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Abstract

Objective—To determine the immunogenicity and efficacy of Brucella abortus strain RB51 (SRB51) as a vaccine in domestic pigs.

Animals—Sixty-eight 6-week-old crossbred domestic pigs and twenty-four 4-month-old gilts.

Procedures—In experiment 1, pigs were vaccinated IM (n = 51) with 2 × 1010 CFUs of SRB51 or sham inoculated (17). Periodic blood samples were obtained to perform blood cultures, serologic evaluations, and cell-mediated immunity assays. Necropsies were performed at selected times between weeks 1 and 23 after vaccination to determine vaccine clearance. In experiment 2, gilts were similarly vaccinated (n = 18) or sham inoculated (8) and similar samples were obtained after vaccination. Gilts were bred and challenged conjunctivally with 5.0 × 107 CFUs of virulent Brucella suis strain 3B. Necropsies were performed on gilts and on fetuses or neonates after abortion or parturition, respectively. Bacterial cultures and serologic evaluations were performed on samples obtained at necropsy to determine vaccine efficacy.

Results—Humoral and cell-mediated immune responses did not differ between vaccinates and controls. After vaccination, SRB51 was not isolated from blood cultures of either group and was isolated from lymphoid tissues of 3 pigs at 2 weeks (n = 2) and 4 weeks (1) after vaccination. No differences were found in isolation of B suis or in seroconversion between vaccinated and control gilts and between their neonates or aborted fetuses.

Conclusions and Clinical Relevance—Parenteral vaccination with SRB51 does not induce humoral or cell-mediated immune responses. Vaccination with SRB51 did not protect gilts or their neonates and fetuses from virulent challenge with B suis.

Full access
in American Journal of Veterinary Research

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 determine the safety and immunogenicity of Brucella abortus strain RB51 as a vaccine in pregnant cattle.

Animals

12 Polled Hereford heifers obtained from a brucellosis-free herd and bred on site at 16 months of age to a brucellosis-free bull.

Procedure

Pregnant heifers were vaccinated at 6 months’ gestation with 109 colony-forming units of B abortus strain RB51 (n = 5), 3 × 108 colony-forming units of B abortus strain 19 (n = 5), or sterile pyrogen-free saline solution (n = 2). Samples were periodically collected for serologic testing and lymphocyte blastogenesis assays. At full gestation, heifers were euthanatized and specimens were collected for bacteriologic culture, histologic analysis, and lymphocyte blastogenesis assay, using various antigenic stimuli.

Results

None of the strain RB51- or strain 19-vaccinates aborted or had gross or microscopic lesions at necropsy that were consistent with brucellosis. Maternal blood mononuclear cells from strain RB51- and strain 19-vaccinates had proliferative responses to γ-irradiated strain RB51 and strain 19 that were greater than responses by cells from nonvaccinated controls. In contrast, maternal superficial cervical lymph node cells from strain 19-vaccinates had proliferative responses to γ-irradiated strain RB51 or strain 19 bacteria greater than those of cells from RB51-vaccinates and nonvaccinated controls. None of the heifers vaccinated with strain RB51 developed antibodies detected by use of the standard tube agglutination test, but all developed antibodies to strain RB51 that reacted in a dot ELISA, using irradiated strain RB51 as antigen.

Conclusions

Pregnant cattle can be safely vaccinated with strain RB51 without subsequent abortion or placentitis. Furthermore, strain RB51 is immunogenic in pregnant cattle, resulting in humoral and cell-mediated immune responses, but does not interfere with serologic diagnosis of field infections. (Am J Vet Res 1997;58:472–477)

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

Abstract

Objective

To evaluate clearance, antibody responses, potential shedding, and histologic lesions in reproductive tissues of adult bison bulls after vaccination with Brucella abortus strain RB51.

Animals

61 two- and 3-year-old bison bulls.

Procedure

12 bison bulls were vaccinated SC with B abortus strain RB51, 3 were inoculated SC with 0.15M NaCI, and antibody responses were evaluated. Various specimens were obtained to evaluate bacterial shedding. Four vaccinates and 1 control were necropsied 10, 20, and 30 weeks after vaccination. In a separate experiment, bison bulls were vaccinated SC with 0.15M NaCI, or by hand or ballistically with strain RB51. Antibody responses were monitored 6 weeks after vaccination and during necropsy 13 weeks after vaccination. Tissue specimens obtained during necropsy from both studies were evaluated bacteriologically and histologically.

Results

Strain RB51 was recovered at various times from semen of 3 of 12 vaccinated bison bulls in experiment 1. During necropsy, strain RB51 was recovered 10 and 20, but not 30, weeks after vaccination. In experiment 2, strain RB51 was recovered from lymphoid tissues of hand- and ballistic-vaccinated bison bulls during necropsy. In both experiments, microscopic lesions in testes, epididymis, and seminal vesicles were minimal and did not differ between strain RB51-vaccinated and saline-inoculated bison bulls.

Conclusions and Clinical Relevance

Strain RB51 does not induce relevant inflammatory lesions in reproductive tissues of adult bison bulls. Shedding of strain RB51 in semen may be transient in some bison bulls; however, the importance of this observation is unknown. (Am J Vet Res 1999;60:905–908)

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective

To determine the ability of Brucella abortus strain RB51 to induce placentitis and abortion in bison after SC vaccination.

Animals

10 pregnant bison cows, 3 to 10 years old and at 3 to 8 months' gestation.

Procedure

Pregnant bison cows on a Montana ranch were vaccinated SC with 109 colony-forming units of B abortus strain RB51. Two cows, identified prior to the study, were euthanatized and examined 5 weeks after vaccination to obtain optimal histologic samples of placenta. Other cows were euthanatized and examined after abortion. After euthanasia, tissue specimens were collected for histologic and immunohistochemical evaluation. Tissue and fluid specimens for bacteriologic culture were also collected during necropsy.

Results

Of 8 cows, 2 aborted at 68 and 107 days after vaccination. Aborting cows had endometritis. Strain RB51 was isolated from reproductive tissues and supramammary lymph nodes. Fetal lesions were not seen; however, fetal bronchial lymph nodes and amniotic fluid contained strain RB51. Cows examined 5 weeks after vaccination had placentitis and endometritis, with numerous bacteria within trophoblastic epithelial cells that were immunoreactive for strain RB51 antigen. Strain RB51 was isolated from placentomes and numerous lymph nodes. Fetal lesions were not seen 5 weeks after vaccination; however, strain RB51 was isolated from numerous lymph nodes and lung, allantoic fluid, and rectal swab specimens.

Conclusions

The vaccine candidate B abortus RB51 has tropism for the bison placenta, and can cause placentitis, which induces abortion in pregnant bison. The vaccine dose used was similar to that being tested in cattle, but may not be appropriate for pregnant bison. (Am J Vet Res 1996;57:1604–1607)

Free access
in American Journal of Veterinary Research