Infection of human NT2 cells and differentiated NT-neurons with herpes simplex virus and replication-incompetent herpes simplex virus vectors.

The human embryonal carcinoma cell line NT2 differentiates irreversibly into postmitotic neuron-like cells following treatment with retinoic acid. These differentiated NT-neurons resemble central nervous system (CNS) neurons and are characterized by development of dendrites and axons and the expression of neuron-specific markers. Because of their unique biological characteristics, NT-neurons were investigated for their utility as a system for studying the replication of herpes simplex virus (HSV) in the neuron and for evaluating characteristics of HSV vectors designed for gene delivery to the neuron. Virus replication in differentiated NT-neurons was significantly reduced and delayed relative to replication in undifferentiated NT2 cells. Replication of thymidine-kinase (tk) deficient HSV was further impaired in NT-neurons, reflecting the behavior of tk-negative virus in primary neurons in vitro and ganglia in vivo. Furthermore, replication-incompetent HSV vectors were capable of infecting NT-neurons, expressing a foreign gene, and persisting in a recoverable state for at least 2 weeks following delivery. These results suggest that differentiated NT-neurons can provide a continuous source of human, post-mitotic neurons-like cells for the study of HSV biology and HSV vector development.