Currently there are almost 1000 clinical trials for the treatment of cancer, inherited monogenic diseases, and cardiovascular diseases.¹ Viral vectors have been used extensively to transduce human cells or tissues, mostly retroviruses and adenoviruses representing the majority because of their transduction efficiency compared to other gene transfer techniques (liposomes, gene gun, electroporation). However, further progress in gene medicine has been compromised by severe problems that arose in clinical trials using recombinant adenoviruses or retroviruses. Severe side effects resulted either from “overdosing” of adenoviral particles resulting in fulminant inflammation or from retroviral insertion into the genomic DNA leading to deregulated proliferation of transduced cells.

The question arises whether there could be a therapeutic option for gene therapy in the treatment of non-life threatening diseases? If there is a consensus that this could be useful, there are some important prerequisites: the gene therapeutic vehicle has to be safe, it should be specifically expressed only in the target cells/tissues without …