Publications by authors named "Davide Oldrini"

11 Publications

  • Page 1 of 1

Conformational and Immunogenicity Studies of the Serogroup 6 O-Antigen: The Effect of O-Acetylation.

Vaccines (Basel) 2021 Apr 27;9(5). Epub 2021 Apr 27.

Department of Computer Science, University of Cape Town, Rondebosch 7701, South Africa.

The pathogenic bacterium is a leading cause of diarrheal disease and mortality, disproportionately affecting young children in low-income countries. The increasing prevalence of antibiotic resistance in necessitates an effective vaccine, for which the bacterial lipopolysaccharide O-antigen is the primary target. serotype 6 has been proposed as a multivalent vaccine component to ensure broad protection against . We have previously explored the conformations of O-antigens from serogroups Y, 2, 3, and 5 that share a common saccharide backbone (serotype Y). Here we consider serogroup 6, which is of particular interest because of an altered backbone repeat unit with non-stoichiometric O-acetylation, the antigenic and immunogenic importance of which have yet to be established. Our simulations show significant conformational changes in serogroup 6 relative to the serotype Y backbone. We further find that O-acetylation has little effect on conformation and hence may not be essential for the antigenicity of serotype 6. This is corroborated by an in vivo study in mice, using Generalized Modules for Membrane Antigens (GMMA) as O-antigen delivery systems, that shows that O-acetylation does not have an impact on the immune response elicited by the serotype 6 O-antigen.
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http://dx.doi.org/10.3390/vaccines9050432DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8144980PMC
April 2021

Stability of Outer Membrane Vesicles-Based Vaccines, Identifying the Most Appropriate Methods to Detect Changes in Vaccine Potency.

Vaccines (Basel) 2021 Mar 6;9(3). Epub 2021 Mar 6.

GSK Vaccines Institute for Global Health (GVGH) S.r.l., Via Fiorentina 1, 53100 Siena, Italy.

Ensuring the stability of vaccines is crucial to successfully performing global immunization programs. Outer Membrane Vesicles (OMV) are receiving great attention as vaccine platforms. OMV are complex molecules and few data have been collected so far on their stability. OMV produced by bacteria, genetically modified to increase their spontaneous release, simplifying their production, are also known as Generalized Modules for Membrane Antigens (GMMA). We have performed accelerated stability studies on GMMA from different pathogens and verified the ability of physico-chemical and immunological methods to detect possible changes. High-temperature conditions (100 °C for 40 min) did not affect GMMA stability and immunogenicity in mice, in contrast to the effect of milder temperatures for a longer period of time (37 °C or 50 °C for 4 weeks). We identified critical quality attributes to monitor during stability assessment that could impact vaccine efficacy. In particular, specific recognition of antigens by monoclonal antibodies through competitive ELISA assays may replace in vivo tests for the potency assessment of GMMA-based vaccines.
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http://dx.doi.org/10.3390/vaccines9030229DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998687PMC
March 2021

Structure-Guided Design of a Group B Streptococcus Type III Synthetic Glycan-Conjugate Vaccine.

Chemistry 2020 Jun 11;26(31):6944. Epub 2020 May 11.

Research Center, GlaxoSmithKline Plc, Via Fiorentina 1, 53100, Siena, Italy.

Invited for the cover of this issue is the group of Roberto Adamo at GlaxoSmithKline Research Center, Siena, and colleagues at The University of the Basque Country and Basque Research Technology Alliance. The image depicts a tactical plan with the different elements of the research as part of the team. Read the full text of the article at 10.1002/chem.202000284.
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http://dx.doi.org/10.1002/chem.202002016DOI Listing
June 2020

Structure-Guided Design of a Group B Streptococcus Type III Synthetic Glycan-Conjugate Vaccine.

Chemistry 2020 Jun 1;26(31):7018-7025. Epub 2020 Apr 1.

Research Center, GlaxoSmithKline Plc, Via Fiorentina 1, 53100, Siena, Italy.

Identification of glycan functional epitopes is of paramount importance for rational design of glycoconjugate vaccines. We recently mapped the structural epitope of the capsular polysaccharide from type III Group B Streptococcus (GBSIII), a major cause of invasive disease in newborns, by using a dimer fragment (composed of two pentasaccharide repeating units) obtained by depolymerization complexed with a protective mAb. Although reported data had suggested a highly complex epitope contained in a helical structure composed of more than four repeating units, we showed that such dimer conjugated to a carrier protein with a proper glycosylation degree elicited functional antibodies comparably to the full-length conjugated polysaccharide. Here, starting from the X-ray crystallographic structure of the polysaccharide fragment-mAb complex, we synthesized a hexasaccharide comprising exclusively the relevant positions involved in binding. Combining competitive surface plasmon resonance and saturation transfer difference NMR spectroscopy as well as in-silico modeling, we demonstrated that this synthetic glycan was recognized by the mAb similarly to the dimer. The hexasaccharide conjugated to CRM , a mutant of diphtheria toxin, elicited a robust functional immune response that was not inferior to the polysaccharide conjugate, indicating that it may suffice as a vaccine antigen. This is the first evidence of an X-ray crystallography-guided design of a synthetic carbohydrate-based conjugate vaccine.
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http://dx.doi.org/10.1002/chem.202000284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7317837PMC
June 2020

Regioselective Glycosylation Strategies for the Synthesis of Group Ia and Ib Streptococcus Related Glycans Enable Elucidating Unique Conformations of the Capsular Polysaccharides.

Chemistry 2019 Dec 4;25(71):16277-16287. Epub 2019 Nov 4.

GSK, Via Fiorentina 1, 53100, Siena, Italy.

Group B Streptococcus serotypes Ia and Ib capsular polysaccharides are key targets for vaccine development. In spite of their immunospecifity these polysaccharides share high structural similarity. Both are composed of the same monosaccharide residues and differ only in the connection of the Neu5Acα2-3Gal side chain to the GlcNAc unit, which is a β1-4 linkage in serotype Ia and a β1-3 linkage in serotype Ib. The development of efficient regioselective routes for GlcNAcβ1-3[Glcβ1-4]Gal synthons is described, which give access to different group B Streptococcus (GBS) Ia and Ib repeating unit frameshifts. These glycans were used to probe the conformation and molecular dynamics of the two polysaccharides, highlighting the different presentation of the protruding Neu5Acα2-3Gal moieties on the polysaccharide backbones and a higher flexibility of Ib polymer relative to Ia, which can impact epitope exposure.
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http://dx.doi.org/10.1002/chem.201903527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6972993PMC
December 2019

A New Family of Capsule Polymerases Generates Teichoic Acid-Like Capsule Polymers in Gram-Negative Pathogens.

mBio 2018 05 29;9(3). Epub 2018 May 29.

Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany

Group 2 capsule polymers represent crucial virulence factors of Gram-negative pathogenic bacteria. They are synthesized by enzymes called capsule polymerases. In this report, we describe a new family of polymerases that combine glycosyltransferase and hexose- and polyol-phosphate transferase activity to generate complex poly(oligosaccharide phosphate) and poly(glycosylpolyol phosphate) polymers, the latter of which display similarity to wall teichoic acid (WTA), a cell wall component of Gram-positive bacteria. Using modeling and multiple-sequence alignment, we showed homology between the predicted polymerase domains and WTA type I biosynthesis enzymes, creating a link between Gram-negative and Gram-positive cell wall biosynthesis processes. The polymerases of the new family are highly abundant and found in a variety of capsule-expressing pathogens such as , , , , and with both human and animal hosts. Five representative candidates were purified, their activities were confirmed using nuclear magnetic resonance (NMR) spectroscopy, and their predicted folds were validated by site-directed mutagenesis. Bacterial capsules play an important role in the interaction between a pathogen and the immune system of its host. During the last decade, capsule polymerases have become attractive tools for the production of capsule polymers applied as antigens in glycoconjugate vaccine formulations. Conventional production of glycoconjugate vaccines requires the cultivation of the pathogen and thus the highest biosafety standards, leading to tremendous costs. With regard to animal husbandry, where vaccines could avoid the extensive use of antibiotics, conventional production is not sufficiently cost-effective. In contrast, enzymatic synthesis of capsule polymers is pathogen-free and fast, offers high stereo- and regioselectivity, and works with high efficacy. The new capsule polymerase family described here vastly increases the toolbox of enzymes available for biotechnology purposes. Representatives are abundantly found in human pathogens but also in animal pathogens, paving the way for the exploitation of polymerases for the development of a new generation of vaccines for animal husbandry.
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http://dx.doi.org/10.1128/mBio.00641-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5974469PMC
May 2018

Combined Chemical Synthesis and Tailored Enzymatic Elongation Provide Fully Synthetic and Conjugation-Ready Neisseria meningitidis Serogroup X Vaccine Antigens.

ACS Chem Biol 2018 04 1;13(4):984-994. Epub 2018 Mar 1.

GSK , Via Fiorentina 1 , 53100 Siena , Italy.

Studies on the polymerization mode of Neisseria meningitidis serogroup X capsular polymerase CsxA recently identified a truncated construct that can be immobilized and used for length controlled on-column production of oligosaccharides. Here, we combined the use of a synthetic acceptor bearing an appendix for carrier protein conjugation and the on-column process to a novel chemo-enzymatic strategy. After protein coupling of the size optimized oligosaccharide produced by the one-pot elongation procedure, we obtained a more homogeneous glycoconjugate compared to the one previously described starting from the natural polysaccharide. Mice immunized with the conjugated fully synthetic oligomer elicited functional antibodies comparable to controls immunized with the current benchmark MenX glycoconjugates prepared from the natural capsule polymer or from fragments of it enzymatically elongated. This pathogen-free technology allows the fast total in vitro construction of predefined bacterial polysaccharide fragments. Compared to conventional synthetic protocols, the procedure is more expeditious and drastically reduces the number of purification steps to achieve the oligomers. Furthermore, the presence of a linker for conjugation in the synthetic acceptor minimizes manipulations on the enzymatically produced glycan prior to protein conjugation. This approach enriches the methods for fast construction of complex bacterial carbohydrates.
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http://dx.doi.org/10.1021/acschembio.7b01057DOI Listing
April 2018

An efficient cell free enzyme-based total synthesis of a meningococcal vaccine candidate.

NPJ Vaccines 2016 15;1:16017. Epub 2016 Nov 15.

Institute for Cellular Chemistry, Hannover Medical School, Hannover, Germany.

Invasive meningococcal disease (IMD) is a global health problem and vaccination has proven the most effective way of disease control. serogroup X (X) is an emerging threat in the African sub-Saharan meningitis belt, but no vaccine is available today. Leading vaccines against are glycoconjugates, in which capsular polysaccharides isolated from large-scale pathogen cultures are conjugated to adjuvant proteins. Though safe and efficacious even in infants, high costs and biohazard associated with the production limit abundant application of glycoconjugate vaccines particularly in the most afflicted nations. An existing X vaccine candidate (CPSXn-CRM) produced by established protocols from X capsule polysaccharide (CPSX) has been shown to elicit high bactericidal immunoglobulin G titres in mice. Here we describe the scalable synthesis of CPSXiv from chemically pure precursors by the use of recombinant X capsule polymerase. Application of the described coupling chemistry gives CPSXiv-CRM, which in mouse vaccination experiments behaves identical to the benchmark CPSXn-CRM. Excluding any biohazards, this novel process represents a paradigm shift in vaccine production and a premise towards vaccine manufacturing in emerging economies.
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http://dx.doi.org/10.1038/npjvaccines.2016.17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5707881PMC
November 2016

Oxetane Grafts Installed Site-Selectively on Native Disulfides to Enhance Protein Stability and Activity In Vivo.

Angew Chem Int Ed Engl 2017 11 20;56(47):14963-14967. Epub 2017 Oct 20.

Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, UK.

A four-membered oxygen ring (oxetane) can be readily grafted into native peptides and proteins through site-selective bis-alkylation of cysteine residues present as disulfides under mild and biocompatible conditions. The selective installation of the oxetane graft enhances stability and activity, as demonstrated for a range of biologically relevant cyclic peptides, including somatostatin, proteins, and antibodies, such as a Fab arm of the antibody Herceptin and a designed antibody DesAb-Aβ against the human Amyloid-β peptide. Oxetane grafting of the genetically detoxified diphtheria toxin CRM improves significantly the immunogenicity of this protein in mice, which illustrates the general utility of this strategy to modulate the stability and biological activity of therapeutic proteins containing disulfides in their structures.
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http://dx.doi.org/10.1002/anie.201708847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5698723PMC
November 2017

Structure of a protective epitope of group B type III capsular polysaccharide.

Proc Natl Acad Sci U S A 2017 05 24;114(19):5017-5022. Epub 2017 Apr 24.

GSK Vaccines, 53100 Siena, Italy

Despite substantial progress in the prevention of group B (GBS) disease with the introduction of intrapartum antibiotic prophylaxis, this pathogen remains a leading cause of neonatal infection. Capsular polysaccharide conjugate vaccines have been tested in phase I/II clinical studies, showing promise for further development. Mapping of epitopes recognized by protective antibodies is crucial for understanding the mechanism of action of vaccines and for enabling antigen design. In this study, we report the structure of the epitope recognized by a monoclonal antibody with opsonophagocytic activity and representative of the protective response against type III GBS polysaccharide. The structure and the atomic-level interactions were determined by saturation transfer difference (STD)-NMR and X-ray crystallography using oligosaccharides obtained by synthetic and depolymerization procedures. The GBS PSIII epitope is made by six sugars. Four of them derive from two adjacent repeating units of the PSIII backbone and two of them from the branched galactose-sialic acid disaccharide contained in this sequence. The sialic acid residue establishes direct binding interactions with the functional antibody. The crystal structure provides insight into the molecular basis of antibody-carbohydrate interactions and confirms that the conformational epitope is not required for antigen recognition. Understanding the structural basis of immune recognition of capsular polysaccharide epitopes can aid in the design of novel glycoconjugate vaccines.
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http://dx.doi.org/10.1073/pnas.1701885114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441712PMC
May 2017