Immunological effects of two new nanovaccines against Brucella based on OPS and LPS antigens conjugated with PLGA nanoparticles

Abstract The risk of catching brucellosis and the absence of effective human vaccines has led to the use of new strategies to produce new vaccines against infections caused by this bacterium. In this study, the effect of two new designed nanovaccines on the production of immunoglobulins and their proper functions was investigated. Firstly, the production of immunoglobulins in the serum of the mouse model after three vaccination periods with lipopolysaccharide and oligopolysaccharide antigens in conjugation with PLGA nanoparticles were studied. The mice were divided into 6 groups and each group received LPS-PLGA, OPS-PLGA, LPS, OPS, PLGA and PBS separately. Immunoglobulin titers were measured every two weeks after each vaccination period. Two weeks after the last vaccination, opsonophagocytosis test were performed to evaluate the efficacy and function of produced immunoglobulins. In order to investigate the protective effect of nanovaccines in vivo, the mice were challenged with Brucella abortus bacteria. Immune responses have increased on immunoglobulin production after each vaccination period. The results of the opsonophagocytosis assay showed that produced immunoglobulins have the superior performance to antibodies produced against the pure antigens. By performing the challenge assay, it was found that the immune system of mice receiving new nanovaccines were able to remove more bacteria from the body of mice. In general, it can be concluded that both new prepared nanovaccines can be considered to improve the immunization process in animals and humans against brucellosis although LPS-PLGA conjugate creates more immunogenicity compared to OPS-PLGA nanovaccine.