A DNA vaccine coding for the Brucella outer membrane protein 31 confers protection against B. melitensis and B. ovis infection by eliciting a specific cytotoxic response

A subunit vaccine based on Brucella rBP26 induces Th1 immune responses and M1 macrophage activation

Brucellosis is a global zoonotic infection caused by Brucella bacteria, which poses a significant burden on society. While transmission prevention is currently the most effective method, the absence of a licenced vaccine for humans necessitates the urgent development of a safe and effective vaccine. Recombinant protein-based subunit vaccines are considered promising options, and in this study, the Brucella BP26 protein is expressed using prokaryotic expression systems. The immune responses are evaluated using the well-established adjuvant CpG-ODN. The results demonstrate that rBP26 supplemented with a CpG adjuvant induces M1 macrophage polarization and stimulates cellular immune responses mediated by Th1 cells and CD8 + T cells. Additionally, it generates high levels of rBP26-specific antibodies in immunized mice. Furthermore, rBP26 immunization activates, proliferates, and produces cytokines in T lymphocytes while also maintaining immune memory for an extended period of time. These findings shed light on the potential biological function of rBP26, which is crucial for understanding brucellosis pathogenesis. Moreover, rBP26 holds promise as an effective subunit vaccine candidate for use in endemic areas.

Immunopathology of early and advanced epididymis lesions caused by Brucella ovis in rams

Ovine brucellosis is an infectious disease that causes alterations in the reproductive tract in ram and abortion in ewes. Their negative economic impact in ovine production warrants a thorough understanding the interactions between B. ovis and the host. Here, epididymis lesions of rams infected by B. ovis were histopathologically staged into early and advanced. Expression by immunohistochemistry of Brucella antigens, inflammatory cell markers (CD3, CD79αcy) and cytokines (IFN-γ, TNF-α, TGF-β1) was assessed in both stages. Early lesions were characterized by epithelial changes, interstitial inflammation, and mild fibrosis; whereas advanced lesions displayed caseous granulomas containing numerous macrophages, multinucleated giant cells, lymphocytes, and plasma cells. Expression of Brucella antigens were observed in both stages. The cellular response in B. ovis lesions were predominantly of T-cells (CD3+) whereas low numbers of B-cells and plasma cells (CD79αcy+) were present in both early and advanced lesions. IFN-γ was expressed by lymphocytes in early lesions suggesting that the adaptive immune response against B. ovis is initiated by Th1 cells, this response was also preserved in advanced stages. Expression of TNF-α was observed in neutrophils of epithelial microabscesses and intraepithelial T-cells of early lesions suggesting a promotion of neutrophil phagocytosis triggered by TNF-α. On the other hand, advanced lesions showed a reduction of TNF-α expression which may permit B. ovis persistence in granulomas. Lastly, TGF-β1 expression (fibroblast, macrophages and less in lymphocytes) were increased with time, suggesting that B. ovis promotes TGF-β1 secretion promoting chronicity of the lesions.

Multi-Epitope Vaccine Candidates Associated with Mannosylated Chitosan and LPS Conjugated Chitosan Nanoparticles Against Brucella Infection

One promising approach to increase protection against infectious diseases is to use adjuvants that can selectively stimulate the immune responses. In this study, multi-epitope antigens associated with LPS loaded chitosan (LLC) as toll-like receptor agonist or mannosylated chitosan nanoparticle (MCN) as vaccine delivery system were evaluated for their ability to stimulate immune responses to Brucella infection in mice model. Our results indicated that the addition of MCN to our vaccine formulations significantly elicited IFN-γ and IL-2 cytokines and antibody titers, in comparison with the non-adjuvanted vaccine candidates. The present results indicated that multi-epitopes and their administration with LLC or MCN induced Th1 immune response. In addition, vaccine candidates containing MCN provided high percentage of protection against B. melitensis and B. abortus infection. Our results provided support to previous reports indicating that MCNs are attractive adjuvants and addition of this adjuvant to multi-epitopes antigens play an important role in the development of vaccine against Brucella.

Novel multi-epitope vaccine against bovine brucellosis: approach from immunoinformatics to expression

Brucellosis is a zoonotic caused by the Brucella which is a well-known infectious disease agent in domestic animals and if transmitted, it can cause infection in humans. Because brucellosis is contagious, its control depends on the eradication of the animal disease in farms. There are two vaccines based on the killed and/or weakened bacteria against B. melitensis and B. abortus, but no recombinant vaccine is available for preventing the disease. The present study was designed to develop a multi-epitope vaccine against of B. melitensis and B. abortus using virB10, Omp31 and Omp16 antigens by the prediction of T lymphocytes, T cell cytotoxicity and IFN-γ epitopes. 50S L7/L12 Ribosomal protein from Mycobacterium tuberculosis was used as a bovine TLR4 and TLR9 agonist. GPGPG, AAY and KK linkers were used as a linker. Brucella construct was well-integrated in the pET-32a Shuttle vector with BamHI and HindIII restriction enzymes. The final construct contained 769 amino acids, that it was soluble protein of about ∼82 kDa after expression in the Escherichia coli SHuffle host. Modeled protein analysis based on the tertiary structure validation, molecular docking studies, molecular dynamics simulations results like RMSD, Gyration and RMSF as well as MM/PBSA analysis showed that this protein has a stable construct and is capable being in interaction with bovine TLR4 and TLR9. Analysis of the data obtained suggests that the proposed vaccine can induce the immune response by stimulating T- and B-cells, and may be used for prevention and remedial purposes, against B. melitensis and B. abortus.Communicated by Ramaswamy H. Sarma.

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.

Proteomic and Antibody Profiles Reveal Antigenic Composition and Signatures of Bacterial Ghost Vaccine of Brucella abortus A19

Brucellosis is an important zoonotic disease that causes great economic losses. Vaccine immunisation is the main strategy for the prevention and control of brucellosis. Although live attenuated vaccines play important roles in the prevention of this disease, they also have several limitations, such as residual virulence and difficulty in the differentiation of immunisation and infection. We developed and evaluated a new bacterial ghost vaccine of Brucella abortus A19 by a new double inactivation method. The results showed that the bacterial ghost vaccine of Brucella represents a more safe and efficient vaccine for brucellosis. We further characterised the antigenic components and signatures of the vaccine candidate A19BG. Here, we utilised a mass spectrometry-based label-free relative quantitative proteomics approach to investigate the global proteomics changes in A19BGs compared to its parental A19. The proteomic analysis identified 2014 proteins, 1116 of which were differentially expressed compared with those in A19. The common immunological proteins of OMPs (Bcsp31, Omp25, Omp10, Omp19, Omp28, and Omp2a), HSPs (DnaK, GroS, and GroL), and SodC were enriched in the proteome of A19BG. By protein micro array-based antibody profiling, significant differences were observed between A19BG and A19 immune response, and a number of signature immunogenic proteins were identified. Two of these proteins, the BMEII0032 and BMEI0892 proteins were significantly different (P < 0.01) in distinguishing between A19 and A19BG immune sera and were identified as differential diagnostic antigens for the A19BG vaccine candidate. In conclusion, using comparative proteomics and antibody profiling, protein components and signature antigens were identified for the ghost vaccine candidate A19BG, which are valuable for further developing the vaccine and its monitoring assays.

Brucella antigens (BhuA, 7α-HSDH, FliC) in poly I:C adjuvant as potential vaccine candidates against brucellosis

A promising strategy for controlling animal brucellosis is vaccination with commercial vaccine strains (Brucella melitensis Rev.1 and Brucella abortus RB51). Owing to safety concerns associated with these vaccines, developing a more effective and safe vaccine is essential. In this study, we examined the capacity of BhuA, 7α-HSDH or FliC antigens in the presence or absence of adjuvant in eliciting immune responses against brucellosis. After cloning, expression and purification, these proteins were used to examine immunologic responses. All immunized mice induced a vigorous IgG, with a predominant IgG2a response. Moreover, splenocytes of immunized mice proliferated and produced IL-2 and IFN-γ, suggesting the induction of cellular immunity. The high IgG2a/IgG1 ratio and IL-2 and IFN-γ indicated a Th1-oriented immune response in test groups. BhuA-, 7α-HSDH- or FliC- poly I:C formulations were the most effective at inducing Th1 immune response compared to groups immunized with naked proteins. Immunization with proteins protected mice against B. melitensis 16M and B. abortus 544. The proteins in adjuvant induced higher levels of protection than proteins only and exhibited similar degree of protection to live attenuated vaccines. Our results, for first time, introduced five potential candidates for subunit vaccine development against B. melitensis and B. abortus infection.

Evaluation of the immunogenicity and efficacy of a chimeric OMP25-OMP31 antigen in BALB/c mice

Brucellosis is a zoonotic disease causes by Brucella bacteria. So far, there is not any efficient treatment for this infectious disease in animals, although subunit vaccines can be a safe alternative. To this aim, we have designed a new chimeric OMP25-OMP31 antigen formulated in Chitosan nanoparticles and studied its protective efficiency in vivo. OMP25-OMP31 was produced using spliced overlap extension by polymerase chain reaction and the 3D protein structure and antigenic ability were predicted using computational tools. In addition, the humoural and cellular immune responses were measured by ELISA in six different experimental groups. The immune response showed chimeric rOMP25-OMP31 antigen-induced higher titers of IFN-γ and TNF-α cytokines, while the lowest amount of IL-4 was dedicated to itself. Also, rOMP25-OMP31 stimulated higher titer of IgG than individual injection of rOMP25 and rOMP31 treatments and the cell proliferation assay demonstrated the vaccination with rOMP25-OMP31 elicits a vigorous antigen-specific cell proliferative. In addition, the challenge experiment showed immunised mic stimulated a higher level of protection than negative controls. Overall, the results of rOMP25-OMP31 could be promising for considering chimeric constructs as a feasible vaccine candidate for further investigations against brucellosis.

When the Going Gets Rough: The Significance of Brucella Lipopolysaccharide Phenotype in Host-Pathogen Interactions

Brucella is a facultatively intracellular bacterial pathogen and the cause of worldwide zoonotic infections, infamous for its ability to evade the immune system and persist chronically within host cells. Despite the frequent association with attenuation in other Gram-negative bacteria, a rough lipopolysaccharide phenotype is retained by Brucella canis and Brucella ovis, which remain fully virulent in their natural canine and ovine hosts, respectively. While these natural rough strains lack the O-polysaccharide they, like their smooth counterparts, are able to evade and manipulate the host immune system by exhibiting low endotoxic activity, resisting destruction by complement and antimicrobial peptides, entering and trafficking within host cells along a similar pathway, and interfering with MHC-II antigen presentation. B. canis and B. ovis appear to have compensated for their roughness by alterations to their outer membrane, especially in regards to outer membrane proteins. B. canis, in particular, also shows evidence of being less proinflammatory in vivo, suggesting that the rough phenotype may be associated with an enhanced level of stealth that could allow these pathogens to persist for longer periods of time undetected. Nevertheless, much additional work is required to understand the correlates of immune protection against the natural rough Brucella spp., a critical step toward development of much-needed vaccines. This review will highlight the significance of rough lipopolysaccharide in the context of both natural disease and host–pathogen interactions with an emphasis on natural rough Brucella spp. and the implications for vaccine development.

Registered Influenza Viral Vector Based Brucella abortus Vaccine for Cattle in Kazakhstan: Age-Wise Safety and Efficacy Studies

A novel influenza viral vector based Brucella abortus vaccine (Flu-BA) was introduced for use in cattle in Kazakhstan in 2019. In this study, the safety and efficacy of the vaccine was evaluated in male and female cattle at different ages, and during pregnancy as a part of its registration process. Our data demonstrated that the Flu-BA vaccine was safe after prime or booster vaccination in calves (5–7 months old male and female), heifers (15–17 months old) and cows (6–7 years old) and was not abortogenic in pregnant animals. A mild, localized granuloma was observed at the Flu-BA injection site. Vaccinated animals did not show signs of influenza infection or reduced milk production in dairy cows, and the influenza viral vector (IVV) was not recovered from nasal swabs or milk. Vaccinated animals in all age groups demonstrated increased IgG antibody responses against Brucella Omp16 and L7/L12 proteins with calves demonstrating the greatest increase in humoral responses. Following experimental challenge with B. abortus 544, vaccinates demonstrated greater protection and no signs of clinical disease, including abortion, were observed. The vaccine effectiveness against B. abortus 544 infection was 75, 60 and 60%, respectively, in calves, heifers and adult cows. Brucella were not isolated from calves of vaccinated cattle that were experimentally challenged during pregnancy. Our data suggests that the Flu-BA vaccine is safe and efficacious in cattle, including pregnant animals; and can therefore be administered to cattle of any age.

Recombinant Lactococcus Lactis Displaying Omp31 Antigen of Brucella melitensis Can Induce an Immunogenic Response in BALB/c Mice

Since Brucella infection mostly occurs through the mucosal surfaces, immune response induced by vaccine that is delivered by a way of mucosal route can be drastically enhanced to control the brucellosis. Omp31is the major outer membrane protein of Brucella, and is considered as a protective antigen against Brucella infection. Accordingly, Lactococcus lactis has been used as an antigen-delivering vector to develop a vaccine-induced mucosal response for having a safer vaccination against brucellosis. A designed omp31 gene fused to the usp45 signal peptide and M6 cell wall anchor was sub cloned in the pNZ7021 expression vector, and a recombinant L. lactis displaying Omp31 was constructed. Omp31 protein expression was confirmed using Western blotting and immunofluorescence analysis. Animals were orally and intraperitoneally immunized with live or killed L. lactis expressing Omp31, respectively. The humoral and cellular immune responses were evaluated by measuring the specific cytokines and antibodies. sIgA, serum IgA, IgM, and total IgG antibodies significantly increased in the mice immunized with live recombinant L. lactis expressing Omp31 and also serum IgM, and total IgG antibodies significantly increased in mice immunized with killed recombinant L. lactis expressing Omp31. Among IgG subtypes, IgG2a response was significantly higher in both groups compared to IgG1. In mice groups immunized with recombinant L. lactis, the IFN-γ and IL-10 level elevated; however, there was no change in the level of IL-4. These results indicated that recombinants L. lactis induce both humoral and cellular immune responses in mice, and also vaccines based on L. lactis-derived live carriers are promising interventions against Brucella melitensis infections.

Development of Brucella melitensis Rev.1 ΔOmp19 mutants with DIVA feature and comparison of their efficacy against three commercial vaccines in a mouse model

Brucella is an intracellular zoonotic pathogen that can affect many hosts. Brucella melitensis Rev.1 is a live attenuated, is one of the most effective vaccine strain against brucellosis. It can be used safely in sheep, goats, and even cattle. Although many studies are available on this topic, there is no effective vaccine strain for sheep and goats that distinguishes the antibody titer produced between the field infections and vaccinations. Outer membrane protein 19 (Omp 19) is both virulent and a protective antigen found on the cell-wall of the Brucella strain. In this study, used the suicide plasmid pJQ200KS, which contained homologous region without Omp19 Open Reading Frame (ORF) that was transferred to B. melitensis Rev.1 and further transformed into spheroplasts along with penicillin, ampicillin, and glycine by electroporation. To obtain a mutant vector from Escherichia coli, we used the heat shock transformation method along with the blue-white colony screening using X-gal media, whereas for the gene transfer in Brucella, we used electroporation. A scanning electron microscope (S.E.M) was used to observe the spheroplast transformation while the mutant vector and deletion mutants were confirmed through PCR and sequence analysis. In the mouse model efficacy trials, three commercial vaccines were found to comply with the OIE standards. Although the deletion mutants 19 and 44/10 had similar efficiency as the commercial vaccines in terms of stimulation power, the ELISA test with Omp19 protein showed the same results as the negative control. The Rev.1 Omp19 deletion mutants obtained in this study contained sufficient residual virulence, and their protective immunity was similar to the commercial vaccines. The study showed that a vaccine prepared using a B. melitensis Rev.1 ΔOmp19 can act as a marker vaccine or differentiate infected from vaccinated animals (DIVA) through the ELISA test that detects the Omp19 protein.

Efficient Immunization of BALB/c Mice against Pathogenic Brucella melitensis and B. ovis: Comparing Cell-Mediated and Protective Immune Responses Elicited by pCDNA3.1 and pVAX1 DNA Vaccines Coding for Omp31 of Brucella melitensis

Background

Brucella spp. are intracellular pathogens, therefore cell-mediated immunity is the main response to inhibit survival and growth of the bacteria in vertebrate host.

Objective

Many eukaryotic plasmid vectors are being used in setting up DNA vaccines which may show different efficiencies in same conditions. This is important in designing the vaccines and immunization strategies. We looked into the probable differences of immune responses induced by different eukaryotic DNA plasmid vectors (pcDNA3.1 and pVAX1) harboring the same Omp31 gene of B. melitensis.

Materials and Methods

Female BALB/c mice were immunized with pcDNA -omp31 and pVAX-omp31 and further boosted with recombinant Omp31. Subclasses of specific serum IgG against the rOmp31 were measured by ELISA. Cytokines responses to rOmp31 in Splenocyte cultures of the immunized mice were evaluated by measuring the production of IL-4, IL-10, IL-12 and IFN-γ. Protective responses of the immunized mice were evaluated by intraperitoneal challenge with pathogenic Brucella melitensis 16M and Brucella ovis PA76250.

Results

Both DNA vaccine candidates conferred potent Th1-type responses with higher levels of cytokines and immunoglobulins observed in mice immunized with pVAX-omp31. Although pcDNA-omp31 and pVAX-omp31 both elicited protective immunity, mice immunized with the latter showed a higher protection against both B. melitensis and B. ovis PA76250.

Conclusion

The results of this study highlight the significant differences between efficiency of diverse plasmid backbones in DNA vaccines which code for an identical antigen. Comparing various plasmid vectors should be considered as an essential part of the studies aiming construction of DNA vaccines for intracellular pathogens.

Nanoparticle-Based Vaccines for Brucellosis: Calcium Phosphate Nanoparticles-Adsorbed Antigens Induce Cross Protective Response in Mice

Introduction

Vaccine formulation with appropriate adjuvants is an attractive approach to develop protective immunity against pathogens. Calcium phosphate nanoparticles (CaPNs) are considered as ideal adjuvants and delivery systems because of their great potential for enhancing immune responses. In the current study, we have designed nanoparticle-based vaccine candidates to induce immune responses and protection against B. melitensis and B. abortus.

Materials and Methods

For this purpose, we used three Brucella antigens (FliC, 7α-HSDH, BhuA) and two multi-epitopes (poly B and poly T) absorbed by CaPNs. The efficacy of each formulation was evaluated by measuring humoral, cellular and protective responses in immunized mice.

Results

The CaPNs showed an average size of about 90 nm with spherical shape and smooth surface. The CaPNs-adsorbed proteins displayed significant increase in cellular and humoral immune responses compared to the control groups. In addition, our results showed increased ratio of specific IgG2a (associated with Th1) to specific IgG1 (associated with Th2). Also, immunized mice with different vaccine candidate formulations were protected against B. melitensis 16M and B. abortus 544, and showed same levels of protection as commercial vaccines (B. melitensis Rev.1 and B. abortus RB51) except for BhuA-CaPNs.

Discussion

Our data support the hypothesis that these antigens absorbed with CaPNs could be effective vaccine candidates against B. melitensis and B. abortus.

Mannosylated chitosan nanoparticles loaded with FliC antigen as a novel vaccine candidate against Brucella melitensis and Brucella abortus infection

Brucellosis is a worldwide bacterial zoonosis disease. Live attenuated Brucella vaccines have several drawbacks. Thus development of a safe and effective vaccine for brucellosis is a concern of many scientists. FliC protein contributes in virulence of Brucella; hence, it is a promising target for brucellosis vaccine. In this study, Mannosylated Chitosan Nanoparticles (MCN) loaded with FliC protein were synthesized as a targeted vaccine delivery system. The immunogenicity and protective efficacy of FliC and FliC-MCN against Brucella infection were evaluated in BALB/c mice. After cloning, expression and purification, FliC protein was loaded on MCN. The particle size, loading efficiency and in vitro release of the NPs were determined. Our investigation revealed that FliC and FliC-MCN could significantly increase specific IgG response (higher IgG2a titers). Besides, spleen cells from immunized mice produced high level of IFN-γ and IL-2 and low level IL-10 cytokines. Immunization with FliC and FliC-MCN conferred significant degree of protection against B. melitensis 16 M and B. abortus 544 infections. Overall these results indicate that FliC protein would be a novel potential antigen candidate for the development of a subunit vaccine against B. melitensis and B. abortus. Moreover, MCN could be used as an adjuvant and targeted vaccine delivery system.

Targeting resident memory T cell immunity culminates in pulmonary and systemic protection against Brucella infection

Brucellosis remains the most common zoonotic disease globally. Currently no vaccines for humans exist, and conventional brucellosis vaccines for livestock fail to confer complete protection; hence, an improved vaccine is needed. Although Brucella infections primarily occur following a mucosal exposure, vaccines are administered parenterally. Few studies have considered mucosal vaccinations, or even targeting of tissue-resident memory T (T_RM) cells. T_RM cells protect against viral infections, but less is known of their role in bacterial infections, and even less for brucellosis. Oral prime, nasal boost with a newly developed Brucella abortus double mutant (znBAZ) confers nearly complete protection against pulmonary challenge with wild-type (wt) B. abortus 2308, and its protective efficacy is >2800-fold better than the RB51 vaccine. Vaccination with znBAZ potently stimulated CD8⁺ T cells, whereas mucosal vaccination with RB51 induced mostly CD4⁺ T cells. Subsequent analysis revealed these pulmonary CD44⁺ CD69⁺ CD8⁺ T cells to be either CD103⁺ or CD103^- T_RM cells, and these sequestered to the lung parenchyma as CXCR3^lo and to the airways as CXCR3^hi. Both CD8⁺ T_RM subsets contained single-positive IFN-γ and TNF-α, as well as, polyfunctional cells. IL-17-producing CD8⁺ T_RM cells were also induced by znBAZ vaccination, but in vivo IL-17 neutralization had no impact upon protection. In vivo depletion of CD4⁺ T cells had no impact upon protection in znBAZ-vaccinated mice. In contrast, CD4⁺ T cell depletion reduced RB51’s protective efficacy in spleens and lungs by two- and three-logs, respectively. Although anti-CD8 mAb-treated znBAZ-vaccinated mice showed a significantly reduced pulmonary efficacy, this treatment failed to completely deplete the lung CD8⁺ T cells, leaving the CD103⁺ and CD103^- CD8⁺ T_RM cell ratios intact. Only znBAZ-vaccinated CD8^-/- mice were fully sensitive to pulmonary challenge with virulent wt B. abortus 2308 since CD8⁺ T_RM cells could not be induced. Collectively, these data demonstrate the key role of mucosal vaccination for the generation of CD8⁺ T_RM cells in protecting against pulmonary challenge with virulent B. abortus.

Brucellosis is the most common zoonotic disease worldwide and is transmitted via the consumption of unpasteurized dairy products or exposure to Brucella-laden aerosols. In fact, mucosal exposure is the most common route of infection for humans and animals, yet parenteral vaccination of livestock remains the preferred route of immunization. To determine whether development of a mucosal vaccination regimen could effectively generate immunity against pulmonary challenge with virulent B. abortus, a double-mutant B. abortus vaccine was administered mucosally, and found to induce CD8⁺ T_RM cells. These conferred complete protection against pulmonary infection and prevented systemic brucellae spread even in the absence of immune recirculating CD8⁺ T cells. These data show that mucosal vaccination can stimulate the induction of T_RM cells, which should be considered as a more effective means to protect against brucellosis. Furthermore, brucellosis needs to be considered a mucosal pathogen to warrant development of approaches different from conventional methods to protect humans and livestock against this disease.

In vivo immunogenicity assessment and vaccine efficacy evaluation of a chimeric tandem repeat of epitopic region of OMP31 antigen fused to interleukin 2 (IL-2) against Brucella melitensis in BALB/c mice

Background

Designing a potent recombinant vaccine, using the appropriate subunits with the greatest effect on stimulating the immune system, especially in the case of intracellular pathogens such as gram negative Brucella Melitensis bacteria, is of great importance. In this study, three repeats of 27 amino acids of the immunogenic epitope derived from OMP31 antigen (3E) from the Brucella melitensis, in a protective manner against Brucellosis have been used. To fortify the delivery system of recombinant antigens, IL-2 cytokine as a molecular adjuvant was fused to recombinant constructs. Recombinant proteins were evaluated for immunological studies in a mouse model (BALB/c).

Results

The results showed that all recombinant proteins could stimulate the immune system to produce Th1 cytokines and antibodies in compare to the negative control treatments. 3E-IL2 and then OMP31-IL2 proteins stimulated higher levels of IFN-γ and IL-2 compared to the other treatments (p < 0.05). Also, the results indicated that experimental treatments produced a higher level of IgG2a isotype than IgG1 isotype. In addition, the findings of the experiment showed that the presence of chemical adjuvant (IFA) along with molecular adjuvant can play a significant role in stimulating the immune system. After determining the potency of recombinant structures, their efficacy in stimulating the immune system were also evaluated. B. melitensis M16 strain was used to challenge 30 days after last immunization. The microbial load of the splenocyte in the treatments receiving chimeric proteins were significantly lower. Also, Wright serological test confirmed that these treatments had the lowest agglutination rate, as well as the positive treatment, while in the negative treatments in excess of blood serum dilutions, agglutination rate were more than 2 + .

Conclusions

3E-IL2 treatment showed the best performance compared to other recombinant proteins and could be considered as the suitable candidate for further research on the production of recombinant vaccine against Brucella.

Evaluation of in ovo vaccination of DNA vaccines for Campylobacter control in broiler chickens

Campylobacter is the leading bacterial cause of human enteritis in developed countries. Chicken is a major natural host of Campylobacter. Thus, on-farm control of Campylobacter load in poultry would reduce the risk of human exposure to this pathogen. Vaccination is an attractive intervention measure to mitigate Campylobacter in poultry. Our previous studies have demonstrated that Campylobacter outer membrane proteins CmeC (a component of multidrug efflux pump) and CfrA (ferric enterobactin receptor) are feasible and promising candidates for vaccine development. In this study, by targeting these two attractive vaccine candidates, we explored and evaluated a new vaccination strategy, which combines the in ovo vaccination route and novel DNA vaccine formulation, for Campylobacter control in broilers. We observed that direct cloning of cfrA or cmeC gene into the eukaryotic expression vector pCAGGS did not lead to sufficient level of production of the target proteins in the eukaryotic HEK-293 cell line. However, introduction of the Kozak consensus sequence (ACCATGG) in the cloned bacterial genes greatly enhanced production of inserted gene in eukaryotic cells, creating desired DNA vaccines. Subsequently, the validated DNA vaccines were prepared and used for two independent in ovo vaccination trials to evaluate their immune response and protective efficacy. However, single in ovo injection of specific DNA vaccine at 18th day of embryonation, regardless using neutral lipid-protected vector or not, failed to trigger significant IgG and IgA immune responses and did not confer protection against C. jejuni colonization in the intestine of chickens. In conclusion, this study demonstrates that the Kozak sequence is critically important for construction of the DNA vaccine expressing prokaryotic gene. The optimal regimen for in ovo vaccination of DNA vaccine for Campylobacter control in poultry needs to be determined in future studies.

Identification of Cross-Protective Potential Antigens against Pathogenic Brucella spp. through Combining Pan-Genome Analysis with Reverse Vaccinology

Brucellosis is a zoonotic infectious disease caused by bacteria of the genus Brucella. Brucella melitensis, Brucella abortus, and Brucella suis are the most pathogenic species of this genus causing the majority of human and domestic animal brucellosis. There is a need to develop a safe and potent subunit vaccine to overcome the serious drawbacks of the live attenuated Brucella vaccines. The aim of this work was to discover antigen candidates conserved among the three pathogenic species. In this study, we employed a reverse vaccinology strategy to compute the core proteome of 90 completed genomes: 55 B. melitensis, 17 B. abortus, and 18 B. suis. The core proteome was analyzed by a metasubcellular localization prediction pipeline to identify surface-associated proteins. The identified proteins were thoroughly analyzed using various in silico tools to obtain the most potential protective antigens. The number of core proteins obtained from analyzing the 90 proteomes was 1939 proteins. The surface-associated proteins were 177. The number of potential antigens was 87; those with adhesion score ≥ 0.5 were considered antigen with "high potential," while those with a score of 0.4-0.5 were considered antigens with "intermediate potential." According to a cumulative score derived from protein antigenicity, density of MHC-I and MHC-II epitopes, MHC allele coverage, and B-cell epitope density scores, a final list of 34 potential antigens was obtained. Remarkably, most of the 34 proteins are associated with bacterial adhesion, invasion, evasion, and adaptation to the hostile intracellular environment of macrophages which is adjusted to deprive Brucella of required nutrients. Our results provide a manageable list of potential protective antigens for developing a potent vaccine against brucellosis. Moreover, our elaborated analysis can provide further insights into novel Brucella virulence factors. Our next step is to test some of these antigens using an appropriate antigen delivery system.

Comparison of the protective immunity elicited by a Brucella cocktail protein vaccine (rL7/L12+rTOmp31+rSOmp2b) in two different adjuvant formulations in BALB/c mice

In the present study, protective efficacy conferred by a cocktail protein consisted of Brucella L7/L12 ribosomal, truncated outer membrane protein 31 (TOmp31) and SOmp2b recombinant proteins in CpG ODN 1826+ Montanide ISA 70VG or Poly (I:C) adjuvants was evaluated and compared in BALB/c mice. Immunization of mice with both vaccine regimens elicited strong specific IgG responses (higher IgG2a titers over IgG1 titers), provided T helper1 (Th1) oriented immune responses and conferred protection levels compatible to the live vaccines against Brucella challenge. Vaccination of BALB/c mice with the cocktail protein in CpG ODN 1826+ Montanide ISA 70 V G adjuvants induced higher levels of antibody, IFN-γ/IL-2 and conferred more protection levels against B. melitenisis and B. abortus challenge than did the cocktail protein in Poly (I:C) formulation. In conclusion, both vaccine regimens are capable of stimulating specific Th1- biased immune responses and conferring cross protection against B. melitensis and B. abortus infections. Therefore, they could be introduced as new potential candidates for the development of subunit vaccines against Brucella infection.

Evaluation of DNA vaccine encoding BCSP31 surface protein of Brucella abortus for protective immunity

Brucellosis is a highly contagious and zoonotic disease and has a considerable impact on animal health and economy of a country, principally in Pakistan, where rural income largely depends upon livestock farming and dairy products. The disease burden is more in underdeveloped/developing countries due to the low economy and limited access to the diagnostic facilities. In Pakistan, the prevalence of Brucella abortus is very high, so it is the need of the hour to control this disease through more advanced methods. This study was designed with the aim to construct the DNA based vaccine of gene encoding antigenic surface protein (BCSP₃₁). For this purpose, the BCSP₃₁ gene was amplified, purified and ligated in pTZ57 R/T (cloning vector). Dubbed BCSP₃₁-pTZ57 R/T vector was transformed into competent cells (DH5α). After plasmid extraction, the plasmid and pET-28a vector was restricted with EcoRI and BamHI. Again, ligation was done and dubbed pET-28a-BCSP₃₁ transformed into E. coli (BL21). After expression, the protein was purified and used for evaluation of immunogenic response. The protective and immunogenic efficacy of the vaccine was evaluated in rabbits (n = 20). The rabbits were divided into four equal groups. Groups A-C were given purified protein diluted in normal saline @ 750, 1500 and 3000 μg/0.2 mL, respectively through intraconjunctival route. Group D was given 0.2 mL normal saline through intraconjunctival route. Specific immunoglobulin G (IgG) responses were measured through indirect ELISA on a weekly basis. The titer of IgG against the antigen was significantly (p < 0.05) higher in vaccinated groups A-C as compared to group D (control group) in a dose dependent manner. Moreover, log units of protection produced by DNA based vaccine in the rabbits (3.02) also indicated the protective efficacy of the DNA vaccine against B. abortus challenge. The response of this vaccine in rabbit suggested its potential effectiveness against Brucella abortus in large animals.

Protective and therapeutic efficacy study of divalent fusion protein rL7/L12-Omp25 against B. abortus 544 in presence of IFNγ

Brucella as intracellular pathogen requires a coordinate interaction between Th1 subset of gamma interferon-secreting CD4 T cells and CD8 T cells for optimal protective immunity. It was previously recognized that L7/L12 as T cell-reactive antigen from the pathogen. On other hand, Omp25 was found as another antigen to provide protection against the Brucella infection by eliciting both Th1 and Th2 type of immune responses in mice. Here, we analyzed the prophylactic and therapeutic efficacy of a divalent fusion protein (rL7/L12-Omp25) comprising these two promising immunogens of Brucella in the presence of murine IFN-gamma in mice against B. abortus 544 challenge. rIFN-gamma with rL7/L12-Omp25 resulted in superior immune response when compared to the animal vaccine strain B. abortus S19. The vaccine candidate caused dominance of IgG1 over IgG2a and upregulated cytokine secretion (IFN-gamma, TNF-α, and IL-10) among immunized mice. Moreover, the antigen in combination with murine IFN-gamma elicited stronger cell-mediated immune response among the immunized animals when compared to standard vaccine (S19). The registered log protection unit among challenged mice with B. abortus 544 pathogen was 2.16, p = 0.0001 when rL7/L12-Omp25 was administered alone and 2.4, p = 0.0001 when it was administered along with rIFN-gamma. However, the molecule upon administration with murine IFN-gamma imparted very minimal or no therapeutic effect against brucellosis. To conclude, our study demonstrates the potential of rL7/L12-Omp25 as an immunogen of prospective and efficient prophylaxis as it is capable of eliciting both cell-mediated and humoral immune responses against brucellosis.

Evaluation of immune responses induced by polymeric OMP25-BLS Brucella antigen

Brucellosis is one the serious infectious diseases caused deleterious health and economic losses. Vaccination with subunit vaccines is the efficient alternative way than live attenuated vaccines against infectious diseases. Herein a new chimeric OMP25-BLS antigen emulsified in Chitosan Nanoparticles was designed and its immune responses were compared with control groups. Also, the role of heat shock protein 60 kDa in combination with OMP25-BLS antigen was assessed. Structural and antigenic features of chimeric antigen were predicted using bioinformatics tools. Moreover, the humoral and cellular immune responses were measured by ELISA in seven different groups. Observations showed rOMP25-BLS structure was highly stable and antigenic. Cytokines analysis showed rOMP25 and rOMP25-BLS + rHSP60 induced higher titer of INF-γ than rHSP60 and rOMP25-BLS. There was no statistically significant difference between positive control group and rOMP25-BLS + rHSP60 in inducing TNF-α (p < .05). Additionally, the highest titer of IL-4 was dedicated to rOMP25 among other immunized treatments, while there were no significant differences between positive control group and other immunized groups with recombinant proteins (p < .05). In addition, rOMP25-BLS and rHSP60 induced higher titer of total antibody compared to other groups. Also, rHSP60 could improve IgG2a to IgG1 ratio when it used in combination with chimeric antigen. Moreover, the lymphocyte proliferation index was higher in chimeric rOMP25-BLS + HSP60 antigen. In conclusion, while rOMP25-BLS chimeric antigen unable to induce efficient cellular response than individual injection of rOMP25, its injection in combination with rHSP60 could improve cellular immunity.

Oral immunization of mice with Omp31-loaded N-trimethyl chitosan nanoparticles induces high protection against Brucella melitensis infection

Brucellosis is a group of closely associated zoonotic bacterial illnesses caused by members of the genus Brucella. B. melitensis Omp31 is a promising candidate for a subunit vaccine against brucellosis. This study surveyed the immunogenicity of Omp31 alone and with incomplete Freund’s adjuvant (Omp31-IFA) and N-trimethyl chitosan (TMC/Omp31) nanoparticles (NPs), as well as the effect of Omp31 immunization route on immunological responses and protection. After expression and purification, the recombinant Omp31 (rOmp31) was loaded onto TMC NPs by ionic gelation. The particle size, loading efficiency and in vitro release of the NPs were examined. Omp31-IFA was administered intraperitoneally, while TMC/Omp31 NPs were administered orally and intraperitoneally. According to the antibody subclasses and cytokine profile, intraperitoneal immunization by Omp31-IFA and TMC/Omp31 NPs induced T helper 1 (Th1) and Th1–Th2 immune responses, respectively. On the other hand, oral immunization with TMC/Omp31 NPs elicited a mixed Th1–Th17 immune response. Data obtained from the cell proliferation assay showed that vaccination with Omp31 stimulated a vigorous antigen-specific cell proliferative response, which could be further increased after oral immunization with TMC/Omp31 NPs. Vaccinated groups of mice when challenged with B. melitensis 16M were found to be significantly protected in the orally administered group in comparison with the intraperitoneally immunized mice. Results of this study indicated that the reason for high protection after oral vaccination can be via elicited Th17 response.

Impact of heat shock protein 60KD in combination with outer membrane proteins on immune response against Brucella melitensis

Brucellosis caused by the bacterium Brucella affects various domestic and wild species. The outer membrane proteins 25 and 31 play key roles on stimulation of cell-mediated immune response against Brucella. GroEL as one of the major Brucella antigens stimulates the immune system and increases intracellular survival of bacteria. In the present study, we assumed injection of GroEL in combination with OMP25 and OMP31 would offer higher immunity levels. So, the impact of GroEL with different concentrations of recombinant outer membrane proteins emulsified in Chitosan Nanoparticles on immune responses was evaluated in mice model. Results showed both univalent (except rGroEL) and divalent immunized groups induced higher IFN-γ, TNF-α, and IL-4 titers in comparison to negative control groups. While GroEL showed negative effect on TNF-α titer, there were positive increase trends in IFN-γ in some treatments. Analysis of humoral antibody response revealed both univalent and divalent immunized groups induced higher IgG2a titer than IgG1 titer, indicating strong bent of Th1 immune response. Also, results showed GroEL can have positive impact on lymphocyte proliferation response. Overall, mice immunization using individual OMP25 or OMP31 demonstrated more effective cell-mediated immunity, although some combinations of rGroEL and rOMP31 vaccines were more efficient than other divalent ones.

Identification of potential antigens from non-classically secreted proteins and designing novel multitope peptide vaccine candidate against Brucella melitensis through reverse vaccinology and immunoinformatics approach

Brucella melitensis is an intracellular pathogen resides in the professional and non-professional phagocytes of the host, causing zoonotic disease brucellosis. The stealthy nature of the Brucella makes it's highly pathogenic, and it is hard to eliminate the bacteria completely from the infected host. Hitherto, no licensed vaccines are available for human brucellosis. In this study, we identified potential antigens for vaccine development from non-classically secreted proteins through reverse vaccinology approach. Based on the systemic screening of non-classically secreted proteins of B. melitensis 16M, we identified nine proteins as potential vaccine candidates. Among these, Omp31 and Omp22 are known immunogens, and its role in the virulence of Brucella is known. Roles of other proteins in the pathogenesis are yet to be studied. From the nine proteins, we identified six novel antigenic epitopes that can elicit both B-cell and T-cell immune responses. Among the nine proteins, the epitopes were predicted from Omp31 immunogenic protein precursor, Omp22 protein precursor, extracellular serine protease, hypothetical membrane-associated protein, iron-regulated outer membrane protein FrpB. Further, we designed a multitope vaccine using Omp31 immunogenic protein precursor, Omp22 protein precursor, extra cellular serine protease, iron-regulated outer membrane protein FrpB, hypothetical membrane-associated protein, and LPS-assembly protein LptD and polysaccharide export protein identified in the previous study. Epitopes were joined using amino acid linkers such as EAAAK and GPGPG. Cholera toxin subunit B, the nontoxic part of cholera toxin, was used as an adjuvant and it was linked to the N-terminal of the multitope vaccine candidate. The designed vaccine candidate was modeled, validated and the physicochemical properties were analyzed. Results revealed that the vaccine candidate is soluble, stable, non-allergenic, antigenic and 87% of residues of the designed vaccine candidate is located in the favored region. In conclusion, the computational analysis showed that the newly designed multitope protein could be used to develop a promising vaccine for human brucellosis.

Development and trial of vaccines against Brucella

The search for ideal brucellosis vaccines remains active today. Currently, no licensed human or canine anti-brucellosis vaccines are available. In bovines, the most successful vaccine (S19) is only used in calves, as adult vaccination results in orchitis in male, prolonged infection, and possible abortion complications in pregnant female cattle. Another widely deployed vaccine (RB51) has a low protective efficacy. An ideal vaccine should exhibit a safe profile as well as enhance protective efficacy. However, currently available vaccines exhibit one or more major drawbacks. Smooth live attenuated vaccines suffer shortcomings such as residual virulence and serodiagnostic interference. Inactivated vaccines, in general, confer relatively low levels of protection. Recent developments to improve brucellosis vaccines include generation of knockout mutants by targeting genes involved in metabolism, virulence, and the lipopolysaccharide synthesis pathway, as well as generation of DNA vaccines, mucosal vaccines, and live vectored vaccines, have all produced varying degrees of success. Herein, we briefly review the bacteriology, pathogenesis, immunological implications, candidate vaccines, vaccinations, and models related to Brucella.

Characterization of novel Omp31 antigenic epitopes of Brucella melitensis by monoclonal antibodies

BACKGROUND

Brucellosis is a severe zoonotic disease worldwide. Detection and identification of Brucella species are essential to prevent or treat brucellosis in humans and animals. The outer membrane protein-31 (Omp31) is a major protein of Brucellae except for B. abortus, while the Omp31 antigenic epitopes have not been extensively characterized yet.

RESULTS

A total of 22 monoclonal antibodies (mAbs) were produced against Omp31 of Brucella (B.) melitensis, of which 13 recognized five linear epitopes, 7 reacted with semi-conformational epitopes and 2 reacted with conformational epitopes, respectively. The mAb isotypes were 11 (50%) IgG2a, 5 (23%) IgG1 and 6 (27%) IgM. On the basis of epitope recognition and reactivity levels, 8 mAbs including 3 IgM and 5 IgG clones were considered as highly reactive and potentially diagnostic antibodies. Among these mAbs, 7A3 (IgG1), 5B1 (IgG2a), 2C1 (IgG2a) and 5B3 (IgG2a) reacted with differently conserved linear epitopes of B. melitensis, B. ovis, B. suis and B. canis strains, while 5H3 (IgG2a) highly reacted with a conformational epitope of Omp31 when tested with several immunoassays.

CONCLUSIONS

These potent monoclonal antibodies can be used for identifying Omp31 antigens or detecting B. melitensis and other Brucella species beyond B. abortus in vitro or in vivo.

Meta-Analysis and Advancement of Brucellosis Vaccinology

Background/Objectives

In spite of all the research effort for developing new vaccines against brucellosis, it remains unclear whether these new vaccine technologies will in fact become widely used. The goal of this study was to perform a meta-analysis to identify parameters that influence vaccine efficacy as well as a descriptive analysis on how the field of Brucella vaccinology is advancing concerning type of vaccine, improvement of protection on animal models over time, and factors that may affect protection in the mouse model.

Methods

A total of 117 publications that met the criteria were selected for inclusion in this study, with a total of 782 individual experiments analyzed.

Results

Attenuated (n = 221), inactivated (n = 66) and mutant (n = 102) vaccines provided median protection index above 2, whereas subunit (n = 287), DNA (n = 68), and vectored (n = 38) vaccines provided protection indexes lower than 2. When all categories of experimental vaccines are analyzed together, the trend line clearly demonstrates that there was no improvement of the protection indexes over the past 30 years, with a low negative and non significant linear coefficient. A meta-regression model was developed including all vaccine categories (attenuated, DNA, inactivated, mutant, subunit, and vectored) considering the protection index as a dependent variable and the other parameters (mouse strain, route of vaccination, number of vaccinations, use of adjuvant, challenge Brucella species) as independent variables. Some of these variables influenced the expected protection index of experimental vaccines against Brucella spp. in the mouse model.

Conclusion

In spite of the large number of publication over the past 30 years, our results indicate that there is not clear trend to improve the protective potential of these experimental vaccines.

MicroRNA Expression Patterns of CD8+ T Cells in Acute and Chronic Brucellosis

Although our knowledge about Brucella virulence factors and the host response increase rapidly, the mechanisms of immune evasion by the pathogen and causes of chronic disease are still unknown. Here, we aimed to investigate the immunological factors which belong to CD8+ T cells and their roles in the transition of brucellosis from acute to chronic infection. Using miRNA microarray, more than 2000 miRNAs were screened in CD8+ T cells of patients with acute or chronic brucellosis and healthy controls that were sorted from peripheral blood with flow cytometry and validated through qRT-PCR. Findings were evaluated using GeneSpring GX (Agilent) 13.0 software and KEGG pathway analysis. Expression of two miRNAs were determined to display a significant fold change in chronic group when compared with acute or control groups. Both miRNAs (miR-126-5p and miR-4753-3p) were decreased (p <0.05 or fold change > 2). These miRNAs have the potential to be the regulators of CD8+ T cell-related marker genes for chronic brucellosis infections. The differentially expressed miRNAs and their predicted target genes are involved in MAPK signaling pathway, cytokine-cytokine receptor interactions, endocytosis, regulation of actin cytoskeleton, and focal adhesion indicating their potential roles in chronic brucellosis and its progression. It is the first study of miRNA expression analysis of human CD8+ T cells to clarify the mechanism of inveteracy in brucellosis.

Nasal vaccination stimulates CD8(+) T cells for potent protection against mucosal Brucella melitensis challenge

Brucellosis remains a significant zoonotic threat worldwide. Humans and animals acquire infection via their oropharynx and upper respiratory tract following oral or aerosol exposure. After mucosal infection, brucellosis develops into a systemic disease. Mucosal vaccination could offer a viable alternative to conventional injection practices to deter disease. Using a nasal vaccination approach, the ΔznuA B. melitensis was found to confer potent protection against pulmonary Brucella challenge, and reduce colonization of spleens and lungs by more than 2500-fold, with more than 50% of vaccinated mice showing no detectable brucellae. Furthermore, tenfold more brucellae-specific, IFN-γ-producing CD8⁺ T cells than CD4⁺ T cells were induced in the spleen and respiratory lymph nodes. Evaluation of pulmonary and splenic CD8⁺ T cells from mice vaccinated with ΔznuA B. melitensis revealed that these expressed an activated effector memory (CD44^hiCD62L^loCCR7^lo) T cells producing elevated levels of IFN-γ, TNF-α, perforin, and granzyme B. To assess the relative importance of these increased numbers of CD8⁺ T cells, CD8^−/− mice were challenged with virulent B. melitensis, and they showed markedly increased bacterial loads in organs in contrast to similarly challenged CD4^−/− mice. Only ΔznuA B. melitensis- and Rev-1-vaccinated CD4^−/− and wild-type mice, not CD8^−/− mice, were completely protected against Brucella challenge. Determination of cytokines responsible for conferring protection showed the relative importance of IFN-γ, but not IL-17. Unlike wild-type mice, IL-17 was greatly induced in IFN-γ^−/− mice, but IL-17 could not substitute for IFN-γ’s protection, although an increase in brucellae dissemination was observed upon in vivo IL-17 neutralization. These results show that nasal ΔznuA B. melitensis vaccination represents an attractive means to stimulate systemic and mucosal immune protection via CD8⁺ T cell engagement.

Immunogenic response to a recombinant pseudorabies virus carrying bp26 gene of Brucella melitensis in mice

Brucellae are facultative intracellular bacterial pathogens of a zoonotic disease called brucellosis. Live attenuated vaccines are utilized for prophylaxis of brucellosis; however, they retain residual virulence to human and/or animals, as well as interfere with diagnosis. In this study, recombinant virus PRV ΔTK/ΔgE/bp26 was screened and purified. One-step growth curve assay showed that the titer of recombinant virus was comparable to the parent strain. Mice experiments showed the recombinant virus elicited high titer of humoral antibodies against Brucella detected by enzyme-linked immunosorbent assay and against PRV by serum neutralization test. The recombinant virus induced high level of Brucella-specific lymphocyte proliferation response and production of interferon gamma. Collectively, these data suggest that the bivalent virus was capable of inducing both humoral and cellular immunity, and had the potential to be a vaccine candidate to prevent Brucella and/or pseudorabies virus infections.

Immunization with Brucella VirB proteins reduces organ colonization in mice through a Th1-type immune response and elicits a similar immune response in dogs

VirB proteins from Brucella spp. constitute the type IV secretion system, a key virulence factor mediating the intracellular survival of these bacteria. Here, we assessed whether a Th1-type immune response against VirB proteins may protect mice from Brucella infection and whether this response can be induced in the dog, a natural host for Brucella. Splenocytes from mice immunized with VirB7 or VirB9 responded to their respective antigens with significant and specific production of gamma interferon (IFN-γ), whereas interleukin-4 (IL-4) was not detected. Thirty days after an intraperitoneal challenge with live Brucella abortus, the spleen load of bacteria was almost 1 log lower in mice immunized with VirB proteins than in unvaccinated animals. As colonization reduction seemed to correlate with a Th1-type immune response against VirB proteins, we decided to assess whether such a response could be elicited in the dog. Peripheral blood mononuclear cells (PBMCs) from dogs immunized with VirB proteins (three subcutaneous doses in QuilA adjuvant) produced significantly higher levels of IFN-γ than cells from control animals upon in vitro stimulation with VirB proteins. A skin test to assess specific delayed-type hypersensitivity was positive in 4 out of 5 dogs immunized with either VirB7 or VirB9. As both proteins are predicted to locate in the outer membrane of Brucella organisms, the ability of anti-VirB antibodies to mediate complement-dependent bacteriolysis of B. canis was assessed in vitro. Sera from dogs immunized with either VirB7 or VirB9, but not from those receiving phosphate-buffered saline (PBS), produced significant bacteriolysis. These results suggest that VirB-specific responses that reduce organ colonization by Brucella in mice can be also elicited in dogs.

Evaluation of the efficacy of outer membrane protein 31 vaccine formulations for protection against Brucella canis in BALB/c mice

Canine brucellosis is an infectious disease caused by the Gram-negative bacterium Brucella canis. Unlike conventional control programs for other species of the genus Brucella, currently there is no vaccine available against canine brucellosis, and preventive measures are simply diagnosis and isolation of infected dogs. New approaches are therefore needed to develop an effective and safe immunization strategy against this zoonotic pathogen. In this study, BALB/c mice were subcutaneously immunized with the following: (i) the recombinant Brucella Omp31 antigen formulated in different adjuvants (incomplete Freund adjuvant, aluminum hydroxide, Quil A, and Montanide IMS 3012 VGPR), (ii) plasmid pCIOmp31, or (iii) pCIOmp31 plasmid followed by boosting with recombinant Omp31 (rOmp31). The immune response and the protective efficacy against B. canis infection were characterized. The different strategies induced a strong immunoglobulin G (IgG) response. Furthermore, spleen cells from rOmp31-immunized mice produced gamma interferon and interleukin-4 (IL-4) after in vitro stimulation with rOmp31, indicating the induction of a mixed Th1-Th2 response. Recombinant Omp31 administered with different adjuvants as well as the prime-boost strategy conferred protection against B. canis. In conclusion, our results suggest that Omp31 could be a useful candidate for the development of a subcellular vaccine against B. canis infection.

Evaluation in mice of Brucella ovis attenuated mutants for use as live vaccines against B. ovis infection

Brucella ovis causes ram contagious epididymitis, a disease for which a specific vaccine is lacking. Attenuated Brucella melitensis Rev 1, used as vaccine against ovine and caprine brucellosis caused by B. melitensis, is also considered the best vaccine available for the prophylaxis of B. ovis infection, but its use for this purpose has serious drawbacks. In this work, two previously characterized B. ovis attenuated mutants (Δomp25d and Δomp22) were evaluated in mice, in comparison with B. melitensis Rev 1, as vaccines against B. ovis. Similarities, but also significant differences, were found regarding the immune response induced by the three vaccines. Mice vaccinated with the B. ovis mutants developed anti-B. ovis antibodies in serum of the IgG₁, IgG_2a and IgG_2b subclasses and their levels were higher than those observed in Rev 1-vaccinated mice. After an antigen stimulus with B. ovis cells, splenocytes obtained from all vaccinated mice secreted similar levels of TNF-α and IL12(p40) and remarkably high amounts of IFN-γ, a crucial cytokine in protective immunity against other Brucella species. By contrast, IL-1α -an enhancer of T cell responses to antigen- was present at higher levels in mice vaccinated with the B. ovis mutants, while IL-10, an anti-inflammatory cytokine, was significantly more abundant in Rev 1-vaccinated mice. Additionally, the B. ovis mutants showed appropriate persistence, limited splenomegaly and protective efficacy against B. ovis similar to that observed with B. melitensis Rev 1. These characteristics encourage their evaluation in the natural host as homologous vaccines for the specific prophylaxis of B. ovis infection.

Influenza viral vectors expressing the Brucella OMP16 or L7/L12 proteins as vaccines against B. abortus infection

BACKGROUND

We generated novel, effective candidate vaccine against Brucella abortus based on recombinant influenza viruses expressing the Brucella ribosomal protein L7/L12 or outer membrane protein (Omp)-16 from the NS1 open reading frame. The main purpose of this work was to evaluate the safety, immunogenicity and protectiveness of vaccine candidate in laboratory animals.

METHODS AND RESULTS

Four recombinant influenza A viral constructs of the subtypes Н5N1 or H1N1 expressing the Brucella proteins L7/L12 or Omp16 were obtained by a reverse genetics method: Flu-NS1-124-L7/L12-H5N1, Flu-NS1-124-Omp16-H5N1, Flu-NS1-124-L7/L12-H1N1 and Flu-NS1-124-Omp16-H1N1. Despite of substantial modification of NS1 gene, all constructs replicated well and were retain their Brucella inserts over five passages in embryonated chicken eggs (CE). Administration of the mono- or bivalent vaccine formulation via prime-boost intranasal (i.n.), conjunctival (c.) or subcutaneous (s.c.) immunization was safe in mice; no deaths, body weight loss or pathomorphological changes were observed over 56 days. Moreover, guinea pigs vaccinated i.n. with vaccine vectors did not shed the vaccine viruses through their upper respiratory tract after the prime and booster vaccination. These findings confirmed the replication-deficient phenotype of viral vectors. The highest antibody response to Brucella antigen was obtained with constructs expressing L7/L12 (ELISA, GMT 242.5-735.0); whereas the highest T-cell immune response- with construct expressing Omp16 (ELISPOT, 337 ± 52-651 ± 45 spots/4×105cells), which was comparable (P > 0.05) to the response induced by the commercial vaccine B. abortus 19. Interestingly, c. immunization appeared to be optimal for eliciting T-cell immune response. In guinea pigs, the highest protective efficacy after challenge with B. abortus 544 was achieved with Omp16 expressing constructs in both monovalent or bivalent vaccine formulations; protective efficacy was comparable to those induced by a commercial live B. abortus 19 vaccine.

CONCLUSION

Thus, influenza vectors expressing Brucella protective antigens can be developed as novel influenza vectored vaccine against B. abortus infection.

Novel influenza virus vectors expressing Brucella L7/L12 or Omp16 proteins in cattle induced a strong T-cell immune response, as well as high protectiveness against B. abortus infection

This paper presents the results of a study of the immunogenicity and protectiveness of new candidate vector vaccine against Brucella abortus - a bivalent vaccine formulation consisting of a mixture of recombinant influenza A subtype H5N1 or H1N1 (viral constructs vaccine formulation) viruses expressing Brucella ribosomal protein L7/L12 and Omp16, in cattle. To increase the effectiveness of the candidate vaccine, adjuvants such as Montanide Gel01 or chitosan were included in its composition. Immunization of cattle (heifers aged 1-1.5 years, 5 animals per group) with the viral constructs vaccine formulation only, or its combination with adjuvants Montanide Gel01 or chitosan, was conducted via the conjunctival method using cross prime (influenza virus subtype H5N1) and booster (influenza virus subtype H1N1) vaccination schedules at an interval of 28 days. Vaccine candidates were evaluated in comparison with the positive (B. abortus S19) and negative (PBS) controls. The viral constructs vaccine formulations, particularly in combination with Montanide Gel01 adjuvant promoted formation of IgG antibodies (with a predominance of antibodies of isotype IgG2a) against Brucella L7/L12 and Omp16 proteins in ELISA. Moreover, these vaccines in cattle induced a strong antigen-specific T-cell immune response, as indicated by a high number of CD4(+) and CD8(+) cells, as well as the concentration of IFN-γ, and most importantly provided a high level of protectiveness comparable to the commercial B. abortus S19 vaccine and superior to the B. abortus S19 vaccine in combination with Montanide Gel01 adjuvant. Based on these findings, we recommended the bivalent vaccine formulation containing the adjuvant Montanide Gel01 for practical use in cattle.

In silico analysis of chimeric TF, Omp31 and BP26 fragments of Brucella melitensis for development of a multi subunit vaccine candidate

OBJECTIVE(S)

Brucellosis, especially caused by Brucella melitensis, remains one of the most common zoonotic diseases worldwide with more than 500,000 human cases reported annually. The commonly used live attenuated vaccine in ovine brucellosis prophylaxis is B. melitensis Rev1. But due to different problems caused by the administration of this vaccine, a protective subunit vaccine against B. melitensis is strongly demanded. Brucella BP26, Omp31 and TF proteins have shown a considerable potential as protective antigens for brucellosis. Chimeric proteins carrying epitopes or adjuvant sequences increase the possibility of eliciting a broad cellular or humoral immune response. In silico tools are highly suited to study, design and evaluate vaccine strategies.

MATERIALS AND METHODS

In this study, a synthetic chimeric gene, encoding TF, BP26 (93-111) and Omp31(48-74) was designed. In order to predict the 3D structure of protein, modeling was carried out.

RESULTS

Validation results showed that 91.1% of residues lie in favored or additional allowed region of Ramachandran plot. The epitopes in the chimeric protein are likely to induce both the B-cell and T-cell mediated immune responses. Conclusion : The chimeric protein may be used as multi subunit for development of Brucella vaccine candidates.

Evaluation of humoral and cellular immune responses to BP26 and OMP31 epitopes in the attenuated Brucella melitensis vaccinated sheep

In recent years, the number of cases of human brucellosis has been increasing by approximately 10% per year in China. Most cases were caused by Brucella melitensis through contacts with infected sheep, goats or their products. An attenuated B. melitensis vaccine M5-90 is currently used to vaccinate both animals in China. This vaccine has not been investigated for critical parameters such as immune response and its association with protective efficacy. In this study, humoral and cellular immune response to the periplasmic protein BP26 and the outer membrane protein OMP31 were evaluated in M5-90 vaccinated Chinese merino and Kazak sheep. Antibodies to BP26 or OMP31 were detected at low levels, and specific IFN-γ response was quantified. Strongly reactive peptides derived from BP26 and OMP31 identified five T-cell epitopes (BP26-6, -8, -11, -12 and OMP31-23) common to both sheep species, five species-specific epitopes (BP26-10, -18, -21 and -22 and OMP31-12) and four animal-specific epitopes (BP26-15, -23, OMP31-6 and -21), which stimulated specific IFN-γ response in vaccinated sheep. Among those T-cell epitopes, reactivity to BP26-18 and -21 epitopes was significantly associated with MHC-I B allele (P=0.024). However, a specific T-cell response induced by the M5-90 vaccine was relatively week and did not sustain long enough, which might be suppressed by rapid activation of T-regulatory (Treg) cells following vaccination. These findings provide an insight in designing a safer and more effective vaccine for use in animals and in humans.

Protective effect of a DNA vaccine containing an open reading frame with homology to an ABC-type transporter present in the genomic island 3 of Brucella abortus in BALB/c mice

The immunogenicity of a DNA vaccine containing an open reading frame (ORF) of genomic island 3 (GI-3), specific for Brucella abortus and Brucella melitensis, has been examined. Intramuscular injection of plasmid DNA carrying the open reading frame with homology to an ABC-type transporter (pV278a) into BALB/c mice elicited both humoral and cellular immune responses. Mice injected with pV278a had a dominant immunoglobulin G2a (IgG2a) response. This DNA vaccine elicited a T-cell-proliferative response and induced significant levels of interferon gamma (INF-γ) upon restimulation with recombinant 278a protein. Upon stimulation with an appropriate recombinant protein or crude Brucella protein, the vaccine did not induce IL-4, suggesting a typical T-helper (TH1) response. Furthermore, the vaccine induced protection in BALB/c mice when challenged with the virulent strain Brucella abortus 2308. Taken together, these data suggest that DNA vaccination offers an improved delivery of the homologous of an ABC-type transporter antigen, and provides the first evidence of a protective effect of this antigen in the construction of vaccines against B. abortus.