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Biomedical subjects

B I Osburn

Publications and source records attributed to B I Osburn.

At least 19 recordsLinked to original sources
PubMed1992

Variation amongst the neutralizing epitopes of bluetongue viruses isolated in the United States in 1979-1981.

Neutralizing epitopes present on field isolates of bluetongue virus (BTV) serotypes 10, 11, 13 and 17 were evaluated with a panel of polyclonal and neutralizing monoclonal antibodies (MAbs). A total of 91 field isolates were evaluated, including 15 isolates of BTV-10, 29 isolates of BTV-11, 26 isolates of BTV-13, and 21 isolates of BTV-17. The viruses were isolated from cattle, goats, sheep, elk and deer in Idaho, Louisiana, Nebraska and, predominantly, California, in the years 1979, 1980 and 1981. The isolates were analyzed and compared using a panel of neutralizing MAbs which included five MAbs raised against BTV-2, seven against BTV-10, five against BTV-13, and six against BTV-17. Neutralization patterns obtained with the MAb panel and individual field isolates were compared to those obtained with prototype viruses of each serotype. All field isolates were neutralized by at least some of the MAbs raised against the prototype virus of the same serotype. All field isolates of BTV-10 were neutralized by the seven MAbs raised to BTV-10, whereas the field isolates of BTV-11, BTV-13 and BTV-17 were not consistently neutralized by all of the MAbs raised against the prototype virus of the same serotype. Variation in neutralizing epitopes recognized by the MAb panel was most pronounced amongst the field isolates of BTV-17. A one-way cross neutralization was evident between BTV-10 and BTV-17 as all field isolates of BTV-17 were neutralized by four of the MAbs raised against BTV-10. In contrast, no BTV-10 isolates were neutralized by the MAbs raised against BTV-17. Differences in the MAb neutralization patterns of field isolates of BTV-11, BTV-13 and BTV-17 suggest that the immunogenic domain responsible for their neutralization is plastic, such that individual epitopes within the domain may vary in their significance to the neutralization of different viruses, even of the same serotype. The apparent conservation of neutralizing epitopes on field isolates of BTV-10 suggests that the field isolates may be derived from the modified-live vaccine strain of BTV-10.

Animals↗
PubMed1992

Hybridization relatedness of Israeli and U.S. bluetongue (BLU) serotypes using cDNA probes from BLU virus strain 11-UC8.

Partial cDNA clones representing 47%, 96%, and 98% of genome segments 7, 9, and 10, respectively, of a US bluetongue virus (BLU) 11 virulent strain were used to study, for the first time, the genetic relationships between Israeli BLU proto-serotypes and field isolates, and US BLU proto-serotypes. Their usefulness as group-specific identification probes was also determined. The viral nucleic acid was extracted from the infected cells and the purified dsRNA genome segments were fractionated by polyacrylamide gel electrophoresis, transferred to a nylon membrane and hybridized to the 32P labeled DNA probes. The three probes recognized all the samples tested. Genome segment 7, that code for the mayor inner capsid protein VP7, showed the most variation in the hybridization signal with the US proto-serotypes and all the Israeli samples studied. The genome segments 9 and 10 that code for the minor inner capsid protein VP6 and the nonstructural protein NS3, respectively, were highly conserved in all the samples tested despite their distant geographical regions of origin. The last two mentioned clones showed to be good group-specific probes for the identification of BLU samples from Israel and United States. The obtained cloned genetic probes were also tested against US epizootic haemorrhagic disease virus (EHDV) serotype 1 and 2 viral dsRNA, a distantly related orbivirus. None of them hybridized with the viral dsRNA of these two viruses.

Animals↗
PubMed1992

Association of virulent and avirulent strains of bluetongue virus serotype 11 with premature births of late-term bovine fetuses.

Two strains of bluetongue virus serotype 11 (BTV 11), UC-2 avirulent and UC-8 neurovirulent in newborn mice, were inoculated into late-term bovine fetuses to investigate whether infection with these two BTV strains in late gestation would produce congenital infection and pathological changes. Fetuses were inoculated by intramuscular injection through the uterine wall at 243 days gestation and recovered after spontaneous delivery. In calves inoculated with UC-8, births occurred 15 to 27 days before expected parturition, resulting in small, weak calves. These calves had a mild encephalitis and were unthrifty at birth. Calves inoculated with UC-2 appeared healthy when born 7 to 11 days prior to expected parturition. No lesions were found in these calves at necropsy. All calves seroconverted by the time of birth. Viraemia was present in the calves inoculated with UC-8 and in one calf inoculated with UC-2. Plasma cortisol concentrations were prematurely elevated, particularly in the calves inoculated with UC-8, indicating that they were stressed by the infection. The elevated cortisol, associated with an active congenital infection caused by bluetongue virus serotype 11 strain UC-8, is capable of causing premature delivery of low birth-weight, weak calves.

Animals↗
PubMed1992

An experimental contribution to the study of the pathogenesis of bovine viral diarrhea virus infection.

This presentation summarizes the results of a study on the pathogenesis of bovine viral diarrhea (BVDV) infection. The cytopathic (CP) strain TVM-2 of BVDV induced in calves an overt clinical disease which is usually recorded as the acute primary BVDV infection observed under natural conditions. In contrast the non-cytopathic (NCP) strain New York-1 of BVDV did not cause any significant signs of disease. However, when the calves were immunosuppressed by treatment with dexamethasone (DMS) the biotype of BVDV involved did not seem to be as important as it appeared to be in an immunologically normal animal. This was shown in this study by the NCP BVDV which caused a fatal disease in calves treated with DMS. A mixed infection given to calves by injecting them with both CP and NCP BVDV, did not result in any particularly serious disease. So, the potential immunosuppressive activity of BVDV itself for the host has not been proven under the experimental procedures used in this experiment. Finally, a modified-live CP BVDV vaccine was unable to cause clinical disease when injected into calves that had been infected previously with strain New York-1 of BVDV.

Animals↗
PubMed1992

Infection of bovine fetuses at 120 days' gestation with virulent and avirulent strains of bluetongue virus serotype 11.

Bluetongue virus infection in sheep and cattle during fetal development causes neuropathology. Two strains of bluetongue virus serotype 11 designated as UC-2 and UC-8 have different virulence patterns in newborn mice. These viruses have distinctly different electropherotype patterns on polyacrylamide gel electrophoresis indicating a genetic difference in these two viruses of the same serotype. Four bovine fetuses each were inoculated intramuscularly with either UC-2 or UC-8, and one fetus was inoculated with placebo. The inoculation was made intramuscularly through the uterine wall at 120 days' gestation, and the bovine fetuses were recovered by cesarean section 12 or 20 days after inoculation. Fetal blood was collected for virus isolation and serology. Virus was reisolated from brain, blood, lung and liver. Both strains, UC-2 and UC-8, cause severe lesions in the 120 day fetuses. The encephalomalacic lesions occurred earlier and were more severe in fetuses inoculated with UC-8 as compared to those inoculated with UC-2. The subtle differences observed in the fetuses inoculated with the two different strains suggest that there is a difference in pathogenic potential of the two viruses. These differences do not appear to be completely dependent upon the host species.

Animals↗
PubMed1992

Detection of bluetongue virus using a cDNA probe derived from genome segment 4 of bluetongue virus serotype 2.

The double-stranded (ds) RNA genome segment 4 of bluetongue virus (BTV) serotype 2 was cloned and used as a serogroup-specific complementary (c) DNA probe for BTV diagnosis. A cDNA representing a 60% copy of genome segment 4 BTV-2 prototype was produced. The specificity of the cDNA probe was determined by hybridizing this probe to a northern blot of dsRNA (separated by polyacrylamide gel electrophoresis) of plaque-purified BTV-2 prototype. This cDNA probe was then used to hybridize to the RNA samples. Because the probe hybridized to all BTV samples but not to epizootic hemorrhagic disease virus samples, it appears to be a group-specific probe that could be used in BTV diagnosis.

Animals↗
PubMed1992

Detection of bluetongue virus serogroup by polymerase chain reaction.

To facilitate detection of active bluetongue virus (BTV) infection, a polymerase chain reaction (PCR) protocol was developed. The BTV reverse transcriptase PCR (RT-PCR) is a 1-tube reaction and involves chemical denaturation of the double-stranded viral RNA target, a complementary DNA (cDNA) synthesis step, and PCR amplification of the cDNA. BTV RT-PCR using primers derived from highly conserved genome segment 10 results in a 251-base pair (bp) product. BTV RNA from all USA prototype serotypes 2, 10, 11, 13, and 17; a wide spectrum of USA BTV field isolates including serotypes 10, 11, 13, and 17; and a spectrum of Israeli field isolates including serotypes 2, 4, 6, 10, and 16 were detected by BTV RT-PCR. With agarose gels, the 251-bp product was detected from as little as 100 fg-1 pg of BTV RNA, which is equivalent to 5 x 10(3)-5 x 10(4) viral particles or 5 x 10(2)-5 x 10(3) infectious units. With dot blot hybridization, specific PCR product was detected from as little as 1 fg of BTV RNA, which is equivalent to 50 viral particles, or 5 infectious units. This level of sensitivity is comparable to that of virus isolation. The BTV RT-PCR using primers derived from genome segment 10 can detect a wide spectrum of USA and Israeli BTV serotypes and has potential for detection of infection by the BTV serogroup. Application of this BTV PCR to clinical samples is in progress.

Base Sequence↗
PubMed1992

Analysis of genetic variation of epizootic hemorrhagic disease virus and bluetongue virus field isolates by coelectrophoresis of their double-stranded RNA.

Thirty-two bovine field isolates of bluetongue virus (BTV), 6 field isolates of epizootic hemorrhagic disease virus (EHDV) from deer, 4 BTV prototype serotypes (10, 11, 13, and 17), and 2 EHDV prototype serotypes (1 and 2) were coelectrophoresed, using polyacrylamide gels. Field isolates were obtained from various regions of the United States. Analysis of polyacrylamide gels and scattered plots generated for comparison of migration patterns for different isolates within each serotype of BTV revealed wide variation among the individual segments. The BTV serotypes 10 and 11 had more variation, compared with BTV serotypes 13 and 17, especially for migration of genome segment 5. A definitive correlation was not seen between the double-stranded RNA migration profiles on polyacrylamide gel electrophoresis, geographic origin, herd of origin, or year of collection. One BTV field isolate contained more than 1 electropherotype, with 2 bands at the segment-7 position, and it was further characterized as BTV serotype 11. Segments 2 and 5 of EHDV isolates were more variable in their migration than were the other gene segments. Generally, migration profiles for EHDV double-stranded RNA were more variable, compared with those of BTV isolates. Although a correlation was found between migration profiles and serotype of 2 isolates of EHDV, a study of additional EHDV isolates is required before the diversity of electrophoretic patterns of EHDV can be determined.

Animals↗
PubMed1992

Comparison of slot blot nucleic acid hybridization, immunofluorescence, and virus isolation techniques to detect bluetongue virus in blood mononuclear cells from cattle with experimentally induced infection.

A slot blot hybridization technique was applied for detection of bluetongue virus (BTV) in blood mononuclear cells (BMNC) obtained from cattle with experimentally induced infection. This technique lacked sensitivity to detect the viral nucleic acid directly in clinical specimens. When aliquots of mononuclear cells from these cattle were cultivated in vitro for 10 days to amplify virus titer, only 33.3% of the samples collected during viremia gave a positive signal in the slot blot hybridization format. By contrast, results for 34.3% of noncultured and 63.3% of cultured mononuclear cell samples collected during viremia were positive by immunofluorescence. The average number of infected cells, as detected by immunofluorescence in the noncultured mononuclear cell samples, was 1 to 5/300,000, and was usually > 10/300,000 in the cultured cell samples. Virus was isolated from all postinoculation blood samples obtained from 4 heifers that were seronegative at the time of inoculation, but was not isolated from any of the preinoculation samples, or from any of the postinoculation samples obtained from 2 heifers that were seropositive at the time of inoculation. When virus isolation was attempted from separated mononuclear cells in 2 heifers, 43.7% of the noncultured and 87.5% of the cultured samples had positive results.

Animals↗
PubMed1991

Expression of a full-length nonstructural protein NS1 of bluetongue virus serotype 17 in Escherichia coli.

The relative abundance of the nonstructural protein NS1 in bluetongue virus (BTV)-infected cells, the existence of NS1 in the BTV particles and the highly conserved NS1 gene among BTV serotypes indicate the diagnostic potential of using NS1 in detecting BTV infections. In this study a NS1 gene was expressed with the T7 RNA polymerase expression system to produce a full-length NS1 protein. Sheep anti-NS1 antibodies were raised with the E. coli-produced NS1 and used to show that the NS1 proteins of the five BTV serotypes in the Unites States were immunologically indistinguishable.

Animals↗
PubMed1991

Genetic variation and evolutionary relationships amongst bluetongue viruses endemic in the United States.

The genetic variation and evolutionary relationships amongst the five serotypes of bluetongue virus (BTV) endemic to the United States were investigated by oligonucleotide fingerprint analysis. The viruses analyzed include prototype viruses of the five U.S. serotypes, and 32 viruses isolated from domestic and wild ruminants from the U.S. in the years 1979-1981. With the exception of serotype 2, most genes encoding the viral core and non-structural proteins were demonstrated to be highly conserved both within and between serotypes and some also appear to have reassorted in nature. Gene segments 2 and 6, which encode the outer capsid proteins VP2 and VP5 respectively, were more variable and were not consistently linked as serotype determination was dependent solely on gene segment 2. Gene segment 2 was the most variable gene between serotypes, but it was highly conserved within serotypes and stable over time. This suggests that the emergence of new BTV serotypes, which would require the stable incorporation of numerous mutations, must be a very slow process. Fingerprint comparisons further suggested that BTV serotypes 10, 11, 13 and 17 have evolved together in the U.S. over a considerable period of time, whereas serotype 2, which is genetically distinct, has evolved elsewhere and is most likely a recent introduction to North America.

Animals↗
PubMed1991

Integrated bovine leukosis proviral DNA in T helper and T cytotoxic/suppressor lymphocytes.

Bovine leukosis virus (BLV) is associated with the disease complex enzootic bovine leukosis. The infection may remain clinically silent in the form of an aleukaemic state or emerge as a persistent lymphocytosis and more rarely as lymphosarcroma. BLV has been considered classically to be a B lymphotropic virus, based upon the absolute increase in B lymphocytes in persistent lymphocytosis, the B lymphocyte phenotype of a majority of the cells making up lymphosarcomas and the identification of viral antigen expressed in B lymphocytes following in vitro culture of peripheral blood mononuclear leukocytes. This association of BLV with B lymphocytes is well established but the mechanism(s) of disease expression is not defined. To examine further the cellular tropism(s) of BLV, T lymphocyte subpopulations from 10 lymphocytotic cattle were established in vitro. Lymphocyte cultures were characterized by their subpopulation phenotype and DNA was extracted for identification of integrated provirus by Southern blot hybridization. Provirus was identified in T lymphocyte cultures derived from seven of 10 lymphocytotic cattle, with both T helper and T cytotoxic/suppressor subpopulations affected.

Animals↗
PubMed1991

Role of eicosanoids in abortion and its prevention by treatment with flunixin meglumine in cows during the first trimester of pregnancy.

Intravenous infusion of E. coli endotoxin at a rate of 4.16 ng/kg/min over 6 hr (total dose 1.5 micrograms/kg) in 5 cows in the first trimester of gestation induced abortion between 60 and 72 hr in three cows. Plasma PGF2 alpha levels in the aborting cows increased significantly to 289% of the zero time control (ZTC) at 1 hr and remained elevated for 9 hr. The PGF2 alpha level remained unaffected in the non-aborting cows except at 2 hr. The plasma TxB2 levels were increased by 6 to 18 fold for 6 hr in both the aborting and non-aborting cows relative to their ZTC controls. The 6-keto-PGF1 alpha levels were significantly increased to 2 to 3 fold only in the aborting cows. Plasma cortisol levels were increased maximally to 1,500% of ZTC at 5 hr in the aborting cows. Thereafter, the levels gradually declined but remained significantly elevated for 24 hr. The increases in the cortisol levels in the non-aborting cows were only 280% of ZTC at 5 hr and returned to ZTC value by 12 hr. Plasma progesterone levels in the aborting cows remained unaffected until 12 hr followed by a progressive decline through 18 hr to extremely low levels at 3, 4, and 5 days. Endotoxin-infusion caused hyperglycemia in both aborting and non-aborting cows and lactic acidemia in the aborting cows. Treatment with two doses of flunixin meglumine (FM, 1.1 mg/kg), an inhibitor of cyclooxygenase, 1 hr prior to endotoxin infusion and then 13 hr later, completely prevented the endotoxin-induced abortion and increases in the plasma PGF2 alpha, TxB2 and 6-keto-PGF1 alpha concentrations. The PGE level remained unaffected. Although FM treatment failed to abolish endotoxin-induced increases in the plasma cortisol and lactic acid levels, it effectively prevented marked decreases in the progesterone and increases in the glucose concentrations. It was concluded that the use of FM offers therapeutic promise in preventing bovine abortion caused by endotoxin resulting from bacterial infection during the 1st trimester of gestation.

Abortion, Veterinary↗
PubMed1991

Evidence of genome segment 5 reassortment in bluetongue virus field isolates.

A recombinant cDNA probe from genome segment 5 obtained from a virulent US bluetongue virus strain (BTV-11 strain UC8) was hybridized to US and Israeli BTV prototypes and field isolates. The cloned genetic probe hybridized with US BTV prototype 10, but not with US prototypes 2, 11, 13, and 17; with the avirulent BTV-11 strain UC2; and with the Israeli prototype 10. When the probe was hybridized to field isolates from the US serotypes, it hybridized to 12 of 14 BTV-10 isolates and 4 of 17 BTV-11 samples, but not to the BTV-13 and BTV-17 samples tested. Hybridization was not observed with the Israeli field isolates studied. Results indicate that a reassortant event occurred between a strain of US BTV-10 and US BTV-11 that originated the BTV-11 strain UC8.

Animals↗