Effect of immunosuppression on gene expression in the HSV-1 latently infected mouse trigeminal ganglion.

PURPOSE: To determine alterations in expression of genes in herpes simples virus (HSV)-1 latently infected mouse trigeminal ganglia (TGs), after treatment with cyclophosphamide and dexamethasone.
METHODS: Scarified corneas of female BALB/c mice were inoculated with HSV-1 strain McKrae. Four weeks after inoculation, cyclophosphamide and dexamethasone were intravenously injected to induce HSV-1 reactivation. Uninfected mice were also treated with the immunosuppressants. Four groups of animals were studied: uninfected, not treated; uninfected, drug treated; latently infected, not treated; and latently infected, drug treated. PolyA+ mRNA from the TGs of each group was reverse transcribed, labeled with 32P, incubated on a 1185-gene array membrane, and analyzed by phosphorimaging. As a comparison and to confirm microarray results, semiquantitative RT-PCR was also performed for selected genes.
RESULTS: The immunosuppressive drugs significantly increased expression of two genes (calpactin 1 light chain and guanine nucleotide-binding protein alpha-stimulating polypeptide [GNAS]) in the ganglia of uninfected mice compared with those in untreated uninfected mice. Ten genes were shown to be significantly increased in the latent TGs of mice treated with immunosuppressants compared with latently infected untreated mice. These genes were prostaglandin E2 receptor EP4 subtype (PTGER4), insulin promoter factor 1 (IPF1), glutathione S-transferase mu2, cyclin D2, peripherin, plasma glutathione peroxidase, methyl CpG-binding protein 2, retinal S-antigen, ErbB2 proto-oncogene, and GNAS. Eight genes were shown to be significantly decreased in the HSV-1 latent TGs treated with the drugs, compared with untreated latently infected mice. These genes were peripheral myelin protein 22, decorin, transcription factor AP-1, dystroglycan 1, myelin protein zero, mitogen-activated protein kinase 3, prothymosin beta 4, and brain lipid-binding protein. The results obtained by semiquantitative RT-PCR were similar to those obtained by microarray analysis.
CONCLUSIONS: Those genes with expression altered by immunosuppressive drug treatment may play an important role in ocular HSV-1 recurrence. Changes in expression of genes in the prostaglandin pathway, a transcription factor, and an enzyme in the cell cycle are considered especially important in HSV-1 reactivation by immunosuppression and are reviewed.