A human sensory neuron model for varicella-zoster virus latency and reactivation in vitro

ABSTRACT Varicella-zoster virus (VZV) is a ubiquitous human neurotropic alphaherpesvirus that establishes lifelong latency in sensory ganglionic neurons. Subsequent viral reactivation causes herpes zoster, a morbid disease often complicated by neuropathic pain. Mechanisms underlying VZV latency and reactivation are not understood, mostly due to the lack of permissive animal models and challenges of current in vitro latency modeling. Here, we evaluated HD10.6 cells, a simplified and easily expandable human sensory neuron line to model VZV latency and reactivation. Differentiated HD10.6 (dHD10.6) neurons supported productive VZV infection, viral DNA replication, production of infectious progeny, and viral spread in cultures. VZV infection was associated with limited cytopathic effects and ultrastructural changes. Infecting dHD10.6 neurons with cell-free VZV in the presence of antivirals resulted in a quiescent-persistent state, characterized by persistent VZV genomes with restricted VZV gene expression and absence of infectious virus. Importantly, VZV could be reactivated by treatment with capsaicin, as evidenced by increased lytic viral transcription and virus spread. In conclusion, this study establishes human HD10.6 neurons as a novel and expandable in vitro model for studying VZV latency and reactivation to identify virus and host factors governing latency that may serve as therapeutic targets to restrict VZV reactivation. IMPORTANCE Most individuals carry latent varicella-zoster virus (VZV) in their dorsal root ganglia (DRG), which can reactivate to cause shingles and chronic pain. The mechanisms by which VZV establishes latency and triggers of reactivation are incompletely understood. Current platforms for the study of VZV latency do not easily support functional experiments (ganglia) or are difficult to expand and complicated by mixed neuronal populations (stem cell-derived neurons). Here, we demonstrate that differentiated HD10.6 cells derived from immortalized human DRG-derived neurons provide a clonal and easy-to-expand platform for studying lytic, latent, and reactivated VZV infection in sensory neurons. We propose that the HD10.6 platform could provide the basis to conduct studies on the viral latent state that have hitherto not been possible.