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.

Abstract

• Background: The purpose of this study was to determine the proportion of neurons expressing herpes simplex virus typel (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-1 following 6-hydroxydopamine/ epinephrine iontophoresis and intrastromal injection of sterile water, and (2) explantation and cocultivation 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-latenc-events, similar proportions of LAT-positive neurons should be established for viruses under comparison.