Background: There is an urgent need to find reliable and rapid bovine tuberculosis (bTB) diagnostics in response to the rising prevalence of bTB worldwide. Toll-like receptor 2 (TLR2) recognizes components of bTB and initiates antigen-presenting cells to mediate humoral immunity. Evaluating the affinity of antigens with TLR2 can form the basis of a new method for the diagnosis of bTB based on humoral immunity. Objectives: To develop a reliable and rapid strategy to improve diagnostic tools for bTB. Methods: In this study, we expressed and purified the sixteen bTB-specific recombinant proteins in Escherichia coli. The two antigenic proteins, MPT70 and MPT83, which were most valuable for serological diagnosis of bTB were screened. Molecular docking technology was used to analyze the affinity of MPT70, MPT83, dominant epitope peptide of MPT70 (M1), and dominant epitope peptide MPT83 (M2) with TLR2, combined with the detection results of enzyme-linked immunosorbent assay to evaluate the molecular docking effect. Results: The results showed that interaction surface Cα-atom root mean square deviation of proteins (M1, M2, MPT70, MPT83)-TLR2 protein are less than 2.5 A, showing a high affinity.It is verified by clinical serum samples that MPT70, MPT83, MPT70-MPT83 showed good diagnostic potential for the detection of anti-bTB IgG and M1, M2 can replace the whole protein as the detection antigen. Conclusions Molecular docking to evaluate the affinity of bTB protein and TLR2 combined with ELISA provides new insights for the diagnosis of bTB.

Objective To investigate the prokaryotic expression and immunoreactivity of BspE,a type Ⅳ secretion protein of Brucella,and the effect of recombinant protein BspE on cytokines.Methods According to the BspE gene of Brucella M5-90 published in GenBank,the gene fragments were synthesized by a company and then ligated into PUC57 vector for sequencing.The sequenced gene was cloned into a prokaryotic expression vector pET-28α and transformed.Induced expression was performed in E.coli DE3 competent cells.The obtained target protein was purified by a Ni-NTA affinity column,and its reactogenicity was analyzed by Western blotting.Mouse RAW264.7 cells were treated with 25 g/L BspE recombinant protein for 12,24,48 h,and the control group was treated with the same amount of BSA instead of BspE,and enzyme-linked immunosorbent assay (ELISA) was used to detect interleukin (IL)-1β level.Results The recombinant expresed plasmid of pET-28α-BspE was successfully obtained.The results of Western blotting showed a single band with a relative molecular mass of about 30.1 × 103,and the recombinant protein BspE had good reactogenicity,and IL-1β levels (ng/L)were significantly elevated by the recombinant protein BspE (12 h:43.27 ± 2.13 vs 30.24 ± 1.66,24 h:57.78 ± 3.44 vs 41.22 ± 1.22,48 h:72.52 ± 3.04 vs 46.77 ± 2.75,t =8.38,7.86,10.89,P ＜ 0.05).Conclusions BspE recombinant protein has better immunoreactivity and can increase the expression level of IL-1β in mouse macrophages.This study provides a scientific basis for the role of effector proteins in the pathogenesis of Brucella.

Brucella is an intracellular pathogen that invades a host and settles in its immune cells; however, the mechanism of its intracellular survival is unclear. Modification of small ubiquitin-related modifier (SUMO) occurs in many cellular activities. E2 conjugating enzyme 9 (Ubc9) is the only reported ubiquitin-conjugating enzyme that links the SUMO molecule with a target protein. Brucella's intracellular survival mechanism has not been studied with respect to SUMO-related proteins and Ubc9. Therefore, to investigate the relationship between Brucella melitensis 16M and SUMO, we constructed plasmids and cells lines suitable for overexpression and knockdown of SUMO1 and Ubc9 genes. Brucella 16M activated SUMO1/Ubc9 expression in a time-dependent manner, and Brucella 16M intracellular survival was inhibited by SUMO1/Ubc9 overexpression and promoted by SUMO1/Ubc9 depletion. In macrophages, Brucella 16M-dependent apoptosis and immune factors were induced by SUMO1/Ubc9 overexpression and restricted by SUMO1/Ubc9 depletion. We noted no effect on the expressions of SUMO1 and Ubc9 in B. melitensis 16M lipopolysaccharide-prestimulated mouse RAW264.7 macrophages. Additionally, intracellular survival of the 16M△VirB2 mutant was lower than that of Brucella 16M (p < 0.05). VirB2 can affect expression levels of Ubc9, thereby increasing intracellular survival of Brucella in macrophages at the late stage of infection. Collectively, our results demonstrate that B. melitensis 16M may use the VirB IV secretion system of Brucella to interact with SUMO-related proteins during infection of host cells, which interferes with SUMO function and promotes pathogen survival in host cells.
Animals ; Apoptosis ; Brucella melitensis ; Brucella ; Immunologic Factors ; Macrophages ; Mice ; Plasmids

Background: Brucella infection induces brucellosis, a zoonotic disease. The intracellular circulation process and virulence of Brucella mainly depend on its type IV secretion system (T4SS) expressing secretory effectors. Secreted protein BspJ is a nucleomodulin of Brucella that invades the host cell nucleus. BspJ mediates host energy synthesis and apoptosis through interaction with proteins. However, the mechanism of BspJ as it affects the intracellular survival of Brucella remains to be clarified. Objectives: To verify the functions of nucleomodulin BspJ in Brucella's intracellular infection cycles. Methods: Constructed Brucella abortus BspJ gene deletion strain (B. abortus ΔBspJ) and complement strain (B. abortus pBspJ) and studied their roles in the proliferation of Brucella both in vivo and in vitro. Results: BspJ gene deletion reduced the survival and intracellular proliferation of Brucellaat the replicating Brucella-containing vacuoles (rBCV) stage. Compared with the parent strain, the colonization ability of the bacteria in mice was significantly reduced, causing less inflammatory infiltration and pathological damage. We also found that the knockout of BspJ altered the secretion of cytokines (interleukin [IL]-6, IL-1β, IL-10, tumor necrosis factor-α, interferon-γ) in host cells and in mice to affect the intracellular survival of Brucella. Conclusions BspJ is extremely important for the circulatory proliferation of Brucella in the host, and it may be involved in a previously unknown mechanism of Brucella's intracellular survival.