Characterization of a series of novel fucose-containing glycosphingolipid immunogens from eggs of Schistosoma mansoni

Glycosphingolipids in human parasites

Glycosphingolipids (GSLs) are comprised of glycans (oligosaccharides) linked to a lipid containing a sphingosine moiety. They are major membrane components in cells of most animals, and importantly, they also occur in parasitic protozoans and worms that infect people. While the endogenous functions of the GSLs in most parasites are elusive, many of these GSLs are recognized by antibodies in infected human and animal hosts, and thus, their structures, biosynthesis, and functions are of great interest. Such knowledge of GSLs could lead to new drugs and diagnostics for treating infections, as well as novel vaccine strategies. The diversity of GSLs recently identified in such infectious organisms and aspects of their immune recognition are major topics of this review. It is not intended to be exhaustive but to highlight aspects of GSL glycans in human parasites.

Reduction of Allergic Lung Disease by Mucosal Application of Toxoplasma gondii-Derived Molecules: Possible Role of Carbohydrates

Background

The hygiene hypothesis suggests a link between parasitic infections and immune disorders, such as allergic diseases. We previously showed that infection with Toxoplasma gondii or systemic application of T. gondii tachyzoites lysate antigen (TLA) in a prophylactic, but not therapeutic protocol, prevented allergic airway inflammation in mice. Here we tested the effect of prophylactic and therapeutic application of TLA via the mucosal route.

Methods

Mice were intranasally treated with TLA either i) prior to sensitization, ii) during sensitization and challenge, or iii) after sensitization with ovalbumin (OVA). Recruitment of inflammatory cells to the lung, cytokine levels in restimulated lung and spleen cell cultures as well as levels of OVA-specific antibodies in serum were measured. In parallel, the effect of native TLA, heat-inactivated (hiTLA) or deglycosylated TLA (dgTLA) on sensitized splenocytes was evaluated ex vivo.

Results

When applied together with OVA i) during systemic sensitization and local challenge or ii) exclusively during local challenge, TLA reduced infiltration of eosinophils into the lung, OVA-specific type 2 cytokines in restimulated lung cell cultures, and partially, type 2 cytokines in restimulated spleen cell cultures in comparison to allergic controls. No beneficial effect was observed when TLA was applied prior to the start of sensitization. Analysis of epitope sugars on TLA indicated a high abundance of mannose, fucose, N-acetylglucosamine, and N-acetylgalactosamine. Deglycosylation of TLA, but not heat-inactivation, abolished the potential of TLA to reduce type 2 responses ex vivo, suggesting a significant role of carbohydrates in immunomodulation.

Conclusion

We showed that mucosal application of TLA reduced the development of experimental allergy in mice. The beneficial effects depended on the timing of the application in relation to the time point of sensitization. Not only co-application, but also therapy in sensitized/allergic animals with native TLA reduced local allergic responses. Furthermore, we show that TLA is highly glycosylated and glycoconjugates seem to play a role in anti-allergic effects. In summary, given the powerful modulatory effect that TLA exhibits, understanding its exact mechanisms of action may lead to the development of novel immunomodulators in clinical application.

The role of Ser-(Arg-Ser-Arg-Ser-GlucNAc)19-GlucNAc Fasciola gigantica glycoprotein in the diagnosis of prepatent fasciolosis in rabbits

In the present study, the carbohydrate structures associated with Fasciola gigantica adult worm were identified by indirect hemagglutination inhibition test. Glucose was found to be the main monosaccharide associated with the fluke. According to indirect hemagglutination inhibition results, purification of glycoprotein fractions from worm crude extract was carried out by affinity chromatography immobilized glucose agarose gel and Con-A lectin columns. The isolated glycoprotein fractions, FI and FII, were characterized by SDS-PAGE which revealed one band in FI of 26 kDa and another one band of 19.5 kDa in FII compared with 12 bands associated with whole worm extract. Both fractions were also characterized by isoelectric focusing technique which proved that both bands were acidic in nature with pIs 6.4 and 6.5 respectively. The comparative diagnostic evaluation of the two isolated glycoprotein fractions and crude extract of experimental fasciolosis in rabbits by ELISA revealed that FII was more potent in the diagnosis during prepatent (first week post infection) and patent periods (10 weeks post infection) than FI and crude extract. Moreover, infected rabbit sera at ten weeks post infection identified both bands; 26 and 19.5 kDa in western blot analysis confirming its immunodiagnostic activities which was proved previously by ELISA. FII proved potency in diagnosis of fasciolosis in 200 buffalo serum samples of different ages and sexes using ELISA which recorded 95 % positive and 5 % negative samples. Moreover, the detailed structural analyses of the most potent fraction, F11, using mass spectrum was made and elucidated chemical structure; O-glycan [Ser-(Arg-Ser-Arg-Ser-GlucNAc)19-GlucNAc]. The present result introduces GlucNAc rich fraction of F .gigantica that can be used successfully in the diagnosis of acute and chronic fasciolosis.

Biochemical studies on sphingolipids of Artemia franciscana: complex neutral glycosphingolipids

Brine shrimp are primitive crustacean arthropodal model organisms, second to daphnia, which can survive in high-salinity environments. Their oviposited cysts, cuticle-covered diapausing eggs, are highly resistant to dryness. To elucidate specialties of brine shrimp, this study characterized glycosphingolipids, which are signal transduction-associated material. A group of novel and complex fucosyl glycosphingolipids were separated and identified from cysts of the brine shrimp Artemia franciscana by repeated lipid extraction, alkaline methanolysis, acid treatment, successive column chromatography, and post-source decay measurements by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Structures of the glycosphingolipids were elucidated by conventional structural characterization and mass spectrometry, and the compounds were identified as GlcNAcβ1-3GalNAcβ1-4(GlcNAcα1-2Fucα1-3)GlcNAcβ1-3Manβ1-4Glcβ1-Cer, GalNAcβ1-4(Fucα1-3)GlcNAcβ1-3GalNAcβ1-4(GlcNAcα1-2Fucα1-3)GlcNAcβ1-3Manβ1-4Glcβ1-Cer, and GalNAcβ1-4(GlcNAcα1-2Fucα1-3)GlcNAcβ1-3GalNAcβ1-4(GlcNAcα1-2Fucα1-3)GlcNAcβ1-3Manβ1-4Glcβ1-Cer. These compounds also contained a branching, non-arthro-series disaccharide with an α-GlcNAc terminus, similar to that found in a previously reported ceramide hexasaccharide (III³(GlcNAcα2Fucα)-At₄Cer). The glycans within these complex GSLs are longer than reported glycans of the animal kingdom containing α-GlcNAc terminus. These complex GSLs as well as the longest GSL with ten sugar residues, ceramide decasaccharide (CDeS), contain the fucosylated LacdiNAc sequence reported to associate with parasitism/immunosuppression and the α-GlcNAc terminus reported to show a certain antibacterial effect in other reports. CDeS, the longest GSL of this species, was found in the highest amount, which indicates that CDeS may be functionally important.

Immune modulation by Lacto-N-fucopentaose III in experimental autoimmune encephalomyelitis

Parasitic infections frequently lead to immune deviation or suppression. However, the application of specific parasitic molecules in regulating autoimmune responses remains to be explored. Here we report on the immune modulatory function of Lacto-N-fucopentaose III (LNFPIII), a schistosome glycan, in an animal model for multiple sclerosis. We found that LNFPIII treatment significantly reduced the severity of experimental autoimmune encephalomyelitis (EAE) and CNS inflammation, and skewed peripheral immune response to a Th2 dominant profile. Inflammatory monocytes (IMCs) purified from LNFPIII-treated mice had increased expression of nitric oxide synthase 2, and mediated T cell suppression. LNFPIII treatment also significantly increased mRNA expression of arginase-1, aldehyde dehydrogenase 1 subfamily A2, indoleamine 2,3-dioxygenase and heme oxygenase 1 in splenic IMCs. Furthermore, LNFPIII treatment significantly reduced trafficking of dendritic cells across brain endothelium in vitro. In summary, our study demonstrates that LNFPIII glycan treatment suppresses EAE by modulating both innate and T cell immune response.

Glycosphingolipid structural analysis and glycosphingolipidomics

Sphingosines, or sphingoids, are a family of naturally occurring long-chain hydrocarbon derivatives sharing a common 1,3-dihydroxy-2-amino-backbone motif. The majority of sphingolipids, as their derivatives are collectively known, can be found in cell membranes in the form of amphiphilic conjugates, each composed of a polar head group attached to an N-acylated sphingoid, or ceramide. Glycosphingolipids (GSLs), which are the glycosides of either ceramide or myo-inositol-(1-O)-phosphoryl-(O-1)-ceramide, are a structurally and functionally diverse sphingolipid subclass; GSLs are ubiquitously distributed among all eukaryotic species and are found in some bacteria. Since GSLs are secondary metabolites, direct and comprehensive analysis (metabolomics) must be considered an essential complement to genomic and proteomic approaches for establishing the structural repertoire within an organism and deducing its possible functional roles. The glycosphingolipidome clearly comprises an important and extensive subset of both the glycome and the lipidome, but the complexities of GSL structure, biosynthesis, and function form the outlines of a considerable analytical problem, especially since their structural diversity confers by extension an enormous variability with respect to physicochemical properties. This chapter covers selected developments and applications of techniques in mass spectrometric (MS) that have contributed to GSL structural analysis and glycosphingolipidomics since 1990. Sections are included on basic characteristics of ionization and fragmentation of permethylated GSLs and of lithium-adducted nonderivatized GSLs under positive-ion electrospray ionization mass spectrometry (ESI-MS) and collision-induced mass spectrometry (CID-MS) conditions; on the analysis of sulfatides, mainly using negative-ion techniques; and on selected applications of ESI-MS and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to emerging GSL structural, functional, and analytical issues. The latter section includes a particular focus on evolving techniques for analysis of gangliosides, GSLs containing sialic acid, as well as on characterizations of GSLs from selected nonmammalian eukaryotes, such as dipterans, nematodes, cestodes, and fungi. Additional sections focus on the issue of whether it is better to leave GSLs intact or remove the ceramide; on development and uses of thin-layer chromatography (TLC) blotting and TLC-MS techniques; and on emerging issues of high-throughput analysis, including the use of flow injection, liquid chromatography mass spectrometry (LC-MS), and capillary electrophoresis mass spectrometry (CE-MS).

Immune biasing by helminth glycans

The ability of helminth parasites to drive polarized Th2 responses has been known for some time. Interestingly, many recent studies have shown that helminth-expressed glycan activation of host immune cells accounts for much of the anti-inflammatory and Th2-biasing observed. This microreview attempts to cover the biology of expression of immunomodulatory glycans in various helminth parasites, the immune cells they interact with including the production of cytokines, chemokines and antibodies. We also discuss the potential cell surface receptors which are capable of binding certain glycans and the known mech-anisms which ultimately lead to production of anti-inflammatory mediators as well as polarizing CD4+ T-cell responses to Th2-type in the host. Lastly, we discuss a novel mechanism for activation of antigen-presenting cells by a specific helminth glycan that leads to maturation of Type 2 dendritic cells.

Chemical structures and immunolocalization of glycosphingolipids isolated from Diphyllobothrium hottai adult worms and plerocercoids

Glycosphingolipids (GSLs) were purified from adults and plerocercoids of the tapeworm Diphyllobothrium hottai, and their chemical structures were determined. Total lipid fractions prepared from chloroform/methanol extracts of whole tissues were fractionated successively on ion-exchange chromatography, silicic acid column chromatography, and preparative TLC. The purified GSLs were characterized by methylation analysis, TLC-immunostaining, liquid secondary ion MS, MALDI-TOF MS, and 1H-NMR. Ten GSLs were isolated from adult worms and four from plerocercoids, comprising mono-, di-, tri-, tetra-, and pentasaccharides. The GSL Gal beta 1-4(Fuc alpha 1-3)Glc beta 1-3Gal beta 1-Cer was found in adult worms but not in plerocercoids, whereas Ga lbeta 1-4 (Fuc alpha 1-3)Glc beta 1-3(Gal beta 1-6)Gal beta 1-Cer was found in both adult worms and plerocercoids. We previously found a similar series of GSLs in plerocercoids of the cestode Spirometra erinaceieuropaei, and termed them 'spirometosides'[Kawakami, Y. et al. (1996) Eur J. Biochem. 239, 905-911]. The core structure of spirometosides, Gal beta 1-4Glc beta 1-3 Gal beta 1-Cer, may have taxonomic significance, being characteristic of pseudophyllidean tapeworms. In the present study, GSL compositions were significantly different between adults and plerocercoids, and growth-dependent changes in composition were documented. We found a novel dihexosylceramide, Glc beta 1-3Gal beta 1-Cer, which is a possible precursor for spirometosides. Immunohistochemical examination showed that spirometoside GSLs are highly enriched in the inner surface of bothria, the major point of contact between the adult worm and the host's intestine. Our findings indicate that spirometosides are involved in host-parasite interaction.

Immunomodulation by parasites: high mobility group 2 (HMG-2) protein is a putative intracellular mediator for fucosylated sugars of Schistosoma mansoni

Fucosylated sugars in Schistosoma mansoni possess immunomodulatory properties. In order to gain insights to the mechanisms involved, attempts were made to identify host immune cell molecules that specifically recognize these sugars. On Western blots, specific binding of synthetic biotinylated fucose sugars to proteins of approximately 25-27kDa was observed. Three proteins were isolated by affinity chromatography and subjected to protein sequencing. The determined N-terminal sequences and that of tryptic peptides of two proteins did not show homology to known sequences in the NCBI database. The third was identified as a member of the high mobility group 2 (HMG-2) proteins. In vitro stimulation of mouse spleen cells with Lewis(x) sugars up-regulated the expression of HMG-2 mRNA. These data suggest that HMG-2 protein may function as a putative intracellular receptor/mediator for fucosylated sugars of parasites.

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.

Fucosyltransferases in Schistosoma mansoni development

Glycoconjugate-bound fucose, abundant in the parasite Schistosoma mansoni, has been found in the form of Fucalpha1,3GlcNAc, Fucalpha1,2Fuc, Fucalpha1,6GlcNAc, and perhaps Fucalpha1,4GlcNAc linkages. Here we quantify fucosyltransferase activities in three developmental stages of S. mansoni. Assays were performed using fluorophore-assisted carbohydrate electrophoresis with detection of radioactive fucose incorporation from GDP-[(14)C]-fucose into structurally defined acceptors. The total fucosyltransferase-specific activity in egg extracts was 50-fold higher than that in the other life stages tested (cercaria and adult worms). A fucosyltransferase was detected that transferred fucose to type-2 oligosaccharides (Galbeta1,4GlcNAc-R), both sialylated (with the sialic acid attached to the terminal Gal by alpha2,3 or 2,6 linkage) and nonsialylated. Another fucosyltransferase was identified that transferred fucose to lactose-based and type-2 fucosylated oligosaccharides, such as LNFIII (Galbeta1,4(Fucalpha1,3)GlcNAcbeta1,3Galbeta1,4Glc). A low level of fucosyltransferase that transfers fucose to no-sialylated type-1 oligosaccharides (Galbeta1,3GlcNAc-R) was also detected. These studies revealed multifucosylated products of the reactions. In addition, the effects of fucose-type iminosugars inhibitors were tested on schistosome fucosyltransferases. A new fucose-type 1-N-iminosugar was four- to sixfold more potent as an inhibitor of schistosome fucosyltransferases in vitro than was deoxyfuconojirimycin. In vivo, this novel 1-iminosugar blocked the expression of a fucosylated epitope (mAb 128C3/3 antigen) that is associated with the pathogenesis of schistosomiasis.

Characteristic structural features of schistosome cercarial N-glycans: expression of Lewis X and core xylosylation

Schistosomal egg N-glycans are the only examples in nature that have been structurally shown to contain beta2-xylosylation, alpha6-fucosylation, and alpha3-fucosylation on the N,N'-diacetyl chitobiose core. We present evidence that core difucosylated and xylosylated N-glycans are characteristics of Schistosoma japonicum eggs but not of the cercariae and adults, for which neither core xylosylation nor alpha3-fucosylation could be readily detected. In contrast, a majority of the N-glycans from Schistosoma mansoni cercariae but not the adults are core xylosylated. Tandem mass spectrometry analysis coupled with chromatographic mapping, sequential exoglycosidase digestion, and methylation analysis were employed to unambiguously define the structures of core beta2-xylosylated, alpha6-fucosylated N-glycans from S. mansoni cercariae. Unexpectedly, a majority of these N-glycans were found to carry Lewis X determinant, Galbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-->, on the nonreducing termini of mono- and biantennary structures. The Lewis X-containing glycoproteins were found to be distinct from those carrying the complex, multifucosylated glycocalyx O-glycans reported previously. The corresponding N-glycans from S. japonicum cercariae are likewise dominated by Lewis X termini but without the core xylosylation. We concluded that the invading cercariae present an important and abundant source of Lewis X antigens, which may contribute to the induced humoral response upon infection. Following transformation and development into the adults, the N-glycans synthesized comprise a significantly larger amount of high mannose and fucosylated pauci-mannose structures in comparison with the cercarial N-glycans. A portion of the mono- and biantennary complex types were identified to carry Lewis X and fucosylated LacdiNAc termini, which could also be detected by mass spectrometry analysis on larger, complex-type structures.

The liver flukes Fasciola gigantica and Fasciola hepatica express the leucocyte cluster of differentiation marker CD77 (globotriaosylceramide) in their tegument

Glycosphingolipids from the parasitic liver flukes Fasciola gigantica and Fasciola hepatica were isolated and their carbohydrate moieties were structurally analysed by methylation analysis, exoglycosidase treatment, on-target exoglycosidase cleavage and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. For both liver fluke species, the ceramide monohexosides Gal1-ceramide and Glc1-ceramide were found in relative amounts of 1.0 to 0.1, respectively. From F. gigantica, the ceramide dihexoside was isolated in sufficient amounts to be structurally determined as lactosylceramide, Gal beta4-Glc1-ceramide, while for both liver fluke species the ceramide trihexoside was shown to be Gal alpha4Gal beta4-Glc1-ceramide, which is designated as either globotriaosylceramide, Pk-blood group antigen or CD77 leucocyte cluster of differentiation antigen. To our knowledge, this is the first report on the expression of globo-series glycosphingolipids in non-mammalian species. Ceramide analysis of ceramide monohexosides yielded as major components octadecanoic and 2-hydroxyoctadecanoic fatty acids together with C18- and C20-phytosphingosines. By the use of an anti-CD77 monoclonal antibody and the Escherichia coli Shiga toxin B1 subunit, globotriaosylceramide could be immunolocalised to the tegument of F. hepatica cryosections. The sharing of CD77 between liver flukes and their mammalian hosts fits in with the concept of molecular mimicry, which is closely parallel to the established imitation of host CD15 (Lewis X) displayed by the blood fluke Schistosoma mansoni.

Glycoconjugates from Parasitic Helminths: Structure Diversity and Immunobiological Implications

We have provided an account of the progress we and others have made over the last decade on the structural characterization of glycans from parasitic helminths. We hope to have illustrated a few principles and patterns governing helminth glycosylation, as well as the experimental approaches adopted and their associated strengths and limitations. Schistosomes remain the best studied systems but are still punctuated with gaps of knowledge. An important theme developed here is the regulated developmental stage-specific expression of various glycan epitopes and their interplay with immediate host environments for successful parasitism. It is anticipated that more novel or unusual structures will continuously be uncovered in the future and that despite many difficulties, current analytical techniques should be well up to meet the challenge in at least elucidating the major or key glycoconjugates from each of the diverse range of worms. The bottle neck will in fact reside in finding suitable experimental models to test their putative immunobiological functions from which the intricate host-parasite interactions can be delineated and rational vaccine design be achieved. The glycobiology of parasitic helminths is an area waiting to be more fully explored and the rewards should be sweet.

Stage-associated expression of ceramide structures in glycosphingolipids from the human trematode parasite Schistosoma mansoni

Glycosphingolipids of Schistosoma mansoni adults, cercariae and eggs comprise ceramide monohexosides (CMH) with glucose or galactose and ceramide dihexosides (CDH) with the schistosome-specific structure GalNAc(beta1-4)Glc(1-1)ceramide. Ceramide analysis revealed C18- and C20-phytosphingosines in egg CMH, C18-sphinganine as well as C18-, C19- and C20-phytosphingosines in cercarial CMH, and C18- and C20-phytosphingosines as well as C18-sphingosine and C18-sphinganine in adult CMH. For all three life cycle stages, the predominant fatty acid was C16h:0. As a characteristic feature, a range of saturated, unsaturated and hydroxylated long-chain fatty acids with 24-28 carbon atoms were additionally found in minor cercarial CMH species. The corresponding ceramides represented major constituents in cercarial CDH, while adult and egg CDH were dominated by ceramides with short fatty acid chains. The resultant ceramide patterns could be correlated with the differential expression of carbohydrate antigens on schistosomal glycolipids at various stages. A possible impact of ceramide structure on the biosynthesis of the carbohydrate moieties is discussed.

Various stages of schistosoma express Lewis(x), LacdiNAc, GalNAcbeta1-4 (Fucalpha1-3)GlcNAc and GalNAcbeta1-4(Fucalpha1-2Fucalpha1-3)GlcNAc carbohydrate epitopes: detection with monoclonal antibodies that are characterized by enzymatically synthesized neoglycoproteins

We report here that fucosylated epitopes such as Lewis(x), LacdiNAc, fucosylated LacdiNAc (LDN-F) and GalNAcbeta1-4(Fucalpha1-2Fucalpha1-3)GlcNAc (LDN-DF) are expressed by schistosomes throughout their life cycle. These four epitopes were enzymatically synthesized and coupled to bovine serum albumin to yield neoglycoproteins. Subsequently these neoglycoproteins were used to probe a panel of 188 monoclonal antibodies obtained from infected or immunized mice, in ELISA and surface plasmon resonance analysis. Of these antibodies, 25 recognized one of the fucosylated structures synthesized, indicating that these structures are immunogenic during infection. The MAbs identified could be subdivided in four different groups based on the recognition of either the Lewis(x)-, the LacdiNAc-, the LDN-DF-, or both the LDN-F- and LDN-DF epitope. These monoclonal antibodies were then used to investigate the localization of the fucosylated epitopes in various stages of Schistosoma mansoni using indirect immunofluorescence. Lewis(x)epitopes were mainly found in the gut and on the tegument of adult worms, on egg shells, and on the oral sucker of cercariae. The LacdiNAc epitope was expressed on the tegument of adult worms, on miracidia, and on the oral sucker of cercariae. In contrast, LDN-DF epitopes were mainly present in the excretory system of adult worms, on miracidia and on whole cercariae. These also stained positive with the LDN-F/LDN-DF epitope antibodies, while whole parenchyma reacted characteristically only with the latter antibodies. The identification of different carbohydrate structures in various stages of schistosomes may lead to a better understanding of the function of glycans in the immune response during infection.

Identification and localization of a schistosome-associated fucosyllactose determinant expressed by Fasciola hepatica

A Biomphalaria alexandrina-derived lectin (BaSII), of proven specificity to a Schistosoma mansoni-associated fucosyllactose [(Fuc alpha1-2) Gal beta1-4 Glc] determinant, was employed to investigate the putative antigenic cross-reactivity between Schistosoma mansoni and Fasciola hepatica in terms of this structurally-defined oligosaccharide sequence. BaSII affinity column chromatography of extracts of adult worms metabolically radiolabelled with 35S-methionine and analysis by two-dimensional gels established the expression of the fucosyllactose determinant in multiple copies among heterogeneous, acidic glycoproteins synthesized by adult Fasciola hepatica. Direct fluorescence microscopy revealed that determinant-bearing glycoproteins were localized to the external glycocalyx and perikarya of the tegument as well as the epithelial lining of the intestinal caeca and vitelline ducts and glands. Determinant expression was also evident in embryonated cells of eggs and miracidia as well as the intermediate cellular wall of encysted metacercariae, suggesting its conservation during the course of development of the parasite. Based on the structural relatedness of the cross-reactive fucosyllactose determinant to the antigenic mammalian blood group H trisaccharide, our observations may have implications in serodiagnosis and immunoprophylaxis of schistosomiasis/fascioliasis.

Immunochemical characterisation of Schistosoma mansoni glycolipid antigens

The aim of this study was to investigate the occurrence, distribution and immunochemical properties of antibody-defined carbohydrate epitopes in neutral glycolipid fractions of Schistosoma mansoni eggs, cercariae and adults. The amount of extractable, antigenic, neutral glycolipids was lowest in adult worms, increasing consecutively in cercariae and eggs. The immunoreactivity of the glycolipids resided in the carbohydrate moiety in that it was periodate-sensitive. Serological reactivity, and monosaccharide component analysis, anomeric configuration and methylation-linkage analyses indicated that there were two dominant epitopes, which could be partially defined immunologically. The first epitope was detected on egg, cercarial and adult glycolipids. It was strongly recognised by mouse chronic infection sera and rabbit hyperimmune sera raised against specific egg antigens, and was defined by the monoclonal antibody M2D3H (Bickle QD, Andrews BJ. Characterisation of Schistosoma mansoni monoclonal antibodies which block in-vitro killing: failure to demonstrate blockage of immunity in vivo. Parasite Immunol 1988;10:151-168). M2D3H appeared to have the same epitope specificity as monoclonal antibody 128C3/3 (Weiss J, Magnani JL, Strand M. Identification of Schistosoma mansoni glycolipids that share immunogenic carbohydrate epitopes with glycoproteins. J Immunol. 1986;136:4275-82). The internal epitope was defined structurally by the presence of fucose 3-linked to 3,4-disubstituted N-acetylglucosamine, which was itself partially substituted by a second fucose residue, to yield the determinant -4[Fucalpha1,2Fucalpha3]GlcNAcbeta1-. The second epitope was defined by the anti-LewisX monoclonal antibody 4D1 and was found primarily on cercarial glycolipids. It was chemically characterised as the LewisX epitope of Galbeta1,4[Fucalpha1,3]GlcNAcbeta1- in a terminal position. The removal of fucose greatly diminished the binding of the anti-LewisX and M2D3H monoclonal antibodies, as well as the polyclonal chronic infection sera, to glycolipids of all three life-cycle stages and thus revealed the epitopic importance of fucose.

Schistosome glysoconjugates

Schistosomes are trematodes known as blood flukes that cause schistosomiasis in people and animals. The male and female worms reside mainly in intestinal veins where they lay eggs that result in a wide-ranging pathology in infected individuals. A growing body of evidence indicates that carbohydrates on glycoproteins, glycolipids and glycosaminoglycans synthesized by the parasite are targets of humoral immunity and may play a role in modulating host immune responses. Carbohydrate antigens may provide protective immunity against infection. In addition, recent evidence indicates that glycoconjugates and carbohydrate-binding proteins from the parasites and their hosts participate in egg adhesion and granuloma formation involved in disease pathology. This review will highlight our current knowledge of the glycoconjugates synthesized by the parasites and their immunological and biological properties. There is increasing anticipation in the field that information about the glycobiology of these parasites may lead to carbohydrate-based vaccines and diagnostics for the disease and perhaps new therapies for treating infected individuals.

Synthetic studies on glycosphingolipids from the parasite Echinococcus multilocularis

Novel neutral glycosphingolipids isolated from the metacestodes of Echinococcus multilocularis by Persat, may be expected to be involved in host-parasite interactions. We have synthesized these glycosphingolipid analogues containing 2-branched fatty alkyl residues in place of ceramide. The glycosylation of galactosyl donors 4 and 5 with each of the acceptors 2 and 11 in the presence of N-iodosuccinimide (NIS)/TfOH, and the glycosylation of fucosyl donor 13 with acceptors 12 and 20 in the presence of dimethyl(methylthio)sulfonium triflate (DMTST) gave the desired oligosaccharide derivatives at good yield. The fully per-O-acylated 2-(trimethylsilyl)ethyl glycosides 6, 15, 21, and 26 were converted to glycosylimidates 7, 16, 22, and 27, which were condensed with 2-(tetradecyl)hexadecanol and subsequently deacylated give four target glycosphingolipid analogues.

Molecular characterization of a fucosyltransferase encoded by Schistosoma mansoni

The glycans of schistosomes include many complex carbohydrates that contain fucose. Although the biological functions of these complex carbohydrates are not yet clearly understood, some of these structures are thought to play essential roles in the life cycle of the parasite. Here we present the molecular cloning and characterization of a fucosyltransferase of Schistosoma mansoni with a DNA sequence similarity of 84.6 and 63.7% to mouse and human fucosyltransferase type VII. Southern blot analysis of genomic DNA indicated that this S. mansoni fucosyltransferase is the product of a single gene. The schistosome cDNA sequence that we obtained contains an open reading frame encoding a protein of 351 amino acids with a predicted molecular size of 40.5 kDa. From the amino acid sequence, we predicted two potential N-linked and one O-linked glycosylation site. Western blot studies of extracts from stably transfected CHO cells showed a band corresponding to the schistosome fucosyltransferase at 50 kDa, suggesting that the enzyme is indeed glycosylated. We further demonstrated the expression and enzymatic activity of the fucosyltransferase in the transfected cells by immunofluorescence studies and flow microfluorimetric analysis, which indicated that the enzyme is capable of synthesizing the SLeX blood group determinant but not the LeX determinant in CHO cells. The identification of a fucosyltransferase type VII in schistosomes further underscores the importance of fucose-containing glycans in schistosome glycobiology.

Expression of Lex antigen in Schistosoma japonicum and S.haematobium and immune responses to Lex in infected animals: lack of Lex expression in other trematodes and nematodes

Adults of the human parasitic trematode Schistosoma mansoni, which causes hepatosplenic/intestinal complications in humans, synthesize glycoconjugates containing the Lewis x (Lex) Galbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-->R, but not sialyl Lewis x (sLex), antigen. We now report on our analyses of Lexand sLexexpression in S.haematobium and S.japonicum, which are two other major species of human schistosomes that cause disease, and the possible autoimmunity to these antigens in infected individuals. Antigen expression was evaluated by both ELISA and Western blot analyses of detergent extracts of parasites using monoclonal antibodies. Several high molecular weight glycoproteins in both S. haematobium and S. japonicum contain the Lexantigen, but no sialyl Lexantigen was detected. In addition, sera from humans and rodents infected with S.haematobium and S.japonicum contain antibodies reactive with Lex. These results led us to investigate whether Lexantigens are expressed in other helminths, including the parasitic trematode Fasciola hepatica , the parasitic nematode Dirofilaria immitis (dog heartworm), the ruminant nematode Haemonchus contortus , and the free-living nematode Caenorhabditis elegans . Neither Lexnor sialyl-Lexis detectable in these other helminths. Furthermore, none of the helminths, including schistosomes, express Lea, Leb, Ley, or the H-type 1 antigen. However, several glycoproteins from all helminths analyzed are bound by Lotus tetragonolobus agglutinin , which binds Fucalpha1-->3GlcNAc, and Wisteria floribunda agglutinin, which binds GalNAcbeta1-->4GlcNAc (lacdiNAc or LDN). Thus, schistosomes may be unique among helminths in expressing the Lexantigen, whereas many different helminths may express alpha1,3-fucosylated glycans and the LDN motif.

Identification of an alpha3-fucosyltransferase and a novel alpha2-fucosyltransferase activity in cercariae of the schistosome Trichobilharzia ocellata: biosynthesis of the Fucalpha1-->2Fucalpha1-->3[Gal(NAc)beta1-->4]GlcNAc sequence

Fucose is a major constituent of the protein- and lipid-linked glycans of the various life-cycle stages of schistosomes. These fucosylated glycans are highly antigenic and seem to play a role in the pathology of schistosomiasis. In this article we describe the identification and characterization of two fucosyltransferases (FucTs) in cercariae of the avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1-->4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R alpha1-->2-FucT. Triton X-100 extracts of cercariae were assayed for FucT activity using a variety of acceptor substrates. Type 1 chain (Galbeta1-->3GlcNAc) based compounds were poor acceptors, whereas those based on a type 2 chain (Galbeta1-->4GlcNAc), whether alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether present as oligosaccharide or contained in a glycopeptide or glycoprotein, all served as acceptor substrates. In this respect the schistosomal alpha3-FucT resembles human FucT V and VI rather than other known FucTs. N-ethylmaleimide, an inhibitor of several human FucTs, had no effect on the activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly inhibitory. Large scale incubations were carried out with Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the products of the incubations were isolated using a sequence of chromatographic techniques. By methylation analysis and 2D-TOCSY and ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1-->4[Fucalpha1-->2Fucalpha1-->3]GlcNAc, GalNAcbeta1-->4[Fucalpha1-->2Fucalpha1-->3]GlcNAcbe ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1-->3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2-FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric) Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural element that have been described on schistosomal glycoconjugates.

Glycobiotechnology: enzymes for the synthesis of nucleotide sugars

Complex carbohydrates, as constituting part of glycoconjugates such as glycoproteins, glycolipids, hormones, antibiotics and other secondary metabolites, play an active role in inter- and intracellular communication. The aim of "glycobiotechnology" as an upcoming interdisciplinary research field is to develop highly efficient synthesis strategies, including in vivo and in vitro approaches, in order to bring such complex molecules into analytical and therapeutic studies. The enzymatic synthesis of glycosidic bonds by Leloir-glycosyltransferases is an efficient strategy for obtaining saccharides with absolute stereo- and regioselectivity in high yields and under mild conditions. There are, however, two obstacles hindering the realization of this process on a biotechnological scale, namely the production of recombinant Leloir-glycosyltransferases and the availability of enzymes for the synthesis of nucleotide sugars (the glycosyltransferase donor substrates). The present review surveys some synthetic targets which have attracted the interest of glycobiologists as well as recombinant expression systems which give Leloir-glycosyltransferase activities in the mU and U range. The main part summarizes publications concerned with the complex pathways of primary and secondary nucleotide sugars and the availability and use of these enzymes for synthesis applications. In this context, a survey of our work will demonstrate how enzymes from different sources and pathways can be combined for the synthesis of nucleotide deoxysugars and oligosaccharides.

A novel fucosyltetrahexosylceramide in plerocercoids of the parasite Spirometra erinacei

This glycosphingolipid was tentatively designated as GalSEGLx, in which the carbohydrate structure is characterized by an additional galactose molecule attached to the reducing-end galactose of SEGLx [Gal beta-4 (Fuc alpha-3) Glc beta-3 Gal beta Cer], which was previously determined by us [Kawakami, Y., Nakamura, K., Kojima, H., Suzuki, M., Inagaki, F., Suzuki, A., Sonoki, S., Uchida, A., Murata, Y. & Tamai, Y. (1993) J. Biochem. 114, 677-683], through a beta 1-6 linkage. The ceramide contained sphinganine and 4D-hydroxysphinganine in an about equimolar ratio, and a non-hydroxy fatty acid with carbon atoms ranging from 16 to 28, 26:0, 28:0 and 28:1 being major components. Based on the finding that a novel carbohydrate structure. Gal beta-4 Glc beta-3 Gal, was commonly found in glycosphingolipids from the parasite, S. erinacei, we here propose the terms, spirometo series, for this core structure series, and spirometosides, for glycosphingolipids having this carbohydrate structure.

Stage-specific expression of fuco-neolacto- (Lewis X) and ganglio-series neutral glycosphingolipids during brain development: characterization of Lewis X and related glycosphingolipids in bovine, human and rat brain

We have purified and characterized a bovine brain pentaglycosylceramide as Lewis X and identified it in human and rat brain using anti-Lewis X (anti-SSEA 1) monoclonal antibody. Neutral glycosphingolipid expression in developing rat brain has been examined by digoxigenin immunostaining and TLC-immunostaining using anti-SSEA 1 and anti-GgOse4Cer (GA1) monoclonal antibodies. Five transient Lewis X-series bands were identified in brain at embryonic day 15 that disappear by postnatal day 5 (one disappears at embryonic day 18). Gangliotetraosylceramide (GA1) first appears at embryonic day 21 and increases in concentration with age until postnatal day 21. In addition, we have purified another minor brain neutral glycosphingolipid and tentatively identified it as a Lewis X-series glycolipid by gas chromatography-mass spectrometry analysis followed by TLC-immunostaining with anti-SSEA 1 antibody.

Characterization of fucosyllactose determinant-bearing glycoproteins probed by a Biomphalaria alexandrina lectin in Schistosoma mansoni cercariae

Utilizing a Biomphalaria alexandrina-derived lectin (BaSII) of proven specificity to a Schistosoma mansoni-associated fucosyllactose [(Fuc alpha 1-2) Gal beta 1-4 Glc] determinant, two determinant-bearing glycoproteins of 40 and 37 kDa were found to be synthesized by the cercarial stage of the parasite. The two glycoproteins were isolated by BaSII affinity column chromatography from extracts of cercariae metabolically radiolabelled with 35S-methionine. Treatments with endoglycosidases, alkaline borohydride, as well as concanavalin A column chromatography and analysis by two-dimensional gels indicated that the two glycoproteins are synthesized as a single 33 kDa polypeptide backbone that is differentially glycosylated with one and/or two determinant-bearing N-linked complex-type glycan units of either the biantennary, or, to a lesser extent, the tri- or tetra-antennary types. The two glycoproteins lack other conventional high mannose-type or O-linked glycans, and the distinct structures of the complex-type oligosaccharides accounted solely for the expression of three isomorphs for each determinant-bearing glycoprotein. Based on the structural relatedness of the fucosyllactose determinant to the antigenic mammalian blood group H trisaccharide, our observations may have implications in mechanisms of host-parasite interactions as well as immunoprophylaxis.

Neutral glycolipids of Schistosoma mansoni as feasible antigens in the detection of schistosomiasis

The neutral glycolipid fraction from mouse-propagated, Schistosoma mansoni adult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.

Evidence for a family of schistosome glycan-binding lectins in Biomphalaria alexandrina

A novel family of isolectins that selectively recognize a schistosome-associated fucosyllactose determinant was identified in the hemolymph of Biomphalaria alexandrina, a snail vector of Schistosoma mansoni. Three lectins of this family were purified by serial affinity chromatography on a column of L-fucose and elution with a gradient of 0.1-1 M L-fucose (designated BaSII and BaSIII), followed by a column of D-glucose and elution with 0.3 M D-glucose (designated BaSI). Assessment of the structural characteristics by one- and two-dimensional gels indicated that, inspite of similarities in native molecular weights, the three lectins were tetramers of noncovalently-associated subunits that were of different sizes and pIs in BaSI, and of equal size but distinct pIs in BaSII and BaSIII. Comparisons of two-dimensional gels of the glycosylated and deglycosylated forms were consistent with the presence of an invariant alpha subunit (13.2 kDa, pI 7.2) constituting the three deglycosylated lectins, which associates with other subunits unique to each lectin, namely a beta subunit (10.1 kDa, pI 5.8) in BaSI, an alpha 1 subunit (13.2 kDa, pI 6.8) in BaSII and BaSIII, and an alpha 2 subunit (13.2 kDa, pI 7.0) in BaSIII. Each of these subunits is subjected to differential post-translational N-linked glycosylations, which accounts for the additional heterogeneity expressed by the glycosylated lectins. Based on miracidial glycoprotein binding and inhibition assays, the three lectins exhibited optimum binding at similar pH and temperature, but were distinct in their binding affinities towards the fucose moiety constituting the fucosyllactose target. These observations indicate that an oligomorphic family of recognition molecules may have evolved to regulate the snails' response to schistosomes.

A unique multifucosylated -3GalNAc beta 1-->4GlcNAc beta 1-->3Gal alpha 1- motif constitutes the repeating unit of the complex O-glycans derived from the cercarial glycocalyx of Schistosoma mansoni

The entire surface of the cercarial stage of the human blood fluke Schistosoma mansoni is covered by a 1-microns thick, highly immunogenic, fucose-rich glycocalyx (GCX). Using strategies based on enzymatic, chemical, and mass spectrometric analysis, we have defined the structures of the major glycans released by reductive elimination from GCX. They comprise a heterogeneous population of multifocosylated complex oligosaccharides with the following nonreducing terminal sequences: [formula: see text] Our structural data suggest that these tri- to pentafucosylated epitopes are carried on type 1, R-->Gal beta-1-->3GalNAc, and type 2, R-->Gal beta 1-->3(R-->GlcNAc beta-1-->6)GalNAc, core structures via repeat units of (3GalNAc beta 1-->4(Fuc alpha 1-->2Fuc alpha 1-->2Fuc alpha 1-->3)GlcNAc beta-1-->3Gal alpha-->)n, where n is mainly 0 and 1, and all sugars are in the pyranose form. The proposed structure represents the first instance where an alpha-galactosylated beta-GalNAc(1-->4)-beta-GlcNAc sequence occurs as a repeating unit in a glycoprotein. It is also unique in being substituted with oligofucosyl appendages. The unusual oligosaccharide structures described here, particularly the potentially immunodominant oligofucosyl moieties, are most likely responsible for the known potency of GCX in modulating various immune responses including complement activation, B cell mitogenesis, and delayed type hypersensitivity in schistosomiasis.

Initiation of chemical studies on the immunoreactive glycolipids of adult Ascaris suum

There is a general lack of basic information concerning one class of glycoconjugate, the glycolipids, from parasitic nematodes. As the prototype, the neutral glycolipid fraction derived from adult males of Ascaris suum was investigated as to its chromatographic, differential chemical staining, antigenic and chemical properties. The thin-layer chromatography-resolved neutral fraction glycolipids could be classified into components of fast and slow migrating band groups. Immunoreactivity was restricted to the latter as detected by IgG and IgM anti-neutral fraction glycolipid antibody levels in serial infection sera of mice. Similarities of chromatography, antigenicity and serological cross-reactivity have been extended to the neutral glycolipid fractions of other parasitic nematodes: Litomosoides carinii and Nippostrongylus brasiliensis. Chemical, differential chemical staining and enzymatic analyses identified the Ascaris suum antigenic, slow migrating band group of components as amphoteric glycosphingolipids, and not the originally hypothesized glycoglycerolipids or glycosylphosphatidylinositols, that contained typical neutral monosaccharide constituents and a zwitterionic phosphodiester linkage, most probably phosphocholine. Glycosphingolipid-immunoreactivity is eliminated on cleavage of the zwitterionic phosphodiester linkage by hydrofluoric acid treatment.

Litomosoides carinii: macrofilariae-derived glycolipids--chromatography, serology and potential in the evaluation of anthelminthic efficacy

A preliminary characterization of the glycolipids of Litomosoides carinii macrofilariae, resolved according to their chromatographic, chemical and serological properties, has been performed. Emphasis has been placed on the neutral fraction glycolipids. These are separable on thinlayer chromatography into two groups of fast and slow migrating band components, that differ in their migration, differential chemical staining and serological traits, respectively. Serological analyses have been accomplished by thin-layer chromatography immunostaining and ELISA. Only components of the slow migrating band group react with infection serum from Litomosoides carinii-infected Mastomys coucha. Cross-reactivity experiments with homologous and heterologous infection sera of various helminthiases indicate that, epitopes bound to the neutral glycolipid fraction show structural similarity within the Nematoda, but not to the Cestoda or Trematoda. The dynamic development of specific Ig-, IgG- and IgM-anti-neutral glycolipid fraction antibody levels were correlated with the different progression of L. carinii and Brugia malayi infections in the multimammate rat, Mastomys coucha. The reduction in the dynamics of IgG- and IgM-antibody levels on chemotherapeutic treatment with the filaricides flubendazole and CGP 20376 has been related to their macrofilaricide-activity.

The immunologically reactive O-linked polysaccharide chains derived from circulating cathodic antigen isolated from the human blood fluke Schistosoma mansoni have Lewis x as repeating unit

The gut-associated excretory antigen circulating cathodic antigen (CCA) was isolated by immunoaffinity chromatography from adult Schistosoma mansoni worms, which were collected from infected golden hamsters. This antigen is probably involved in protection of the schistosome gut and is increasingly used in highly sensitive and specific immunodiagnostic assays. Amino acid analysis before and after alkaline borohydride treatment of CCA and monosaccharide analysis indicated that CCA is O-glycosylated mostly via GalNAc-Thr. After reductive alkaline treatment, the O-linked carbohydrate chains were fractionated by gel-permeation chromatography, followed by normal-phase HPLC on LiChrosorb-NH2. Carbohydrate-positive fractions were investigated by one-dimensional and two-dimensional 1H-NMR spectroscopy, fast atom bombardment mass spectrometry and collision-induced-dissociation tandem mass spectrometry. The analyses showed that the low-molecular-mass O-linked oligosaccharide alditols (the minor fraction) consist of disaccharides to hexasaccharides having the Gal beta (1-3)GalNAc-OL core in common. The major carbohydrate fraction comprises a population of polysaccharides, containing Lewis x repeating units (-3)Gal beta (1-4)[Fuc alpha (1-3)]GlcNAc beta (1-). CCA-specific monoclonal antibodies and IgM antibodies in patient sera recognized the fucosylated O-linked carbohydrate antigenic structures. Since CCA evokes a strong IgM antibody response and carbohydrate structures containing repeating Lewis x units are found on circulating neutrophils, it is proposed that the antigenic poly-Lewis x polysaccharide of CCA is involved in the induction of auto-immunity against granulocytes, resulting in the mild to moderate neutropenia observed during schistosome infection.

Schistosoma mansoni: immunolocalization of two different fucose-containing carbohydrate epitopes

We have used two monoclonal antibodies, 128C3/3 and 504B1, to immunolocalize their carbohydrate epitopes in different developmental stages of Schistosoma mansoni. Both epitopes contain fucose: mAb 128C3/3, as we have shown previously, recognizes fucose in a novel, possibly internal linkage (Levery et al. 1992) while mAb 504B1, as we show here, bound to the Le(x) epitope, which contains fucose alpha 1-->3 linked to N-acetyl-glucosamine. The tissue expression of these epitopes was strikingly different and both elicit an immune response in infected hosts. The mAb 128C3/3-defined epitope was exposed on the surface of all larval stages but not on adult worms; however, it was found in the excretory system of adult worms of both sexes. In contrast, surface expression of the Le(x) epitope was initiated after the transformation of cercariae to schistosomula and was maintained throughout the adult life in both sexes.

Characterization of novel fucosyl- and tyvelosyl-containing glycoconjugates from Trichinella spiralis muscle stage larvae

The monosaccharide composition of an affinity-purified family of antigenically-related Trichinella spiralis larval glycoproteins was determined by gas chromatography/mass spectrometry. This group of 6 major glycoproteins, designated TSL-1, originates in the muscle stage (L1) larval stichosome. They are present on the L1 surface and in excretory/secretory products of L1 larvae, are stage-specific, and are highly immunodominant. The glycosyl composition of the TSL-1 antigens was remarkable in 2 respects: (1) fucose accounted for 36 molar percent of the glycosyl residues; and (2) a 3,6-dideoxyhexose was identified, which accounted for at least 24 molar percent of the glycosyl residues. Previously, 3,6-dideoxyhexoses have been found only in certain Gram-negative bacterial lipopolysaccharides and in ascaroside alcohols (ascarylose) of Ascaris eggs. The 3,6-dideoxyhexose found in the TSL-1 antigens also was found in ES. This Trichinella sugar has been chemically identified as a 3,6-dideoxyarabinohexose, the same as found in Ascaris eggs. However, the absolute configuration of the TSL-1 sugar is D-(tyvelose), not L-(ascarylose) as is found in Ascaris eggs. Methylation analysis indicated that the TSL-1 3,6-dideoxy-D-arabinohexose was present entirely as non-reducing terminal residues. Approximately 83% of the fucose was also present as non-reducing terminal residues, with the remaining fucose found as 3,4-linked branched residues.

A novel saccharide structure, Xyl 1----3 Gal 1----(SO3-)3,4 Fuc----, is present in acrosome reaction-inducing substance of the starfish, Asterias amurensis

The jelly coat of echinoderm eggs contains a glycoconjugate, acrosome reaction-inducing substance (ARIS), that is essential for triggering the acrosome reaction in homologous spermatozoa. In the starfish, Asterias amurensis, ARIS is a sulfated glycoprotein of an apparent molecular size of greater than 10(7). Since its biological activity is dependent mostly on its sugar moiety, oligosaccharides liberated by hydrolysis with 10 mM H2SO4 for 60 min at 100 degrees C from pronase digests of ARIS (P-ARIS) were chemically analyzed. The main oligosaccharide purified by high-performance anion-exchange chromatography was determined to be Xyl1----3Gal1----(SO3-)3,4Fuc by compositional analysis and FAB mass spectrometry. This structure indicates that ARIS possesses a novel saccharide chain having sulfated fucose as an internal residue.