Defining the Mechanisms of Epstein-Barr Virus Persistence and Recurrence

ABSTRACT Our ultimate goal to define the molecular mechanisms for EBV latency establishment and reactivation in the oral cavity. In this proposal, we aim to characterize how EBV usurps B-cell maturation programs for cell survival and the establishment of a continuum of cell states balancing latency-driven proliferation, differentiation, and lytic reactivation. It is our central hypothesis that EBV establishes B-cell latent infection through mimicry of the germinal center (GC) reaction and subsequently promotes a continuum of activation and differentiation that is balanced to enable access to a cell state supporting lytic reactivation. We have formulated our central hypothesis based on preliminary data including single-cell gene expression, chromatin conformation of tonsillar B cells and EBV-immortalized cells as well as characterization of new spontaneously lytic strains of EBV. We found that EBV latent infection promotes GC mimicry through temporal regulation of anti-apoptotic MCL-1 and BFL-1. Using scRNA-seq of LCLs, we discovered a continuum of gene expression where NFB signaling/activation (e.g. NFKB2, MYC, IRF8) is strongly anti-correlated with plasmablast differentiation (e.g. CD38, PRDM1, XBP1). Furthermore, EBV lytic genes were expressed in cells most similar to the high differentiation state suggesting a model whereby EBV-infected cells constantly sample this differentiated state to enable a switch to lytic reactivation. Finally, using new strains of EBV we describe a paradigm of a persistent, spontaneous switch to productive infection that is transient and reversible. Therefore, the rationale for this proposed research is that understanding how EBV establishes latency and reactivates to productive infection provides insight into therapeutic modalities to eliminate EBV-infected cells from the oral cavity. The underlying molecular circuitry controlling these cell fate decisions may also provide important new information regarding the plasticity of B-cell maturation states. 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 mechanisms by which EBV promotes B-cell survival mimicking tonsillar B-cell maturation, ii) to define the underlying molecular circuitry supporting a novel activation/differentiation continuum within individual EBV-immortalized B cells, and iii) to define the biochemical and cell biological features of a newly described EBV recurrence phenotype in which latently infected cells produce virions and return to their basal latent state.