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  • Author or Editor: Betsy J. Bricker x
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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

SUMMARY

A study was conducted to determine whether subcomponent proteins (previously identified as BCSP20, BCSP31, and BCSP45, and the corresponding recombinant proteins rBCSP20, rBCSP31, and rBCSP45) that were recovered from the cell surface of Brucella abortus strain 19 were immunogenic and protective for mice when compared with Brucella cell surface protein (bcsp) and with a proteinase K-treated lipopolysaccharide (pklps) extracted from B abortus strain 2308. Protection was evaluated after challenge exposure with a virulent culture of B abortus strain 2308, using CD-I or BALB/c mice or both inoculated with vaccines of various combinations and concentrations, with and without pklps or bcsp. Protection was assessed by enumeration of splenic colony-forming units, reduced mean splenic weight relative to controls, and the relative serologic responses (immune response) in an elisa.

The general results indicate that bcsp, pklps, bcsp20, and bcsp31 are immunogenic or protective or both. Protectiveness was not observed for each of the recombinant proteins; however, results from the combined recombinant protein vaccine study suggest the immunogenicity of the recombinant proteins. The apparent immune-inducing properties of bcsp20 and bcsp31 are thought to be attributable to the presence of an immunogenic and protective bcsp fraction (possibly lipopolysaccharide) still associated. Serologic results support our conclusion that each of the recombinant protein vaccines did not induce a protective response comparable to that of bcsp or pklps, even when the subcomponents were combined.

Although the results suggest that the subcomponents of bcsp apparently induced partial protection, they are thought to be only a part of the antigens contained in bcsp that influence the serologic response. Our findings may serve as an experimental model to determine the mechanisms involved in the protective responses induced by Brucella antigens.

Free access
in American Journal of Veterinary Research