The present invention relates to particles, comprising: a protein envelope with a fusion protein, which comprises a virus protein, a cell permeability-mediating peptide and a heterologous cell-specific binding site; and a nucleic acid present in the protein envelope, which comprises the sequence for a virus-specific packaging signal and a structural gene. The invention further relates to methods for the preparation of such particles and means suitable for this purpose, as well as the use of the particles in gene therapy.