Selection of protective epitopes for Brucella melitensis by DNA vaccination

A comprehensive comparison of DNA and RNA vaccines

Nucleic acid technology has revolutionized vaccine development, enabling rapid design and production of RNA and DNA vaccines for prevention and treatment of diseases. The successful deployment of mRNA and plasmid DNA vaccines against COVID-19 has further validated the technology. At present, mRNA platform is prevailing due to its higher efficacy, while DNA platform is undergoing rapid evolution because it possesses unique advantages that can potentially overcome the problems associated with the mRNA platform. To help understand the recent performances of the two vaccine platforms and recognize their clinical potentials in the future, this review compares the advantages and drawbacks of mRNA and DNA vaccines that are currently known in the literature, in terms of development timeline, financial cost, ease of distribution, efficacy, safety, and regulatory approval of products. Additionally, the review discusses the ongoing clinical trials, strategies for improvement, and alternative designs of RNA and DNA platforms for vaccination.

Proteome-Wide Screening of Potential Vaccine Targets against Brucella melitensis

The ongoing antibiotic-resistance crisis is becoming a global problem affecting public health. Urgent efforts are required to design novel therapeutics against pathogenic bacterial species. Brucella melitensis is an etiological agent of brucellosis, which mostly affects sheep and goats but several cases have also been reported in cattle, water buffalo, yaks and dogs. Infected animals also represent the major source of infection for humans. Development of safer and effective vaccines for brucellosis remains a priority to support disease control and eradication in animals and to prevent infection to humans. In this research study, we designed an in-silico multi-epitopes vaccine for B. melitensis using computational approaches. The pathogen core proteome was screened for good vaccine candidates using subtractive proteomics, reverse vaccinology and immunoinformatic tools. In total, 10 proteins: catalase; siderophore ABC transporter substrate-binding protein; pyridoxamine 5'-phosphate oxidase; superoxide dismutase; peptidylprolyl isomerase; superoxide dismutase family protein; septation protein A; hypothetical protein; binding-protein-dependent transport systems inner membrane component; and 4-hydroxy-2-oxoheptanedioate aldolase were selected for epitopes prediction. To induce cellular and antibody base immune responses, the vaccine must comprise both B and T-cells epitopes. The epitopes were next screened for antigenicity, allergic nature and water solubility and the probable antigenic, non-allergic, water-soluble and non-toxic nine epitopes were shortlisted for multi-epitopes vaccine construction. The designed vaccine construct comprises 274 amino acid long sequences having a molecular weight of 28.14 kDa and instability index of 27.62. The vaccine construct was further assessed for binding efficacy with immune cell receptors. Docking results revealed that the designed vaccine had good binding potency with selected immune cell receptors. Furthermore, vaccine-MHC-I, vaccine-MHC-II and vaccine-TLR-4 complexes were opted based on a least-binding energy score of -5.48 kcal/mol, 0.64 kcal/mol and -2.69 kcal/mol. Those selected were then energy refined and subjected to simulation studies to understand dynamic movements of the docked complexes. The docking results were further validated through MMPBSA and MMGBSA analyses. The MMPBSA calculated -235.18 kcal/mol, -206.79 kcal/mol, and -215.73 kcal/mol net binding free energy, while MMGBSA estimated -259.48 kcal/mol, -206.79 kcal/mol and -215.73 kcal/mol for TLR-4, MHC-I and MHC-II complexes, respectively. These findings were validated by water-swap and entropy calculations. Overall, the designed vaccine construct can evoke proper immune responses and the construct could be helpful for experimental researchers in formulation of a protective vaccine against the targeted pathogen for both animal and human use.

Antigen-Presenting, Self-Assembled Protein Nanobarrels as an Adjuvant-Free Vaccine Platform against Influenza Virus

Although naturally occurring, self-assembled protein nanoarchitectures have been utilized as antigen-delivery carriers, and the inability of such carriers to elicit immunogenicity requires additional use of strong adjuvants. Here, we report an immunogenic Brucella outer membrane protein BP26-derived nanoarchitecture displaying the influenza extracellular domain of matrix protein-2 (M2e) as a vaccine platform against influenza virus. Genetic engineering of a monomeric BP26 containing four or eight tandem repeats of M2e resulted in a hollow barrel-shaped nanoarchitecture (BP26-M2e nanobarrel). Immunization with BP26-M2e nanobarrels induced a strong M2e-specific humoral immune response in vivo that was much greater than that of a physical mixture of soluble M2e and BP26, with or without the use of an alum adjuvant. An anti-M2e antibody generated by BP26-M2e nanobarrel-immunized mice specifically bound to influenza virus-infected cells. Furthermore, in viral challenge tests, BP26-M2e nanobarrels effectively protected mice from influenza virus infection-associated death, even without the use of a conventional adjuvant. A mechanism study revealed that both M2e-specific antibody-dependent cellular cytotoxicity and T cell responses are involved in the vaccine efficacy of BP26-M2e nanobarrels. These findings suggest that the BP26-based nanobarrel developed here represents a versatile vaccine platform that can be used against various viral infections.

Trigger Factor in Association with the ClpP1P2 Heterocomplex of Leptospira Promotes Protease/Peptidase Activity

The genomic analysis of Leptospira reveals a trigger factor (TF) encoding gene (tig) to be colocalized along with the clpP1 and clpX. The TF is a crouching dragon-like protein known to be a ribosome-associated chaperone that is involved in cotranslational protein folding in bacteria in an ATP-independent mode. In Leptospira, tig is localized upstream of the clpP1 with a short (4 bp) overlap. In the present study, we document the distinctive role of Leptospira TF (LinTF) in the caseinolytic protease (ClpP) system. The recombinant LinTF (rLinTF) was found to improve the peptidase or protease activity of the ClpP1P2 heterocomplex and ClpXP1P2 complex, respectively, on model substrates. In addition, on supplementation of rLinTF to rClpP1P2 bound to its physiological ATPase chaperone ClpX or the antibiotic analogue acyldepsipeptide (ADEP), an augmentation in the activity of ClpP1P2 was observed. These studies underscore the novel role of LinTF in aiding the caseinolytic protease activity of Leptospira. Supplementation of rLinTF to a peptidase assay of rClpP1P2 conditionally in the presence of a salt (sodium citrate) with high Hofmeister strength led us to speculate that rLinTF may have a role in the assembly of multimeric proteins. The deletion of one of the arms (arm-2) of the LinTF structure from the carboxy terminal domain indicated a reduction in its capacity to stimulate rClpP1P2 activity. Thus, the C-terminal domain of LinTF may have a role in the assembly of multimeric ClpP protein, leading to enhancement of ClpP activity.

Structural analysis of a Simpl-like protein from Campylobacter jejuni

Signaling molecule that interacts with mouse pelle-like kinase (Simpl) is an animal protein that contributes to the regulation of inflammatory responses. Although Simpl-like proteins (SLPs) are mainly found in bacteria, functional and structural studies on bacterial SLPs are limited to BP26, a periplasmic protein from Brucella species. We identified a group of bacterial SLPs, including Campylobacter jejuni SLP (cjSLP) and Shewanella putrefaciens SLP (spSLP), that exhibit significant sequence variation from Simpl and BP26. To address the structural and oligomeric diversities of SLPs, we determined the crystal structure of cjSLP and performed a comparative analysis of SLP structures. cjSLP adopts a boomerang-shaped, two-domain structure, and each domain of cjSLP adopts an α-helix-decorated β-sheet structure as observed in BP26. This observation suggests that the duplicated α/β structure would be the canonical fold of the Simpl family. Despite the fold similarity, cjSLP exhibits a more open interdomain organization than BP26 and displays unique local structural features that are not observed in BP26. Furthermore, cjSLP and its ortholog spSLP are monomeric in solution in contrast to the hexadecameric assembly of BP26. Therefore, we conclude that cjSLP represents a unique bacterial SLP group that is distinct from BP26 in both structures and oligomeric states.

Binding of Brucella protein, Bp26, to select extracellular matrix molecules

BACKGROUND

Brucella is a facultative intracellular pathogen responsible for zoonotic disease brucellosis. Little is known about the molecular basis of Brucella adherence to host cells. In the present study, the possible role of Bp26 protein as an adhesin was explored. The ability of Brucella protein Bp26 to bind to extracellular matrix (ECM) proteins was determined by enzyme-linked immunosorbent assay (ELISA) and biolayer interferometry (BLI).

RESULTS

ELISA experiments showed that Bp26 bound in a dose-dependent manner to both immobilized type I collagen and vitronectin. Bp26 bound weakly to soluble fibronectin but did not bind to immobilized fibronectin. No binding to laminin was detected. Biolayer interferometry showed high binding affinity of Bp26 to immobilized type I collagen and no binding to fibronectin or laminin. Mapping of Bp26 antigenic epitopes by biotinylated overlapping peptides spanning the entire sequence of Bp26 using anti Bp26 mouse serum led to the identification of five linear epitopes. Collagen and vitronectin bound to peptides from several regions of Bp26, with many of the binding sites for the ligands overlapping. The strongest binding for anti-Bp26 mouse serum, collagen and vitronectin was to the peptides at the C-terminus of Bp26. Fibronectin did not bind to any of the peptides, although it bound to the whole Bp26 protein.

CONCLUSIONS

Our results highlight the possible role of Bp26 protein in the adhesion process of Brucella to host cells through ECM components. This study revealed that Bp26 binds to both immobilized and soluble type I collagen and vitronectin. It also binds to soluble but not immobilized fibronectin. However, Bp26 does not bind to laminin. These are novel findings that offer insight into understanding the interplay between Brucella and host target cells, which may aid in future identification of a new target for diagnosis and/or vaccine development and prevention of brucellosis.

Research Progress on Brucellosis

Brucellosis is a debilitating febrile illness caused by an intracellular Brucella. The disease is distributed in humans and animals widely, especially in developing countries. Ten species are included in the genus Brucella nowadays; four species of them are pathogenic to humans, which make brucellosis a zoonosis with more than 500,000 new cases reported annually. For human brucellosis, the most pathogenic species is B. melitensis followed by B. suis, while B. abortus is the mildest type of brucellosis. The infection mechanism of Brucella is complicated and mostly relies on its virulence factors. The therapy of the disease contains vaccination and antibiotic. However, there are some defects in currently available vaccines such as the lower protective level and safety. Thus, safe and efficient vaccines for brucellosis are still awaited. The dual therapy of antibacterial is effective in the treatment of brucellosis if a rapid and exact detection method is found.

Immunogenic and protective antigens of Brucella as vaccine candidates

Brucella is an intracellular pathogen that causes abortion in domestic animals and undulant fever in humans. Due to the lack of a human vaccine against brucellosis, animal vaccines play an important role in the management of animal and human brucellosis for decades. Strain 19, RB51 and Rev1 are the approved Brucella spp. vaccine strains that are most commonly used to protect livestock against infection and abortion. However, due to some disadvantages of these vaccines, numerous studies have been conducted for the development of effective vaccines that could also be used in other susceptible animals. In this review, we compare different aspects of immunogenic antigens that have been a candidate for the brucellosis vaccine.

Streptococcus pneumoniae Cell Wall-Localized Trigger Factor Elicits a Protective Immune Response and Contributes to Bacterial Adhesion to the Host

Trigger factor (TF) has a known cytoplasmic function as a chaperone. In a previous study we showed that pneumococcal TF is also cell-wall localized and this finding combined with the immunogenic characteristic of TF, has led us to determine the vaccine potential of TF and decipher its involvement in pneumococcal pathogenesis. Bioinformatic analysis revealed that TF is conserved among pneumococci and has no human homologue. Immunization of mice with recombinant (r)TF elicited a protective immune response against a pneumococcal challenge, suggesting that TF contributes to pneumococcal pathogenesis. Indeed, rTF and an anti-rTF antiserum inhibited bacterial adhesion to human lung derived epithelial cells, indicating that TF contributes to the bacterial adhesion to the host. Moreover, bacteria lacking TF demonstrated reduced adhesion, in vitro, to lung-derived epithelial cells, neural cells and glial cells. The reduced adhesion could be restored by chromosomal complementation. Furthermore, bacteria lacking TF demonstrated significantly reduced virulence in a mouse model. Taken together, the ability of rTF to elicit a protective immune response, involvement of TF in bacterial adhesion, conservation of the protein among pneumococcal strains and the lack of human homologue, all suggest that rTF can be considered as a future candidate vaccine with a much broader coverage as compared to the currently available pneumococcal vaccines.

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.

Alternative strategies for vaccination to brucellosis

Brucellosis remains burdensome for livestock and humans worldwide. Better vaccines for protection are needed to reduce disease incidence. Immunity to brucellosis and barriers to protection are discussed. The benefits and limitations of conventional and experimental brucellosis vaccines are outlined, and novel vaccination strategies needed to ultimately protect against brucellosis are introduced.

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.

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.

Development of a multi-epitope peptide vaccine inducing robust T cell responses against brucellosis using immunoinformatics based approaches

Current investigations have demonstrated that a multi-epitope peptide vaccine targeting multiple antigens could be considered as an ideal approach for prevention and treatment of brucellosis. According to the latest findings, the most effective immunogenic antigens of brucella to induce immune responses are included Omp31, BP26, BLS, DnaK and L7-L12. Therefore, in the present study, an in silico approach was used to design a novel multi-epitope vaccine to elicit a desirable immune response against brucellosis. First, five novel T-cell epitopes were selected from Omp31, BP26, BLS, DnaK and L7-L12 proteins using different servers. In addition, helper epitopes selected from Tetanus toxin fragment C (TTFrC) were applied to induce CD4+ helper T lymphocytes (HTLs) responses. Selected epitopes were fused together by GPGPG linkers to facilitate the immune processing and epitope presentation. Moreover, cholera toxin B (CTB) was linked to N terminal of vaccine construct as an adjuvant by using EAAAK linker. A multi-epitope vaccine was designed based on predicted epitopes which was 377 amino acid residues in length. Then, the physico-chemical properties, secondary and tertiary structures, stability, intrinsic protein disorder, solubility and allergenicity of this multi-epitope vaccine were assessed using immunoinformatics tools and servers. Based on obtained results, a soluble, and non-allergic protein with 40.59kDa molecular weight was constructed. Expasy ProtParam classified this chimeric protein as a stable protein and also 89.8% residues of constructed vaccine were located in favored regions of the Ramachandran plot. Furthermore, this multi-epitope peptide vaccine was able to strongly induce T cell and B-cell mediated immune responses. In conclusion, immunoinformatics analysis indicated that this multi-epitope peptide vaccine can be effectively expressed and potentially be used for prophylactic or therapeutic usages against brucellosis.

Immuno-pathophysiological responses of mouse model to experimental infection with Brucella melitensis and its lipopolysaccharides via intraperitoneal route

Brucella melitensis is one of the major zoonotic pathogens with significant economic implications worldwide. The pathogenicity is complex and not always well understood. Lipopolysaccharide (LPS) remains the major virulent factor of B. melitensis and responsible for the mechanism by which the pathogen causes its deleterious effects. In this study, 84 mice of 6-8 weeks old of both sexes were divided equally into 3 groups; namely Brucella melitensis infected group, lipopolysaccharide (LPS) infected group and control group. The former two groups contained 36 mice each with equal gender distribution. The control group consisted of 12 mice only. Animals in B. melitensis infected group, a single inoculum of 0.4 ml containing 10⁹ of B. melitensis were intraperitoneally challenged while animals in LPS group, a single dose of 0.4 ml containing LPS extracted from the B. melitensis were intraperitoneally inoculated. Animals in control group received intraperitoneally, a single dose of 0.4 ml phosphate buffered saline (PBS) of pH7. Animals that were infected intraperitoneally with B. melitensis demonstrated significant clinical presentation; gross and histo-pathological evidence than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1β and IL6), antibody levels (IgM an IgG) as early as 3 days post-infection with predominance in LPS infected group. In contrast, low levels of sex related hormonal changes in which LPS infected group showed the least concentration were also detected throughout the experimental period. In conclusion, B. melitensis can be transmitted via gastrointestinal, respiratory and reproductive tract. Moreover, LPS stimulated significantly the innate and acquired immune system without significant systemic dysfunction, suggesting potentiality of the protective properties of this component as alternative vaccine for brucellosis infection.

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.

Immune reactivity of sera obtained from brucellosis patients and vaccinated-rabbits to a fusion protein from Brucella melitensis

OBJECTIVES

Brucella spp. are facultative intracellular pathogens which can stay alive and multiply in professional and nonprofessional phagocytes. Immunity against Brucella melitensis involves antigen-specific CD4(+) and CD8(+) T-cells activation and humoral immune responses. Due to negative aspects of live attenuated vaccines, much attention has been focused on finding Brucella-protective antigens to introduce them as potential subunit vaccine candidates.

MATERIALS AND METHODS

A chimeric gene encoding trigger factor (TF), Omp31(48-74) and BP26(87-111) fragments (TOB) from B. melitensis was successfully cloned, expressed in Escherichia coli BL21-DE3 and purified by Ni-NTA agarose column. Antibodies to recombinant TOB (rTOB) have been investigated in Brucella-infected human sera and a pool serum prepared from B. melitensis-vaccinated rabbits.

RESULTS

Our results showed that the immunized rabbit pool serum strongly reacted with rTOB. In addition, antibodies against rTOB were detectable in 76.5% of sera obtained from infected patients.

CONCLUSION

These findings suggest that rTOB may provide a potential immunogenic candidate which could be considered in future vaccine studies.

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.

Brucella melitensis T cell epitope recognition in humans with brucellosis in Peru

Brucella melitensis, one of the causative agents of human brucellosis, causes acute, chronic, and relapsing infection. While T cell immunity in brucellosis has been extensively studied in mice, no recognized human T cell epitopes that might provide new approaches to classifying and prognosticating B. melitensis infection have ever been delineated. Twenty-seven pools of 500 major histocompatibility complex class II (MHC-II) restricted peptides were created by computational prediction of promiscuous MHC-II CD4(+) T cell derived from the top 50 proteins recognized by IgG in human sera on a genome level B. melitensis protein microarray. Gamma interferon (IFN-γ) and interleukin-5 (IL-5) enzyme-linked immunospot (ELISPOT) analyses were used to quantify and compare Th1 and Th2 responses of leukapheresis-obtained peripheral blood mononuclear cells from Peruvian subjects cured after acute infection (n = 9) and from patients who relapsed (n = 5). Four peptide epitopes derived from 3 B. melitensis proteins (BMEI 1330, a DegP/HtrA protease; BMEII 0029, type IV secretion system component VirB5; and BMEII 0691, a predicted periplasmic binding protein of a peptide transport system) were found repeatedly to produce significant IFN-γ ELISPOT responses in both acute-infection and relapsing patients; none of the peptides distinguished the patient groups. IL-5 responses against the panel of peptides were insignificant. These experiments are the first to systematically identify B. melitensis MHC-II-restricted CD4(+) T cell epitopes recognized by the human immune response, with the potential for new approaches to brucellosis diagnostics and understanding the immunopathogenesis related to this intracellular pathogen.

Immune reactivity of Brucella melitensis-vaccinated rabbit serum with recombinant Omp31 and DnaK proteins

BACKGROUND AND OBJECTIVES

Brucella melitensis infection is still a major health problem for human and cattle in developing countries and the Middle East.

MATERIALS AND METHODS

In this study, in order to screen immunogenic candidate antigens for the development of a Brucella subunit vaccine, a cytoplasmic protein (DnaK) and an outer membrane protein (Omp31) of B. melitensis were cloned, expressed in E.coli BL21 and then purified using Ni-NTA agarose. Immunized serum was prepared from a rabbit inoculated with attenuated B. melitensis.

RESULTS AND CONCLUSION

It was proved that immunized serum contains antibodies against recombinant Omp31 (rOmp31) and DnaK (rDnaK) by Western blot and ELISA assays. The results may suggest the importance of these proteins as subunit vaccines against B. melitensis as well as targets for immunotherapy.

Progress in Brucella vaccine development

Brucella spp. are zoonotic, facultative intracellular pathogens, which cause animal and human disease. Animal disease results in abortion of fetuses; in humans, it manifests flu-like symptoms with an undulant fever, with osteoarthritis as a common complication of infection. Antibiotic regimens for human brucellosis patients may last several months and are not always completely effective. While there are no vaccines for humans, several licensed live Brucella vaccines are available for use in livestock. The performance of these animal vaccines is dependent upon the host species, dose, and route of immunization. Newly engineered live vaccines, lacking well-defined virulence factors, retain low residual virulence, are highly protective, and may someday replace currently used animal vaccines. These also have possible human applications. Moreover, due to their enhanced safety and efficacy in animal models, subunit vaccines for brucellosis show great promise for their application in livestock and humans. This review summarizes the progress of brucellosis vaccine development and presents an overview of candidate vaccines.

Brucella immunogenic BP26 forms a channel-like structure

An outer membrane protein BP26/OMP28 of Brucella, BP26, is identified as a major immunodominant antigen and widely used as a diagnostic marker and for vaccination against Brucellosis. BP26 belongs to the family of proteins that contains a SIMPL (signaling molecule that associates with the mouse pelle-like kinase) domain, whose structure and function have been unknown. Here, we present the crystal structure of BP26 revealing that 16 BP26 molecules form a novel channel-like assembly as also shown by electron microscopy analysis. Eight BP26 molecules forming a ring structure contain a hole at the center of the octamer, and another octamer interacts with each other to form a channel having a large internal cavity. BP26 is found to be structurally similar to a bacteriophage protein involved in infection, implicating that BP26 might function during Brucella infection. In addition, the BP26 structure suggests that the protein functions as a multimeric channel-like form and provides a canonical model for the SIMPL domains.

Immunogenicity and protective potential of a bacterially expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in BALB/c mice

Brucellosis is one of the world's major zoonoses. No vaccine is available for the prevention of brucellosis in human. Efforts are needed to develop an effective, safe, stable, vaccine with long lasting immunity against human brucellosis. Here, we cloned and expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in Escherichia coli and purified up to homogeneity by metal affinity chromatography. The purified rE2o is immunoreactive with brucellosis positive cattle sera. The immunogenicity and the protective potential of recombinant dihydrolipoamide succinyltransferase (rE2o) were evaluated in BALB/c mice with two different adjuvants i.e., Freund's and aluminium hydroxide gel. Mice were tested for humoral immune response by ELISA. Cell mediated immune response was tested by lymphocyte proliferation assay and cytokine profiling. The recombinant E2o (rE2o) generated high IgG antibody and its isotypes IgG1, and induced significant production of INF-γ, IL-10 and IL-4 cytokines. The rE2o protein induced significant lymphoproliferation of splenocytes. Altogether, these results suggest that rE2o induces a mixed but a predominant Th2 type of immune response in BALB/c mice and provides partial protection against challenge with pathogenic Brucella abortus.

Characterization of periplasmic protein BP26 epitopes of Brucella melitensis reacting with murine monoclonal and sheep antibodies

More than 35,000 new cases of human brucellosis were reported in 2010 by the Chinese Center for Disease Control and Prevention. An attenuated B. melitensis vaccine M5-90 is currently used for vaccination of sheep and goats in China. In the study, a periplasmic protein BP26 from M5-90 was characterized for its epitope reactivity with mouse monoclonal and sheep antibodies. A total of 29 monoclonal antibodies (mAbs) against recombinant BP26 (rBP26) were produced, which were tested for reactivity with a panel of BP26 peptides, three truncated rBP26 and native BP26 containing membrane protein extracts (NMP) of B. melitensis M5-90 in ELISA and Western-Blot. The linear, semi-conformational and conformational epitopes from native BP26 were identified. Two linear epitopes recognized by mAbs were revealed by 28 of 16mer overlapping peptides, which were accurately mapped as the core motif of amino acid residues ⁹³DRDLQTGGI¹⁰¹ (position 93 to 101) or residues ¹⁰⁴QPIYVYPD¹¹¹, respectively. The reactivity of linear epitope peptides, rBP26 and NMP was tested with 137 sheep sera by ELISAs, of which the two linear epitopes had 65–70% reactivity and NMP 90% consistent with the results of a combination of two standard serological tests. The results were helpful for evaluating the reactivity of BP26 antigen in M5-90.

Antigen-specific acquired immunity in human brucellosis: implications for diagnosis, prognosis, and vaccine development

Brucella spp., are Gram negative bacteria that cause disease by growing within monocyte/macrophage lineage cells. Clinical manifestations of brucellosis are immune mediated, not due to bacterial virulence factors. Acquired immunity to brucellosis has been studied through observations of naturally infected hosts (cattle, goats), mouse models (mice), and human infection. Even though Brucella spp. are known for producing mechanisms that evade the immune system, cell-mediated immune responses drive the clinical manifestations of human disease after exposure to Brucella species, as high antibody responses are not associated with protective immunity. The precise mechanisms by which cell-mediated immune responses confer protection or lead to disease manifestations remain undefined. Descriptive studies of immune responses in human brucellosis show that TH₁ (interferon-γ-producing T cells) are associated with dominant immune responses, findings consistent with animal studies. Whether these T cell responses are protective, or determine the different clinical responses associated with brucellosis is unknown, especially with regard to undulant fever manifestations, relapsing disease, or are associated with responses to distinct sets of Brucella spp. antigens are unknown. Few data regarding T cell responses in terms of specific recognition of Brucella spp. protein antigens and peptidic epitopes, either by CD4+ or CD8+ T cells, have been identified in human brucellosis patients. Additionally because current attenuated Brucella vaccines used in animals cause human disease, there is a true need for a recombinant protein subunit vaccine for human brucellosis, as well as for improved diagnostics in terms of prognosis and identification of unusual forms of brucellosis. This review will focus on current understandings of antigen-specific immune responses induced Brucella peptidic epitopes that has promise for yielding new insights into vaccine and diagnostics development, and for understanding pathogenetic mechanisms of human brucellosis.

Prospects for the future using genomics and proteomics in clinical microbiology

The availability of genome sequences has revolutionized the fields of microbiology and infectious diseases. Indeed, more than 1,000 bacterial genomes and 3,000 viral genomes, including representatives of all significant human pathogens, have been sequenced to date. Owing to this tremendous amount of data, genomes are regarded as chimeras of sequence fragments from various origins. Coupled with novel proteomic analyses, genome sequencing has also resulted in unprecedented advances in pathogen diagnosis and genotyping and in the detection of virulence and antibiotic resistance. Herein, we review current achievements of genomics and proteomics and discuss potential developments for clinical microbiology laboratories.

Serial kinetics of the antibody response against the complete Brucella melitensis ORFeome in focal vertebral brucellosis

Human brucellosis is a common zoonosis worldwide. Here we present a case of focal vertebral brucellosis in a 71-year-old Mexican-American woman who contracted infection from unpasteurized goat milk. Standard agglutination serology was negative; the diagnosis was established by the isolation of Brucella melitensis from abscess fluid. A B. melitensis protein microarray comprised of nearly all proteins encoded by the bacterial genome was used to determine the kinetics of this patient's antibody responses to the complete collection of open reading frames existing in the genome (ORFeome). Three patterns of antibody responses against B. melitensis antigens were seen for serum samples obtained on days 0 (pretreatment), 14, 49, 100, and 180: (i) stable titers over time, (ii) a steady fall in titers, and (iii) an initial rise in titers followed by declining titers. Sera from this patient with chronic brucellosis recognized some of the same B. melitensis proteins as those recognized by sera from acute/subacute, blood culture-positive brucellosis patients but also recognized a distinct set of proteins. This study is the first to determine the kinetics of the human antibody responses to the complete repertoire of proteins encoded by a bacterial genome and demonstrates fundamentally different immunopathogenetic mechanisms between acute human brucellosis and chronic human brucellosis. While an extension of these findings to a larger patient population is necessary, these findings have important clinical and diagnostic implications and lead toward new insights into the fundamental immunopathogenesis of brucellosis.

Identification of immunogenic proteins within distinct molecular mass fractions of Flavobacterium psychrophilum

Flavobacterium psychrophilum is the aetiological agent of bacterial coldwater disease (CWD), and this pathogen has large economic impacts on salmonid aquaculture worldwide. Previously, it was demonstrated that high levels of protection against F. psychrophilum challenge were conferred to rainbow trout, Oncorhynchus mykiss (Walbaum), by immunization with distinct molecular mass fractions of the bacterium, and specific antibodies were correlated with protection. In this study, an immunoproteomic analysis of F. psychrophilum was performed using two-dimensional polyacrylamide gel electrophoresis and Western blotting with serum from fish immunized with high- and mid-molecular mass fractions of the bacterium. Mass spectrometry was used to determine the protein identity, and 15 immunogenic proteins were positively identified following Mascot searches of the F. psychrophilum genome. Based on known function and immunogenicity of homologous proteins in other bacterial pathogens, antibodies specific for several of the identified proteins may be important for protective immunity from CWD. These include outer membrane protein OmpA (P60), trigger factor, ClpB, elongation factor G, gliding motility protein GldN and a conserved hypothetical protein. This work increases the understanding of the protective humoral immune response of rainbow trout against these distinct molecular mass fractions of F. psychrophilum and provides new potential targets for recombinant protein vaccine development.

Systems biology approach predicts antibody signature associated with Brucella melitensis infection in humans

A complete understanding of the factors that determine selection of antigens recognized by the humoral immune response following infectious agent challenge is lacking. Here we illustrate a systems biology approach to identify the antibody signature associated with Brucella melitensis (Bm) infection in humans and predict proteomic features of serodiagnostic antigens. By taking advantage of a full proteome microarray expressing previously cloned 1406 and newly cloned 1640 Bm genes, we were able to identify 122 immunodominant antigens and 33 serodiagnostic antigens. The reactive antigens were then classified according to annotated functional features (COGs), computationally predicted features (e.g., subcellular localization, physical properties), and protein expression estimated by mass spectrometry (MS). Enrichment analyses indicated that membrane association and secretion were significant enriching features of the reactive antigens, as were proteins predicted to have a signal peptide, a single transmembrane domain, and outer membrane or periplasmic location. These features accounted for 67% of the serodiagnostic antigens. An overlay of the seroreactive antigen set with proteomic data sets generated by MS identified an additional 24%, suggesting that protein expression in bacteria is an additional determinant in the induction of Brucella-specific antibodies. This analysis indicates that one-third of the proteome contains enriching features that account for 91% of the antigens recognized, and after B. melitensis infection the immune system develops significant antibody titers against 10% of the proteins with these enriching features. This systems biology approach provides an empirical basis for understanding the breadth and specificity of the immune response to B. melitensis and a new framework for comparing the humoral responses against other microorganisms.

Cloning, expression and purification of Pwo polymerase from Pyrococcus woesei

BACKGROUND AND OBJECTIVES

Pyrococcus woesei is a hyperthermophilic archaea and produces a heat stable polymerase (Pwo polymerase) that has proofreading activity.

MATERIALS AND METHODS

In this study, this microorganism was cultured, its DNA was extracted and the pwo gene polymerase was cloned, expressed and purified. The DNA sequence of the cloned gene was verified by sequencing. The pwo polymerase gene consists of 2,328 bps (775 amino acids with about 90 kD molecular weight). Cloning was done by GATEWAY™ Cloning System and for purification of recombinant protein; His6x-Tag was added to the C-terminus of the recombinant protein.

RESULTS AND CONCLUSION

We could purify Pwo polymerase enzyme by Ni-NTA resin. PCR assay showed that Pwo polymerase activity is comparable to a commercial Pfu polymerase activity.

Murine and bovine γδ T cells enhance innate immunity against Brucella abortus infections

γδ T cells have been postulated to act as a first line of defense against infectious agents, particularly intracellular pathogens, representing an important link between the innate and adaptive immune responses. Human γδ T cells expand in the blood of brucellosis patients and are active against Brucella in vitro. However, the role of γδ T cells in vivo during experimental brucellosis has not been studied. Here we report TCRδ^−/− mice are more susceptible to B. abortus infection than C57BL/6 mice at one week post-infection as measured by splenic colonization and splenomegaly. An increase in TCRγδ cells was observed in the spleens of B. abortus-infected C57BL/6 mice, which peaked at two weeks post-infection and occurred concomitantly with diminished brucellae. γδ T cells were the major source of IL-17 following infection and also produced IFN-γ. Depletion of γδ T cells from C57BL/6, IL-17Rα^−/−, and GMCSF^−/− mice enhanced susceptibility to B. abortus infection although this susceptibility was unaltered in the mutant mice; however, when γδ T cells were depleted from IFN-γ^−/− mice, enhanced susceptibility was observed. Neutralization of γδ T cells in the absence of TNF-α did not further impair immunity. In the absence of TNF-α or γδ T cells, B. abortus-infected mice showed enhanced IFN-γ, suggesting that they augmented production to compensate for the loss of γδ T cells and/or TNF-α. While the protective role of γδ T cells was TNF-α-dependent, γδ T cells were not the major source of TNF-α and activation of γδ T cells following B. abortus infection was TNF-α-independent. Additionally, bovine TCRγδ cells were found to respond rapidly to B. abortus infection upon co-culture with autologous macrophages and could impair the intramacrophage replication of B. abortus via IFN-γ. Collectively, these results demonstrate γδ T cells are important for early protection to B. abortus infections.

DNA vaccination of bison to brucellar antigens elicits elevated antibody and IFN-γ responses

Brucella abortus remains a threat to the health and well-being of livestock in states bordering the Greater Yellowstone Area. During the past several years, cohabitation of infected wildlife with cattle has jeopardized the brucellosis-free status of Idaho, USA; Wyoming, USA; and Montana, USA. Current livestock B. abortus vaccines have not proven to be efficacious in bison (Bison bison) or elk (Cervus elaphus nelsoni). One problem with the lack of vaccine efficacy may stem from the failure to understand wildlife immune responses to vaccines. In an attempt to understand their immune responses, bison were vaccinated with eukaryotic DNA expression vectors encoding the Brucella periplasmic protein, bp26, and the chaperone protein, trigger factor (TF). These DNA vaccines have previously been shown to be protective against Brucella infection in mice. Bison were immunized intramuscularly at weeks 0, 2, and 4 with bp26 and TF DNA vaccines plus CpG adjuvant or empty vector (control) plus CpG. Blood samples were collected before vaccination and at 8, 10, and 12 wk after primary vaccination. The results showed that bison immunized with bp26 and TF DNA vaccines developed enhanced antibody, proliferative T cell, and interferon-gamma (IFN-γ) responses upon in vitro restimulation with purified recombinant bp26 or TF antigens, unlike bison immunized with empty vector. Flow cytometric analysis revealed that the percentages of CD4(+) and CD8(+) T lymphocytes from the DNA-vaccinated groups were significantly greater than they were for those bison given empty vector. These data suggest that DNA vaccination of bison may elicit strong cellular immune responses and serve as an alternative for vaccination of bison for brucellosis.

Immunization of mice with gamma-irradiated Brucella neotomae and its recombinant strains induces protection against virulent B. abortus, B. melitensis, and B. suis challenge

Human brucellosis, a zoonotic disease of major public health concern in several developing countries, is primarily caused by Brucella abortus, Brucella melitensis, and Brucella suis. No brucellosis vaccine is available for human use. The aim of this study was to determine if Brucella neotomae, a bacterium not known to cause disease in any host, can be used for developing brucellosis vaccines. B. neotomae and its recombinant strains overexpressing superoxide dismutase and a 26 kDa periplasmic protein were rendered non-replicative through exposure to gamma-radiation and used as vaccines in a murine brucellosis model. All three vaccines induced antigen-specific antibody and T cell responses. The vaccinated mice showed significant resistance against challenge with virulent B. abortus 2308, B. melitensis 16 M, and B. suis 1330. These results demonstrate that the avirulent B. neotomae is a promising platform for developing a safe and effective vaccine for human brucellosis.

Liposomal delivery of p-ialB and p-omp25 DNA vaccines improves immunogenicity but fails to provide full protection against B. melitensis challenge

Background

We have previously demonstrated protective efficacy against B. melitensis using formulations of naked DNA vaccines encoding genes ialB and omp25. The present study was undertaken to further understand the immune response generated by the protective vaccination regimens and to evaluate cationic liposome adsorption as a delivery method to improve vaccine utility.

Methods

The protective efficacy and immunogenicity of vaccines delivered as four doses of naked DNA, a single dose of naked DNA or a single dose of DNA surface adsorbed to cationic liposomes were compared using the BALB/c murine infection model of B. melitensis. Antigen-specific T cells and antibody responses were compared between the various formulations.

Results

The four dose vaccination strategy was confirmed to be protective against B. melitensis challenge. The immune response elicited by the various vaccines was found to be dependent upon both the antigen and the delivery strategy, with the IalB antigen favouring CD4+ T cell priming and Omp25 antigen favouring CD8+. Delivery of the p-ialB construct as a lipoplex improved antibody generation in comparison to the equivalent quantity of naked DNA. Delivery of p-omp25 as a lipoplex altered the profile of responsive T cells from CD8+ to CD4+ dominated. Under these conditions neither candidate delivered by single dose naked DNA or lipoplex vaccination methods was able to produce a robust protective effect.

Conclusions

Delivery of the p-omp25 and p-ialB DNA vaccine candidates as a lipoplex was able to enhance antibody production and effect CD4+ T cell priming, but was insufficient to promote protection from a single dose of either vaccine. The enhancement of immunogenicity by lipoplex delivery is a promising step toward improving the practicality of these two candidate vaccines, and suggests that this lipoplex formulation may be of value in situations where improvements to CD4+ responses are required. However, in the case of Brucella vaccine development it is suggested that further modifications to the candidate vaccines and delivery strategies will be required in order to deliver sustained protection.

Large scale immune profiling of infected humans and goats reveals differential recognition of Brucella melitensis antigens

Brucellosis is a widespread zoonotic disease that is also a potential agent of bioterrorism. Current serological assays to diagnose human brucellosis in clinical settings are based on detection of agglutinating anti-LPS antibodies. To better understand the universe of antibody responses that develop after B. melitensis infection, a protein microarray was fabricated containing 1,406 predicted B. melitensis proteins. The array was probed with sera from experimentally infected goats and naturally infected humans from an endemic region in Peru. The assay identified 18 antigens differentially recognized by infected and non-infected goats, and 13 serodiagnostic antigens that differentiate human patients proven to have acute brucellosis from syndromically similar patients. There were 31 cross-reactive antigens in healthy goats and 20 cross-reactive antigens in healthy humans. Only two of the serodiagnostic antigens and eight of the cross-reactive antigens overlap between humans and goats. Based on these results, a nitrocellulose line blot containing the human serodiagnostic antigens was fabricated and applied in a simple assay that validated the accuracy of the protein microarray results in the diagnosis of humans. These data demonstrate that an experimentally infected natural reservoir host produces a fundamentally different immune response than a naturally infected accidental human host.

Brucellosis is a bacterial disease transmitted from infected animals to humans. This disease often presents as a prolonged but non-specific illness primarily characterized as fever without specific organ localization. Because infections can result after ingestion (typically from unpasteurized animal milk or milk products from goats, cattle or sheep) or inhalation (important because of bioterrorism potential) of small numbers of organisms, the bacteria that cause brucellosis are potential biological warfare agents. Here, a protein microarray containing 1406 Brucella melitensis proteins was used to study the antibody response of experimentally infected goats and naturally infected humans in B. melitensis infection. Goats recognized 18 proteins and humans recognized 13 proteins as serodiagnostic antigens; antibody detection of only two of these antigens was shared by goats and humans, suggesting either fundamentally different immune responses or different responses in relation to mode or setting of infection. The human serodiagnostic antigens were evaluated in a simple nitrocellulose line blot assay, which validated the protein microarray results. The approach described here will lead to the development of new diagnostics for brucellosis and other infectious diseases, and aid in understanding the human and animal host immune response to pathogenic organisms.

A parenteral DNA vaccine protects against pneumonic plague

The chemokine, lymphotactin (LTN), was tested as a molecular adjuvant using bicistronic DNA vaccines encoding the protective Yersinia capsular (F1) antigen and virulence antigen (V-Ag) as a F1-V fusion protein. The LTN-encoding F1-V or V-Ag vaccines were given by the intranasal (i.n.) or intramuscular (i.m.) routes, and although serum IgG and mucosal IgA antibodies (Abs) were induced, F1-Ag boosts were required for robust anti-F1-Ag Abs. Optimal efficacy against pneumonic plague was obtained in mice i.m.-, not i.n.-immunized with these DNA vaccines. These vaccines stimulated elevated Ag-specific Ab-forming cells and mixed Th cell responses, with Th17 cells markedly enhanced by i.m. immunization. These results show that LTN can be used as a molecular adjuvant to enhance protective immunity against plague.

Towards a Brucella vaccine for humans

There is currently no licensed vaccine for brucellosis in humans. Available animal vaccines may cause disease and are considered unsuitable for use in humans. However, the causative pathogen, Brucella, is among the most common causes of laboratory-acquired infections and is a Center for Disease Control category B select agent. Thus, human vaccines for brucellosis are required. This review highlights the considerations that are needed in the journey to develop a human vaccine, including animal models, and includes an assessment of the current status of novel vaccine candidates.

Protection of mice against Brucella abortus 544 challenge by vaccination with recombinant OMP28 adjuvanted with CpG oligonucleotides

Brucella abortus, a gram negative, facultative intracellular pathogen causes brucellosis in many animal species and humans. Although live, attenuated vaccines are available against this infection, they suffer from certain limitations. Therefore, the development of an effective subunit vaccine against brucellosis is an area of intense research. The outer membrane proteins (OMPs) of Brucella species have been extensively studied for its immunogenicity and protective ability. We have investigated the potential of CpG ODN to enhance the immunogenicity and protective efficacy of recombinant 28 kDa outer membrane protein (rOMP28) of Brucella melitensis. The study demonstrated vigorous immunoglobulin G (IgG) response of OMP28. The administration of rOMP28 with CpG caused increased cell mediated immune response in terms of induced IgG2a, T-cell proliferation and up-regulation of type I cytokine expression. In contrast, the free antigen suppressed the interferon gamma (type I cytokine) production on in-vitro stimulation of spleenocytes. The result indicates the role of OMP28 in the down regulation of IFN-gamma production. Moreover, the B. abortus S-19 vaccinated mice showed highest production of IL-4 and IFN-gamma. The protective ability of the antigen was evaluated by systemic bacterial clearance after challenging the mouse with B. abortus 544 pathogen. The level of protection was significant in rOMP28+CpG treated mice but was lower than the required level. The results of the present study indicate that rOMP28 could be an immunogen capable of inducing both humoral and cellular immune response. The humoral response was biased towards Th1 type when it was co-administered with CpG.