Induction of protective immunity against brucellosis in mice by vaccination with a combination of naloxone, alum, and heat-killed Brucella melitensis 16 M.

BACKGROUND/PURPOSE: A T-helper cell type 1-specific response leads to the elimination of intracellular infection with Brucella. Studies have shown that naloxone (NLX) can promote a cellular immune response in this respect. The current study was carried out to evaluate the induction of protective immunity in mice against brucellosis by vaccination with a combination of NLX, alum, and heat-killed Brucella melitensis 16 M (HKB). METHODS: Mice were categorized into five groups and received intraperitoneal vaccination on Days 0 and 7. Then serum levels of interferon (IFN)-γ and interleukin (IL)-4, the bacterial load, and the survival rate were measured 2 weeks after the last vaccination. RESULTS: The serum levels of IFN-γ, IL-4, and immunoglobulin G in the NLX + alum + HKB group were shown to be significantly increased (p < 0.05). Furthermore, the lowest bacterial load was observed in this group. The survival rate in groups vaccinated with combinations containing adjuvants was 100%. CONCLUSION: The combination of NLX and alum enhanced the immunogenicity of HKB, which can be used in the vaccination of animals and humans at risk of the disease.