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.