HIGH-AFFINITY OLIGONUCLEOTIDE LIGANDS TO HUMAN IGE INHIBIT BINDING TOFC-EPSILON RECEPTOR-I

Using the systematic evolution of ligands by exponential enrichment (S ELEX) method, we have identified oligonucleotides that bind to human I gE with high affinities and high specificity. These ligands were isola ted from three pools of oligonucleotides, each representing 10(15) mol ecules: two pools contained 2'-NH2 pyrimidine-modified RNA with either 40 or 60 randomized sequence positions, and the third pool contained ssDNA with 40 randomized sequence positions. Based an sequence and str ucture similarities, these oligonucleotide IgE ligands were grouped in to three families: 2'-NH2 RNA group A ligands are represented by the 3 5-nucleotide truncate IGEL1.2 (K-d = 30 nM); 2'-NHd RNA group B ligand s by the 25-nucleotide truncate IGEL2.2 (K-d = 35 nM); and the ssDNA g roup ligands by the 37-nucleotide truncate D17.4 (K-d = 10 nM). Second ary structure analysis suggests G quartets for the 2'-NH2 RNA ligands, whereas the ssDNA ligands appear to form stem-loop structures. Using rat basophilic leukemia cells transfected with the human high-affinity IgE receptor Fc epsilon RI, we demonstrate that ligands IGEL1.2 and D 17.4 competitively inhibit the interaction of human IgE with Fc epsilo n R1. Furthermore, this inhibition is sufficient to dose-dependently b lock IgE-mediated serotonin release from cells triggered with IgE-spec ific Ag or anti-IgE Abs. Therefore, these oligonucleotide ligands repr esent a novel class of IgE inhibitors that may prove useful in the fig ht against allergic diseases.