Retrovirus molecular conjugates - A novel, high transduction efficiency, potentially safety-improved, gene transfer system

Two significant barriers limit the use of amphotropic retrovirus for human gene transfer protocols: 1) low transduction efficiency in cells with low r eceptor expression and 2) safety concerns originating from the risk of form ation and propagation of replication competent virus in vivo. In principle, if ecotropic retrovirus, which is incapable of infecting human cells, coul d be transiently modified to effectively transduce human cells, this safety risk could be alleviated. Here we demonstrate that formation of amphotropi c retrovirus polylysine molecular conjugates (aMMLV-PL) enhanced gene trans fer up to 10-fold in a variety of human cell lines over the equivalent of u nconjugated vector (aMMLV). The polylysine modification and formation of ec otropic retrovirus molecular conjugates (eMMLV-PL) permitted effective and stable transduction of different human cell lines as well as primary human bone marrow stroma cells at frequencies of greater than 80%. It is conceiva ble that this novel ecotropic-based conjugate retrovirus vector could also potentially provide enhanced safety characteristics not only over amphotrop ic retrovirus vectors but also over genetically tropism-modified recombinan t ecotropic vectors. In contrast to genetic modifications, physical or chem ical modifications are not propagated. Thus, formation of replication compe tent eMMLV from conjugates would be self-limited and would not result in vi rus propagation in humans.