Herpes simplex virus type 1 promoter activity during latency establishment, maintenance, and reactivation in primary dorsal root neurons in vitro

A neonatal rat dorsal root ganglion-derived neuronal culture system has bee n utilized to study herpes simplex virus (HSV) latency establishment, maint enance, and reactivation. We present our initial characterization of viral gene expression in neurons following infection,vith replication-defective H SV recombinants carrying beta -galactosidase and/or green fluorescent prote in reporter genes under the control of lytic cycle- or latency-associated p romoters. In this system lytic virus reporter promoter activity was detecte d in up to 58% of neurons 24 h after infection. Lytic cycle reporter promot ers were shut dean over time, and long-term survival of neurons harboring l atent virus genomes was demonstrated. Latency-associated promoter-driven re porter gene expression was detected in neurons from early times postinfecti on and was stably maintained in up to 83% of neurons for at least 3 weeks. In latently infected cultures, silent lytic cycle promoters could be activa ted in up to 53% of neurons by nerve growth factor withdrawal or through in hibition of histone deacetylases by trichostatin A. We conclude that the us e of recombinant viruses containing reporter genes, under the regulation of lytic and latency promoter control in neuronal cultures in which latency c an be established and reactivation can be induced, is a potentially powerfu l system in which to study the molecular events that occur during HSV infec tion of neurons.