The University of Georgia College of Veterinary Medicine

Tripp Lab, UGA - RNA Interference

Viral Immunology:Tripp Laboratory

RNA Interference

RNA-mediated silencing is a naturally occurring process for controlling gene expression having its branches in the evolutionary tree ranging from plants to man. This process, referred to as RNA interference (RNAi), has become a powerful tool amenable to high-throughput approaches making RNAi important tool in drug target screening, and for development of therapeutic drugs, particularly anti-viral drugs.

RNAi silencing is initiated when double-stranded RNA (dsRNA) is processed into small interfering RNAs (siRNA) between 19-26 base pairs in length by an RNaseIII enzyme called Dicer. These siRNAs are subsequently incorporated into RNA-induced silencing complexes (RISC) that target cognate messenger RNA (mRNA) for cleavage to mediate gene suppression.

RNAi has several important advantages over other methods for targeted inhibition of gene expression (e.g. antisense, catalytic RNA and DNA molecules, and homologous recombination), as unlike these methods, RNAi has broad cross-species application, the mechanism of action is gene-specific so there is no or little off-target effects, synthetic siRNAs are relatively easy to manufacture, and since siRNAs are formed by a natural endogenous process, all cells carry the machinery needed to mediate gene silencing.

Given these advantages, RNAi has become a gene-silencing tool of choice; however, to be effective RNAi mediators such as synthetic siRNAs must be efficiently delivered into target cells. Synthetic siRNAs can be delivered to mammalian cells by a variety of methods including use of lipophilic agents and by electroporation; however these methods are limited by several factors that negatively impact RNAi efficacy including toxicity associated with the delivery agent, cell death associated with the delivery method, and the transient nature of siRNA gene silencing linked to degradation by cellular enzymes. Efforts are underway to modify these effects, including minimizing the charge of the siRNA phosphate backbone to facilitate its entry into cells; however it is clear that development of efficient siRNA delivery methods is critical for the therapeutic potential of RNAi.

The objectives of the laboratory are to optimize methods for targeting and delivery of novel siRNA drugs to be used in a disease intervention strategy for influenza and other respiratory virus infections. Studies from our laboratory in collaboration with our industry partner have shown that we can design and in vitro evaluate candidate siRNA drugs using lipophilic delivery agents; however, in vivo evaluation remains difficult due to limitations associated with delivery and targeting. Our long-term goal is to develop novel in vivo cell targeting and delivery approaches for siRNA candidates to be used therapeutically across a range of virus strains. The ongoing laboratory research is innovative as we are developing new and novel drug delivery agents and methods to inhibit influenza and other viruses across a broad range of strains, and are provide an effective delivery mechanism for disease intervention strategies to protect public health.

This page last updated March 10, 2010 .