Abstract
Purpose::
The goal of this research is to use triplex-forming oligonucleotides to bind and disable latent herpes simplex virus type 1 in order to prevent episodes of recurrent herpes keratitis.
Methods::
Triplex-forming oligonucleotides (TFOs) form a third DNA strand that is bound non-covalently to specific double stranded DNA target sequences to affect transcription of a gene.Specific anti-HSV TFOs were tested for their proposed binding activity against target sequences within the HSV-1 inverted repeat region. Cationic-modified purine motif TFOs were synthesized and purified by HPLC. Both regular and modified TFOs were conjugated to photoactivatable compounds, tested for binding in gel shift assays, and assayed for their potential to cleave DNA at their target sites.
Results::
The anti-HSV-1 oligonucleotide "TFO3" was conjugated to the photoactivatable compounds pheophorbide and tetraphenylporphyrin (TPP). These compounds were purified by HPLC. Chemical structures were verified by mass spectroscopy. Single-stranded nicking was demonstrated at 1 mM free TPP following activation by white, blue, and red laser light. Unmodified 50 nM TFO3-TPP binds to and shifts its HSV-1 target site. Some nicking of the HSV-1 target site was induced under these conditions following prolonged exposure of the triplex to intense blue light. Oligo transport and viral reactivation studies are ongoing in a latently infected cellular system and in explanted, latently infected mouse trigeminal ganglia.
Conclusions::
These studies continue to pursue the goal of developing a safe, specific, and effective genetic treatment to eliminate latent HSV-1 in neural tissue. Significant progress has been made in conjugating and modifying the oligos to damage synthetic viral target DNA.
Keywords: herpes simplex virus • keratitis • gene transfer/gene therapy