Quantitation of concanavalin A and wheat germ agglutinin binding by two strains of Trichomonas vaginalis of differing pathogenicity using gold particle-conjugated lectins.

Two strains of Trichomonas vaginalis, which differed in their pathogenicity for both women and experimental animals hosts, were compared for the presence and number of concanavalin A (ConA)- and wheat germ agglutinin (WGA)-binding sites on their surface using gold lectin conjugates. Both strains showed a high affinity for ConA and WGA and a similar pattern of gold particle distribution on the surface coat. The gold marker was distributed over the cytoplasmic membrane sparsely as single particles but more often in groups, suggesting the presence of single and clustered sugar residues on the parasite surface. Statistical analysis of the level of lectin binding, expressed as the number of gold particles attached per 1 micron plasmalemma, by pathogenic and non-pathogenic strains of T. vaginalis show that these two strains do not differ in the number of ConA receptors on their surfaces. However, WGA-binding receptors were more numerous on the surface of the pathogenic than on the non-pathogenic strain. This suggests that these two strains differ in the number of N-acetyl-D-glucosamine residues on their surfaces. The lectin-gold particle conjugate technique therefore appears more sensitive than agglutination assays or the horseradish peroxidase-3,3'-diaminobenzidine method for the assessment of lectin-binding sites on the surface of T. vaginalis.