Novel semi-synthetic carbohydrates as potential therapeutics for severe malaria

Lead Research Organisation: University of Liverpool
Department Name: Sch of Biological Sciences

Abstract

Severe malaria is a disease that kills millions every year, especially in developing nations, resulting in widespread suffering and economic damage. Severe malaria is caused by both the aggregation of red blood cells infected by the parasite into rosettes and via cytoadherence, the attachment of red blood cells to the cells of the host, lining the blood vessels. Rosette formation and cytoadherence both prevent proper transport of oxygen by the red blood cells around the capilaries of the brain and causes blockages, damaging the brain, and this is often fatal. This project will identify the simplest fragments, from a novel semi-synthetic library of negatively charged carbohydrates, that are able to disrupt rosetting and cytoadherence while minimising/eliminating any potential side-effects. This will provide information concerning the minimum structures required, allowing cheap, chemical synthesis of the molecules to be undertaken. This project will ultimatley lead to the development of new pharmaceutical agents, which are urgently needed, as resistance emerges to the drugs being administered currently.

Technical Summary

Malaria, caused by Plasmodium species, affects one third of the world?s population with over 300 million infections resulting in 2 million deaths annually. Severe malaria, caused by P. falciparum, is the most serious complication of the disease resulting in widespread suffering and economic damage, especially in developing nations. Severe malaria severity correlates with the extent of venule occlusion (by rosetting, auto-aglutination and cytoadherance) resulting in hypoxia and coma. Cell-cell adhesions are facilitated by interactions between parasite expressed proteins and host carbohydrates (hyaluronic acid, chondroitin sulfate, heparan sulfate) and proteins (CD-36, E-selectin, PECAM-1, ICAM-1, VCAM-1 and thrombospondin) while the rosetting process is mediated principally by the parasite expressed protein, P. falciparum erythrocyte membrane protein-1 (PfEMP-1) through attachment to host cell-surface carbohydrates. It has been shown that both naturally occuring and chemically modified carbohydrates are capable of disrupting malaria rosettes and/or cytoadherance, but the structural details of these interactions, and the carbohydrates themselves, remain poorly defined. This project will create an arsenal of semi-synthetic, structurally diverse polysaccharides which will faciitate the generation of a series of size-defined, structurally diverse oligosaccharides from which the simplest structures (i.e. smallest and least charged) capable of inhibiting rosetting and cytoadherence will be selected, purified and their detailed structures defined by a combination of recently developed sequencing techniques (e.g. ES-MS and NMR). As a precaution, successful inhibitors will also be screened for potential side-effects, including the formation of immunogenic platelet factor-IV complexes and activities with the blood clotting cascade (anti-factor Xa, antithrombin and factor II) activities, which can be highly attenuated (down to 0.5 %) with simple chemical modifications. The structural information will not only provide detailed data concerning the nature of the interacting species, leading to improved mechanistic understanding, but will also provide the structurally simplest targets for future chemical synthesis, the first step to producing new pharmaceutical agents.
 
Description The interaction of the SARS CoV-2 spike protein receptor binding domain with heparin and its derivatives.
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact Our study of the interaction of the SARS CoV-2 spike protein receptor binding domain with heparin and its derivatives, both as models of the cell surface ligand, heparan sulfate, and as potential therapeutics, underpinned the international CHARTER (Can nebulised heparin reduce time to extubation in SARS-CoV-2?) clinical trial. Our work was published originally in March 2020 on the BioRiv server [1], then in the peer-reviewed journal, Thrombosis and Haemostasis [2], and underpins both the present Wellcome Trust application as well as a recent application to NIHR. The protocol [3], which was adopted for CHARTER, also involved several of the applicants as well as an international group of collaborating clinicians. Now, the findings of the CHARLI (Can heparin administration reduce lung injury?) clinical trial, conducted by the same international group of collaborators, have been published in Lancet Respiratory Medicine ('Nebulised heparin for patients with or at risk of acute respiratory distress syndrome; a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.' by B Dixon et al., [4]. The results from CHARLI confirm the safety of nebulised heparin for the treatment of non-viral ARDS, indicating a reduction in the extent of lung damage, while enabling an earlier return home than patient control groups. Since the publication by Dixon et al., there has been enthusiasm among the scientific community to test nebulised heparin in a more homogenous population than was used in the initial study, since ARDS can take many forms; a view echoed in a recent publication in The Lancet Respiratory Medicine [5]. Very recently, a study in the BMJ [6] has shown that early prophylaxis with heparin decreases the 30-day mortality in a cohort of COVID-19 patients who had no increased risk of serious bleeding events, a risk factor for the use of conventional heparin. These findings provide further confidence in the possible application of better-optimised compounds derived from crude heparin, a source of greater structural and bioactivity diversity than the conventional pharmaceutical heparin employed in the CHARLI clinical trial, and ones from which bleeding complications can be essentially eliminated. [1] https://doi.org/10.1101/2020.02.29.971093 [2] Thromb Haemost 2020; 120(12): 1700-1715 DOI: 10.1055/s-0040-1721319 [3] https://doi.org/10.1101/2020.04.28.20082552 [4] DOI: 10.1016/S2213-2600(20)30470-7 [5] https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30513-0/fulltext [6] https://www.bmj.com/content/372/bmj.n311
 
Description project grant
Amount £50,000 (GBP)
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2010 
End 09/2011
 
Title sulfated polysaccharide library 
Description a family of sulfated polysaccharides with several interesting biological activities in addition to those of the grant also developed several assays 
Type Of Material Technology assay or reagent 
Year Produced 2008 
Provided To Others? Yes  
Impact assays measuring inhibition of viral attachment are underway 
 
Description Collaboration in infectivity studies with University of Keele 
Organisation Keele University
Department School of Life Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution Provision of sulfated inhibitors of parasite invasion
Collaborator Contribution Assays of invasion
Impact Publication in preparation
Start Year 2009
 
Description Cytoadherence and inhibition with polysaccharides 
Organisation Liverpool School of Tropical Medicine
Country United Kingdom 
Sector Academic/University 
PI Contribution Provide polysaccharides to inhibit and reverse cytoadherence
Collaborator Contribution Provided assay for cytoadherence
Impact paper in preparation: Reversal and Inhibition of P.falciparum cytoadherence by chemically modified polysaccharide analogues of glycosaminoglycans.M. Khairul, M.A.Skidmore, A.C.Craig and E.A.Yates (in preparation)
Start Year 2009
 
Description inhibitors of viral attachment 
Organisation San Raffaele Hospital
Department Virology
Country Italy 
Sector Hospitals 
PI Contribution Provided inhibitors of viral attachment and invasion
Collaborator Contribution provided assays of viral entry into cells
Impact Inhibition of influenza H1N1 viral entry into cells. A. Ruzentska, M.A.Skidmore, E.A.Yates and E.Vicenzi
Start Year 2008
 
Description ICOPA Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact 100 + audience with questions and enquiries


Useful exchange of know-how and materials.

ICOPA XII, Melbourne Australia, 15/08/12-20/08/10 (www.icopaxii.org)
Year(s) Of Engagement Activity 2010
 
Description Invited Talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Poster Presentation
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact 6th International Conference on proteoglycans, Aix-les-Bains, France. "GAG analogues disrupt P.falciparum malaria" 13th-17th September 2009. (http://pg2009-fr/.Aix-les-Bains)

new collaborative links
Year(s) Of Engagement Activity 2009
 
Description Invited talk to University of New South Wales 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Audience questions answered and potential collaborative links formed

University of New South Wales, Australia (2010) "GAGs, Chemically Modified derivatives and Semi-synthetic analogues: new technologies paving the way towards glycotherapies". Interest from potential new collaborators.
Year(s) Of Engagement Activity 2010
 
Description Outreach presentation to public at 68th Annual Meeting of SBPC (in Porto Seguro, Bahia, Brazil, 2016) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Engaged with broad general public in Brazil over 1 week, demonstrating structures of biological materials using simple experiments and outlining infection processes in tropical diseases using easy to follow diagrams.
Year(s) Of Engagement Activity 2016
URL http://sbpcacervodigital.org.br/handle/20.500.11832/96
 
Description RSC invited talk 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Invited Talk. Royal Society of Chemistry Autumn Meeting of the Carbohydrate Group, Liverpool, 13th-17th september 2011. (www.rsc.org/ConferncesAndEvents)

New experimental design formed following discussions, which has been conducted by undergraduate research students.
Year(s) Of Engagement Activity 2011
 
Description Talk to visiting medical students from Saudi Arabia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Paper Presentation
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Medical Students from Saudi Arabia were given a talk about potential treatments for malaria based on carbohydrates.

Several expressed interest in studying in UK
Year(s) Of Engagement Activity 2009
 
Description invited talk keele 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact NEMO EU-Marie Curie Actions, ITN Network-, University of Keele, 13-17/09/12. "Prebiotics and probiotics in medicine, veterinary sciences and aquaculture: the future"
(www.keele-conferencemanagement.com/nemo.2012)

Collaboration with Brazilian research group initiated
Year(s) Of Engagement Activity 2012
URL http://www.keele-conferencemanagement.com/nemo.2012