Analysis of the In Vitro Transcriptional Response of Human Pharyngeal Epithelial Cells to AdherentStreptococcus pneumoniae: Evidence for a Distinct Response to Encapsulated Strains

Abstract

Infection of the human host by Streptococcus pneumoniae begins with colonization of the nasopharynx, which is mediated by the adherence of bacteria to the respiratory epithelium. Several studies have indicated an important role for the pneumococcal capsule in this process. Here, we used microarrays to characterize the in vitro transcriptional response of human pharyngeal epithelial Detroit 562 cells to the adherence of serotype 2 encapsulated strain D39, serotype 19F encapsulated strain G54, serotype 4 encapsulated strain TIGR4, and their nonencapsulated derivatives (⌬cps). In total, 322 genes were found to be upregulated in response to adherent pneumococci. Twenty-two genes were commonly induced, including those encoding several cytokines (e.g., interleukin 1␤ [IL-1␤] and IL-6), chemokines (e.g., IL-8 and CXCL1/2), and transcriptional regulators (e.g., FOS), consistent with an innate immune response mediated by Toll-like receptor signaling. Interestingly, 85% of genes were induced specifically by one or more encapsulated strains, suggestive of a capsule-dependent response. Importantly, purified capsular polysaccharides alone had no effect. Over a third of these loci encoded products predicted to be involved in transcriptional regulation and signal transduction, in particular mitogenactivated protein kinase signaling pathways. Real-time PCR of a subset of 10 genes confirmed the microarray data and showed a time-dependent upregulation of, especially, innate immunity genes. The downregulation of epithelial genes was most pronounced upon adherence of D39⌬cps, as 68% of the 161 genes identified were repressed only by this nonencapsulated strain. In conclusion, we identified a subset of host genes specifically induced by encapsulated strains during in vitro adherence and have demonstrated the complexity of interactions occurring during the initial stages of pneumococcal infection.

Plasminogen- and Fibronectin-binding Protein B Is Involved in the Adherence of Streptococcus pneumoniae to Human Epithelial Cells

“…3, right panels) adhered to the cells more efficiently than the encapsulated parental D39 strain (Fig. 3, left panels), in agreement with the known ability of the capsule to mask adhesins in pneumococci (4,20). Notably, the pfbB-deleted strains adhered less efficiently than the corresponding parental strains to all tested cell lines.…”

“…It is well known that the presence of a thick capsule can hinder pneumococcal adherence, due to a "masking" effects on surface adhesins (4,20). Accordingly, we found that the encapsulated D39 strain adhered to epithelial cells severalfold less efficiently than its unencapsulated derivatives.…”

“…2B). Weaker binding to the encapsulated strain relative to the unencapsulated one was not surprising, because it is known that the polysaccharide capsule can mask surface expression of cell wall-linked proteins (20). As expected, anti-sp17 sera did not bind the pfbB-deleted mutants FP228 and FP242 (data not shown).…”

Interleukin‐8 gene regulation in epithelial cells by Vibrio cholerae: role of multiple promoter elements, adherence and motility of bacteria and host MAPKs

“…We hypothesize that the reduction in IL-8 secretion obtained with the OmpU insertional mutant OMPUN could be due to alterations in the adherence of bacteria. Our results support our previous finding that bacterial adherence to epithelial cells stimulates IL-8 production [37][38][39]. Flagellin of V. cholerae, which were shown to trigger IL-8 release both in vitro and in vivo was considered as a potential virulence factor contributing to an inflammatory response in the host [15][16][17].…”

Adherence of Streptococcus pneumoniae to Polystyrene Plates and Epithelial Cells and the Antiadhesive Potential of Albumin and Xylitol

“…The low adherence observed in the three serotype 3 strains tested here also confirms such observations. However, nonencapsulated strains or isogenic nonencapsulated derivatives of capsulated pneumococci that were usually of transparent phenotype showed greater binding ability to epithelial cells than that of the capsulated WT strains (26). Pneumococcal adherence to epithelial cells not only depends on the bacteria but also on the host cells.…”