Effects of major OMPs and LPS of Brucella on the control of activation of bone marrow-derived dendritic cells and proliferation of T-lymphocytes in mice.

Abstract

Background: Brucella outer membrane proteins (OMPs) are highly immunogenic, and lipopolysaccharides (LPS) are also considered significant antigens, making them potential candidates for subunit vaccines.

Aims: To investigate the effects of Brucella OMPs and LPSs on mouse bone marrow-derived dendritic cells (BMDC) activation and T-lymphocyte proliferation.

Methods: BMDC were isolated and cultured in vitro, and subsequently co-cultured with Brucella recombinant proteins (rOMP10, rOMP19, rBP26, rOMP25, and rOMP31), as well as smooth LPS (S-LPS) or rough LPS (R-LPS). The expression of maturation markers on the surface of BMDCs was determined using flow cytometry, while the expression of TLR receptors was determined using RT-PCR. The levels of inflammatory cytokines were measured using iELISA, and the impact on the proliferation of mouse T-lymphocytes was assessed using the MTT method.

Results: The impact of LPS on BMDC maturation, TLRs-mediated cytokine secretion, and antigen presentation was found to be limited. In contrast, rOMP10, rOMP19, and rBP26 were observed to promote BMDC maturation, increase the expression of TLR-2 and TLR-4 mRNA, and activate T-lymphocyte proliferation by significantly increasing the expression of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-6, IL-12) and antigen-presenting molecules. However, rOMP25 and rOMP31 did not promote BMDC maturation, inhibited the expression of MHCI and MHCII antigen-presenting molecules, and increased the expression of inflammation-suppressing cytokines (IL-10 and IL-4), resulting in the inhibition of T-lymphocyte proliferation.

Conclusion: Brucella OMP10, OMP19, and BP26 play an important role in activating the host immune response, while OMP25 together with OMP31 may play a role in Brucella immune escape.