Antibodies to three chondroitin sulfate-containing proteoglycans in squid skin recognize hexa- or longer chondroitin oligosaccharides as major antigenic determinants

Human Single-Chain Antibodies Reactive with Native Chondroitin Sulfate Detect Chondroitin Sulfate Alterations in Melanoma and Psoriasis

Chondroitin sulfate (CS) belongs to the group of glycosaminoglycans (GAGs), which are linear polysaccharides, located in the extracellular matrix and on the cell surface. To study the structure and distribution of CS in human skin and skin disorders, we have selected antibodies using phage display technique against CS. Four unique human anti-CS single-chain antibodies were selected: IO3D9, IO3H10, IO3H12, and IO4C2. We determined their amino acid sequence and evaluated their CS reactivity using ELISA and immunohistochemistry. Antibodies were reactive with CS, but not with other GAGs except for IO4C2, which was also reactive with heparin. Antibody IO3D9 showed a strong reactivity with highly sulfated CS (CSE). All antibodies displayed a different staining pattern in rat kidney, indicating the recognition of unique CS epitopes. In normal skin, the papillary dermis but not the reticular dermis was strongly stained. Antibody IO3H12 also stained basal keratinocytes. We applied these antibodies to study CS expression and localization in melanoma and psoriasis. A strong immunoreactivity with the extracellular matrix of melanoma metastases could be observed for all four antibodies, while in atypical nevi a less extensive reactivity with only the papillary dermis was observed. In psoriatic lesions, CS could be observed in the papillary dermis and in the reticular dermis, whereas the specific location in the papillary dermis found in normal skin was completely lost. In conclusion, human phage-display-derived anti-CS antibodies have been selected, characterized, and applied to detect CS alterations in skin conditions. Altered CS composition was detected in melanoma and psoriasis.

Polydispersity and heterogeneity of squid cranial cartilage proteoglycans as assessed by immunochemical methods and electron microscopy

The three populations of squid cranial cartilage proteoglycans, D1D1A, D1D1B and D1D2 appeared to have a high degree of polydispersity. Gel electrophoresis and immunoblotting analysis showed that polydispersity was mainly due to the variable size of chondroitin sulphate E chains. This was further ascertained after rotary shadowing electron microscopy of proteoglycan core proteins and glycosaminoglycan side chains and statistical analysis of the sizes measured for both components. Enzymic treatment of the proteoglycan core proteins produced different peptides from each population, suggesting that the observed heterogeneity of the proteoglycans is due to their core proteins. Antibodies were raised in rabbits against all proteoglycans and enzyme-linked immunosorbent analysis of proteoglycan core proteins revealed that the proteoglycans, even heterogeneous, shared many common epitopes. Part of the common proteoglycan epitopes were found to be located in chondroitin sulphate E chains. Heterogeneity of squid proteoglycans was also investigated by studying their interactions with collagen and it was found that only the two populations of high molecular mass, D1D1A and D1D2, were able to interact with only collagen type I, the latter stronger than the former.

A monoclonal antibody which recognizes a glycosaminoglycan epitope in both dermatan sulfate and chondroitin sulfate proteoglycans of human skin

Studies have been initiated to identify various cell surface and matrix components of normal human skin through the production and characterization of murine monoclonal antibodies. One such antibody, termed PG-4, identifies both cell surface and matrix antigens in extracts of human foetal and adult skin as the dermatan sulfate proteoglycans, decorin and biglycan, and the chondroitin sulfate proteoglycan versican. Treatment of proteoglycans with chondroitinases completely abolishes immunoreactivity for all of these antigens which suggests that the epitope resides within their glycosaminoglycan chains. Further evidence for the carbohydrate nature of the epitope derives from competition studies where protein-free chondroitin sulfate chains from shark cartilage react strongly; however, chondroitin sulfate chains from bovine tracheal cartilage fail to exhibit a significant reactivity, an indication that the epitope, although present in some chondroitin sulfate chains, does not consist of random chondroitin 4- or 6-sulfate disaccharides. The presence of the epitope on dermatan sulfate chains and on decorin was also demonstrated using competition assays. Thus, PG-4 belongs to a class of antibodies that recognize native epitopes located within glycosaminoglycan chains. It differs from previously described antibodies in this class in that it identifies both chondroitin sulfate and dermatan sulfate proteoglycans. These characteristics make PG-4 a useful monoclonal antibody probe to identify the total population of proteoglycans in human skin.

Chemical and immunological assay of the nonreducing terminal residues of chondroitin sulfate from human aggrecan

Samples of aggrecan chondroitin sulfate, isolated from normal human knee cartilages of individuals from fetal to 72 years of age, were digested with chondroitin lyases. The products were analyzed by fluorescence-based anion exchange high performance liquid chromatography to separate and quantitate nonreducing terminal structures, in addition to internal unsaturated disaccharide products. The predominant terminal structures were the monosaccharides, GalNAc4S and GalNAc4,6S as they were present on 85-90% of all chains. The remaining chains terminated with the disaccharides GlcAbeta1,3GalNAc4S and GlcAbeta1,3GalNAc6S. Marked changes in the relative abundance of these terminals were identified in the transition from growth cartilage to adult articular cartilage. First, terminal GalNAc residues were almost exclusively 4-sulfated in aggrecan from fetal through 15 years of age, but were approximately 50% 4,6-disulfated in aggrecans from adults (22-72 years of age). Second, the terminal disaccharide GlcAbeta1,3GalNAc4S was on approximately 7% of chains on aggrecan from fetal through 15 years of age, but on only approximately 3% of chains on adult aggrecan. In contrast, the proportion of chains terminating in GlcAbeta1,3GalNAc6S, approximately 9%, was unchanged from fetal to 72 years of age. This terminal disaccharide is proposed to be recognized by the widely used monoclonal antibody 3B3. However, chemical quantitation of the structure together with solid phase 3B3(-) immunoassay of fetal and adult aggrecans showed that the content of the terminal disaccharide does not necessarily correlate with immunoreactivity of the proteoglycan, as chain density and presentation on the solid phase are critical factors for recognition of chain terminals by 3B3. The quantitative results obtained from chemical analyses of all nonreducing termini of aggrecan chondroitin sulfate chains revealed important changes in chain termination that occur when cellular activities are altered as adult articular cartilage is formed after removal of growth cartilage. These findings are discussed in relation to specific enzymatic steps that generate the nonreducing termini of chains in the biosynthesis pathway of chondroitin sulfate proteoglycans and their modulation in tissue development and pathology.

Novel tetrasaccharides isolated from squid cartilage chondroitin sulfate E contain unusual sulfated disaccharide units GlcA(3-O-sulfate)beta1-3GalNAc(6-O-sulfate) or GlcA(3-O-sulfate)beta1-3GalNAc

We previously isolated novel tetrasaccharides containing 3-O-sulfated glucuronic acid from king crab cartilage chondroitin sulfate K and demonstrated that the disaccharide units containing 3-O-sulfated glucuronic acid were decomposed by chondroitinase ABC digestion (Sugahara, K., Tanaka, Y., Yamada, S., Seno, N., Kitagawa, H., Haslam, S. M., Morris, H. R., and Dell, A. (1996) J. Biol. Chem. 271, 26745-26754). The findings indicated the necessity to re-evaluate the disaccharide compositions of chondroitin sulfate preparations purified from other biological sources and analyzed using the above enzyme. In this study, to evaluate squid cartilage chondroitin sulfate E a series of even-numbered oligosaccharides were isolated after exhaustive digestion with sheep testicular hyaluronidase and subsequent fractionation by gel chromatography. The tetrasaccharide fraction was subfractionated by high performance liquid chromatography on an amine-bound silica column. Systematic structural analysis of five major fractions, h, l, m, n, and q, by fast atom bombardment mass spectrometry, enzymatic digestions in conjunction with capillary electrophoresis, and 500-MHz 1H NMR spectroscopy revealed one disulfated, three trisulfated, and one tetrasulfated tetrasaccharide structure: fraction h, GlcAbeta1-3GalNAc(4S)beta1-4GlcAbeta1-3GalNAc(4S); fraction l, GlcA(3S)beta1-3GalNAc(6S)beta1-4GlcAbeta1-3GalNAc(4S); fraction m, GlcA(3S)beta1-3GalNAc(4S)beta1-4GlcAbeta1-3GalNAc(4S); fraction n, GlcAbeta1-3GalNAc(4S,6S)beta1-4GlcAbeta1-3GalNAc(4S); and fraction q, GlcA(3S)beta1-3GalNAc(4S,6S)beta1-4GlcAbeta1-3GalNAc(4S), where 3S, 4S, and 6S represent 3-O-, 4-O- and 6-O-sulfate, respectively. The structures found in fractions h and m as well as the unsaturated counterpart of that found in fraction n have been reported, whereas those in fractions l and q are novel in that they contained unusual disulfated and trisulfated disaccharide units where GlcA(3S) is directly linked to GalNAc(6S) and GalNAc(4S,6S), respectively. These novel tetrasaccharide sequences are distinct from those found in other chondroitin sulfate isoforms and may play key roles in the biological functions and activities of chondroitin sulfate E not only from squid cartilage but also from mammalian cells and tissues.

The major 20-kDa polysaccharide of Staphylococcus epidermidis extracellular slime and its antibodies as powerful agents for detecting antibodies in blood serum and differentiating among slime-positive and -negative S. epidermidis and other staphylococci species

Staphylococcus epidermidis has been recognized as an important pathogen in immunocompromised hosts and patients with prosthetic or implanted medical devices. A highly adhesive extracellular material (slime or biofilm) produced by certain strains is associated with bacterial adherence to and growth on biomaterials contributing to pathogenesis of bacteremia. We have recently reported on the isolation and characterization of a sulfated 20-kDa acidic polysaccharide which constitutes slime's major component. Immunization of rabbits with crude slime and 20-kDa polysaccharide gave rise to readily reactive sera without manipulation of the 20-kDa polysaccharide structure. Immunological studies using purified polyclonal antibodies to 20-kDa polysaccharide by direct and competitive ELISA showed that they exhibit a high degree of reactivity and specificity with the homologous antigen. A significant proportion of the reactivity of antibodies to crude slime was also shown to be attributed to the 20-kDa polysaccharide. This polysaccharide is immunogenic in humans since blood sera derived from patients 10-15 days after confirmation of slime-producing S. epidermidis bacteremia gave approximately 16 times higher reactivity than that of healthy individuals. Antibodies to 20-kDa polysaccharide were able to recognize and react specifically with slime-positive S. epidermidis strains compared to slime-negative ones (2 to 5 times higher reactivity). Moreover, these antibodies exhibited statistically significant (P < 0.05) differences in the degree of reactivity among S. epidermidis and other staphylococci species. These results open a new area in the diagnosis of S. epidermidis infection by direct analysis in blood sera, in differentiating among slime-positive and slime-negative strains as well as in distinguishing slime-producing S. epidermidis from other staphylococci species by simple laboratory tests.