O:2-CRM197 Conjugates against Salmonella Paratyphi A

Micoli, Francesca; Rondini, Simona; Gavini, Massimiliano; Lanzilao, Luisa; Medaglini, Donata; Saul, Allan; Martin, Laura B.

doi:10.1371/journal.pone.0047039

Cited by 75 publications

(82 citation statements)

References 37 publications

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“…A similar chemistry was evaluated where the reductive amination was conducted using adipic acid dihydrazide (ADH) followed also in this case by derivatization with SIDEA, thus resulting in a longer linker (Fig. 1C) (39). The use of more reactive ADH molecule resulted in shorter reaction time of the first step (from 5 d to 1 h) and higher derivatization yield: 40% of MenX chains derivatized with NH 4 OAc, compared with 81% using ADH, as quantified by 2,4,6-trinitrobenzenesulfonic acid (TNBS) colorimetric method.…”

Section: Resultsmentioning

confidence: 99%

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Development of a glycoconjugate vaccine to prevent meningitis in Africa caused by meningococcal serogroup X

Micoli

Romano

Tontini

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Neisseria meningitidis is a major cause of bacterial meningitis worldwide, especially in the African meningitis belt, and has a high associated mortality. The meningococcal serogroups A, W, and X have been responsible for epidemics and almost all cases of meningococcal meningitis in the meningitis belt over the past 12 y. Currently no vaccine is available against meningococcal X (MenX). Because the development of a new vaccine through to licensure takes many years, this leaves Africa vulnerable to new epidemics of MenX meningitis at a time when the epidemiology of meningococcal meningitis on the continent is changing rapidly, following the recent introduction of a glycoconjugate vaccine against serogroup A. Here, we report the development of candidate glycoconjugate vaccines against MenX and preclinical data from their use in animal studies. Following optimization of growth conditions of our seed MenX strain for polysaccharide (PS) production, a scalable purification process was developed yielding high amounts of pure MenX PS. Different glycoconjugates were synthesized by coupling MenX oligosaccharides of varying chain length to CRM 197 as carrier protein. Analytical methods were developed for in-process control and determination of purity and consistency of the vaccines. All conjugates induced high anti-MenX PS IgG titers in mice. Antibodies were strongly bactericidal against African MenX isolates. These findings support the further development of glycoconjugate vaccines against MenX and their assessment in clinical trials to produce a vaccine against the one cause of epidemic meningococcal meningitis that currently cannot be prevented by available vaccines.

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Section: Resultsmentioning

confidence: 99%

“…The use of ADH as a more reactive linker (Fig. 1C) (39) increased the yield of this first step and reduced the reaction time. Working with longer OS, a completely different chemistry was required (Fig.…”

Section: Discussionmentioning

confidence: 99%

Development of a glycoconjugate vaccine to prevent meningitis in Africa caused by meningococcal serogroup X

Micoli

Romano

Tontini

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…All OAg preparations were characterized using a range of analytical methods (27,28): (i) phenol sulfuric acid assay for total sugar quantification (32); (ii) micro-BCA for protein quantification (using bovine serum albumin as a reference according to the manufacturer's instructions [Thermo Scientific]); (iii) UV spectroscopy for nucleic acid content (assuming that a nucleic acid concentration of 50 g/ml gives an OD 260 of 1); (iv) chromogenic kinetic LAL (Limulus amebocyte lysate) for endotoxin level (Charles River Endosafe-PTS instrument); (v) sizeexclusion high-pressure liquid chromatography (HPLC-SEC; differential refractive index [dRI] detection) to estimate molecular size distribution of OAg populations; (vi) high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) for sugar composition analysis; (vii) semicarbazide/HPLC-SEC method for KDO sugar quantification; and (viii) proton nuclear magnetic resonance ( 1 H NMR) analysis to identify OAg samples and quantify O-acetylation level.…”

Section: Methodsmentioning

confidence: 99%

“…OAg was extracted by acetic acid hydrolysis directly from the bacterial pellet, a process that removes the toxic lipid A by cleaving the labile bond between lipid A and the KDO sugar at the end of the core region (27). The KDO was used for covalent linkage of OAg to CRM 197 through a conjugation chemistry that does not modify the structure of the polysaccharide chain (28). conjugates varied with regard to (i) OAg source, with use of three Typhimurium strains (D23580, NVGH1792, and LT2) producing OAg with specific structural differences, (ii) OAg molecular weight (MW) distribution, with conjugates containing OAg populations of different chain length, and (iii) OAg/CRM 197 ratio.…”

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confidence: 99%

Design of Glycoconjugate Vaccines against Invasive African Salmonella enterica Serovar Typhimurium

et al. 2015

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dNontyphoidal salmonellae, particularly Salmonella enterica serovar Typhimurium, are a major cause of invasive disease in Africa, affecting mainly young children and HIV-infected individuals. Glycoconjugate vaccines provide a safe and reliable strategy against invasive polysaccharide-encapsulated pathogens, and lipopolysaccharide (LPS) is a target of protective immune responses. With the aim of designing an effective vaccine against S. Typhimurium, we have synthesized different glycoconjugates, by linking O-antigen and core sugars (OAg) of LPS to the nontoxic mutant of diphtheria toxin (CRM 197 ). The OAg-CRM 197 conjugates varied in (i) OAg source, with three S. Typhimurium strains used for OAg extraction, producing OAg with differences in structural specificities, (ii) OAg chain length, and (iii) OAg/CRM 197 ratio. All glycoconjugates were compared for immunogenicity and ability to induce serum bactericidal activity in mice. In vivo enhancement of bacterial clearance was assessed for a selected S. Typhimurium glycoconjugate by challenge with live Salmonella. We found that the largest anti-OAg antibody responses were elicited by (i) vaccines synthesized from OAg with the highest glucosylation levels, (ii) OAg composed of mixed-or medium-molecular-weight populations, and (iii) a lower OAg/CRM 197 ratio. In addition, we found that bactericidal activity can be influenced by S. Typhimurium OAg strain, most likely as a result of differences in OAg O-acetylation and glucosylation. Finally, we confirmed that mice immunized with the selected OAg-conjugate were protected against S. Typhimurium colonization of the spleen and liver. In conclusion, our findings indicate that differences in the design of OAg-based glycoconjugate vaccines against invasive African S. Typhimurium can have profound effects on immunogenicity and therefore optimal vaccine design requires careful consideration.

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“…Only one Salmonella Paratyphi A vaccine, CVD 1902, has been evaluated in a phase 1 clinical trial (registered at ClinicalTrials.gov [https: //clinicaltrials.gov] under registration number NCT01129453) (K. Kotloff, personal communication), and it was found to be safe. Several conjugate vaccine approaches are also under investigation in preclinical studies (23)(24)(25).…”

Section: Salmonella Vaccinesmentioning

confidence: 99%

Animal Models for Salmonellosis: Applications in Vaccine Research

Higginson

Simon

Tennant

2016

Clin Vaccine Immunol

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Salmonellosis remains an important cause of human disease worldwide. While there are several licensed vaccines for Salmonella enterica serovar Typhi, these vaccines are generally ineffective against other Salmonella serovars. Vaccines that target paratyphoid and nontyphoidal Salmonella serovars are very much in need. Preclinical evaluation of candidate vaccines is highly dependent on the availability of appropriate scientific tools, particularly animal models. Many different animal models exist for various Salmonella serovars, from whole-animal models to smaller models, such as those recently established in insects. Here, we discuss various mouse, rat, rabbit, calf, primate, and insect models for Salmonella infection, all of which have their place in research. However, choosing the right model is imperative in selecting the best vaccine candidates for further clinical testing. In this minireview, we summarize the various animal models that are used to assess salmonellosis, highlight some of the advantages and disadvantages of each, and discuss their value in vaccine development.A nimal models are indispensable tools for assessing candidate vaccines, with preclinical animal safety, immunogenicity, and efficacy data being prerequisite for regulatory agencies such as the U.S. Food and Drug Administration (FDA) prior to undertaking early-stage clinical trials. However, not all animal models are created equal. While some models are highly robust and closely mimic clinical infection, others are contrived and far removed from clinical relevance. Choosing the right animal model for the vaccine under investigation is imperative in determining its safety and/or effectiveness.Salmonella spp. are often used as model organisms to study bacterial pathogenesis and host-microbe interactions, due to the ability of certain Salmonella serovars to readily infect animals. As such, there are a myriad of animal models available to vaccine developers. These range from colonization or lethality models to those involving complex surgical techniques (Table 1). The choice of model is often related not only to relevance but also cost, ethics, housing requirements, and the availability of appropriate technical expertise. While most researchers utilize one model or another, integration of data from multiple animal models can provide a more complete understanding of the safety of a candidate vaccine and/or predict how a potential vaccine may perform in humans. In this minireview, we provide background on Salmonella clinical syndromes and pathogenesis and then summarize the various animal models that have been used for Salmonella vaccine research. We include a brief discussion of the technical aspects, advantages, and limitations of each model, followed by a review of the literature surrounding its use in vaccine evaluation. While there has been considerable development for veterinary Salmonella vaccines, here we will focus solely on vaccines and models for human salmonellosis.

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O:2-CRM197 Conjugates against Salmonella Paratyphi A

Cited by 75 publications

References 37 publications

Development of a glycoconjugate vaccine to prevent meningitis in Africa caused by meningococcal serogroup X

Development of a glycoconjugate vaccine to prevent meningitis in Africa caused by meningococcal serogroup X

Design of Glycoconjugate Vaccines against Invasive African Salmonella enterica Serovar Typhimurium

Animal Models for Salmonellosis: Applications in Vaccine Research

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