Relationship between the ability of oral streptococci to interact with platelet glycoprotein Ibα and with the salivary low-molecular-weight mucin, MG2

Abstract

The oral streptococci Streptococcus sanguinis, Streptococcus gordonii and Streptococcus oralis are common aetiological agents of infective endocarditis, and their ability to adhere to and induce the aggregation of platelets is thought to be a virulence trait. The platelet glycoprotein GPIbalpha has been implicated as the adhesion receptor for S. sanguinis and S. gordonii, but it is not known if this is the case for S. oralis and other species. The aim of this study was to determine the GPIbalpha-interactive capability of a range of oral streptococci and to determine the relationship between this capability and their ability to interact with the salivary constituents that they would encounter in their normal habitat. All platelet-adhesive S. sanguinis strains and most S. gordonii strains adhered in a GPIbalpha-dependent manner, but strains of S. oralis, Streptococcus cristatus, Streptococcus parasanguinis and Streptococcus mitis had no direct affinity for platelets. Those strains that were able to bind GPIbalpha also bound to the low-molecular-weight submandibular salivary mucin, MG2, and this interaction was sialic acid-dependent. The data suggest that S. sanguinis and S. gordonii may be efficient colonizers of platelet vegetations because of their adaptation to recognize sialylated salivary mucins. In contrast, S. oralis does not interact with platelets and so is likely to colonize vegetations through an as yet unidentified mechanism.

Streptococcus oralis Neuraminidase Modulates Adherence to Multiple Carbohydrates on Platelets

“…The wide distribution of these carbohydrates suggests that this adherence mechanism mediates binding to these carbohydrates in a range of contexts and, as a result, is likely important in adherence to not only platelets and endothelial cells but also other host surfaces, including the oral cavity. Previous studies have demonstrated a reduction in binding of other SRRP mutants to salivary proteins and in vitro models of oral surfaces (41,(62)(63)(64). The demonstration that a fap1 mutant has reduced adherence for an oral epithelial cell line supports the hypothesis that this protein contributes to S. oralis binding in the oral cavity; however, further studies will be required to determine the precise contribution.…”

Characterisation and expression of SPLUNC2, the human orthologue of rodent parotid secretory protein

“…Crittenden cups and a custom-made silicone impression device, respectively (Plummer et al 2006). Whole stimulated saliva was collected from several volunteers by chewing sugarfree gum and unstimulated saliva was collected over several minutes by allowing saliva to pool briefly in the mouth.…”

Streptococcus gordoniiHsa Environmentally Constrains Competitive Binding byStreptococcus sanguinisto Saliva-Coated Hydroxyapatite

“…By elucidating the salivary receptor(s) in this competition phenomenon, we will determine whether Hsa-mediated attachment of S. gordonii directly blocks the same receptor utilized by S. sanguinis or prevents access of S. sanguinis to its own pellicle receptor(s). For example, both S. gordonii and S. sanguinis have been shown to bind salivary mucin MG2 (35,52). Alternatively, salivary pellicle binding sites identified for S. sanguinis include a complex of ␣-amylase and the light chain of sIgA (7).…”