Overview: Retroviral Vectors for Gene Therapy and Transgenics

Ribozyme uses in retinal gene therapy

In this chapter we discuss the design, delivery and preclinical testing of mutation-specific ribozymes for the treatment of dominantly inherited retinal disease. We focus particular attention on the initial screening of ribozymes in vitro, because the activity of RNA enzymes in cell-free systems can be used to predict their suitability for animal experiments. Current techniques for delivering genes of interest to cells of the retina using viral vectors are then briefly surveyed emphasizing vector properties that best match to the needs of a ribozyme-based therapy. Using these considerations, analysis of ribozyme gene therapy for an autosomal dominant RP-like disease in a rodent model is outlined emphasizing the desirability of combining biochemical, morphological and electrophysiological measures of therapy. Finally, we describe alternative, perhaps more general, ribozyme approaches that have yet to be tested in the context of retinal disease.

Interactions between Exogenous and Endogenous Retroviruses

Retroviruses are distinguished from other viruses by several features. Notably, some retroviruses are present as normal elements in the genomes of virtually all vertebrates (endogenous proviruses). Others are exogenous, i.e. horizontally transmitted agents, many of which cause fatal diseases. The endogenous retroviruses are genetically transmitted and to a large extent their significance is uncertain. However, there is evidence suggesting that they contribute to the development of diseases in several animal species. Most importantly, some endogenous retroviruses are capable of interacting with exogenous counterparts through a variety of different mechanisms with serious consequences to the host. Conversely, others are advantageous in that they protect against exogenous retroviruses. In this review various types of interactions between endogenous and exogenous retroviruses are discussed, including receptor interference, recombination, phenotypic mixing, immunological interactions and heterologous trans-activation. Copyright 1997 S. Karger AG, Basel