Inhibition of tumor necrosis factor mRNA translation by a rationally designed immunomodulatory peptide

Based on sequences of immunomodulatory peptides derived from the heavy chai n of HLA Class I, novel immunomodulatory peptides with increased potency we re developed by computer-aided rational design. Allotrap 1258 was character ized in detail and shown to inhibit cell-mediated immune responses in vitro and in vivo. Immunomodulatory activity was associated with the capability of the peptides to modulate heme oxygenase (HO) activity. In this study we analyzed the effect of Allotrap 1258 on cytokine expression. Allotrap 1258 inhibited concanavalin A- and lipopolysaccharide-induced human and mouse tu mor necrosis factor (TNF) production in vitro and in vivo but had no effect on interleukin (IL)-1, IL-2, IL-4, IL-6, or IL-10 expression. Experiments with HO-1/KO and iNOS/KO mice showed that Allotrap 1258-mediated inhibition of TNF was independent of HO-1 and iNOS. Quantitation of TNF protein expre ssion and mRNA steady state levels demonstrated that Allotrap 1258-mediated inhibition occurred at the translational level. Deletion of the AU-rich el ement in the 3'-untranslated region (UTR) of TNF mRNA, a region known to be involved in TNF mRNA translation, had minimal effect on Allotrap 1258-medi ated inhibition. However, replacement of the TNF 3'-UTR with the human glob in 3'-UTR rendered the peptide inactive. This demonstrates that besides AU- rich elements, other sequences in the 3'-UTR of TNF mRNA are involved in tr anslational control of TNF expression. Such sequences are necessary for All otrap 1258 mediated inhibition of TNF production.