The candidate vaccine strain Brucella ovis ∆abcBA is protective against Brucella melitensis infection in mice

Brucellosis is a major zoonotic disease, and Brucella melitensis is the species most often associated with human infection. Vaccination is the most efficient tool for controlling animal brucellosis, with a consequent decrease of incidence of human infections. Commercially available live attenuated vaccines provide some degree of protection but retain residual pathogenicity to human and animals. In this study, Brucella ovis ∆abcBA (Bo∆abcBA) a live-attenuated candidate vaccine strain, was tested in two formulations (encapsulated with alginate and alginate plus vitelline protein B - VpB) to immunize mice against experimental challenge with B. melitensis strain 16M. One week after infection, livers and spleens of immunized mice had reduced numbers of the challenge strain B. melitensis 16M when compared to non-immunized mice, with a reduction of approximate 1-log10 of B. melitensis 16M in the spleens from immunized mice. Moreover, splenocytes stimulated with B. melitensis antigens in vitro secreted IFNγ when mice had been immunized with Bo∆abcBA encapsulated with alginate plus VpB, but not with alginate alone. Body and liver weights were similar among groups, although spleens from mice immunized with Bo∆abcBA encapsulated with alginate were larger than those immunized with Bo∆abcBA encapsulated with alginate plus VpB or non-immunized mice. This study demonstrated that two vaccine formulations containing Bo∆abcBA protected mice against experimental challenge with B. melitensis. This article is protected by copyright. All rights reserved.