Validation of human sensory neurons derived from inducible pluripotent stem cells as a model for latent infection and reactivation by herpes simplex virus 1.

Herpes simplex virus 1 (HSV-1) undergoes primary acute lytic replication in mucosal epithelial cells and then spreads to establish latent infection in peripheral neurons including sensory and autonomic neurons. Latent HSV-1 reactivates to cause recurrent cold sores but can also cause more severe disease including keratitis and encephalitis. Animal models have been used extensively to study HSV-1 latent infection, while human sensory neuronal systems have been difficult to establish or make scalable. To address neuron-intrinsic mechanisms of HSV-1 latent infection, we developed a protocol to rapidly differentiate human-inducible pluripotent stem cells (hiPSCs) into sensory neurons. The differentiated neurons are excitable and express functional ion channels. We established conditions for latent infection with HSV-1 in these cells that show i) no infectious virus, ii) reduced lytic gene expression, iii) efficient latency-associated transcript expression, and iv) viral heterochromatin. Latent HSV-1 can be reactivated by previously known stimuli including forskolin and PI3Ki. Therefore, this scalable human iPSC-derived sensory neuron system is a promising model to explore mechanisms of HSV-1 latent infection in human neurons. IMPORTANCE: Herpes simplex viruses are prevalent human pathogens that cause significant morbidity and mortality in neonates and adults. They undergo acute infection in the mucosae and spread to peripheral neurons including sensory and autonomic neurons, where they establish lifelong latent infection. Reactivation from latency leads to recurrent infection and disease, including central nervous system infection that can be life-threatening. Experimental studies of HSV latency have mostly been conducted in animals, which may differ from the human situation. In this study, we establish a system for differentiation of human-inducible pluripotent stem cells into sensory neurons and for latent infection and reactivation by herpes simplex virus 1. This system will enable studies of the mechanism of HSV latent infection in human sensory neurons and therapeutic approaches to curtail it.