SIV Vectors

The recovery of vectors that are suitable for an in vivo gene delivery has been a recurrent theme in gene therapy research over the last decade. Several challenging hurdles need to be overcome to reach such a goal. First, is a need for methods that allow the preparation of vectors at high titers and in culture systems with potential for large scale-up need to be optimized. Second, the gene transfer vectors should not be recognized by the host immune system in order to avoid inactivation. Upon delivery into gene therapy recipients, vectors should also be able to circumvent the numerous biological barriers that are likely to limit their diffusion and biodistribution in the target organism. They should, therefore, be able to recognize specifically and to penetrate cells of the gene therapy target tissue. Third, they should be able to replicate and to express a transgene in cells that are either not or only slowly proliferating, a predominant situation in vivo. Last, but not least, they should be accepted by both ethical and regulatory authorities. In this respect, the development of vectors derived from viruses that are not pathogenic to human may be preferred.