Immune response and serum bactericidal activity against Brucella ovis elicited using a short immunization schedule with the polymeric antigen BLSOmp31 in rams

Evaluation of the efficacy of polymeric antigen BLSOmp31 formulated in a new cage-like particle adjuvant (ISPA) administered by parenteral or mucosal routes against Brucella ovis in BALB/c mice

Brucella ovis is an economically important cause of epididymitis in rams worldwide. Polymeric BLSOmp31 was previously identified as a protective immunogen against this pathogen. In this study, BLSOmp31 was formulated with a modified version of ISCOMATRIX adjuvant called ISPA (BLSOmp31/ISPA) and was administered in BALB/C by the subcutaneous and ocular route. The systemic and mucosal immune responses, the opsonic activity of antibodies and the protection conferred against B. ovis were evaluated. BLSOmp31+ISPA injected subcutaneously or by ocular route induced significantly higher IgG antibody levels with a mixed Th1/Th2 profile compared to non-immunized mice. IgA and IgG were detected in sera and nasal, tracheobronchial, vaginal secretions, tears and faeces, from SC immunized mice while in the group immunized by the ocular route a slight increase in both isotypes was mainly observed in all secretions, except in vaginal fluid. Opsonic antibodies stimulated binding and increased uptake of PHrodo™ Green-labelled B. ovis by neutrophils and monocytes. BLSOmp31 administered subcutaneously induced the highest levels of IFN-ɣ. The ocular immunization not only produced significant levels of this cytokine but also IL-4 compared to non-immunized mice. Both, subcutaneous and ocular routes of immunization, significantly protected against B. ovis infection. These results indicate that BLSOmp31/ISPA administered parenterally or by ocular route is a safe and effective vaccine against B. ovis in the murine model.

Natural Brucella melitensis Infection and Rev. 1 Vaccination Induce Specific Brucella O-Polysaccharide Antibodies Involved in Complement Mediated Brucella Cell Killing

Vaccination against brucellosis using live attenuated strains is the primary approach in protecting livestock against the disease through a strong cellular immune response. Attenuated vaccine strains also induce serum anti-Brucella antibodies, mostly against Brucella O-polysaccharide, but their role in protection against the disease remains unclear. In this study, we show that Brucella OPS serum antibodies after vaccination or natural infection could kill Brucella in vitro as shown by the serum bactericidal activity (SBA) assay. We used serum samples of Rev. 1 vaccinated sheep that were negative or positive for Brucella OPS antibodies by either one of complement fixation test (CFT), microplate agglutination test (MAT) and ELISA, or sera of naturally infected sheep positive by CFT. We found a significant increase in the killing ability of sera 30 days after intraocular vaccination with Rev. 1 as compared with pre-vaccination. SBA was significantly higher in sera containing Brucella OPS IgG antibodies in comparison with sera lacking such antibodies (p < 0.001 against 16M & Rev. 1 strains). All 10 sera of convalescent sheep demonstrated significant killing ability against the 16M B. melitensis field strain. Specific OPS antibodies participate in the in vitro complement mediated Brucella killing suggesting a potential role in protection against the disease through this mechanism and relevance of developing OPS-based Brucella vaccines.

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.

Polymeric antigen BLSOmp31 formulated with class B CpG-ODN in a nanostructure (BLSOmp31/CpG-ODN/Coa-ASC16) administered by parenteral or mucosal routes confers protection against Brucella ovis in Balb/c mice

Previously, we demonstrated that the chimera BLSOmp31 formulated in chitosan microspheres or Poloxamer407-Chitosan administered via the nasal and the ocular mucosa conferred partial protection in sheep against B. ovis. In this work, we tested a new delivery system for mucosal immunization with BLSOmp31 in the murine model to improve the efficacy of previously used formulations. First, we evaluated the protective efficacy against B. ovis induced by BLSOmp31 administered by the subcutaneous route using either BLSOmp31 alone, co-administered with immunostimulatory synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG-ODN) or with CpG-ODN in a nanostructure called Coa-ASC16 compared with BLSOmp31 emulsified in Incomplete Freund Adjuvant. Then, we evaluated the protection conferred by the best performing formulation (BLSOmp31/CpG-ODN/Coa-ASC16) administered by both subcutaneous and ocular routes. BLSOmp31/CpG-ODN/Coa-ASC16 injected subcutaneously did not induce higher IgG antibody levels compared to BLSOmp31 alone or BLSOmp31/CpG-ODN but it did stimulate a mixed immune Th1-Th2 response with the highest levels of IFN-ɣ and conferred significant protection against the B. ovis challenge. Although ocular instillation of BLSOmp31/CpG-ODN/Coa-ASC16 showed a similar degree of protection compared to the parenteral route (3.66 and 3.60 logs of protection, respectively), it induced lower levels in serum of specific IgG (with mixed IgG1/IgG2a) and IgA antibodies and, less IFN-ɣ and IL-4 than the subcutaneous route. No antibodies were detected in vaginal lavages or saliva. Fecal antigen-specific IgA was slightly higher in mice immunized with BLSOmp31/CpG-ODN/Coa-ASC16 subcutaneously compared with the ocular route. These results indicate that BLSOmp31/CpG-ODN/Coa-ASC16 was a safe and effective vaccine against B. ovis in mice.

Asymmetric bifunctional protein nanoparticles through redesign of self-assembly

Engineering oligomeric protein self-assembly is an attractive approach to fabricate nanostructures with well-defined geometries, stoichiometry and functions. The homodecamer Brucella Lumazine Synthase (BLS) is a highly stable and immunogenic protein nanoparticle (PNP). Here, we engineered the BLS protein scaffold to display two functions in spatially opposite regions of its structure yielding a Janus-like nanoparticle. An in silico analysis of the BLS head-to-head dimer of homopentamers shows major inter-pentameric interactions located in the equatorial interface. Based on this analysis, two BLS protomer variants were designed to interrupt pentamer self-dimerization and promote heteropentameric dimers. This strategy enabled us to generate a decameric particle with two distinct sides formed by two independent pentamers. The versatility of this new self-assembly nanofabrication strategy is illustrated with two example applications. First, a bifunctional BLS bearing Alexa Fluor 488 fluorophores on one side and sialic acid binding domains on the other side was used for labelling murine and human cells and analyzed by flow cytometry and confocal microscopy. Second, multichromophoric FRET nanoparticles were fabricated and characterized at the single molecule level, showing discrete energy transfer events. The engineered BLS variants constitute a general platform for displaying two functions in a controlled manner within the same PNP with potential applications in various areas such as biomedicine, biotechnology and nanotechnology.

Mucosal immunization with polymeric antigen BLSOmp31 using alternative delivery systems against Brucella ovis in rams

Subcellular vaccines against ovine contagious epididymitis due Brucella ovis can solve some shortcomings associated with the use of Brucella melitensis Rev 1. We have demonstrated that the parenteral immunization with polymeric antigen BLSOmp31 emulsified in oil adjuvant conferred significant protection against B. ovis in rams. In our previous studies, we have characterized chitosan microspheres (ChMs) and a thermoresponsive and mucoadhesive in situ gel (Poloxamer 407-Ch) as two novel formulation strategies for the delivery of BLSOmp31 in nasal as well as conjunctival mucosa. In the present work, we evaluated the immunogenicity and protection conferred by the intranasal and conjunctival immunization with these two mucosal delivery systems against B. ovis in rams. BLSOmp31-ChM administered by intranasal route and BLSOmp31-P407-Ch applied by intranasal or conjunctival routes induced systemic, local and preputial IgG and IgA antibody response. Neither formulation showed interference in the serological diagnosis. Thus, mucosal immunization using either formulation induced significant specific cellular immune responses (in vitro and in vivo) and it prevented the excretion of B. ovis in semen. Although these vaccines did not prevent infection in immunized rams, colonization reduction of infected organs and bacterial distribution differed significantly between vaccinated and unvaccinated rams.

In silico Design, and In vitro Expression of a Fusion Protein Encoding Brucella abortus L7/L12 and SOmp2b Antigens

Background:

L7/L12 is a protective antigen conserved in main Brucella pathogens and is considered as potential vaccine candidate. Outer membrane protein 2b is an immunogen conserved in all Brucella pathogens.

Materials and Methods:

The purpose of the current study was to in silico design a L7/L12-SOmp2b fusion protein and in vitro production of the chimera. Two possible fusion forms, L7/L12-SOmp2b and SOmp2b-L7/L12, were subjected to in silico modeling and analysis. Cloning and expression of the fusion protein has been done in the pET28a vector and Escherichia coli Bl21 (DE3), respectively.

Results:

Analysis and validation of the fusion proteins three-dimensional models showed that both models are in the range of native proteins. However, L7/L12-SOmp2b structure was more valid than the SOmp2b-L7/L12 model and subjected to in vitro production. The major histocompatibility complex II (MHC-II) epitope mapping using Immune Epitope DataBase indicated that the model contained good MHC-II binders. The L7/L12-Omp2b coding sequence was cloned in pET28a vector. The fusion was successfully expressed in E. coli BL21 by induction with isopropyl-β-d-thiogalactopyranoside. The rL7/L12-SOmp2b was purified with Ni-NTA column. The yield of the purified rL7/L12-SOmp2b was estimated by Bradford method to be 240 μg/ml of the culture. Western blot analysis revealed a specific reactivity with purified rL7/L12-SOmp2b produced in E. coli cells and showed the expression in the prokaryotic system.

Conclusions:

Our data indicates that L7/L12-SOmp2b fusion protein has a potential to induce both B- and T-cell-mediated immune responses and it can be evaluated as a new subunit vaccine candidate 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.

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.

Immunogenicity Analysis of a Novel Subunit Vaccine Candidate Molecule-Recombinant L7/L12 Ribosomal Protein of Brucella suis

Brucella was an intracellular parasite, which could infect special livestock and humans. After infected by Brucella, livestock's reproductive system could be affected and destroyed resulting in huge economic losses. More seriously, it could be contagious from livestock to humans. So far, there is no available vaccine which is safe enough for humans. On this point, subunit vaccine has become the new breakthrough of conquering brucellosis. In this study, Brucella rL7/L12-BLS fusion protein was used as an antigen to immunize rabbits to detect the immunogenicity. The results of antibody level testing assay of rabbit antiserum indicated rL7/L12-BLS fusion protein could elicit rabbits to produce high-level IgG. And gamma interferon (IFN-γ) concentrations in rabbit antiserum were obviously up-regulated in both the rL7/L12 group and rL7/L12-BLS group. Besides, the results of quantitative real-time PCR (qRT-PCR) showed the IFN-γ gene's expression levels of both the rL7/L12 group and rL7/L12-BLS group were obviously up-regulated. All these results suggested Brucella L7/L12 protein was an ideal subunit vaccine candidate and possessed good immunogenicity. And Brucella lumazine synthase (BLS) molecule was a favorable transport vector for antigenic protein.

Protection Provided by an Encapsulated Live Attenuated ΔabcBA Strain of Brucella ovis against Experimental Challenge in a Murine Model

This study aimed to evaluate the Brucella ovis ΔabcBA strain as a vaccine candidate in the murine model. BALB/c mice were subcutaneously or intraperitoneally immunized with a single dose or three doses of the B. ovis ΔabcBA strain and then were challenged with wild-type B. ovis. Single or multiple immunizations provided only mild protection, with significantly smaller numbers of wild-type B. ovis CFU in the livers of immunized mice but not in the spleens. Encapsulation of B. ovis ΔabcBA significantly improved protection against experimental challenges in both BALB/c and C57BL/6 mice. Furthermore, immunization with encapsulated B. ovis ΔabcBA markedly prevented lesions in the spleens and livers of experimentally challenged mice. These results demonstrated that the encapsulated B. ovis ΔabcBA strain confers protection to mice; therefore, this strain has potential as a vaccine candidate for rams.