Targeting CD44 augments the efficacy of Tregs in autoimmune diabetes

• Anti-CD44 treatment reduced pancreatic infiltrates in NOD mice.
• Anti-CD44 treatment increased the frequencies of IL-2 or TGF-β producing CD4 T cells.
• Anti-CD44 treatment delayed T1D onset in NOD mice.
• A short course of anti-CD44 treatment dramatically improved Treg therapy efficacy in T1D mouse model.

Curing type 1 diabetes (T1D) will require lasting control of the autoimmune response that destroys insulin-producing islet β-cells. Re-establishing tolerance by restoring/replacing Tregs has significant potential for treatment of T1D but will require strategies to augment and maintain their efficacy. We previously showed that polyclonal in vitro-induced Tregs can reverse recent onset of T1D in ∼50% of NOD mice. Here we report that treatment of newly hyperglycemic animals with a short course of anti-CD44 at the time of Treg transfer improved diabetes reversal to >90%. Anti-CD44 treatment alone delayed diabetes onset and increased the frequencies of pancreatic CD4+ T cells producing IL-2 or TGF-β, cytokines that support Treg function and survival, without altering production of IFN-γ. These anti-CD44 effects on endogenous T cells were also observed in the context of polyclonal Treg transfer, and the combination treatment also reduced pancreatic infiltrates. The results provide compelling evidence that approaches to modulate the pancreatic milieu to support Treg function and counteract inflammation in the pancreas can greatly enhance the efficacy of adoptively transferred Tregs, and suggest that approaches achieving these outcomes hold promise for long-term control of autoimmunity in T1D.