It is generally believed that events at peripheral nervous system (PNS) nerve termini, (i.e. damage, infection, inflammation) must be relayed to neuronal soma to produce an appropriate response at the site of insult. However, axons can be centimeters to meters long, creating a signaling and trafficking conundrum for PNS neurons. How long distance transport and communication between the axon and neuronal soma is accomplished remains a fundamental question in neuroscience. Recently, a subset of mRNAs and the entire protein synthetic machinery have been identified and functionally validated in PNS axons; findings suggest that environmental stimuli induces cell soma-independent protein synthesis in axons. The central goal of this project is to determine how PNS neurons respond to events at axon termini, particularly cytokine signaling after viral infection. Specifically, this wrk will define how type I interferons (IFN) affect axonal infection by Herpes Simplex Virus type I (HSV-1), a neuroinvasive human pathogen of the alpha herpesvirus subfamily. HSV-1 first infects epithelial tissues, and newly replicated progeny invade innervating axons of PNS neurons. Infected epithelial cells release pro-inflammatory cytokines, including type I IFN, that bathe innervating nerve termini and induce host antiviral responses to control viral invasion. Preliminary data show that exposure of axons to IFN restricts retrograde axonal transport of a swine alpha herpes virus by a currently unknown mechanism. Intriguingly, axon damage also inhibits retrograde viral transport; axon damage signals compete with viral particles for the same retrograde transport machinery. Conceivably, IFN signaling may mimic the axon damage response to prevent viral access to the cell soma. The proposed study is guided by the following hypothesis: Exposure of PNS axons to interferon induces a damage response in axons, which causes an axon- specific antiviral response that restricts neuroinvasion by reducing HSV-1 transport and replication. The goals of this project are threefold: 1) Define the effect of axonal IFN treatment on retrograde transport of the human pathogen, HSV-1, using live-cell imaging of fluorescent viral particles. 2) Isolate proteins synthesized locally in axons in response to IFN treatment using metabolic labelling of newly synthesized proteins and ultra-high performance liquid chromatography (UPLC)-mass spectrometry (MS)- based proteomic analyses. 3) Identify phosphorylated axonal proteins and activated signaling pathways in axons exposed to IFN using UPLC-MS-based phospho-proteomic analyses. The proposed studies will address the knowledge gap surrounding the mechanism of long distance signaling between axon and soma in response to events at PNS nerve termini. A local response in axons represents a new paradigm for cytokine control of neuroinvasion and may prompt re-thinking about where to focus future therapeutic efforts for neuroinvasive viruses. Knowledge gained from these studies will advance our understanding of PNS antiviral mechanisms and contribute to the conception of novel antiviral strategies.
Herpes Simplex Virus type I is a ubiquitous human pathogen that invades the nervous system, persists life- long, and reactivates intermittently to cause significant morbidity and mortality in humans. This project will explore novel mechanisms that protect the nervous system from viral invasion by investigating how axons of peripheral nervous system neurons respond to inflammatory stimulators (cytokines) produced after viral infection. A local response in axons represents a new paradigm for cytokine control of neuroinvasion and may prompt rethinking about where to focus future therapeutic efforts concerning neuroinvasive viruses.
| MacGibeny, Margaret A; Koyuncu, Orkide O; Wirblich, Christoph et al. (2018) Retrograde axonal transport of rabies virus is unaffected by interferon treatment but blocked by emetine locally in axons. PLoS Pathog 14:e1007188 |
| Koyuncu, Orkide O; MacGibeny, Margaret A; Enquist, Lynn W (2018) Latent versus productive infection: the alpha herpesvirus switch. Future Virol 13:431-443 |
