Sekiguchi K, J Gen Virol 71: 1,835-1,838 (1990)] corresponding to the pathogenic (J1'73) and non-pathogenic (H/3'76) Japanese strains of the SVDV, respectively. All pigs inoculated with the virus recovered from pSVLSJ1 produced clinical signs of similar severity to those inoculated with the parental J1'73 strain. In contrast, pigs inoculated with the virus recovered from pSVLS00 did not show any clinical signs. Viruses recovered from cells transfected with either pSVLSJ1 or pSVLS00 therefore retained the in vitro characteristics and the in vivo pathogenicity of their respective parental strains.

Animals↗
PubMed1995

Pathogenesis of foot-and-mouth disease in swine, studied by in-situ hybridization.

Eight 7-month-old pigs were inoculated intradermally with 10(3) plaque-forming units of foot-and-mouth disease virus, type O, and killed 24, 48, 72, or 96 h later. Numerous tissues from each animal were collected and examined histopathologically and by in-situ hybridization to determine the presence of virus and its correlation with lesion development. The probe for in-situ hybridization was a biotinylated 500-base negative-sense transcription product corresponding to a portion of the gene encoding polymerase. With this technique, virus was shown to be widely disseminated in all epidermal tissues, regardless of histologically apparent cellular disruption.

Animals↗
PubMed2005

Noninfectious virus-like particle antigen for detection of swine vesicular disease virus antibodies in pigs by enzyme-linked immunosorbent assay.

An inactivated SVDV antigen is used in current enzyme-linked immunosorbent assays (ELISAs) for the detection of antibodies to swine vesicular disease virus (SVDV). To develop a noninfectious recombinant alternative, we produced SVDV-like particles (VLPs) morphologically and antigenically resembling authentic SVDV particles by using a dual baculovirus recombinant, which expresses simultaneously the P1 and 3CD protein genes of SVDV under different promoters. Antigenic differences between recombinant VLPs and SVDV particles were not statistically significant in results obtained with a 5B7-ELISA kit, indicating that the VLPs could be used in the place of SVDV antigen in ELISA kits. We developed a blocking ELISA using the VLPs and SVDV-specific neutralizing monoclonal antibody 3H10 (VLP-ELISA) for detection of SVDV serum antibodies in pigs. The VLP-ELISA showed a high specificity of 99.9% when tested with pig sera that are negative for SVDV neutralization (n=1,041). When tested using sera (n=186) collected periodically from pigs (n=19) with experimental infection with each of three different strains of SVDV, the VLP-ELISA detected SVDV serum antibodies as early as 3 days postinfection and continued to detect the antibodies from all infected pigs until termination of the experiments (up to 121 days postinfection). This test performance was similar to that of the gold standard virus neutralization test and indicates that the VLP-ELISA is a highly specific and sensitive method for the detection of SVDV serum antibodies in pigs. This is the first report of the production and diagnostic application of recombinant VLPs of SVDV. Further potential uses of the VLPs are discussed.

Animals↗
PubMed1999

Molecular evolution of swine vesicular disease virus.

Phylogenetic analysis was used to examine the evolutionary relationships within a group of coxsackie B viruses that contained representatives of the major serotypes of this group and 45 isolates of swine vesicular disease virus (SVDV) from Asia and Europe. Separate analyses of sequence data from two regions of the viral genomes encoding the VP1 and 3BC genes both revealed that the SVDV belonged to a single monophyletic group which could be clearly distinguished from all other sampled coxsackieviruses. Regression analysis revealed that within the SVDV clade at least 80% of the synonymous variation in evolutionary divergence between isolates was explained by time, indicating the existence of an approximate molecular clock. Calibration of this clock according to synonymous substitutions per year indicated the date of occurrence of a common ancestor for the SVDV clade to be between 1945 and 1965.

Amino Acid Substitution↗
PubMed2001

An attenuating mutation in the 2A protease of swine vesicular disease virus, a picornavirus, regulates cap- and internal ribosome entry site-dependent protein synthesis.

Virulent and avirulent strains of swine vesicular disease virus (SVDV), a picornavirus, have been characterized previously. The major determinants for attenuation have been mapped to specific residues in the 1D-2A-coding region. The properties of the 2A proteases from the virulent and avirulent strains of SVDV have now been examined. Both proteases efficiently cleaved the 1D/2A junction in vitro and in vivo. However, the 2A protease of the avirulent strain of SVDV was much less effective than the virulent-virus 2A protease at inducing cleavage of translation initiation factor eIF4GI within transfected cells. Hence the virulent-virus 2A protease is much more effective at inhibiting cap-dependent protein synthesis. Furthermore, the virulent-virus 2A protease strongly stimulated the internal ribosome entry sites (IRESs) from coxsackievirus B4 and from SVDV, while the avirulent-virus 2A protease was significantly less active in these assays. Thus, the different properties of the 2A proteases from the virulent and avirulent strains of SVDV in regulating protein synthesis initiation reflect the distinct pathogenic properties of the viruses from which they are derived. A single amino acid substitution, adjacent to His21 of the catalytic triad, is sufficient to confer the characteristics of the virulent-strain 2A protease on the avirulent-strain protease. It is concluded that the efficiency of picornavirus protein synthesis, controlled directly by the IRES or indirectly by the 2A protease, can determine virus virulence.

Animals↗