Liposomal leakage induced by virus-derived peptides, viral proteins, and entire virions: rapid analysis by chip electrophoresis.

Permeabilization of model lipid membranes by virus-derived peptides, viral proteins, and entire virions of human rhinovirus was assessed by quantifying the release of a fluorescent dye from liposomes via a novel chip electrophoretic assay. Liposomal leakage readily occurred upon incubation with the pH-sensitive synthetic fusogenic peptide GALA and, less efficiently, with a 24mer peptide (P1-N) derived from the N-terminus of the capsid protein VP1 of human rhinovirus 2 (HRV2) at acidic pH. Negative stain transmission electron microscopy showed that liposomes incubated with the rhinovirus-derived peptide remained largely intact. At similar concentrations, the GALA peptide caused gross morphological changes of the liposomes. On a molar basis, the leakage-inducing efficiency of the P1 peptide was by about 2 orders of magnitude inferior to that of recombinant VP1 (from HRV89) and entire HRV2. This underscores the role in membrane destabilization of VP1 domains remote from the N-terminus and the arrangement of the peptide in the context of the icosahedral virion. Our method is rapid, requires tiny amounts of sample, and allows for the parallel determination of released and retained liposomal cargo.