Trichomonas vaginalis and Tritrichomonas foetus: expression of chitin at the cell surface

The expression of chitin as a structural component of Trichomonas vaginalis and Tritrichomonas foetus was demonstrated by using enzymatic hydrolysis by recombinant (rec-) chitinase, chemical analysis, lectin, fluorescent Calcofluor and antibody binding, glycosidases of known specificity, high-performance liquid chromatography (HPLC), and flow cytometry. Chitinous structures were characterized by their insolubility in hot alkali and by releasing glucosamine on hydrolysis with 6 N HCl. N,N'-Diacetylchitobiose and N,N,'N''-triacetylchitotriose were identified by HPLC as enzymatic hydrolysis products of the alkali-resistant polysaccharide. The location of chitin on the surface of T. vaginalis and T. foetus was inferred from the decreased reactivity with whole parasites of ligands such as Lycopersicon esculentum (TOL) and Solanum tuberosum lectins, fluorescent Calcofluor, and anti-chitin antibody, after cell treatment with rec-chitinase. Binding of [125I]TOL showed that, in T. vaginalis and T. foetus, the numbers of lectin receptors per cell were 4.2 x 10(5) and 3.0 x 10(5), respectively. Binding of the lectin to the trichomonad surface was markedly decreased by treatment with rec-chitinase. TOL interaction with the parasites was not affected by N-acetyl-beta-D-glucosaminidase treatment, showing that the lectin receptors consisted of beta-linked GlcNAc polymers and not of terminal beta-linked GlcNAc residues.