Use of recombinant Brucella outer membrane proteins 19, 25, and 31 for serodiagnosis of bovine brucellosis

Expression of cytokine and Apoptosis-Associated genes in mice bone Marrow-Derived Macrophages stimulated with Brucella recombinant type IV secretion effectors

BACKGROUND

Brucellosis is an economically important infectious caused by most commonly by Brucella. Detection of infected animals at the early stage is important for controlling the disease. The diagnostic antigens, usually protein antigens, have attracted much interest. However, the accurate mechanism of immune response is still unknown. The secretory effectors (BPE005, BPE275, and BPE123) of the type IV secretion system (T4SS) were involved in the intracellular circulation process of Brucella and the immune responses of the host.

METHODS

Genes encoding three B. abortus effector proteins (BPE005, BPE275, and BPE123) of T4SS were cloned and the recombinant proteins were expressed and purified. The purified recombinant proteins were named rBPE005, rBPE275 and rBPE123. Then, the expressions of Th1- and Th2-related cytokine genes were analyzed in mice bone marrow-derived macrophages (BMDMs) after stimulation with rBPE005, rBPE275, and rBPE123. Furthermore, four apoptosis-associated genes (Caspase-3, Caspase-8, Bax, and Bcl-2) were also detected to explore the damage of the proteins to the cells.

RESULTS

Expressions of all Th1- and Th2-related cytokine genes were induced with three proteins, and different cytokine expression patterns induced by each protein depend on the stimulation time and dose of protein. However, expressions of apoptosis-related genes did not change.

CONCLUSION

These results showed that the secreted antigens of Brucella induced an immune reaction via the production of Th1- and Th2-type cytokines in BMDMs without exerting any damage on the cells.

Proteomics Exploration of Brucella melitensis to Design an Innovative Multi-Epitope mRNA Vaccine

Brucellosis is a chronic and debilitating disease in humans, causing great economic losses in the livestock industry. Making an effective vaccine is one of the most important concerns for this disease. The new mRNA vaccine technology due to its accuracy and high efficiency has given promising results in various diseases. The objective of this research was to create a novel mRNA vaccine with multiple epitopes targeting Brucella melitensis. Seventeen antigenic proteins and their appropriate epitopes were selected with immunoinformatic tools and surveyed in terms of toxicity, allergenicity, and homology. Then, their presentation and identification by MHC cells and other immune cells were checked with valid tools such as molecular docking, and a multi-epitope protein was modeled, and after optimization, mRNA was analyzed in terms of structure and stability. Ultimately, the immune system's reaction to this novel vaccine was evaluated and the results disclosed that the designed mRNA construct can be an effective and promising vaccine that requires laboratory and clinical trials.

Serodiagnosis of human brucellosis by an indirect ELISA test using recombinant outer membrane protein 19 kDa (rOMP19) as an antigen

BACKGROUND

Brucellosis remains one of the global health concerns that reemerges in recent years. Delayed or inaccurate diagnosis end to a long treatment duration and financial burden; therefore, finding a good antigen for detection of specific anti-Brucella antibodies is crucial. We intended to evaluate the serodiagnosis value of recombinant Brucella outer membrane protein 19 kDa (rOMP19) using indirect ELISA system compared with Rose Bengal test.

RESULTS

The OMP19 sequence was successfully cloned into pET-28a and produced in E. coli cells (DE3). After extraction and purification of rOMP19, this protein was used for designing indirect ELISA to detect anti-Brucella antibodies in 73 human sera, including 6 brucellosis-positive and 67 brucellosis-negative samples. The accuracy of rOMP19 ELISA was evaluated by receiver operating characteristic (ROC) curve and then compared with Rose Bengal plate test and a commercial anti-IgG Brucella ELISA kit. In comparison with Rose Bengal plate test, the area under the ROC curve was 0.985 (95% CI, 0.96-1.00). From coordinates of the curve, the optimal cut-off value was selected at 0.147, in which the diagnostic sensitivity was 100%, and the specificity was 94%. At this cut-off point, 10 samples were diagnosed as positive (6 true positives and 4 false positives), while negative samples were all correctly diagnosed. The results of our designed rOMP19 ELISA was the same as data obtained from commercial ELISA kit, which applied LPS as an antigen.

CONCLUSIONS

We concluded that OMP19 is an efficient antigen for the serodiagnosis of human brucellosis.

Brucellosis detection and the role of Brucella spp. cell wall proteins

Brucellosis remains an endemic zoonotic disease in many developing countries, causing great harm to public health and devastating losses to livestock. One of the main reasons for the low effectiveness of anti-brucellosis measures is the lack of reliable methods for diagnosing infected animals throughout their lifespan. Classical serological tests, such as the tube agglutination test, rose Bengal plate test, and complement fixation test, as well as commercial enzyme-linked immunosorbent assay kits, are based on the detection of antibodies to the cell wall polysaccharide antigens of Brucella spp. smooth strains. As a result, they do not exclude cross-reactions with related bacteria and fail to differentiate between infected and vaccinated animals. Over the past decades, many attempts have been made to identify immunoreactive and pathogen-specific protein antigens. To date, several studies have investigated Brucella spp. recombinant proteins, including cell wall proteins, as the best antigens for diagnosing brucellosis in animals and humans. However, the available results on the specificity and sensitivity of serological tests based on cell wall proteins are ambiguous and sometimes contradictory. This review aims to provide an overview of the current state of knowledge of the diagnostic value of outer membrane and/or periplasmic proteins of Brucella spp. The goal is to identify future developments that may lead to reliable antigens for serological tests.

The outer membrane proteins based seroprevalence strategy for Brucella ovis natural infection in sheep

Introduction

The diagnosis of brucellosis largely relies on tiger red plate agglutination test (RBPT). However, it is difficult to distinguish between natural infection antibody positive and vaccination antibody positive, nevertheless, the identification of specific Brucella species natural infection.

Methods

Here, we analyzed the structure of main outer membrane proteins (OMPs), OMP25 and OMP31 from Brucella ovis (B. ovis) and Brucella melitensis (B. melitensis), which are the main pathogens of sheep brucellosis, and found the OMP25 and OMP31 could be used as the differential antigens for B. ovis and B. melitensis antibody. Then we expressed the OMP25 from B. ovis (OMP25o) and OMP31 from B. melitensis (OMP31m).

Results

They have equally efficiency in antibody detection of vaccinated sheep serum, consistent with the RBPT results. However, through epidemiological investigations, we found some RBPT positive samples were negative by the OMP31m based serum antibody detection, but these samples gave positive results by the OMP25o. We verified these OMP31m negative but OMP25o positive samples by B. ovis and B. melitensis specific primers based PCR detection, and all these samples were B. melitensis negative. However, four out of six samples are B. ovis positive. These results showed that we could use the OMP25o and OMP31m to diagnose sheep brucellosis antibody, especially to discriminate the infection of the B. ovis.

Discussion

Currently, China has not yet approved a vaccine based on B. ovis and B. ovis positive samples should be naturally infected. There should be some implicit transmission of B. ovis in Jilin province. Further epidemiological investigation should be conducted to monitor the B. ovis natural infection.

False Positives in Brucellosis Serology: Wrong Bait and Wrong Pond?

This review summarizes the status of resolving the problem of false positive serologic results (FPSR) in Brucella serology, compiles our knowledge on the molecular background of the problem, and highlights some prospects for its resolution. The molecular basis of the FPSRs is reviewed through analyzing the components of the cell wall of Gram-negative bacteria, especially the surface lipopolysaccharide (LPS) with details related to brucellae. After evaluating the efforts that have been made to solve target specificity problems of serologic tests, the following conclusions can be drawn: (i) resolving the FPSR problem requires a deeper understanding than we currently possess, both of Brucella immunology and of the current serology tests; (ii) the practical solutions will be as expensive as the related research; and (iii) the root cause of FPSRs is the application of the same type of antigen (S-type LPS) in the currently approved tests. Thus, new approaches are necessary to resolve the problems stemming from FPSR. Such approaches suggested by this paper are: (i) the application of antigens from R-type bacteria; or (ii) the further development of specific brucellin-based skin tests; or (iii) the application of microbial cell-free DNA as analyte, whose approach is detailed in this paper.

Study on antigenic protein Omp2b in combination with Omp31 and BP26 for serological detection of human brucellosis

BACKGROUND

Brucellosis is a very common zoonosis in certain localized areas worldwide, with a high prevalence in most developing countries. The detection of brucellosis still faces many challenges such as the need for more sensitive and specific diagnostic antigens.

METHODS

To evaluate the efficacy of Brucella outer membrane proteins (Omps) Omp2b in combination with omp31 and BP26 as diagnostic antigens for the serological detection of human brucellosis, these proteins were prepared by a prokaryotic expression system. Human brucellosis-positive and-negative sera were collected, and the detection effects of the diagnostic antigens were evaluated using an established indirect ELISA (iELISA) method. Receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC), true positives, true negatives, false positives, false negatives, accuracy, positive predictive value, negative predictive value, analytical specificity, and sensitivity were obtained to evaluate the effectiveness of Omp2b and antigen combinations.

RESULTS

The iELISA results showed that the AUC of the antigenic proteins was 0.9100, 0.9387, 0.9343, and 0.9448, respectively, and that the combination of Omp31 and BP26 improved the accuracy and was superior to that of Omp2b alone. Analysis at the determined cut-off values showed that the analytical sensitivity of the assay was 0.8739 (95% CI:0.7974-0.9293) and the analytical specificity was 0.8539 (95% CI:0.7632-0.9199) when using Omp2b alone and 0.8649 when using the combination of Omp2b + BP26 (95% CI:0.7869-0.9223) with an analytical specificity of 0.9213 (95% CI:0.8446-0.9678) and 0.8468 (95% CI:0.7662-0.9082) and an analytical sensitivity of 0.9101 (95% CI:0.8305-0.9604). When Omp2b + Omp31 + BP26 was combined, the analytical sensitivity and specificity were 0.8559 (95% CI:0.7765-0.9153) and 0.9326 (95% CI:0.8590-0.9749), respectively. Protein antigens, including antigen combinations, did not cross-react with Yersinia enterocolitica O9 and E. coli O157: H7, indicating that their specificity was better than that of lipopolysaccharide (LPS).

CONCLUSIONS

Compared with individual Omp2b, antigen combinations improved the effectiveness in detecting brucellosis, but were still not as effective as LPS antigen. Omp2b, combined with Omp31 and BP26 as diagnostic antigens, can be used to detect human brucellosis.

Evaluation of the Fluorescence Polarization Assay for the Diagnosis of Brucellosis in Goat Milk

The milk ring test is a detection assay for antibodies against Brucella in bovine milk. It has good sensitivity but tends to give false positive results. In this study, we standardized the application of the fluorescence polarization assay (FPA) for the detection of antibodies against B.melitensis in goat milk. We obtained negative serum and milk samples from healthy goat flocks in the northern zone of Nuevo León. Positive milk and negative, weak, and strong controls were obtained by mixing volumes of positive control serum with negative control milk. Milk samples were treated with citric acid, after which an FPA was performed. Results were then compared with the Rose Bengal test and the FPA in serum. Milk treatment allowed the quantification of antibodies in samples. Significant differences were found between the 2%, 4%, and 6% groups, compared with the control group (F3, 67 = 17.45, p < 0.0001) but not between the 2% and 4% groups (p = 0.0718). The cut-off value was 74.1 mP, with a sensitivity (Se) of 95% and a specificity (Sp) of 100%. Se and Sp values in field milk samples were 84% and 74.55%, respectively. Despite the FPA test on milk samples showed lower Se and Sp than the FPA test on serum samples, its cutoff may be adjusted. It may be recommended as a screening test in goat milk and become useful for the control and eradication of the disease.

Evaluation of chimeric proteins for serological diagnosis of brucellosis in cattle

Background and Aim

An accurate diagnosis of Brucella-infected animals is one of the critical measures in eradication programs. Conventional serological tests based on whole-cell (WC) antigens and detecting antibodies against pathogen-associated lipopolysaccharide might give false-positive results due to the cross-reactivity with other closely related bacteria. This study evaluated the serological potential of Brucella spp. chimeric outer membrane proteins (Omps) as antigens in an indirect enzyme-linked immunosorbent assay (i-ELISA).

Materials and Methods

The chimeric gene constructs of the most immunodominant regions of Brucella Omps 25+31, 25+19, and 19+31 were cloned into the pET28a expression vectors and transformed into Escherichia coli BL21 (DE3). The serological potential of chimeric proteins compared with single recombinant Omps (rOmps)19, 25, and/or 31 were studied on blood serum samples of (i) a rabbit immunized with killed Brucella abortus 19WC, (ii) mice immunized with single rOmps, (iii) cows seropositive for brucellosis by rose Bengal test, and (iv) cattle naturally and/or experimentally infected with brucellosis.

Results

E. coli BL21 actively produced Brucella chimeric rOmps, the concentration of which reached a maximum level at 6 h after isopropyl-b-D-1-thiogalactopyranoside stimulation. Target proteins were antigenic and expressed in an active state, as recognized by rabbit anti-B. abortus antibodies in an i-ELISA and western blotting. Murine antibodies against the single rOmps reacted with chimeric antigens, and conversely, antichimeric antibodies found their epitopes in single proteins. Brucella chimeric rOmps showed higher antigenicity in blood sera of seropositive cattle kept in the hotbed of the infection and/or experimentally challenged with brucellosis than single proteins.

Conclusion

Brucella chimeric recombinant outer membrane proteins could be a potential antigen candidate for developing an ELISA test for accurate diagnosis of bovine brucellosis.