A noncanonical STING-dependent IFN-I independent pathway against KSHV reactivation

About This Grant

Project Summary Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic virus that causes two deadly cancers: Kaposi sarcoma and primary effusion lymphoma. KSHV establishes lifelong latent infections in humans, and this is irreversible due to the lack of a vaccine or curative treatment options. Moreover, KSHV can reactivate into the lytic phase to produce infectious virions, posing a continuous transmissible oncogenic threat worldwide. Despite its significant impact on human health, host mechanisms that restrict reactivation remain poorly understood, limiting the development of strategies to prevent viral spread and associated cancers. The cGAS/STING pathway is essential for broad antiviral innate immunity, and STING agonists robustly block KSHV reactivation. Canonically, STING activates IRFs to induce type I interferons (IFN-I) for antiviral responses; however, KSHV encodes multiple inhibitors that suppress IFN-I production, suggesting the existence of an alternative host defense pathway under IFN-I deficiency. Excitingly, our preliminary data reveal a previously unrecognized STING-dependent, IFN-I-independent mechanism that restricts KSHV reactivation. Using stringent genetic models, we identified IRF transcription factors and a subset of interferon-stimulated genes (ISGs) as critical mediators of this pathway. The long-term goal of this project is to delineate antiviral mechanisms of the STING pathway and identify new therapeutic strategies to limit KSHV-associated cancers. The overall objective of this R21 is to define the molecular components and functional relevance of the STING-dependent, IFN-I-independent pathway. We propose two specific aims: (1) define the roles of IRF transcription factors in inducing ISGs via this noncanonical pathway using IFNAR1 knockout KSHV-infected cells and STING agonists, and (2) identify and validate direct ISGs that restrict KSHV reactivation under IFN-I deficiency using RNA-seq and functional knockdown assays. Successful completion of this study will provide mechanistic insight into a noncanonical STING-dependent host defense, identify novel antiviral targets, and generate the foundation for a future R01 investigating broader innate immune pathways and therapeutic strategies. Moreover, because many viruses suppress IFN-I production as an immune-evasive strategy, these findings will reveal a broadly relevant host defense strategy against diverse viral pathogens.