A means for targeting therapeutics to peripheral nervous system neurons with axonal damage.

Objective: Delivery of biological therapeutics to motor and dorsal root ganglion neurons remains a major hurdle in the development of treatments for a variety of neurological processes, including peripheral nerve injury, pain, and motor neuron diseases. Because nerve cell bodies are important in initiating and controlling axonal regeneration, targeted delivery is an appealing strategy to deliver therapeutic proteins after peripheral nerve injury.

Methods: Tet1 is a 12-aa peptide, isolated through phage display that is selected for tetanus toxin C fragment-like binding properties. In this study, we surveyed its uptake and retrograde transport using compartmented cultures and sciatic nerve injections. We then characterized the time course of this delivery. Finally, to confirm the retrograde transport involvement, a colchicine pretreatment was performed. We also performed competitive binding studies between Tet1 and a recombinant tetanus toxin C fragment using recombinant tetanus toxin C fragment enzyme-linked immunosorbent assay.

Results: We were able to demonstrate efficient uptake and retrograde axonal transport of the Tet1 peptide in vitro and in vivo. Intraneural colchicine pretreatment partially blocked fluorescence detection in the spinal cord, revealing a retrograde axonal transport mechanism. Finally, a competitive enzyme-linked immunosorbent assay experiment revealed Tet1-specific binding to the recombinant tetanus toxin C fragment axon terminal trisialogangliosides receptor.

Conclusion: These properties of Tet1 can be applied to the development of therapeutic viral vectors and fusion proteins for neuronal targeting and enhanced spinal cord delivery in the treatment of nerve regeneration, neuroprotection, analgesia, and spasticity. Small peptides can be easily fused to larger proteins without significantly modifying their function and can be used to alter the binding and uptake properties of these proteins.