Conclusion
Encapsulated BoΔabcBA protected mice against experimental B. canis infection, and it is safe for dogs. Therefore, B. ovis ΔabcBA has potential as a vaccine candidate for canine brucellosis prevention.
Methods
Intracellular growth of the vaccine strain BoΔabcBA was assessed in canine and ovine macrophages. Protection induced by BoΔabcBA against virulent Brucella canis was evaluated in the mouse model. Safety of the vaccine strain BoΔabcBA was assessed in experimentally inoculated dogs.
Results
Wild type B. ovis and B. canis had similar internalization and intracellular multiplication profiles in both canine and ovine macrophages. The BoΔabcBA strain had an attenuated phenotype in both canine and ovine macrophages. Immunization of BALB/c mice with alginate-encapsulated BoΔabcBA (108 CFU) induced lymphocyte proliferation, production of IL-10 and IFN-γ, and protected against experimental challenge with B. canis. Dogs immunized with alginate-encapsulated BoΔabcBA (109 CFU) seroconverted, and had no hematologic, biochemical or clinical changes. Furthermore, BoΔabcBA was not detected by isolation or PCR performed using blood, semen, urine samples or vaginal swabs at any time point over the course of this study. BoΔabcBA was isolated from lymph nodes near to the site of inoculation in two dogs at 22 weeks post immunization.