Plasmodium falciparum AMA-1 erythrocyte binding peptides implicate AMA-1 as erythrocyte binding protein

Abstract

The role of AMA-1 during merozoite invasion has not yet been determined. However, reported experimental evidence suggests that this protein can be used, in particular as erythrocyte-binding protein, since, Fab fragments against this protein are able to block merozoite invasion. Using a previously described methodology, eight peptides with high binding activity to human erythrocyte, scattered along the different domains and having around 130 nM affinity constants, were identified in the Plasmodium falciparum AMA-1 protein. Their binding activity was sialic acid independent. Some of these peptides showed homology with the erythrocyte binding domains of one of the apical organelle protein family, MAEBL, identified in rodent malarial parasites. One of these peptides shares amino acid sequence with a previously reported B-cell epitope which induces antibodies to block parasite growth. The critical residues were identified for erythrocyte binding conserved peptides 4313 (DAEVAGTQ YRL PSGKCPVFG), 4321 (VVDN WE KV C PRKN L QNAKFG), 4325 (MIK SA FLPTGAFK AD R Y KSH) and 4337 ( W GE E KRAS H TTPVLMEKPYY). All conserved peptides were able to block merozoite invasion of new RBC and development, suggesting that these peptides are involved in P. falciparum invasion.