Salmonella is an intracellular pathogen with a cellular infection mechanism similar to that of Brucella, making it a suitable choice for use in an anti-Brucella immune boost system. This study explores the efficacy of a Salmonella Typhimurium delivery-based combination vaccine for four heterologous Brucella antigens (Brucella lumazine synthase, proline racemase subunit A, outer-membrane protein 19, and Cu/Zn superoxide dismutase) targeting brucellosis in goats. We inoculated the attenuated Salmonella delivery-based vaccine combination subcutaneously at two different inoculation levels; 5 × 10⁹ colony-forming unit (CFU)/mL (Group B) and 5 × 10¹⁰ CFU/mL (Group C) and challenged the inoculations with virulent Brucella abortus at 6 weeks post-immunization. Serum immunoglobulin G titers against individual antigens in Salmonella immunized goats (Group C) were significantly higher than those of the non-immunized goats (Group A) at 3 and 6 weeks after vaccination. Upon antigenic stimulation, interferon-γ from peripheral blood mononuclear cells was significantly elevated in Groups B and C compared to that in Group A. The immunized goats had a significantly higher level of protection as demonstrated by the low bacterial loads in most tissues from the goats challenged with B. abortus. Relative real-time polymerase chain reaction results revealed that the expression of Brucella antigens was lower in spleen, kidney, and lung of immunized goats than of non-immunized animals. Also, treatment with our combination vaccine ameliorated histopathological lesions induced by the Brucella infection. Overall, the Salmonella Typhimurium delivery-based combination vaccine was effective in delivering immunogenic Brucella proteins, making it potentially useful in protecting livestock from brucellosis.
Animals ; Bacterial Load ; Brucella abortus ; Brucella Vaccine ; Brucella ; Brucellosis ; Goats ; Immunoglobulin G ; Kidney ; Livestock ; Lung ; Proline ; Real-Time Polymerase Chain Reaction ; Salmonella typhimurium ; Salmonella ; Spleen ; Stem Cells ; Superoxides ; Vaccination

Animals ; Antibodies, Bacterial ; blood ; Bacterial Proteins ; genetics ; immunology ; Brucella Vaccine ; immunology ; Brucella abortus ; immunology ; Female ; Immunization ; Interferon-gamma ; biosynthesis ; Lymphocyte Activation ; Mice ; Mice, Inbred BALB C ; Periplasmic Binding Proteins ; genetics ; immunology ; Ribosomal Proteins ; genetics ; immunology ; Vaccines, DNA ; immunology

The outer membrane proteins (OMPs) of Brucella (B.) abortus have been extensively studied, but their immunogenicity and protective ability against B. abortus infection are still unclear. In the present study, B. abortus Omp28, a group 3 antigen, was amplified by PCR and cloned into a maltose fusion protein expression system. Recombinant Omp28 (rOmp28) was expressed in Escherichia coli and was then purified. Immunogenicity of rOmp28 was confirmed by Western blot analysis with Brucella-positive mouse serum. Furthermore, humoral- or cell-mediated immune responses measured by the production of IgG1 or IgG2a in rOmp28-immunized mice and the ability of rOmp28 immunization to protect against B. abortus infection were evaluated in a mouse model. In the immunogenicity analysis, the mean titers of IgG1 and IgG2a produced by rOmp28-immunized mice were 20-fold higher than those of PBS-treated mice throughout the entire experimental period. Furthermore, spleen proliferation and bacterial burden in the spleen of rOmp28-immunized mice were approximately 1.5-fold lower than those of PBS-treated mice when challenged with virulent B. abortus. These findings suggest that rOmp28 from B. abortus is a good candidate for manufacturing an effective subunit vaccine against B. abortus infection in animals.
Animals ; Antibodies, Bacterial/blood ; Blotting, Western/veterinary ; Brucella Vaccine/*immunology ; Brucella abortus/*immunology ; Brucellosis, Bovine/*immunology/microbiology/*prevention & control ; Cattle ; Cloning, Molecular ; Electrophoresis, Polyacrylamide Gel/veterinary ; Enzyme-Linked Immunosorbent Assay/veterinary ; Female ; Immunization/veterinary ; Immunoglobulin G/blood ; Immunoglobulin Isotypes/blood ; Membrane Proteins/genetics/*immunology ; Mice ; Mice, Inbred BALB C ; Models, Animal ; Recombinant Proteins/genetics/immunology ; Vaccines, Subunit/immunology