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Abstract

Glycoproteins from the ruminant helminthic parasite Haemonchus contortus react with Lotus tetragonolobus agglutinin and Wisteria floribunda agglutinin, which are plant lectins that recognize alpha1,3-fucosylated GlcNAc and terminal beta-GalNAc residues, respectively. However, parasite glycoconjugates are not reactive with Ricinus communis agglutinin, which binds to terminal beta-Gal, and the glycoconjugates lack the Lewis x (Le(x)) antigen or other related fucose-containing antigens, such as sialylated Le(x), Le(a), Le(b) Le(y), or H-type 1. Direct assays of parasite extracts demonstrate the presence of an alpha1,3-fucosyltransferase (alpha1,3FT) and beta1,4-N-acetylgalactosaminyltransferase (beta1,4GalNAcT), but not beta1,4-galactosyltransferase. The H. contortus alpha1,3FT can fucosylate GlcNAc residues in both lacto-N-neotetraose (LNnT) Galalpha1-->4GlcNAcbeta1-->3Galbeta1-->4Glc to form lacto-N-fucopentaose III Galbeta1-->4[Fuca1-->3]GlcNAc beta1-->3Galbeta1-4GIc, which contains the Le(x) antigen, and the acceptor lacdiNAc (LDN) GalNAcbeta1-->4GlcNAc to form GalNAc beta1-->4[Fualpha1-->3]GlcNAc. The alpha1,3FT activity towards LNnT is dependent on time, protein, and GDP-Fuc concentration with a Km 50 microM and a Vmax of 10.8 nmol-mg(-1) h(-1). The enzyme is unusually resistant to inhibition by the sulfhydryl-modifying reagent N-ethylmaleimide. The alpha1,3FT acts best with type-2 glycan acceptors (Galbeta1-->4GlcNAcbeta1-R) and can use both sialylated and non-sialylated acceptors. Thus, although in vitro the H. contortus alpha1,3FT can synthesize the Le(x) antigen, in vivo the enzyme may instead participate in synthesis of fucosylated LDN or related structures, as found in other helminths.

Sweet secrets of a therapeutic worm: mass-spectrometric N-glycomic analysis of Trichuris suis

“…Antennal fucosylation in T. suis also occurred in the absence of a phosphorylcholine modification and is probably in the form of fucosylated LacdiNAc as present in insects and trematodes [43,48]. As judged by retention times and example digests, antennal fucose is predominantly on the lower arm and we recently found co-eluting N-glycans in both H. contortus and Anopheles gambiae [39,20]; both these species express compatible fucosyltransferase activities [49,50] . However, an antibody recognising fucosylated LacdiNAc only poorly reacted with T. suis soluble products [13], which could be due to the localisation of this epitope only in certain tissues or proteins of the parasite or steric hindrance when this motif also carries phosphorylcholine.…”

Molecular Basis of Anti-horseradish Peroxidase Staining in Caenorhabditis elegans

“…To date the exact structures of only some of the fucosylated N-and O-glycans are known (2, 9), whereas no fucosylated glycolipids have as yet been detected. There is also only fragmented data on the fucosylation of other nematodes: up to three fucose residues on the core of N-glycans (45,46) and the presence of a Lewis-type fucosyltransferase (47) in Haemonchus, fucosylation of artho-series glycolipids from Ascaris suum (48), and the presence of Lewis epitopes in Dictyocaulus viviparus (49). In C. elegans, the single obvious ␣1,6-fucosyltransferase homologue (FUT-8) has been expressed in an active recombinant form, 4 and the determination of the enzymatic activity of only one ␣1,2-fucosyltransferase (FUT-2 or CE2FT1) has been published (16) but left its biological substrate unrevealed.…”

How helminths use excretory secretory fractions to modulate dendritic cells

“…Le x is also expressed by nematodes such as Dictyocaulus viviparus 18 and antisera against structures containing Le x are raised during infection with Taenia crassiceps and T. spiralis 19 , 20 . In addition, many helminths have been shown to express an enzyme responsible for the production of Le x 21 - 24 …”

“…Immunodominant helminth glycans were first identified, and have largely been characterized via the analysis of protective antibodies from the serum of immune animals 21 . Lewis x or Le x was one of the first helminth glycan antigens to be described in the immune sera of mice infected with S. mansoni 43 - 45 .…”