Research Project 1: Role of Epigenetic and Transcriptional Mechanisms in the Pathogenesis of Ebola Virus Disease

RESEARCH PROJECT 1 (RP1): PROJECT SUMMARY/ABSTRACT Pathogenesis of the disease caused by Ebola virus (EBOV) is characterized by a multifaceted and contradictory interplay between the virus and the host. The effect of EBOV infection is characterized by deficient T-cell responses and lymphopenia, which at least in part results from stimulation by virus-infected dendritic cells whose maturation is suppressed by interferon-inhibiting domains of the virus. In addition, EBOV infections are characterized by hyperinflammation, contributed by interaction of the EBOV envelope glycoprotein (GP) with TLR4 on T cells and possibly by other mechanisms, resulting in massive secretion of cytokines. This dysregulated immune response results from disruption of transcriptional networks, many caused by alterations in the epigenome, as evidenced by (1) chemical inhibition of type 1 topoisomerase resulting in reduced expression of proinflammatory mediators induced by EBOV in infected cells, (2) inhibition of TLR4 signaling, which is regulated at epigenetic level, promoting survival of EBOV-infected mice, and (3) treatment of EBOV- infected mice with a global histone methylation inhibitor that upregulates production of IFNα and protects animals from death. The central hypothesis of Research Project 1 (RP1) is that cell-specific and gene-specific regulation of transcription in response to EBOV infection leads to contrasting responses that paradoxically cause a pathogenic immune response and "immune paralysis". To address this hypothesis, the epigenetic and transcriptional landscape during EBOV infections in vitro and in vivo will be characterized. A comprehensive analysis of the transcriptome alterations and epigenetic changes caused by EBOV infection will be performed in both human primary cells and specific cell types isolated from infected nonhuman primates. Investigations involving the expression of mRNAs that encode transcription factors will be done to determine the deposition of epigenetic marks and their role in gene activation and repression, as well as investigating the effects of chromatin accessibility on expression and secretion of inflammatory mediators using cells from human donors. This project will target key transcriptional nodes identified by modeling EBOV infection. The data generated in vitro and in vivo, together with data from in RP2 and RP3, will be integrated by the Bioinformatics and Modelling Core (Core D) in a model. The transcriptional networks identified in the model will predict critical nodes that represent vulnerabilities that will be targeted to modulate cell response and reduce EBOV pathogenesis. For example, chromatin-resident enzymes and transcription factors that induce expression of genes causing inflammation and other pathological changes will be targeted. The study will result in the characterization of epigenetic and transcriptional responses to EBOV; to date no epigenetic response to any BSL-4 level virus has been characterized. The study will also result in the development of approaches to treat EBOV disease by targeting host transcriptional and epigenetic functions.