A large body of evidence shows that targeted delivery of exogenous GDNF to the specific brain or spinal regions by viral vectors may be exploited as a potential therapeutic strategy in the treatment of Parkinson’s disease and neuropathic pain [17,18,19], suggesting that using lentivirus inducing a local up-regulation of GDNF is likely to be a potential therapy. The gene discussed is GDNF; the disease is Parkinson disease.