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Published on: August 5, 2016
Characterization of outer membrane vesicles from Brucella melitensis and protection induced in mice
Eric Daniel Avila-Calderón1, Ahidé Lopez-Merino, Neeta Jain
1Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Colonia Santo Tomás, 11340, Mexico, DF, Mexico.
Abstract:
The outer membrane vesicles (OMVs) from smooth B. melitensis 16 M and a derived rough mutant, VTRM1 strain, were purified and characterized with respect to protein content and induction of immune responses in mice. Proteomic analysis showed 29 proteins present in OMVs from B. melitensis 16 M; some of them are well-known Brucella immunogens such as SOD, GroES, Omp31, Omp25, Omp19, bp26, and Omp16. OMVs from a rough VTRM1 induced significantly higher expression of IL-12, TNFα, and IFNγ genes in bone marrow dendritic cells than OMVs from smooth strain 16 M. Relative to saline control group, mice immunized intramuscularly with rough and smooth OMVs were protected from challenge with virulent strain B. melitensis 16 M just as well as the group immunized with live strain B. melitensis Rev1 (P < 0.005). Additionally, the levels of serum IgG2a increased in mice vaccinated with OMVs from rough strain VTRM1 consistent with the induction of cell-mediated immunity.
Insights
Outer membrane vesicles (OMVs) from rough Brucella melitensis induced stronger immune responses and protected mice against infection. These bacterial OMVs show potential as effective vaccine candidates against Brucellosis.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Brucella melitensis causes brucellosis, a significant zoonotic disease.
- Outer membrane vesicles (OMVs) are promising vaccine platforms due to their inherent immunogenicity.
- Investigating differences between smooth and rough Brucella OMVs can reveal novel vaccine strategies.
Purpose of the Study:
- To characterize and compare the immunogenicity of OMVs from smooth (B. melitensis 16 M) and rough (VTRM1) Brucella strains.
- To evaluate the protective efficacy of these OMVs as vaccine candidates against virulent B. melitensis challenge.
- To assess the type of immune response induced by smooth and rough OMVs.
Main Methods:
- Purification and proteomic analysis of OMVs from smooth and rough B. melitensis strains.
- In vitro assessment of immune gene expression (IL-12, TNFα, IFNγ) in bone marrow dendritic cells.
- In vivo immunization of mice with OMVs followed by challenge with virulent B. melitensis.
- Measurement of serum IgG2a levels to infer cell-mediated immunity.
Main Results:
- Proteomic analysis identified known Brucella immunogens in smooth strain OMVs.
- Rough strain VTRM1 OMVs induced significantly higher expression of key immune genes (IL-12, TNFα, IFNγ) in dendritic cells.
- Mice vaccinated with both smooth and rough OMVs demonstrated protection comparable to live B. melitensis Rev1 vaccination.
- Vaccination with rough strain OMVs correlated with increased serum IgG2a, indicating cell-mediated immunity.
Conclusions:
- Bacterial OMVs from both smooth and rough Brucella strains confer significant protection against virulent challenge.
- Rough strain OMVs elicit a stronger innate immune response and promote cell-mediated immunity, suggesting enhanced vaccine potential.
- OMVs represent a viable and effective strategy for developing subunit vaccines against Brucellosis.
