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

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 shaw that antagonistic activity can be conferred to peptides of HIV env elope glycoprotein gp120 and reverse transcriptase p66 by adding flanking p olypeptide sequences at the C or at the N terminus by genetic engineering, rather than by introducing substitutions by synthesis. The glutathione S-tr ansferase (GST)-peptide system has been used to produce molecules that disp lay the peptide at the appropriate end of the GST carrier. When the gp120 p eptide 191-205 (pep24) was expressed at the C terminus of GST (GST-24), ant igenicity of specific human CD4 T cells was maintained. In contrast, when t he peptide was expressed at the N terminus of GST (24-GST), antigenicity wa s abolished and antagonistic activity was introduced. Similar results were obtained with a p66-derived peptide at the C terminus of the GST carrier An tagonism was (1) specific; proliferation of a CD4 T cell line from the same donor responding to the envelope glycoprotein of another retrovirus, HTLV- I, was not affected; (2) reversible; proliferative response was rescued in T cells exposed to antigen-presenting cells (APC) pulsed with the antagonis t; (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 c leaved by proteolysis while the antagonistic activity was preserved. Thus a minimal sequence that confers antagonistic activity can be engineered or s ynthesized with peptides to antagonize undesired CD4 responses as an altern ative to the use of APL.