THE PROPORTION OF TRIGEMINAL GANGLIONIC NEURONS EXPRESSING HERPES-SIMPLEX VIRUS TYPE-1 LATENCY-ASSOCIATED TRANSCRIPTS CORRELATES TO REACTIVATION IN THE NEW-ZEALAND RABBIT OCULAR MODEL

Background: The purpose of this study was to determine the proportion of neurons expressing herpes simplex virus type1 (HSV-1) latency-assoc iated transcripts (LATs) in trigeminal ganglia for different HSV-1 wil d-type strains and to correlate this measurement with the ability of e ach virus to reactivate. Methods: Latent infections were established i n New Zealand white rabbits following bilateral ocular inoculation wit h one of three different HSV-1 strains: W, F, and KOS. The in vivo abi lity of each virus to reactivate was determined by (1) detection of in duced ocular shedding of HSV-I following 6-hydroxydopamine/epinephrine iontophoresis and intrastromal injection of sterile water, and (2) ex plantation and, cocultiva tion of trigeminal ganglia (TGs). The propor tion of neurons expressing the HSV-1 LAT transcripts was determined by in situ hybridization. Results: Significant differences among the thr ee HSV-1 wt strains W, F, and KOS in the proportions of LAT-expressing neurons (4.70%, 0.70%, 0.15%, respectively) were found. A positive co rrelation between the proportion of LAT-expressing neurons and the abi lity of an HSV-1 strain to reactivate following induction (73%, 36%, 0 %) was indicated. Recovery following cocultivation was 82%, 18%, and 1 3% for W, F, and KOS, respectively. Conclusion: The proportion of TG n eurons expressing the HSV-1 LATs is an important measure of the viral genetic factors involved in reactivation. For analysis of factors affe cting post-latency events, similar proportions of LAT-positive neurons should be established for viruses under comparison.