Cytokines production and toll-like receptors expression in human leukemic monocyte cells, THP-1, stimulated with Brucella abortus cellular antigens

A zoonotic pathogen, Brucella spp. is the causative agent of brucellosis, which results in abortion and loss in milk production in domestic animals, and undulant fever, osteoarticular pain and splenomegaly in humans. Due to the capability of the bacteria to modulate the host cell functions and survive in macrophages, early detection and eradication of the intracellular bacteria has received significant attention. Moreover, understanding the immunological alterations in Brucella infection is crucial to help develop control measures. Cytokines and toll-like receptors (TLRs) are some of the major compounds that play important roles in modulating the innate immunity and acquired immunity in host after infection. In this study, therefore, human leukemic monocyte cells (THP-1 cells) were stimulated with five Brucella abortus cellular components: outer membrane protein 10 (OMP10), outer membrane protein 19 (OMP19), thiamine transporter substrate-binding protein (TbpA), arginase (RocF), and malate dehydrogenase (Mdh). Post stimulation, the cytokine productions and TLR expressions in the cells were evaluated at different time points (12 h and 24 h), and analyzed using ELISA and real time RT-PCR, respectively. In the production of cytokines, it was observed that the production of TNF-α and IL-6 was highly induced in THP-1 cells stimulated with five recombinant protein antigens. Also, TLR8 was induced in a time-dependent manner after stimulation with two recombinant proteins, rOMP19 and rMdh, until 24 h. These results suggest that the two B. abortus antigens, rOMP19 and rMdh, might be involved in TLR8 signaling pathway in THP-1 cells in a time-dependent manner. These two proteins are therefore potentially effective antigen candidates which would help to provide better understandings of the immune responses after Brucella infection.