New Approaches towards ex vivo and in vivo gene therapy

A number of hurdles have to be overcome for efficient and specific gene the rapy approaches. Here, we report on two different strategies that should le ad to an improvement of current protocols. A strategy is presented to tag u nique chromosomal integration sites by means of retroviral infection, which can be reused for exchange with the gene of interest by action of site-spe cific recombinases. Targeting exchange is achieved in one step with 100% ef ficiency by a stringent positive selection, which makes further screening s uperfluous. With this strategy a predictable gene expression is obtained fo r foreign genes integrated into a predefined chromatin structure. A second approach aims at the stabilization of mouse retroviruses towards human seru m which is a prerequisite for in vivo gene thera py protocols. To stabilize murine leukemia virus-based retroviruses against human serum, complement r egulatory proteins were fused to the retroviral ENV proteins. This resulted in infectious and human complement-protected particles. Copyright (C) 2000 S. Karger AG,Basel.