Immunological evaluation of Brucella antigens formulated with two agonists of toll-like receptor 4 and 3 against brucellosis in BALB/c mice.

Development of a safe and effective brucellosis vaccine has been faced with a number of challenges, such as poor immunogenicity, so identification of appropriate formulations of antigens and adjuvants is crucial to overcome these challenges. The aim of this study is to evaluate the capacity of FliC, 7α-HSDH, BhuA antigens and two multi-epitope from these antigens with poly I:C+MPL adjuvants in eliciting immune responses against B. melitensis and B. abortus in BALB/c mice. FliC, 7α-HSDH, BhuA, poly B and poly T antigens both with and without adjuvant, significantly increased specific antibody titers, with IgG2a levels predominating over IgG1. Our results also showed a significant level of IFN-γ and IL-2 production, alongside enhanced T-cell proliferation in response to antigens and antigens-adjuvant formulations, indicating the induction of Th1-biased immune responses. Additionally, antigens administered with or without the poly I:C and MPL adjuvant conferred significant protection against infections with Brucella melitensis 16M and Brucella abortus 544. The adjuvanted formulations elicited stronger immune responses and greater protective efficacy. Therefore, this study suggests that these antigens combined with poly I:C and MPL represent promising candidates for the development of effective vaccines against B. melitensis and B. abortus infections.