| Summary: | The role of Prevotella, a Gram-negative anaerobe, frequently detected in the airways of patients with cystic fibrosis (CF), is not well understood. The aims of this study were to determine the lipopolysaccharide (LPS) chemotype of Prevotella spp. isolated from CF and non-CF patients and to characterise both the structure and inflammatory potential of Prevotella spp. LPS. Also, to ascertain the extent of capsular polysaccharide (CPS) production by these isolates and to investigate the role of Prevotella spp. CPS within the CF airways. SDS-PAGE demonstrated LPS consisting solely of a lipid A-core oligosaccharide in 33/36 (92%) CF isolates and 9/18 (50%) non-CF isolates. Structural elucidation of LPS revealed a highly negatively charged heptasaccharide containing hexoses, with the first two sugars of the core region highly phosphorylated. The lipid A moiety possessed the typical structure of the genus Prevotella lipid A and was also highly phosphorylated. The biological properties of P. denticola and P. intermedia LPS were examined in THP-1 cells over a 24-h period. The THP-1 cell peak response to Prevotella, E. coli, and P. aeruginosa LPS was within the same order of magnitude for IL-8, IL-6, and IL-1 (3. However, Prevotella LPS induced earlier up-regulation of gene expression and a more rapid pro-inflammatory response in THP-1 cells. Prevotella spp. isolates were screened for capsule production using eosin staining and brightfield microscopy. The majority of Prevotella spp. isolates (43/49; 87.8 %) were capsulated, with capsulated isolates significantly more resistant to complement mediated killing. Purified Prevotella spp. CPS induced a pro-inflammatory response in THP-1 monocytes, and also caused a significant decrease in the susceptibility of both Prevotella spp. and P. aeruginosa isolates to the cationic antimicrobial peptide polymyxin B. These findings indicate that Prevotella spp. isolates may have the potential to contribute to chronic inflammatory processes within the airways patients with CF.
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