Elicitation of Th1/Th2 related responses in mice by chitosan nanoparticles loaded with Brucella abortus malate dehydrogenase, outer membrane proteins 10 and 19.

Brucella spp. is the causative agent of brucellosis, one of the worldwide diseases. The pathogen infects humans and animals mainly through the digestive or respiratory tract. Therefore, induction of mucosal immunity is required as the first line of defense. In this study, three Brucella abortus recombinant proteins, malate dehydrogenase (rMdh), outer membrane proteins (rOmp) 10 and 19 were loaded in mucoadhesive chitosan nanoparticles (CNs) and induction of mucosal and systemic immunity were investigated after intranasal immunization of BALB/c mice. These antigens were also coimmunized as cocktail (rCocktail) to evaluate multiple antigen specific vaccine candidates. At 6-weeks post-immunization (wpi), antigen specific total IgG was increased in all of the immunized groups, predominantly IgG1. In addition, spleenocyte from rMdh-, rOmp19-, and rCocktail-immunized groups significantly produced IFN-γ and IL-4 suggesting the induction of a mixed Th1-Th2 response. For mucosal immunity, anti-Mdh IgA from nasal washes and fecal excretions, and anti-Omps IgA from sera, nasal washes, genital secretions and fecal excretions were significantly increased in single antigen immunized groups. In the rCocktail-immunized group, anti-Mdh IgA were significantly increased while anti-Omps IgA was not. Collectively, this study indicates that comprise of B. abortus antigen-loaded CNs elicited the antigen-specific IgA with a Th2-polarized immune responses and combination of the highly immunogenic antigens elicited IgG specific to each type of antigen.