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Abstract

Objective

To evaluate clearance of the vaccine strain, immunologic responses, and potential shedding of Brucella abortus strain RB51 organisms after vaccination of bison calves.

Animals

Fourteen 7-month-old female bison calves.

Procedure

10 bison calves were vaccinated SC with 1.22 × 1010 colony-forming units of B abortus strain RB51. Four bison calves were vaccinated SC with 0.15M NaCl solution. Rectal, vaginal, nasal, and ocular swab specimens were obtained to evaluate potential shedding by vaccinated bison. The superficial cervical lymph node was biopsied to evaluate clearance of the vaccine strain. Lymphocyte proliferative responses to strain RB51 bacteria were evaluated in lymph node cells obtained from biopsy specimens and also in peripheral blood mononuclear cells.

Results

Strain RB51 was recovered from superficial cervical lymph nodes of vaccinates examined 6, 12, and 18 weeks after vaccination (4/4, 3/4, and 1/4, respectively) but not in vaccinates examined at 24 weeks (0/3) after vaccination or nonvaccinates examined at all sample collection times (n = 1 bison/sample period). Serologic, immunologic, and bacterial culture techniques failed to reveal shedding of strain RB51 by vaccinates or infection of nonvaccinated bison. Lymphocyte proliferative responses were evident in lymph node cells and blood mononuclear cells from strain RB51-vaccinated bison beginning 12 weeks after vaccination.

Conclusion

Strain RB51 was cleared from bison by 18 to 24 weeks after vaccination. Bison vaccinated with strain RB51 did not shed the vaccine strain to nonvaccinated bison housed in close proximity. Strain RB51 did not induce antibody responses in bison that would interfere with brucellosis surveillance tests, but did stimulate cell-mediated immunity. (Am J Vet Res 1998;59:410–415)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To protect neonatal calves against fatal salmonellosis within the first 2 weeks after birth, using chicken egg yolk antibodies specific against Salmonella typhimurium or S dublin.

Animals

38 neonatal Holstein calves from Salmonella-free farms.

Procedure

After removal of the lipid components with hydroxypropylmethylcellulose phthalate, egg yolk antibodies were spray dried. At 4 days of age, calves were challenge exposed by oral inoculation with 1011 virulent S typhimurium (experiment 1) or S dublin (experiment 2). Starting from the challenge-exposure day, egg yolk antibody preparations were administered orally 3 times a day for 7 to 10 days.

Results

In passive immunization trials, the orally administered antibodies conferred dose-dependent protection against infection with each of the homologous strains of Salmonella. Within 7 to 10 days after challenge exposure, all control calves died, whereas low-titer antibody-treated calves had 60 to 100% mortality. Only fever and diarrhea, but no deaths (P < 0.01), were observed in calves given the highest titer of antibody.

Conclusions and Clinical Relevance

Compared with that in control calves, survival was significantly higher among calves given antibodies with titers of 500 (P < 0.05) and 1,000 (P < 0.01) homotypic for S typhimurium and with titer of 5,000 (P < 0.01) for S dublin. Egg yolk antibodies specific for whole cell S typhimurium or S dublin are protective against fatal salmonellosis when given in sufficiently high concentration, and may be clinically useful during a salmonellosis outbreak. (Am J Vet Res 1998;59:416–420)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine expression of the β2-integrin (CD18) family of adhesion molecules and L-selectin (CD62L) on neutrophils from periparturient cows and calves.

Animals

8 periparturient Holstein cows and 9 Holstein calves.

Procedure

Constitutive CD18 and CD62L expression on neutrophils was determined by flow cytometry, using specific monoclonal antibodies. Platelet-activating factor was used to activate neutrophils in vitro to measure down-regulation of CD62L and up-regulation of CD18 on activated neutrophils.

Results

Mean values for constitutive and platelet-activating factor-stimulated CD18 expression on neutrophils from cows and calves were highest at parturition, then decreased during the first 24 hours after parturition on calf neutrophils, whereas CD62L expression decreased markedly by 9 to 24 hours after parturition on cow and calf neutrophils. Constitutive amounts of CD18 and CD62L on cow neutrophils returned to prepartum values by day 3 after parturition. Amounts of CD18 expression on calves’ neutrophils recovered by 1 week of age, but did not reach original birth values, whereas CD62L expression exceeded birth values by day 3 after parturition. Cows had leukocytosis (neutrophilia), with a doubling of circulating neutrophils 9 hours after calving that was inversely correlated with CD62L expression on neutrophils.

Conclusions and Clinical Relevance

Low amounts of CD62L and CD18 on calf neutrophils and of CD62L on neutrophils from cows for several days after parturition may result in impaired inflammatory response. Low CD62L expression may contribute to increased susceptibility to disease. (Am J Vet Res 1998;59:37–43)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To characterize 2 bovine neutrophil monoclonal antibodies (MAB) as to effects on bovine neutrophil function and their binding antigens on the cell surface of bovine neutrophils.

Animals

16 healthy, lactating Holstein cattle, 1 calf with leukocyte adhesion deficiency, and 1 age-matched control calf, 2 healthy ewes, and 2 healthy human beings as neutrophil sources.

Procedure

Neutrophil chemotactic and respiratory burst activities and calcium influx, and binding properties of the 2 MAB were determined. Molecular mass of corresponding cell surface antigens also was determined, as was binding of human L-selectin MAB DREG56 to molecules recognized by MAB 11G10 and 2G8 on the surface of bovine neutrophils.

Results

MAB 11G10 and 2G8 inhibited chemotactic activity of bovine neutrophils, up-regulated amplitude of native chemiluminescence, and shortened the time to reach maximal chemiluminescence induced by serum-opsonized zymosan. Crosslinking both MAB with a second antibody induced rapid increase in intracellular free calcium concentration. Binding density of MAB 11G10 and 2G8 to bovine neutrophils treated with trypsin was increased (P < 0.05), compared with that of untreated neutrophils. Neutrophils treated with phosphatidylinositol-specific phospholipase C had decreased (P < 0.05) binding density of MAB 11G10 and 2G8. Binding of the various MAB to neutrophils from calves with bovine leukocyte adhesion deficiency was lower (P < 0.05) than binding to neutrophils from healthy calves. Expression of antigens recognized by the aforementioned MAB on the surface of bovine neutrophils was decreased (P < 0.05) within 10 minutes.

Conclusion

MAB 11G10 and 2G8 recognized L-selectin molecules on bovine neutrophil membrane. L-Selectin (CD62L) is involved in low-affinity adhesion reactions between leukocytes and L-selectin ligand on postcapillary venular endothelial cells. (Am J Vet Res 1997;58:1392–1401)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To characterize infection of bone marrow-derived macrophages (BMDM) with equine infectious anemia virus (EIAV) by determining virus production, effects on viability, and induction of cytokines.

Sample Population

BMDM obtained from bone marrow of 6 clinically normal adult horses.

Procedure

BMDM were infected with EIAV at a multiplicity of infection of 8. Cell viability, percentage of cells with detectable viral protein, reverse transcriptase activity, and concentrations of infective virus (focus-forming units/ml), interleukin 6, and tumor necrosis factor-α were measured in culture supernatant samples obtained at various days after infection.

Results

Cell viability was decreased on day 4 and was maximally decreased on day 8. The number of cells with detectable viral protein and supernatant reverse transcriptase activity increased significantly on day 4 and increased until day 6. Virus concentration (focus-forming units per milliliter) peaked on day 4 after infection and was constant thereafter. Infection with EIAV caused significant induction of interleukin 6 production by BMDM. The maximal difference was seen on day 4 after infection. Control and infected BMDM produced only negligible amounts of tumor necrosis factor-α.

Conclusions

BMDM are useful, as a cell population, to study the effects of infection with EIAV, including cell death and induction of interleukin 6 but not tumor necrosis factor-α production. (Am J Vet Res 1997;58:1402–1407)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To investigate whether platelet-activating factor (PAF) primes the porcine pulmonary response to lipopolysaccharide (LPS), and what effect PAF priming has on porcine neutrophil superoxide (SO) release.

Animals

8- to 10-week old pigs.

Procedures

After pigs were anesthetized with sodium pentobarbital and instrumented for standard cardiopulmonary hemodynamic measurements, they were randomly assigned to receive PAF (0.1 ng/kg of body weight/min, 0 to 2 hours) plus saline solution (2 to 6 hours), saline solution (0 to 2 hours) plus LPS (0.25 μg/kg/h, 2 to 6 hours), or PAF plus LPS. Cardiopulmonary variables were measured throughout the study. Neutrophils were isolated from saline- or PAF-treated pigs at 0 (baseline) and 2 hours, and the effect of in vivo PAF exposure on ex vivo phorbol myristate acetate (PMA)-induced SO release was measured. Additionally, neutrophils isolated from immune-naive pigs were primed in vitro for 10 minutes with 10 μM PAF, and PMA-induced SO release was measured.

Results

PAF infusion significantly enhanced the increase in mean pulmonary arterial pressure, pulmonary vascular resistance, and hypoxemia associated with LPS administration. The infusion increased ex vivo neutrophil SO release, and in vitro PAF exposure primed neutrophils for enhanced SO release that was inhibited by pretreatment of cells with indomethacin.

Conclusions

PAF primes the porcine pulmonary system for the response to LPS. It primes porcine neutrophils in vivo and in vitro for PMA-induced SO release, and in vitro priming is mediated by cyclooxygenase products of arachidonic acid metabolism.

Clinical Relevance

PAF may modulate the porcine inflammatory response by acting as a priming agent, making pigs more responsive to the negative effects of bacterial LPS. (Am J Vet Res 1997;58:1386–1391)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine whether horses with summer pasture-associated obstructive pulmonary disease (SPAOPD) have increased concentrations of antigen-specific IgG and IgE in tracheal lavage fluid, compared with values in clinically normal horses.

Animals

8 horses (6 females, 2 geldings; 6 Quarter Horses, 2 Appaloosas), 14 to 23 years old and with previous diagnosis of SPAOPD, served as the principal group; 8 horses (2 females, 6 geldings; 1 Quarter Horse, 7 Thoroughbreds), 6 to 9 years old, with no evidence of respiratory tract disease, served as the control group.

Procedure

Data were collected twice during a 1- year period: when all SPAOPD-affected horses were manifesting clinical signs of disease (July), and when all SPAOPD-affected horses appeared clinically normal (February). On each occasion, clinical evaluations were performed and blood and tracheal lavage fluid samples were collected. Transtracheal lavage supernatant was evaluated for mold antigen-specific IgG and IgE concentrations.

Results

Median IgE relative antibody unit (RAU) values were significantly higher in control, compared with principal, horses. The SPAOPD-affected horses had increased concentrations of specific IgG for only 1 antigen, during winter sample collection.

Conclusion

Antigen-specific IgG and IgE RAU values were not increased in SPAOPD-affected horses when these horses were manifesting clinical signs of disease. (Am J Vet Res 1997;58:1408–1411)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To identify the effect of Pasteurella haemolytica lipopolysaccharide (LPS) and leukotoxin (LKT) on spontaneous and calcium ionophore-induced histamine and inflammatory mediator release from isolated bovine lung parenchyma.

Sample Population

Lungs from 8 healthy cattle.

Procedure

Isolated bovine lung parenchyma was incubated in vitro for 2 hours with LKT or LPS, and spontaneous and induced release of inflammatory mediators was determined.

Results

LKT and LPS increased spontaneous release of histamine and leukotriene B4. In addition, incubation with LPS increased spontaneous release of prostaglandin E2. Moreover, a differential effect of the 2 toxins on calcium ionophore-induced inflammatory mediator release was observed. LKT specifically primed isolated lung parenchyma to release leukotriene B4 and thromboxane B2 in response to calcium ionophore, whereas LPS did not alter the profile of prostanoids released by bovine lung tissue exposed to calcium ionophore.

Conclusions

Pasteurella haemolytica toxins have a direct effect on bovine lung parenchyma, causing release of inflammatory mediators, which contribute to response to infection. Furthermore, bacterial toxins (LKT in this study) may sensitize tissues to the effects of other irritant stimuli, amplifying the inflammatory response. (Am J Vet Res 1997;58:1227–1231)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine relative sensitivities of the PK(15)- and WEHI 164(13)-based bioassays for detection of tumor necrosis factor α (TNF).

Sample Population

Recombinant human, murine, and porcine TNF, and serum from pigs given endotoxin IV.

Procedure

Two cell lines were used as targets for recombinant human, murine, and porcine TNF cytotoxicity bioassays. Pigs were given sublethal doses of endotoxin to obtain serum samples containing high activity of porcine TNF. Serum TNF activity was tested, using both cell lines. Viable cells were detected by addition of dimethylthiazol diphenyltetrazolium bromide after 18 to 20 hours’ incubation with samples containing TNF.

Results

The 2 cell lines tested had different sensitivities to human, murine, and porcine TNF. Compared with WEHI 164(13) cells, PK(15) cells were 50 times less sensitive to murine TNF and 15 times less sensitive to human TNF. However, PK(15) cells were 4 times more sensitive to recombinant porcine TNF and 15 times more sensitive to porcine serum containing TNF.

Conclusions

The PK(15) cell line was more sensitive to porcine TNF-mediated lysis than was the WEHI 164(13) cell line. The PK(15)-based TNF bioassay will be especially useful for study of infectious disease processes in swine, particularly where low activity of TNF exists. (Am J Vet Res 1997;58:1115–1119)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To examine safety and efficacy of a mutagen-attenuated Rift Valley fever virus (RVFV) vaccine (RVF MP-12) in cattle.

Animals

38 pregnant cows, 14 steers, and 10 lactating dairy cows.

Procedure

Pregnant cows in their third, fifth, or eighth month of gestation were vaccinated (1 ml of RVF MP-12 containing 5 log10 plaque-forming units [PFU] of virus) and were monitored daily through parturition for signs of disease, viremia, and immunologic response. Additionally, 10 vaccinated pregnant cows were challenge inoculated with virulent RVFV at postvaccination day (PVD) 30 and were monitored daily for untoward effects. Ten unvaccinated pregnant cows also were challenge inoculated with virulent RVFV and served as challenge controls. Vaccinated lactating dairy cows were monitored for viremia and virus shedding in the milk through PVD 14. Yearling steers were vaccinated to assess their immunologic response to various doses of vaccine and were challenge inoculated with virulent RVFV at PVD 28 to assess protection.

Results

10 of 38 (26.3%) cows vaccinated during pregnancy developed transient postvaccination viremia titer ≥ 2.5 log10 PFU/ml of serum. All vaccinated cows delivered live, healthy calves that were RVFV seronegative at birth, but which quickly acquired colostral antibodies. Vaccinated cows and their fetuses were protected when challenge exposed with virulent RVFV at PVD 30, whereas unvaccinated pregnant cows inoculated with RVFV became febrile and viremic, and aborted. Vaccine virus was unsuccessfully sought from milk of lactating dairy cows after vaccination, suggesting that shedding of vaccine virus through milk should not be a concern. Steers, inoculated with tenfold escalating vaccine doses, beginning with 1.0 log10 PFU, were protected against virulent RVFV challenge exposure.

Conclusions

RVF MP-12 may be safe and efficacious for use in pregnant or lactating bovids, and a minimal dose of vaccine may provide suitable protection against viremia. (Am J Vet Res 1997;58:1104–1109)

Free access
in American Journal of Veterinary Research