Insulin B:9-23 peptide-nanobubbles target islets, expand regulatory T cells, delaying T1D onset.

Type 1 diabetes (T1D) is an autoimmune disease characterized by autoreactive T cells destroying pancreatic beta-cells. Current antigen-specific immunotherapies using tolerogenic peptides aim to induce peripheral tolerance but have struggled with clinical efficacy, often due to challenges in targeted delivery and maintaining sufficient local concentrations. This research addresses the need for an image-guided platform to precisely deliver tolerogenic peptides to pancreatic islets, enhancing local immune modulation and improving therapeutic outcomes.

Researchers developed submicron-sized peptide-nanobubbles (NBs) as an image-guided delivery system for tolerogenic peptides in mouse models of T1D. They incorporated an insulin B:9-23 peptide mimotope into NBs, designed to passively accumulate in pancreatic islets of non-obese diabetic (NOD) mice due to increased microvascular permeability. The study also evaluated NBs prepared with a hybrid insulin peptide (HIP) in an adoptive transfer mouse model. Accumulation was monitored using contrast-enhanced ultrasound, and the primary endpoint was the expansion of islet-resident regulatory T cells and delay of diabetes onset.

Peptide-nanobubbles (NBs) successfully retained their normal size distribution and acoustic properties after peptide incorporation, confirming their stability. Upon administration, peptide-NBs demonstrated significant accumulation within the pancreatic islets of NOD mice, a process that was visually confirmed in real-time using contrast-enhanced ultrasound. This targeted delivery led to an increased proportion of islet insulin-reactive regulatory T cells, indicating a localized immunomodulatory effect. The abstract does not provide specific quantitative data on the magnitude of T-cell expansion or diabetes delay. However, the qualitative findings are clear. > Furthermore, NBs formulated with a hybrid insulin peptide (HIP) specifically expanded islet HIP-reactive regulatory T cells and substantially delayed the onset of diabetes in an adoptive transfer mouse model of autoimmune diabetes. These findings highlight the potential for precise, image-guided delivery to enhance the efficacy of antigen-specific immunotherapy by concentrating tolerogenic peptides at the site of autoimmune attack, thereby promoting peripheral tolerance.