Structure of Forssman hapten glycosphingolipid from sheep erythrocytes

Characterization of sheep erythrocyte glycosphingolipids recognized by human anti-Forssman antibodies

The FORS histo-blood group system is the most recently discovered carbohydrate-based human blood group system. FORS is a rare blood group system, and most individuals have naturally occurring anti-FORS1 antibodies in plasma. Screening for anti-FORS1 antibodies is often done by hemagglutination assays using FORS1-expressing sheep erythrocytes, since FORS1-positive human erythrocytes are most often not available. Here, we have characterized the non-acid glycosphingolipids from sheep erythrocytes and isolated subfractions, with mass spectrometry, binding of antibodies and lectins, and by enzymatic hydrolysis. This demonstrated the presence of Forssman and Galili pentaosylceramides, and a Galili heptaosylceramide. Two complex glycosphingolipids recognized by human anti-FORS1 antibodies were characterized as a Forssman neolacto hybrid hexaosylceramide (GalNAcα3GalNAcβ3Galβ4GlcNAcβ3Galβ4Glcβ1Cer) and a Forssman Galili hybrid heptaosylceramide (GalNAcα3GalNAcβ3Galα3Galβ4GlcNAcβ3Galβ4Glcβ1Cer). These are novel glycosphingolipid structures, and to our knowledge, the first case of an elongated Galili antigen. Thus, the anti-Forssman antibodies in human serum bind not only to the classical Forssman pentaosylceramide (GalNAcα3GalNAcβ3Galα4Galβ4Glcβ1Cer), but also when the GalNAcα3GalNAcβ3 sequence is presented on a neolacto core chain and even on a Galili carbohydrate sequence.

Mouse monoclonal antibodies to pneumococcal C-polysaccharide backbone show restricted usage of VH-DH-JH gene segments and share the same kappa chain

The immunization of BALB/c mice with heat-killed cells of Streptococcus mitis SK598 allowed the rescue of mouse monoclonal antibodies (mAbs) reactive with the pneumococcal cell wall C-polysaccharide backbone. We report for the first time the genetic and molecular characterization of these mAbs, which altogether reflect a typical thymus-independent type 2 immune response. They were isotype-diverse (IgM, IgG1, IgG2b and IgG3). They made use of restricted and scarcely mutated VH-DH-JH combinations, and the same kappa chain, essentially in germ line configuration. Interestingly, this light chain was also found making up part of an anti-phosphorylcholine mAb. These mAbs were not inhibited by phosphorylcholine and related compounds, nor N-acetylneuraminic acid (NANA), nor the Forssman disaccharide; some of them showed limited reactivity with the meningococcal C polysaccharide. Their CDR-H3s do not show any recognizable patterns resembling those found in antibodies to bacterial polysaccharides that have already been characterized.

Purification, characterization, and cDNA cloning of alpha-N-acetylgalactosamine-specific lectin from starfish, Asterina pectinifera

We report here the purification, characterization, and cDNA cloning of a novel N-acetylgalactosamine-specific lectin from starfish, Asterina pectinifera. The purified lectin showed 19-kDa, 41-kDa, and 60-kDa protein bands on SDS-PAGE, possibly corresponding to a monomer, homodimer, and homotrimer. Interestingly, on 4-20% native PAGE the lectin showed at least nine protein bands, among which oligomers containing six to nine subunits had potent hemagglutination activity for sheep erythrocytes. The hemagglutination activity of the lectin was specifically inhibited by N-acetylgalactosamine, Tn antigen, and blood group A trisaccharide, but not by N-acetylglucosamine, galactose, galactosamine, or blood group B trisaccharide. The specificity of the lectin was further examined using various glycosphingolipids and biotin-labeled lectin. The lectin was found to bind to Gb5Cer, but not Gb4Cer, Gb3Cer, GM1a, GM2, or asialo-GM2, indicating that the lectin specifically binds to the terminal alpha-GalNAc at the nonreducing end. The hemagglutination activity of the lectin was completely abolished by chelation with EDTA or EGTA and completely restored by the addition of CaCl(2). cDNA cloning of the lectin showed that the protein is composed of 168 amino acids, including a signal sequence of 18 residues, and possesses the typical C-type lectin motif. These findings indicate that the protein is a C-type lectin. The recombinant lectin, produced in a soluble form by Escherichia coli, showed binding activity for asialomucin in the presence of Ca(2+) but no hemagglutination.

The aqueous solution structure of the tetrasaccharide-ribitol repeat-unit from the lipoteichoic acid of Streptococcus pneumoniae strain R6 determined using a combination of NMR spectroscopy and computer calculations

High-resolution 1D- and 2D-correlation 1H NMR and 13C NMR, at 500 and 125 MHz, respectively, permitted assignment of the majority of the resonances in the per-N-acetylated, phosphorylated tetrasaccharide-ribitol repeat-unit, and in the complete polymer (n = 5 - 7) containing between five and seven repeating units attached to the deacylated lipid anchor, for the lipoteichoic acid from Streptococcus pneumoniae strain R6; the 31P resonances were also assigned. Comparison of the 31P spectra obtained for the per-N-acetylated oligosaccharide and for the oligosaccharide having the AATG 4-NH2 group still free, indicate a conformational difference brought about by interaction between the amino group and the neighboring phosphate group.

The structure of pneumococcal lipoteichoic acid. Improved preparation, chemical and mass spectrometric studies

Pneumococcal lipoteichoic acid was extracted and purified by a novel, quick and effective procedure. Structural analysis included methylation, periodate oxidation, Smith degradation, oxidation with CrO3, and fast-atom-bombardment mass spectrometry. Hydrolysis with 48% (by mass) HF and subsequent phase partition yielded the lipid anchor (I), the dephosphorylated repeating unit of the chain (II) and a cleavage product of the latter (III). The proposed structures are: (I) Glc(beta 1----3)AATGal(beta 1----3)Glc(alpha 1----3)acyl2Gro, (II) Glc(beta 1----3)AATGal(alpha 1----4)GalNAc(alpha 1----3)GalNAc(beta 1----1)ribitol and (III) Glc(beta 1----3)AATGal(alpha 1----4)GalNAc(alpha 1----3)GalNAc, where AATGal is 2-acetamido-4-amino-2,4,6-trideoxygalactose, and all sugars are in the pyranose form and belong to the D-series. Alkaline phosphodiester cleavage of lipoteichoic acid, followed by treatment with phosphomonoesterase, resulted in the formation of II and IV, with IV as the prevailing species: [sequence: see text] The linkage between the repeating units was established as phosphodiester bond between ribitol 5-phosphate and position 6 of the glucosyl residue of adjacent units. The chain was shown to be linked to the lipid anchor by a phosphodiester between its ribitol 5-phosphate terminus and position 6 of the non-reducing glucosyl terminus of I. The lipoteichoic acid is polydisperse: the chain length may vary between 2 and 8 repeating units and variations were also observed for the fatty acid composition of the diacylglycerol moiety. Preliminary results suggest that repeating units II and IV are enriched in separate molecular species. All species were associated with Forssman antigenicity, albeit to a various extent when related to the non-phosphocholine phosphorus. Owing to its unique structure, the described macroamphiphile may be classified as atypical lipoteichoic acid.

Glycolipid-lectin interactions: reactivity of lectins from Helix pomatia, Wisteria floribunda, and Dolichos biflorus with glycolipids containing N-acetylgalactosamine

The autoradiographic detection of 125I-labeled lectins binding to glycolipids on thin-layer chromatograms can be used to rapidly analyze total glycolipid extracts of cells or tissues for specific oligosaccharide structures. The Helix pomatia lectin which binds with high affinity to terminal alpha-linked GalNAc residues did not bind to globoside (terminal beta 1-3GalNAc) but did bind the ganglioside GM2 and its asialo derivative which have terminal beta 1-4GalNAc residues. The lectin from Dolichos biflorus bound specifically to the Forssman glycolipid with relatively low affinity. The lectin from Wisteria floribunda was bound to Forssman glycolipid, globoside, and the asialo derivative of the ganglioside GM2. The interactions of these lectins with the glycolipid-derived, 3H-labeled oligosaccharides was also analyzed by affinity chromatography. The results indicated that the reactivity of multivalent carbohydrate-binding proteins with polyvalent surfaces of glycolipids is strong enough to permit detection of low-affinity interactions that may not be observed in binding assays that are based on carbohydrate-protein interactions in solution. The autoradiographic analysis of 125I-Helix pomatia lectin binding to thin-layer chromatograms of total lipid extracts from human erythrocyte membranes detected the quantitative differences in the A-active glycolipids from type A1 and A2 cells.

A quantitative analysis of cell surface glycosphingolipid with a fluorescence activated cell sorter

The fluorescence activated cell sorter (FACS) was used with an indirect membrane immunofluorescence technique to detect antibody against the Forssman antigen, a glycosphingolipid. Sheep erythrocytes, which contain Forssman antigen as a major membrane glycosphingolipid, were used as the target antigen. Detection of the anti-Forssman antibody on the sheep erythrocytes was done with specific fluorescein-conjugated second antibody and analyzed on a FACS. Compared to other available methods, analysis with the FACS was simple, sensitive, reproducible and quantitative. More than 250 pg of antibody could be detected. In addition, as little as 1 ng of Forssman antigen could be estimated by a binding inhibition experiment.

SV40 tumor rejection induced by vesicular stomatitis virus bearing SV40 tumor-specific transplantation antigen (SV40-TSTA). II. Association of SV40-TSTA activity with liposomes containing VSV glycolipids

Highly purified vesicular stomatitis virus (VSV) was obtained from VSV-infected SV40-transformed and from "normal" hamster cell lines. A glycolipid extract was prepared from these VSV preparations according to the Folch partition procedure. These glycolipids were rendered immunogenic to the Syrian hamsters when incorporated within liposomal membranes composed of lecithin/sphingomyelin/cholesterol (1/1/2 by weight). When the glycolipids were extracted from VSV grown on cell lines (TSV5-cl2 and EHSVi-cl1) which contained the SV40 tumor-specific transplantation antigen (SV40-TSTA), it was possible either to induce a tumor rejection or at least to slow the growth of the tumor in Syrian hamsters challenged with TSV5-cl2 cells. No protection was obtained in animals treated with liposomes containing glycolipids extracted from purified VSV grown on SV40-TSTA-negative cells (EHB). The SV40-TSTA could be a glycolipid of the transformed cell membrane which is incorporated within the VSV envelope.

Isolation and partial characterization of the heterophile antigen of infectious mononucleosis from bovine erythrocytes

The heterophile antigen (Paul-Bunnell antigen, PBA) of infectious mononucleosis was isolated by extraction of an aqueous suspension of bovine erythrocyte stromata with chloroform-methanol (2:1). The upper aqueous layer contained gangliosides, PBA, and a high-molecular-weight glycoprotein. PBA and gangliosides were separated from the high-molecular-weight glycoprotein by extraction of lyophilized upper layer with chloroform-methanol solvents. Separation of PBA from gangliosides was carried out by chromatography on DEAE-cellulose with chloroform-methanol solvents. PBA appeared to be a minor glycoprotein component of the erythrocyte membrane and had both hydrophobic and hydrophilic properties. It was soluble in either organic or aqueous solvents. On SDS-polyacrylamide gel electrophoresis, it migrated as a single component that stained for protein with Coomassie blue, for carbohydrate with periodic acid-Schiff reagent, and for lipid with oil red 0; it had an apparent molecular weight of 26,000. It was composed of 62% protein with major amino acids; glutamic acid, proline, glycine, isoleucine, leucine, and threonine (158, 116, 98, 90, 85, and 82 residues per 1,000 residues, respectively). Carbohydrate content was 9.2% with major sugar constituents: sialic acid, galactosamine, and galactose. Serologic activity of PBA was destroyed by pronase but not by trypsin.

Characterization of B and H blood-group active glycosphingolopids from human B erythrocyte membranes

Two blood group B active glycosphingolipids (B-I and B-II) previously isolated and highly purified from human B erythrocytes [21] were analysed first by degradation with alpha-D-galactosidase from coffee beans, alpha-L-fucosidase from bovine kidney and with 0,1 N trichloracetic acid; the native B-glycolipids as well as their degradation products were then investigated by methylation analysis with combined gas chromatography-mass spectromety, by thin layer chromatography, two dimensional immunodiffusion and by the hemagglutination inhibition technique. Together with the results obtained by mass spectrometry of permethylated glycolipids [26] the following structures were elucidated: alpha-D-gakactpurampsu;-(1 leads to 3) [alpha-L-fucopyranosyl-(1 leads to 2)]-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-(1 leads to 1)-ceramide for the B-I glycosphingolipid and alpha-D-galactopyransosyl-(1 leads to 3)-[alpha-L-fucopyranosyl-(1 leads to 2)]-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-(1 leads to 1)-ceramide for the B-II glycophingolipid. AH active glycolipid fraction from B erythrocytes further purified by thin layer chromatography was also investigated by methylation analysis. The pattern of its partially methylated alditol acetates was essentially the same as that of the alpha-galactosidase treated and permethylated B-I glycoliped. It is also exhibited strongly precipitating and hemagglutination inhibiting H properties as well as the two alpha-galactosidase treated B-I and B-II glycosphingolipids. Based upon these data the following tentative structure was proposed: alpha-L-fucopyranosyl-(1 leads to 2)-D-galactopyranosyl-(1 leads to 4)-N-acetyl-D-glucosaminosyl-(1 leads to 3)-D-Galactopyranosyl-(1 leads to 4)-D-glucopyranosyl-( 1 leads to 1)-ceramide. Gas chromatographic analysis revealed sphingosine and lignoceric, nervonic and behenic acids to be the main components of the ceramide residues of the three glycophingolipids. From the data presented the H active substance very probably can be regarded as the immediate precursor of the B-I gly cosphingolipid from human B erythrocyte membranes.