Differential PfEMP1 expression is associated with cerebral malaria pathology

Area of Science:

• Malariology
• Immunology
• Genetics

Background:

• Plasmodium falciparum uniquely sequesters in post-capillary venules.
• P. falciparum erythrocyte membrane protein 1 (PfEMP1) mediates cytoadherence and is divided into groups A-C.
• Cerebral malaria (CM) involves parasite sequestration in vital organs.

Purpose of the Study:

• To investigate the genetic background and PfEMP1 group expression in sequestered P. falciparum populations.
• To compare parasite expression patterns across different cerebral malaria pathologies (CM1, CM2) and parasitaemic controls (PC).
• To analyze sequestered parasite populations directly from post-mortem brain, heart, and gut tissues.

Main Methods:

• Post-mortem tissue collection from twenty paediatric patients with CM1, CM2, and PC.
• Quantitative PCR to assess var gene group expression.
• Cloning and sequencing of var transcript tags to identify dominant expressed sequences.

Main Results:

• Quantitative PCR showed Group A var genes upregulated in CM2 and PC cases across organs.
• CM1 infections exhibited high Group B var expression, correlating with sequestration but not vascular pathology.
• Cloning and sequencing revealed low Group A-like var expression, with dominant expression of 1-2 sequences per sample.
• 23% of var tags were found in multiple genetically distinct patients, with two tags appearing in up to seven hosts.

Conclusions:

• Parasite sequestration and PfEMP1 expression vary significantly with cerebral malaria pathology.
• Specific var gene groups (A and B) are differentially expressed depending on the clinical presentation of cerebral malaria.
• A subset of PfEMP1 variants may be broadly expressed across genetically distinct P. falciparum infections, suggesting potential roles in severe malaria pathogenesis.