Characterization of the intestinal mononuclear phagocytic cells in the intestine of the lamb to better understand the immune response against Cryptosporidium parvum

International audience; Cryptosporidiosis is a poorly controlled zoonosis caused by the intestinal infection by a protozoan parasite, Cryptosporidium parvum (Cp), presenting a high prevalence in ruminant farms (cattle, sheep, goats). Young animals with an immature intestinal immune system are particularly susceptible to this infection. In a neonatal mouse model, we previously demonstrated the key role of innate immunity and in particular of CD11c+CD103+CD11b- dendritic cell (DC) subset incontrolling the acute phase of Cp infection [1]. During infection, in response to chemokine production by infected epithelial cells, newly recruited CD11c+CD103+CD11b- DC produce IL12 and IFNγ contributing to the elimination process of the parasite. According to the current common classification of DC in different species (human, mouse, pig, sheep, and chicken), this subpopulation can be identified as the cDC1 subset of conventional DC. The aim of this project was to better characterize intestinal DC subpopulations in lamb and to determine their role during Cp infection. As in the mouse model, the parasite invades and multiplies mainly in the ileum of young lambs. However, a peculiarity of young ruminants is the presence of a large ileal Peyer’s patch (lymphoid tissue) that extends all along the ileum. We characterized in various compartments of the lamb small intestine (lymphoid and non-lymphoid) the various mononuclear phagocyte populations by performing a phenotypic and functional analysis by flow cytometry and transcriptomic methods respectively. We followed the evolution of the cell subsets according to the age of the animals and during Cp infection. This work represents the first fine description of mononuclear phagocyte cell subsets in the small intestine of young lambs at homeostasis and during the course of C. parvum infection.