Multivalent Fusion DNA Vaccine against Brucella abortus

Abstract

As an alternative brucellosis prevention method, we evaluated the immunogenicity induced by new multivalent DNA vaccines in BALB/c mice. We constructed the vaccines by fusion of BAB1_0273 and/or BAB1_0278 open reading frames (ORFs) from genomic island 3 (GI-3) and the Brucella abortus 2308 sodC gene with a link based on prolines and alanines (pV273-sod, pV278-sod, and pV273-278-sod, resp.). Results show that immunization with all tested multivalent DNA vaccines induced a specific humoral and cellular immune response. These novel multivalent vaccines significantly increased the production of IgM, IgG, and IgG2a antibodies as well as IFN-γ levels and the lymphoproliferative response of splenocytes. Although immunization with these multivalent vaccines induced a typical T-helper 1- (Th1-) dominated immune response, such immunogenicity conferred low protection levels in mice challenged with the B. abortus 2308 pathogenic strain. Our results demonstrated that the expression of BAB1_0273 and/or BABl_0278 antigens conjugated to SOD protein can polarize mice immunity to a Th1-type phenotype, conferring low levels of protection.

Figure 1

Peripheral blood antibody production quantified by indirect ELISA. (a) IgM, (b) IgG, and (c) IgG2a, specific against recombinant proteins. Results are plotted as mean ± standard deviation of the inverse of the last dilution before cutting. ^∗P < 0.05, ^∗∗P < 0.01, and ^∗∗∗P < 0.001 indicate statistically significant values.

Figure 2

Lymphoproliferative response. Splenocytes stimulated in vitro with (a) 2 μg/ml or 10 μg/ml of R273S, R278S, or R273-278S recombinant proteins, respectively, and (b) 2 μg/ml or 10 μg/ml of B. abortus 2308 crude Brucella proteins. Results are plotted as mean ± standard deviation. ^∗P < 0.05 and ^∗∗∗P < 0.001 indicate statistically significant values.

Figure 3

Cytokine levels quantified by ELISA sandwich. Production of (a) IFN-γ and (b) IL-4, present in the supernatant of splenocytes stimulated in vitro with 2 or 10 μg/ml of R273S, R278S, or R273-278S recombinant proteins for 72 h. Results are plotted as mean ± standard deviation. ^∗∗∗P < 0.001 indicates statistically significant values.