Defining the mechanisms of Epstein-Barr virus persistence and recurrence

About This Grant

ABSTRACT Epstein-Barr virus (EBV) is a latent, recurring herpesvirus that replicates in the oral cavity and is transmitted by saliva. While most infections are relatively benign, EBV can cause malignancies in the immune suppressed, such as transplant patients and HIV-infected individuals, and is also a potential trigger for certain autoimmune diseases. In addition, rare germline genetic variants lead to increased susceptibility to EBV- associated diseases. EBV is a highly successful virus with nearly 95% of adults worldwide being latently infected. This efficiency is due to the unique and evolutionarily conserved ability of EBV to mimic B cell signaling pathways and evade the innate immune response. The balance of these activities determines whether EBV is successful in establishing latency and in some genetic backgrounds, the consequences range from autoimmunity to cancer. It is therefore our ultimate goal to define the molecular mechanisms for EBV latency establishment and persistence in the oral cavity. In this proposal, we aim to characterize how EBV evades innate immune signaling and usurps intrinsic B-cell signaling to promote latency establishment and pathogenesis. It is our central hypothesis that EBV establishes B-cell latent infection through antagonizing innate immune signaling and mimicry of constitutive B-cell signaling pathway activation. We have formulated our central hypothesis based on preliminary data including a CRISPR screen following up on our recent early infection scRNA/ATACseq experiments in primary human B cell infection leading to mechanistic studies demonstrating a positive role for the ubiquitin like molecule, ISG15, and restrictive roles for BCR signaling regulators in EBV-driven B cell immortalization. We further found that ISG15 acts as a regulator of type I interferon signaling such that ISGylation enzymes were suppressors of B cell outgrowth and STAT1/2 or IFNAR1/2 loss rescued ISG15 loss. Excitingly, we also identified patients with poor control of EBV harboring deleterious variants of these EBV regulators suggesting that our CRISPR screen identified clinically relevant molecules as arbiters of EBV infection in vivo. Therefore, the rationale for this proposed research is that understanding how EBV regulates innate immune and BCR signaling to establish latency and transform B cells provides insight into therapeutic modalities to eliminate EBV-infected cells from the oral cavity. We plan to test our central hypothesis and complete the objectives in this proposal through the following three specific aims: i) to determine the molecular mechanism by which EBV regulates type I interferon signaling to promote latency establishment and tumorigenesis, ii) to determine the unique role of B-cell receptor signaling regulators in EBV transformation and tumorigenesis, and iii) to determine the mechanistic roles of rare germline variants in regulatory genes from patients with EBV-associated diseases impacting ISGylation, signaling, and B cell fate decisions.