Search Results

You are looking at 1 - 5 of 5 items for :

  • Author or Editor: Mark G. Stevens x
  • Refine by Access: All Content x
Clear All Modify Search

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

SUMMARY

The role of interleukin-1 (il-1), interleukin-6 (il- 6), and tumor necrosis factor α during endotoxin-induced mastitis in cows was characterized. Six cows had 10 μg of Escherichia coli lipopolysaccharide infused into 1 mammary gland. Three other cows served as nontreated controls. Within 1.5 to 2.5 hours after infusion, endotoxin caused obvious edema of the mammary gland and increased serum albumin concentration in milk of infused glands 6 times. Milk somatic cell count began to increase 3 to 5 hours after infusion in all treated glands. At 7 hours after infusion, somatic cell counts were increased >10 times, compared with counts in milk from control cows. Pyrexia of >1 C developed in only 1 cow, but all treated cows had serum cortisol concentrations >50 ng/ml in response to endotoxin treatment. High concentrations of il-1 (10 to 600 U/ml) and il-6 (2 to 22 U/ml) were detected in milk of infused glands beginning 2.5 to 4 hours after infusion. Endotoxin did not induce detectable amounts of tumor necrosis factor activity in milk or serum. Swelling and mammary gland permeability changes preceded any detectable increase in il-1 and il-6 activity, indicating that these clinical signs of inflammation were not mediated by these cytokines. Systemic responses and the leukocytic influx into endotoxin-infused glands developed after or concurrently with initial increases in il-1 and il-6 activities in milk. These results suggested that il-1 and il-6 may have a role in mammary gland defenses and in the pathophysiologic changes during endotoxin-induced mastitis.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To establish that female calves vaccinated with Brucella abortus strain RB51 at 3, 5, and 7 months of age are protected against infection and abortion when challenged exposed during their first pregnancy.

Animals

Polled Hereford heifer calves obtained from a brucellosis-free herd.

Procedure

Calves were inoculated SC at 3, 5, or 7 months of age with strain RB51 (n = 26), strain 19 (n = 16), or sterile saline solution (n = 15). Calves were bred at 16 to 17 months of age and challenged exposed during the first pregnancy with virulent B abortus strain 2308.

Results

After vaccination, none of the heifers given strain RB51 developed serum antibodies that reacted in the standard tube agglutination test, but reacted in a dotblot assay, using RB51 antigen. B abortus was cultured from biopsy specimens of superficial cervical lymph nodes in the RB51 and S19 vaccinates at 10 weeks, but not at 12 weeks after vaccination. All 4 heifers that had been vaccinated with RB51 at 3 months of age were protected against infection and abortion when challenged exposed. Vaccination at 5 and 7 months of age gave equivalent protection. Heifers given strain 19 were 95% protected and controls (given saline solution) had a high incidence of infection and abortion.

Conclusions

Strain RB51 is protective at doses comparable to those of strain 19 in calves 3 to 10 months of age.

Clinical Relevance

Immunogenicity and failure to induce antibodies that interfere with the serologic diagnosis of field infections of B abortus make strain RB51 an effective vaccine. (Am J Vet Res 1996;57:1153—1156)

Free access
in American Journal of Veterinary Research

SUMMARY

A study was conducted to determine the effect of monophosphoryl lipid A (mpl) and trehalose dimycolate (tdm) as adjuvants on the protective responses in balb/c mice vaccinated with Brucella abortus salt-extractable protein (bcsp) or proteinase-K-treated B abortus lipopolysaccharide (pklps). Mice were vaccinated with different doses of bcsp or pklps given alone or in combination with mpl or tdm. Mice were challenge-exposed 4 weeks later with virulent B abortus strain 2308. Two weeks after challenge exposure, the number of B abortus colony-forming units (cfu) per spleen, spleen weights, and spleen cell interleukin 1 production were measured. Serum IgG and IgM concentrations specific for vaccinal immunogens were measured before and after challenge exposure with B abortus.

Spleen weights and mean B abortus cfu per vaccine group were significantly lower in bcsp- and pklps-vaccinated mice, compared with those of nonvaccinated control mice. Monophosphoryl lipid A enhanced the suppression of splenic infection when given with the bcsp vaccine, but not when given with the pklps vaccine. Trehalose dimycolate had no effect on mean cfu when given with bcsp, but incorporation of tdm resulted in a significant increase in mean cfu when given with pklps. Spleen weights in bcsp- or pklps-vaccinated mice were not different when these vaccines were combined with mpl or tdm. Because of the wide variation in the results, we could not conclude that vaccination with bcsp or pklps alone, or in combination with mpl altered spleen cell interleukin-1 production in B abortus-infected mice. Increased host protection as defined by decreased cfu could not be related consistently to increased bcsp- or pklps-specific serum IgG or IgM antibodies introduced by any of the vaccines. These results do not eliminate a role for antibodies in the protection observed.

Free access
in American Journal of Veterinary Research

SUMMARY

Leukocytosis (34,600 wbc/μl of blood) was detected in an apparently healthy 7-day-old Holstein heifer. Analysis of blood samples obtained over the next 41 days revealed chronic progressive neutrophilia, which peaked at > 85% neutrophils and exceeded 100,000 wbc/μl. In vitro assessment of isolated blood neutrophils obtained from the heifer at 38 and 45 days of age revealed selected functional abnormalities. Endocytosis of immunoglobulin-opsonized Staphylococcus aureus and killing of this test organism by the calf’s neutrophils were significantly diminished, as were phagocytosis-associated superoxide generation, chemiluminescence activity, and myeloperoxidase-catalyzed iodination. Diminished H2O2 elaboration by the calf’s neutrophils was evident during ingestion of opsonized zymosan or on exposure to phorbol myristate acetate. Extracellular release (secretion) of elastase during ingestion of zymosan was also diminished, although total cell content of elastase was normal, compared with that of neutrophils from age-matched calves, and granular or other morphologic abnormalities of the calf’s neutrophils were not evident by ultrastructural examination. Abnormalities of random migration were inconsistently detected, and normal or high degree of antibody-dependent cytotoxicity or natural killing by the calf’s neutrophils was observed. Similar in vitro assessment of neutrophils obtained from the calf’s dam revealed no functional abnormalities. The calf died at 48 days of age, with persistent fever and chronic diarrhea, despite administration of antibiotics. Histologic examination at necropsy revealed large numbers of intravascular neutrophils in most tissues, including massive neutrophil sequestration in spleen. However, a striking lack of extravascular neutrophils was evident in inflamed submucosa adjacent to intestinal ulcers heavily contaminated with enteric microorganisms. Bone marrow examination revealed diffuse myeloid hyperplasia, but no other abnormalities.

The clinical and pathologic features in this calf were similar to those in previously reported human patients or Irish Setters with genetic deficiency of the CD11/CD18 leukocyte glycoprotein complex, thus prompting further postmortem evaluations. Results of immunoblot analyses of the neutrophil lysates of the heifer calf (isolated and stored prior to death) documented severe deficiency of Mac-1 (CD11b/CD18). Results of immunofluorescent analyses indicated substantially diminished (intermediate) amounts ofthe Mac-1 β subunit (CD18) on blood neutrophils of the calf's dam and sire and on neutrophils of 8 of 15 paternal half-siblings; findings were consistent with an autosomal recessive trait in the proband's kindred. Findings also indicate that genetic abnormalities of CD11/CD18 proteins may underlie the molecular pathogenesis of disease in this calf as well as other previously described examples of the granulocytopathy syndrome in Holstein cattle.

Free access
in American Journal of Veterinary Research