Cryptosporidium parvum is a parasite that causes diarrhea for immunocompetent individuals. However for immunocompromised individuals, the symptoms are more severe and lethal. The waterborne disease is found worldwide and undergoes colonization in epithelial tissue. Bioinformatics data indicate that C. parvum has sixteen amyloid positive amino acids in its adhesion proteins. Activated amyloid nanodomains on the surface of Candida albicans cells were shown to mediate adhesion for cell-to-cell binding interactions (Lipke et al. 2014). Amyloid-perturbing dyes Thioflavin S and Congo Red were shown to decrease adhesion of Candida albicans to substrates (Chan, Lipke 2014). C.parvum sporozoites fluoresce when stained with 20 µM of Thioflavin S. Since adhesion is an essential first step to the infection of host cells, we studied whether amyloid-perturbing dyes would decrease adhesion of the parasite C.parvum to host ileocecal HCT-8 cells. We tested whether Thioflavin S, Congo Red, and Thioflavin T would inhibit adhesion of C.parvum to HCT-8 cells. We treated C.parvum sporozoites with 10 and 200 µM of Thioflavin S, 1 and 20 µM of Congo Red, and 0.1 and 2 µM of Thioflavin T. After a 15-hour infection of HCT-8 cells, we utilized the Merifluor reagent to measure the immunofluorescence of C.parvum oocysts and evaluate adhesion. The uninfected/non-treated HCT-8 cells’ fluorescence was measured at approximately onefold, while the infected but non-treated host cells’ fluorescence was at a near twofold increase. The most effective treatments for reducing adhesion were 20 µM of Congo Red (onefold) and 0.1 µM of Thioflavin T (onefold). These results show that these dyes lead to a decreased adhesion of C.parvum to the host HCT-8 cells. It is also demonstrated that the inclusion of these dyes can bring the infected host cells’ level of adhesion back down near the uninfected host cells’ level of adhesion, which denotes an inhibition of adhesion of C.parvum to the host HCT-8 cells.

Amyloid-perturbing dyes inhibit adhesion of Cryptosporidium parvum to the human ileocecal adenocarcinoma HCT-8 cell line

249th National Meeting (2015)

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