New experimental models are needed to develop treatments for varicella zoster virus (VZV), a DNA virus that has infected over 90% of individuals worldwide. Primary infection causes chickenpox, while reactivation of the virus within the nervous system can have dire consequences. Shingles (herpes zoster) is the most common manifestation of viral reactivation, affecting one out of every three people in the U.S. and causing post-herpetic neuralgia (PHN), a severe, often chronic, pain syndrome with annual U.S. costs of over $1 billion. Viral reactivation within the central nervous system can result in encephalitis and myelitis, often leading to death or severe cognitive and physical disability. Notably, VZV continues to exact a marked toll despite the advent and widespread use of antiviral agents (acyclovir) and vaccination, which only afford partial protection and do not specifically address PHN. Thus, new therapies are needed to limit the morbidity and mortality associated with neuronal infection and reactivation. The major limitation in the study of VZV infection is the strict species-specificity of the virus, such that it essentially exclusively infects human cells. As a result, there are no robust animal models that recapitulate essential features of human disease. Moreover, the virus appears to utilize distinct cellular and molecular pathways in different cell types. Thus, studies of viral infection in human fibroblasts or other skin cells may not directly bear on pathogenesis within human neurons. Recently, VZV has been shown to infect neurons derived from human neural stem cells and human pluripotent stem cells, suggesting that stem-cell based approaches for the study of VZV pathogenesis are likely to hold great promise for the development of new treatments. However, most human neuronal cultures systems derived from stem cells are typically comprised of few, if any, sensory neurons. This is a great limitation since sensory neurons are the main cell type in which the virus establishes latency and later re-emerges during reactivation. Here, we propose to develop a model of human pluripotent stem cell based model of sensory neuron infection by VZV. The establishment of such a model will result in the ability to study VZV neuropathogenesis in a relevant cell type. We anticipate that establishment of our model will yield initial insights into how VZV infects and reactivates in human sensory neurons and will serve as the basis for a system to develop new treatments for VZV reactivation and PHN.
Over 90% of individuals worldwide have been infected by varicella zoster virus (VZV), the cause of chickenpox. VZV remains dormant in the nervous system and, when it reactivates, can cause the painful condition shingles or debilitating neurologic conditions such as brain or spinal cord inflammation (encephalitis and myelitis). Here, we propose to use new stem-cell based models to investigate pathways within neurons that contribute to infection and reactivation.
