Authors

E Kuhlemaijer²; A Van Diepen²; T Veldhuizen²; B Hulme¹; J Forde-Thomas¹; G Rinaldi¹; K Hoffmann¹; C Hokke²;  ¹ Aberystwyth University, UK;  ² Leiden University Medical Centre, Netherlands

Discussion

Schistosomiasis is a neglected tropical disease (NTD) caused by blood flukes of the genus Schistosoma. Worldwide, at least 250 million people are infected with Schistosoma parasites and an estimated 779 million people are at risk of infection. Although the infection can be treated with praziquantel (PZQ), this drug is ineffective against juvenile stages and does not prevent reinfection. Hence, there is an urgent need for prophylactic vaccines and to identify new drugs that target different life-stages of the parasite.

In order to develop new vaccines and drugs, understanding of the intricate parasite-host interaction is crucial. The parasite is known to modulate the host’s immune response by expressing a variety of antigens and releasing specific molecules. Several of the parasite-derived molecules are glycoconjugates consisting of glycans covalently linked to proteins or lipids. Previously, it has been shown that the glycan component of these glycoproteins and glycolipids may be crucial in provoking a polarised host immune response. Additionally, glycans play essential roles in diverse eukaryotic cell processes such as protein folding and intercellular communication. Taken together, glycans could be pivotal in shaping parasite-host interactions and parasite development.

Our research aims to develop glycoengineered living adult Schistosoma mansoni worms and subsequently employ these to study how different glycans might contribute to the mammalian immune responses against parasite-derived molecules. Glycoengineered worms were generated in ex vivo cultures using kifunensine and swainsonine, chemical compounds that inhibit specific α-mannosidases involved in the N-glycosylation pathway. We show that the compounds alter the N-glycosylation profile from complex type glycans to hybrid and oligomannosidic N-glycan forms, as measured by MALDI-TOF MS. Notably, the shift in N-glycan forms appeared to gradually increase over time. Additionally, we used phenotypic analyses to assess worm motility and morphology in glycoengineered worms. WHO-TDR motility scoring confirmed that these worms exhibited normal movement when compared to untreated worms. Furthermore, we stained glycoengineered worms with live dyes selective for cell nuclei, plasma membranes and F-actin to study worm morphology. Confocal fluorescence microscopy revealed no apparent changes in the oral and ventral sucker, oesophagus, testes or ovary and tegument.

Overall, these results show that the N-glycosylation profile of live S. mansoni worms can be altered ex vivo, without apparent changes in worm motility or morphology. Hereupon, glycosylated extracts of the glycoengineered worms could be used to stimulate immune cells and study the induced immune response. Hence, we conclude that glycoengineered worms are a promising tool to further elucidate the mammalian immune response against worm-derived N-glycans.