Chemical Structures of Streptococcus pneumoniae Capsular Polysaccharide Type 39 (CPS39), CPS47F, and CPS34 Characterized by Nuclear Magnetic Resonance Spectroscopy and Their Relation to CPS10A

Abstract

c Structural characterization of Streptococcus pneumoniae capsular polysaccharides (CPS) is a prerequisite for unraveling both antigenic and genetic relationships that exist between different serotypes. In the current study, comparative structural studies of S. pneumoniae CPS serogroup 10 (CPS10) were extended to include genetically related S. pneumoniae CPS34, CPS39, and CPS47F. High-resolution heteronuclear nuclear magnetic resonance (NMR) spectroscopy confirmed the published structure of CPS34 and, in conjunction with glycosyl composition analyses, revealed the following repeat unit structures of the other serotypes, which have not been previously characterized:Common and unique structural features of these polysaccharides, including different positions of O-acetylation, were unambiguously associated with specific genes in each corresponding cps locus. The only exception involved the gene designated wcrC, which is associated with the ␣1-2 transfer of Gal pyranoside (Galp) to ribitol-5-phosphate in the synthesis of CPS10A, CPS47F, and CPS34 but with ␣1-1 transfer of Gal to ribitol-5-phosphate in the synthesis of CPS39. The corresponding gene in the cps39 locus, although related to wcrC, more closely resembled a previously identified gene (i.e., wefM) of Streptococcus oralis that is associated with ␣1-1 transfer of Galp to ribitol-5-phosphate. These and other recent findings identify linkages from ␣-Galp to ribitol-5-phosphate and from this residue to adjacent Gal furanoside (Galf) as important sites of CPS structural and genetic diversity. Streptococcus pneumoniae capsular polysaccharides (CPS) are of interest both as virulence factors and as protective immunogens for serotype-specific prevention of invasive disease. Currently recommended CPS-based vaccines include the 23-valent pneumococcal polysaccharide vaccine for adults and the 13-valent pneumococcal conjugate vaccine for children. Monitoring the efficacy of these vaccines requires ongoing surveillance of invasive pneumococcal serotypes (1). The traditional method for serotyping these bacteria is the Neufeld-Quellung test, which detects apparent swelling of bacterial capsules in the presence of factor antisera (2). Such determinations, although reliable, require training, experience, and specialized immunological reagents and, thus, are not amenable to widespread use. Molecular methods for serotyping these bacteria have also been described and are being developed that target genes for CPS biosynthesis in large operons (cps loci) located between dexB and aliA (3, 4). Sequencing of this region in reference strains of 88 S. pneumoniae serotypes revealed 1,502 genes, each defined by a different protein homology group (5). These include 430 genes for putative glycosyltransferases, 69 for sugar/polyalcohol phosphate transferases, 78 for acetyltransferases, 90 for different polymerases (Wzy) and 88 for different flippases (Wzx) (6). The proteins encoded by some of these genes have been shown biochemically to have the predicted function (4), and a number of other...

Structures of Capsular Polysaccharide Serotypes 35F and 35C of Streptococcus pneumoniae Determined by Nuclear Magnetic Resonance and Their Relation to Other Cross-Reactive Serotypes

“…5B) in a manner consistent with that used in previous studies of these types (18) and types 34, 42, and 47F (16). CPS structures are now available for all five serotypes with genes designated wcrJ (Table 2).…”

“…Additional WcrH acceptors may thus be suggested from the structures of CPS36 and CPS43, the only serotypes in genetic cluster 4 (9) that remain to be structurally characterized. CR931721, CR931703, CR931704, CR931706, CR931715, CR931705, and CR931694) (A) with the corresponding CPS structures determined in the present or previous investigations (10,11,16,17,19) (B). The antigenic formulas of the CPS serotypes are indicated in parentheses.…”

“…1A) showed four peaks that were assigned the letters A, B, C, and E, chosen to correspond to the four Gal residues of genetically related CPS47F (16). Like CPS47F, the anomeric resonance of residues A and C were assigned to ␤-Galf on the basis of their downfield 13 C chemical shifts (Table 1).…”

Capsular Polysaccharide Expression in CommensalStreptococcusSpecies: Genetic and Antigenic Similarities to Streptococcus pneumoniae

“…S5). The transferases (genes 0350 and 0351, core-2/I-branching enzyme [pfam02485]) catalyzing these two bonds are somewhat related (40 to 45% identity) to the products of the wcrM and wcrG genes in S. pneumoniae serotypes 29 and 35B and in serotypes 10A and 39, respectively (11, 27, 48) (Table S3). The five mentioned pneumococcal polysaccharides contain a glycosylic linkage shared with SK137.…”

A New Pneumococcal Capsule Type, 10D, is the 100th Serotype and Has a Large cps Fragment from an Oral Streptococcus

“…Serologically, 39X cross-reacts with FS10d and Hyp10AG1, which recognize a structural motif shared by serotypes 39 and 10A ( Fig. S3) (24). Indeed, Cam853 was mistyped as 10A (17,20).…”