Retrograde axonal transport of the neurotropic alphaherpesvirus Varicella zoster virus (VZV) from vesicles at the skin results in sensory neuron infection and establishment of latency. Reactivation from latency leads to painful herpes zoster. The lack of a suitable animal model of these processes for the highly human-restricted VZV has resulted in a dearth of knowledge regarding the axonal transport of VZV. We recently demonstrated VZV infection of distal axons, leading to subsequent capsid transport to the neuronal somata, and replication and release of infectious virus using a new model based on neurons derived from human embryonic stem cells (hESC). In the present study, we perform a kinetic analysis of the retrograde transport of green fluorescent protein-tagged ORF23 in VZV capsids using hESC-derived neurons compartmentalized microfluidic chambers and time-lapse video microscopy. The motion of the VZV was discontinuous, showing net retrograde movement with numerous short pauses and reversals in direction. Velocities measured were higher 1 h after infection than 6 h after infection, while run lengths were similar at both time points. The hESC-derived neuron model was also used to show that reduced neuronal spread by a VZV loss-of-function mutant for ORF7 is not due to the prevention of axonal infection and transport of the virus to the neuronal somata. hESC-derived neurons are, therefore, a powerful model for studying axonal transport of VZV and molecular characteristics of neuronal infection.
Bibliographical noteFunding Information:
This study was supported by Israel Science Foundation grant ##238/11 (RSG): NIH grants NS064022 and EY08098, and funds from the Research to Prevent Blindness Inc. and The Eye & Ear Foundation of Pittsburgh (PRK). Dr. Lina Gamarnik (Ziegler) performed preliminary experiments leading to the shortening of the protocol for neuron differentiation via PA6 cells. The authors thank Chaya Morgenstern and Michael Lee for the technical and logistic support and Dr. Rachel Levy-Drummer for the help with the statistics. Our gratitude to Dr. Mike Fainzilber for his insights on retrograde transport. Special thanks to Dr. Alexander Perelman for his personal guidance in live imaging experiments.
- Axonal transport
- Human embryonic stem cells
- Varicella zoster virus