Immunomodulating activity of analogs of noninflammatory fragment 163-171 of human interleukin-1beta

The synthetic nonapeptide Val-Gln-Gly-Glu-Glu-Ser-Asn-Asp-Lys corresponding to the amino acid sequence 163-171 of human interleukin-1beta (IL-1beta) has been reported to retain considerable immunostimulatory activity of the native protein without the induction of the inflammatory or pyrogenic responses. Two lipophilic derivatives of this nonapeptide, one having a lauroyl residue (1) and the other having a palmitoyl residue (2) at the N-terminus of the peptide, and a more stable analog carrying D-Val residue at position 1 of the peptide (3) were synthesized with a view to find out if these structural modifications had a favorable effect on in vitro mouse thymocyte proliferation and IL-1 dependent inhibition of A375 cells. We have found that analogs (1) and (2) are active in both the tests like the parent nonapeptide. The lipophilic analog (2) is in fact, effective at a lower dose as compared to the parent nonapeptide in mouse thymocyte proliferation assay. Although the analog (3) has the ability to inhibit A375 cells, it does not stimulate mouse thymocyte proliferation in vitro. The IL-1beta fragment (163-171) and the analog (2) were further compared for their effects on pyrogenicity, blood glucose level, acute phase response and radioprotection. Unlike IL-1beta, its fragment (163-171) and the analog (2) do not induce pyrogenicity and any of the acute phase related changes such as the increase in C-reactive protein and hypoglycemia following their administration in Balb/c mice. We have found that 40% of animals treated with analog (2) survive more than 21 days after lethal irradiation as compared to 20% survivors in groups treated with recombinant IL-1beta or its nonapeptide fragment (163-171), under conditions when all the control animals died within 10 days. This study may help in designing small peptides which may be more effective and stable.

Conformation of a T-cell stimulating peptide of interleukin-1 beta protein: circular dichroism studies

A T-cell stimulating peptide Val-Gln-Gly-Glu-Glu-Ser-Asn-Asp-Lys-OH, the 163-171 fragment epitope of interleukin-1 beta (IL-1 beta), has been synthesized in solution phase and purified by reverse-phase high-performance liquid chromatography (RP-HPLC). The backbone conformation of the synthetic fragment, investigated in aqueous solution by circular dichroism (CD) spectroscopy, is qualitatively a mixture of beta-turns and random coil. Quantification of the CD spectra revealed the presence of a 9% beta-turn fraction in water at pH 7.0, suggesting the occurrence of the conformation for the epitope fragment in aqueous solution necessary for T-cell stimulation and antigenicity. Concomitant changes in CD spectra were observed with increases in the trifluoroethanol (TFE) concentration in water, and the beta-turn fraction in peptide increased to 28% at a concentration of 90% TFE. This helicogenic solvent, as well as other solvents such as methanol, acetonitrile and dioxane (all favouring an ordered structure in peptides), failed to induce any alpha-helical conformation in the IL-1 beta (163-171) fragment, and CD spectra were attributed to only beta-turn ordered structure. This beta-turn structure has also been found to be a theoretically preferred conformation using Chou-Fasman proclivity data and is in accordance with the presence of an all-beta-globular conformation for its parent molecule IL-1 beta. Thus, the beta-turn conformation is probably involved in retention of T-cell stimulation activity in this synthetic epitope.

Development of glycosylated human interleukin-1 alpha, neoglyco IL-1 alpha, coupled with D-mannose dimer: synthesis and biological activities in vitro

Interleukin 1 (IL-1) is a nonglycosylated cytokine with pleiotropic effects on various cell types. In order to investigate the effect of carbohydrate introduction on IL-1 activity and to develop IL-1 with less deleterious effects recombinant human IL-1 alpha was chemically coupled with mannose dimers, alpha-D-Man1-6-D-Man[Man2(alpha 1,6)] and alpha-D-Man1-4-D-Man[Man2(alpha 1,4)]. About 5 molecules of mannose dimers were introduced per molecule of IL-1. Anti-IL-1 alpha antibody reacted only weakly with the glycosylated IL-1s. Conversely, antibody against the mannose dimer reacted with only glycosylated IL-1. The effect of glycosylation on IL-1 activity was evaluated by measuring a variety of IL-1 activities in vitro, including proliferative effect on T cells, antiproliferative effect on melanoma cells, stimulatory effect on IL-6 synthesis by melanoma cells, and stimulatory effect on prostaglandin E2 synthesis by fibroblast cells. Glycosylated IL-1s exhibited reduced activities, which were 10-fold to more than several hundred-fold lower than those of the original IL-1 alpha depending upon different aspects of activities addressed. Man2(alpha 1,6)-introduced IL-1 exhibited lower activity than Man2(alpha 1,4)-introduced IL-1. The competitive binding of 125I-IL-1 alpha to mouse T cells with unlabeled IL-1s suggests that the reduced activity of glycosylated IL-1s is due, at least partially, to the decrease of their receptor binding abilities.

In vivo immunostimulating activity of the 163-171 peptide of human IL-1 beta

The stimulating effect of a synthetic nonapeptide (fragment 163-171) of human interleukin 1 beta (IL-1 beta) on antibody responses to both T helper-dependent and T helper-independent antigens was investigated. It was shown that the nonapeptide enhanced the antibody response, as evaluated in the hemolytic plaque assay, of spleen cells from mice immunized with sheep red blood cells (SRBC). The activity of the 163-171 peptide on the primary response to SRBC was dose-dependent, being maximal when the peptide was inoculated at 100 mg/kg together with the antigen. Moreover, the 163-171 peptide was also effective in enhancing the secondary response to SRBC. The effect of the 163-171 peptide was to augment the frequency of cells specific for the antigen, inasmuch as no increase was ever observed in spleen cell numbers after treatment. In all these studies, human recombinant IL-1 beta gave effects qualitatively comparable to those of the 163-171 peptide, with a maximal activity at 20 ng/kg. Both the 163-171 peptide and human recombinant IL-1 beta were also able to enhance the in vivo immune response to a T helper-independent antigen such as SIII, a poorly immunogenic polysaccharidic antigen from Streptococcus pneumoniae type III. It can therefore be proposed that this synthetic nonapeptide of human IL-1 beta may represent a good candidate for use as adjuvant in vaccines.