concanavalin-a and melezitose

There has been a re-emergence of the use of lectins in a variety of therapeutic venues. In addition lectins are often responsible for the binding of pathogens to cells and for cancer cell clumping that increases their escape from body defenses. It is important to define precisely the activity of inhibitors of lectin-binding that may be used in anti-infection and anti-cancer therapeutics. Here we describe a kinetic assay that measures the activity of saccharide inhibitors of lectin binding using a model system of yeast (Saccharomyces cerevisiae) and lectin (Concanavalin A, Con A) derivatized agarose microbeads that mimics pathogen-cell binding. We show that old methods (part I of this study) used to identify inhibitor activity using only one sugar concentration at one time point can easily provide wrong information about inhibitor activity. We assess the activity of 4 concentrations of 10 saccharides at 4 different times in 400 trials and statistically evaluate the results. We show that d-melezitose is the best inhibitor of yeast binding to the lectin microbeads. These results, along with physical chemistry studies, provide a solid foundation for the development of drugs that may be useful in anti-infectivity and anti-cancer therapeutics.

Topics: Anticarcinogenic Agents; Concanavalin A; Lectins; Microspheres; Saccharomyces cerevisiae; Trisaccharides

It was found that lectin-binding protein (LB) from leguminosae seeds can serve as mitogens B lymphocytes from athymic nu/nu mice. Most of the experiments were performed using a LB from Vicia faba as this was the most potent mitogen among all LB tested. When mixed B and T lymphocyte populations were stimulated by LB a bell-shaped dose-response curve resulted which is also characteristic of the corresponding lectins; LB, however, act at much higher concentrations than the lectins. In control experiments, using lymphocytes from C3H/HeJ mice which have a genetic defect with respect to lipopolysaccharide responsiveness, the enhancement of DNA synthesis by LB was comparable to that observed with other strains. This indicates that stimulation by LB does not result from contamination by lipopolysaccharides. B lymphocytes from nu/nu mice were stimulated by LB as efficiently as mixed T and B lymphocyte populations whereas lectins per se had no effect on nu/nu lymphocytes. Cyclosporin A, a fungal metabolite, is known to specifically suppress T cell responses. Cyclosporin A did not influence the mitogenic activity of the LB from Vicia faba on unseparated spleen cells. Cell populations enriched for T cells (lymph node cells: nylon wool-passed or nylon wool-passed and anti-Ia plus complement-treated) responded poorly to LB, if at all, even in the presence of interleukin 2-containing supernatants.

Topics: Animals; B-Lymphocytes; Concanavalin A; Cyclosporins; Female; Lectins; Lipopolysaccharides; Lymphocyte Activation; Lymphocyte Culture Test, Mixed; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Mice, Nude; Mitogens; Protein Binding; T-Lymphocytes; Thymidine; Trisaccharides