Previous Claims Of siRNA Therapeutic Effects Called Into Question By Report In Human Gene Therapy

Main Category: Genetics
Also Included In: Immune System / Vaccines
Article Date: 04 Sep 2008 - 2:00 PDT

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The many recent reports documenting the therapeutic efficacy of short interfering RNAs (siRNAs) in animal models of human disease may actually be describing non-specific therapeutic effects related to the ability of siRNA to activate an immune response, according to a paper in the September 2008 issue (Volume 19, Number 9) of Human Gene Therapy, a peer-reviewed journal published by Mary Ann Liebert, Inc. The paper, which was published "instant online," is available free online at http://www.liebertpub.com/hum

Marjorie Robbins, Adam Judge, Ellen Ambegia, Catherine Choi, Ed Yaworski, Lorne Palmer, Kevin McClintock, and Ian MacLachaln of Protiva Biotherapeutics (Burnaby, BC Canada), in a paper entitled, "Misinterpreting the Therapeutic Effects of siRNA Caused by Immune Stimulation," emphasize the need for researchers to design siRNA studies that incorporate suitable controls to differentiate the disease-modulating effect of an siRNA from its ability to stimulate an innate immune response.

siRNAs have been highly touted for their ability to target very specifically and selectively the disease-causing factors in a range of disorders, from viral infections to tumors and inflammatory and immunologic processes. However, siRNA also has the potential to activate innate immunity and the production of interferons, which can in turn bring about therapeutic effects in a range of disease models.

The authors of this paper contend that, "surprisingly few of the reported studies have adequately tested, or controlled, for the potential effects of siRNA-mediated immune stimulation."

In the current study, use of a commonly used control siRNA sequence called GFP siRNA, which has only a minimal capacity to activate the immune system, clearly showed the striking difference between the immunostimulatory potential of GFP siRNA and of some other siRNAs. Using a mouse model of influenza, the authors demonstrated that the anti-viral activity of siRNA is mainly due to non-specific stimulation of the immune system rather than to a targeted attack on the disease-causing virus.

"siRNA holds tremendous potential as a research tool, however its clinical development is still in its infancy. The study by Robbins et al. points out a very important issue regarding non-specific effects that should be considered when designing and evaluating siRNA strategies," says James M. Wilson, MD, PhD, Editor-in-Chief, and Head of the Gene Therapy Program, Division of Medical Genetics, University of Pennsylvania School of Medicine, in Philadelphia.

Notes:

Human Gene Therapy, the Official Journal of the European Society of Gene and Cell Therapy (www.esgct.org), the British Society for Gene Therapy (http://www.bsgt.org), and the French Society of Cell and Gene Therapy (http://www.sftcg.fr), is an authoritative peer-reviewed journal published monthly in print and online that presents reports on the transfer and expression of genes in mammals, including humans. Related topics include improvements in vector development, delivery systems, and animal models, particularly in the areas of cancer, heart disease, viral disease, genetic disease, and neurological disease, as well as ethical, legal, and regulatory issues related to the gene transfer in humans. Tables of contents and a free sample issue may be viewed online at http://www.liebertpub.com/

Mary Ann Liebert, Inc is a privately held, fully integrated media company known for establishing authoritative peer-reviewed journals in many promising areas of science and biomedical research, including Tissue Engineering, Stem Cells and Development, and Cloning and Stem Cells. Its biotechnology trade magazine, Genetic Engineering & Biotechnology News (GEN), was the first in its field and is today the industry's most widely read publication worldwide.

Source:
Vicki Cohn
Mary Ann Liebert, Inc.
140 Huguenot St.,
New Rochelle,
NY 10801-5215
Mary Ann Liebert, Inc./Genetic Engineering News