Reticulocyte and erythrocyte binding-like proteins function cooperatively in invasion of human erythrocytes by malaria parasites

Infect Immun. 2011 Mar;79(3):1107-17. doi: 10.1128/IAI.01021-10. Epub 2010 Dec 13.

Abstract

Plasmodium falciparum causes the most severe form of malaria in humans and invades erythrocytes using multiple ligand-receptor interactions. Two important protein families involved in erythrocyte binding are the erythrocyte binding-like (EBL) and the reticulocyte binding-like (RBL or P. falciparum Rh [PfRh]) proteins. We constructed P. falciparum lines lacking expression of EBL proteins by creating single and double knockouts of the corresponding genes for eba-175, eba-181, and eba-140 and show that the EBL and PfRh proteins function cooperatively, consistent with them playing a similar role in merozoite invasion. We provide evidence that PfRh and EBL proteins functionally interact, as loss of function of EBA-181 ablates the ability of PfRh2a/b protein antibodies to inhibit merozoite invasion. Additionally, loss of function of some ebl genes results in selection for increased transcription of the PfRh family. This provides a rational basis for considering PfRh and EBL proteins for use as a combination vaccine against P. falciparum. We immunized rabbits with combinations of PfRh and EBL proteins to test the ability of antibodies to block merozoite invasion in growth inhibition assays. A combination of EBA-175, PfRh2a/b, and PfRh4 recombinant proteins induced antibodies that potently blocked merozoite invasion. This validates the use of a combination of these ligands as a potential vaccine that would have broad activity against P. falciparum.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Protozoan / immunology
  • Antibodies, Protozoan / metabolism
  • Coculture Techniques
  • Enzyme-Linked Immunosorbent Assay
  • Erythrocytes / immunology
  • Erythrocytes / metabolism
  • Erythrocytes / parasitology*
  • Gene Knockout Techniques
  • Humans
  • Immunoblotting
  • Malaria / immunology
  • Malaria / metabolism*
  • Malaria Vaccines / immunology
  • Plasmodium falciparum / genetics
  • Plasmodium falciparum / metabolism
  • Plasmodium falciparum / pathogenicity*
  • Protozoan Proteins / genetics
  • Protozoan Proteins / immunology
  • Protozoan Proteins / metabolism*
  • Rabbits
  • Reticulocytes / immunology
  • Reticulocytes / metabolism
  • Reticulocytes / parasitology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection

Substances

  • Antibodies, Protozoan
  • Malaria Vaccines
  • Protozoan Proteins