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Role of sequestration-induced loss of protein C receptors in coagulation and inflammation in cerebral malaria
Poster Abstracts
Role of sequestration-induced loss of protein C receptors in coagulation and inflammation in cerebral malaria Christopher Moxon, Samuel Wassmer, Danny Milner Jr, Ngawina Chisala, Terrie Taylor, Karl Seydel, Malcolm Molyneux, Charles Esmon, Colin Downey, Cheng-Hock Toh, Alister Craig, Robert Heyderman
Abstract Background Cerebral malaria is a major cause of mortality in African children but pathogenesis remains incompletely understood. Although brain microhaemorrhages are suggestive of a clotting disorder, whether they are important in pathogenesis is debated. We hypothesised that localised cerebral microvascular thrombosis in cerebral malaria is caused by a decreased expression of the anticoagulant and protective receptors thrombomodulin (TM) and endothelial protein C receptor (EPCR) and that low constitutive expression of these regulatory molecules in the brain makes it particularly vulnerable. Methods Histological examination for fibrin and EPCR was performed on archival post-mortem brain tissue from children who died with cerebral malaria and non-malarial encephalopathy. The expression of endothelial receptors in subcutaneous tissue needle biopsy samples were measured ex vivo by a novel flow cytometry technique in children with cerebral malaria and in healthy controls. Coagulation markers were measured in plasma from children with cerebral malaria, non-malarial coma, mild non-malarial febrile illness, uncomplicated malaria, and healthy controls. Findings Microvascular fibrin deposition was more common in brain tissue samples from ten children with fatal cerebral malaria than in six non-malarial controls (odds ratio [OR] 19·96, 95% CI 7·05–56·55; p<0·001) and was associated with malaria-infected erythrocyte (IE) sequestration (r=0·60, p<0·001). IE sequestration was also associated with loss of EPCR staining (r=20·57, p<0·001) which was also lower in cerebral malaria than in controls (OR 0·048, 95% CI 0·012–0·20; p<0·001). IE-associated loss of EPCR and thrombomodulin was shown in vivo in subcutaneous tissue samples from 17 children with cerebral malaria and 20 healthy controls. In peripheral blood, coagulation was activated in children with cerebral malaria, with detection of raised plasma thrombin-anti-thrombin (TAT) complexes (n=67, geometric mean 26·7 μg/mL, 95% CI 20·5–34·8) compared with children with uncomplicated malaria (n=21, 10·6, 7·6–14·8; p<0·001) and aparasitaemic febrile illness (n=30, 12·3, 7·4–20·3; p<0·01). In children with cerebral malaria, higher admission TAT concentrations were associated with fatal outcome (p=0·02). However, prothrombin fragment-to-activated protein C ratio and functional coagulation indices were similar between cerebral malaria and uncomplicated malaria. Interpretation Our data show that activation of coagulation occurs in cerebral malaria. Although this activation is compensated peripherally, there is a local loss of endothelial anticoagulant receptors and thrombosis at sites of IE sequestration in the microvasculature. This major endothelial homoeostatic pathway defect principally affects the brain, where constitutive expression of thrombomodulin and EPCR is low. Funding Wellcome Trust. Contributors CM designed and did the research, analysed the data, and wrote the abstract. SW designed the research and wrote the abstract. DM designed the research and provided technical advice. TT and MM designed the clinical study. TT, MM, and KS supervised study conduct. NC did the research; C-HT, CD, and CE provided technical advice. RH and AC designed the research and wrote the abstract. All authors contributed to critical revision of the abstract. Conflicts of interest We declare that we have no conflicts of interest.
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Published Online February 26, 2014 Poster 49 Institute of Translational Medicine, University of Liverpool, Liverpool, UK (C Moxon MBBS); Malawi-Liverpool-Wellcome Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi (C Moxon, N Chisala BSc, M Molyneux MBBS, Prof R Heyderman MBBS); Liverpool School of Tropical Medicine, Liverpool, UK (C Moxon, Prof A Craig PhD, Prof R Heyderman); New York University School of Medicine, New York, NY, USA (S Wassmer PhD); Brigham and Women's Hospital, Boston, MA, USA (D Milner Jr MD); College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA (Prof T Taylor DO, K Seydel MD); Oklahoma Medical Research Foundation, Oklahoma City, OK, USA (Prof C Esmon PhD); Howard Hughes Medical Institute, Oklahoma City, OK, USA (Prof C Esmon); Institute of Infection and Global Health, Liverpool University, Liverpool, UK (C Downey BSc, Prof C-H Toh MBBS); and Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi (Prof T Taylor, K Seydel) Correspondence to: Dr Christopher Moxon, Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK [email protected]
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Role of sequestration-induced loss of protein C receptors in coagulation and inflammation in cerebral malaria Christopher Moxon, Samuel Wassmer, Danny Milner Jr, Ngawina Chisala, Terrie Taylor, Karl Seydel, Malcolm Molyneux, Charles Esmon, Colin Downey, Cheng-Hock Toh, Alister Craig, Robert Heyderman
Abstract Background Cerebral malaria is a major cause of mortality in African children but pathogenesis remains incompletely understood. Although brain microhaemorrhages are suggestive of a clotting disorder, whether they are important in pathogenesis is debated. We hypothesised that localised cerebral microvascular thrombosis in cerebral malaria is caused by a decreased expression of the anticoagulant and protective receptors thrombomodulin (TM) and endothelial protein C receptor (EPCR) and that low constitutive expression of these regulatory molecules in the brain makes it particularly vulnerable. Methods Histological examination for fibrin and EPCR was performed on archival post-mortem brain tissue from children who died with cerebral malaria and non-malarial encephalopathy. The expression of endothelial receptors in subcutaneous tissue needle biopsy samples were measured ex vivo by a novel flow cytometry technique in children with cerebral malaria and in healthy controls. Coagulation markers were measured in plasma from children with cerebral malaria, non-malarial coma, mild non-malarial febrile illness, uncomplicated malaria, and healthy controls. Findings Microvascular fibrin deposition was more common in brain tissue samples from ten children with fatal cerebral malaria than in six non-malarial controls (odds ratio [OR] 19·96, 95% CI 7·05–56·55; p<0·001) and was associated with malaria-infected erythrocyte (IE) sequestration (r=0·60, p<0·001). IE sequestration was also associated with loss of EPCR staining (r=20·57, p<0·001) which was also lower in cerebral malaria than in controls (OR 0·048, 95% CI 0·012–0·20; p<0·001). IE-associated loss of EPCR and thrombomodulin was shown in vivo in subcutaneous tissue samples from 17 children with cerebral malaria and 20 healthy controls. In peripheral blood, coagulation was activated in children with cerebral malaria, with detection of raised plasma thrombin-anti-thrombin (TAT) complexes (n=67, geometric mean 26·7 μg/mL, 95% CI 20·5–34·8) compared with children with uncomplicated malaria (n=21, 10·6, 7·6–14·8; p<0·001) and aparasitaemic febrile illness (n=30, 12·3, 7·4–20·3; p<0·01). In children with cerebral malaria, higher admission TAT concentrations were associated with fatal outcome (p=0·02). However, prothrombin fragment-to-activated protein C ratio and functional coagulation indices were similar between cerebral malaria and uncomplicated malaria. Interpretation Our data show that activation of coagulation occurs in cerebral malaria. Although this activation is compensated peripherally, there is a local loss of endothelial anticoagulant receptors and thrombosis at sites of IE sequestration in the microvasculature. This major endothelial homoeostatic pathway defect principally affects the brain, where constitutive expression of thrombomodulin and EPCR is low. Funding Wellcome Trust. Contributors CM designed and did the research, analysed the data, and wrote the abstract. SW designed the research and wrote the abstract. DM designed the research and provided technical advice. TT and MM designed the clinical study. TT, MM, and KS supervised study conduct. NC did the research; C-HT, CD, and CE provided technical advice. RH and AC designed the research and wrote the abstract. All authors contributed to critical revision of the abstract. Conflicts of interest We declare that we have no conflicts of interest.
www.thelancet.com
Published Online February 26, 2014 Poster 49 Institute of Translational Medicine, University of Liverpool, Liverpool, UK (C Moxon MBBS); Malawi-Liverpool-Wellcome Clinical Research Programme, University of Malawi College of Medicine, Blantyre, Malawi (C Moxon, N Chisala BSc, M Molyneux MBBS, Prof R Heyderman MBBS); Liverpool School of Tropical Medicine, Liverpool, UK (C Moxon, Prof A Craig PhD, Prof R Heyderman); New York University School of Medicine, New York, NY, USA (S Wassmer PhD); Brigham and Women's Hospital, Boston, MA, USA (D Milner Jr MD); College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA (Prof T Taylor DO, K Seydel MD); Oklahoma Medical Research Foundation, Oklahoma City, OK, USA (Prof C Esmon PhD); Howard Hughes Medical Institute, Oklahoma City, OK, USA (Prof C Esmon); Institute of Infection and Global Health, Liverpool University, Liverpool, UK (C Downey BSc, Prof C-H Toh MBBS); and Blantyre Malaria Project, University of Malawi College of Medicine, Blantyre, Malawi (Prof T Taylor, K Seydel) Correspondence to: Dr Christopher Moxon, Department of Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool L69 3BX, UK [email protected]
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