Gene Therapy 2000.
This article reviews 1) the use of gene transfer methods to genetically manipulate hematopoietic stem cell targets, 2) recent advances in technology that are addressing problems that have prevented widespread successful translation of gene transfer approaches for the cure of disease, and 3) recent regulatory issues related to human gene therapy trials. In Section I, Dr. Nienhuis describes the use of alternative viral envelopes and vector systems to improve efficiency of transduction of hematopoietic stem cells. Major limitations of stem cell transduction are related to low levels of viral receptors on the stem cells of large animal species and the low frequency of cycling stem cells in the bone marrow. Attempts to circumvent these limitations by exploiting non-oncoretroviral vectors and pseudotyping of Moloney vectors with alternative envelopes are discussed. In Section II, Dr. Hawley addresses new strategies to improve the expression of transgenes in cells derived from long-term reconstituting hematopoietic stem cells. Transgene silencing in transduced hematopoietic stem cells remains an obstacle to gene therapy for some gene sequences. New generations of retroviral backbones designed to both improve expression and reduce silencing in primary cells are explored. In Section III, Drs. Smith and Cornetta update regulatory issues related to human gene therapy trials. Increased scrutiny of human trials has led to changes in requirements and shifts in emphasis of existing regulations, which apply to human gene therapy trials. The current Food and Drug Administration's structure and regulations and the roles of the Recombinant DNA Advisory Committee of the NIH and other sponsors and partners in gene therapy trials are reviewed.