Newcastle disease virus-like particles containing the Brucella BCSP31 protein induce dendritic cell activation and protect mice against virulent Brucella challenge

Brucellosis is a widespread zoonosis that poses a substantial threat to human and animal public health due to the absence of a sufficiently safe and efficient vaccine. Virus-like particles (VLPs) have been developed as novel vaccine candidates and suitable carrier platforms for the delivery of exogenous proteins. Herein, we constructed chimeric virus-like particles (cVLPs) assembled by a Newcastle disease virus (NDV) M protein and glycosyl-phosphatidylinositol-anchored Brucella BCSP31 protein (GPI-BC5P31). cVLPs-GPI-BC51331 were highly efficient in murine dendritic cell (DC) activation, both in vitro and in vivo. Moreover, they elicited strong specific humoural immune responses detected through EL1SA assay with inactivated Brucella and recombinant BCSP31 protein and by elevated cellular immune responses indicated by intracellular IFN-gamma and IL-4 levels in CD3+CD4+T and CD3+CD8+T cells. Importantly, cVLPs-GPI-BCSP31 conferred protection against virulent Brucella melitensis strain 16 M challenge, comparable to the efficacy of Brucella vaccine strain M5. In summary, this study provides a new strategy for the development of a safe and effective vaccine candidate against virulent Brucella and further extends the application of NDV VLP-based vaccine platforms.