Gene Therapy Group
Group Leader: Professor Olivier Danos
Gene therapy is the insertion of nucleic acids into cells of an organism in order to change or correct its phenotype with the ultimate purpose of treating disease. Whereas traditional drugs act by direct and transient modification of a biological target, the purpose of gene therapy is to reprogram cells. Clinical studies have now demonstrated biological responses or efficacy following gene therapy in patients with genetic diseases affecting the immune system, skin, blood clotting or retina. Positive data have also been reported in patients with AIDS, melanoma and Parkinson disease. Although these studies clearly indicate that gene therapy will be a part of molecular medicine practice in the near future, they also reveal difficulties, limitations and toxicities that require attention.
We have a long standing interest and expertise in the design of viral vectors for gene transfer and their application in gene therapy. We focus mostly on vectors derived from retroviruses and lentiviruses which are highly effective in a variety of cultured cells including stem cells (Figure 1), as well as from Parvoviruses (Adeno-Associated Virus, AAV) which can be used for direct gene transfer into target organs including liver, brain, skeletal and cardiac muscle and retina Figure 2 and 3).
Antisense sequence delivery for therapeutic intervention
Up to 50% of disease-associated mutations in humans affect the processing of pre-mRNAs, resulting in exon skipping, inclusion of cryptic exons or intron retention, and to the production of non-functional mRNAs or proteins. In addition, neutral exonic mutations can disrupt splicing enhancers and silencers and have an important impact on the delicate balance of alternative splicing. The modulation of the pre-mRNA maturation processes is likely to be a powerful mode of impacting on a cellular phenotype and can be proposed as a strategy to compensate the deleterious effect of mutations. It can be achieved with a high specificity, using antisense sequences that mask key determinants of splicing through Watson-Crick pairing with the pre-mRNA. We have previously used AAV and lentiviral vectors for the delivery of antisense sequences linked to a modified U7 small nuclear RNA (snRNA) and demonstrated their efficacy in the animal models of Duchenne Muscular Dystrophy and in cells from human patients (Figure 3).
The goal of this project is to obtain optimal and controlled levels of antisense sequences following AAV or lentivirus-mediated gene transfer. This involves the design of efficient, tissue specific and regulatable expression cassettes for improved antisense carriers derived from short nuclear (sn) RNAs.
Design of a universal lentiviral vector for safe chromosomal integration
Homologous recombination will be used to drive integration of a sequence carried by a lentiviral vector towards a precise and unique site on the human genome. The integration site will be chosen following two criteria: a) the demonstration from the available data on integration sites in gene therapy patients that vector integration at this locus is innocuous, and b) the presence of a recognition sequence for an artificial homing endonuclease (meganuclease) engineered from I-CreI, which will be used to transiently enhance the rate of recombination at this locus. Our goal is to minimise the risk of integration mutagenesis.
UCL Gene Therapy Consortium (Olivier Danos, Director)
The multi-disciplinary campus of UCL is an ideal setting for the development of gene therapy with its specialist hospitals, strong clinical track record in experimental medicine, and excellence in basic research. UCL supports an exceptional array of gene therapy research spanning basic vector design, preclinical gene therapy development and clinical trials. The UCL Gene Therapy Consortium is a Wellcome Trust funded initiative by leading scientists and clinicians on the campus who recognize that excellence in gene therapy at UCL now depends on the organisation of a translational research program, facilitating the development of improved therapies to be tested in a series of phase I/II clinical trials. The consortium partners include three investigators from the UCL Cancer Institute, David Linch (gene therapy for haematological malignancies), Amit Nathwani (gene therapy for haemophilia) and Hans Stauss (gene therapy for haematological malignancies). The other partners are Adrian Thrasher (gene therapy for inherited immunodeficiencies, UCL Institute of Child Health), Robin Ali (gene therapy for eye disease, UCL Institute of Opthalmology) and Mary Collins (gene therapy for melanoma, Windeyer Institute). There are four active academic gene therapy clinical trials on the UCL campus, with two more having received GTAC approval, and fifteen at different stages of development. For each of these new projects, the supply of clinical grade gene transfer vector preparations is a major bottleneck. The first mission of the consortium is to provide resources and know-how for vector production and cell processing in the existing facilities at Chenies Mews and at the Great Ormond Street Hospital. Following this initial phase, these facilities will be extended to serve the gene therapy community nationally and internationally.
Takeuchi, Y., R. Myers, and O. Danos, Recombination and population mosaic of a multifunctional viral gene, adeno-associated virus cap. PLoS ONE, 2008. 3(2): p. e1634. Pubmed
Lorain, S., D.A. Gross, A. Goyenvalle, O. Danos, J. Davoust, and L. Garcia, Transient immunomodulation allows repeated injections of AAV1 and correction of muscular dystrophy in multiple muscles. Mol Ther, 2008. 16(3): p. 541-7. Pubmed
Chappert, P., M. Leboeuf, P. Rameau, D. Stockholm, R. Liblau, O. Danos, J.M. Davoust, and D.A. Gross, Antigen-driven interactions with dendritic cells and expansion of Foxp3+ regulatory T cells occur in the absence of inflammatory signals. J Immunol, 2008. 180(1): p. 327-34. Pubmed
Fougerousse, F., M. Bartoli, J. Poupiot, L. Arandel, M. Durand, N. Guerchet, E. Gicquel, O. Danos, and I. Richard, Phenotypic Correction of alpha-Sarcoglycan Deficiency by Intra-arterial Injection of a Muscle-specific Serotype 1 rAAV Vector. Mol Ther, 2007. 15(1): p. 53-61. pubmed
Bartoli, M., J. Poupiot, A. Vulin, F. Fougerousse, L. Arandel, N. Daniele, C. Roudaut, F. Noulet, L. Garcia, O. Danos, and I. Richard, AAV-mediated delivery of a mutated myostatin propeptide ameliorates calpain 3 but not alpha-sarcoglycan deficiency. Gene Ther, 2007. 14(9): p. 733-40. pubmed