Deciphering the Interplay of Depleting Anti-PD-1 Antibodies and Autoimmune Environments in Type-1 Diabetes: Towards Better Utility of Therapeutic Antibody

About This Grant

PROJECT SUMMARY This project aims to investigate the interactions and impacts between a depleting antibody (D-aPD-1) that targets programmed death-1-expressing (PD-1+) cells and the autoimmune environment in type 1 diabetes (T1D). PD- 1+ cells are primarily effector lymphocytes that are diabetogenic in T1D.These PD-1+ cells could be a potential target for suppressing autoimmunity in T1D. Initial studies demonstrated that eliminating PD-1+ cells with a PD- 1-specific immunotoxin delayed hyperglycemia onset in NOD mice with late insulitis (L-insulitis). However, immunotoxins are not ideal for chronic disease management, leading to the development of D-aPD-1 as an alternative. Interestingly, when administered to mice with early insulitis (E-insulitis), D-aPD-1 delayed hyperglycemia onset, suggesting a protective effect. However, when given to L-insulitis mice, it unexpectedly accelerated hyperglycemia onset, indicating a pro-autoimmune response. Furthermore, unlike D-aPD-1, PD-1 immunotoxin delayed hyperglycemia onset in L-insulitis mice. These findings align with clinical observations that disease stages and therapeutic agens influences treatment outcomes, highlighting the need to elucidate the mechanisms driving these contrasting responses for better desing and application of T1D therapeutics. To address these questions, this project will investigate the hypothesis that both the immune milieu of T1D and the characteristics of PD-1+ cell-depleting agents play key roles in determining treatment outcomes. Aim 1 will uncover the immune determinants of D-aPD-1’s divergent treatment outcomes in E and L-insulitis by profiling pancreatic islets and systemic immune cells before and after D-aPD-1 treatment. We will use single-cell RNA sequencing (scRNA-seq) and flow cytometry to dentify changes in immune cell populations and pathways associated with pro- and -anti-autoimmune effects. Additionally, strategies to shift L-insulitis responses toward an E-insulitis-like profile will be explored through modulate certain immune cell types. Aim 2 will define the mechanism underlying differential responses to D-aPD-1 and PD-1 immunotoxin by comparing immune cell dynamics and gene expression changes following the treatments. We will identify key cellular mediators responsible for the pro-autoimmune response induced by D-aPD-1, while also investigating whether depleting these responsive cell populations can mitigate its adverse effects. Aim 3 will establish that Fc-free PD-1+ cell depleting agents protect L-insulitis mice from hyperglycemia. Specifically, we will assess whether the Fc-free PD-1+ depleting agents, including albumin-amended antibody-drug conjugate (A3DC) and bispecific killer cell engager (BiKE), can eliminate PD-1+ cells without triggering pro-autoimmune effects. This research could advance targeted PD-1+ cell depletion strategies, leading to safer and more effective antibody-based treatments for T1D. By addressing immune context and therapeutic design, the findings may tailor the design and application of therapeutics for T1D patients at different stages.