Immunization of mice with gamma-irradiated Brucella neotomae and its recombinant strains induces protection against virulent B. abortus, B. melitensis, and B. suis challenge

Human brucellosis, a zoonotic disease of major public health concern in several developing countries, is primarily caused by Brucella abortus, Brucella melitensis, and Brucella suis. No brucellosis vaccine is available for human use. The aim of this study was to determine if Brucella neotomae, a bacterium not known to cause disease in any host, can be used for developing brucellosis vaccines. B. neotomae and its recombinant strains overexpressing superoxide dismutase and a 26 kDa periplasmic protein were rendered non-replicative through exposure to gamma-radiation and used as vaccines in a murine brucellosis model. All three vaccines induced antigen-specific antibody and T cell responses. The vaccinated mice showed significant resistance against challenge with virulent B. abortus 2308, B. melitensis 16 M, and B. suis 1330. These results demonstrate that the avirulent B. neotomae is a promising platform for developing a safe and effective vaccine for human brucellosis.