1. ¹Gene Therapy Research Group, Section of Cell and Molecular Biology, Sir Alexander Fleming Building, Imperial College Road, Imperial College of Science, Technology and Medicine, London, UK
2. ²Department of Internal Medicine I, Medical University Hospital, Tuebingen, Germany
3. ³Molekulare Virologie, Max-Planck-Institute for Biochemistry, Martinsried, Germany

Correspondence: Dr SN Waddington, Gene Therapy Research Group, Section of Cell and Molecular Biology, Sir Alexander Fleming Building, Imperial College Road, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK

Received 20 April 2003; Accepted 27 October 2003; Published online 15 January 2004.

Abstract

Current concerns over insertional mutagenesis by retroviral vectors mitigate investigations into alternative, potentially persistent gene therapy vector systems not dependent on genomic integration, such as Sendai virus vectors (SeVV). Prenatal gene therapy requires efficient gene delivery to several tissues, which may not be achievable by somatic gene transfer to the adult. Initially, to test the potential and tropism of the SeVV for gene delivery to fetal tissues, first-generation (replication- and propagation-competent) recombinant SeVV, expressing -galactosidase was introduced into late gestation immunocompetent mice via the amniotic and peritoneal cavities and the yolk sac vessels. At 2 days, this resulted in very high levels of expression particularly in the airway epithelium, mesothelium and vascular endothelium, respectively. However, as expected, substantial vector toxicity was observed. The efficiency of gene transfer and the level of gene expression were then examined using a second-generation SeVV. The second generation was developed to be still capable of cytoplasmic RNA replication and therefore high-level gene expression, but incapable of vector spread due to lack of the gene for viral F-protein. Vector was introduced into the fetal amniotic and peritoneal cavities, intravascularly, intramuscularly and intraspinally; at 2 days, expression was observed in the airway epithelia, peritoneal mesothelia, unidentified cells in the gut wall, locally at the site of muscle injection and in the dorsal root ganglia, respectively. Mortality was dramatically diminished compared with the first-generation vector.