The outer membrane vesicles (OMVs) from smoothB. melitensis16 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 fromB. melitensis16 M; some of them are well-knownBrucellaimmunogens such as SOD, GroES, Omp31, Omp25, Omp19, bp26, and Omp16. OMVs from a rough VTRM1 induced significantly higher expression of IL-12, TNFα, and IFNγgenes 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 strainB. melitensis16 M just as well as the group immunized with live strainB. melitensisRev1 (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.
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