scholarly journals Characterization and immunogenicity of a Shigella flexneri 2a O-antigen bioconjugate vaccine candidate

Glycobiology ◽  
2019 ◽  
Vol 29 (9) ◽  
pp. 669-680 ◽  
Author(s):  
Neil Ravenscroft ◽  
Martin Braun ◽  
Joerg Schneider ◽  
Anita M Dreyer ◽  
Michael Wetter ◽  
...  
Keyword(s):  
Diarrheal Disease ◽  
Vaccine Candidate ◽  
Shigella Flexneri ◽  
Preventive Measure ◽  
Shigella Dysenteriae ◽  
O Antigen ◽  
Shigella Flexneri 2A ◽  
Single Production ◽  
Functional Antibodies ◽  
Efficacious Vaccine

AbstractShigellosis remains a major cause of diarrheal disease in developing countries and causes substantial morbidity and mortality in children. Vaccination represents a promising preventive measure to fight the burden of the disease, but despite enormous efforts, an efficacious vaccine is not available to date. The use of an innovative biosynthetic Escherichia coli glycosylation system substantially simplifies the production of a multivalent conjugate vaccine to prevent shigellosis. This bioconjugation approach has been used to produce the Shigella dysenteriae type O1 conjugate that has been successfully tested in a phase I clinical study in humans. In this report, we describe a similar approach for the production of an additional serotype required for a broadly protective shigellosis vaccine candidate. The Shigella flexneri 2a O-polysaccharide is conjugated to introduced asparagine residues of the carrier protein exotoxin A (EPA) from Pseudomonas aeruginosa by co-expression with the PglB oligosaccharyltransferase. The bioconjugate was purified, characterized using physicochemical methods and subjected to preclinical evaluation in rats. The bioconjugate elicited functional antibodies as shown by a bactericidal assay for S. flexneri 2a. This study confirms the applicability of bioconjugation for the S. flexneri 2a O-antigen, which provides an intrinsic advantage over chemical conjugates due to the simplicity of a single production step and ease of characterization of the homogenous monomeric conjugate formed. In addition, it shows that bioconjugates are able to raise functional antibodies against the polysaccharide antigen.

scholarly journals Stable Chromosomal Expression of Shigella flexneri 2a and 3a O-Antigens in the Live Salmonella Oral Vaccine Vector Ty21a

2017 ◽  
Vol 24 (12) ◽  
Author(s):  
Madushini N. Dharmasena ◽  
Manuel Osorio ◽  
Kazuyo Takeda ◽  
Scott Stibitz ◽  
Dennis J. Kopecko
Keyword(s):  
Oral Vaccine ◽  
Shigella Flexneri ◽  
Serum Antibody ◽  
Vaccine Vector ◽  
Shigella Dysenteriae ◽  
Antigenic Determinants ◽  
Content Type ◽  
O Antigen ◽  
Shigella Flexneri 2A ◽  
O Antigens

ABSTRACT We have been exploring the use of the live attenuated Salmonella enterica serovar Typhi Ty21a vaccine strain as a versatile oral vaccine vector for the expression and delivery of multiple foreign antigens, including Shigella O-antigens. In this study, we separately cloned genes necessary for the biosynthesis of the Shigella flexneri serotype 2a and 3a O-antigens, which have been shown to provide broad cross-protection to multiple disease-predominant S. flexneri serotypes. The cloned S. flexneri 2a rfb operon, along with bgt and gtrII, contained on the SfII bacteriophage, was sufficient in Ty21a to express the heterologous S. flexneri 2a O-antigen containing the 3,4 antigenic determinants. Further, this rfb operon, along with gtrA, gtrB, and gtrX contained on the Sfx bacteriophage and oac contained on the Sf6 bacteriophage, was sufficient to express S. flexneri 3a O-antigen containing the 6, 7, and 8 antigenic determinants. Ty21a, with these plasmid-carried or chromosomally inserted genes, demonstrated simultaneous and stable expression of homologous S. Typhi O-antigen plus the heterologous S. flexneri O-antigen. Candidate Ty21a vaccine strains expressing heterologous S. flexneri 2a or 3a lipopolysaccharide (LPS) elicited significant serum antibody responses against both homologous S. Typhi and heterologous Shigella LPS and protected mice against virulent S. flexneri 2a or 3a challenges. These new S. flexneri 2a and 3a O-antigen-expressing Ty21a vaccine strains, together with our previously constructed Ty21a strains expressing Shigella sonnei or Shigella dysenteriae 1 O-antigens, have the potential to be used together for simultaneous protection against the predominant causes of shigellosis worldwide as well as against typhoid fever.

scholarly journals Molecular Modeling of the Shigella flexneri Serogroup 3 and 5 O-Antigens and Conformational Relationships for a Vaccine Containing Serotypes 2a and 3a

Vaccines ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 643
Author(s):  
Jason Hlozek ◽  
Sara Owen ◽  
Neil Ravenscroft ◽  
Michelle M. Kuttel
Keyword(s):  
Diarrheal Disease ◽  
Shigella Flexneri ◽  
Quadrivalent Vaccine ◽  
Slight Effect ◽  
Work Support ◽  
O Antigen ◽  
The Common ◽  
O Antigens ◽  
Chain Conformations ◽  
Shared Epitopes

The pathogenic bacterium Shigella flexneri is a leading global cause of diarrheal disease. The O-antigen is the primary vaccine target and distinguishes the 30 serotypes reported. Except for serotype 6, all S. flexneri serotypes have a common backbone repeating unit (serotype Y), with variations in substitution creating the various serotypes. A quadrivalent vaccine containing serotypes 2a and 3a (as well as 6 and Shigella sonnei) is proposed to provide broad protection against non-vaccine S. flexneri serotypes through shared epitopes and conformations. Here we model the O-antigen (O-Ag) conformations of serogroups 3 and 5: a continuation of our ongoing systematic study of the S. flexneri O-antigens that began with serogroup 2. Our simulations show that S. flexneri serogroups 2, 3, and 5 all have flexible O-Ags, with substitutions of the backbone altering the chain conformations in different ways. Our analysis suggests three general heuristics for the effects of substitution on the Shigella O-Ag conformations: (1) substitution on rhamnose C reduces the extension of the O-Ag chain; (2) substitution at O-3 of rhamnose A restricts the O-Ags to predominantly helical conformations, (3) substitution at O-3 of rhamnose B has only a slight effect on conformation. The common O-Ag conformations across serotypes identified in this work support the assumption that a quadrivalent vaccine containing serotypes 2a and 3a could provide coverage against S. flexneri serotype 3b and serogroup 5.

Live Shigella flexneri 2a and Shigella sonnei I vaccine candidate strains with two attenuating markers

Vaccine ◽  
1990 ◽  
Vol 8 (1) ◽  
pp. 30-34 ◽  
Author(s):  
V. Dentchev ◽  
S. Marinova ◽  
Tch. Vassilev ◽  
M. Bratoyeva ◽  
K. Linde
Keyword(s):  
Vaccine Candidate ◽  
Shigella Flexneri ◽  
Shigella Sonnei ◽  
Shigella Flexneri 2A

scholarly journals The normal chain length distribution of the O antigen is required for the interaction of Shigella flexneri 2a with polarized Caco-2 cells

2012 ◽  
Vol 45 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Anilei Hoare ◽  
Denisse Bravo ◽  
Mara Martinic ◽  
Miguel A Valvano ◽  
Inés Contreras ◽  
...  
Keyword(s):  
Chain Length ◽  
Shigella Flexneri ◽  
Length Distribution ◽  
Chain Length Distribution ◽  
O Antigen ◽  
Shigella Flexneri 2A

scholarly journals Molecular detection of all 34 distinct O-antigen forms of Shigella

2009 ◽  
Vol 58 (1) ◽  
pp. 69-81 ◽  
Author(s):  
Yayue Li ◽  
Boyang Cao ◽  
Bin Liu ◽  
Dan Liu ◽  
Qili Gao ◽  
...  
Keyword(s):  
Shigella Flexneri ◽  
Bacterial Species ◽  
Milk Powder ◽  
Shigella Dysenteriae ◽  
Detection Sensitivity ◽  
Clinical Samples ◽  
Shigella Boydii ◽  
O Antigen ◽  
Probe Concentration ◽  
O Antigens

Shigella is the cause of shigellosis or bacillary dysentery, the occurrence of which is estimated to be 165 million cases per year worldwide, resulting in 1.1 million deaths. Rapid and reliable assays for detecting and identifying Shigella in food, environmental and clinical samples are therefore necessary. Shigella species are traditionally identified by their O antigens. This study developed a DNA microarray targeting O-serotype-specific genes to detect all 34 distinct O-antigen forms of Shigella, including Shigella boydii types 1–18, Shigella dysenteriae types 1–13, Shigella flexneri types 1–5 and 6, and Shigella sonnei. A total of 282 strains were used to test the specificity of the microarray, including 186 Shigella and Escherichia coli representative strains, 86 Shigella clinical isolates and ten strains of other bacterial species that are commonly isolated from food or clinical stool specimens. The oligonucleotide probes were printed on the microarray in concentrations from 1 to 100 μM, and 10 μM proved to be the optimal probe concentration. The detection sensitivity for each serotype was 50 ng genomic DNA or 1 c.f.u. in 25 g milk powder sample following a 6 h enrichment in broth. The microarray is specific, sensitive and reproducible, and, to our knowledge, is the first report of a microarray for serotyping all O-antigen forms of Shigella.

scholarly journals Influence of Shigella flexneri 2a O Antigen Acetylation on Its Bacteriophage Sf6 Receptor Activity and Bacterial Interaction with Human Cells

2020 ◽  
Vol 202 (24) ◽  
Author(s):  
Min Yan Teh ◽  
Axel Furevi ◽  
Göran Widmalm ◽  
Renato Morona
Keyword(s):  
Shigella Flexneri ◽  
Limited Range ◽  
World Health ◽  
Bacteriophage Therapy ◽  
Chemical Modifications ◽  
Content Type ◽  
O Antigen ◽  
Shigella Flexneri 2A ◽  
Bacterial Interaction ◽  
Health Organization

ABSTRACT Shigella flexneri is a major causative agent of bacillary dysentery in developing countries, where serotype 2a2 is the prevalent strain. To date, approximately 30 serotypes have been identified for S. flexneri, and the major contribution to the emergence of new serotypes is chemical modifications of the lipopolysaccharide (LPS) component O antigen (Oag). Glucosylation, O-acetylation, and phosphoethanolamine (PEtN) modifications increase the Oag diversity, providing benefits to S. flexneri. LPS Oag acts as a primary receptor for bacteriophage Sf6, which infects only a limited range of S. flexneri serotypes (Y and X). It uses its tailspike protein (Sf6TSP) to establish initial interaction with LPS Oags that it then hydrolyzes. Currently, there is a lack of comprehensive study on the parent and serotype variant strains from the same genetic background and an understanding of the importance of LPS Oag O-acetylations. Therefore, a set of isogenic strains (based on S. flexneri 2457T [2a2]) with deletions of different Oag modification genes (oacB, oacD, and gtrII) that resemble different naturally occurring serotype Y and 2a strains was created. The impacts of these Oag modifications on S. flexneri sensitivity to Sf6 and the pathogenesis-related properties were then compared. We found that Sf6TSP can hydrolyze serotype 2a LPS Oag, identified that 3/4-O-acetylation is essential for resistance of serotype 2a strains to Sf6, and showed that serotype 2a strains have better invasion ability. Lastly, we revealed two new serotype conversions for S. flexneri, thereby contributing to understanding the evolution of this important human pathogen. IMPORTANCE The emergence of antibiotic-resistant strains and lack of efficient vaccines have made Shigella a priority organism for the World Health Organization (1). Therefore, bacteriophage therapy has received increasing attention as an alternative therapeutic approach. LPS Oag is the most variable part of LPS due to chemical modifications and is the target of bacteriophage Sf6 (S. flexneri specific). We dissected the evolution of S. flexneri serotype Y to 2a2, which revealed a new role for a gene acquired during serotype conversion and furthermore identified new specific forms of LPS receptor for Sf6. Collectively, these results unfold the importance of the acquisition of those Oag modification genes and further our understanding of the relationship between Sf6 and S. flexneri.

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