Vigilant vectors: adeno-associated virus with a biosensor to switch on amplified therapeutic genes in specific tissues in life-threatening diseases.

There are many life-threatening and chronic diseases in which physiological signals could be used to switch on therapeutic protective genes. We are developing a gene therapy approach in which a systemically injected "vigilant vector" waits for these signals and switches on genes to protect specific tissues with high amplification. The concept of a vigilant vector requires four components. The first component is a safe and stable vector that can be administered by systemic injection and express transgenes in a particular organ or tissue. The adeno-associated virus vector is safe and stable for this purpose. The second component is a reversible gene switch which is a biosensor that can detect certain physiological signals. We are developing a hypoxia switch, based on the oxygen-dependent degradation domain of hypoxia-inducible factor. The third component is a tissue-specific promoter, and we have used the myosin light-chain-2V promoter for specific expression in the heart. The fourth component is an amplification system. For this we have developed a double-plasmid/vector system based on the yeast GAL4 and human transcriptional activator p65 to produce a transactivating fusion protein that binds to a GAL4 activation sequence in an activating plasmid that then expresses high levels of cardioprotective genes. Copyright 2002 Elsevier Science (USA)