A novel domain cassette identifies Plasmodium falciparum PfEMP1 proteins binding ICAM-1 and is a target of cross-reactive, adhesion-inhibitory antibodies

J Immunol. 2013 Jan 1;190(1):240-9. doi: 10.4049/jimmunol.1202578. Epub 2012 Dec 3.

Abstract

Cerebral Plasmodium falciparum malaria is characterized by adhesion of infected erythrocytes (IEs) to the cerebral microvasculature. This has been linked to parasites expressing the structurally related group A subset of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family of IE adhesion ligands and to IEs with affinity for ICAM-1. However, recent evidence has cast doubt on both these associations, tempering hopes of the feasibility of developing a vaccine based on ICAM-1-binding PfEMP1. In this study, we report the identification of a domain cassette (DC) present in group A var genes from six genetically distinct P. falciparum parasites. The three domains in the cassette, which we call DC4, had a high level of sequence identity and cluster together phylogenetically. Erythrocytes infected by these parasites and selected in vitro for expression of DC4 adhered specifically to ICAM-1. The ICAM-1-binding capacity of DC4 was mapped to the C-terminal third of its Duffy-binding-like β3 domain. DC4 was the target of broadly cross-reactive and adhesion-inhibitory IgG Abs, and levels of DC4-specific and adhesion-inhibitory IgG increased with age among P. falciparum-exposed children. Our study challenges earlier conclusions that group A PfEMP1 proteins are not central to ICAM-1-specific IE adhesion and support the feasibility of developing a vaccine preventing cerebral malaria by inhibiting cerebral IE sequestration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Blocking / genetics
  • Antibodies, Blocking / metabolism*
  • Antigens, Protozoan / classification
  • Antigens, Protozoan / genetics
  • Antigens, Protozoan / metabolism*
  • Binding Sites, Antibody / genetics
  • Cell Adhesion / genetics
  • Cell Adhesion / immunology
  • Conserved Sequence / genetics
  • Conserved Sequence / immunology
  • Cross Reactions / immunology
  • Erythrocyte Membrane / genetics
  • Erythrocyte Membrane / immunology
  • Erythrocyte Membrane / metabolism*
  • Genomics / methods
  • HEK293 Cells
  • Humans
  • Intercellular Adhesion Molecule-1 / genetics
  • Intercellular Adhesion Molecule-1 / immunology
  • Intercellular Adhesion Molecule-1 / metabolism*
  • Mutagenesis, Insertional / genetics
  • Mutagenesis, Insertional / immunology*
  • Plasmodium falciparum / genetics
  • Plasmodium falciparum / immunology*
  • Protein Binding / genetics
  • Protein Binding / immunology
  • Protein Structure, Tertiary / genetics
  • Protozoan Proteins / classification
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*
  • Rats

Substances

  • Antibodies, Blocking
  • Antigens, Protozoan
  • ICAM1 protein, human
  • Protozoan Proteins
  • erythrocyte membrane protein 1, Plasmodium falciparum
  • Intercellular Adhesion Molecule-1