HSV-1 quantitation from rabbit neural tissues after epinephrine-induced reactivation

Epinephrine iontophoresis into the eye can induce ocular herpes simplex virus type-1 (HSV-1) shedding with a high frequency from latently infected rabbits. The present study was designed to qualify and quantify infectious HSV-1 from neural tissues of latently infected rabbits after ocular epinephrine iontophoresis. Epinephrine iontophoresis was performed daily for 3 consecutive days on selected days during 220-227 days postinoculation. The induced ocular shedding was detected in the tear film with a frequency of 83% (10/12) within 72 hr after the initial iontophoresis. The rabbits were killed 24 hr after the last iontophoretic treatment, and the corneas and neural tissues were homogenized immediately. The cell-free supernatants were inoculated on primary rabbit kidney cell monolayers for qualitative assays of infectious virus and later titrated on CV-1 monolayers. The frequencies of the recovery of infectious HSV-1 from the cell-free homogenates were 0% of the corneas (0/12), 83% (10/12) from the superior cervical ganglion (SCG), 100% (12/12) from the trigeminal ganglion (TG), 42% (5/12) from the ophthalmic branch of the trigeminal nerve (TN), 8% (1/12) from the root entry zone of the trigeminal nerve into the brain-stem (REZ), and 0% (0/12) from the cerebellum. The authors conclude that epinephrine iontophoresis can reactivate the latent HSV-1 in neural tissues and infectious virus can be quantified from the cell-free homogenates. To the best of our knowledge, this is the first report to quantify HSV-1 with a high frequency from neural tissues following induced reactivation.