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Protectivecapacity of Outer Membrane Vesicles derived from Bordetella bronchiseptica.Authors:Bottero D, Gaillard ME and Hozbor DThough vaccines for Bordetella bronchiseptica (Bb)zoonotic pathogen have been in common use since theirdevelopment in the late 1970s many questions related to the efficacy and thelongevity of vaccine-induced immunity remain unanswered. New vaccines, bettercharacterized, seems to be neededObjective: To design and characterize a new vaccine against Bb based on outermembrane vesicles derived from this pathogen (OMVsBb). Material and Methods: Basedon our experience on OMVs isolation from B.pertussis and B. parapertussis,here we obtained OMVsBb from Bb strain 9.73. TEM microscopy and immunoblots were usedto examine the quality of our OMVsBb preparations. Totest the protective capacity of OMVsBb-based vaccine, the murine respiratory model ofinfection was used.Results: OMVsBb with a mean size of80nm were obtained. When these characterized OMVsBb were used in the murinemodel as vaccine against the infection caused by Bb isolates obtained eitherfrom rabbit or human, significant differences between immunized animals and thePBS treated group were observed (p < 0.001). Humoral response induced byOMVsBb vaccine appeared to be involved in the protective capacity as it wasdemonstrated by sera transfer assay. Adequateelimination rates were observed in mice immunized with OMVsBb-sera but not withnaïve sera (p < 0.001). The contribution of virulence factors in OMVsBb-mediatedprotection was also investigated. Interestingly, we observed that theprotective ability of OMVsBb obtained from a Bb strain, which does notexpress any of the virulence factors but expresses the avirulent phenotype; wascomparable to that of OMVs obtained from virulent Bb phase. Conclusion: Here we demonstrated that OMVsBb are protective in themurine model of infection. Protection conferred by OMVsBb seems to be at leastmediated by the humoral immune response. Moreover, the presence of virulencefactors on OMVsBb is not essential for the protective capacity conferred byOMVsBb.