Invasion of Burkholderia cepacia complex isolates into lung epithelial cells involves glycolipid receptors

Burkholderia cepacia complex (Bcc) is a group of opportunistic cystic fibrosis (CF) pathogens that invade lung epithelial cells. The mechanisms of invasion are poorly understood, in particular, the receptors utilised by this bacterium in the invasion process have not been identified. The aim of this study was to investigate the epithelial receptors involved in the invasion of Bcc isolates. We confirmed that invasion into two lung epithelial cell lines (16HBE14o- and CFBE41o-) which have a non-CF and CF phenotype, respectively, is receptor mediated and showed that pre-treatment of these epithelial cell lines with α- or β-galactosidase reduced invasion of isolates of two species of Bcc, Burkholderia multivorans and Burkholderia cenocepacia. In contrast, removal of mucin had no significant effect. Biotinylated Bcc strains were shown to bind to purified glycolipids separated by thin layer chromatography, albeit different patterns of binding were associated with different strains. Invasion of CF lung epithelial cells (CFBE41o-) by all three Bcc strains examined was significantly reduced by treatment of cells with inhibitors of glycolipid biosynthesis. Although the specific glycolipid involved in each case has not been elucidated, it is apparent that invasion of lung epithelial cells is mediated via binding to glycosphingolipid receptors.