High affinity nucleic acid ligands of complement system proteins

#Described herein are methods for identifying and preparing high-affinity Nucleic Acid Ligands to Complement System Proteins. The method utilized herein for identifying such Nucleic Acid Ligands is called SELEX™, an acronym for Systematic Evolution of Ligands by EXponential enrichment. Described herein are methods for identifying and preparing high-affinity Nucleic Acid Ligands to the Complement System Proteins C1q, C3 and C5. This invention includes high affinity Nucleic Acid Ligands of C1q, C3 and C5. Also disclosed are RNA ligands of C1q, C3 and C5. Also disclosed are Nucleic Acid Ligands that inhibit and/or activate the Complement System. The oligonucleotides of the present invention are useful as pharmaceuticals or diagnostic agents.

#The complement system comprises a set of at least 20 plasma and membrane proteins that act together in a regulated cascade system to attack extracellular forms of pathogens (Janeway et al. (1994) Immunobiology: The Immune System in Health and Disease. Current Biology Ltd, San Francisco, pp. 8:35-8:55; Morgan (1995) Crit. Rev. in Clin Lab. Sci. 32(3):265-298). There are two distinct enzymatic activation cascades, the classical and alternative pathways, and a non-enzymatic pathway known as the membrane attack pathway.

#The classical pathway is usually triggered by an antibody bound to a foreign particle. It comprises several components, C1, C4, C2, C3 and C5 (listed by order in the pathway). Initiation of the classical pathway of the Complement System occurs following binding and activation of the first complement component (C1) by both immune and non-immune activators (Cooper (1985) Adv. Immunol. 37:151). C1 comprises a calcium-dependent complex of components C1q, C1r and C1s, and is activated through binding of the C1q component. C1 q contains six identical subunits and each subunit comprises three chains (the A, B and C chains). Each chain has a globular head region which is connected to a collagen-like tail. Binding and activation of C1q by antigen-antibody complexes occurs through the C1q head group region. Numerous non-antibody C1q activators, including proteins, lipids and nucleic acids (Reid et al. (1993) The Natural Immune System: Humoral Factors. E. Sim, ed. IRL Press, Oxford, p. 151) bind and activate through a distinct site on the collagen-like stalk region.

#FIG. 1 shows the results of an inhibition assay in which 2′-F RNA ligands C 12 (SEQ ID NO:59), A6 (SEQ ID NO:48), K7 (SEQ ID NO:50), C9 (SEQ ID NO:58), E5c (SEQ ID NO:47) and F8 (SEQ ID NO:49) to human C5 were incubated with antibody-coated sheep erythrocytes and whole human serum. The results are presented as optical density (OD) versus concentration of ligand in nM.

#FIG. 2 shows the % C5a generation as a function of concentration of clone C6 (SEQ ID NO:51).

#FIG. 3A shows a sequencing gel of 5′-kinase-labeled clone C6 (SEQ ID NO:51) after alkaline hydrolysis or digestion with T1 nuclease. The 3′-sequence (5′-end labeled) is aligned with the alkaline hydrolysis ladder. On the left is the T1 ladder and on the right are RNA selected with 5× and 1× concentrations of C5. The boundary where removal of a base eliminates binding is shown by the arrow. The asterisk shows a G which is hypersensitive to T1.

#This application describes Nucleic Acid Ligands to Complement System Proteins identified generally according to the method known as SELEX. As stated earlier, the SELEX technology is described in detail in the SELEX Patent Applications which are incorporated herein by reference in their entirety. Certain terms used to describe the invention herein are defined as follows:

#“Nucleic Acid Ligand” as used herein is a non-naturally occurring Nucleic Acid having a desirable action on a Target. A desirable action includes, but is not limited to, binding of the Target, catalytically changing the Target, reacting with the Target in a way which modifies/alters the Target or the functional activity of the Target, covalently attaching to the Target as in a suicide inhibitor, and facilitating the reaction between the Target and another molecule. In the preferred embodiment, the desirable action is specific binding to a Target molecule, such Target molecule being a three dimensional chemical structure other than a polynucleotide that binds to the Nucleic Acid Ligand through a mechanism which predominantly depends on Watson/Crick base pairing or triple helix binding, wherein the Nucleic Acid Ligand is not a Nucleic Acid having the known physiological function of being bound by the Target molecule. Nucleic Acid Ligands include Nucleic Acids that are identified from a Candidate Mixture of Nucleic Acids, said Nucleic Acid Ligand being a ligand of a given Target by the method comprising: a) contacting the Candidate Mixture with the Target, wherein Nucleic Acids having an increased affinity to the Target relative to the Candidate Mixture may be partitioned from the remainder of the Candidate Mixture; b) partitioning the increased affinity Nucleic Acids from the remainder of the Candidate Mixture; and c) amplifying the increased affinity Nucleic Acids to yield a ligand-enriched mixture of Nucleic Acids.

#“Candidate Mixture” is a mixture of Nucleic Acids of differing sequence from which to select a desired ligand. The source of a Candidate Mixture can be from naturally-occurring Nucleic Acids or fragments thereof, chemically synthesized Nucleic Acids, enzymatically synthesized Nucleic Acids or Nucleic Acids made by a combination of the foregoing techniques. In a preferred embodiment, each Nucleic Acid has fixed sequences surrounding a randomized region to facilitate the amplification process.