Award details

Immune evasion by schistosomes: a proteomic analysis of the tegument surface

Reference	BB/C516328/1
Principal Investigator / Supervisor	Professor Alan Wilson
Co-Investigators / Co-Supervisors	Professor Jane Thomas-Oates
Institution	University of York
Department	Biology
Funding type	Research
Value (£)	253,512
Status	Completed
Type	Research Grant
Start date	06/07/2005
End date	05/05/2009
Duration	46 months

Abstract

Schistosomes are remarkable parasites that can live in the bloodstream for many years provoking an immune response but avoiding its consequences, and so they must possess an efficient immune evasion mechanism. The worms are covered by a syncytial cytoplasmic layer, the tegument, bounded by a normal plasma membrane. The underlying cell bodies manufacture multilaminate vesicles that traffic to the tegument cytoplasm and discharge their contents into the base of tegumental pits. The released material then flows over the surface to provide the protective bilayer, which we termed a membranocalyx. Understanding how this secreted bilayer prevents immune attach is important in the fight against schistosome infections in animals and humans. It may also carry a more universal message about the strategies that pathogens in general use to establish chronic infections. Methods were developed more than 20 years ago to remove and enrich the surface layers of the tegument, but the techniques of the day precluded detailed identification of its components. The proposed project is both novel in its newly developed proteomic techniques to characterise the molecular architecture of the surface layers, and timely in that it is made possible by the sequencing of the schistosoma mansoni genome, currently being assembled. The wealth of DNA information now available makes it possible to link virtually any schistosome protein to its encoding gene sequence. The first task will be to use tandem mass spectrometry (MS), predominantly MALDI ToF-ToF MS, to create an inventory of the proteins present in the isolated surface layers and to classify them according to biological function; this should reveal the range and relative importance of biological processes occurring at this host-parasite interface. We shall incubate live worms with a biotinylation reagent that links to exposed proteins to discover which surface constituents are accessible from the exterior. (The impermeant probe reacts with certain membrane proteins but does not reach the underlying cytoskeleton). Isolation of the membranocalyx is a central and crucial goal of the project. Any proteins present in the layer will be identified by tandem MS. The lipids and glycolipids (including those of host erythrocyte origin), which represent the bulk of the material, will be characterised by electrospray ionisation MS. The final aspect of the project is to integrate all the information obtained into a 3D conceptual model of the tegument surface, placing the constituents in their correct relative locations. The first step, in a continuing activity throughout the project, will be to model each identified protein using standard bioinformatics tools, and predict likely antigenic epitopes. Corresponding peptides will then be synthesised and used to raise antibodies for immunolocalisation by confocal microscopy. Our aim is a clear understanding of the properties of the membranocalyx and the plasma membrane that it protects. The work may also reveal if any proteins are potentially accessible to immune effector mechanisms.

Summary

unavailable

Committee	Closed Committee - Animal Sciences (AS)
Research Topics	Animal Health, Immunology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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