Characterization of Intestinal mononuclear phagocyte subsets of young lamb at homeostasis by single cell RNA-Seq and during Cryptosporidium parvum infection by flow cytometry.

Abstract

International audienceIntestinal mononuclear phagocytes are key immune cells that maintain intestinal homeostasis and participate in the protective immune responses toward pathogens. Cryptosporidiosis is a poorly controlled zoonosis caused by an intestinal parasite, Cryptosporidium parvum (Cp), with a high prevalence in ruminant farms. 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 in controlling the acute phase of Cp infection and deciphered the role of different subsets of intestinal mononuclear phagocytes in this protective immune response. The aim of this project was to better characterize intestinal mononuclear phagocytes in lamb at homeostasis and during Cp infection. 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 (IPP) (lymphoid tissue) that extends all along the ileum. We first performed a characterization of mononuclear phagocytes present in the IPP of a non-infected 10-day-old lamb by a single cell transcriptomic approach on CD11c+ MHCII+ sorted cells. This global approach allowed us to identify in the IPP of young lamb two main populations of macrophages and at least three different population of dendritic cells. Then, we carried out phenotypic and functional analyses of these different cell subsets by flow cytometry and transcriptomic methods in various compartments of the small intestine at homeostasis and during infection