The Immunogenicity of OMP31 Peptides and Its Protection Against Brucella melitensis Infection in Mice

Bioinformatics approach for structure modeling, vaccine design, and molecular docking of Brucella candidate proteins BvrR, OMP25, and OMP31

Brucellosis is a zoonotic disease with significant economic and healthcare costs. Despite the eradication efforts, the disease persists. Vaccines prevent disease in animals while antibiotics cure humans with limitations. This study aims to design vaccines and drugs for brucellosis in animals and humans, using protein modeling, epitope prediction, and molecular docking of the target proteins (BvrR, OMP25, and OMP31). Tertiary structure models of three target proteins were constructed and assessed using RMSD, TM-score, C-score, Z-score, and ERRAT. The best models selected from AlphaFold and I-TASSER due to their superior performance according to CASP 12 - CASP 15 were chosen for further analysis. The motif analysis of best models using MotifFinder revealed two, five, and five protein binding motifs, however, the Motif Scan identified seven, six, and eight Post-Translational Modification sites (PTMs) in the BvrR, OMP25, and OMP31 proteins, respectively. Dominant B cell epitopes were predicted at (44-63, 85-93, 126-137, 193-205, and 208-237), (26-46, 52-71, 98-114, 142-155, and 183-200), and (29-45, 58-82, 119-142, 177-198, and 222-251) for the three target proteins. Additionally, cytotoxic T lymphocyte epitopes were detected at (173-181, 189-197, and 202-210), (61-69, 91-99, 159-167, and 181-189), and (3-11, 24-32, 167-175, and 216-224), while T helper lymphocyte epitopes were displayed at (39-53, 57-65, 150-158, 163-171), (79-87, 95-108, 115-123, 128-142, and 189-197), and (39-47, 109-123, 216-224, and 245-253), for the respective target protein. Furthermore, structure-based virtual screening of the ZINC and DrugBank databases using the docking MOE program was followed by ADMET analysis. The best five compounds of the ZINC database revealed docking scores ranged from (- 16.8744 to - 15.1922), (- 16.0424 to - 14.1645), and (- 14.7566 to - 13.3222) for the BvrR, OMP25, and OMP31, respectively. These compounds had good ADMET parameters and no cytotoxicity, while DrugBank compounds didn't meet Lipinski's rule criteria. Therefore, the five selected compounds from the ZINC20 databases may fulfill the pharmacokinetics and could be considered lead molecules for potentially inhibiting Brucella's proteins.

Design of multi-epitope vaccine candidate against Brucella type IV secretion system (T4SS)

Brucellosis is a common zoonosis, which is caused by Brucella infection, and Brucella often infects livestock, leading to abortion and infertility. At present, human brucellosis remains one of the major public health problems in China. According to previous research, most areas in northwest China, including Xinjiang, Tibet, and other regions, are severely affected by Brucella. Although there are vaccines against animal Brucellosis, the effect is often poor. In addition, there is no corresponding vaccine for human Brucellosis infection. Therefore, a new strategy for early prevention and treatment of Brucella is needed. A multi-epitope vaccine should be developed. In this study, we identified the antigenic epitopes of the Brucella type IV secretion system VirB8 and Virb10 using an immunoinformatics approach, and screened out 2 cytotoxic T lymphocyte (CTL) epitopes, 9 helper T lymphocyte (HTL) epitopes, 6 linear B cell epitopes, and 6 conformational B cell epitopes. These advantageous epitopes are spliced together through different linkers to construct a multi-epitope vaccine. The silico tests showed that the multi-epitope vaccine was non-allergenic and had a strong interaction with TLR4 molecular docking. In immune simulation results, the vaccine construct may be useful in helping brucellosis patients to initiate cellular and humoral immunity. Overall, our findings indicated that the multi-epitope vaccine construct has a high-quality structure and suitable characteristics, which may provide a theoretical basis for the development of a Brucella vaccine.

Exosomes released by Brucella-infected macrophages inhibit the intracellular survival of Brucella by promoting the polarization of M1 macrophages

Exosomes, membrane vesicles released extracellularly from cells, contain nucleic acids, proteins, lipids and other components, allowing the transfer of material information between cells. Recent studies reported the role of exosomes in pathogenic microbial infection and host immune mechanisms. Brucella-invasive bodies can survive in host cells for a long time and cause chronic infection, which causes tissue damage. Whether exosomes are involved in host anti-Brucella congenital immune responses has not been reported. Here, we extracted and identified exosomes secreted by Brucella melitensis M5 (Exo-M5)-infected macrophages, and performed in vivo and in vitro studies to examine the effects of exosomes carrying antigen on the polarization of macrophages and immune activation. Exo-M5 promoted the polarization of M1 macrophages, which induced the significant secretion of M1 cytokines (tumour necrosis factor-α and interferon-γ) through NF-κB signalling pathways and inhibited the secretion of M2 cytokines (IL-10), thereby inhibiting the intracellular survival of Brucella. Exo-M5 activated innate immunity and promoted the release of IgG2a antibodies that protected mice from Brucella infection and reduced the parasitaemia of Brucella in the spleen. Furthermore, Exo-M5 contained Brucella antigen components, including Omp31 and OmpA. These results demonstrated that exosomes have an important role in immune responses against Brucella, which might help elucidate the mechanisms of host immunity against Brucella infection and aid the search for Brucella biomarkers and the development of new vaccine candidates.

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.

A designed peptide-based vaccine to combat Brucella melitensis, B. suis and B. abortus: Harnessing an epitope mapping and immunoinformatics approach

Vaccines against Brucella abortus, B. melitensis and B. suis have been based on weakened or killed bacteria, however there is no recombinant vaccine for disease prevention or therapy. This study attempted to predict IFN-γ epitopes, T cell cytotoxicity, and T lymphocytes in order to produce a multiepitope vaccine based on BtpA, Omp16, Omp28, virB10, Omp25, and Omp31 antigens against B. melitensis, B. abortus, and B. suis. AAY, GPGPG, and EAAAK peptides were used as epitope linkers, while the PADRE sequence was used as a Toll-like receptor 2 (TLR2) and TLR4 agonist. The final construct included 389 amino acids, and was a soluble protein with a molecular weight of 41.3 kDa, and nonallergenic and antigenic properties. Based on molecular docking studies, molecular dynamics simulations such as Gyration, RMSF, and RMSD, as well as tertiary structure validation methods, the modeled protein had a stable structure capable of interacting with TLR2/4. As a result, this novel vaccine may stimulate immune responses in B and T cells, and could prevent infection by B. suis, B. abortus, and B. melitensis.

Evaluation of Brucellosis Vaccines: A Comprehensive Review

Brucellosis is a bacterial zoonosis caused by Brucella spp. which can lead to heavy economic losses and severe human diseases. Thus, controlling brucellosis is very important. Due to humans easily gaining brucellosis from animals, animal brucellosis control programs can help the eradication of human brucellosis. There are two popular vaccines against animal brucellosis. Live attenuated Brucella abortus strain 19 (S19 vaccine) is the first effective and most extensively used vaccine for the prevention of brucellosis in cattle. Live attenuated Brucella melitensis strain Rev.1 (Rev.1 vaccine) is the most effective vaccine against caprine and ovine brucellosis. Although these two vaccines provide good immunity for animals against brucellosis, the expense of persistent serological responses is one of the main problems of both vaccines. The advantages and limitations of Brucella vaccines, especially new vaccine candidates, have been less studied. In addition, there is an urgent need for new strategies to control and eradicate this disease. Therefore, this narrative review aims to present an updated overview of the available different types of brucellosis vaccines.

Design of a multi-epitope vaccine candidate against Brucella melitensis

Brucella is a typical facultative intracellular bacterium that can cause zoonotic infections. For Brucella, it is difficult to eliminate with current medical treatment. Therefore, a multi-epitope vaccine (MEV) should be designed to prevent Brucella infection. For this purpose, we applied the reverse vaccinology approach from Omp10, Omp25, Omp31 and BtpB. Finally, we obtained 13 cytotoxic T lymphocyte (CTL) epitopes, 17 helper T lymphocyte (HTL) epitopes, 9 linear B cell epitopes, and 2 conformational B cell epitopes for further study. To keep the protein folded normally, we linked AAY, GPGPG, and KK to CTL epitopes, HTL epitopes, and B cell epitopes, respectively. The N-terminal of the vaccine peptide is supplemented with appropriate adjuvants to enhance immunogenicity. To evaluate its immunogenicity, stability, safety, and feasibility, a final MEV containing 806 amino acids was constructed by linking linkers and adjuvants. In addition, molecular docking and molecular dynamics simulations were performed to verify the affinity and stability of the MEV-TLR4. Then, codon adaptation and in silico cloning studies were carried out to identify the possible codons for expressing the MEV. In animal experiments, the results demonstrated that the MEV had high immunogenicity. Collectively, this study provided a theoretical basis for the development of a Brucella vaccine.

Design of a Recombinant Multivalent Epitope Vaccine Based on SARS-CoV-2 and Its Variants in Immunoinformatics Approaches

The development of an effective multivalent vaccine against SARS-CoV-2 variants is an important means to improve the global public health situation caused by COVID-19. In this study, we identified the antigen epitopes of the main global epidemic SARS-CoV-2 and mutated virus strains using immunoinformatics approach, and screened out 8 cytotoxic T lymphocyte epitopes (CTLEs), 17 helper T lymphocyte epitopes (HTLEs), 9 linear B-cell epitopes (LBEs) and 4 conformational B-cell epitopes (CBEs). The global population coverage of CTLEs and HTLEs was 93.16% and 99.9% respectively. These epitopes were spliced together by corresponding linkers and recombined into multivalent vaccine. In silico tests, the vaccine protein was a non-allergen and the docking with TLR-3 molecule showed a strong interaction. The results of immune simulation showed that the vaccine may be helpful to initiate both cellular and humoral immunity against all VOC. The optimistic immunogenicity of the vaccine was confirmed in vivo and in vitro finally. Therefore, our vaccine may have potential protection against SARS-CoV-2 and its variants.

Design of a new multi-epitope vaccine against Brucella based on T and B cell epitopes using bioinformatics methods

Brucellosis is one of the most serious and widespread zoonotic diseases, which seriously threatens human health and the national economy. This study was based on the T/B dominant epitopes of Brucella outer membrane protein 22 (Omp22), outer membrane protein 19 (Omp19) and outer membrane protein 28 (Omp28), with bioinformatics methods to design a safe and effective multi-epitope vaccine. The amino acid sequences of the proteins were found in the National Center for Biotechnology Information (NCBI) database, and the signal peptides were predicted by the SignaIP-5.0 server. The surface accessibility and hydrophilic regions of proteins were analysed with the ProtScale software and the tertiary structure model of the proteins predicted by I-TASSER software and labelled with the UCSF Chimera software. The software COBEpro, SVMTriP and BepiPred were used to predict B cell epitopes of the proteins. SYFPEITHI, RANKpep and IEDB were employed to predict T cell epitopes of the proteins. The T/B dominant epitopes of three proteins were combined with HEYGAALEREAG and GGGS linkers, and carriers sequences linked to the N- and C-terminus of the vaccine construct with the help of EAAAK linkers. Finally, the tertiary structure and physical and chemical properties of the multi-epitope vaccine construct were analysed. The allergenicity, antigenicity and solubility of the multi-epitope vaccine construct were 7.37–11.30, 0.788 and 0.866, respectively. The Ramachandran diagram of the mock vaccine construct showed 96.0% residues within the favoured and allowed range. Collectively, our results showed that this multi-epitope vaccine construct has a high-quality structure and suitable characteristics, which may provide a theoretical basis for future laboratory experiments.

Bioinformatics analysis of candidate proteins Omp2b, P39 and BLS for Brucella multivalent epitope vaccines

This study focuses on analyzing the physicochemical properties, structural characteristics and dominant epitopes of Brucella outer membrane protein 2b (Omp2b), periplasmic binding protein (P39) and Brucella lumazine synthase (BLS) proteins by bioinformatics methods, and to provide a theoretical basis for constructing multi-epitope vaccines. The amino acid sequences of three kinds of proteins were obtained from the UniProt database. The highest frequency alleles in northern China were obtained from the AlleleFrequencies database. Analysis of the physicochemical properties of the proteins by ProtParam online software. Analysis of the secondary structure of the proteins were predicted by SOMPA online software. Using SWISS-MODEL online software constructed and analyzed the tertiary structure of the proteins. Using ABCpred, BepiPred, BCPred and SVMTrip online software analyzed linear B cell epitopes of proteins, The T cell dominant epitope of the protein was analyzed using SYFPEITHI, RANKPEP and IEDB online software. Omp2b was identified three linear B cell dominant epitopes, five CD8⁺ T cell dominant epitopes, and three CD4⁺ T cell dominant epitopes. P39 was identified three linear B cell dominant epitopes, two CD8⁺ T cell dominant epitopes, and two CD4⁺ T cell dominant epitopes. BLS was identified one linear B cell dominant epitope, one CD8⁺ T cell dominant epitope, and two CD4⁺ T cell dominant epitopes. The results indicated that epitope prediction of three Brucella vaccine candidate proteins can provide a theoretical basis for the construction of an ideal multivalent epitope vaccine against Brucella.

Immunoinformatics prediction of OMP2b and BCSP31 for designing multi-epitope vaccine against Brucella

Brucella poses a serious threat to human health. High quality vaccines for Brucella are urgently needed to effectively reduce the incidence of brucellosis. OMP2b and BCSP31 are important component proteins of the Brucella outer membrane and are highly immunogenic. Here, we used the bioinformatics software ProtParam, SOPMA, SWISS-MODEL, Rasmol, BepiPred, SYFPEITHI and IEDB to analyze the structure of these two proteins and predict the epitopes of T cells and B cells. Through analysis, we predicted three Th cell epitopes, seven CTL epitopes, eight B cell epitopes, and one T-B combined epitope of OMP2b protein. Subsequently, we also obtained three Th cell epitopes, six CTL epitopes, nine B cell epitopes and one T-B combined epitope of BCSP31 protein. The T-B combined epitopes and CTL epitopes of OMP2b and those of BCSP31 were synthesized to detect their immunogenicity. The IFN-γ ELISPOT assay showed that the T-B combined epitope peptides of OMP2b and BCSP31 activated Th cell immune responses. ELISA analysis detected the specific antibodies against the T-B combined epitope peptide of OMP2b and BCSP31 in the serum of Brucellosis patients. Additionally, CTL epitope peptide of OMP2b and BCSP31 proteins promoted the secretion of soluble perforin and granzyme B in the culture supernatant. In conclusion, our study shows that the T-B combined epitopes and CTL epitopes of OMP2b and BCSP31 have immunogenicity and immunoreactivity. Our results may lay a theoretical foundation for the development of vaccines against Brucella.