Contribution of novel choline‐binding proteins to adherence, colonization and immunogenicity of Streptococcus pneumoniae

Abstract

SummaryThe surface of Streptococcus pneumoniae is decorated with a family of choline-binding proteins (CBPs) that are non-covalently bound to the phosphorylcholine of the teichoic acid. Two examples (PspA, a protective antigen, and LytA, the major autolysin) have been well characterized. We identified additional CPBs and characterized a new CBP, CbpA, as an adhesin and a determinant of virulence. Using choline immobilized on a solid matrix, a mixture of proteins from a pspA-deficient strain of pneumococcus was eluted in a choline-dependent fashion. Antisera to these proteins passively protected mice challenged in the peritoneum with a lethal dose of pneumococci. The predominant component of this mixture, CbpA, is a 75-kDa surface-exposed protein that reacts with human convalescent antisera. The deduced sequence from the corresponding gene showed a chimeric architecture with a unique N-terminal region and a C-terminal domain consisting of 10 repeated choline-binding domains nearly identical to PspA. A cbpA-deficient mutant showed a >50% reduction in adherence to cytokine-activated human cells and failed to bind to immobilized sialic acid or lacto-N-neotetraose, known pneumococcal ligands on eukaryotic cells. Carriage of this mutant in an animal model of nasopharyngeal colonization was reduced 100-fold. There was no difference between the parent strain and this mutant in an intraperitoneal model of sepsis. These data for CbpA extend the important functions of the CBP family to bacterial adherence and identify a pneumococcal vaccine candidate.

Purification of native α-enolase from Streptococcus pneumoniae that binds plasminogen and is immunogenic

“…Subsequent invasion of human endothelial cells is promoted by cytokine activation which increases the amount of surface-expressed platelet-activating factor (PAF) re- ceptor that in turn binds to the phosphorylcholine component of the cell wall [28]. An adhesin CbpA promotes increased attachment to activated human cells [29]. Recent studies showed that pneumococci could bind to reconstituted basement membrane as well as to a purified laminin component [4].…”

Versatility of pneumococcal surface proteins

“…The ectodomain of pIgR is also known as the secretory component (SC), and independent reports have indicated that the human specificity of the PspC-SC interaction is determined by amino acid differences in ectodomains D3 and D4 of the SC (Elm et al, 2004;Lu et al, 2003). Despite such human specificity, loss of function in PspC has been shown to reduce colonization of infant rats (Rosenow et al, 1997) and pIgR knockout mice (Zhang et al, 2000). The hexameric SC-binding site in PspC is located in N-terminal repeated domains (Hammerschmidt et al, 2000), recently designated R1 and R2.…”

Phage display reveals 52 novel extracellular and transmembrane proteins from Lactobacillus reuteri DSM 20016T

“…Three proteins possibly involved in specific interaction between L. reuteri and its host were identified: Lre0019 with similarities to the S. pneumoniae PspC; Lre0018 with similarities to the Lactobacillus johnsonii Apf1; and the previously described CnBP (Roos et al, 1996). The cell surface adhesin PspC is involved in colonization of mucosal surfaces in the nasopharynx (Balachandran et al, 2002;Rosenow et al, 1997). The protein interferes with the complement pathway by binding to the third component, C3 (Cheng et al, 2000), and to factor H (Dave et al, 2001).…”