Historically, the discovery of recombinant DNA technology in the 1970s provided the tools to efficiently develop gene therapy. Scientists used these techniques to readily manipulate viral genomes, isolate genes, identify mutations involved in human diseases, characterize and regulate gene expression, and engineer various viral vectors and non-viral vectors. Many vectors, regulatory elements, and means of transfer into animals have been tried. Taken together, the data show that each vector and set of regulatory elements provides specific expression levels and duration of expression. They exhibit an inherent tendency to bind and enter specific types of cells as well as spread into adjacent cells. The effect of the vectors and regulatory elements are able to be reproduced on adjacent genes. The effect also has a predictable survival length in the host. Although the route of administration modulates the immune response to the vector, each vector has a relatively inherent ability, whether low, medium or high, to induce an immune response to the transduced cells and the new gene products.
The development of suitable gene therapy treatments for many genetic diseases and some acquired diseases has encountered many challenges and uncovered new insights into gene interactions and regulation. Further development often involves uncovering basic scientific knowledge of the affected tissues, cells, and genes, as well as redesigning vectors, formulations, and regulatory cassettes for the genes.
While effective long-term treatments for anemias, hemophilia, cystic fibrosis, muscular dystrophy, Gauscher’s disease, lysosomal storage diseases, cardiovascular diseases, diabetes, and diseases of the bones and joints are elusive today, some success is being observed in the treatment of several types of immunodeficiency diseases, cancer, and eye disorders.