There exists a great need to understand how the human herpesvirus Varicella zoster Virus (VZV) interacts with neurons. The sensory neuron is critical to successful VZV pathogenesis as the site of a decades-long state of persistence, and the source for VZV reactivation to cause Herpes zoster. This painful and debilitating disease is encountered by a third of adults, and is frequently complicated by chronic pain and neurological problems. Furthermore, ophthalmic zoster is a potentially devastating infectious disease that causes significant vision loss and a much greater toll than zoster elsewhere in terms of pain, complications and marked disruption of the quality of life. Even if all eligible persons received the zoster vaccine (which is far from being achieved). the partial effectiveness would still result in some half of a million zoster cases annually. What we know of VZV latency and reactivation has remained enigmatic, controversial and unclear, because most animal models or their neurological tissues do not support VZV replication or reactivation. Indeed, VZV experimental reactivation has proved exceedingly difficult under any circumstances. Yet, if neuronal infection, spread, persistence or reactivation can be prevented, disease could be more easily controlled. We now have an unprecedented cultured human neuron platform, derived from human embryonic stem cells, that supports not only VZV productive infection, but also persistent states that can now be reactivated. Our overlying hypothesis is that this system will enable us to address aspects of neuron infection, latency and qreactivation in a manner that has not been previously possible.
Our first aim will test the hypothesis that specific VZV proteins are required for neuron axonal infection, replication, inter-neuronal spread or anterograde axonal return. We will evaluate fluorescent reporter VZV with gene deletions for each stage of neuronal infection to identify those proteins required. Such proteins could be not only be targeted in strategies to block latency and reactivation, but such VZV mutants could be the basis for improved vaccines with defined deficiencies in neurotropism.
Our second aim will address the viral transcription program during VZV persistence and reactivation. We will then identify what transcription occurs during persistence and reactivation, including a search for small RNAs that may contribute to latency. We will also address if transcriptional programs differ following reactivation at differen temperatures.
Our third aim will test the hypothesis that the persistent VZV genome can be targeted by large sequence recognition nucleases, in order to reduce VZV latent genomic loads or prevent reactivation. This would establish principles or targeting the latent VZV genome without reliance on viral gene products. Globally, our studies will set the stage for understanding and targeting the VZV latent state in a manner that has not been previously possible.

Public Health Relevance

Most people worldwide are infected by varicella zoster virus (VZV) when they have chickenpox. Virus then remains in their nerves for life: in about a third of people, it reemerges late in life to cause 'shingles', a painful and debilitating disease that can have major life-changing long-term consequences, including loss of vision. The state of the virus in neurons and what leads to reawakening have been extraordinarily difficult to study. We now have a cultured human neuron system that recapitulates latency and reactivation, and the work proposed will use it to study VZV latency reemergence and the means to prevent them.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IDM-W (02))
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Challberg, Mark D
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University of Pittsburgh
Schools of Medicine
United States
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Markus, Amos; Golani, Linoy; Ojha, Nishant Kumar et al. (2017) Varicella-Zoster Virus Expresses Multiple Small Noncoding RNAs. J Virol 91:
Markus, Amos; Lebenthal-Loinger, Ilana; Yang, In Hong et al. (2015) An in vitro model of latency and reactivation of varicella zoster virus in human stem cell-derived neurons. PLoS Pathog 11:e1004885