Gene therapy
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Endogenous opiate peptides acting pre- and post-synaptically in the dorsal horn of spinal cord inhibit transmission of nociceptive stimuli. We transfected neurons of the dorsal root ganglion in vivo by footpad inoculation with 30 microl (3 x 10(7) p.f.u.) of a replication-incompetent (ICP4-deleted) herpes simplex virus (HSV) vector with a cassette containing a portion of the human proenkephalin gene coding for 5 met- and 1 leu-enkephalin molecules under the control of the human cytomegalovirus immediate-early promoter (HCMV IEp) inserted in the HSV thymidine kinase (tk) locus. ⋯ The antinociceptive effect was blocked completely by intrathecal naltrexone. These results suggest that gene therapy with an enkephalin-producing herpes-based vector may prove useful in the treatment of pain.