Antigen-Encoding Bone Marrow Terminates Islet-Directed Memory CD8+ T-Cell Responses to Alleviate Islet Transplant Rejection

Abstract

Islet-specific memory T cells arise early in type 1 diabetes (T1D), persist for long periods, perpetuate disease, and are rapidly reactivated by islet transplantation. As memory T cells are poorly controlled by "conventional" therapies, memory T cell-mediated attack is a substantial challenge in islet transplantation, and this will extend to application of personalized approaches using stem cell-derived replacement b-cells. New approaches are required to limit memory autoimmune attack of transplanted islets or replacement b-cells. Here, we show that transfer of bone marrow encoding cognate antigen directed to dendritic cells, under mild, immune-preserving conditions, inactivates established memory CD8 + T-cell populations and generates a long-lived, antigen-specific tolerogenic environment. Consequently, CD8 + memory T cell-mediated targeting of islet-expressed antigens is prevented and islet graft rejection alleviated. The immunological mechanisms of protection are mediated through deletion and induction of unresponsiveness in targeted memory T-cell populations. The data demonstrate that hematopoietic stem cell-mediated gene therapy effectively terminates antigenspecific memory T-cell responses, and this can alleviate destruction of antigen-expressing islets. This addresses a key challenge facing islet transplantation and, importantly, the clinical application of personalized b-cell replacement therapies using patient-derived stem cells.

APC‐targeted proinsulin expression inactivates insulin‐specific memory CD8+ T cells in NOD mice

“…These observations indicate ‘adaptive tuning’ of residual undeleted insulin‐specific CD8 + Tmem to the proinsulin expressed in PI‐Tg recipients. An unexpected finding was that CD5, which is an indicator of antigen‐sensing 39 and upregulated by tolerant T cells in many settings, 26 , 40 was not upregulated by inactivated G9 Tmem in PI‐Tg recipients. This could perhaps reflect altered regulation of CD5 in Tmem, particularly as CD5 expression was reduced during in vitro Tm differentiation ().…”

“…Certainly, transfer of genetically modified haematopoietic stem cells shows that gene therapy has the potential to be an effective treatment 26,44,45 and this is capable of preventing recurrent autoimmune attack of transplanted islets. 26 Here we found no inflammatory infiltrates in pancreatic islets of PI-Tg recipients of G9 Tmem, even after immunisation (e.g. Figure 4) or CTL (e.g.…”

“…One key component of tolerance induction by enforced antigen expression is persistent exposure to antigen, 44 making gene therapy approaches that achieve long-term antigen expression highly applicable. Certainly, transfer of genetically modified haematopoietic stem cells shows that gene therapy has the potential to be an effective treatment 26,44,45 and this is capable of preventing recurrent autoimmune attack of transplanted islets. 26 Here we found no inflammatory infiltrates in pancreatic islets of PI-Tg recipients of G9 Tmem, even after immunisation (e.g.…”

“…We employed an in vitro differentiation procedure 17 where G9 T cells were activated in the presence of cognate antigen (insB [15][16][17][18][19][20][21][22][23] ) and IL-2 for 3 days and then washed and recultured in IL-15 to induce central memory differentiation. We have previously validated memory T cells (herein termed Tmem) generated using this and similar procedures in tolerance and other studies 17,19,26 and their behaviour is similar to in vivo-derived memory cells. 17 During in vitro differentiation, G9 T cells underwent blastogenesis and acquired high levels of CD44 expression during insB [15][16][17][18][19][20][21][22][23] and IL-2 stimulation (Supplementary S1A and B).…”

Allergen-encoding bone marrow transfer inactivates allergic T cell responses, alleviating airway inflammation

“…Effective engraftment and establishment of hematopoiesis by the transferred HSPC is required for the continued genesis of antigen-expressing APC in order to generate a long-lived tolerogenic state in recipients. While, thymic mechanisms might prevent emergence of de novo antigen-specific T cells, the antigen-expressing APC that develop inactivate existing populations of antigen-specific T cells through peripheral tolerance mechanisms (27), and this has been demonstrated to extend to pathogenic CD8 + T cells (31). Whereas others have shown that expression of allergen by BM-derived cells can induce T cell and B cell tolerance in recipients of gene-engineered BM cells, this has been tested only under harsh, fully immunoablative conditions (43) where central tolerance mechanisms that influence development of naive lymphocyte populations may predominate.…”