Improved Detection of Human Antibodies to aPlasmodium Antigen Using a Peptide Modified with Aib Residues

Abstract

A 17-mer sequence was selected as a model to study the influence of modifications of terminal ends both on the conformational of a peptide and on its antigenicity towards naturally developing antibodies. This sequence corresponded to a tandemly repeated motif, found in a long repetitive region, with high helical propensity, of a Plasmodium falciparum liver-stage antigen (LSA-1), immunogenic in man. Our model peptide was synthesized with ionizable or non-ionizable ends, or modified in both extremities by introduction of the helix-promoting residue alpha-aminoisobutyric acid (Aib). Helical contribution, absent in the 17 amino-acid sequence possessing ionizable ends, was detectable when non-ionizable ends were introduced, and dramatically increased in the Aib-modified analogue. The presence of ionizable ends totally abolished reactivity towards human sera, otherwise detectable with the peptide possessing non-ionizable ends. While modification by Aib residues was neither detrimental nor beneficial to antigenicity in solution, it clearly resulted in an improved sensitivity of the specific antibody detection when used as solid-phase antigen in ELISA.

Long-Term Multiepitopic Cytotoxic-T-Lymphocyte Responses Induced in Chimpanzees by Combinations ofPlasmodium falciparumLiver-Stage Peptides and Lipopeptides

“…Collectively, these results point to new regions within LSA1, LSA3, and SALSA Ags each bearing at least one CD8 ϩ -CTL epitope. These epitopes are distinct from those previously identified in humans living in malaria-endemic areas (1,2,32,51) and in primate models (9,11,12,14,19,46,47,57). In addition, these results strongly suggest that multiepitopic and MHC-restricted CD8 ϩ CTLs can be simultaneously primed by combinations of LS peptides in Montanide ISA51 and lipopeptides in saline.…”

“…Therefore, the induction and maintenance of CTLs by this set of LS peptides or lipopeptides could rely upon the coexistence in the sequences used of multiepitopes capable of inducing both CD8 ϩ CTLs and CD4 ϩ -T-helper cells. In addition to CD8 CTL responses, several of the LS peptides and lipopeptides used in the present study have also been found previously able to induce CD4 and antibody responses (2,9,11,12,14,19). This is important since developing a vaccine against P. falciparum will likely require generating a breadth of responses that include both humoral and CD8 ϩ CD4 ϩ cellular immunity.…”

Identification of Novel Immunodominant CD4+Th1-Type T-Cell Peptide Epitopes from Herpes Simplex Virus Glycoprotein D That Confer Protective Immunity

“…on a 9050 Pep Synthesizer Instrument by using solid-phase peptide synthesis and standard 9-fluorenylmethoxy carbonyl technology (PE Applied Biosystems, Foster City, Calif.). Peptides were cleaved from the resin by using trifluoroacetic acid-anisole-thioanisole-anisole-ethanedithiol (EDT)-water (87.5:2.5:2.5:2.5:5%) followed by ether (methyl-t-butyl ether) extraction and lyophilization, as previously described (5,7,11). The purity of peptides was between 75 and 96%, as determined by reversed-phase high-performance liquid chromatography (Vydac C 18 ) and mass spectroscopy (Voyager MALDI-TOF System).…”

Systemic immune responses induced by mucosal administration of lipopeptides without adjuvant

“…Anti‐LSA3‐NRII or LSA1‐J peptide antibodies were determined by ELISA as described 22, 23, using sera diluted at 1/100 and revealed by peroxidase‐conjugated goat anti‐mouse IgG (Biosys, Compiègne, France). Results were expressed either as optical density (OD 450 nm ) or as ELISA‐RATIO calculated as previously described 22, 23. Isotype analysis was carried out using class‐specific alkaline phosphatase‐conjugated Goat anti‐Mouse IgA, IgM, IgG1, IgG2a, IgG2b or IgG3 HRP‐labeled as second antibody (Southern Biotechnology Associates, Birmingham, USA).…”