Enhancing effect of chitosan nanoparticles on the immune efficacy of Bordetella bronchiseptica outer membrane vesicles

The outer membrane vesicle (OMV) of bacteria is a bilayer membrane vesicle with a diameter of about 10–300?nm that is secreted during the growth of Gram-negative bacteria. OMV is considered as a high-quality vaccine candidate antigen because of its natural immunogenicity and non-replicability. Although the excellent antigenicity of OMV has been widely confirmed, its instability and heterogeneity greatly affect its immune effect. Many studies have demonstrated that in combination with nanoparticles can enhance the stability of OMV. In this study, OMVs were used to coat chitosan nanoparticles (CNPs) and obtain a stable OMV vaccine. The characteristics, including morphology, hydrodynamic size, and zeta potential were evaluated. The immune protection of CNP-OMV and anti-infection efficacy were examined and compared in vivo and in vitro. The results showed that the CNP-OMV were homogenous with a size of 139?nm and a stable core–shell structure. And CNP-OMV could significantly increase the cell proliferation, phagocytosis and TNF-α, IL-6 and IL-10 secretion of RAW264.7 in vitro. In vivo, CNP-OMV could significantly increase the levels of anti-Bb and OMV IgG antibodies. Levels of blood lymphocyte, and Th1 (IFN-γ, IL-12), Th2 (IL-4, IL-5), and Th17 (IL-17, TNF-α) type cytokines in the serum were all significantly increased. At the same time, CNP-OMV could significantly reduce the bacterial invading the lungs of challenged rabbits. And CNP-OMV could largely protect the lungs from injury. The above results showed that CNP-OMV had a good immune efficacy and could resist the infection of Bordetella bronchiseptica . This study provided a scientific basis for the development of novel effective and safe vaccine against Bordetella bronchiseptica , and also provided a new idea for the development of new bacterial vaccine.

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