Plasmodium falciparum antigenic variation: relationships between widespread endothelial activation, parasite PfEMP1 expression and severe malaria. 2014

Abdirahman I Abdi, and Gregory Fegan, and Michelle Muthui, and Esther Kiragu, and Jennifer N Musyoki, and Michael Opiyo, and Kevin Marsh, and George M Warimwe, and Peter C Bull
KEMRI-Wellcome Trust Research Programme, P,O, Box 230-80108, Kilifi, Kenya. aabdi@kemri-wellcome.org.

BACKGROUND Plasmodium falciparum erythrocyte membrane protein 1(PfEMP1) is a family of variant surface antigens (VSA) that mediate the adhesion of parasite infected erythrocytes to capillary endothelial cells within host tissues. Opinion is divided over the role of PfEMP1 in the widespread endothelial activation associated with severe malaria. In a previous study we found evidence for differential associations between defined VSA subsets and specific syndromes of severe malaria: group A-like PfEMP1 expression and the "rosetting" phenotype were associated with impaired consciousness and respiratory distress, respectively. This study explores the involvement of widespread endothelial activation in these associations. METHODS We used plasma angiopoietin-2 as a marker of widespread endothelial activation. Using logistic regression analysis, we explored the relationships between plasma angiopoietin-2 levels, parasite VSA expression and the two syndromes of severe malaria, impaired consciousness and respiratory distress. RESULTS Plasma angiopoietin-2 was associated with both syndromes. The rosetting phenotype did not show an independent association with respiratory distress when adjusted for angiopoietin-2, consistent with a single pathogenic mechanism involving widespread endothelial activation. In contrast, group A-like PfEMP1 expression and angiopoietin-2 maintained independent associations with impaired consciousness when adjusted for each other. CONCLUSIONS The results are consistent with multiple pathogenic mechanisms leading to severe malaria and heterogeneity in the pathophysiology of impaired consciousness. The observed association between group A-like PfEMP1 and impaired consciousness does not appear to involve widespread endothelial activation.

UI MeSH Term Description Entries
D007630 Kenya A republic in eastern Africa, south of ETHIOPIA, west of SOMALIA with TANZANIA to its south, and coastline on the Indian Ocean. Its capital is Nairobi. Republic of Kenya
D010963 Plasmodium falciparum A species of protozoa that is the causal agent of falciparum malaria (MALARIA, FALCIPARUM). It is most prevalent in the tropics and subtropics. Plasmodium falciparums,falciparums, Plasmodium
D012128 Respiratory Distress Syndrome A syndrome characterized by progressive life-threatening RESPIRATORY INSUFFICIENCY in the absence of known LUNG DISEASES, usually following a systemic insult such as surgery or major TRAUMA. ARDS, Human,Acute Respiratory Distress Syndrome,Adult Respiratory Distress Syndrome,Pediatric Respiratory Distress Syndrome,Respiratory Distress Syndrome, Acute,Respiratory Distress Syndrome, Adult,Respiratory Distress Syndrome, Pediatric,Shock Lung,Distress Syndrome, Respiratory,Distress Syndromes, Respiratory,Human ARDS,Lung, Shock,Respiratory Distress Syndromes,Syndrome, Respiratory Distress
D002648 Child A person 6 to 12 years of age. An individual 2 to 5 years old is CHILD, PRESCHOOL. Children
D004727 Endothelium A layer of epithelium that lines the heart, blood vessels (ENDOTHELIUM, VASCULAR), lymph vessels (ENDOTHELIUM, LYMPHATIC), and the serous cavities of the body. Endotheliums
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000940 Antigenic Variation Change in the surface ANTIGEN of a microorganism. There are two different types. One is a phenomenon, especially associated with INFLUENZA VIRUSES, where they undergo spontaneous variation both as slow antigenic drift and sudden emergence of new strains (antigenic shift). The second type is when certain PARASITES, especially trypanosomes, PLASMODIUM, and BORRELIA, survive the immune response of the host by changing the surface coat (antigen switching). (From Herbert et al., The Dictionary of Immunology, 4th ed) Antigen Switching,Antigenic Diversity,Variation, Antigenic,Antigen Variation,Antigenic Switching,Antigenic Variability,Switching, Antigenic,Diversity, Antigenic,Switching, Antigen,Variability, Antigenic,Variation, Antigen
D012397 Rosette Formation The in vitro formation of clusters consisting of a cell (usually a lymphocyte) surrounded by antigenic cells or antigen-bearing particles (usually erythrocytes, which may or may not be coated with antibody or antibody and complement). The rosette-forming cell may be an antibody-forming cell, a memory cell, a T-cell, a cell bearing surface cytophilic antibodies, or a monocyte possessing Fc receptors. Rosette formation can be used to identify specific populations of these cells. Immunocytoadherence,Formation, Rosette,Formations, Rosette,Immunocytoadherences,Rosette Formations
D015800 Protozoan Proteins Proteins found in any species of protozoan. Proteins, Protozoan
D016778 Malaria, Falciparum Malaria caused by PLASMODIUM FALCIPARUM. This is the severest form of malaria and is associated with the highest levels of parasites in the blood. This disease is characterized by irregularly recurring febrile paroxysms that in extreme cases occur with acute cerebral, renal, or gastrointestinal manifestations. Plasmodium falciparum Malaria,Malaria, Plasmodium falciparum

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