Dissecting the Role of Endogenous Retroviruses in Type 1 Diabetes Progression - Abstract. Type 1 diabetes (T1D) arises from autoimmune destruction of pancreatic beta cells, yet the upstream molecular events that heighten beta cell vulnerability and trigger autoreactive T-cell responses remain poorly understood. Emerging evidence suggests that human endogenous retroviruses (hERVs), ancient viral elements comprising ~8% of the human genome, may act as upstream amplifiers of innate immune activation, beta cell stress responses, and antigen presentation. In our preliminary studies, single-cell long-read sequencing of human islets revealed a global increase in hERV expression in T1D, with several beta cell–enriched hERVs tightly correlated with inflammatory, viral-response, and antigen-presentation pathways. Building on these findings, this proposal will leverage human islets, hPSC-derived vascularized immune islet (VII) organoids, T cell–organoid co-culture systems, and humanized mouse models to systematically evaluate how T1D- upregulated hERVs influence beta cell identities, inflammation status, antigen presentation, and downstream T- cell activation. We will test the hypothesis that T1D-associated stressors, including viral infection and cytokine exposure, activate hERV activation, which in turn drives beta cell inflammation, increases antigen presentation, and promotes autoimmune T-cell responses. Aim 1 will define the regulatory landscape governing hERV activation in human beta cells during T1D progression by integrating single-cell long-read transcriptomics, chromatin accessibility profiling, spatial transcriptomics, and functional perturbation of hERV regulatory elements using CRISPRi and region-specific knockouts. Aim 2 will determine how hERV activation reshapes beta cell identity, function, stress responses, and inflammatory signaling using hPSC-derived islet and VII organoids with precise hERV overexpression or knockdown. Aim 3 will establish whether hERV activation enhances beta cell antigen presentation and increases susceptibility to cytotoxic attack by polyclonal and autoantigen-specific human CD8⁺ T cells, using co-culture assays. Together, these studies will provide the first mechanistic dissection of how hERVs integrate cytokine and viral cues, remodel beta cell states, and potentiate autoreactive T-cell responses in human T1D. By identifying early, targetable pathways upstream of beta cell destruction, this work has the potential to reveal new biomarkers and therapeutic strategies to preserve beta cell function and prevent T1D progression.
