Many flaviviruses, including West Nile virus (WNV), Japanese encephalitis virus, tick- borne encephalitis virus and dengue virus, are significant human pathogens. No effective antiviral therapies currently exist for treating individuals with flavivirus infections and flavivirus-induced pathogenesis is not completely understood. Evidence for the existence of two Type 1 IFN- and IRF-3/7-independent cellular "backup" up-regulation pathways for subsets of interferon stimulated genes (ISG) and for a novel virus- mediated counteraction mechanism directed at suppressing protein production by a subset of antiviral ISGs have been discovered. Initial exploratory studies are proposed to define the mechanisms involved.
The specific aims are focused on gaining an initial understanding of: (1) the mechanisms responsible for the up-regulation of a subset of IRF-3/7-independent ISGs by 12 hr after infection in the absence of a canonical Type I interferon signaling pathway in WNV-infected cells and for the different regulatory mechanism required for a second subset of ISGs that show delayed activation in WNV-infected cells;and (2) the mechanism by which protein expression by the second subset of ISGs is suppressed in WNV-infected cells.
Under Aim 1, we will map the critical transcription factor binding sites (TFBSs) involved in interferon-independent up-regulation of ISGs in the promoters of model ISGs that are rapidly up-regulated and those that show delayed up-regulation in WNV- infected cells. The functional relevance of the mapped TFBSs will be tested by mutagenesis and by in vitro and in vivo DNA-protein interaction assays. Transcription factors binding to the mapped TFBSs will be identified by MassSpec sequencing of proteins obtained by DNA pull-down.
Under Aim 2, the contributions of ISG mRNA stability, cell RNA binding proteins and cell miRNAs in reducing protein levels expressed by a subset of ISGs in WNV-infected cells will be investigated. A detailed understanding of these mechanisms will increase knowledge about the complexity of the host innate response to virus infection and about a novel viral counteraction mechanism. Delineation of the viral counteraction mechanism will provide a new cell target for the development of antiviral therapeutics that may be applicable to a broad spectrum of virus infections.

Public Health Relevance

Many flaviviruses, such as West Nile virus, tick-borne encephalitis virus, and dengue virus, are human pathogens causing significant human morbidity and mortality in ever expanding regions of the world. No effective anti-flaviviral therapies currently exist. We propose to analyze two novel Type 1 interferon- and IRF- 3/7-independent pathways for activating host innate antiviral genes in infected cells and a novel mechanism of viral counteraction of host innate responses recently discovered by our lab. A detailed understanding of these mechanisms will increase knowledge about the host innate response to virus infection and viral virulence.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Exploratory/Developmental Grants (R21)
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Virology - B Study Section (VIRB)
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Repik, Patricia M
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Georgia State University
Schools of Arts and Sciences
United States
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