ABSTRACT
Virosomes are reconstituted viral envelopes that can serve as vaccines and as vehicles for cellular delivery of macromolecules.
The prospect of drug delivery and targeting using virosomes is an interesting field of research and development. Because virosomes
are biocompatible, biodegradable, nontoxic, and non-autoimmunogenic, attempts have been made to use them as vaccines or adjuvants
as well as delivery systems for drugs, nucleic acids, or genes for therapeutic purposes. Influenza virus is the most common
virus of choice. The success of virosomal drug delivery depends on the methods used to prepare the encapsulated bioactive
materials and incorporate them into the virosomes, as are characterization and formulation of the finished preparation. Virosome
technology could potentially be used to deliver peptides, nucleic acids or genes, and drugs like antibiotics, anticancer agents,
and steroids.
(VETTER PHARMA INTERNATIONAL GMBH)
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Promising drugs are often discontinued during development because they cannot be suitably delivered to target cells, tissues,
and organs. The new generation of therapeutics against cancer or neurodegenerative disorders require delivery systems that
target drugs to specified cell types and host tissues by receptor-mediated uptake and controlled release. Virosomal technology
presents a novel sophisticated delivery system to meet these challenges.
Virosomes are reconstituted viral envelopes, including membrane lipids and viral spike glycoproteins, but devoid of viral
genetic material. The external surface of the virosome resembles that of a virus particle, with spike proteins protruding
from the membrane, but their interior compartment is empty. Virosomes were first prepared by Almeida et al., who inserted
purified influenza spike proteins into preformed liposomes.1 Thereafter a range of viral envelopes have been reconstituted, including those of Sendai virus,2–4 Semliki Forest virus (SFV),5,6 vesicular stomatitis virus (VSV),7,8 and Sindbis virus.9 Because virosomes display viral envelope glycoproteins, which, in their native conformation stimulate humoral responses,
they are highly effective as vaccine antigens and adjuvants.10–12 Moreover, since the receptor-binding and membrane-fusion properties of the viral envelope glycoprotein can be preserved,
virosomes can be used as transport vehicles for cellular delivery of biologically active macromolecules. In this article,
we provide a brief overview of virosomal drug delivery.
Overall, virosomes protect pharmaceutically active substances from proteolytic degradation and low pH within endosomes, allowing
their contents to remain intact when they reach the cytoplasm. This is a major advantage of virosomal carrier systems over
other drug-delivery vehicles, including liposomal and proteoliposomal carrier systems.
