Scientific Abstract

Proposal No. IBD-0078
Principal Investigator:  Takeshi Sano, Ph.D.
Applicant Organization:  Beth Israel Deaconess Medical Center (Boston, Massachusetts, U.S.A.)
Project Title:  A colon-directed gene transfer technology for gene therapy of inflammatory bowel disease
Period of Award:  November 1, 2003 - October 31, 2005

Our goal is to develop an effective gene therapy for inflammatory bowel disease (IBD). Our strategy is to repress intense local inflammation in the colon by using gene insertion to produce anti-inflammatory cytokines, such as interleukin-10 (IL-10) and IL-4, or antagonists and antibodies against pro-inflammatory cytokines. Although systemic daily administration of purified IL-10 has shown some therapeutic effect in Crohn's disease, the very short life of IL-10 and other anti-inflammatory cytokines in the circulation necessitates their frequent administration. This may also lead to possible detrimental effects of these cytokines on other tissues and organs. These problems make this strategy unrealistic for the therapy of IBD. Gene therapy approaches are particularly attractive, since localized, long-term expression of anti-inflammatory cytokines at inflamed lesions is potentially achievable. In fact, a few recent studies have demonstrated the potential efficacy of virus-mediated delivery of the IL-10 gene to the colon for the therapy of IBD.

One genuine concern in an effort to bring this and other gene therapy approaches to the clinical arena is with the safety in using viral vectors in human subjects. The need for a much greater attention to safety than previously considered has now become apparent for any gene therapy protocol prior to its implementation in human subjects.

This project aims to develop strategies for safe and focused virus-mediated delivery of therapeutic transgenes to inflamed lesions in the colon toward the realization of gene therapy of IBD. Particular emphasis will be placed on the safety of virus-mediated gene transfer, which is associated with uncontrolled migration of viral particles from target sites and subsequent transduction of non-target tissues and organs by viral vectors, and immune responses to viral vectors and transduced cells.

We have recently developed a novel gene transfer technology, which uses solid microbeads as carriers for viral vectors for their focused delivery. Viral particles (adenoviral vectors or adeno-associated viral vectors) can be immobilized tightly on the surfaces of microbeads by using the extremely stable streptavidin-biotin interaction, while maintaining the infectivity of the viral vectors. Such immobilized viral vectors are stable, as no dissociation of viral particles from the solid surface occurs under physiological conditions. Interestingly, such virus-microbead conjugates can infect target cells at efficiencies much greater than the equivalent viral vectors used free in solution. In addition, these virus-microbead conjugates can efficiently infect target cells, which are otherwise not permissive to the same viral vectors used in solution.

A key feature of this gene transfer technology is that the infection sites by viral vectors are equal to the contact sites between target cells and virus-microbead conjugates. This allows focused delivery of transgenes to target sites with high transduction efficiencies by strategic placement of virus-microbead conjugates at the site of interest. Since each viral particle on the microbeads either mediates infection of a cell or stays on the microbeads, no free viral particles should be present.

These characteristics should offer enormous safety enhancements to virus-mediated gene transfer strategies for the following reasons: (i) Virus-mediated gene transfer should be restricted to only the site of interest by strategic placement of the virus-microbead conjugates in the particular site; (ii) Since no free viral particles are present, uncontrolled transduction of other tissues or organs by viral vectors can be eliminated, and immune responses to viral vectors can be minimized; and (iii) Due to the high infection efficiency and the ability to infect a wider range of cell types (broader tropism), fewer numbers of viral particles are needed than those used free in solution. These and other characteristics suggest that this gene transfer technology could be extremely useful for the development of gene therapy for IBD. We propose to investigate the potential of this gene transfer technology for safe, efficient, and focused delivery of the genes for anti-inflammatory factors to the colon toward the realization of gene therapy of IBD.