BINDING OF ACANTHAMOEBA TO 23 MANNOSE-GLYCOPROTEINS OF CORNEAL EPITHELIUM - EFFECT OF INJURY

Purpose. Acanthamoeba keratitis is a sight-threatening corneal infecti on, It is known that: (i) more amoebae bind to the surface of injured corneas than to the normal corneal surface and (ii) mannose-containing glycoproteins (GPs) possess binding sites for Acanthamoeba. The prese nt study was undertaken to determine whether subtle corneal surface in jury exposes mannose-GPs and whether more amoebae bind to the mannose- GPs of injured corneas than to those of normal corneas. Methods. Corne al cup assays were developed to determine whether corneal surface inju ry exposes binding sites for a mannose/glucose-specific lectin, succin ylated-concanavalin A (s-ConA), To determine whether injury exposes ma nnose-GPs, corneal surface proteins were biotinylated, biotin-labeled mannose-GPs were allowed to bind to s-ConA-agarose beads and were anal yzed by SDS-polyacrylamide gel electrophoresis (PAGE), Amoeba binding to mannose-GPs of corneal epithelia was analyzed by PAGE-blot overlay assays. Results. S-ConA binding site density was 2.4 times greater on the injured corneal surface than on the surface of normal corneas. Bas ed on the analysis of the s-ConA-bound, biotin-labeled corneal surface proteins. approximately 5.2, limes greater amounts of mannose-GPs wer e present on the surface of injured corneas than on the normal corneal surface. PAGE-blot overlay assays of s-ConA bound GPs of unlabeled co rneal epithelia revealed that, on a per mg total cell protein basis, i njured corneal epithelium contained 1.8 times greater amounts of Acant hamoeba-reactive mannose-GPs than normal corneal epithelium. Conclusio ns. Subtle corneal injury exposes mannose-GPs on the surface of injure d corneas. The newly exposed GPs may serve to provide additional attac hment sites for the amoebae. This, in turn, could render the cornea su sceptible to the infection.