Chemical inhibition of α-mannosidase in S. mansoni schistosomula leads to reshaped N-glycosylation associated with developmental alterations

Schistosomiasis, a neglected tropical disease caused by parasitic flatworms of the genus Schistosoma, afflicts more than 230 million people worldwide, and the parasites responsible can survive for decades inside the human body. A research team led by Eleonore Kuhlemaijer, Angela van Diepen and Cornelis Hokke at the Leiden University Medical Center, working with colleagues at Aberystwyth University and the University of Oxford, has now shown that chemically reshaping the N-glycans of developing schistosome larvae can visibly disturb their development. The study, published in Frontiers in Parasitology, offers one of the most direct demonstrations to date that the parasite’s sugar coat is not merely decorative but is woven into the fabric of its own maturation.

N-glycosylation is a conserved enzymatic process in eukaryotes that begins in the endoplasmic reticulum, where a Glc3Man9GlcNAc2 precursor is transferred to a growing peptide chain, and continues in the Golgi apparatus, where mannose residues are trimmed and distinct terminal motifs are added. The resulting glycans influence protein folding, receptor-ligand binding and cell adhesion, and their alteration in humans underlies congenital disorders of glycosylation and lysosomal storage disease. Schistosomes display characteristic N-glycan motifs, including LacdiNAc, multi-fucosylated LacdiNAc and LacNAc, together with core β1-2xylose and α1-6fucose modifications that are absent from human glycans. Each schistosome species and life stage carries its own glycan signature, and as the larvae journey through the mammalian host, the profile changes dynamically: core xylose and fucosylated LacNAc decline while LacdiNAc rises, sex-specific glycans eventually distinguish adult females from males, and glycans on extracellular vesicles released by the parasite shift in parallel, mediating recognition by host C-type lectin receptors.

To probe whether this shifting sugar landscape matters for development, the team cultured newly transformed Schistosoma mansoni schistosomula in vitro for up to six weeks, mimicking the larval maturation that normally takes five to seven weeks inside the host. They remodelled the parasite N-glycome with two α-mannosidase inhibitors: kifunensine, which blocks α-mannosidase I and thereby prevents the removal of α1-2-linked mannose residues, and swainsonine, which inhibits Golgi α-mannosidase II as well as lysosomal and cytosolic α-mannosidases. A high-throughput imaging screen showed that neither compound had any overt toxicity: after 72 and 120 hours of exposure, the motility and phenotype scores of treated schistosomula clustered with negative controls, while parasites exposed to the known anti-schistosomal compounds auranofin and praziquantel scored aberrantly on both metrics.

The glycan analysis revealed how profoundly the inhibitors reshaped the parasite’s N-glycosylation. Newly transformed schistosomula carried a median of 84.9 percent complex N-glycans, but within the first week of culture the profile shifted markedly, with control parasites settling at roughly 60 percent complex and 30 percent oligomannose structures. Kifunensine treatment pushed oligomannose N-glycans to 72.2 percent at week one, dominated by structures with nine (M9) and eight (M8) mannose residues, and by week six oligomannose accounted for 93 percent of the profile. Swainsonine produced a different signature: oligomannose at 44.4 percent, hybrid N-glycans at 11.4 percent, and, strikingly, free N-glycans bearing only one core GlcNAc at 16.4 percent, an effect attributed to inhibition of cytosolic α-mannosidase. The inhibitors also suppressed the developmental motifs: in kifunensine-treated parasites, core xylose fell from 11.2 percent at week one to one percent or less from week three onwards, core fucose dropped from 24.1 percent to around three percent or less, the LacNAc motif dwindled and the rise of LacdiNAc was prevented entirely. Swainsonine had a milder effect on core modifications but clearly curtailed LacNAc and LacdiNAc, which sit mostly on complex glycans.

Western and lectin blotting confirmed that these mass spectrometric changes were reflected at the glycoprotein level. The lectin Concanavalin A, which binds strongly to high-mannose structures, detected additional glycoprotein bands in kifunensine-treated parasites at weeks three and six, while the monoclonal antibody 100-4G11, which recognises the trimannosyl core motif, revealed an intense band between 25 and 37 kilodaltons after swainsonine treatment. The team also corrected meticulously for human-derived N-glycans contaminating the parasite extracts, since the culture medium contains human serum and red blood cells, using sialylated marker structures to subtract the host contribution from each spectrum.

Perhaps the most consequential finding emerged from the microscopy. By week four, a subset of continuously kifunensine-treated schistosomula developed local oedema: the body became locally bloated and darkened by what appeared to be accumulated hemozoin in the gut. The phenotype affected 8.2 percent of parasites at week four, rising to 21.9 percent at week six, compared with only 3.4 percent in controls, and it appeared consistently across three biological replicates. Confocal imaging with live dyes for nuclei, actin and cell membranes confirmed the gut disorganisation and revealed similar, subtler alterations in swainsonine-treated parasites that brightfield microscopy had missed. Normal developmental landmarks, including oral and ventral suckers, oesophagus, muscle layer, tegument and the beginnings of sexual dimorphism, were nonetheless evident in all conditions by week six.

Crucially, the team also discontinued the inhibitor treatment after the first week. The N-glycan profiles of both kifunensine- and swainsonine-treated parasites then recovered, returning to a pattern similar to controls by week three, and no oedema or other visible abnormality appeared at week four or later. This temporal dissociation is telling: sustained glycan perturbation during the larval maturation period disturbed development, whereas a brief glycan shift confined to the first week did not. The authors suggest that the oedema could stem from altered N-glycosylation of cell adhesion proteins such as E-cadherin and integrins, whose adhesive functions are known to depend on their glycan type, or from disruption of the digestive function of the schistosome gut, whose glycoproteins carry highly complex N-glycans. Differentiation of mammalian intestinal epithelial cells is itself accompanied by a decrease in highly mannosylated structures and upregulation of Golgi α-mannosidases, hinting that mannose trimming is a signal for tissue organisation in the parasite as well.

The study builds on the team’s earlier work showing that the same inhibitors remodelled the N-glycans of adult schistosomes without apparent harm, and it now extends glycan remodelling to the larval stage, where development is most extensive and the glycan profile changes most dynamically. The in vitro maturation of the control parasites closely mirrored previously published in vivo glycan profiles, with LacdiNAc rising, core xylosylated structures disappearing and core-fucosylated glycans declining, validating the culture system as a model for intra-mammalian development.

Yet the rapid recovery of the glycan profile after treatment withdrawal also exposes a limitation: chemical α-mannosidase inhibition is not suited for long-term co-culture experiments or in vivo studies, because the parasite simply restores its normal glycans once the compound is gone. The authors therefore point toward more durable glycoengineering approaches, including RNA interference to knock down glycosylation enzymes in a species-specific manner, and CRISPR-Cas9 genome editing, which has already been applied to schistosomula, adult worms and eggs, to create parasites with permanently altered glycan profiles. Such tools would also allow selective manipulation of individual motifs or of other glycan classes, such as O-glycans and glycosphingolipids, which broad-spectrum inhibitors cannot achieve.

For a field urgently seeking prophylactic vaccines and drugs against a parasite that evades and modulates host immunity with remarkable sophistication, glyco-remodelled live schistosomes now provide an attractive experimental platform. By tuning the parasite’s sugar coat and watching development falter or recover, researchers can begin to assign functional roles to individual glycans in larval survival, immune recognition and host interaction, exposing tentative glycan-based targets for the next generation of schistosomiasis control strategies and, potentially, for other neglected tropical diseases at large.

Subject of Research: Chemical inhibition of α-mannosidase in S. mansoni schistosomula leads to reshaped N-glycosylation associated with developmental alterations

Article Title: Chemical inhibition of α-mannosidase in S. mansoni schistosomula leads to reshaped N-glycosylation associated with developmental alterations

Article References: Kuhlemaijer, E. B., Veldhuizen, T., Hoekstra, Q. C. A., Umbach, J. A., Niezen, M. J., Forde-Thomas, J. E., Rinaldi, G., Hoffmann, K. F., van Diepen, A., & Hokke, C. H. (2026). Chemical inhibition of α-mannosidase in S. mansoni schistosomula leads to reshaped N-glycosylation associated with developmental alterations. Frontiers in Parasitology, 5, Article 1930872. https://doi.org/10.3389/fpara.2026.1930872

Image Credits: AI Generated

DOI: 10.3389/fpara.2026.1930872

Keywords: Chemical, inhibition, mannosidase, mansoni, schistosomula, leads, reshaped, N-glycosylation, associated, developmental, alterations, scientific research