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Plasmodium falciparum EPCR-binding PfEMP1 expression increases with malaria disease severity and is elevated in
Estela Shabani1,2, Benjamin Hanisch3, Robert O Opoka4
1Ryan White Center for Pediatric Infectious Diseases and Global Health, Indiana University, 1044 W Walnut St R4 402D, Indianapolis, Indiana, USA.
Background:
Expression of group A and the A-like subset of group B Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is associated with severe malaria (SM). The diversity of var sequences combined with the challenges of distinct classification of patient pathologies has made studying the role of distinct PfEMP1 variants on malaria disease severity challenging. The application of retinopathy in the recent years has provided a further method to clinically evaluate children with cerebral malaria (CM). The question of whether children with clinical CM but no retinopathy represent a completely different disease process or a subgroup within the spectrum of CM remains an important question in malaria. In the current study, we use newly designed primer sets with the best coverage to date in a large cohort of children with SM to determine the role of var genes in malaria disease severity and especially CM as discriminated by retinopathy.
Methods:
We performed qRT-PCR targeting the different subsets of these var genes on samples from Ugandan children with CM (n = 98, of whom 50 had malarial retinopathy [RP] and 47 did not [RN]), severe malarial anemia (SMA, n = 47), and asymptomatic parasitemia (AP, n = 14). The primers used in this study were designed based on var sequences from 226 Illumina whole genome sequenced P. falciparum field isolates.
Results:
Increasing severity of illness was associated with increasing levels of endothelial protein C receptor (EPCR)-binding PfEMP1. EPCR-binding PfEMP1 transcript levels were highest in children with combined CM and SMA and then decreased by level of disease severity: RP CM > RN CM > SMA > AP.
Conclusions:
The study findings indicate that PfEMP1 binding to EPCR is important in the pathogenesis of SM, including RN CM, and suggest that increased expression of EPCR-binding PfEMP1 is associated with progressively more severe disease. Agents that block EPCR-binding of PfEMP1 could provide novel interventions to prevent or decrease disease severity in malaria.
Insights
Severe malaria is linked to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variants. Higher levels of EPCR-binding PfEMP1 correlate with increased disease severity, suggesting new therapeutic targets for malaria.
Area of Science:
- Malariology
- Immunology
- Genetics
Background:
- Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variants, particularly group A and A-like B, are implicated in severe malaria (SM).
- Studying distinct PfEMP1 roles in malaria severity is challenging due to var gene diversity and complex patient pathology classification.
- Malarial retinopathy aids clinical evaluation of cerebral malaria (CM), but distinguishing CM with and without retinopathy requires further investigation.
Purpose of the Study:
- To investigate the role of var genes in malaria disease severity, specifically cerebral malaria (CM) differentiated by retinopathy.
- To determine the association between Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) expression and malaria severity in a large cohort of children.
Main Methods:
- Quantitative reverse transcription PCR (qRT-PCR) was used to target different subsets of var genes.
- Samples were analyzed from Ugandan children diagnosed with CM (with and without retinopathy), severe malarial anemia (SMA), and asymptomatic parasitemia (AP).
- Newly designed primer sets, based on var sequences from 226 P. falciparum field isolates, were utilized for comprehensive coverage.
Main Results:
- Increasing severity of illness correlated with higher levels of endothelial protein C receptor (EPCR)-binding PfEMP1.
- EPCR-binding PfEMP1 transcript levels were highest in children with combined CM and SMA.
- Transcript levels decreased with decreasing disease severity: retinopathy-positive CM > retinopathy-negative CM > SMA > asymptomatic parasitemia.
Conclusions:
- PfEMP1 binding to EPCR is crucial in the pathogenesis of severe malaria, including retinopathy-negative CM.
- Increased expression of EPCR-binding PfEMP1 is associated with progressively severe malaria.
- Blocking EPCR-binding of PfEMP1 presents a potential novel therapeutic strategy for malaria.