Exploration of peptide motifs for potent non‐viral gene delivery highly selective for dividing cells

Abstract

The immunogenicity of viral DNA vectors is an important problem for gene therapy. The use of peptide motifs for gene delivery would largely overcome this problem, and provide a simple, safe and powerful approach for non-viral gene therapy. We explored the functional properties of two motifs: the (Lys)(16) motif (for binding and condensing DNA, and probably also nuclear translocation of plasmids) and the fusogenic peptide motif of influenza virus (for acid-dependent endocytic escape of peptide/DNA particles). The physical properties and gene delivery efficiencies of (Lys)(16)-containing peptides in combination with free fusogenic peptide were evaluated, and compared with a single composite peptide incorporating both moieties. Post-mitotic corneal endothelial cells and growth-arrested HeLa were included, so as not to neglect the question of nuclear translocation of plasmids. The fusogenic moiety in the composite peptide was able to adopt an alpha-helical configuration unhindered by the (Lys)(16) moiety, and retained acid-dependent fusogenic properties. The composite peptide gave remarkably high levels of gene delivery to dividing cell lines. However, in marked contrast to (Lys)(16)/DNA complexes plus free fusogenic peptide, the composite peptide was completely ineffective for gene delivery to post-mitotic and growth-arrested cells. Attachment of the fusogenic peptide to (Lys)(16) appears to block (Lys)(16)-mediated nuclear translocation of plasmid, but not fusogenic peptide mediated endocytic escape. This strengthens the experimental basis for (Lys)(16)-mediated nuclear translocation of plasmids, and provides a single peptide with potent gene delivery properties, restricted to dividing cells. This property is potentially useful in experimental biology and clinical medicine.