title: Structural reevaluation of Streptococcus pneumoniae Lipoteichoic acid and new insights into its immunostimulatory potency.
abstract: Streptococcus pneumoniae is a Gram-positive human pathogen with a complex lipoteichoic acid (pnLTA) structure. Because the current structural model for pnLTA shows substantial inconsistencies, we reinvestigated purified and, more importantly, O-deacylated pnLTA, which is most suitable for NMR spectroscopy and electrospray ionization-MS spectrometry. We analyzed pnLTA of nonencapsulated pneumococcal strains D39Δcps and TIGR4Δcps, respectively. The data obtained allowed us to (re)define (i) the position and linkage of the repeating unit, (ii) the putative α-GalpNAc substitution at the ribitiol 5-phosphate (Rib-ol-5-P), and (iii) the length of (i.e. the number of repeating units in) the pnLTA chain. We here also describe for the first time that the terminal sugar residues in the pnLTA (Forssman disaccharide; α-D-GalpNAc-(1→3)-β-D-GalpNAc-(1→)), responsible for the cross-reactivity with anti-Forssman antigen antibodies, can be heterogeneous with respect to its degree of phosphorylcholine substitution in both O-6-positions. To assess the proinflammatory potency of pnLTA, we generated a (lipopeptide-free) Δlgt mutant of strain D39Δcps, isolated its pnLTA, and showed that it is capable of inducing IL-6 release in human mononuclear cells, independent of TLR2 activation. This finding was quite in contrast to LTA of the Staphylococcus aureus SA113Δlgt mutant, which did not activate human mononuclear cells in our experiments. Remarkably, this is also contrary to various other reports showing a proinflammatory potency of S. aureus LTA. Taken together, our study refines the structure of pnLTA and indicates that pneumococcal and S. aureus LTAs differ not only in their structure but also in their bioactivity.
authors.affiliation: Division of Immunochemistry, Leibniz-Center for Medicine and Biosciences, Borstel, Germany. ngisch@fz-borstel.de
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gisch
authors.forename: Thomas
authors.initials: T
authors.lastname: Kohler
authors.forename: Artur J
authors.initials: AJ
authors.lastname: Ulmer
authors.forename: Johannes
authors.initials: J
authors.lastname: Müthing
authors.forename: Thomas
authors.initials: T
authors.lastname: Pribyl
authors.forename: Kathleen
authors.initials: K
authors.lastname: Fischer
authors.forename: Buko
authors.initials: B
authors.lastname: Lindner
authors.forename: Sven
authors.initials: S
authors.lastname: Hammerschmidt
authors.forename: Ulrich
authors.initials: U
authors.lastname: Zähringer
mesh_terms: D000276:Adjuvants, Immunologic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D000907:Antibodies, Bacterial / Q000276:immunology; D000910:Antibodies, Heterophile / Q000276:immunology; D006801:Humans; D015850:Interleukin-6 / Q000276:immunology / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008958:Models, Molecular; D009154:Mutation; D013045:Species Specificity; D013211:Staphylococcus aureus / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D013682:Teichoic Acids / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D000907:Antibodies, Bacterial; D000910:Antibodies, Heterophile; C508600:IL6 protein, human; D015850:Interleukin-6; D008070:Lipopolysaccharides; C495342:TLR2 protein, human; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; C009900:lipoteichoic acid
keywords: Analytical Chemistry; Forssman Antigen; Immunostimulatory Potency; Innate Immunity; Lipoteichoic Acid; Mass Spectrometry (MS); NMR; Streptococcus pneumoniae; Structural Biology