title: Scavenger receptor gp340 aggregates group A streptococci by binding pili.
abstract: Group A streptococci (GAS) are the most frequent cause of bacterial pharyngitis. The first obstacle to GAS colonization of the pharynx is saliva. As well as forming a physical barrier, saliva contains components of innate and acquired immunity. Previous work has shown that saliva induces bacterial aggregation, which may serve as a clearance mechanism. As the aggregation of some oral streptococci in saliva is mediated by long proteinaceous appendages, we hypothesized that pili of GAS might behave similarly. Wild-type GAS M1 strain SF370 aggregated in saliva, while pilus-defective mutants did not. Similarly, heterologous expression of diverse GAS pili on the surface of Lactococcus lactis induced aggregation in saliva, while control strains were unaffected. Further studies revealed that aggregating bacteria bound salivary component gp340. Purified gp340 aggregated wild-type GAS and L. lactis expressing GAS pili, but not control strains. GAS pilus-defective mutants were abrogated in gp340 binding and aggregation. Furthermore, gp340-mediated aggregation reduced bacterial adhesion to human epithelial cells, suggesting a role in host defence.
authors.affiliation: Novartis Vaccines, Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Edwards
authors.forename: Andrea G O
authors.initials: AG
authors.lastname: Manetti
authors.forename: Fabiana
authors.initials: F
authors.lastname: Falugi
authors.forename: Chiara
authors.initials: C
authors.lastname: Zingaretti
authors.forename: Sabrina
authors.initials: S
authors.lastname: Capo
authors.forename: Scilla
authors.initials: S
authors.lastname: Buccato
authors.forename: Giuliano
authors.initials: G
authors.lastname: Bensi
authors.forename: John L
authors.initials: JL
authors.lastname: Telford
authors.forename: Immaculada
authors.initials: I
authors.lastname: Margarit
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins; D036781:Fimbriae Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000378:metabolism; D006801:Humans; D013294:Lactococcus lactis / Q000235:genetics / Q000502:physiology; D051379:Mice; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D012463:Saliva / Q000378:metabolism; D012471:Salivary Proteins and Peptides / Q000302:isolation & purification / Q000378:metabolism*; D013290:Streptococcal Infections / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000235:genetics / Q000502:physiology*; D025521:Tumor Suppressor Proteins
chemical_list: D001426:Bacterial Proteins; D002135:Calcium-Binding Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; D011956:Receptors, Cell Surface; D012471:Salivary Proteins and Peptides; D025521:Tumor Suppressor Proteins; D036781:Fimbriae Proteins