These beneficial effects have been replicated in non-human primate models of PD with AAV-GDNF shown to protect nigral neurons, provide a partial protection of DA fibers in the striatum, and bring about a clinical improvement in monkeys lesioned with 6-OHDA and MPTP (Eslamboli et al., 2003; Eberling et al., 2009; Johnston et al., 2009). The gene discussed is GDNF; the disease is Parkinson disease.