Modular retro-vectors for transgenic and therapeutic use

Retroviruses have been used for many years as vectors for human gene therap y as well as for making transgenic animals. However, the efficient insertio n of genes by retroviruses is often complicated by transcriptional inactiva tion of the retroviral long terminal repeats (LTRs) and by the production o f replication-competent retroviruses (RCR). Solutions to these and other di fficulties are being found in modular vectors, in which the desirable featu res of different vector systems are combined. Examples of synergistic vecto rs include virosomes (liposome/virus delivery), adeno-retro vectors, and ML V/VL30 chimeras. As gene delivery systems become increasingly complex, meth odology is also needed for precise assembly of modular vectors. Gene self-a ssembly (GENSA) technology permits seamless vector construction and simulta neous, multifragment assembly, (C) 2000 Wiley-Liss, Inc.