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-associated transcripts (LATs) in trigeminal ganglia for different HSV-1 wild-type strains and to correlate this measurement with the ability of each virus to reactivate. Methods: Latent infections were established in New Zealand white rabbits following bilateral ocular inoculation with one of three different HSV-1 strains: W, F, and KOS. The in vivo ability of each virus to reactivate was determined by (1) detection of induced ocular shedding of HSV-I following 6-hydroxydopamine/epinephrine iontophoresis and intrastromal injection of sterile water, and (2) explantation and, cocultiva tion of trigeminal ganglia (TGs). The proportion of neurons expressing the HSV-1 LAT transcripts was determined by in situ hybridization. Results: Significant differences among the three 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 correlation between the proportion of LAT-expressing neurons and the ability of an HSV-1 strain to reactivate following induction (73%, 36%, 0%) was indicated. Recovery following cocultivation was 82%, 18%, and 13% for W, F, and KOS, respectively. Conclusion: The proportion of TG neurons expressing the HSV-1 LATs is an important measure of the viral genetic factors involved in reactivation. For analysis of factors affecting post-latency events, similar proportions of LAT-positive neurons should be established for viruses under comparison.