Factor H binding to PspC of Streptococcus pneumoniae increases adherence to human cell lines in vitro and enhances invasion of mouse lungs in vivo.
ABSTRACT Pneumococcal surface protein C (PspC) binds to both human secretory immunoglobulin A (sIgA) and complement factor H (FH). FH, a regulator of the alternative pathway of complement, can also mediate adherence of different host cells. Since PspC contributes to adherence and invasion of host cells, we hypothesized that the interaction of PspC with FH may also mediate adherence of pneumococci to human cells. In this study, we investigated FH- and sIgA-mediated pneumococcal adherence to human cell lines in vitro. Adherence assays demonstrated that preincubation of Streptococcus pneumoniae D39 with FH increased adherence to human umbilical vein endothelial cells (HUVEC) 5-fold and to lung epithelial cells (SK-MES-1) 18-fold, relative to that of D39 without FH on the surface. The presence of sIgA enhanced adherence to SK-MES-1 6-fold and to pharyngeal epithelial cells (Detroit 562) 14-fold. Furthermore, sIgA had an additive effect on adherence to HUVEC; specifically, preincubation of D39 with both FH and sIgA led to a 21-fold increase in adherence. Finally, using a mouse model, we examined the significance of the FH-PspC interaction in pneumococcal nasal colonization and lung invasion. Mice intranasally infected with D39 preincubated with FH had increased bacteremia and lung invasion, but they had similar levels of nasopharyngeal colonization compared to that of mice challenged with D39 without FH.
Article: Recombinant generation of two fragments of the rat complement inhibitory factor H [FH(SCR1-7) and FH(SCR1-4)] and their structural and functional characterization in comparison to FH isolated from rat serum.[show abstract] [hide abstract]
ABSTRACT: Factor H (FH) is the predominant soluble inhibitor of the complement system. With a concentration of 200-800 microg/ml in human and rat plasma it acts as a cofactor for the soluble factor I (FI)-mediated cleavage of the component C3b to iC3b. Furthermore it competes with factor B for binding to C3b and C3(H2O) and promotes the dissociation of the C3bBb complex. FH is a monomer of about 155 kDa which comprises 20 short consensus repeats (SCR), each of which is composed of approximately 60 amino acid (aa) residues. Two functional fragments of FH comprising the SCR1-4 or SCR1-7 were generated using either the Baculovirus system or stably transfected human embryonal kidney cells, respectively. These fragments, as well as FH purified from rat serum, were first analyzed for their relative molecular weights (Mr) using non-reducing or reducing SDS-PAGE. The Mr of the FH variants differed by about 20% depending on the experimental conditions employed. Only the Mr of proteins separated under reducing conditions were in accordance with the MW calculated from the aa sequence. Analyses of the glycosylation patterns using PAS-staining showed a lack of staining of the recombinant variants (SCR1-4 and SCR1-7) in contrast to FH(SCR1-20) from serum. Using a complement hemolysis assay (CH50-assay) all three variants exhibited a molar complement inhibitory activity of FH(1-20)/FH(1-7)/FH(1-4) of about 3/1/1. These data support the postulated model of FH bearing three binding sites for its ligand C3b, from which one is located in the SCR1-4, whereas the other two are located in the SCR8-20.Histology and histopathology 02/2006; 21(1):93-102. · 2.48 Impact Factor
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ABSTRACT: Pneumococcal surface protein C (PspC) binds to the complement regulatory protein factor H (FH), which inhibits alternative pathway activation. In the present study, using a mouse model of systemic infection and flow-cytometric analyses, we demonstrated an in vivo interaction between FH and pneumococci and showed differential FH binding during bacteremia. Flow-cytometric analyses of pneumococci harvested after intraperitoneal (ip) challenge demonstrated increased binding of FH, compared with that after intravenous (iv) challenge. Real-time polymerase chain reaction analyses of PspC mRNA showed that, relative to pneumococci grown in vitro, those recovered from the blood of mice 24 h after iv challenge exhibited 23-fold higher mRNA levels; however, after ip challenge, PspC mRNA induction was increased 870-fold. A subsequent increase in PspC expression was detected by flow cytometry using a monoclonal antibody against PspC. Furthermore, pneumococci with FH bound to complement before exposure had increased proliferation, compared with pneumococci not pretreated with FH. These results suggest that the interaction between PspC and FH contributes to pneumococcal virulence.The Journal of Infectious Diseases 01/2006; 192(11):1996-2003. · 6.41 Impact Factor
Article: Innate immunity of the sinonasal cavity: expression of messenger RNA for complement cascade components and toll-like receptors.[show abstract] [hide abstract]
ABSTRACT: To study the expression of important elements of the innate immune responses in human sinonasal tissue to elucidate its potential role in mucosal inflammation. We studied human sinonasal tissue from patients with chronic rhinosinusitis and an immortalized epithelial cell line to detect the expression of innate immune effectors and the responses of these cells to stimulation with compounds associated with pathogenic organisms. Nine individuals undergoing endoscopic sinus surgery for chronic rhinosinusitis. Expression of complement components and toll-like receptors. We found detectable levels of messenger RNA for all toll-like receptors in human sinonasal tissue and in the BEAS-2B epithelial cell line. Expression of several components of the alternate pathway of complement (factors B, H, and I and properdin) was constitutively present in unstimulated BEAS-2B cells and was readily detectable in human sinonasal tissue. Stimulation of BEAS-2B cells with the toll-like receptor 3 ligand double-stranded RNA resulted in increased expression of messenger RNA for factors B and H but not for properdin or factor I. Toll-like receptors and the alternate pathway of complement are important components of innate immunity that are expressed in human sinonasal epithelium in vivo and in cultured airway epithelial cells in vitro. The expression of some of these components can be significantly induced by stimulation via toll-like receptors, and epithelial expression of components of innate immunity may play a role in inflammation in chronic rhinosinusitis.Archives of Otolaryngology - Head and Neck Surgery 01/2005; 130(12):1374-80. · 1.63 Impact Factor