ABSTRACT: African trypanosomes have been recently shown to colonise the skin in a process critical for parasite transmission. However, the tissue responses to infection, especially in the lead to parasite transition from the host skin to the vector remain unresolved. Here, using a combination of spatial and single cell transcriptomics, coupled with imaging mass cytometry and genetic models, we investigated the local immune response of the skin in both a murine model of infection and in human samples from the Democratic Republic of Congo (DRC). Our results provide several novel key findings previously unappreciated in the context of parasitic infections in the skin. Firstly, we identified that the skin stromal cells, in particular interstitial preadipocytes located in the subcutis, upregulate several genes involved in inflammatory signalling and antigen presentation, including several molecules involved in T cell activation and survival. Secondly, we detected a significant expansion of a population of IL-17 producing Vg6 gdT cells in the infected murine skin compared to naïve controls, that occur mainly in the subcutis, that we further validated at the protein level by flow cytometry. In silico cell-cell communication analyses between adipocytes and T cells suggests that adipocytes trigger T cell activation locally via Il6, Il10, and Tnfsf18 signalling, amongst others. Thirdly, mice deficient of Vg6 gdT cells show extensive inflammation, increased IFNg-producing CD4+ T cells, and tissue parasite burden compared to naïve controls, indicating that Vg6 gdT cells are important to limit skin inflammation and parasite replication. Based on these observations, we proposed a model whereby interstitial preadipocytes (and potentially adipocytes) as well as Vg6 gdT cells act concertedly in the subcutis to limit tissue damage and parasite load, thus imposing an immunological barrier for transmission. These studies shed light into the mechanisms of gdT cells-mediated immunity in the skin in the context of African trypanosomes infection, as well as a potential role of immature and mature adipocytes as homeostatic regulators on the skin during chronic infection.
