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International audience

International audience; Background: Cryptosporidiosis consists in acute gastrointestinal infections in young children and is one of the two main leading causes of diarrhea in newborn calves in France and England resulting in substantial financial losses for farmers and a source of contamination for humans. Despite the seriousness of cryptosporidiosis and the recent strong mobilization of the scientific community to find for new therapeutic strategies (eg Swale et al. PMID: 31694928), the obtention of new potent drugs targeting these pathogens is still urgently awaited.Objective: Identification of new potent orally active anti-Cryptosporidium compounds able to prevent and control an established infection in order to increment the poor number of therapeutics available. Material and Methods. A targeted library of approximately 1000 compounds was initially screened for anti-Cryptosporidium activity leading to the identification of 3 compounds with a best EC50 around 700 nM. Medicinal chemistry guided by structure activity relationship (SAR) via in vitro assays in HCT-8 cell cultured with transgenic Cryptosporidium was applied to optimise efficiency. Best compounds from in vitro selection were evaluated as oral therapeutics in mouse models (neonatal mice, IFNγ-/-) and neonatal lambs. Results: Successive in vitro assays following chemical improvement allowed to identify several drugs active in the nanomolar range, with the best candidates with EC50 in low sub nanomolar range. Both mice models and lamb experiments confirmed the strong efficacy (parasite load; weight gain) of these soluble and orally administrable compounds. No adverse effects were detected in the in vivo experiment. Conclusion: The strong efficacy of the best compounds combined to low toxicity revealed their robust selectivity for Cryptosporidium, thus revealing the strong potential of these new therapeutics which hopefully will be able to participate in the future arsenal of therapeutics required for optimal cryptosporidiosis control.

National audience

International audience; Cryptosporidiosis is a poorly controlled zoonosis caused by an intestinal parasite, Cryptosporidium parvum (Cp), with a high prevalence in livestock (cattle, sheep, goats). Young animals are particularly susceptible to this infection due to the immaturity of their intestinal immune system. In a neonatal mouse model, we previously demonstrated the importance of the innate immunity and in particular of CD11c+CD103+CD11b-conventional dendritic cells (cDC) among mononuclear phagocytes (MP) in controlling the acute phase of Cp infection. During infection, in response to chemokine production by infected epithelial cells, newly recruited cDCs produce IL12 and IFNγ contributing to the elimination of the parasite. According to the well-established mouse cDC classification, this Batf3+DC subpopulation corresponds to the cDC1 subset. The aim of this project was to better characterize intestinal MP subpopulations in neonatal lamb and calf at homeostasis and during Cp infection. As in the mouse model, the parasite invades and multiplies mainly in the ileum of animals. However, a peculiarity of young ruminants is the presence of a large ileal Peyer’s patch (lymphoid tissue) that extends all along the ileum. MP were therefore analyzed in lymphoid and non-lymphoid intestinal tissues of lambs and claves. We performed phenotypic and functional analyses of mononuclear phagocytes by flow cytometry and by transcriptomic methods (FLUIDIGM®) respectively, in the distal jejunum, jejunal and ileal Peyer’s patches. We characterized a population of macrophages and three subpopulations of cDC. We demonstrated that the subset identified as cDC1, according to the current common classification of cDC in different species (human, mouse, pig, sheep and chicken), increases with the age of animal. This might be linked with the decrease in sensitivity to C. parvum observed with the age. We are currently investigating the evolution of cDC1 subset during C. parvum infection.