Publications by authors named "Vanessa Arato"

8 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

Prophylaxis and Treatment against : Current Insights on This Emerging Anti-Microbial Resistant Global Threat.

Int J Mol Sci 2021 Apr 14;22(8). Epub 2021 Apr 14.

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

(Kp) is an opportunistic pathogen and the leading cause of healthcare-associated infections, mostly affecting subjects with compromised immune systems or suffering from concurrent bacterial infections. However, the dramatic increase in hypervirulent strains and the emergence of new multidrug-resistant clones resulted in Kp occurrence among previously healthy people and in increased morbidity and mortality, including neonatal sepsis and death across low- and middle-income countries. As a consequence, carbapenem-resistant and extended spectrum β-lactamase-producing Kp have been prioritized as a critical anti-microbial resistance threat by the World Health Organization and this has renewed the interest of the scientific community in developing a vaccine as well as treatments alternative to the now ineffective antibiotics. Capsule polysaccharide is the most important virulence factor of Kp and plays major roles in the pathogenesis but its high variability (more than 100 different types have been reported) makes the identification of a universal treatment or prevention strategy very challenging. However, less variable virulence factors such as the O-Antigen, outer membrane proteins as fimbriae and siderophores might also be key players in the fight against Kp infections. Here, we review elements of the current status of the epidemiology and the molecular pathogenesis of Kp and explore specific bacterial antigens as potential targets for both prophylactic and therapeutic solutions.
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http://dx.doi.org/10.3390/ijms22084042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8070759PMC
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

Effect of O-Antigen Chain Length Regulation on the Immunogenicity of and Generalized Modules for Membrane Antigens (GMMA).

Int J Mol Sci 2021 Jan 28;22(3). Epub 2021 Jan 28.

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

Recently, generalized modules for membrane antigens (GMMA) technology has been proposed as an alternative approach to traditional glycoconjugate vaccines for O-antigen delivery. Saccharide length is a well-known parameter that can impact the immune response induced by glycoconjugates both in terms of magnitude and quality. However, the criticality of O-antigen length on the immune response induced by GMMA-based vaccines has not been fully elucidated. Here, and GMMA-producing strains were further mutated in order to display homogeneous polysaccharide populations of different sizes on a GMMA surface. Resulting GMMA were compared in mice immunization studies. Athymic nude mice were also used to investigate the involvement of T-cells in the immune response elicited. In contrast with what has been reported for traditional glycoconjugate vaccines and independent of the pathogen and the sugar structural characteristics, O-antigen length did not result in being a critical parameter for GMMA immunogenicity. This work supports the identification of critical quality attributes to optimize GMMA vaccine design and improve vaccine efficacy and gives insights on the nature of the immune response induced by GMMA.
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http://dx.doi.org/10.3390/ijms22031309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7865430PMC
January 2021

Dual role of the colonization factor CD2831 in Clostridium difficile pathogenesis.

Sci Rep 2019 04 3;9(1):5554. Epub 2019 Apr 3.

Glaxo Smith Kline Vaccines, Via Fiorentina 1, 53100, Siena, Italy.

Clostridium difficile is a Gram-positive, anaerobic bacterium and the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis. C. difficile modulates its transition from a motile to a sessile lifestyle through a mechanism of riboswitches regulated by cyclic diguanosine monophosphate (c-di-GMP). Previously described as a sortase substrate positively regulated by c-di-GMP, CD2831 was predicted to be a collagen-binding protein and thus potentially involved in sessility. By overexpressing CD2831 in C. difficile and heterologously expressing it on the surface of Lactococcus lactis, here we further demonstrated that CD2831 is a collagen-binding protein, able to bind to immobilized collagen types I, III and V as well as native collagen produced by human fibroblasts. We also observed that the overexpression of CD2831 raises the ability to form biofilm on abiotic surface in both C. difficile and L. lactis. Notably, we showed that CD2831 binds to the collagen-like domain of the human complement component C1q, suggesting a role in preventing complement cascade activation via the classical pathway. This functional characterization places CD2831 in the Microbial Surface Components Recognizing Adhesive Matrix Molecule (MSCRAMMs) family, a class of virulence factors with a dual role in adhesion to collagen-rich tissues and in host immune evasion by binding to human complement components.
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http://dx.doi.org/10.1038/s41598-019-42000-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447587PMC
April 2019

Outer Membrane Vesicles (OMV)-based and Proteomics-driven Antigen Selection Identifies Novel Factors Contributing to Adhesion to Epithelial Cells.

Mol Cell Proteomics 2018 02 4;17(2):205-215. Epub 2017 Dec 4.

From the ‡GSK Vaccines, Siena, Italy

Despite high vaccination coverage world-wide, whooping cough, a highly contagious disease caused by is recently increasing in occurrence suggesting that novel vaccine formulations targeted at the prevention of colonization and transmission should be investigated. To identify new candidates for inclusion in the acellular formulation, we used spontaneously released outer membrane vesicles (OMV) as a potential source of key adhesins. The enrichment of Bvg+ OMV with adhesins and the ability of anti-OMV serum to inhibit the adhesion of to lung epithelial cells were demonstrated. We employed a proteomic approach to identify the differentially expressed proteins in OMV purified from bacteria in the Bvg+ and Bvg- virulence phases, thus comparing the outer membrane protein pattern of this pathogen in its virulent or avirulent state. Six of the most abundant outer membrane proteins were selected as candidates to be evaluated for their adhesive properties and vaccine potential. We generated strains singularly expressing the selected proteins and assessed their ability to adhere to lung epithelial cells Four out of the selected proteins conferred adhesive ability to Three of the candidates were specifically detected by anti-OMV mouse serum suggesting that these proteins are immunogenic antigens able to elicit an antibody response when displayed on the OMV. Anti-OMV serum was able to inhibit only BrkA-expressing adhesion to lung epithelial cells. Finally, stand-alone immunization of mice with recombinant BrkA resulted in significant protection against infection of the lower respiratory tract after challenge with Taken together, these data support the inclusion of BrkA and possibly further adhesins to the current acellular pertussis vaccines to improve the impact of vaccination on the bacterial clearance.
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http://dx.doi.org/10.1074/mcp.RA117.000045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795387PMC
February 2018

Physiopathological roles of spontaneously released outer membrane vesicles of Bordetella pertussis.

Future Microbiol 2017 11 5;12:1247-1259. Epub 2017 Oct 5.

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

Aim: Bordetella pertussis has been shown to release outer membrane vesicles (OMV) both in vitro and in vivo but little is known about their biological role during the initial phases of B. pertussis infection of the airways.

Results: We have demonstrated that OMV are released by B. pertussis in a human ciliated-airway cell model and purified vesicles can interact with host cells. Binding and uptake are strictly Bvg-regulated and OMV-associated pertussis toxin contributes to host-cell intoxication. Furthermore, we have shown that OMV act as iron-delivery systems complementing the B. pertussis growth defect in iron-limiting conditions.

Conclusion: We have proved that OMV play different roles in B. pertussis physiopathology and we opened new perspectives to be further investigated.
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http://dx.doi.org/10.2217/fmb-2017-0064DOI Listing
November 2017

A novel high-throughput assay to quantify the vaccine-induced inhibition of Bordetella pertussis adhesion to airway epithelia.

BMC Microbiol 2016 09 15;16:215. Epub 2016 Sep 15.

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

Background: Pertussis or whooping cough is an acute respiratory illness caused by the Gram-negative pathogen Bordetella pertussis. Despite high vaccination coverage whooping cough is currently re-emerging in many developed countries. Although the causes of pertussis resurgence are matter of debate, emerging evidences suggest that acellular vaccines efficiently protect against the hallmark symptoms of pertussis disease but fail to prevent colonization. This presumably impacts on increased risk of bacterial transmission and consequent spread throughout the population. These evidences suggest that improved vaccines may be required for efficient bacterial clearance in the upper respiratory tract. Consequently, there is a need for novel bioassays to evaluate at pre-clinical or clinical level the impact of different vaccines on B. pertussis colonization.

Results: We developed a high-throughput bacterial adhesion inhibition (BAI) assay based on human respiratory cell lines and on live bacteria chemically conjugated to a fluorescent dye. Employing A549 cells as model, we evaluated the impact of antibodies elicited by acellular (aP) and whole cell (wP) vaccines on B. pertussis adhesion in vitro. Moreover, we settled the method also on polarized Calu-3 cells grown at air-liquid interface (ALI), showing that this assay can be extended to more complex cell models mimicking the airway epithelium.

Conclusions: We proved that this method is a sensitive, rapid and reproducible system to evaluate the anti-adhesive properties of vaccine-induced antibodies and can be employed to assess improved pertussis vaccines.
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http://dx.doi.org/10.1186/s12866-016-0829-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5025618PMC
September 2016