Effects of carbohydrates and lectins on cryptosporidial sporozoite penetration of cultured cell monolayers.

Cryptosporidium parvum first interacts with enterocytes when sporozoites penetrate the host plasma membrane. We have developed a shell vial assay using human embryonic Intestine 407 cells and purified C. parvum sporozoites to study this process. Sporozoites were incubated in culture medium with various carbohydrates and lectins, and the suspensions were then added to the cell monolayers. Following incubation, the monolayers were fixed and stained and the number of schizonts were counted. No decreases in sporozoite motility or Intestine 407 cell viability were observed with carbohydrate or lectin treatment. N-Acetyl-D-glucosamine, chitobiose and chitotriose inhibited C. parvum infection, compared to 5 other tested carbohydrates. Wheat germ agglutinin reduced penetration and concanavalin A enhanced schizont formation, when compared to 8 other lectins. Next, we pretreated sporozoites or Intestine 407 cells with wheat germ agglutinin and concanaval in A prior to sporozoite inoculation. Wheat germ agglutinin treatment of sporozoites or cells equally caused a reduction in C. parvum infection, while enhancement was only observed when Intestine 407 cell were pretreated with concanavalin A. These data suggest that glycoproteins with terminal N-acetyl-D-glucosamine residues may play a role in C. parvum adhesion or penetration of enterocytes. Also, host glycoproteins with concanavalin A-like activity may play a role in these processes.