Evaluation of the Efficacy of Outer Membrane Protein 31 Vaccine Formulations for Protection against Brucella canis in BALB/c Mice

Abstract

ABSTRACTCanine brucellosis is an infectious disease caused by the Gram-negative bacteriumBrucella canis. Unlike conventional control programs for other species of the genusBrucella, currently there is no vaccine available against canine brucellosis, and preventive measures are simply diagnosis and isolation of infected dogs. New approaches are therefore needed to develop an effective and safe immunization strategy against this zoonotic pathogen. In this study, BALB/c mice were subcutaneously immunized with the following: (i) the recombinantBrucellaOmp31 antigen formulated in different adjuvants (incomplete Freund adjuvant, aluminum hydroxide, Quil A, and Montanide IMS 3012 VGPR), (ii) plasmid pCIOmp31, or (iii) pCIOmp31 plasmid followed by boosting with recombinant Omp31 (rOmp31). The immune response and the protective efficacy againstB. canisinfection were characterized. The different strategies induced a strong immunoglobulin G (IgG) response. Furthermore, spleen cells from rOmp31-immunized mice produced gamma interferon and interleukin-4 (IL-4) afterin vitrostimulation with rOmp31, indicating the induction of a mixed Th1-Th2 response. Recombinant Omp31 administered with different adjuvants as well as the prime-boost strategy conferred protection againstB. canis. In conclusion, our results suggest that Omp31 could be a useful candidate for the development of a subcellular vaccine againstB. canisinfection.