Abstract
Brucellosis is a clinically and economically important disease. Therefore, eradication programs of the disease have been implemented in several countries. One hurdle in these programs is the detection of infected animals at the early stage. Although the protein antigens as diagnostic antigens have recently received attention, the exact mechanisms at the beginning of immune responses are not yet known. Therefore, genes encoding five B. abortus cellular proteins were cloned and the expressed recombinant proteins were purified. The expression of several cytokine genes (IL-1β, IL-4, IL-6, IL-12p40, IFN-γ, TNF-α, and iNOS) was analyzed in bovine peripheral blood mononuclear cells (bPBMC) after stimulation with the recombinant proteins. Three apoptosis-related genes, Bax, Bcl-2, and TLR4, were also included in the analysis to find out the adverse effects of the proteins to the cells. Each protein induced different patterns of cytokine expression depending on the stimulation time and antigen dose. Expression of IL-6, IL-12p40, and IFN-γ was induced with all of the proteins while IL-1β, IL-4, TNF-α, and iNOS gene expression was not. Expression of apoptosis-related genes was not altered except TLR4. These results suggest that the cellular antigens of B. abortus induce both humoral and cellular immunity via the production of IL-6, IL-12p40, and IFN-γ in bPBMC without exerting any adverse effects on the cells.
Highlights
Brucellosis is a highly contagious zoonosis caused by Gram-negative bacteria of the genus Brucella
Induction of inducible nitric oxide synthase (iNOS) gene expression was up-regulated at 12 or 24 h after stimulation of bovine peripheral blood mononuclear cells (bPBMC) with 10 μg of outer membrane protein 28 (OMP28), mdh, tsf, and rocF proteins (p < 0.01) while there was no significant change in the gene expression with 5 μg of all proteins (Figure 2)
The cellular proteins of B. abortus have received increased attention in the development of diagnostic techniques and vaccines given the important roles of these proteins in the early stage of infection [23]
Summary
Brucellosis is a highly contagious zoonosis caused by Gram-negative bacteria of the genus Brucella. This disease affects livestock, wild animals, and humans. Brucellosis causes significant economic losses because it affects animal production (reduced milk production, abortion, delayed conception, and impaired fertility) and because detection of the disease in a region or country causes enactment of international veterinary regulations as well as restrictions on animal movements and trade [1, 3]. Most serological diagnostic methods for detecting Brucella infection use antibodies against common Brucella antigens [5]. Several cellular proteins of B. abortus have been considered new diagnostic antigens because traditional diagnostic methods using Brucella LPS have low specificity due to cross-reactivity with other relevant bacteria such as Yersinia enterocolitica O:9 [10, 11]
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