Anti-adhesin antibodies that recognize a receptor-binding motif (adhesintope) inhibit pilus/fimbrial-mediated adherence of Pseudomonas aeruginosa and Candida albicans to asialo-GM1 receptors and human buccal epithelial cell surface receptors.

Pseudomonas aeruginosa and Candida albicans were reported to adhere to the glycosphingolipid asialo-GM1 by means of pili and fimbriae, respectively. These diverse adhesins have been previously reported to have an immunologically conserved antigenic epitope and the role of this cross-reactive epitope in adherence to asialo-GM1 was investigated in this study. Both the unbiotinylated PAK pilus and fimbrial adhesins inhibited biotinylated pili from P. aeruginosa PAK and biotinylated C. albicans fimbriae binding to asialo-GM1 and receptors present on human buccal epithelial cells (BECs), which suggested that the same receptor sites were recognized by the two adhesins. Monoclonal antibodies PK99H and Fm16 raised against the P. aeruginosa PAK pili and C. albicans fimbriae, respectively, recognized a conserved epitope present on the two adhesins. Both Fm16 and PK99H blocked fimbriae binding to asialo-GM1 and BEC receptors and also inhibited P. aeruginosa and C. albicans whole cell binding to BECs. These data suggested that the conserved epitope confers receptor-binding properties to the adhesins, demonstrated that (i) asialo-GM1-like receptors present on epithelial cell surfaces are utilized by the pilus and fimbrial adhesins and (ii) the binding to these glycoreceptors is mediated by a conserved epitope that has receptor-binding properties.