Structural characterization of N-glycans from the freshwater snail Biomphalaria glabrata cross-reacting with Schistosoma mansoni glycoconjugates

The human parasitic trematode Schistosoma mansoni has a complex life cycle that includes the freshwater snail Biomphalaria glabrata as intermediate host. Within each stage, the parasite synthesizes a wide array of glycoconjugates, exhibiting, in part, unique carbohydrate structures. In addition, the parasite expresses definitive host-like sugar epitopes, such as Lewis X determinants, supporting the concept of carbohydrate-mediated molecular mimicry as an invasion and survival strategy. In the present study, we investigated whether common carbohydrate determinants occur also at the level of the intermediate host. To this end, a structural characterization of hemolymph glycoprotein-N-glycans of B. glabrata was performed. N-glycans were released from tryptic glycopeptides and labeled with 2-aminopyridine. Sugar chains serologically cross-reacting with S. mansoni glycoconjugates were isolated by immunoaffinity chromatography using a polyclonal antiserum directed against schistosomal egg antigens and fractionated by Aleuria aurantia lectin affinity chromatography and high-performance liquid chromatography. Obtained glycans were analyzed by different mass spectrometric techniques as well as by monosaccharide constituent and linkage analysis. The results revealed a highly heterogeneous oligosaccharide pattern. Cross-reacting species represented about 5% of the total glycans and exhibited a terminal Fuc(alpha1-3)GalNAc unit, a (1-2)-linked xylosyl residue, or both types of structural motifs. In conclusion, our study demonstrates the presence of common carbohydrate epitopes also at the level of S. mansoni and its intermediate host.     

Characterization of glycosphingolipids from Schistosoma mansoni eggs carrying Fuc(alpha1-3)GalNAc-, GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc- and Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc- (Lewis X) terminal structures.

The carbohydrate moieties of glycosphingolipids from eggs of the human parasite, Schistosoma mansoni, were enzymatically released, labelled with 2-aminopyridine (PA), fractionated and analysed by linkage analysis, partial hydrolysis, enzymatic cleavage, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nano-electrospray ionization mass spectrometry. Apart from large, highly fucosylated structures with five to seven HexNAc residues, we found short, oligofucosylated species containing three to four HexNAc residues. Their structures have been determined as Fuc(alpha1-3)GalNAc(beta1-4)[ +/- Fuc (alpha1-3)]GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)GlcNAc(beta1-3)GalNAc(beta1-4) Glc-PA, Fuc(alpha1-3)GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-4) GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, and Fuc(alpha1-3) GalNAc(beta1-4)[ +/- Fuc(alpha1-2) +/- Fuc(alpha1-2)Fuc(alpha1-3)]Glc NAc(beta1-3)GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA. The last structure exhibits a trifucosyl sidechain previously identified on the cercarial glycocalyx. These structures stress the importance of 3-fucosylated GalNAc as a terminal epitope in schistosome glycoconjugates. To what degree these glycans contribute to the pronounced antigenicity of S. mansoni egg glycolipids remains to be determined. In addition, we have identified the compounds GlcNAc(beta1-3)GalNAc(beta1-4)Glc-PA, Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3) GalNAc (beta1-4)Glc-PA, the latter of which is a Lewis X-pentasaccharide identical to that present on cercarial glycolipids, as well as Gal(beta1-3)GalNAc(1-4)Gal(1-4)Glc-PA, which corresponds to asialogangliotetraosylceramide and is most probably derived from the mammalian host.     

Targeted glycoproteomic analysis reveals that kappa-5 is a major, uniquely glycosylated component of Schistosoma mansoni egg antigens

Glycans present on glycoproteins from the eggs of the parasite Schistosoma mansoni are mediators of various immune responses of the human host, including T-cell modulation and granuloma formation, and they are the target of glycan-specific antibodies. Here we have analyzed the glycosylation of kappa-5, a major glycoprotein antigen from S. mansoni eggs using a targeted approach of lectin purification followed by mass spectrometry of glycopeptides as well as released glycans. We demonstrate that kappa-5 has four fully occupied N-glycosylation sites carrying unique triantennary glycans composed of a difucosylated and xylosylated core region, and immunogenic GalNAcβ1-4GlcNAc (LDN) termini. Furthermore, we show that the kappa-5 specific IgE antibodies in sera of S. mansoni-infected individuals are directed against the core region of the kappa-5 glycans. Whereas two previously analyzed immunomodulatory egg glycoproteins, IPSE/alpha-1 and omega-1, both express diantennary N-glycans with a difucosylated core and one or two Galβ1-4(Fucα1-3)GlcNAc (Lewis X) antennae, the kappa-5 glycosylation appears unique among the major soluble egg antigens of S. mansoni. The distinct structural and antigenic properties of kappa-5 glycans suggest a specific role for kappa-5 in schistosome egg immunogenicity.     

Localization of carbohydrate determinants common to Biomphalaria glabrata as well as to sporocysts and miracidia of Schistosoma mansoni

The presence of antigenic carbohydrate epitopes shared by Biomphalaria glabrata as well as by the sporocysts and miracidia representing snail-pathogenic larval stages of Schistosoma mansoni was assayed by immunohistochemical staining of paraformaldehyde-fixed tissues. To this end, both polyclonal rabbit antiserum raised against soluble egg antigens (SEA) of S. mansoni and monoclonal antibodies recognizing the carbohydrate epitopes LDN [GalNAc(beta1-4)GlcNAc(beta1-)], F-LDN [Fuc(alpha1-3)GalNAc(beta1-4)GlcNAc(beta1-)], LDN-F [GalNAc(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-)], LDN-DF [GalNAc(beta1-4)[Fuc(alpha1-2)Fuc(alpha1-3)]GlcNAc(beta1-)] and Lewis X [Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-)] were used. Intriguingly, anti-SEA serum as well as anti-F-LDN antibodies displayed significant binding in the foot region, anterior tissue and the hepatopancreas of uninfected snails, whereas the Lewis X epitope was only weakly detectable in the latter tissue. In contrast, increased binding of antibodies recognizing LDN, LDN-F and LDN-DF was observed in infected snail tissue, in particular in regions involved in sporocystogenesis, in addition to an enhanced binding of anti-SEA serum and antibodies reacting with F-LDN. A pronounced expression of most of these carbohydrate antigens was also observed at the surface of miracidia. Hence, the detection of shared carbohydrate determinants in uninfected snail tissue, sporocysts and miracidia may support the hypothesis of carbohydrate-based molecular mimicry as a survival strategy of S. mansoni.     

Novel polyfucosylated N-linked glycopeptides with blood group A, H, X, and Y determinants from human small intestinal epithelial cells

A novel type of N-linked glycopeptides representing a major part of the glycans in human small intestinal epithelial cells from blood group A and O individuals were isolated by gel filtrations and affinity chromatography on concanavalin A-Sepharose and Bandeiraea simplicifolia lectin I-Sepharose. Sugar composition, methylation analysis, 1H NMR spectroscopy of the underivatized glycopeptides and FAB-mass spectrometry and electron impact-mass spectrometry of the permethylated glycopeptides indicated a tri- and tetra-antennary structure containing an intersecting N-acetylglucosamine and an alpha (1----6)-linked fucose residue in the core unit for the majority of the glycans. In contrast to most glycopeptides of other sources, the intestinal glycopeptides were devoid of sialic acid, but contained 6-7 residues of fucose. The outer branches contained the following structures: Fuc alpha 1-2Gal beta 1-3GleNAc beta 1- (H type 1) Fuc alpha 1-2Gal beta 1-4GleNAc beta 1- (H type 2) Gal beta 1-4 (Fuc alpha 1-3)GlcNAc beta 1- (X) Fuc alpha 1-2Gal beta 1-4(Fuc alpha 1-3)GleNAc beta 1- (Y) GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta 1-3GleNAc beta 1- (A type 1) GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta 1-4GleNAc beta 1- (monofucosyl A type 2) GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta 1-4 (Fuc alpha 1-3)GlcNAc beta 1- (trifucosyl A type 2) The blood group determinant structures were mainly of type 2, whereas glycolipids from the same cells contained mainly type 1 determinants. The polyfucosylated glycans represent a novel type of blood group active glycopeptides. The unique properties of the small intestinal glycopeptides as compared with glycopeptides of other tissue sources may be correlated with the specialized functional properties of the small intestinal epithelial cells.     

N-Glycosylation patterns of hemolymph glycoproteins from Biomphalaria glabrata strains expressing different susceptibility to Schistosoma mansoni infection

Comparative analyses of the N-glycosylation pattern of hemolymph glycoproteins from Biomphalaria glabrata strains Puerto Rico (BgPR) and Salvador (BgBS-90), differing in their susceptibility towards Schistosoma mansoni infection, were performed by Western blotting, enzyme-linked immunosorbent assays, two-dimensional high-performance liquid chromatography and mass spectrometry. Obtained data demonstrated an enhanced expression of serologically cross-reacting, fucosylated carbohydrate epitopes by the highly susceptible BgPR-strain in comparison to the resistant BgBS-90-strain. In particular, glycoproteins of BgPR snails exhibited larger amounts of glycans with (β1-2)-linked xylose or terminal Fuc(α1-3)GalNAc(β1-4)[±Fuc(α1-3)]GlcNAc(β1-)-units which are known to mediate cross-reactivity with schistosomal glycoconjugates. This finding could be corroborated by immunohistochemical studies showing again an enhanced expression of such carbohydrate epitopes in BgPR tissue. Hence, our results provide evidence for a correlation of B. glabrata susceptibility towards S. mansoni infection and the expression of carbohydrate determinants shared by the parasite and its intermediate host.     

Antibody responses to the fucosylated LacdiNAc glycan antigen in Schistosoma mansoni-infected mice and expression of the glycan among schistosomes

Infections of animals with parasitic worms, such as Schistosoma mansoni, induce humoral immune responses to carbohydrate antigens, raising the possibility that such antigens might be useful targets for the development of vaccines and new diagnostic approaches. Here we describe the identification of fucosylated LacdiNAc (LDNF) [GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc-R] as a new carbohydrate antigen in S. mansoni that induces humoral immune responses in infected mice. The presence of antibodies was determined by ELISA using a neoglycoconjugate synthesized to express LDNF sequences. Sera from S. mansoni-infected, but not uninfected, mice contain IgM, IgG, IgA, and IgE antibodies to LDNF. The IgG antibodies are primarily of the IgG1 and IgG3 subclasses, with no detectable levels of the complement-fixing IgG2a and IgG2b isotypes. An IgM monoclonal antibody, designated SMLDNF1, was generated from the spleens of S. mansoni-infected mice, and the antibody exhibits specific recognition of LDNF sequences, but not other fucosylated glycans tested. Immunocytochemical analysis demonstrates that LDNF antigens are localized on the tegumental surface of adult S. mansoni. Western blot analysis indicates that LDNF sequences are expressed on numerous high-molecular-weight glycoproteins from the three major human schistosome species, as well as the bird schistosome Trichobilharzia ocellata. The identification of LDNF antigen on the tegumental glycoproteins of schistosomes and the ability to synthesize LDNF conjugates should aid in the development of glycan-based vaccines and immunodiagnostic tests for schistosomiasis and in determining the role(s) of the glycans in worm development and pathogenesis.     

Studies of oligosaccharide specificity of perch roe fucolectin,using gold labeled neoglycoproteins

The specificity of perch (Perca fluviatilis) roe fucolectin was studied using the protein dot blot technique, followed by detection with colloidal gold-labeled neoglycoproteins bearing human milk polysaccharides. The strongest binding was noted with the H type 1 pentasaccharide lacto-N-fucopentaose (LNFP I, Fuc alpha 1-2 Gal beta 1-3 GlcNAc beta 1-3 Gal beta 1-4Glc); the interaction with the H type 6 trisaccharide 2'-fucosyllactose (2-FL, Fuc alpha 1-2 Gal beta 1-4 Glc) was weaker. Binding of the perch lectin to the Lewis antigens (associated with tumors and embryonic tissues) was also studied. It was found that the lectin weakly interacted with the hexasaccharide lacto-N-difucohexaose I, Fuc alpha 1-2 Gal beta 1-3[Fuc alpha 1-4]GlcNac beta 1-3 Gal beta 1-4 Glc), but not with Lea, Lec, Lex antigens. Thus, perch roe lectin exhibited pronounced differences in carbohydrate specificity from other fucolectins--a feature that may be used in structural studies and isolation of fucose-containing glycoconjugates.     

Primary structure of the glycans from mouse serum and milk transferrins.

A 'serotransferrin-like' protein was purified from mouse milk. This serotransferrin cross-reacts immunologically with the serotransferrin isolated from mouse plasma and not with the mouse lactotransferrin (lactoferrin). Sugar analysis of the three transferrins, i.e. serotransferrin, milk 'serotransferrin-like' protein and lactotransferrin, revealed that the major difference between the glycan primary structure of mouse serotransferrin and those of mouse milk 'serotransferrin-like' protein and lactotransferrin concerns essentially the presence of one fucose residue in the last two proteins. For structural determination, the N-glycosidically linked glycans were released from the protein by a reductive cleavage of the oligosaccharide-protein linkage under strong alkaline conditions. The primary structure of the released oligosaccharide alditols was determined by methylation analysis and 400 MHz 1H-n.m.r. spectroscopy. The oligosaccharide alditols released from milk 'serotransferrin-like' protein and lactotransferrin were identical and were identified as disialylated biantennary glycans of the N-acetyl-lactosamine type with a fucose residue alpha-1,6-linked to the N-acetylglucosamine residue conjugated to the peptide chain and having the following primary structure: NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-3)[NeuAc(alpha 2-6)Gal(beta 1-4)GlcNAc(beta 1-2)Man(alpha 1-6)]Man(beta 1-4)GlcNAc(beta 1-4)[Fuc(alpha 1-6)]GlcNAc(beta 1-N)Asn. The serotransferrin glycan has the same primary structure but is only partially fucosylated (10-15%).     

Isolation and characterization of four major neutral glycosphingolipids from the liver of the English sole (Parophrys vetulus). Presence of a novel branched lacto-ganglio-iso-globo hybrid structure

We have previously reported on carbohydrate structures of the major acidic glycosphingolipids from the liver of the English sole, Parophrys vetulus (Ostrander, G. K., Levery, S. B., Hakomori, S., and Holmes, E. H. (1988) J. Biol. Chem. 263, 3103-3110). We have now isolated four major neutral glycosphingolipids from English sole liver. They have been characterized by 1H nuclear magnetic resonance spectroscopy, methylation analysis, and by fast atom bombardment-mass spectrometry. In addition to neutral glycosphingolipids with known structures (CMH, lactosylceramide, and Gg3), a major polar neutral glycosphingolipid was isolated and characterized as having the following novel structure: (formula; see text) The compound represents a novel hybrid of neolacto-, ganglio-, and iso-globo-series glycosphingolipid structures, a combination not previously encountered. Furthermore, the linkage Fuc alpha 1----3GalNac has not been previously reported for a glycosphingolipid. The relationship of these structural elements to known glycoconjugates is discussed.     

H (0) blood group determinant is present on soluble human L-selectin expressed in BHK-cells.

In the present study we show that the H (0) blood group determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1-R is present on N-linked glycans of soluble human L-selectin recombinantly expressed in baby hamster kidney (BHK) cells. The glycans were isolated using complementary HPLC techniques and characterized by a combination of exoglycosidase digestion and mass spectrometry. The linkage of the fucose residues was determined by incubation of the glycans with specific fucosidases. The H blood determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1 was detected for bi-, 2,4 branched tri- and tetraantennary structures. To our knowledge, the proposed oligosaccharide structures represent a new glycosylation motif for recombinant glycoproteins expressed on BHK cells.     

Glycans of Schistosoma mansoni and keyhole limpet haemocyanin induce hepatic granulomas in vivo

Schistosoma mansoni eggs trapped in the liver of an infected host cause the major pathological manifestations of schistosomiasis. Miracidia within the deposited eggs secrete soluble egg antigens (SEA) that induce periovular granuloma formation, which may lead to severe hepatic fibrosis. Several reports have highlighted the immunomodulatory capacities of carbohydrate determinants present in the glycoproteins of SEA. These glycans contain among others the immunogenic Galbeta1-4(Fucalpha1-3)GlcNAc (LewisX) and GalNAcbeta1-4(Fucalpha1-2Fucalpha1-3)GlcNAc (LDN-DF) elements. Due to cross-reactivity with schistosomal glycan antigens, keyhole limpet haemocyanin (KLH) has been used extensively for diagnostic and therapeutic studies on schistosomiasis. In the present study, a granulomatous response with numerous eosinophils towards SEA- and KLH-coated beads implanted in the liver by mesenteric injection was observed. Immunophenotyping of these experimentally induced granulomas for cellular recruitment, chemokines, adhesion and extracellular matrix proteins revealed very close resemblance with hepatic lesions evoked by native schistosome eggs, hence demonstrating the usefulness of the bead model, in general, as well as of KLH as a model antigen to study the immunopathological mechanisms of schistosome infections. While trypsin digestion of KLH did not alter its antigenic characteristics, beads coated with SEA or KLH treated with sodium periodate to destroy the immunological properties of their carbohydrate chains, yielded only a monolayer of macrophages similar to negative control beads. Up-regulation of ICAM-1, LFA-1 and fibronectin in SEA-induced granulomas and in native and trypsinised KLH-induced granulomas indicates a major role of the carbohydrate elements of SEA and KLH in the initiation and homeostasis of the inflammatory response. These data provide new insights in the complex and multifactorial carbohydrate-dependent host-parasite immunological interactions.     

Structural characterization of Schistosoma mansoni adult worm glycosphingolipids reveals pronounced differences with those of cercariae

Immune responses induced by glycans upon infection with Schistosoma mansoni may be mediated by either schistosomal glycoproteins or glycosphingolipids. In this study, we have elucidated the structural features of both carbohydrate moieties and respective ceramide units of complex glycosphingolipids from adult S. mansoni. Obtained data revealed a vast structural heterogeneity due to manifold combinations of different oligosaccharides and ceramide entities. Observed carbohydrate moieties included Lewis(X) (Le(X); Gal(β1-4)[Fuc(α1-3)]GlcNAc) as well as, in part, multiply fucosylated LacdiNAc (LDN; GalNAc(β1-4)GlcNAc) carbohydrate epitopes. Corresponding lipid portions comprised predominantly C18-sphingosine as well as C18- and C20-phytosphingosine derivatives. Intriguingly, glycosphingolipids carrying an Le(X) epitope contained predominantly C18-sphingosine, whereas LDN-based species exhibited mostly phytosphingosine derivatives, in addition to C18-sphingosine, indicating that the two classes of glycosphingolipids might be synthesized via different biosynthetic routes. Compared with literature data, adult worm glycosphingolipids with Le(X) epitopes revealed clear structural differences in comparison to corresponding cercarial species which have been shown to exhibit mainly sphinganine bases with 18-21 carbon atoms. Therefore, it may be hypothesized that the divergent structural features of the respective ceramide moieties are responsible for the published observation that only adult worm, but not cercarial glycosphingolipids are able to induce dendritic cell activation skewing the T-cell response toward a Th1 profile.     

Carbohydrate structures of nonspecific cross-reacting antigen-2, a glycoprotein purified from meconium as an antigen cross-reacting with anticarcinoembryonic antigen antibody. Occurrence of complex-type sugar chains with the Gal beta 1----3GlcNAc beta 1----3Gal beta 1----4GlcNAc beta 1----outer chains

Nonspecific cross-reacting antigen-2 (NCA-2) is a glycoprotein purified from meconium as a closely correlated entity with carcinoembryonic antigen (CEA). As in the case of CEA, only asparagine-linked sugar chains are included in NCA-2. In order to elucidate the structural characteristics of the sugar chains of NCA-2, they were quantitatively released from the polypeptide backbone by hydrazinolysis and reduced with NaB3H4 after N-acetylation. The radioactive oligosaccharides were fractionated by paper electrophoresis, serial chromatography on immobilized lectin columns, and Bio-Gel P-4 (under 400 mesh) column chromatography. Structures of the oligosaccharides were estimated from the data of the binding specificities of immobilized lectin columns and the effective size of each oligosaccharide determined by passing through a Bio-Gel P-4 column and were then confirmed by endo-beta-galactosidase digestion, sequential digestion with exoglycosidases with different aglycon specificities, and methylation analysis. NCA-2 contains a similar number (27 mol) of sugar chains in one molecule compared with CEA (24-26 mol). However, all sugar chains of NCA-2 were complex-type in contrast to CEA, approximately 8% of the sugar chains of which were high mannose-type (Yamashita, K., Totani, K., Kuroki, M., Matsuoka, Y., Ueda, I., and Kobata, A. (1987) Cancer Res. 47, 3451-3459). About 80% of the oligosaccharides from NCA-2 contain bisecting N-acetylglucosamine residues, and the percent molar ratio of mono-, bi, tri, and tetraantennary oligosaccharides was 2:14:57:27. (+/- Fuc alpha 1----2)Gal beta 1----4(+/- Fuc alpha 1----3)GlcNAc, (+/- Fuc alpha 1----2)Gal beta 1----3(+/- Fuc alpha 1----4)GlcNAc, (+/- Fuc alpha 1----2)Gal beta 1----4(+/- Fuc alpha 1----3)GlcNAc beta 1---- 3Gal beta 1----4GlcNAc, (+/- Fuc alpha 1----2)Gal beta 1----3(+/- Fuc alpha 1----4)GlcNAc beta 1---- 3Gal beta 1----4GlcNAc, and GalNAc beta 1----3Gal beta 1----3GlcNAc beta 1----3Gal beta 1----4GlcNAc were found as their outer chain moieties. Approximately 60% of the oligosaccharides from NCA-2 contain the Gal beta 1----4 or 3GlcNAc beta 1----3Gal beta 1----4GlcNAc beta 1----group in their outer chains.     

Analysis of folate binding protein N-linked glycans by mass spectrometry

The folate binding protein (FBP), also known as the folate receptor (FR), is a glycoprotein which binds the vitamin folic acid and its analogues. FBP contains multiple N-glycosilation sites, is selectively expressed in tissues and body fluids, and mediates targeted therapies in cancer and inflammatory diseases. Much remains to be understood about the structure, composition, and the tissue specificities of N-glycans bound to FBP. Here, we performed structural characterization of N-linked glycans originating from bovine and human milk FBPs. The N-linked glycans were enzymatically released from FBPs, purified, and permethylated. Native and permethylated glycans were further analyzed by matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry (MS), while tandem MS (MS/MS) was used for their structural characterization. The assignment of putative glycan structures from MS and MS/MS data was achieved using Functional Glycomics glycan database and SimGlycan software, respectively. It was found that FBP from human milk contains putative structures that have composition consistent with high-mannose (Hex(5-6)HexNAc(2)) as well as hybrid and complex N-linked glycans (NeuAc(0-1)Fuc(0-3)Hex(3-6)HexNAc(3-5)). The FBP from bovine milk contains putative structures corresponding to high-mannose (Hex(4-9)HexNAc(2)) as well as hybrid and complex N-linked glycans (Hex(3-6)HexNAc(3-6)), but these glycans mostly do not contain fucose and sialic acid. Glycomic characterization of FBP provides valuable insight into the structure of this pharmacologically important glycoprotein and may have utility in tissue-selective drug targeting and as a biomarker.     

Molecular cloning and characterization of an alpha1,3 fucosyltransferase, CEFT-1, from Caenorhabditis elegans

We report on the identification, molecular cloning, and characterization of an alpha1,3 fucosyltransferase (alpha1,3FT) expressed by the nematode, Caenorhabditis elegans . Although C. elegans glycoconjugates do not express the Lewis x antigen Galbeta1-- >4[Fucalpha1-->3]GlcNAcbeta-->R, detergent extracts of adult C.elegans contain an alpha1,3FT that can fucosylate both nonsialylated and sialylated acceptor glycans to generate the Lexand sialyl Lexantigens, as well as the lacdiNAc-containing acceptor GalNAcbeta1-->4GlcNAcbeta1-- >R to generate GalNAcbeta1-->4 [Fucalpha1-->3]GlcNAcbeta1-->R. A search of the C.elegans genome database revealed the existence of a gene with 20-23% overall identity to all five cloned human alpha1,3FTs. The putative cDNA for the C.elegans alpha1,3FT (CEFT-1) was amplified by PCR from a cDNA lambdaZAP library, cloned, and sequenced. COS7 cells transiently transfected with cDNA encoding CEFT-1 express the Lex, but not sLexantigen. The CEFT-1 in the transfected cell extracts can synthesize Lex, but not sialyl Lex, using exogenous acceptors. A second fucosyltransferase activity was detected in extracts of C. elegans that transfers Fuc in alpha1,2 linkage to Gal specifically on type-1 chains. The discovery of alpha-fucosyltransferases in C. elegans opens the possibility of using this well-characterized nematode as a model system for studying the role of fucosylated glycans in the development and survival of C.elegans and possibly other helminths.      

Repeats of LacdiNAc and fucosylated LacdiNAc on N-glycans of the human parasite Schistosoma mansoni

N-Glycans from glycoproteins of the worm stage of the human parasite Schistosoma mansoni were enzymatically released, fluorescently labelled and analysed using various mass spectrometric and chromatographic methods. A family of 28 mainly core-alpha1-6-fucosylated, diantennary N-glycans of composition Hex(3-4)HexNAc(6-12)Fuc(1-6) was found to carry dimers of N,N'-diacetyllactosediamine [LacdiNAc or LDN; GalNAc(beta1-4)GlcNAc(beta1-] with or without fucose alpha1-3-linked to the N-acetylglucosamine residues in the antennae {GalNAc(beta1-4)[+/-Fuc(alpha1-3)]GlcNAc(beta1-3)GalNAc(beta1-4)[+/-Fuc(alpha1-3)]GlcNAc(beta1-}. To date, oligomeric LDN and oligomeric fucosylated LDN (LDNF) have been found only on N-glycans from mammalian cells engineered to express Caenorhabditis elegansbeta4-GalNAc transferase and human alpha3-fucosyltransferase IX [Z. S. Kawar et al. (2005) J Biol Chem280, 12810-12819]. It now appears that LDN(F) repeats can also occur in a natural system such as the schistosome parasite. Like monomeric LDN and LDNF, the dimeric LDN(F) moieties found here are expected to be targets of humoral and cellular immune responses during schistosome infection.     

Differential expression of LacdiNAc,fucosylated LacdiNAc,and Lewis x glycan antigens in intramolluscan stages of Schistosoma mansoni

We report the expression of 3 well-characterized adult Schistosoma mansoni glycan antigens among molluscan stages of the parasite. These antigens are LacdiNAc (LDN; GalNAcbeta1-4GlcNAc-R), fucosylated LacdiNAc (LDNF; GalNAc[Fucal-3]beta1-4GlcNAc-R), and Lewis x (Le(x); Gal[Fucalpha1-3]beta1-4GlcNAc-R). The presence of the glycans was determined by both immunoblot and immunohistological methods using monoclonal antibodies that specifically recognize each glycan epitope. Immunoblot analyses reveal that LDN and LDNF epitopes are expressed on many different glycoproteins, including eggs, mother sporocysts, daughter sporocysts, and cercariae, although LDN expression among daughter sporocysts is greatly reduced. LDN and LDNF epitopes are localized on the tegument and in the intrasporocyst cell masses of both in vitro-derived and in vivo-derived mother sporocysts and in the daughter sporocysts derived on day 16 after infection. Unexpectedly, high levels of LDN and LDNF glycans were detected in the infected, but not in the uninfected, snail hemolymph, suggesting that the infecting larvae secrete LDN and LDNF glycoconjugates into the snail hosts. In contrast, the expression of Le(x) antigen among the molluscan stages is highly restricted. Le(x) is present on a few high-molecular weight glycoproteins in eggs and cercariae but is undetectable in mother and daughter sporocysts. Taken together with our earlier studies on vertebrate stages of S. mansoni, these results show that LDN and LDNF glycans are conserved during schistosome development. The study further extends the evidence that Le(x) is a developmentally regulated antigen in schistosomes.     

Selective expression of different fucosylated epitopes on two distinct sets of Schistosoma mansoni cercarial O-glycans: identification of a novel core type and Lewis X structure.

The glycobiology of Schistosoma mansoni is dominated by developmentally regulated expression of various fucosylated structures, most notably the Lewis X epitope and a multifucosylated sequence, Fuc alpha1-->2Fuc alpha1-->, in its various forms. For the infective cercarial stage, Lewis X has been structurally identified on glycosphingolipids and N-glycans of total glycoprotein extracts, and a population of multifucosylated glycoproteins were found to carry a unique terminal sequence, +/-Fuc alpha1-->2Fuc alpha1-->[3GalNAc beta1-->4(Fuc alpha1-->2Fuc alpha1--> 2Fuc alpha1-->3) GlcNAc beta1-->3Gal alpha1-->](n), on their O-glycans. Using a mass spectrometry approach coupled with chromatographic separation, sequential exoglycosidase digestion, periodate oxidation, and other chemical derivatization, we demonstrate that Lewis X could also be carried on the cercarial O-glycans, but the two distinctive sets of fucosylated epitopes were conjugated to two different core structures. Lewis X, lacNAc, or single GlcNAc was found to attach directly to the -->3Gal beta1-->3GalNAc core and indirectly via another beta-Gal residue branching off from C6 of the reducing end GalNAc to give a biantennary-like structure. The -->3(+/-Gal beta1-->6)Gal beta1-->3(-->3Gal beta1-->6)GalNAc core thus characterized represents a novel core type for O-glycans. In contrast, the previously characterized multifucosylated terminal sequences were carried on conventional type 1 and 2 cores. The smallest structures of the reductively released O-glycans were defined as GalNAc beta1-->4GlcNAc beta1-->3Gal beta1-->3GalNAcitol with a total of two to four fucoses attached to the terminal lacdiNAc. alpha-Galactosylation of the nonreducing terminal beta-GalNAc instead of fucose capping leads to further elongation with another lacdiNAc unit that could also extend directly from C6 of the reducing end GalNAc and similarly elongated or terminated.