Enhancement of antigen-specific Treg vaccination in vivo

Abstract

The conversion of naive T cells into Treg can be achieved in vivo by delivery of antigen under subimmunogenic conditions. Here we have examined several drugs for their ability to enhance the conversion process in vivo and have found that the rapamycin analog everolimus potently enhances Treg conversion by interfering with T-cell costimulation, reducing cell division and thereby activation of DNA methyltransferase 1 as well as by reducing T-cell activation through the ATP-gated P2×7 receptor controlling Ca2 + influx. The resulting Tregs exhibit increased stability of Foxp3 expression even when generated in TGFβ-containing media in vitro. Thus the mammalian target of rapamycin (mTOR) inhibitor everolimus in addition to inhibiting immune responses enhances Treg conversion by several distinct pathways. The converted Tregs can be further expanded by injection of IL-2/IL-2ab complexes. These complexes also increase the number of CD25 + Foxp3 − cells that, however, do not represent cytokine secreting effector cells but anergic cells, some of which can secrete IL-10 and can themselves be considered regulatory T cells as well. The combined use of everolimus and IL-2/IL-2ab complexes in vivo makes it feasible to achieve highly effective antigen-driven conversion of naive T cells into Treg and their expansion in vivo and thereby the described protocols constitute important tools to achieve immunological tolerance by Treg vaccination.antigen-specific Treg conversion | Foxp3 | IL-2/IL-2ab complexes | mammalian target of rapamycin | prospective tolerance A t present it is unclear how much the conversion of naive T cells into Treg in peripheral lymphoid tissue contributes to the control of immunity by Treg. On the other hand, it seems reasonable to exploit this conversion process to control unwanted immune responses. In the past our lab has described several strategies to induce such conversion by exogenous antigens with the aim to study whether Treg conversion can be used to induce tolerance to antigens, including transplantation antigens, prospectively (1-3). We were successful in using this approach to induce prospective tolerance in female mice to a variety of male tissues, including skin and hematopoetic grafts (4).With regard to mechanisms it became clear that Treg conversion in vivo is best achieved by subimmunogenic delivery of strong agonists under conditions that avoid functional activation of antigen presenting cells (5-9). Also, in accordance with more recent data (10), in this setting, best conversion is seen in T cells that undergo only limited proliferation, whereas higher doses of the strong agonist result in more extensive proliferation and diminished conversion (5). Thus these studies that addressed Treg conversion by monitoring the generation of Foxp3-expressing Treg in vivo confirmed anecdotal evidence of generating "dominant" tolerance by subimmunogenic antigen delivery (10).Comparison of such converted Treg with Treg generated by T-cell stimulation in vitro in the presence of relatively high doses of tran...

DEC205+ Dendritic Cell–Targeted Tolerogenic Vaccination Promotes Immune Tolerance in Experimental Autoimmune Arthritis

“…Recombinant anti-DEC205 Abs fused to disease-relevant autoantigens have been developed and used successfully for tolerogenic protection in autoimmune disease models, including autoimmune diabetes (24,26) and EAE (14,18,25). In the present study, we show that administration of a single dose of recombinant anti-DEC205 Ab fused to the cartilage-derived immunodominant PG 70-84 efficiently ameliorates the severity of PG-induced arthritis.…”

“…DEC205 + DC-targeted dominant tolerance can be achieved by the Ag-specific enhancement of Foxp3 + regulatory T cell (Treg) activity (15-18, 24, 25), whereas recessive tolerance mechanisms include deletion and induction of anergy in pathogenic T cells (13,14,18,24). DEC205 + DC targeting has been shown to promote immune tolerance in the spontaneous NOD mouse model of autoimmune diabetes (24,26) and peptide-induced mouse models of experimental autoimmune encephalomyelitis (EAE) (14,18,25). Compared to peptide-induced autoimmune models such as EAE, PGIA is fundamentally different because disease is induced with whole protein, namely human cartilage-derived PG.…”

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

“…Because administration of peptide Ag together with immunomodulatory reagents favors the induction of Ag-specific Tregs in vivo (32,53,54), we assume it should be desirable to include islet Ag peptide in the combination, and indeed such a combination promoted significant Ag-specific Treg expansion in the spleens and pancreatic lymph nodes (Fig. 2B, 2C).…”

“…The administration of IL-2/anti-IL-2 mAb (clone JES6-1) complexes in vivo has been shown to increase polyclonal Treg numbers in lymphoid organs (29). It has also been reported that the mammalian target of rapamycin inhibitor rapamycin can selectively inhibit proliferation of CD4 + effector T cells, enhance the expansion of Tregs (30,31), and maintain the stability of expanded Tregs (32,33). Therefore, we hypothesized that a combined treatment comprising an islet Ag (BDC2.5 cognate mimetope), IL-2/IL-2 mAb complexes, and rapamycin could act in synergy to expand Ag-specific Tregs in lymphoid organs.…”

Immunotherapy in Autoimmune Type 1 Diabetes

“…Recognition of agonist TCR ligand works as a key element for the initiation of Treg cell generation, a developmental program which can run intra- [93,94] or extrathymically [95][96][97][98][99][100]. Studies on extrathymic Treg cell generation in the peripheral adult immune system can have an important therapeutic potential.…”