Protein/Protein, DNA/DNA and DNA/Protein based vaccination strategies using truncated Omp2b against Brucella infection in BALB/c Mice

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.

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.

A Solution with Ginseng Saponins and Selenium as Vaccine Diluent to Increase Th1/Th2 Immune Responses in Mice

Pseudorabies is an important infectious disease of swine, and immunization using attenuated pseudorabies virus (aPrV) vaccine is a routine practice to control this disease in swine herds. This study was to evaluate a saline solution containing ginseng stem-leaf saponins (GSLS) and sodium selenite (Se) as a vaccine adjuvant for its enhancement of immune response to aPrV vaccine. The results showed that aPrV vaccine diluted with saline containing GSLS-Se (aP-GSe) induced significantly higher immune responses than that of the vaccine diluted with saline alone (aP-S). The aP-GSe promoted higher production of gB-specific IgG, IgG1, and IgG2a, neutralizing antibody titers, secretion of Th1-type (IFN-γ, IL-2, IL-12), and Th2-type (IL-4, IL-6, IL-10) cytokines, and upregulated the T-bet/GATA-3 mRNA expression when compared to aP-S. In addition, cytolytic activity of NK cells, lymphocyte proliferation, and CD4⁺/CD8⁺ ratio was also significantly increased by aP-GSe. More importantly, aP-GSe conferred a much higher resistance of mice to a field virulent pseudorabies virus (fPrV) challenge. As the present study was conducted in mice, further study is required to evaluate the aP-GSe to improve the vaccination against PrV in swine.

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.

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.

Evaluation of immunogenicity of novel multi-epitope subunit vaccines in combination with poly I:C against Brucella melitensis and Brucella abortus infection

Brucellosis is a worldwide zoonotic disease affecting domestic animals and humans. Due to several safety problems associated with live attenuated vaccines (Rev1 and RB51), it is necessary to produce an efficient and safer vaccine against Brucella. In this study, we evaluated efficacy of two novel multi-peptide vaccine candidates of FliC, 7α-HSDH, BhuA antigens with and without poly I:C adjuvant. Hence, humoral and cellular immune responses and protective efficacy were determined in immunized mice. Our investigation indicated that multi-epitope antigens showed a significant induction of Th1 immunity with high levels of specific IgG (especially the IgG2a), as well as IFN-γ and IL-2 compared to the control group. The addition of poly I:C to multi-epitope antigens improved the humoral and cellular immune responses. The multi-epitope antigens with and without poly I:C also provided cross protection against B. melitensis16M and B. abortus544 infections. The present study suggests that the novel multi-epitope vaccine candidates based on B cell, CD4⁺ and CD8⁺T-cell epitopes of FliC, 7α-HSDH, BhuA proteins would be potential vaccine candidate against B. melitensis and B. abortus infections. Furthermore, poly I:C could be considered as a strong Th1-inducing adjuvant in designing vaccine formulation against brucellosis.

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.

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.

A review of Brucellosis in Iran: Epidemiology, Risk Factors, Diagnosis, Control, and Prevention

Brucellosis caused by species of Brucella is among the most prevalent zoonoses with the annual incidence of half a million cases globally. Most parts of Iran are endemic for brucellosis, and the annual incidence of the human and animal brucellosis is still high. At present, there is no safe and protective human vaccine against brucellosis, and the only preventive strategy is animal vaccination, which harbors significant disadvantages. Considering the identification of many immunogenic proteins in Brucella, several studies have recently been performed to evaluate the vaccine potency of such antigens as a new subunit vaccine candidate. This review represents an overview of brucellosis in Iran, including epidemiology, transmission routs, diagnosis, and treatment. Moreover, it mainly highlights the history of brucellosis control and prevention in Iran, including eradication programs, vast livestock vaccination programs, and subunit vaccine studies. It also discusses major problems that the country encounters with disease control. In recent years, Persian scientists have focused on evaluating the efficacy of best Brucella immunogens in vivo to introduce a new subunit vaccine. The results of some studies could demonstrate the vaccine potential of some immunogens.