Evaluation of immunogenicity of novel multi-epitope subunit vaccines in combination with poly I:C against Brucella melitensis and Brucella abortus infection.

Brucellosis is a worldwide zoonotic disease affecting domestic animals and humans. Due to several safety problems associated with live attenuated vaccines (Rev1 and RB51), it is necessary to produce an efficient and safer vaccine against Brucella. In this study, we evaluated efficacy of two novel multi-peptide vaccine candidates of FliC, 7α-HSDH, BhuA antigens with and without poly I:C adjuvant. Hence, humoral and cellular immune responses and protective efficacy were determined in immunized mice. Our investigation indicated that multi-epitope antigens showed a significant induction of Th1 immunity with high levels of specific IgG (especially the IgG2a), as well as IFN-γ and IL-2 compared to the control group. The addition of poly I:C to multi-epitope antigens improved the humoral and cellular immune responses. The multi-epitope antigens with and without poly I:C also provided cross protection against B. melitensis16M and B. abortus544 infections. The present study suggests that the novel multi-epitope vaccine candidates based on B cell, CD4 and CD8T-cell epitopes of FliC, 7α-HSDH, BhuA proteins would be potential vaccine candidate against B. melitensis and B. abortus infections. Furthermore, poly I:C could be considered as a strong Th1-inducing adjuvant in designing vaccine formulation against brucellosis.