Production and efficacy of a low-cost recombinant pneumococcal protein polysaccharide conjugate vaccine

Escherichia coli in the production of biopharmaceuticals

Escherichia coli has shouldered a massive workload with the discovery of recombinant DNA technology. A new era began in the biopharmaceutical industry with the production of insulin, the first recombinant protein, in E. coli and its use in treating diabetes. After insulin, many biopharmaceuticals produced from E. coli have been approved by the US Food and Drug Administration and the European Medicines Agency to treat various human diseases. Although E. coli has some disadvantages, such as lack of post-translational modifications and toxicity, it is an important host with advantages such as being a well-known bacterium in recombinant protein production, cheap, simple production system, and high yield. This study examined biopharmaceuticals produced and approved in E. coli under the headings of peptides, hormones, enzymes, fusion proteins, antibody fragments, vaccines, and other pharmaceuticals. The topics on which these biopharmaceuticals were approved for treating human diseases, when and by which company they were produced, and their use and development in the field are included.

Recombinant production platform for Group A Streptococcus glycoconjugate vaccines

Group A Streptococcus (Strep A) is a human-exclusive bacterial pathogen killing annually more than 500,000 patients, and no current licensed vaccine exists. Strep A bacteria are highly diverse, but all produce an essential, abundant, and conserved surface carbohydrate, the Group A Carbohydrate, which contains a rhamnose polysaccharide (RhaPS) backbone. RhaPS is a validated universal vaccine candidate in a glycoconjugate prepared by chemical conjugation of the native carbohydrate to a carrier protein. We engineered the Group A Carbohydrate biosynthesis pathway to enable recombinant production using the industry standard route to couple RhaPS to selected carrier proteins within Escherichia coli cells. The structural integrity of the produced recombinant glycoconjugate vaccines was confirmed by Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry. Purified RhaPS glycoconjugates elicited carbohydrate-specific antibodies in mice and rabbits and bound to the surface of multiple Strep A strains of diverse M-types, confirming the recombinantly produced RhaPS glycoconjugates as valuable vaccine candidates.

Development of a broad-spectrum epitope-based vaccine against Streptococcus pneumoniae

Streptococcus pneumoniae (SPN) is a significant pathogen causing pneumonia and meningitis, particularly in vulnerable populations like children and the elderly. Available pneumonia vaccines have limitations since they only cover particular serotypes and have high production costs. The emergence of antibiotic-resistant SPN strains further underscores the need for a new, cost-effective, broad-spectrum vaccine. Two potential vaccine candidates, CbpA and PspA, were identified, and their B-cell, CTL, and HTL epitopes were predicted and connected with suitable linkers, adjivant and PADRE sequence. The vaccine construct was found to be antigenic, non-toxic, non-allergenic, and soluble. The three-dimensional structure of the vaccine candidate was built and validated. Docking analysis of the vaccine candidate by ClusPro demonstrated robust and stable binding interactions between the MEV and toll-like receptor 4 in both humans and animals. The iMOD server and Amber v.22 tool has verified the stability of the docking complexes. GenScript server confirmed the high efficiency of cloning for the construct and in-silico cloning into the pET28a (+) vector using SnapGene, demonstrating successful translation of the epitope region. Immunological responses were shown to be enhanced by the C-IMMSIM server. This study introduced a strong peptide vaccine candidate that has the potential to contribute to the development of a rapid and cost-effective solution for combating SPN. However, experimental verification is necessary to evaluate the vaccine's effectiveness.

Engineering Escherichia coli for increased Und-P availability leads to material improvements in glycan expression technology

BACKGROUND

Bacterial surface glycans are assembled by glycosyltransferases (GTs) that transfer sugar monomers to long-chained lipid carriers. Most bacteria employ the 55-carbon chain undecaprenyl phosphate (Und-P) to scaffold glycan assembly. The amount of Und-P available for glycan synthesis is thought to be limited by the rate of Und-P synthesis and by competition for Und-P between phosphoglycosyl transferases (PGTs) and GTs that prime glycan assembly (which we collectively refer to as PGT/GTs). While decreasing Und-P availability disrupts glycan synthesis and promotes cell death, less is known about the effects of increased Und-P availability.

RESULTS

To determine if cells can maintain higher Und-P levels, we first reduced intracellular competition for Und-P by deleting all known non-essential PGT/GTs in the Gram-negative bacterium Escherichia coli (hereafter called ΔPGT/GT cells). We then increased the rate of Und-P synthesis in ΔPGT/GT cells by overexpressing the Und-P(P) synthase uppS from a plasmid (puppS). Und-P quantitation revealed that ΔPGT/GT/puppS cells can be induced to maintain 3-fold more Und-P than wild type cells. Next, we determined how increasing Und-P availability affects glycan expression. Interestingly, increasing Und-P availability increased endogenous and recombinant glycan expression. In particular, ΔPGT/GT/puppS cells could be induced to express 7-fold more capsule from Streptococcus pneumoniae serotype 4 than traditional E. coli cells used to express recombinant glycans.

CONCLUSIONS

We demonstrate that the biotechnology standard bacterium E. coli can be engineered to maintain higher levels of Und-P. The results also strongly suggest that Und-P pathways can be engineered to increase the expression of potentially any Und-P-dependent polymer. Given that many bacterial glycans are central to the production of vaccines, diagnostics, and therapeutics, increasing Und-P availability should be a foremost consideration when designing bacterial glycan expression systems.

In silico design of an epitope-based vaccine against PspC in Streptococcus pneumoniae using reverse vaccinology

BACKGROUND

Streptococcus pneumoniae is a major pathogen that poses a significant hazard to global health, causing a variety of infections including pneumonia, meningitis, and sepsis. The emergence of antibiotic-resistant strains has increased the difficulty of conventional antibiotic treatment, highlighting the need for alternative therapies such as multi-epitope vaccines. In this study, immunoinformatics algorithms were used to identify potential vaccine candidates based on the extracellular immunogenic protein Pneumococcal surface protein C (PspC).

METHOD

The protein sequence of PspC was retrieved from NCBI for the development of the multi-epitope vaccine (MEV), and potential B cell and T cell epitopes were identified. Linkers including EAAAK, AAY, and CPGPG were used to connect the epitopes. Through molecular docking, molecular dynamics, and immunological simulation, the affinity between MEV and Toll-like receptors was determined. After cloning the MEV construct into the PET28a ( +) vector, SnapGene was used to achieve expression in Escherichia coli.

RESULT

The constructed MEV was discovered to be stable, non-allergenic, and antigenic. Microscopic interactions between ligand and receptor are confirmed by molecular docking and molecular dynamics simulation. The use of an in-silico cloning approach guarantees the optimal expression and translation efficiency of the vaccine within an expression vector.

CONCLUSION

Our study demonstrates the potential of in silico approaches for designing effective multi-epitope vaccines against S. pneumoniae. The designated vaccine exhibits the required physicochemical, structural, and immunological characteristics of a successful vaccine against SPN. However, laboratory validation is required to confirm the safety and immunogenicity of the proposed vaccine design.

Bacterial glycobiotechnology: A biosynthetic route for the production of biopharmaceutical glycans

The recent advancement in the human glycome and progress in the development of an inclusive network of glycosylation pathways allow the incorporation of suitable machinery for protein modification in non-natural hosts and explore novel opportunities for constructing next-generation tailored glycans and glycoconjugates. Fortunately, the emerging field of bacterial metabolic engineering has enabled the production of tailored biopolymers by harnessing living microbial factories (prokaryotes) as whole-cell biocatalysts. Microbial catalysts offer sophisticated means to develop a variety of valuable polysaccharides in bulk quantities for practical clinical applications. Glycans production through this technique is highly efficient and cost-effective, as it does not involve expensive initial materials. Metabolic glycoengineering primarily focuses on utilizing small metabolite molecules to alter biosynthetic pathways, optimization of cellular processes for glycan and glycoconjugate production, characteristic to a specific organism to produce interest tailored glycans in microbes, using preferably cheap and simple substrate. However, metabolic engineering faces one of the unique challenges, such as the need for an enzyme to catalyze desired substrate conversion when natural native substrates are already present. So, in metabolic engineering, such challenges are evaluated, and different strategies have been developed to overcome them. The generation of glycans and glycoconjugates via metabolic intermediate pathways can still be supported by glycol modeling achieved through metabolic engineering. It is evident that modern glycans engineering requires adoption of improved strain engineering strategies for creating competent glycoprotein expression platforms in bacterial hosts, in the future. These strategies include logically designing and introducing orthogonal glycosylation pathways, identifying metabolic engineering targets at the genome level, and strategically improving pathway performance (for example, through genetic modification of pathway enzymes). Here, we highlight current strategies, applications, and recent progress in metabolic engineering for producing high-value tailored glycans and their applications in biotherapeutics and diagnostics.

Development of a novel glycoengineering platform for the rapid production of conjugate vaccines

Conjugate vaccines produced either by chemical or biologically conjugation have been demonstrated to be safe and efficacious in protection against several deadly bacterial diseases. However, conjugate vaccine assembly and production have several shortcomings which hinders their wider availability. Here, we developed a tool, Mobile-element Assisted Glycoconjugation by Insertion on Chromosome, MAGIC, a novel biotechnological platform that overcomes the limitations of the current conjugate vaccine design method(s). As a model, we focused our design on a leading bioconjugation method using N-oligosaccharyltransferase (OTase), PglB. The installation of MAGIC led to at least twofold increase in glycoconjugate yield via MAGIC when compared to conventional N-OTase based bioconjugation method(s). Then, we improved MAGIC to (a) allow rapid installation of glycoengineering component(s), (b) omit the usage of antibiotics, (c) reduce the dependence on protein induction agents. Furthermore, we show the modularity of the MAGIC platform in performing glycoengineering in bacterial species that are less genetically tractable than the commonly used Escherichia coli. The MAGIC system promises a rapid, robust and versatile method to develop vaccines against serious bacterial pathogens. We anticipate the utility of the MAGIC platform could enhance vaccines production due to its compatibility with virtually any bioconjugation method, thus expanding vaccine biopreparedness toolbox.

Preparation of a Klebsiella pneumoniae conjugate nanovaccine using glycol-engineered Escherichia coli

BACKGROUND

Engineered strains of Escherichia coli have been used to produce bioconjugate vaccines using Protein Glycan Coupling Technology (PGCT). Nanovaccines have also entered the vaccine development arena with advances in nanotechnology and have been significantly developed, but chassis cells for conjugate nanovaccines have not been reported.

RESULTS

To facilitate nanovaccine preparation, a generic recombinant protein (SpyCather4573) was used as the acceptor protein for O-linked glycosyltransferase PglL, and a glycol-engineered Escherichia coli strain with these two key components (SC4573 and PglL) integrated in its genome was developed in this study. The targeted glycoproteins with antigenic polysaccharides produced by our bacterial chassis can be spontaneously bound to proteinous nanocarriers with surface exposed SpyTag in vitro to form conjugate nanovaccines. To improve the yields of the targeted glycoprotein, a series of gene cluster deletion experiments was carried out, and the results showed that the deletion of the yfdGHI gene cluster increased the expression of glycoproteins. Using the updated system, to the best of our knowledge, we report for the first time the successful preparation of an effective Klebsiella pneumoniae O1 conjugate nanovaccine (KPO1-VLP), with antibody titers between 4 and 5 (Log10) after triple immunization and up to 100% protection against virulent strain challenge.

CONCLUSIONS

Our results define a convenient and reliable framework for bacterial glycoprotein vaccine preparation that is flexible and versatile, and the genomic stability of the engineered chassis cells promises a wide range of applications for biosynthetic glycobiology research.

Glycoconjugate vaccines against antimicrobial resistant pathogens

INTRODUCTION

Antimicrobial resistance (AMR) is responsible for the death of millions worldwide and stands as a major threat to our healthcare systems, which are heavily reliant on antibiotics to fight bacterial infections. The development of vaccines against the main pathogens involved is urgently required as prevention remains essential against the rise of AMR.

AREAS COVERED

A systematic research review was conducted on MEDLINE database focusing on the six AMR pathogens defined as ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli), which are considered critical or high priority pathogens by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC). The analysis was intersecated with the terms carbohydrate, glycoconjugate, bioconjugate, glyconanoparticle, and multiple presenting antigen system vaccines.

EXPERT OPINION

Glycoconjugate vaccines have been successful in preventing meningitis and pneumoniae, and there are high expectations that they will play a key role in fighting AMR. We herein discuss the recent technological, preclinical, and clinical advances, as well as the challenges associated with the development of carbohydrate-based vaccines against leading AMR bacteria, with focus on the ESKAPE pathogens. The need of innovative clinical and regulatory approaches to tackle these targets is also highlighted.

30-Minute Highly Multiplexed VaxArray Immunoassay for Pneumococcal Vaccine Antigen Characterization

Pneumonia accounts for over 20% of deaths worldwide in children aged 1 to 5 years, disproportionately affecting lower- and middle-income countries. Effective, highly multivalent pneumococcal vaccines are available to decrease disease burden, with numerous new vaccines currently under development to serve a variety of worldwide markets. However, pneumococcal conjugate vaccines are among the hardest biologics to manufacture and characterize due to their complexity and heterogeneity. Current characterization methods are often inherently singleplex, requiring separate tests for each serotype present. In addition, identity and quantity are often determined with separate methods. We developed the VaxArray pneumococcal assay for applications in identity, quantity, and stability testing of pneumococcal polysaccharide and pneumococcal conjugate vaccines. The VaxArray pneumococcal assay has a time to result of less than 30 min and is an off-the-shelf multiplexed, microarray-based immunoassay kit that can identify and simultaneously quantify 23 pneumococcal polysaccharide serotypes common to many on-market and in-development vaccines. Here, we highlight the potential of the assay for identity testing by showing high reactivity and serotype specificity to a wide variety of native polysaccharides, CRM197-conjugated polysaccharides, and drug product. The assay also has vaccine-relevant lower limits of quantification in the low-to-mid ng/mL range and can be used for accurate quantification even in adjuvanted vaccines. Excellent correlation to the anthrone assay is demonstrated, with VaxArray resulting in significantly improved precision over this antiquated chemical method.

Engineering a suite of E. coli strains for enhanced expression of bacterial polysaccharides and glycoconjugate vaccines

BACKGROUND

Glycoengineering, in the biotechnology workhorse bacterium, Escherichia coli, is a rapidly evolving field, particularly for the production of glycoconjugate vaccine candidates (bioconjugation). Efficient production of glycoconjugates requires the coordinated expression within the bacterial cell of three components: a carrier protein, a glycan antigen and a coupling enzyme, in a timely fashion. Thus, the choice of a suitable E. coli host cell is of paramount importance. Microbial chassis engineering has long been used to improve yields of chemicals and biopolymers, but its application to vaccine production is sparse.

RESULTS

In this study we have engineered a family of 11 E. coli strains by the removal and/or addition of components rationally selected for enhanced expression of Streptococcus pneumoniae capsular polysaccharides with the scope of increasing yield of pneumococcal conjugate vaccines. Importantly, all strains express a detoxified version of endotoxin, a concerning contaminant of therapeutics produced in bacterial cells. The genomic background of each strain was altered using CRISPR in an iterative fashion to generate strains without antibiotic markers or scar sequences.

CONCLUSIONS

Amongst the 11 modified strains generated in this study, E. coli Falcon, Peregrine and Sparrowhawk all showed increased production of S. pneumoniae serotype 4 capsule. Eagle (a strain without enterobacterial common antigen, containing a GalNAc epimerase and PglB expressed from the chromosome) and Sparrowhawk (a strain without enterobacterial common antigen, O-antigen ligase and chain length determinant, containing a GalNAc epimerase and chain length regulators from Streptococcus pneumoniae) respectively produced an AcrA-SP4 conjugate with 4 × and 14 × more glycan than that produced in the base strain, W3110. Beyond their application to the production of pneumococcal vaccine candidates, the bank of 11 new strains will be an invaluable resource for the glycoengineering community.

Production of Vaccines Using Biological Conjugation

The production of conjugate vaccines within an E. coli (Escherichia coli) host provides an inexhaustible supply without the need for culture of pathogenic organisms. The machinery for expression of glycan and acceptor protein, as well as the coupling enzyme, are all housed within the E. coli chassis, meaning that there are no additional steps required for individual purification and chemical conjugation of components. In addition, there are far fewer purification steps necessary to obtain a purified glycoconjugate for use in vaccine testing. Here we describe production and purification of a HIS-tagged Campylobacter jejuni AcrA protein conjugated to Streptococcus pneumoniae serotype 4 capsule.

Bacteria-Based Microdevices for the Oral Delivery of Macromolecules

The oral delivery of macromolecules is quite challenging due to environmental insults and biological barriers encountered along the gastrointestinal (GI) tract. Benefiting from their living characteristics, diverse bacterial species have been engineered as intelligent platforms to deliver various therapeutics. To tackle difficulties in oral delivery, innovative bacteria-based microdevices have been developed by virtue of advancements in synthetic biology and nanotechnology, with aims to overcome the instability and short half-life of macromolecules in the GI tract. In this review, we summarize the main classes of macromolecules that are produced and delivered through the oral ingestion of bacteria and bacterial derivatives. Furtherly, we discuss the engineering strategies and biomedical applications of these living microdevices in disease diagnosis, bioimaging, and treatment. Finally, we highlight the advantages as well as the limitations of these engineered bacteria used as platforms for the oral delivery of macromolecules and also propose their potential for clinical translation. The results summarized in this review article would contribute to the invention of next-generation bacteria-based systems for the oral delivery of macromolecules.

Epitope-targeting platform for broadly protective influenza vaccines

Seasonal influenza vaccines are often ineffective because they elicit strain-specific antibody responses to mutation-prone sites on the hemagglutinin (HA) head. Vaccines that provide long-lasting immunity to conserved epitopes are needed. Recently, we reported a nanoparticle-based vaccine platform produced by solid-phase peptide synthesis (SPPS) for targeting linear and helical protein-based epitopes. Here, we illustrate its potential for building broadly protective influenza vaccines. Targeting known epitopes in the HA stem, neuraminidase (NA) active site, and M2 ectodomain (M2e) conferred 50-75% survival against 5LD50 influenza B and H1N1 challenge; combining stem and M2e antigens increased survival to 90%. Additionally, protein sequence and structural information were employed in tandem to identify alternative epitopes that stimulate greater protection; we report three novel HA and NA sites that are highly conserved in type B viruses. One new target in the HA stem stimulated 100% survival, highlighting the value of this simple epitope discovery strategy. A candidate influenza B vaccine targeting two adjacent HA stem sites led to >104-fold reduction in pulmonary viral load. These studies describe a compelling platform for building vaccines that target conserved influenza epitopes.

Development of an automated platform for the optimal production of glycoconjugate vaccines expressed in Escherichia coli

Protein Glycan Coupling Technology (PGCT) uses purposely modified bacterial cells to produce recombinant glycoconjugate vaccines. This vaccine platform holds great potential in this context, namely due to its modular nature, the simplified production process in comparison to traditional chemical conjugation methods, and its amenability to scaled-up operations. As a result, a considerable reduction in production time and cost is expected, making PGCT-made vaccines a suitable vaccine technology for low-middle income countries, where vaccine coverage remains predominantly low and inconsistent. This work aims to develop an integrated whole-process automated platform for the screening of PGCT-made glycoconjugate vaccine candidates. The successful translation of a bench scale process for glycoconjugate production to a microscale automated setting was achieved. This was integrated with a numerical computational software that allowed hands-free operation and a platform adaptable to biological variation over the course of a production process. Platform robustness was proven with both technical and biological replicates and subsequently the platform was used to screen for the most favourable conditions for production of a pneumococcal serotype 4 vaccine candidate. This work establishes an effective automated platform that enabled the identification of the most suitable E. coli strain and genetic constructs to be used in ongoing early phase research and be further brought into preclinical trials.

A Recombinant Protein SARS-CoV-2 Candidate Vaccine Elicits High-titer Neutralizing Antibodies in Macaques

Background

Vaccines that generate robust and long-lived protective immunity against SARS-CoV-2 infection are urgently required.

Methods

We assessed the potential of vaccine candidates based on the SARS-CoV-2 spike in cynomolgus macaques (M. fascicularis) by examining their ability to generate spike binding antibodies with neutralizing activity. Antigens were derived from two distinct regions of the spike S1 subunit, either the N-terminal domain or an extended C-terminal domain containing the receptor-binding domain and were fused to the human IgG1 Fc domain. Three groups of 2 animals each were immunized with either antigen, alone or in combination. The development of antibody responses was evaluated through 20 weeks post-immunization.

Results

A robust IgG response to the spike protein was detected as early as 2 weeks after immunization with either protein and maintained for over 20 weeks. Sera from animals immunized with antigens derived from the RBD were able to prevent binding of soluble spike proteins to the ACE2 receptor, shown by in vitro binding assays, while sera from animals immunized with the N-terminal domain alone lacked this activity. Crucially, sera from animals immunized with the extended receptor binding domain but not the N-terminal domain had potent neutralizing activity against SARS-CoV-2 pseudotyped virus, with titers in excess of 10,000, greatly exceeding that typically found in convalescent humans. Neutralizing activity persisted for more than 20 weeks.

Conclusions

These data support the utility of spike subunit-based antigens as a vaccine for use in humans.

Biomimetic bacterial and viral-based nanovesicles for drug delivery, theranostics, and vaccine applications

Smart nanocarriers obtained from bacteria and viruses offer excellent biomimetic properties which has led to significant research into the creation of advanced biomimetic materials. Their versatile biomimicry has application as biosensors, biomedical scaffolds, immobilization, diagnostics, and targeted or personalized treatments. The inherent natural traits of biomimetic and bioinspired bacteria- and virus-derived nanovesicles show potential for their use in clinical vaccines and novel therapeutic drug delivery systems. The past few decades have seen significant progress in the bioengineering of bacteria and viruses to manipulate and enhance their therapeutic benefits. From a pharmaceutical perspective, biomimetics enable the safe integration of naturally occurring bacteria and virus particles to achieve high, stable rates of cellular transfection/infection and prolonged circulation times. In addition, biomimetic technologies can overcome safety concerns associated with live-attenuated and inactivated whole bacteria or viruses. In this review, we provide an update on the utilization of bacterial and viral particles as drug delivery systems, theranostic carriers, and vaccine/immunomodulation modalities.

"A recombinant protein SARS-CoV-2 candidate vaccine elicits high-titer neutralizing antibodies in macaques."

Vaccines that generate robust and long-lived protective immunity against SARS-CoV-2 infection are urgently required. We assessed the potential of vaccine candidates based on the SARS-CoV-2 spike in cynomolgus macaques (M. fascicularis) by examining their ability to generate spike binding antibodies with neutralizing activity. Antigens were derived from two distinct regions of the spike S1 subunit, either the N-terminal domain (NTD) or an extended C-terminal domain containing the receptor-binding domain (RBD) and were fused to the human IgG1 Fc domain. Three groups of 2 animals each were immunized with either antigen, alone or in combination. The development of antibody responses was evaluated through 20 weeks post-immunization. A robust IgG response to the spike protein was detected as early as 2 weeks after immunization with either protein and maintained for over 20 weeks. Sera from animals immunized with antigens derived from the RBD were able to prevent binding of soluble spike proteins to the ACE2 receptor, shown by in vitro binding assays, while sera from animals immunized with the NTD alone lacked this activity. Crucially, sera from animals immunized with the RBD but not the NTD had potent neutralizing activity against SARS-CoV-2 pseudotyped virus, with titers in excess of 10,000, greatly exceeding that typically found in convalescent humans. Neutralizing activity persisted for more than 20 weeks. These data support the utility of spike subunit-based antigens as a vaccine for use in humans.

Synthetic Glycobiology: Parts, Systems, and Applications

Protein glycosylation, the attachment of sugars to amino acid side chains, can endow proteins with a wide variety of properties of great interest to the engineering biology community. However, natural glycosylation systems are limited in the diversity of glycoproteins they can synthesize, the scale at which they can be harnessed for biotechnology, and the homogeneity of glycoprotein structures they can produce. Here we provide an overview of the emerging field of synthetic glycobiology, the application of synthetic biology tools and design principles to better understand and engineer glycosylation. Specifically, we focus on how the biosynthetic and analytical tools of synthetic biology have been used to redesign glycosylation systems to obtain defined glycosylation structures on proteins for diverse applications in medicine, materials, and diagnostics. We review the key biological parts available to synthetic biologists interested in engineering glycoproteins to solve compelling problems in glycoscience, describe recent efforts to construct synthetic glycoprotein synthesis systems, and outline exemplary applications as well as new opportunities in this emerging space.

Application of an O-Linked Glycosylation System in Yersinia enterocolitica Serotype O:9 to Generate a New Candidate Vaccine against Brucella abortus

Brucellosis is a major zoonotic public health threat worldwide, causing veterinary morbidity and major economic losses in endemic regions. However, no efficacious brucellosis vaccine is yet available, and live attenuated vaccines commonly used in animals can cause human infection. N- and O-linked glycosylation systems have been successfully developed and exploited for the production of successful bioconjugate vaccines. Here, we applied an O-linked glycosylation system to a low-pathogenicity bacterium, Yersinia enterocolitica serotype O:9 (Y. enterocolitica O:9), which has repeating units of O-antigen polysaccharide (OPS) identical to that of Brucella abortus (B. abortus), to develop a bioconjugate vaccine against Brucella. The glycoprotein we produced was recognized by both anti-B. abortus and anti-Y. enterocolitica O:9 monoclonal antibodies. Three doses of bioconjugate vaccine-elicited B. abortus OPS-specific serum IgG in mice, significantly reducing bacterial loads in the spleen following infection with the B. abortus hypovirulent smooth strain A19. This candidate vaccine mitigated B. abortus infection and prevented severe tissue damage, thereby protecting against lethal challenge with A19. Overall, the results indicated that the bioconjugate vaccine elicited a strong immune response and provided significant protection against brucellosis. The described vaccine preparation strategy is safe and avoids large-scale culture of the highly pathogenic B. abortus.

Glycoconjugate vaccines: some observations on carrier and production methods

Glycoconjugate vaccines use protein carriers to improve the immune response to polysaccharide antigens. The protein component allows the vaccine to interact with T cells, providing a stronger and longer-lasting immune response than a polysaccharide interacting with B cells alone. Whilst in theory the mere presence of a protein component in a vaccine should be sufficient to improve vaccine efficacy, the extent of improvement varies. In the present review, a comparison of the performances of vaccines developed with and without a protein carrier are presented. The usefulness of analytical tools for macromolecular integrity assays, in particular nuclear magnetic resonance, circular dichroism, analytical ultracentrifugation and SEC coupled to multi-angle light scattering (MALS) is indicated. Although we focus mainly on bacterial capsular polysaccharide-protein vaccines, some consideration is also given to research on experimental cancer vaccines using zwitterionic polysaccharides which, unusually for polysaccharides, are able to invoke T-cell responses and have been used in the development of potential all-polysaccharide-based cancer vaccines.A general trend of improved immunogenicity for glycoconjugate vaccines is described. Since the immunogenicity of a vaccine will also depend on carrier protein type and the way in which it has been linked to polysaccharide, the effects of different carrier proteins and production methods are also reviewed. We suggest that, in general, there is no single best carrier for use in glycoconjugate vaccines. This indicates that the choice of carrier protein is optimally made on a case-by-case basis, based on what generates the best immune response and can be produced safely in each individual case.Abbreviations: AUC: analytical ultracentrifugation; BSA: bovine serum albumin; CD: circular dichroism spectroscopy; CPS: capsular polysaccharide; CRM197: Cross Reactive Material 197; DT: diphtheria toxoid; Hib: Haemophilius influenzae type b; MALS: multi-angle light scattering; Men: Neisseria menigitidis; MHC-II: major histocompatibility complex class II; NMR: nuclear magnetic resonance spectroscopy; OMP: outer membrane protein; PRP: polyribosyl ribitol phosphate; PSA: Polysaccharide A1; Sa: Salmonella; St.: Streptococcus; SEC: size exclusion chromatography; Sta: Staphylococcus; TT: tetanus toxoid; ZPS: zwitterionic polysaccharide(s).

Glycoengineering bioconjugate vaccines, therapeutics, and diagnostics in E. coli

The first, general glycosylation pathway in bacteria, the N-linked glycosylation system of Campylobacter jejuni, was discovered two decades ago. Since then, many diverse prokaryotic glycosylation systems have been characterized, including O-linked glycosylation systems that have no homologous counterparts in eukaryotic organisms. Shortly after these discoveries, glycosylation pathways were recombinantly introduced into E. coli creating the field of bacterial glycoengineering. Bacterial glycoengineering is an emerging biotechnological tool that harnesses prokaryotic glycosylation systems for the generation of recombinantly glycosylated proteins using E. coli as a host. Over the last decade, as our understanding of prokaryotic glycosylation systems has advanced, so too has the glycoengineering toolbox. Currently, glycoengineering utilizes two broad approaches to recombinantly glycosylate proteins, both of which can generate N- or O-linkages: oligosaccharyltransferase (OTase)-dependent and OTase-independent. This review discusses the applications of these bacterial glycoengineering techniques as they relate to the development of glycoconjugate vaccines, therapeutic proteins, and diagnostics.

Preparation and preclinical evaluation of two novel Staphylococcus aureus capsular polysaccharide 5 and 8-fusion protein (Hla-MntC-SACOL0723) immunoconjugates

Staphylococcus aureus is one of the most common pathogens in the hospital and the community. The emergence of broad-spectrum antibiotic resistance in S. aureus has made the treatment process more difficult. Therefore, it is obvious that an effective prevention strategy against the pathogen could significantly reduce costs related to care in hospitals. In this report, we describe a simple approach to conjugate S. aureus capsular polysaccharide 5 (CP5) from S. aureus Reynolds strain and 8 (CP8) from S. aureus Becker strain to a fusion protein (Hla-MntC-SACOL0723) and investigation of its bioactivity. The conjugation was done by using ADH (as a bridge) and EDAC (as a coupling agent). The immunoconjugates were characterized by routine polysaccharide/protein contents assays followed by reverse phase chromatography and FTIR spectroscopy. The groups of mice were immunized with conjugate vaccines, capsular polysaccharides, and phosphate-buffered saline (PBS) as a control group. The functional activity of the vaccine candidates was evaluated by ELISA, opsonophagocytosis tests, and determination of bacterial load in challenge study. The results showed that the specific antibody (total IgG) titers raised against conjugate molecules were higher than those of the nonconjugated capsular polysaccharides. The opsonic activity of the conjugate vaccines antisera was significantly higher than polysaccharides alone (58% reduction in the number of bacteria versus 16.3% at 1:2 dilution, p < .05), Further, the conjugate vaccine group had a significant reduction in bacterial load after challenge with S. aureus COL strain cells as compared to the PBS and nonconjugated controls. In conclusion, the immunoconjugates could be developed as a potential vaccine candidate against S. aureus.

Designing self-assembled peptide nanovaccine against Streptococcus pneumoniae: An in silico strategy

Streptococcus pneumoniae is the main cause of diseases such as meningitis, pneumoniae and sepsis, especially in children and old people. Due to costly antibiotic treatment, and increasing resistance of pneumococcus, developing high-efficient protective vaccine against this pathogen is an urgent need. Although the pneumoniae polysaccharide vaccine (PPV) and pneumonia conjugate vaccines (PCV) are the efficient pneumococcal vaccine in children and adult groups, but the serotype replacement of S. pneumoniae strains causes the reduction in efficacy of such vaccines. For overcoming the aforesaid drawbacks epitope-based vaccines are introduced as the relevant alternative. In our previous research, the epitope vaccine was designed based on immunodominant epitopes from PspA, CbpA antigens as cellular stimulants and PhtD, PiuA as humoral stimulants. Because the low immunogenicity is the main disadvantage of epitope vaccine, in the current study, we applied coiled-coil self-assembled structures for developing our vaccine. Recently, self-assembled peptide nanoparticles (SAPNs) have gained much attention in the field of vaccine development due to their multivalency, self-adjuvanticity, biocompatibility, and size similarity to pathogen. In this regard, the final designed vaccine is comprised of cytotoxic T lymphocytes (CTL) epitopes from PspA and CbpA, helper T lymphocytes (HTL) epitopes from PhtD and PiuA, the pentamer and trimmer oligomeric domains form 5-stranded and 3-stranded coiled-coils as self-assembled scaffold, Diphtheria toxoids (DTD) as a universal T-helper, which fused to each other with appropriate linkers. The four different arrangements based on the order of above-mentioned compartments were constructed, and each of them were modeled, and validated to find the 3D structure. The structural, physicochemical, and immunoinformatics analyses of final vaccine construct represented that our vaccine could stimulate potent immune response against S. pneumoniae; however, the potency of that should be approved via various in vivo and in vitro immunological tests.

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Stimulating cellular and especially humoral immunities are essential for protection against Streptococcus Pneumoniae.

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Immunodominant epitopes were selected from highly protective antigens of S. pneumoniae: PspA, CbpA, PiuA, PhtD.

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In order to bypass the low immunogenicity of epitope-based peptide vaccine the self-assembled motifs, coiled-coil structure, was applied as the vaccine scaffold.

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The structural, physicochemical, and immunoinformatics results indicate that the designed vaccine can incite strong immune response against S. pneumoniae.

Recent advances in the production of recombinant glycoconjugate vaccines

Glycoconjugate vaccines against bacteria are one of the success stories of modern medicine and have led to a significant reduction in the global occurrence of bacterial meningitis and pneumonia. Glycoconjugate vaccines are produced by covalently linking a bacterial polysaccharide (usually capsule, or more recently O-antigen), to a carrier protein. Given the success of glycoconjugate vaccines, it is surprising that to date only vaccines against Haemophilus influenzae type b, Neisseria meningitis and Streptococcus pneumoniae have been fully licenced. This is set to change through the glycoengineering of recombinant vaccines in bacteria, such as Escherichia coli, that act as mini factories for the production of an inexhaustible and renewable supply of pure vaccine product. The recombinant process, termed Protein Glycan Coupling Technology (PGCT) or bioconjugation, offers a low-cost option for the production of pure glycoconjugate vaccines, with the in-built flexibility of adding different glycan/protein combinations for custom made vaccines. Numerous vaccine candidates have now been made using PGCT, which include those improving existing licenced vaccines (e.g., pneumococcal), entirely new vaccines for both Gram-positive and Gram-negative bacteria, and (because of the low production costs) veterinary pathogens. Given the continued threat of antimicrobial resistance and the potential peril of bioterrorist agents, the production of new glycoconjugate vaccines against old and new bacterial foes is particularly timely. In this review, we will outline the component parts of bacterial PGCT, including recent advances, the advantages and limitations of the technology, and future applications and perspectives.

A platform for glycoengineering a polyvalent pneumococcal bioconjugate vaccine using E. coli as a host

Chemical synthesis of conjugate vaccines, consisting of a polysaccharide linked to a protein, can be technically challenging, and in vivo bacterial conjugations (bioconjugations) have emerged as manufacturing alternatives. Bioconjugation relies upon an oligosaccharyltransferase to attach polysaccharides to proteins, but currently employed enzymes are not suitable for the generation of conjugate vaccines when the polysaccharides contain glucose at the reducing end, which is the case for ~75% of Streptococcus pneumoniae capsules. Here, we use an O-linking oligosaccharyltransferase to generate a polyvalent pneumococcal bioconjugate vaccine with polysaccharides containing glucose at their reducing end. In addition, we show that different vaccine carrier proteins can be glycosylated using this system. Pneumococcal bioconjugates are immunogenic, protective and rapidly produced within E. coli using recombinant techniques. These proof-of-principle experiments establish a platform to overcome limitations of other conjugating enzymes enabling the development of bioconjugate vaccines for many important human and animal pathogens.

Bioconjugation is a promising process to manufacture conjugate vaccines, but currently employed enzymes cannot generate the full spectrum of bacterial glycoproteins. Here, the authors use an O-linking oligosaccharyltransferase to generate a polyvalent pneumococcal bioconjugate vaccine with polysaccharides containing glucose at their reducing end.