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[Virus diseases].

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Acyclovir↗

Growth of Newcastle disease virus and rubella virus in rheumatoid and nonrehumatoid synovial cell cultures.

Rheumatoid and nonrheumatoid synovial cell cultures were challenged with Newcastle disease virus and rubella virus in an attempt to confirm reports that rheumatoid synovial cells are relatively resistant to infection with these viruses. Newcastle disease virus caused complete cell destruction by day 7 in both rheumatoid and nonrheumatoid cultures, and peak virus titers were similar. Rubella virus replicated in both rheumatoid and nonrheumatoid synovial cell cultures, and no consistent differences in virus titers were detected. Rubella-infected cell lines were observed for up to 28 days and no virus-specific cytopathic effect was seen.

Adolescent↗

Selection and characterization of RNA aptamers to the RNA-dependent RNA polymerase from foot-and-mouth disease virus.

Foot-and-mouth disease virus causes a highly contagious disease of agricultural livestock and is of enormous economic importance. Replication of the RNA genome of the virus, via negative strand intermediates, involves an RNA-dependent RNA polymerase (3Dpol). RNA aptamers specific to this enzyme have been selected and characterized. Some of these molecules inhibit enzymatic activity in vitro, with IC50 values of <20 nM and Ki values of 18-75 nM. Two of these show similarity, both with each other and with regions of the viral genome. Furthermore, truncated versions of one of the aptamers have been used to define the parts of the molecule responsible for its inhibitory activity.

Aptamers, Nucleotide↗

Primer design for specific diagnosis by PCR of highly variable RNA viruses: typing of foot-and-mouth disease virus.

A PCR assay for the specific detection and identification of viral sequences that correlate with established serotypes of foot-and-mouth disease virus (FMDV) has been developed. A new analysis based on homology profiles among reported sequences was used for primer design. RNA replicase (3D) gene regions that showed high homology among FMDVs, and low homology to other picornaviruses, were used for PCR amplification. Specific and highly sensitive detection was achieved for RNA of FMDV types C, A, and O, either purified or extracted from vesicular fluids of infected animals, under reaction conditions permissive for the detection of variants present in the virus population. Similarly, serotype-specific primers were designed to amplify the carboxy-terminal end of VP1 gene of FMDV types either C, A, or O. The results of PCR amplification of 15 different FMDV RNAs using type-specific primers are in agreement with the serological typing of the corresponding viruses and show that the primer-selection procedure developed for FMDV constitutes a reliable method of viral diagnosis.

Animals↗

[Biological characteristics of the plaque variants of the swine vesicular disease virus].

The Swine Vesicular Disease virus yields a heterogenic plaque population consisting of large round plaques of 8-10 mm, small uniform plaques with slightly indented contours, measuring 1-3 mm, and single plaques of transient form and size. The reisolates of the large (Lpf) plaques give a population that is similar to the initial virus, while the cloning of the small (Mpf) plaques leads to a homogenic population of such plaques. In vivo, the virus of the large plaques manifests enhanced virulence for swine. On the other hand, the selected small-plaque variant is apathogenic, which makes it possible to produce a live avirulent vaccine.

Animals↗

Metabolic requirements for the development of hemadsorption activity and virus formation in BHK-21 cells infected with Newcastle disease virus.

Differential effect of various metabolic inhibitors on the development of hemadsorption activity and virus formation in cells infected with Newcastle disease virus (NDV) was investigated. It was found that, in BHK-21 cells infected with NDV, cycloheximide did not prevent the development of hemadsorption activity, whereas protein synthesis and virus formation by the cell were rapidly inhibited by the drug. When the drug was added to the culture at 4.5 h after infection or later, hemadsorption activity of the cell continued to develop normally for about 1 h. Similar increase in hemadsorption activity was found in cells which were treated with anti-NDV serum (to neutralize their hemadsorption activity) and then washed and incubated with cycloheximide. However, when cells were treated with the drug early in the infection (1.5 or 3.0 h), they did not show any detectable hemadsorption reaction throughout the infection. In contrast to cycloheximide, iodoacetate added to the culture together with sodium azide inhibited completely both the development of hemadsorption activity and the formation of progeny virus. These results suggest that the change of cell surface to become hemadsorptive may depend upon the energy generating system but not upon de novo synthesis of protein, whereas production of infectious virus may require continuous synthesis of protein.

Animals↗

Demonstration of heavy and light density populations of Aleutian disease virus.

A highly purified and concentrated suspension of aleutian disease virus was prepared from large quantities of early infected mink tissues using repeated fluorocarbon extraction procedures. Equilibrium centrifugation of the aleutian disease virus preparation in a cesium chloride gradient yielded three distinct bands at buoyant densities of 1.295, 1.332, and 1.405--1.416 g/cm(3). Electron microscopic observations of these three bands revealed mainly empty particles in the first band. In the second band complete particles with a flattened appearnce predominated and there were also some empty particles. In the third band both complete and empty particles were observed. The size of the aleutian disease virus particles observed in all of the three densities was 23 nm. Light aleutian disease virions (density of 1.332 g/cm3) had a particle to counterimmunoelectrophoresis antigen ratio comparable to that of dense aleutian disease virions (density of 1.405--1.416 g/cm3) but possessed much lower infectivity as determined by mink inoculation.

Aleutian Mink Disease↗

Analysis of intratypic variation evident in an Ibaraki virus strain and its epizootic hemorrhagic disease virus serogroup.

A new strain of Ibaraki virus (IBAV) was isolated from cattle showing atypical symptoms of Ibaraki disease. The isolate was genetically characterized, and the genetic diversity and evolution of the capsid proteins of viruses in the epizootic hemorrhagic disease virus (EHDV) serogroup were investigated. The nucleotide sequences of the isolate's viral RNA segments 2, 3, 6, and 7, which encode the viral structural proteins VP2, VP3, VP5, and VP7, respectively, were determined and were then compared against those of the existing strains of IBAV and EHDV, to which IBAV belongs serologically. The nucleotide sequences of segments 3 and 7 were conserved within the EHDV serogroup, particularly well among the strains of IBAV and Australian EHDV. The similarity of the sequence of segment 6 of the isolate to sequences of corresponding segments of the other strains of IBAV and EHDV was found to be about 93%. The similarity of segment 2 of the isolate to segments 2 of the other strains of IBAV and EHDV was less than 70%. Phylogenetic analysis based on the deduced amino acid sequences of segments 3 and 7 revealed that the viruses differed according to their geographical distributions. However, the new isolate of IBAV was categorized as having a distinct lineage in the phylogenetic tree of VP2. These results suggest that the isolate was modified by a reassortment of segment 2 and that it exhibits unique genetic and antigenic characteristics.

Animals↗

Systemic and local antibody responses to infectious bronchitis virus in chickens inoculated with infectious bursal disease virus and control chickens.

Serum and local (respiratory) antibody responses to infectious bronchitis virus (IBV) were studied in 5-wk-old white leghorn-type control chickens and chickens inoculated with infectious bursal disease virus (IBDV) at 1 day of age. Of the chickens inoculated with IBV alone, 93% had detectable levels of IBV antibodies in the sera and 87% had detectable antibodies in the respiratory lavage fluids. Compared to this group, only 73% and 65% of IBDV-IBV inoculated chickens had serum and respiratory antibodies, respectively. In chickens inoculated with IBV alone, the IBV antibodies were evenly associated with immunoglobulin classes IgM, IgG, and IgA, whereas the IBDV-IBV inoculated chickens mainly produced IgM-associated antibodies with low to negligible levels of IgA- and IgG-associated antibodies. These results suggest that the lack of adequate IgA- and IgG-associated antibody production in IBDV-infected chickens may account for their increased susceptibility to IBV infection.

Animals↗

Severe outbreak of disease in the southern chamois (Rupicapra pyrenaica) associated with border disease virus infection.

An outbreak of a previously unreported disease affecting southern chamois (Rupicapra pyrenaica) in the central Pyrenees (NE Spain) was recorded in 2001 and 2002. There was a marked temporal distribution, most animals being found between February and June. After the outbreak, the population was found to have decreased by about 42%, most probably due to the disease. We examined 20 affected chamois. Clinical manifestations included depression, weakness and movement difficulties in all cases. Three chamois presented abnormal behaviour, with absence of flight reaction, and 16 showed different degrees of alopecia with skin hyperpigmentation. At necropsy cachexia was observed in all animals, four chamois had abscesses in different parts of the body, four had pneumonia, one had an extensive subcutaneous infection on the head and neck and one had severe orchitis. Microscopic lesions were found in the brain, mainly edema, gliosis, espongiosis, cariorrexis and neuronal multifocal necrosis. A perivascular mononuclear inflammatory infiltrate was present in three of them. Skin lesions included marked follicular atrophy, mild to moderate epidermal hyperplasia with orthokeratotic hyperkeratosis and follicular hyperkeratosis, and hypermelanosis. In 13 chamois there were haemosiderin deposits in the spleen, and in three individuals kidney "cloissone" was observed. Intraeritrocitic parasites were detected either by direct observation or PCR in 8 of 17 chamois. A pestivirus was isolated and detected by RT-PCR from 12 of 13 affected chamois and antigenic characterized as border disease virus by monoclonal antibodies. This is the first time a border disease virus has been associated with an outbreak of a high-mortality disease in a wild species.

Animals↗