Characterization of a novel inhibitory human monoclonal antibody directed against Plasmodium falciparum Apical Membrane Antigen 1

Sci Rep. 2016 Dec 21:6:39462. doi: 10.1038/srep39462.

Abstract

Malaria remains a major challenge to global health causing extensive morbidity and mortality. Yet, there is no efficient vaccine and the immune response remains incompletely understood. Apical Membrane Antigen 1 (AMA1), a leading vaccine candidate, plays a key role during merozoite invasion into erythrocytes by interacting with Rhoptry Neck Protein 2 (RON2). We generated a human anti-AMA1-antibody (humAbAMA1) by EBV-transformation of sorted B-lymphocytes from a Ghanaian donor and subsequent rescue of antibody variable regions. The antibody was expressed in Nicotiana benthamiana and in HEK239-6E, characterized for binding specificity and epitope, and analyzed for its inhibitory effect on Plasmodium falciparum. The generated humAbAMA1 shows an affinity of 106-135 pM. It inhibits the parasite strain 3D7A growth in vitro with an expression system-independent IC50-value of 35 μg/ml (95% confidence interval: 33 μg/ml-37 μg/ml), which is three to eight times lower than the IC50-values of inhibitory antibodies 4G2 and 1F9. The epitope was mapped to the close proximity of the RON2-peptide binding groove. Competition for binding between the RON2-peptide and humAbAMA1 was confirmed by surface plasmon resonance spectroscopy measurements. The particularly advantageous inhibitory activity of this fully human antibody might provide a basis for future therapeutic applications.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal / immunology*
  • Antigens, Protozoan / immunology*
  • B-Lymphocytes / parasitology
  • Binding, Competitive
  • Cell Line
  • Epitopes / immunology
  • Erythrocytes / immunology
  • Erythrocytes / parasitology*
  • Humans
  • Immunoglobulin G / immunology
  • Inhibitory Concentration 50
  • Leukocytes, Mononuclear / parasitology
  • Membrane Proteins / immunology*
  • Molecular Conformation
  • Nicotiana
  • Plasmodium falciparum / immunology*
  • Protein Binding
  • Protozoan Proteins / immunology*
  • Surface Plasmon Resonance

Substances

  • Antibodies, Monoclonal
  • Antigens, Protozoan
  • Epitopes
  • Immunoglobulin G
  • Membrane Proteins
  • Protozoan Proteins
  • apical membrane antigen I, Plasmodium