Abstract
Purpose: :
The goal of this research is to use 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 induce mutations or affect transcription of a gene. Three TFOs 19–24 bp in length were tested for their proposed binding activity against target sequences within the HSV–1 inverted repeat region. Conventional phosphodiester–backboned (pd) and diethylethylenediamine (DEED) and dimethylethylenediamine (DMED) modified purine motif TFOs were synthesized and purified.
Results: :
Triplex DNA complexes have been reliably and repeatedly confirmed in vitro using each of the three TFOs and their respective HSV–1 target sequences. Under optimal conditions (MgCl2 20 mM, no KCl) using pd–backboned oligos complete triplex formation was achieved at 0.5–5 nM TFO. However, the pd–backboned oligos bound less efficiently or not at all under intracellular conditions (MgCl2 0.1 mM, KCl 140 mM). Three cationic DEED or DMED modified oligonucleotides formed complete triplexes at HSV–1 target sites at a concentration of 0.5 nM. Specificity these reactions was confirmed by the lack of detectable binding between control, unmatched and HSV–1 targets. Cellular transport and reporter construct studies with the modified TFOs are underway.
Conclusions: :
These studies indicate the feasibility of antilatency antivirals active against HSV–1 at nanomolar concentrations. The oligonucleotides required chemical modifications to form triplex DNA under conditions similar to those found inside living cells.
Keywords: herpes simplex virus • keratitis • gene modifiers