Transcriptomic and Metabolic Heterogeneity During Epstein-Barr Virus Latency Establishment
Epstein-Barr Virus (EBV) is a ubiquitous gamma-herpesvirus in the human population and highly associated with lymphomas of the immune-suppressed. EBV maintains itself within the human host via temporal regulation of viral gene expression before establishing latency in resting memory B cells. Experimentally, we can model these immune-compromised lymphomas via in vitro infection of B cells isolated from peripheral blood. This infection model is biphasic where the initial phase is characterized by hyper-proliferation and expression of the EBV nuclear antigens (EBNAs) in the absence of the latent membrane proteins (LMPs) called latency IIb before transitioning to the NFkB-dependent latency III lymphoblastoid cell line (LCL) stage characterized by full expression of the LMPs in the presence of the EBNAs. This temporal regulation manipulates host cell proliferation rates and metabolic profiles of infected B lymphocytes. Our laboratory and my studies, in particular, are focused on the latency IIb to latency III transition as these states are often observed in patient biopsies of EBV-associated malignancies.
Latent membrane protein 1 (LMP1) expression defines latency III and has been used in lymphoma samples to identify EBV latency III in vivo. While LMP1 expression is lower in latency IIb, the mechanism by which it is repressed is currently unknown. Additionally, while LMP1 expression can be used to distinguish latency IIb from latency III, LMP1 expression varies widely within latency III and a subset of LMP1lo latency III cells express LMP1 at levels similar to latency IIb making these cells hard to distinguish in vitro and in vivo. Lastly, while EBV manipulates host cell metabolism, the viral and host factors important for metabolic rewiring have not been fully elucidated.
Using RT-qPCR, ChIP-qPCR, RNA-sequencing, Western Blotting, flow cytometry, and bioinformatic approaches we have identified c-Myc as a repressor of LMP1 during latency IIb. We have also identified host mRNA biomarkers capable of distinguishing latency IIb from latency III. This discovery was additionally leveraged to develop a multiplex RNA-FISH platform capable of distinguishing latency IIb from latency III. Lastly, we have identified host and viral proteins necessary to rewire host cell metabolism and sustain EBV-mediated B cell proliferation. This work, taken together, adds new understanding to EBV latency establishment, heterogeneity, and host B cell biology to develop new, more targeted, therapeutics for EBV-associated lymphomas in the future.
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