Herpes simplex virus 1 (HSV-1) is a double-stranded DNA virus, often acquired during childhood, that currently infects more than 50% of the human population. The symptoms of infection are herpetic lesions that frequently appear throughout a host's life in response to stress in the orofacial or genital region. As a pathogen, HSV-1 replicates rapidly in epithelial cells, but it is also capable of infecting neurons where it can pursue a lytic or latent infection. Latency is a state of viral quiescence where the virus can persist indefinitely yet remain poised to reactivate. Latency is unique to herpesviruses and key to HSV's success, but the molecular mechanisms that govern this state are unclear. A virus-encoded E3-ubiquitin ligase, Infected Cell protein 0 (ICP0), is often correlated with latency establishment but is detected in opposition to the state of latency. During lytic infection, ICP0 has many biological roles but primarily catalyzes the addition of ubiquitin to target substrate, marking proteins for degradation or altering their function. This ubiquitination ability allows ICP0 to alter the intracellular environment making neurons conducive to lytic or latent HSV-1 infection. ICP0's neuron-specific targets, however, are unknown, representing a significant gap in knowledge. Through the studies presented in this dissertation, we identified some of the neuron-specific ubiquitination targets of ICP0 in neurons. We utilized primary adult sensory neurons of the dorsal root ganglia and HSV-1 viral strains KOS, wild-type virus encoding a fully functional ICP0, and HSV-1 n212, encoding a truncated ICP0 protein, to illuminate the mechanisms involved in establishing and maintaining HSV latency. By using adult primary neurons and functional HSV-1 strains with and without ICP0, we were able to show that ICP0 regulates host and viral proteins during the initial onset of neuronal infection. We also show that based on neuronal conditions set forth before HSV-1 initial infection, host proteins will influence HSV-1 viral proteins to repress viral gene expression, thereby promoting the establishment of latency. / Doctor of Philosophy / Herpes simplex virus (HSV-1) is a virus, often acquired during childhood, that more than 50% of people have. Those who are infected with HSV-1 often have cold sores that appear in response to stress on the face or on the genitals. As a virus, HSV-1 replicates around the eyes, nose, and mouth but can also infect neurons where it can continue to replicate or establish latency. Latency is when the virus is inside the neurons but is unnoticeable and can reappear in response to stress. The state of latency is unique to herpesviruses and key to the success of HSV-1, but scientists are unsure of how it works. A protein made by the virus, Infected Cell Protein 0 (ICP0), is often correlated with the state of latency but is often present when the virus is not latent. ICP0 does a lot to support HSV-1, but it primarily destroys proteins that prevent the virus from replicating. By destroying proteins that prevent HSV-1 replication, ICP0 can help the virus make more viruses. The proteins that are destroyed by ICP0 are currently unknown, which represents a significant gap in knowledge. Through the research conducted in this dissertation, we identified some of the proteins that ICP0 destroys in neurons. We utilized neurons from the dorsal root ganglia and HSV-1 viral strain KOS, which encoded a functional ICP0, and n212, which encodes a nonfunctional ICP0, to study the mechanisms used by the virus to infect neurons. By using HSV-1 viruses with and without ICP0, we were able to show what proteins ICP0 destroys during infection in neurons. We were also able to show that HSV-1's ability to establish latency is dependent on how the neurons handle the initial onset of infection. Overall, a combination of host and viral proteins coordinates the virus's ability to establish latency and persist within a host.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/113668 |
| Date | 03 February 2023 |
| Creators | Harrell, Telvin |
| Contributors | Biomedical and Veterinary Sciences, Bertke, Andrea S., Cecere, Thomas Edward, Lazar, Maria Iuliana, Duggal, Nisha |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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