• Vaccine Name: Recombinant Brucella abortus RB51 vaccine expressing listeriolysin O, BAX, and SMAC
• Target Pathogen: Brucella spp.
• Target Disease: Brucellosis
• Vaccine Ontology ID: VO_0009508
• Type: Live attenuated vaccine + Recombinant vector vaccine
• Status: Research
• Host Species for Licensed Use: Cattle
• Host Species as Laboratory Animal Model: Mus musculus; J774A.1 murine macrophage-like cell line; BALB/c mice
• Antigen: listeriolysin O (LLO); mutant LLO (mLLO); BAX; SMAC
• Preparation: RB51 was transformed with two broad-host-range plasmids: pbbr1ori-LLO containing LLO, and pBlu-mLLO-BAX-SMAC containing mutant LLO and BAX-SMAC fusion gene, generating recombinant RB51 strains. (Sarmadi et al, 2022)
• Description: The RB51 strain is a live attenuated vaccine with low side effects but insufficient protective efficacy. To enhance efficacy and safety, RB51 was genetically modified to express Listeria monocytogenes listeriolysin O (LLO), and apoptotic proteins BAX and SMAC. Efficacy: Recombinant RB51 strains expressing mLLO and BAX-SMAC showed higher cytotoxicity, reduced macrophage survival, and increased apoptosis and necrosis compared to parental RB51. Vaccination with RB51-mLLO-BAX-SMAC enhanced Th1 immune response in mice, indicating improved potency. Immune response: Enhanced T cell-mediated immunity, primarily through bacterial endosome escape and antigen cross-priming, leading to increased IFN-γ production and a stronger Th1 response, potentially improving safety and efficacy of the vaccine candidate. (Sarmadi et al, 2022)

Mouse Response

• Host Strain: BALB/c
• Host cell type: J774A.1
• Immune Response: Enhanced T cell-mediated immunity, primarily through bacterial endosome escape and antigen cross-priming, leading to increased IFN-γ production and a stronger Th1 response, potentially improving safety and efficacy of the vaccine candidate. (Sarmadi et al, 2022)
• Efficacy: Recombinant RB51 strains expressing mLLO and BAX-SMAC showed higher cytotoxicity, reduced macrophage survival, and increased apoptosis and necrosis compared to parental RB51. Vaccination with RB51-mLLO-BAX-SMAC enhanced Th1 immune response in mice, indicating improved potency. (Sarmadi et al, 2022)
• Description: In vitro infection of J774A.1 macrophage-like cells with recombinant RB51 strains and parental RB51 to assess cytotoxicity, bacterial survival, apoptosis, and necrosis. In vivo vaccination of BALB/c mice with RB51-mLLO-BAX-SMAC recombinant strain to evaluate modulation of IFN-γ production and Th1 immune response. (Sarmadi et al, 2022)