Mycobacterium avium subspecies paratuberculosis (MAP) drives an innate Th17-like T cell response and upregulation of inhibitory signals

Abstract

Abstract Johne’s disease (JD) is a chronic inflammatory gastrointestinal disorder of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Our work suggested that MAP may drive a non-classical Th17-like response in PBMCs. Our objectives were to determine if Th17 cell activation by MAP required the presence of antigen presenting cells (APCs) and to determine how epithelial cells might influence Th17 activation. Monocytes were isolated by adhering and washing protocols and then cultured for 5 days to allow differentiation into macrophages. T cells and B cells were isolated using magnetic-activated cell sorting (MACS) by positive selection of CD3+ and sIgM+ cells, respectively. MACS cells were then cultured or cocultured with macrophages. MDBK cells were used as an epithelial cell model. qPCR was used to determine mRNA expression levels of MDBK, T cells alone, and T cells cultured with macrophages or B cells. All T cell cultures increased IL-17a and IL-23 mRNA expression with MAP-antigen stimulation when compared to untreated cells. APC containing cultures expressed significantly more IL-17a than T cells alone. IL-22 expression was only observed in T cell cultures stimulated with live MAP. T cell exhaustion and tolerance markers (PD-1, PD-L1, LAG-3) were increased in T cell only cultures when stimulated with MAP, but repressed in the presence of APCs. The presence of MDBK cells upregulated IL-23 following stimulation with MAP, suggesting that epithelial cells exposed to MAP may also help drive Th17 differentiation.