Structural modifications to a high-activity binding peptide located within the PfEMP1 NTS domain induce protection against P. falciparum malaria in Aotus monkeys

Abstract

Binding of P. falciparum-infected erythrocytes to vascular endothelium and to uninfected erythrocytes is mediated by the parasite-derived variant erythrocyte membrane protein PfEMP-1 and various receptors, both on the vascular endothelium and on the erythrocyte surface. Consecutive, non-overlapping peptides spanning the N-terminal segment (NTS) and Duffy-binding-like PfEMP1 sequence alpha-domain (DBLalpha) of this protein were tested in erythrocyte and C32 cell binding assays. Eight peptides specifically bound to C32 cells, and were named high-activity binding peptides (HABPs). No erythrocyte binding HABPs were found in this region. Strikingly, three HABPs [6504 ((1)MVELA KMGPK EAAGG DDIED(20)), 6505 ((21)ESAKH MFDRI GKDVY DKVKE(40)) and 6506 ((41)YRAKE RGKGL QGRLS EAKFEK(60))] are located within the NTS, for which no specific function has yet been described. HABP 6505 is neither immunogenic nor protection-inducing; therefore, based on our previous reports, critical amino acids (shown in bold) in HABP-C32 cell binding were identified and replaced to modify HABP immunogenicity and protectivity. Analogue peptide 12722 (ESAKH KFDRI GKDVY DMVKE) produced high antibody titres and completely protected three out of 12 vaccinated Aotus monkeys and 23410 (KHKFD FIGKI VYDMV KER) also produced high protection-inducing titres and completely protected one out of eight monkeys. (1)H NMR studies showed that all peptides were helical. Binding of these peptides to isolated HLADRbeta1 molecules did not reveal any preference, suggesting that they could bind to molecules not studied here.

Research and in situ conservation of owl monkeys enhances environmental law enforcement at the Colombian‐Peruvian border

“…Indeed, scientific publications resulting from research conducted by FIDIC indicate that A. nancymaae and A. nigriceps have been used by them. All these publications have been reported to Corpoamazonia [e.g., Cardenas et al, 2005;Curtidor et al, 2007;Daubenberger et al, 2007;Patarroyo et al, 2006;Rojas-Caraballo et al, 2009;Suárez et al, 2011]. Ruiz-Garcia et al [2013] conducted a molecular genetics analysis of mtDNA COII gene sequences reporting genetic evidence of the illegal trade conducted by FIDIC.…”

Functional, Immunological and Three-Dimensional Analysis of Chemically Synthesised Sporozoite Peptides as Components of a Fully-Effective Antimalarial Vaccine

“…Critical host-cell binding residues have thus been determined by means of competition binding assays with HABP analogues in which each amino acid from an original peptide has been replaced, one by one, by glycine analogue scanning as a strategy for overcoming such "immunological silence". Modifications affecting original peptide binding by more than 50% have therefore been critical for the original interaction between a native HABP and its corresponding host cell receptor and have thus been named critical binding residues [73,[81][82][83].…”

Binding activity, structure, and immunogenicity of synthetic peptides derived from Plasmodium falciparum CelTOS and TRSP proteins

“…Analog peptides were used for subcutaneously immunizing groups of 5-8 Aotus monkeys which were kept in our field station in Leticia (Amazonas, Colombia); animal care and handling were in line with Colombian Institute of Health guidelines which was strictly supervised by the competent Colombian environmental authority (CORPO-AMAZONIA), as previously described (Curtidor et al 2007;Cifuentes et al 2009). The immunization scheme was as follows: 125 lg peptide dissolved in distilled water was homogenized with 250 lL Freund's complete adjuvant (FCA) for the first dose administered on day zero and with 250 lL Freund's incomplete adjuvant (FIA) for the second and third doses administered on days 20 and 40, respectively.…”