Modular retro-vectors for transgenic and therapeutic use.

Retroviruses have been used for many years as vectors for human gene therapy as well as for making transgenic animals. However, the efficient insertion of genes by retroviruses is often complicated by transcriptional inactivation of the retroviral long terminal repeats (LTRs) and by the production of replication-competent retroviruses (RCR). Solutions to these and other difficulties are being found in modular vectors, in which the desirable features of different vector systems are combined. Examples of synergistic vectors include virosomes (liposome/virus delivery), adeno-retro vectors, and MLV/VL30 chimeras. As gene delivery systems become increasingly complex, methodology is also needed for precise assembly of modular vectors. Gene self-assembly (GENSA) technology permits seamless vector construction and simultaneous, multifragment assembly.