High affinity nucleic acid ligands to lectins

Details High affinity nucleic acid ligands to lectins High affinity nucleic acid ligands to lectins

1997-11-21

2001-08-28

Riley, Jezia (Department: 1656)

Chemistry: molecular biology and microbiology

Measuring or testing process involving enzymes or...

Involving nucleic acid

C435S091100, C435S091200, C435S007100, C536S022100, C536S023100, C536S024330, C530S300000

Reexamination Certificate

active

06280932

ABSTRACT:

FIELD OF THE INVENTION
Described herein are methods for identifying and preparing high-affinity nucleic acid ligands to lectins. Lectins are carbohydrate binding proteins. The method utilized herein for identifying such nucleic acid ligands is called SELEX, an acronym for Systematic Evolution of Ligands by EXponential enrichment. Specifically disclosed herein are high-affinity nucleic acid ligands to wheat germ agglutinin (WGA), L-selectin, E-selectin, and P-selectin.
BACKGROUND OF THE INVENTION
The biological role of lectins (non-enzymatic carbohydrate-binding proteins of non-immune origin; I. J. Goldstein et al., 1980, Nature 285:66) is inextricably linked to that of carbohydrates. One function of carbohydrates is the modification of physical characteristics of glyco-conjugates (i.e., solubility, stability, activity, susceptibility to enzyme or antibody recognition), however, a more interesting and relevant aspect of carbohydrate biology has emerged in recent years; the carbohydrate portions of glyco-conjugates are information rich molecules (N. Sharon and H. Lis, 1989, Science 246:227-234; K. Drickamer and M. Taylor, 1993, Annu. Rev. Cell Biol. 9:237-264; A. Varki, 1993, Glycobiol. 3:97-130). Within limits, the binding of carbohydrates by lectins is specific (i.e., there are lectins that bind only galactose or N-acetylgalactose; other lectins bind mannose; still others bind sialic acid and so on; K. Drickamer and M. Taylor, supra). Specificity of binding enables lectins to decode information contained in the carbohydrate portion of glyco-conjugates and thereby mediate many important biological functions.
Numerous mammalian, plant, microbial and viral lectins have been described (I. Ofek and N. Sharon, 1990, Current Topics in Microbiol. and Immunol. 151:91-113; K. Drickamer and M. Taylor, supra; I. J. Goldstein and R. D. Poretz, 1986, in The Lectins, p.p. 33-247; A. Varki, supra). These proteins mediate a diverse array of biological processes which include: trafficking of lysosomal enzymes, clearance of serum proteins, endocytosis, phagocytosis, opsonization, microbial and viral infections, toxin binding, fertilization, immune and inflammatory responses, cell adhesion and migration in development and in pathological conditions such as metastasis. Roles in symbiosis and host defense have been proposed for plant lectins but remain controversial. While the functional role of some lectins is well understood, that of many others is understood poorly or not at all.
The diversity and importance of processes mediated by lectins is illustrated by two well documented mammalian lectins, the asialoglycoprotein receptor and the serum mannose binding protein, and by the viral lectin, influenza virus hemagglutinin. The hepatic asialoglycoprotein receptor specifically binds galactose and N-acetylgalactose and thereby mediates the clearance of serum glycoproteins that present terminal N-acetylgalactose or galactose residues, exposed by the prior removal of a terminal sialic acid. The human mannose-binding protein (MBP) is a serum protein that binds terminal mannose, fucose and N-acetylglucosamine residues. These terminal residues are common on microbes but not mammalian glyco-conjugates. The binding specificity of MBP constitutes a non-immune mechanism for distinguishing self from non-self and mediates host defense through opsonization and complement fixation. Influenza virus hemagglutinin mediates the initial step of infection, attachment to nasal epithelial cells, by binding sialic acid residues of cell-surface receptors.
The diversity of lectin mediated functions provides a vast array of potential therapeutic targets for lectin antagonists. Both lectins that bind endogenous carbohydrates and those that bind exogenous carbohydrates are target candidates. For example, antagonists to the mammalian selectins, a family of endogenous carbohydrate binding lectins, may have therapeutic applications in a variety of leukocyte-mediated disease states Inhibition of selectin binding to its receptor blocks cellular adhesion and consequently may be useful in treating inflammation, coagulation, transplant rejection, tumor metastasis, rheumatoid arthritis, reperfusion injury, stroke, cyocardial infarction, burns, psoriasis, multiple sclerosis, bacterial sepsis, hypovolaemic and traumatic shock, acute lung injury, and ARDS.
The selectins, E-, P- and L-, are three homologous C-type lectins that recognize the tetrasaccharide, sialyl-Lewis
x
(C. Foxall et al, 1992, J. Cell Biol. 117,895-902). Selectins mediate the initial adhesion of neutrophils and monocytes to activated vascular endothelium at sites of inflammation (R. S. Cotran et al., 1986, J. Exp. Med. 164 661-; M. A. Jutila et al., 1989, J. Immunol. 143,3318-; J. G. Geng et al., 1990, Nature, 757; U. H. Von Adrian et al., 1994, Am J. Physiol. Heart Circ. Physiol. 263, H 1034-H1044). In addition, L-selectin is responsible for the horning of lymphocytes to peripheral and mesenteric lymph nodes (W. M. Gallatin et al., 1983, Nature 304,30; T. K. Kishimoto et al., 1990, Proc. Natl. Acad. Sci. 87,2244-) and P-selectin mediates the adherence of platelets to neutrophils and monocytes (S- C. Hsu-Lin et al., 1984, J. Biol. Chem. 259,9121).
Selectin antagonists (antibodies and carbohydrates) have been shown to block the extravasation of neutrophils at sites of inflammation (P. Piscueta and F. W. Luscinskas, 1994, Am. J. Pathol. 145, 461-469), to be efficacious in animal models of ischemia/reperfusion (A. S. Weyrich et al., 1993, J. Clin. Invest. 91,2620-2629; R. K. Winn et al., 1993, J. Clin. Invest. 92, 2042-2047), acute lung injury (M. S. Mulligan et al., 1993, J. Immunol. 151, 6410-6417; A Seekamp et al., 1994, Am. J. Pathol. 144, 592-598), insulitis/diabetes (S. D. Yang et al., 1993, Proc. Natl. Acad. Sci. 90,10494-10498), meningitis (C. Granet et al., 1994, J. Clin. Invest. 93, 929-936), hemorrhagic shock (R. K. Winn et al., 1994, Am J. Physiol. Heart Circ. Physiol. 267, H2391-H2397) and transplantation. In addition, selectin expression has been documented in models of arthritis (R. Jamar et al., 1995, Radiology 194, 843-850), experimental allergic encephalomyelitis (J. M. Dopp et al., 1994, J. Neuroimmunol. 54, 129-144), cutaneous inflammation (A. Siber et al., 1994, Lab. Invest. 70, 163-170) glomerulonephritis (P. G. Tipping et al., 1994, Kidney Int. 46, 79-88), on leukaemic cells and colon carcinomas (R. M. Lafrenie et al., 1994, Eur. J. Cancer [A] 30A, 2151-2158) and L-selectin receptors have been observed in myelinated regions of the central nervous system (K. Huang et al., 1991, J. Clin. Invest. 88, 1778-1783). These animal model data strongly support the expectation of a therapeutic role for selectin antagonists in a wide variety of disease states in which host tissue damage is neutrophil-mediated.
Other examples of lectins that recognize endogenous carbohydrates are CD22&bgr;, CD23, CD44 and sperm lectins (A. Varki, 1993, Glycobil.3, 97-130; P. M. Wassarman, 1988, Ann. Rev. Biochem. 57, 415-442). CD22&bgr; is involved in early stages of B lymphocyte activation; antagonists may modulate the immune response. CD23 is the low affinity IgE receptor; antagonists may modulate the IgE response in allergies and asthma. CD44 binds hyaluronic acid and thereby mediates cell/cell and cell/matrix adhesion; antagonists may modulate the inflammatory response. Sperm lectins are thought to be involved in sperm/egg adhesion and in the acrosomal response; antagonists may be effective contraceptives, either by blocking adhesion or by inducing a premature, spermicidal acrosomal response.
Antagonists to lectins that recognize exogenous carbohydrates may have wide application for the prevention of infectious diseases. Many viruses (influenza A, B and C; Sendhi, Newcastle disease, coronavirus, rotavirus, encephalomyelitis virus, enchephalomyocarditis virus, reovirus, paramyxovirus) use lectins on the surface of the viral particle for attachment to cells, a prerequisite for infection; antagonists to these lectins are expected to prevent infection (A. Varki, 1993, G

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