Defining host mechanisms that restrict EBV lytic reactivation

摘要

ABSTRACT Epstein-Barr virus (EBV) is an extremely pervasive human herpesvirus, infecting approximately 95% of the global population by adulthood. EBV is transmitted through saliva and establishes infection in the oral cavity where it then establishes a latent infection for life in memory B cells. In most individuals this infection will remain benign, but EBV-associated diseases include infectious mononucleosis and cancers, more commonly in immune- compromised individuals. The balance between latent and lytic infection is under tight control and understanding the regulation of this process has broad implications for processes ranging from viral persistence in the oral mucosa to strategies to eliminate latently infected tumor cells. EBV reactivates in response to a diverse range of stressors including DNA damage, hypoxia, histone deacetylase inhibitors and activation of the B-cell receptor. A pervasive phenomenon, observed both in vitro and in vivo, is that cells have a heterogenous response to lytic induction stimuli. In a fraction of cells, the virus fully reactivates, while others remain completely refractory or only partially progress through the lytic cycle leading to an abortive infection. To better understand these cell fates after EBV lytic reactivation, my lab recently completed a single-cell RNA seq experiment of resting and reactivated EBV+ B lymphoma cells. We observed differential host gene expression patterns between refractory, abortive, and productive lytic cells. This included high expression of the known EBV restriction factors MYC and STAT3 in the refractory cells, but previously unknown markers of abortive cell populations: one characterized by elevated IL-6 receptor and the other defined by pro-survival signaling through the NFB pathway. Based on our single-cell data and prior studies, I hypothesize that an EBV induced DNA damage response leads to IL-6 production, which in turn promotes an abortive, antiviral state through the IL-6 receptor and ultimately pro- survival NFB signaling. In addition to defining mechanisms of host defense from EBV reactivation, this work also has important clinical ramifications as lytic induction therapies are currently in trials for EBV-associated malignancies. Understanding host factors that restrict successful lytic reactivation could lead to more effective therapeutic strategies in the future. Furthermore, these findings could have broad implications for how other herpesviruses reactivate and how latently infected cells communicate to regulate this process.