Evaluation of the Immunogenecity of a Complex of Recombinant Brucella Proteins In Vitro

Brucellosis is a zoonotic disease caused by Brucella. In the Russian Federation, a live vaccine based on the attenuated strain B. abortus 19BA is used to prevent brucellosis in humans. However, pronounced reactogenicity and the likelihood of developing an infectious process after immunization makes the creation of a safe subunit vaccine an urgent task. For this purpose, we created 47 recombinant brucellosis proteins and assessed their vaccine potential on a mouse cell culture. The aim of the study was to evaluate the immunogenic properties of recombinant Brucella proteins on cell culture and serum of BALB/c mice immunized with a Brucella vaccine strain. Using reverse vaccinology methods, candidate brucellosis proteins were identified, and technology for their production and purification was developed. Forty-seven single and fused recombinant proteins were obtained in the E. coli system of optimal concentration and purity for further use in immune assays. To assess the immunogenicity of recombinant proteins, BALB/c mice were immunized with the B. abortus 19BA vaccine strain, and the blood serum and spleens of the animals were collected on the 30th day of infection. The proteins were used as specific inducers for stimulating lymphocytes in in vitro experiments and antigens for determining serum antibody titers in immune and intact mice. The levels of IFN-γ and IL-4 cytokines in lymphocyte cell supernatants, as well as serum-specific antibody titers, were analyzed by enzyme immunoassay. The ability of 47 recombinant brucellosis proteins to induce the formation of humoral and cellular immune responses was assessed. As a result, 41 proteins activating the synthesis of IFN-γ and eight proteins to which IgG antibodies are formed were identified. Brucellosis proteins capable of inducing a pronounced immune response in immunocompetent cells have been obtained and identified. These proteins can be considered as possible candidates for inclusion in vector, DNA, and subunit vaccines against brucellosis in humans.