Adhesion of Pseudomonas aeruginosa to human buccal epithelial cells: evidence for two classes of receptors

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Abstract
The adhesion of P. aeruginosa strain 492c to trypsinized and untrypsinized buccal epithelial cells (BECs) was studied. Kinetic analysis of the adhesion data, empolying a Langmuir absorption isotherm, indicated the presence of 2 classes of binding sites of untrypsinized BECs: a high affinity-low copy number site [apparent association constant (Ka .apprxeq. 1.57 .times. 10-8 ml/cell with .apprx. 29 binding sites/cell] and a low affinity-high copy number class of binding sites [Ka .apprxeq. 4.78 .times. 10-10 ml/cell with .apprx. 264 binding sites/cell]. The low affinity-high copy number class of sites was found to be trypsin sensitive. A single class of binding sites was found on trypsinized BECs exhibiting a high affinity-low copy number [Ka .apprxeq. 3.70 .times. 10-7 ml/cell with .apprx. 31 binding sites/cell]. Positive cooperativity in binding of P. aeruginosa strain 492c to the low affinity -high copy number class site on untrypsinized BECs was demonstrated by analysis of Hill plots of the adhesion data. Sugar inhibition data using a preincubation methodology showed an inhibition of adhesion to trypsinized BECs in the presence of N-acetylneuraminic acid and D-arabinose, while these same 2 sugars enhanced adhesion to untrypsinized BECs. D-Galactose and N-acetylglucosamine enhanced adhesion to both types of BECs though the latter did to different extents. D-Fucose only inhibited adhesion to untrypsinized BECs. Without preincubation the sugar inhibition data indicated that N-acetylglucosamine had no effect on adhesion, while N-acetylneuraminic acid and D-fucose both enhanced adhesion to both types of BECs. D-Arabinose had a slight inhibitory effect on adhesion, while D-galactose had a slight enhancing effect to both cell types, but to different levels. This sugar data suggests a difference in the receptors on the 2 types of BEC, but the possibility of metabolism of these sugars by P. aeruginosa requires one to interpret this data with caution. Flagella were shown not to be involved in adhesion, while the alginic acid of the capsule was implicated. The low copy number binding site is speculated to be a pili-binding site, while the high copy number class of binding sites is proposed to involve a lectin which binds alginic acid.