Antagonistic activity of HIV-1 T helper peptides flanked by an unrelated carrier protein

Abstract

Antagonism is the ability of a modified antigenic peptide (altered peptide ligand, APL) to prevent CD4 T cell activation by the original peptide. Here we show that antagonistic activity can be conferred to peptides of HIV envelope glycoprotein gp120 and reverse transcriptase p66 by adding flanking polypeptide sequences at the C or at the N terminus by genetic engineering, rather than by introducing substitutions by synthesis. The glutathione S-transferase (GST)-peptide system has been used to produce molecules that display the peptide at the appropriate end of the GST carrier. When the gp120 peptide 191-205 (pep24) was expressed at the C terminus of GST (GST-24), antigenicity of specific human CD4 T cells was maintained. In contrast, when the peptide was expressed at the N terminus of GST (24-GST), antigenicity was abolished and antagonistic activity was introduced. Similar results were obtained with a p66-derived peptide at the C terminus of the GST carrier. Antagonism was (1) specific; proliferation of a CD4 T cell line from the same donor responding to the envelope glycoprotein of another retrovirus, HTLV-1, was not affected; (2) reversible; proliferative response was rescued in T cells exposed to antigen-presenting cells (APC) pulsed with the antagonist; (3) dominant; T cells cultured with APC pulsed with the agonist and with APC pulsed with the antagonist did not proliferate. The carrier could be cleaved by proteolysis while the antagonistic activity was preserved. Thus a minimal sequence that confers antagonistic activity can be engineered or synthesized with peptides to antagonize undesired CD4 responses as an alternative to the use of APL.

Clustering of Th Cell Epitopes on Exposed Regions of HIV Envelope Despite Defects in Antibody Activity

“…Vaccine approaches that involve either the production or the injection of native proteins may thus be preferable to those using shuffled or linked peptides (47)(48)(49). In the latter instance, it is possible that mechanisms of processing and presentation may be altered when peptides are removed from their normal context (50). Vaccines that maintain native envelope structures and preserve natural processing mechanisms might best mimic the live viruses they are designed to eradicate.…”

Identification of an I‐Ad restricted peptide on the 65‐kilodalton heat shock protein of Mycobacterium avium

“…Clones 8.10 and 8.22, arising from line eight did not, however, respond to any of the four fusion fragments. Flanking sequences may influence the presentation of epitopes, particularly if they are present very close to point of fusion with the fusion partner leading to alteration in antigen processing 3 , 38 . To eliminate the possibility of GST influencing antigen presentation, it was removed by thrombin digestion from all four proteins.…”