Enhancement of gene delivery to human airway epithelial cells in vitro using a peptide from the polyoma virus protein VP1.

Background: Current liposome-based gene delivery methods for therapeutic benefit are limited by their low efficiency. One possible way to improve gene expression is to include a peptide with a nuclear localization signal (NLS) to enhance the movement of the transfection complex from the cytoplasm to the nuclei of target cells. We have tested a synthetic peptide based on the amino terminal region of the polyoma virus VP1 protein. This region has non-overlapping motifs for DNA binding and nuclear localization.

Methods: Luciferase gene transfer efficiency was evaluated using this peptide and a control peptide with a mutated NLS in subconfluent, confluent and polarized human bronchial epithelial (16HBE) cells compared to lipoplex alone.

Results: Gene transfer efficiency with a lipopolyplex containing the VP1 peptide enhanced gene delivery compared to lipoplex. Transfection with a lipopolyplex containing the control peptide failed to enhance gene delivery. The VP1 peptide increased the amount of plasmid associated with the nucleus while the mutant VP1 peptide did not. The order of lipopolyplex formation was important, with greatest enhancement when peptide was added to the plasmid before addition of the liposome. A bipartite peptide with the VP1 sequence and an integrin-binding motif (RGD) resulted in a reduction in gene transfer efficiency compared to lipoplex. Cell adhesion studies showed that the integrin binding associated with the RGD motif was lost when it was attached to the VP1 sequence. The combination of the two peptide sequences in cis may have compromised the function of both.

Conclusions: Our results indicate that the VP1 peptide represents a strategy to enhance liposome-mediated gene delivery to airway epithelia in vitro. Comparison of transfection efficiencies between the VP1 and the mutant VP1 peptides and the direct measurement of plasmid associated with the nucleus suggests that this enhancement is caused by the NLS signal sequence in the peptide.