A comparison between adjuvant and delivering functions of calcium phosphate, aluminum hydroxide and chitosan nanoparticles, using a model protein of Brucella melitensis Omp31.

Vaccination is the most efficient and economic approach used to hinder infection and intense consequences caused by viruses, bacteria, or other pathogenic organisms. Since the intrinsic immunogenicity of recombinant antigens is usually low, safe and potent vaccine adjuvants are needed to ensure the success of those recombinant vaccines. Nanoparticles (NPs) have attracted much interest as adjuvants and delivery systems. Previous studies have shown that calcium phosphate (CP), aluminum hydroxide (AH) and chitosan (CS) NPs are promising delivery systems for immunization. In addition, it has been determined that Omp31 is a good candidate for inducing protection against Brucella (B) melitensis and B. ovis. Our aim in the present study was to compare the functions of CP, AH and CS NPs for stimulation of the immune response and protection against B. melitensis by using omp31 as a model protein. Based on the cytokine profile and subclasses of the antibody, vaccination with Omp31 load CP (CP/Omp31) and Omp31 load AH (AH/Omp31) NPs induced T helper type 1 (Th1)-T helper type 2 (Th2) immune response, whereas immunization by Omp31 load CS (CS/Omp31) NPs induced Th1 immune response. CP/Omp31 NPs elicited protection toward B. melitensis challenge equivalent to the vaccine strain B. melitensis Rev.1. Compared to CS/Omp31 NPs, CP/Omp31 NPs elicited a low increase in protection level against B. melitensis 16 M. In conclusion, the obtained results indicated that CP NPs were potent antigen delivery systems to immunize brucellosis.