Epithelial processed Mycobacterium avium subsp. paratuberculosis induced prolonged Th17 response and suppression of phagocytic maturation in bovine peripheral blood mononuclear cells.

Johne's disease (JD) caused by Mycobacterium avium subsp. paratuberculosis (MAP) is a chronic, wasting infectious disease in ruminants that causes enormous economic losses to the dairy and beef cattle industries. Understanding the mechanism of persistency of MAP is key to produce novel ideas for the development of new diagnostic methods or prevention techniques. We sought interactions between the host and MAP using epithelial passage model, which mimic initial stage of infection. From the transcriptomic analysis of bovine immune cells (PBMCs), it was suggested that infection through the epithelial cells elicited prolonged Th17-derived immune response, as indicated by upregulation of IL-17A, IL-17F and RORC until 120 h p.i., compared to directly infected PBMCs. Global downregulation of gene expression was observed after 72 h p.i., especially for genes encoding cell surface receptors of phagocytic cells, such as Toll-like receptors and MHC class II molecules. In addition, the cholesterol efflux transporters ABCA1, ABCG1, and APOE, which are regulated by the LXR/RXR pathway, were downregulated. In summary, it would be suggested that the host initiate immune response to activate Th17-derived cytokines, and MAP survives persistently by altering the host adaptive immune response by suppressing surface receptors and manipulating lipid metabolism in phagocytic cells.