Thymosin-like peptides as potential immunostimulants. Synthesis via the polymeric-reagent method

This paper reports our attempt at designing new immunostimulating peptides which are chemically related to the bioactive peptides thymosin alpha 1 and thymopentin. Three peptides were synthesized, Asp-Leu-Lys-Glu-Arg-Lys-Asp-Val-Tyr (3), Arg-Lys-Asp-Val-Tyr-Glu-Glu-Ala-Glu-Asn (2), and Asp-Leu-Lys-Glu-Arg-Lys-Asp-Val-Tyr-Glu-Glu-Ala-Glu-Asn (1), each of which contains the thymopentin sequence and portions of the bioactive sequence of thymosin alpha 1. Peptides 1-3 were assembled from selected blocked fragments that were synthesized by the polymeric-reagent method, using PHBT (polystyrene-bound 1-hydroxybenzotriazole) as the activating polymer. The ability of peptides 1-3 to enhance the activation (RNA synthesis) and proliferation (DNA synthesis) of human T lymphocytes was determined. In comparison to thymosin alpha 1, thymosin alpha 1 (15-28), and thymopentin, peptides 1-3 did not show significant enhancement of these processes.