Identification of the common antigenic determinant shared by Streptococcus pneumoniae serotypes 33A, 35A, and 20 capsular polysaccharides

Lin, Fiona L.; Vinogradov, Evgeny; Deng, Cunbao; Zeller, Sandra; Green, Bruce A.; Jansen, Kathrin U.; Pavliak, Viliam

doi:10.1016/j.carres.2013.08.001

Cited by 12 publications

(20 citation statements)

References 21 publications

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“…To confirm that the 33X1 and 33X2 capsules were chemically distinct from 33A and 33F, polysaccharides were purified and their O-acetylation patterns were characterized by nuclear magnetic resonance (NMR). Prior studies analyzing the 33A and 33F polysaccharides identified peaks associated with WcjE-and WciG-mediated O-acetylation (25,27). As expected, 33A polysaccharide had both WciG-associated (2.13 ppm) (Fig.…”

Section: Figsupporting

confidence: 66%

“…3B). We extended the 2D NMR analysis by assigning all the other peaks in the 33X1 and 33X2 spectra (Table 1) with the help of published NMR spectra of 33A and 33F (25,27). The analysis confirmed that WcjE adds O-acetyl groups to the fifth and sixth carbons of 3-␤-D-galactofuranose (Galf) and that WciG adds an O-acetyl group to the second carbon of 5-␤-D-Galf.…”

Section: Figmentioning

confidence: 83%

“…Serotype 33A and 33F strains could be differentiated by fs20b, which recognizes WcjE-mediated O-acetylation present in the 33A capsule ( Fig. 2) (25). Additionally, an in-house monoclonal antibody, Hyp33FG1, bound 33F and partially cross-reacted with 33A.…”

Section: Resultsmentioning

confidence: 99%

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Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F

et al. 2017

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Streptococcus pneumoniae (pneumococcus) produces many capsule types that differ in their abilities to evade host immune recognition. To explain these serotypedependent protective capacities, many studies have investigated capsular thickness or the interaction of the capsule with complement proteins, but the effects of small chemical modifications of the capsule on its function have not been studied. One small chemical modification found frequently among pneumococcal capsules is O-acetylation. Pneumococcal serotype 33A has two membrane-bound O-acetyltransferase genes, wciG and wcjE. A 33A wcjE-deficient variant, 33F, occurs naturally and is increasing in prevalence in the wake of widespread conjugate vaccine use, but no wciG-deficient variants have been reported. To study the biological consequence of the loss of O-acetylation, we created wciG-deficient variants in both serotypes 33A and 33F, which we named 33X1 (ΔwciG) and 33X2 (ΔwciG ΔwcjE). Serotypes 33X1 and 33X2 express novel capsule types based on serological and biochemical analyses. We found that loss of WcjE-mediated O-acetylation appears not to affect cell wall shielding, since serotypes 33A and 33F exhibit comparable nonspecific opsonophagocytic killing, biofilm production, and adhesion to nasopharyngeal cells, though serotype 33F survived short-term drying better than serotype 33A. Loss of WciG-mediated O-acetylation in serotypes 33X1 and 33X2, however, resulted in a phenotype resembling that of nonencapsulated strains: increased cell wall accessibility, increased nonspecific opsonophagocytic killing, enhanced biofilm formation, and increased adhesion to nasopharyngeal cells. We conclude that WciG-mediated, but not WcjE-mediated, O-acetylation is important for producing protective capsules in 33A and that small chemical changes to the capsule can drastically affect its biological properties.KEYWORDS O-acetyltransferase, O-acetylation, capsular diversity, pneumococcal vaccine, capsular polysaccharide, serotype S treptococcus pneumoniae (pneumococcus) is an important human pathogen that can colonize the nasopharynx asymptomatically and disseminate opportunistically to cause pneumonia, meningitis, septicemia, and otitis media. The pneumococcus has a polysaccharide capsule, and 98 distinct capsular types (serotypes) have been identified based on chemical differences in their capsular repeat units (1-3). These chemical differences are mediated by genetic changes in the capsular polysaccharide synthesis (cps) operon (4) and result in different reactivities with anti-capsule antibodies. The capsule is essential for pneumococcal virulence (5), since it shelters pneumococci from complement fixation and opsonophagocytosis (6). However, differences in capsule type have been shown to affect complement fixation and virulence (7).

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Section: Figsupporting

confidence: 66%

Section: Figmentioning

confidence: 83%

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Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F

et al. 2017

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“…Since WciG-mediated O-acetylation correlates with factor serum 35a, factor serum 35a must target the O-acetyl group conserved in serogroup 35 members other than 35D. Similarly, factor serum 20b has been shown to recognize WcjE-mediated O-acetylation (20), which is present in both the serotype 35A and 35C repeat units (13; K. A. Geno, C. A. Bush, M. H. Nahm, and J. Yang, unpublished data). Binding of factor serum 35b distinguishes serotype 29, whose first repeat unit sugar is Gal, from serotype 35D, whose first repeat unit sugar is Glc.…”

Section: Discussionmentioning

confidence: 99%

Discovery of Novel Pneumococcal Serotype 35D, a Natural WciG-Deficient Variant of Serotype 35B

2017

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Pneumococcus (Streptococcus pneumoniae) remains a significant cause of morbidity and mortality, especially among those at the extremes of age. Its capsular polysaccharide is essential for systemic virulence. Over 90 serologically distinct pneumococcal capsular polysaccharides (serotypes) are recognized, but they are unequal in prevalence. Because antibodies against the capsule are protective, polysaccharide conjugate vaccines, which are constructed against the most prevalent serotypes, have caused great reductions in pneumococcal disease caused by these serotypes. In response, however, the relative prevalences of serotypes have shifted. Certain previously rare serotypes, such as serotype 35B, are increasing in prevalence. Serotype 35B is thus a likely future vaccine candidate, but due to their previous rarity, serotype 35B strains have not been scrutinized for underlying heterogeneity. We studied putative serotype 35B clinical isolates to assess the uniformity of their serological reactions. While most isolates exhibited the accepted serology of serotype 35B, one isolate failed to bind to critical serotyping reagents. We determined that the genetic basis for this aberrant serology was the presence of inactivating mutations in the O-acetyltransferase gene wciG. Complementation studies in a wciG deletion strain verified that the mutant WciG was nonfunctional, and the serology of the mutant could be restored through complementation with a construct encoding a functional WciG. Nuclear magnetic resonance studies confirmed that the capsule of the WciG-deficient isolate lacked O-acetylation but was otherwise identical to serotype 35B. As this isolate expresses a unique serology with unique biochemistry and a stable genetic basis, we named its novel capsule serotype 35D.KEYWORDS O-acetylation, Streptococcus pneumoniae, capsular polysaccharide, serogroup 35, serotype 35B, serotype 35D S treptococcus pneumoniae (pneumococcus) is an important human pathogen that can express many different polysaccharide capsules that protect the organism from opsonophagocytic killing (1). As antibodies to the capsule are protective, currently available vaccines against pneumococcus are designed to elicit antibodies to the capsule and have been highly successful in reducing the incidence of invasive pneumococcal disease (IPD). A pneumococcal polysaccharide-protein conjugate vaccine (PCV) with polysaccharide from the seven most commonly observed serotypes (PCV7) was introduced in the United States in 2000 and reduced the incidence of IPD in children younger than 5 by over 75% (2); the updated 13-valent PCV (PCV13) has reduced the incidence of IPD by an additional 64% in this age group in the United States (3). However, the protection by these vaccines is serotype specific, and their widespread implementation has brought shifts in the serotypes found in both nasopharyngeal carriage and IPD (see, e.g., reference 4).

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“…expression of a new serotype, e.g., 33A/33F and 15B/15C (22)(23)(24). We are developing methods to detect capsule O-acetylation in other serogroups and investigating the role these capsule features play in pneumococcal ecology.…”

Section: Figmentioning

confidence: 99%

Spectrum of Pneumococcal Serotype 11A Variants Results from Incomplete Loss of Capsule O -Acetylation

Calix

Brady

et al. 2014

J Clin Microbiol

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Streptococcus pneumoniae is a significant bacterial pathogen that expresses >90 capsule serotypes. Conventional serotyping methods assume that each serotype is a genetically and antigenically distinct entity; however, recent investigations have revealed pneumococcal isolates that cannot be unambiguously serotyped because they share the properties of more than one serotype. Here, we employed a novel serotyping method and NMR spectroscopy to examine clinical isolates sharing properties of serotypes 11A and 11E. These ambiguous clinical isolates were provisionally named 11A variant (11Av) isolates. Serotype 11A pneumococci characteristically express capsule ␤-galactose-6-O-acetylation (␤Gal6OAc) mediated by the capsule synthesis gene wcjE, while 11E strains contain loss-of-function mutations in wcjE and completely lack the expression of ␤Gal6OAc. Although 11Av isolates also contained mutated wcjE alleles, 11Av clinical isolates were composed of antigenically homogeneous bacteria expressing reduced amounts of 11A-specific capsule antigen. NMR data confirmed reduced but detectable amounts of ␤Gal6OAc on 11Av capsule polysaccharide. Furthermore, the transformation of strains with wcjE alleles from 11Av strains was sufficient to restore partial ␤Gal6OAc in an 11E background. We conclude that, instead of being distinct entities, serotypes 11A and 11E represent two extremes of an antigenic spectrum resulting from variable capsule O-acetylation secondary to heterologous wcjE mutations. These findings challenge whether all clinically relevant pneumococci can be definitively categorized into distinct serotypes.

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Identification of the common antigenic determinant shared by Streptococcus pneumoniae serotypes 33A, 35A, and 20 capsular polysaccharides

Cited by 12 publications

References 21 publications

Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F

Position of O-Acetylation within the Capsular Repeat Unit Impacts the Biological Properties of Pneumococcal Serotypes 33A and 33F

Discovery of Novel Pneumococcal Serotype 35D, a Natural WciG-Deficient Variant of Serotype 35B

Spectrum of Pneumococcal Serotype 11A Variants Results from Incomplete Loss of Capsule O -Acetylation

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