Submicron ultrasound contrast agents as diagnostic agents and therapeutic vehicles in type 1 diabetes

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PROJECT SUMMARY Type 1 diabetes (T1D) is characterized by infiltration of autoreactive T cells in pancreatic islets, leading to autoimmune destruction of insulin-producing beta cells and diabetes. Initiation of autoimmunity and substantial beta cell loss may begin years prior to symptomatic onset. Therefore, there is a crucial need to develop diagnostics and therapeutic interventions directed towards this often-lengthy presymptomatic phase of T1D. Limited success has been demonstrated in clinical trials for therapeutics directed towards presymptomatic T1D. While anti-CD3 has shown promise, anti-CD3 only prevented diabetes onset in a subset of the study cohort and is not directed specifically against T cells reactive to beta cell antigens, such as insulin. An approach that has gained substantial traction in preclinical studies is the usage of peptide therapeutics to provide tolerance towards antigens targeted by autoreactive T cells. Administration of insulin peptide therapeutics in mice has been shown to prevent diabetes onset by expanding insulin-reactive regulatory T cells, which are anti-inflammatory and are essential for proper immune tolerance and regulation. Despite their therapeutic potential, insulin peptides have shown mixed results amongst different groups and have only been effectively administered via surgical implantation of an infusion pump. Therefore, optimizing therapeutic efficacy through targeted delivery and incorporation with diagnostics is warranted. This could be accomplished with ultrasound contrast agents (UCAs), which are small gas-filled bubbles that can be visualized using contrast enhanced ultrasound (CEUS) and are safe, easy to formulate, and clinically approved. A novel, submicron, ‘nanobubble’ ultrasound contrast agent has been developed and prior work has demonstrated enhanced accumulation of nanobubbles in islets of mice with presymptomatic T1D as a result of inflammation-associated microvascular permeability. My overall goal is to develop and apply submicron UCAs to both target therapeutic agents specifically to the disease site and track the effect of therapeutics on T1D progression. I hypothesize that submicron UCAs can be applied to both predict therapeutic induced disease prevention and as vehicles for targeted peptide delivery. I will examine this via two specific aims: I aim 1, I will predict therapeutic-induced disease prevention using submicron UCAs, using CEUS to detect changes in islet accumulation of submicron UCAs following therapeutic intervention. In aim 2, I will apply UCAs as therapeutic peptide delivery vehicles. Preliminary data indicates that peptide can be incorporated into nanobubbles and nanobubbles can target peptide to islets. I will characterize effect of nanobubble ablation on peptide cellular uptake characterize dynamics of peptide-nanobubble islet extravasation, and assess immunological and disease-modifying effects of peptide-nanobubble treatment. Developing an agent that allows for accumulation of therapeutic peptides in islets, enhanced therapeutic efficacy, and disease- reversal-predicting diagnostics can serve as a major advancement in T1D prevention.