Changes in gene expression in latent HSV-1-infected rabbit trigeminal ganglia following epinephrine iontophoresis

Purpose. The aim of the present study was to identify the genes that express in the nervous system when herpes simplex virus type 1 (HSV-1) reactivates from latency by using subtraction cloning following epinephrine iontophoresis. Methods. The corneas of New Zealand White rabbits (2 to 2.5 kg) were topically inoculated with 5 × 10⁵ PFU of plaque-purified HSV-1 strain McKrae. Corneal infection was monitored by slit lamp examination (SLE) on days 3-7 after infection. At 30d post-infection, eyes were assessed for infectious virus by ocular swabs. Disappearance of virus in ocular swabs signified latency for HSV-1. Latently-infected rabbits were subjected to transcorneal iontophoresis. The messenger RNA (mRNA) was isolated from the trigeminal ganglia and used for subtraction cloning and subtraction library synthesis. Results. Our results indicate 18 genes with increased expression and 6 genes with decreased levels. Northern blot analysis revealed that genes for OX-40 ligand, MHC class II HLA-DR-α and β-microglobulin showed predominant increase followed by tyrosine 3′-monooxygenase, proteolipid protein, tyrosine beta, and apolipoprotein D. Genes that underwent reduced expression included cytochrome c oxidase subunit I, ATP synthase isoform, cytochrome b, ATPase 9, and at least one unidentified gene. Conclusions. Our results, particularly the increased detection of OX-40 ligand and MHC class II-α and β-2 microglobulin, support the finding that lymphocytes persist in latently-infected trigeminal ganglia (TGs). These results also suggest a role of the immune system in HSV-1 recurrences. In addition, we have detected genes associated with neuronal disorders, OX-40L, proteolipid protein, and apolipoprotein D.