Effects of selected condensed tannins on Cryptosporidium parvum growth and proliferation in HCT-8 cell cultures

Authors: WOOLSEY, IAN - Norwegian Veterinary Institute; Zeller, Wayne; BLOMSTRAND, BERIT - Norwegian Centre For Organic Agriculture; OLINES, OLVIND - Norwegian Veterinary Institute; ENEMARK, HEIDI - Norwegian Veterinary Institute

Submitted to: Experimental Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2022
Publication Date: 8/19/2022
Citation: Woolsey, I.D., Zeller, W.E., Blomstrand, B.M., Oines, O., Enemark, H.L. 2022. Effects of selected condensed tannins on Cryptosporidium parvum growth and proliferation in HCT-8 cell cultures. Experimental Parasitology. 241. Article 108353. https://doi.org/10.1016/j.exppara.2022.108353.
DOI: https://doi.org/10.1016/j.exppara.2022.108353

Interpretive Summary: Protozoan parasites of the genus Cryptosporidium constitute a major public health burden worldwide in addition to substantial production losses to the livestock industry where bovine cryptosporidiosis is established as a major cause of calf enteritis. Condensed tannins (CTs) are plant secondary metabolites that have been shown to demonstrate anti-parasitic properties in vitro and in vivo particularly against gastrointestinal nematode parasites of ruminants. Considering this previous research and the severe problems associated with Cryptosporidium spp. infection in humans and livestock, bioactive assessment of CT against these protozoa is warranted. Cryptosporidium parvum infected cell cultures were treated with escalating doses of structurally diverse CTs from five different plant species but revealed that none of the CTs examined demonstrated inhibitory potential against the parasite. These studies clarify that caution should be exercised with CT-containing plant extracts which show inhibitory effects against Cryptosporidium spp. (i.e. pomegranate) and that this activity is likely not due to the presence of CTs in the extracts. It is important that investigators are informed of candidate compounds contained within these extracts which show little promise against Cryptosporidium spp.

Technical Abstract: Infections with Cryptosporidium spp. constitute a substantial public health burden and are responsible for widespread production losses in cattle herds. Reducing disease and shedding of Cryptosporidium spp.oocysts is an important One Health goal. There are very few therapeutic options available to treat cryptosporidiosis. Interest in plant bioactive compounds to mitigate the spread of anthelmintic resistance in ruminants has led to investigation of these phytocompounds against other parasitic taxa. Condensed tannins (CTs) are plant secondary metabolites that have shown potential against nematodes in vitro and in vivo but their applicability to Cryptosporidium spp. is comparatively under-explored. Cryptosporidium parvum infected human ileocecal colorectal adenocarcinoma (HCT)-8 cell cultures were treated with escalating doses of highly purified and well-characterized CTs from five plant species, big trefoil (Lotus pedunculatus), black currant (Ribes nigrum), sainfoin (Onobrychis viciifolia), whiteclover (Trifolium repens) and grapeseed (Vitis vinifera) for 44h. Quantitative-PCR (qPCR) analysis revealed that none of the CTs examined demonstrated inhibitory potential against the parasite. Substantial inhibition ofC. parvum by paromomycin was observed in positive controls in all assays (76.94–90.72% inhibition), proving the validity of the assay. Despite the lack of inhibition, these results represent an important step towards identifying alternative treatment options against this parasite.