Effect of combined low dose IL-2 and polyclonal Tregs infusion in Type 1 Diabetes patients

Background

IL-2 is a well characterized cytokine that drives the expansion of activated human T cells. Its mechanism of action involving the high affinity receptor CD25 confers to IL-2 a crucial role in the homeostasis and function of regulatory T cell (Treg) basally expressing CD25. It has been suggested that low doses of IL-2 treatment in vivo, selectively expands Tregs without altering effector T cell or NK populations. This preferential targeting is key to cell-based immunotherapeutics that aim to prevent autoimmunity such as Type 1 Diabetes.

Methods

A phase I protocol was initiated to treat recently diagnosed T1D patients with a single infusion of ex-vivo expanded autologous polyclonal Tregs followed by two 5-days courses of low-dose IL-2. Patients were monitored for safety and diabetes-related metabolic profiles. PBMCs were analyzed at different time points by CyToF and 10X genomic single-cell RNAseq to monitor T cell activation.

Results

The overall safety profile was excellent but all 9 patients treated with the combined therapy failed to maintain c-peptide production at pre-treatment levels. We observed an expansion of Tregs and granzyme B (GZMB)+ NK subsets. More interestingly, single cell T cell receptor and gene expression sequencing allowed us to detected in all the patients a population of (GZMB)-producing CD8+ T that expanded clonally after IL-2 treatment.

Conclusion

These data suggest that the usage of low-dose IL-2 together with polyclonal Tregs infusion exacerbate the expansion of Tregs but also of a GZMB+ CD8+ T cells and NK population already present in blood. Thus, the failure for all patients to maintain C-peptide level may be due to a shift of the immune balance toward activation rather than tolerance.

The miR-17-92 cluster is essential for regulatory T cell function in vivo (168.14)

microRNAs (miRNAs) are posttranscriptional regulators of the proteome. We have identified CD28-responsive miRNAs in human CD4+ T cells. Among others, the miR-17-92 cluster was of particular interest because abnormal miR-17 levels have been reported in peripheral blood mononuclear cells from patients with multiple sclerosis. When activated with low CD28-costimulation the miR-17-92 cluster was necessary to drive maximal proliferation in conventional mouse CD4+ T cells (Tconv) in vitro. However, the miR-17-92 cluster was largely dispensable for total T cell numbers in secondary lymphoid tissues and for antigen-response in vivo. Since FoxP3+ regulatory T cells (Treg) are strongly co-stimulation dependent we deleted the miR-17-92 cluster specifically in Treg. Preliminary data suggest that as for Tconv the miR-17-92 cluster was dispensable for Treg numbers and function under homeostatic conditions, even in aging mice. By contrast, mice with miR-17-92-deficient Treg develop much more severe experimental autoimmune encephalitis than control mice. Preliminary results suggest that miR-17-92-deficient Treg numbers are significantly reduced in the spinal cord while antigen-specific effector cells are present in normal numbers. We are currently investigating how miR-17-92 mediates this crucial function. Our results demonstrate that miRNAs are critical for optimal T cell co-stimulation via CD28. The miR-17-92 cluster is essential for Treg function under inflammatory conditions in vivo.

Transcriptional profile of CD28 costimulation and Dec1 relevance in T-cell activation (113.14)

Antigen recognition by the T cell receptor and costimulatory signal through CD28 receptor are required for a complete T-cell activation. CD28 ligation regulates a wide range of biochemical processes that drive T-cell proliferation, prevent apoptosis and enhance IL-2 production. However, the direct effect of CD28 signaling on the global gene transcription after T-cell activation remains controversial. We described the transcriptional profile of CD28 costimulation employing microarray analysis of human naïve CD4+ T cells. Although we demonstrated that CD28-dependent signaling had quantitative effects on gene expression during the first stages of activation, strong qualitative changes on transcription were observed by 24 hours after activation. Among the genes directly induced by CD28 costimulation we identified the transcription factor Dec1. We described the critical role of Dec1 for the transcriptional response to CD28 costimulation in both Jurkat T cells and primary mouse CD4+ T cells. Importantly, we showed that the effects of Dec1 deficiency impact specifically on CD28 costimulation-dependent gene expression. Further, we proved that Dec1 is necessary to induce experimental autoimmune encephalitis in mice after MOG peptide immunization. This observation validates the in vivo importance of Dec1 for immune system function in a CD28-dependent disease.