Anti-phagocytic effect of mannose-rich exopolysaccharide from a biofilm-forming strain of Prevotella intermedia

Abstract

Our previous studies revealed that several clinical isolates of Prevotella intermedia (P. intermedia) can produce the large amounts of exopolysaccharide (EPS) needed to form biofilm and resist the host's immune system. We used THP-1 cells with opsonized latex beads to investigate whether the EPS from P. intermedia biofilm acts as an anti-phagocytic factor in a phagocytosis model. In addition, we used microarray analysis to study how EPS influences the gene expression pattern of THP-1 cells during the phagocytosis process. Although EPS inhibited latex bead engulfment in a dose dependent manner, it did not inhibit recognition of opsonized latex beads by THP-1 cells. The inhibition of phgocytosis caused by EPS up-regulated the expression of more than 140 genes in THP-1 cells by two- to four-fold compared with the expression of THP-1 cells having a smooth phagocytosis process. These results may suggest that the EPS from P. intermedia has an anti-phagocytic effect and influences gene expression patterns as well as activities of the host's immune cells.