Abstract
Conditions affecting the adherence of clinical isolates of Cryptococcus neoformans to rat glial and lung cell cultures were studied. Adherence to glial cells was a time-dependent process that was affected by the yeast culture age and growth temperature. The most adherent yeasts were those from 48 h cultures grown at 37°C. Formalin-treating the yeasts did not affect adherence but formalin-treating the glial monolayers prevented yeast binding. Treating the yeasts with trypsin reduced adherence to glial monolayers, indicating that the yeast adhesin had a trypsin-labile protein component. Certain carbohydrates inhibited cryptococcal adherence to glial and lung cells in a time and concentration-dependent manner. Of the carbohydrates tested, N-acetyl-d-glucosamine, sucrose, lactose, sorbitol and myo-inositol were the most inhibitory, while mannose, galactose and xylose were the least inhibitory. The results collectively indicated that the mechanisms of adherence of C. neoformans to lung cells were similar to those of glial cells and that both involved a protein-containing adhesin on the cryptococcal surface that was expressed only after growth at 37°C. Carbohydrate receptors also appeared to be involved with these interactions.