Delivery of GDNF by an E1,E3/E4 deleted adenoviral vector and driven by a GFAP promoter prevents dopaminergic neuron degeneration in a rat model of Parkinson's disease

Abstract

A new adenoviral vector (Ad-GFAP-GDNF) (Ad-¼ adenovirus, GFAP ¼ glial fibrillary acidic protein, GDNF ¼ glial cell line-derived neurotrophic factor) was constructed in which (i) the E1,E3/E4 regions of Ad5 were deleted and (ii) the GDNF transgene is driven by the GFAP promoter. We verified, in vitro, that the recombinant GDNF was expressed in primary cultures of astrocytes. In vivo, the Ad-GFAP-GDNF was injected into the striatum of rats 1 week before provoking striatal 6-OHDA lesion. After 1 month, the striatal GDNF levels were 37 pg/mg total protein. This quantity was at least 120-fold higher than in nontransduced striatum or after injection of the empty adenoviral vector. At 3 months after viral injection, GDNF expression decreased, whereas the viral DNA remained unchanged. Furthermore, around 70% of the dopaminergic (DA) neurons were protected from degeneration up to 3 months as compared to about 45% in the control groups. In addition, the amphetamine-induced rotational behavior was decreased. The results obtained in this study on DA neuron protection and rotational behavior are similar to those previously reported using vectors with viral promoters. In addition to these results, we established that a high level of GDNF was present in the striatum and that the period of GDNF expression was prolonged after injection of our adenoviral vector.

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

“…Gene vectors have been injected directly into the brain to circumvent the BBB (Do Thi et al, 2004; Yang et al, 2013). The innate difficulty and risk during brain administration makes this method less applicable over long-term clinical trials.…”

“…In addition, unique pathogenesis of each NDD requires a tailored vehicle system designed to deliver a gene of interest to a certain cell type for a given disease. Though genes have been injected or infused directly in the brain (Do Thi et al, 2004; Yang et al, 2013; Mastorakos et al, 2015), obtaining global gene expression has been difficult -(Lisovoski et al, 1997; Arregui et al., 2011). This is attributed to low gene or vehicle diffusion within brain parenchyma (Mastorakos et al, 2015), less viral vector transduction efficiency (Lisovoski et al, 1997), and reduced gene expression driven by weak promoters (Sandhu et al, 2009).…”

“…Since then, replication-restricted or deficient AVs have been developed by deleting non-essential viral DNA (Andrews et al, 2001; Do Thi et al, 2004; Dormond et al, 2009). Consistent AV-mediated brain gene expression has been found at three through thirty days, and was detectable at six months in Sprague-Dawley (SD) rats (Thomas et al, 2000).…”

“…Adenoviral vector-mediated GDNF gene delivery was tested in 6-hydoxydopamine- (6-OHDA) and cold-lesioned rats, modeling PD and brain trauma, respectively (Hermann et al, 2001a; Do Thi et al., 2004). Lesions and apoptotic cells reduced in the brain trauma model (Hermann et al, 2001a), and dopaminergic neuronal loss decreased and motor function improved in the PD study (Do Thi et al, 2004). When AV delivered BDNF to excitotoxic rats (Bemelmans et al, 1999), Quinolinic acid-induced lesion size was reduced and striatal neuron survival increased (Bemelmans et al, 1999).…”

“…Subsequent peripheral AV immunizations led to reduced CNS gene expression, increased macrophage and T cell infiltration into the brain, microglial activation, and demyelination (Byrnes et al, 1996; Hermens and Verhaagen, 1998; Thomas et al, 2000). Second and third generation AV with deleted early regions (E1, E3, and E4) depicted low immunogenicity (Do Thi et al, 2004). When Bellini and coworkers delivered IGF-1 to rat spinal cords, the resulting mild inflammatory response was attributed to IGF-1 reducing AV immunogenicity (Bellini et al., 2011).…”