title: Streptococcus pneumoniae capsular serotype invasiveness correlates with the degree of factor H binding and opsonization with C3b/iC3b.
abstract: Different capsular serotypes of Streptococcus pneumoniae vary markedly in their ability to cause invasive infection, but the reasons why are not known. As immunity to S. pneumoniae infection is highly complement dependent, variations in sensitivity to complement between S. pneumoniae capsular serotypes could affect invasiveness. We have used 20 capsule-switched variants of strain TIGR4 to investigate whether differences in the binding of the alternative pathway inhibitor factor H (FH) could be one mechanism causing variations in complement resistance and invasive potential between capsular serotypes. Flow cytometry assays were used to assess complement factor binding and complement-dependent neutrophil association for the TIGR4 capsule-switched strains. FH binding varied with the serotype and inversely correlated with the results of factor B binding, C3b/iC3b deposition, and neutrophil association. Differences between strains in FH binding were lost when assays were repeated with pspC mutant strains, and loss of PspC also reduced differences in C3b/iC3b deposition between strains. Median FH binding was high in capsule-switched mutant strains expressing more invasive serotypes, and a principal component analysis demonstrated a strong correlation between serotype invasiveness, high FH binding, and resistance to complement and neutrophil association. Further data obtained with 33 clinical strains also demonstrated that FH binding negatively correlated with C3b/iC3b deposition and that median FH binding was high in strains expressing more invasive serotypes. These data suggest that variations in complement resistance between S. pneumoniae strains and the association of a serotype with invasiveness could be related to capsular serotype effects on FH binding.
authors.affiliation: Centre for Inflammation and Tissue Repair, Division of Medicine, University College Medical School, Rayne Institute, London, United Kingdom.
authors.forename: Catherine
authors.initials: C
authors.lastname: Hyams
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Trzcinski
authors.forename: Emilie
authors.initials: E
authors.lastname: Camberlein
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Weinberger
authors.forename: Suneeta
authors.initials: S
authors.lastname: Chimalapati
authors.forename: Mahdad
authors.initials: M
authors.lastname: Noursadeghi
authors.forename: Marc
authors.initials: M
authors.lastname: Lipsitch
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Brown
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000276:immunology / Q000378:metabolism; D016667:Bacterial Capsules / Q000276:immunology* / Q000378:metabolism; D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism; D002648:Child; D003176:Complement C3 / Q000276:immunology* / Q000378:metabolism; D003179:Complement C3b / Q000276:immunology* / Q000378:metabolism; D017242:Complement Factor H / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000276:immunology; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D011008:Pneumococcal Infections / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D011485:Protein Binding / Q000276:immunology; D012703:Serotyping / Q000379:methods; D013296:Streptococcus pneumoniae / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism / Q000472:pathogenicity
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D003176:Complement C3; D003179:Complement C3b; D017242:Complement Factor H