Virosomes are reconstituted influenza virus (A/Singapore) envelopes. The membrane of these vesicles consists of a spherical, unilamellar lipid bilayer. Purified influenza envelope glycoproteins (hemagglutinin HA and neuramindase NA) are inserted into the lipid bilayer. Virosomes with a bilayer consisting of neutral phospholipids can be used as an unspecific or a specific drug carrier system, while positively charged vesicles can be used as a transfer system for any genetic materials.

Semi-synthetic complex derived from nucleic-acid free viral particles. They are essentially reconstituted viral coats, where the infectious nucleocapsid is replaced by a compound of choice. Virosomes retain their fusogenic activity and thus deliver the incorporated compound (antigens, drugs, genes) inside the target cell. They can be used for vaccines (VACCINES, VIROSOME), drug delivery, or gene transfer.