Avidin fusion protein strategies in targeted drug and gene delivery

Chicken avidin is used in a wide variety of applications in the life sciences, due to its extraordinarily strong affinity for biotin. Avidin-biotin strategy has also recently established a role in medical targeting approaches for cancer treatments. An interesting new exploitation for avidin-biotin techniques is the utilization of this strong affinity in gene therapy, to target and enhance gene delivery to the appropriate target cells and tissues. In this communication, we review novel avidin fusion proteins that have been developed for enhanced gene delivery and drug targeting purposes. The principles of this approach are highlighted by the avidin fusion proteins Scavidin (fusion with the macrophage scavenger receptor class A), Lodavin (fusion with the endocytotic LDL receptor) and avidin-displaying baculovirus (Baavi). Scavidin and Lodavin are cell membrane proteins in which avidin is expressed as an extracellular portion, thereby enhancing the targeted drug and gene delivery with biotinylated drug molecules and vectors. Baavi, on the other hand, displays avidin moieties on its surface, and opens up possibilities for flexible modification of its targeting properties and other characteristics by using different biotin-conjugated molecules. Potential applications of avidin fusion proteins and future trends of targeted drug and gene delivery based on these strategies will be discussed.