Analysis by RNA-PCR of latency and reactivation of herpes simplex virus in multiple neuronal tissues

Following intracameral inoculation with herpes simplex virus type 1 (HSV-1), BALB/c mice develop acute necrotizing chorioretinitis and infectious virus is detected in the eyes, trigeminal ganglia, brain, spinal cord and adrenal glands during acute infection. In this study, we analysed the latent phase of this experimental animal system. In mice which survived the acute infection, latent HSV-1 was recovered from the trigeminal ganglia, brain and adrenal glands by co-cultivation with Vero cells. In these tissues, both the unspliced latency-associated transcript (LAT) and the spliced LAT were detected by RNA-PCR. Following in vivo administration of cyclophosphamide and dexamethasone to induce viral reactivation, ICP0 mRNA became detectable in the multiple neural tissues, and the spliced LAT disappeared whereas the unspliced LAT remained detectable by RNA-PCR. Sequence analysis of the RNA-PCR products revealed that the GC-AG splicing signal previously reported for LATs from trigeminal ganglia was also detected in LATs from the brain and adrenal glands, suggesting that the splicing of LATs might be associated with the maintenance of and/or reactivation from latency. The generalized latent infection of HSV-1 described in this study might serve as an experimental model of possible viral reactivation from organs that do not innervate the primary port of entry.