Human single chain antibodies against heparin: selection, characterization, and effect on coagulation.

Heparin, located in mast cells and basophilic granulocytes, is widely used as an anticoagulant. It belongs to a class of linear polysaccharides called glycosaminoglycans (GAGs). Using phage display technology, we have selected 19 unique human antiheparin antibodies. Some antibodies react almost exclusively with heparin, others also react with the structurally related heparan sulfate, and some with chondroitin sulfate. In all cases, sulfate groups are essential for binding. For activity of some antibodies, O-sulfation is more important than N-sulfation. Antibodies are reactive with heparin in mast cells. Each antibody showed a defined staining pattern on cryosections of rat kidney, pancreas, and testis. Enzymatic digestion with glycosidases on tissue sections further indicated that the antibodies are specific for GAGs. All antibodies recognize a unique epitope. The effect of the antibodies on heparin as an anticoagulant was also studied. There were 3 antibodies that were very effective inhibitors of heparin action in the activated partial thromboplastin time (APTT) clotting assay, and their effect was related to the amount of heparin bound. Some antibodies reacted strongly with the pentasaccharide, which interacts with antithrombin III. The human antibodies selected represent unique tools to study the structure, location, and function of heparin and related GAGs, and some may be used as blocking agents

Heparan sulphate epitope-expression is associated with the inflammatory response in metastatic malignant melanoma.

Item does not contain fulltextHeparan sulphate (HS) represents a heterogeneous class of molecules on cell membranes and extracellular matrices. These molecules are involved in a variety of biological processes, including immune responses, through their binding and functional modulation of proteins. Recently a panel of HS-epitope-specific, human single chain antibodies have been generated by phage display, facilitating analysis of the structural heterogeneity of HS in relation to pathological conditions. In a pilot study a heterogeneous staining pattern in melanoma metastases was observed with one of the clones (EW4G1). Using a double-staining technique, the expression of this epitope was studied in 12 metastatic melanoma lesions in relation to the presence of a CD3(+) cell infiltrate. Different staining patterns with EW4G1 were observed in the different lesions. The different staining patterns were associated with the presence and pattern of inflammation with CD3(+) cells. A pronounced staining pattern of blood vessels with EW4G1 was associated with a more or less brisk presence of CD3(+) cells, while a pronounced staining of tumour cells or tumour cell matrix or absence of staining with EW4G1 was associated with absence of CD3(+) cells. These results suggest a dualistic role for HS in the recruitment and intratumoural migration of CD3(+) cells, depending on the location of expression of its epitope recognized by EW4G1. Further characterization of the structural diversity of HS and its function in T-cell recruitment and migration is therefore warranted, since detailed understanding of this relation may provide new targets for therapeutic intervention, such that better homing and migration of T cells (in)to tumours might be achieved in immunologically based treatment strategies

Localization and characterization of melanoma-associated glycosaminoglycans: differential expression of chondroitin and heparan sulfate epitopes in melanoma.

Item does not contain fulltextGlycosaminoglycans (GAGs) are anionic polysaccharides present on cells and in the extracellular matrix (ECM). They likely play a role in tumor formation because of their capacity to bind and modulate a variety of proteins including growth factors, cytokines, and proteases. Using a panel of (human) phage display-derived anti-GAG antibodies, the location and expression of GAG epitopes in human cutaneous melanocytic lesions was studied. Antibodies EW4E1 and EW4G2 identified a melanoma-associated chondroitin sulfate/heparan sulfate epitope, whereas antibody EW4B7 recognized a melanoma-associated heparan sulfate epitope. These antibodies showed a high reactivity with blood vessels and ECM in cutaneous melanoma tumors, whereas their reactivity with nevi was very low. Using a set of defined oligosaccharides it was established that sulfate groups are of main importance in the binding to the antibodies and that glycomimetics can mimic natural oligosaccharides. In xenografts of melanoma cell line MeL57, a strong association of GAG epitopes with an injected fluorescent fluid flow tracer was observed. In uveal melanoma antibody, EW4E1 proved to be a sensitive probe for the detection of the geometry of ECM structures, known to have prognostic value. Taken together, data indicate that in melanoma a defined set and location of GAG epitopes are present with possible functional significance