439. Neuronal Membrane Specific Binding Peptides Isolated Via Phage Display Biopanning Against Trisialogangliosides

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Background: The tropism of adeno-associated viral vectors can be altered by inserting peptides into the vector's coat. However, large peptides may alter the capacity of VP proteins to package DNA. In order to enhance the neural affinity and specificity of AAV binding, we have attempted to isolate short peptides which when inserted into the cap gene of the AAV genome, would retarget the vector toward neuronal membranes without hindering its transduction efficiency. We have previously reported a phage display biopanning strategy for the isolation of such peptides (Liu et al Mol Ther: 7(5) S351, 2003). We used trisialogangliosides (GT1b), a known receptor of Clostridial tetanus toxin present on neuronal membranes, as our target. Tetanus toxin owes its high neuronal affinity to specific GT1b binding providing an ideal interaction to replicate in AAV. Using a random 12 amino acid peptide phage library, we conducted a novel four round biopanning process against immobilized GT1b. In the final three rounds of biopanning, we eluted with recombinant Tetanus Toxin C Fragment (rTTC) to recover phage that specifically mimic its binding to GT1b. Four candidate peptides were enriched following the biopanning process. We selected the most common peptide (Clone 2A) which was present in 70% of the sequenced phage clones along with a second peptide (Clone 2B) that shared similar homology with Clone 2A (Liu et al Mol Ther: 7(5) S351, 2003).