E M Atkinson

The field of gene therapy, delivering genes to directly treat diseases, has had a remarkable year. This is no more evident than in the scope of the third annual meeting of the American Society of Gene Therapy (ASGT). Clear progress has been made in both ex vivo clinical protocols and in vivo administration. The meeting covered every major method of gene delivery, from injection of naked DNA to advanced synthetic gene delivery systems, as well as the major viral-based vectors. The optimism of the society was tempered, however, by the much-publicized death of a patient in a clinical trial at the University of Pennsylvania last year. There was a correspondingly high regulatory presence at the meeting, with several presentations by representatives of the US FDA and National Institutes of Health (NIH). Major clinical advances in gene therapy have been in genetic diseases, including hemophilia, severe combined immunodeficiency, and cystic fibrosis. Therapies are in later-stage clinical trials, and evidence of efficacy has been demonstrated, most notably by the apparent cure of SCID-affected children in Paris by ex vivo gene therapy with cytokine receptor subunit genes. Cancer gene therapy is also making significant headway, with many products entering phase II and III trials. Basic technology development is proceeding in vector targeting, enhancement of gene transfer efficiency, and regulating expression of therapeutic genes. In addition, basic research demonstrates the promise of new combined modes for treating diseases such as muscular dystrophy, lysosomal storage diseases and cardiovascular disease.

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

One of the challenges facing researchers working with viruses and gene therapy vectors is the need to rapidly assay for infectious virus. Current methods used to titer many viruses are cumbersome and are not amenable to handling large numbers of samples. Here we describe the development of an assay that can rapidly quantify infectious viruses and gene therapy vectors. The assay relies on biological amplification of viral sequences and hybridization of labeled probes to immobilized nucleic acid from infected cells. The amplification of the viral genome makes this a highly sensitive method. The assay is configured in a high-throughput format that has been used to detect recombinant adeno-associated virus (AAV), wild-type AAV and infectious adenovirus. The assay is quantitative, and can be used to titer virus preparations with or without a known standard.