The effect of lectins on Cryptosporidium parvum oocyst in vitro attachment to host cells

The influence of lectins on Cryptosporidium parvum oocyst agglutination and on attachment to both fixed Madin Darby Canine Kidney (MDCK) cells and fixed HCT-8 (human colorectal epithelial) cells was examined. Oocyst cell wall characteristics were examined by transmission electron microscopy. Lectin-free oocysts were shown to adhere equally to both MDCK cells and HCT-8 cells. In MDCK cells, the addition of 1-25 μg/ml Codium fragile lectin, 10 μg/ml Maclura pomifera lectin, 10 μg/ml Helix pomatia lectin, and 10-200 μg/ml Artocarpus integrifolia lectin significantly increased attachment to at least 1 of the cell cultures as compared to oocysts incubated without any lectin. The lectin-enhanced attachment was reversed by coincubation of lectin treated-oocysts with 250 mM of each specific sugar (for a given lectin). In agglutination assays, concentrations as low as 0.5 μg/ml of C. fragile, M. pomifera, and A. integrifolia lectin agglutinated oocysts within 60 min. Finally, in TEM samples, colloidal gold conjugated-lectins from A. integrifolia, C. fragile, H. pomatia, and M. pomifera attached to oocysts, and this could be competitively inhibited by a lectin-specific sugar. This suggests that C. parvum oocysts are highly reactive to N-acetyl galactosamine-binding lectins and that the presence of N-acetyl-galactosamine containing molecules on oocysts can potentially help in oocyst attachment to host cells.