Induction of stable human FOXP3+ Tregs by a parasite-derived TGF-β mimic

Objectives. Immune homeostasis in the intestinal tract is tightly controlled by FOXP3+ regulatory T cells (Tregs), with loss of this Treg-mediated control linked to development of chronic conditions, such as inflammatory bowel disease (IBD). As a mechanism of immune evasion, several species of intestinal parasites strengthen intestinal Treg activity, leading to the notion that parasite-derived products could be harnessed and used as an immunoregulatory therapy for IBD. It has been previously demonstrated that the parasite Heligmosomoides polygyrus secretes a molecule (Hp-TGM) which mimics the ability of TGF-β to induce FOXP3 expression in CD4+ T cells. Our aim was to investigate whether Hp-TGM could induce human FOXP3+ Tregs as a potential therapeutic approach. Methods. Human CD4+ T cells from healthy volunteers were expanded in the presence of Hp-TGM or mammalian TGF-β. The induction of Tregs was measured by flow cytometric detection of FOXP3 and other Treg markers, such as CTLA-4 and CD25. Epigenetic changes were detected using ChIP-Seq and pyrosequencing of FOXP3. Treg phenotype stability was assessed following inflammatory cytokine challenge and Treg function was assessed by cellular co-culture suppression assays and secreted cytokines measured by cytometric bead array. Results. Hp-TGM efficiently induced FOXP3 expression (>60%), in addition to another Treg functional marker CTLA-4. Hp-TGM caused epigenetic modification of the FOXP3 loci to a greater extent than did TGF-β. Hp-TGM-induced Tregs also had superior suppressive function compared to TGF--induced Tregs, and retained their phenotype following exposure to inflammatory cytokines. Hp-TGM also induced a Treg phenotype in in vivo differentiated Th17 cells, indicating its potential to re-program memory cells to enhance immune tolerance. Conclusion. These data indicate Hp-TGM has the potential to be used to generate stable human FOXP3+ Tregs to treat IBD. Examination of H3K27Ac in TGFbeta or TGM primed human CD4 T cells