The present invention relates to an immunogen-carrier having immunopotentiating or adjuvant properties. More particularly, the immunogen-carrier is a virus-like particle (VLP) from the family of potexvirus, and most particularly the papaya mosaic virus. The VLP produced by recombinant techniques is in fusion with one of its own proteins a protein immunogen. The above VLP and a protein or a protein extract from a viral, bacterial or parasital pathogen may be used as a vaccine.