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Retroviral cell targeting vectors.

The availability of cell targeting vectors is an unalterable requirement for in vivo gene therapy trials. This review will describe the different strategies developed over the past few years in order to target retroviral vectors to preselected human cell types by genetic modification of the envelope (Env) proteins. Current targeting concepts include the substitution of the complete Env protein as well as the incorporation of new receptor binding domains into the Env protein. These approaches are aimed at altering the host range of vectors with a natural tropism for non-human cells to specific human cell types, or achieving tissue-specificity for vectors that would naturally infect a wide spectrum of human cell types. Targeting concepts and efficient targeting vectors with potential for clinical trials will be described, and their advantages and disadvantages will be discussed.