Herpes simplex viruses (HSV-1 and HSV-2) are widespread viral pathogens that persist in the human population by establishing latency in sensory and sympathetic ganglia after ocular, labial or genital infection, but can also reactivate to produce different patterns and frequencies of recurrent disease. Latency is maintained through epigenetic mechanisms that are dependent on continuous signaling initiated by the binding of neurotrophic factors such as nerve growth factor (NGF) or glial cell line-derived neurotrophic factor (GDNF) to cognate receptors. Recent studies have shown that signaling via GDNF is critical to maintain both HSV-1 and HSV-2 latency in cultured murine sensory and sympathetic neurons. The as yet poorly understood virus-host relationship includes changes in the expression of neuronal microRNAs, short non-coding RNAs that fine tune mRNA translation. Profiling studies in cultured rat embryonic sympathetic neurons showed that HSV-1 infection can selectively increase the levels of three closely-related and evolutionarily-conserved microRNAs (miR-183, miR-96 and miR-182) encoded by a single gene locus known collectively as miR183C. Induction occurs at the level of transcription of the precursor RNA and is mediated by the viral E3 ligase ICP0. Known mRNA targets for miR183C encode a variety of proteins that either protect cells against physiological and genomic stresses or help maintain cell type identity and at least in dopaminergic neurons, miR183C can mimic the trophic action of GDNF. In this project we will test the innovative hypothesis that viral upregulation of miR-183C helps to buffer the latent reservoir against fluctuations in GDNF signaling. To do this we will first ask whether the miR-183C locus is responsive to HSV in cultured prenatal and adult murine sensory and sympathetic ganglia (Aim 1). We will also ask if this is a shared property of HSV-2, which encodes an ICP0 ortholog (Aim 2). Finally, we will ask using gene knockouts and overexpression whether induction of miR183C can compensate for GDNF in maintaining HSV-1 latency in adult sympathetic neurons and HSV-2 latency in adult sensory neurons (Aim 3). Armed with a better understanding of the virus-host interplay in different neuronal types we hope to identify key regulatory nodes as targets for innovative therapeutic strategies to control or eliminate reactivation.

PROJECT NARRATIVE Herpes simplex virus (HSV) can establish lifelong nonproductive infections of sensory and autonomic neurons but also reactivates periodically to cause recurrent disease, affecting >250 million people in the US alone. This project tests the hypothesis that HSV alters the expression of neuronal microRNAs in order to protect host neurons and maintain persistent infections. Understanding the contribution of this virus-host interaction will enable the development of new targeted antivirals to improve clinical outcomes of herpes-associated disease.