IMMUNOGENICITY OF OUTER MEMBRANE VESICLES FROM A BRUCELLA MELITENSIS HUMAN ISOLATE IN BALB/C MICE

Background and Aim:Brucellosis is a bacterial zoonosis with worldwide importance caused by members of the genus Brucella. Human infection occurs mainly by contact with infected animals and their products. Animal vaccination is the key for the disease control and prevention. However, live vaccines used for animal immunization have drawbacks which limit their application. Moreover, no approved vaccine is available for human use. Outer membrane vesicles (OMVs) are interesting tools for vaccine development against Gram-negative bacteria.Methods:In this study, OMVs from a B. melitensis human isolate were extracted by ultracentrifugation and characterized. BALB/c mice (n=12) were immunized with OMVs intramuscularly by 2 injections with a 2-week interval. Another 12 mice were used as controls. Two weeks after the last vaccination, 6 mice of each group were sacrificed to evaluate splenocyte proliferation and interferon gamma (IFNγ) production following in vitro stimulation. Concomitantly, other mice were challenge with the B. melitensis isolate. Two weeks later, all mice were killed and spleens were cultured for colony forming units (CFU) determination of challenge strain.Results:The results showed proliferative response and IFNγ production of splenocytes in vaccinated mice were significantly higher than those in control mice (2.18±0.57 stimulation index (SI) (mean±SD) vs 1.03±0.03 SI; 1519.35±10.7 pg/ml vs 210.01±17.58 pg/ml, respectively). Logarithms of challenge strain numbers in spleens of vaccinated mice were significantly less than those of controls (5.1±0.86 and 6.7±0.15, respectively).Conclusion:Our study revealed vaccination with OMVs of the B. melitensis isolate could induce specific immune responses and protection against its challenge in the mouse mode

Keywords:

Brucellosis , Vaccine , Outer Membrane Vesicles