TARGETED TRANSDUCTION OF CNS NEURONS WITH ADENOVIRAL VECTORS CARRYINGNEUROTROPHIC FACTOR GENES CONFERS NEUROPROTECTION THAT EXCEEDS THE TRANSDUCED POPULATION

Application of neurotrophic factors (NFs) to the cut stump of motor ne rves of neonatal rats confers neuroprotection from trauma-induced neur onal death. To lest whether motoneurons are capable of responding to e ndogenously produced NFs, facial motoneurons were genetically modified in vivo to express several NFs and then tested for their response to peripheral nerve damage. Replication-defective adenoviral vectors [Adv .Rous sarcoma virus (RSV)-nf] representing three families of NFs were constructed that carried genes for brain-derived neurotrophic factor ( BDNF), ciliary neurotrophic factor (CNTF), glial cell-derived neurotro phic factor (GDNF), and nerve growth factor Media from cultured cells transduced with Adv.RSV-nf contained NFs that supported the survival o f cultured chick sensory neurons in the same manner as recombinant NF standards. When Adv.RSV-nf or an adenoviral vector containing the beta -galactosidase gene (Adv.RSV-beta-gal) were injected into the facial m uscles of neonatal rats the vectors were retrogradely transported to t he facial nucleus where the NFs or beta-gal were expressed. A fraction (similar to 10%) of the neurons were transduced as demonstrated by re verse transcriptase-PCR, histochemistry, and immunocytochemistry. In t he case of Adv.RSV-BDNF, Adv.RSV-CNTF, and Adv.RSV-GDNF, a significant portion of the facial nucleus neurons was protected, 16.5, 18.2, and 53.3%, respectively, from death after axotomy, showing that neurons ar e capable of transporting the Adv.RSV-nf, expressing the recombinant N F genes, and responding to the NFs. In the case of Adv.RSV-GDNF, a gre ater number of facial nucleus motoneurons survived than were transduce d, indicating that neighboring untransduced neurons were protected by the GDNF expressed by the transduced neurons by a paracrine mechanism.