β-Interleukin I (163-171), human

Cytokines as vaccine adjuvants: interleukin 1 and its synthetic peptide 163-171

The possibility of preventing infectious diseases by employing efficacious vaccine is rapidly growing as a consequence of the new technologies in recombinant DNA and protein chemistry. However, the increasing number of synthetic and recombinant antigens further stresses the role of appropriate adjuvants to ensure maximal vaccine activity and the protection of all vaccinees. Several approaches can be applied to develop safe and effective agents capable of enhancing specific immune responses which can then protect the host from the pathogen. Among others, the direct use as adjuvant of those cytokines which are induced in animals by the classical Freund's adjuvants has recently become a matter of investigation. In particular, interleukin 1 (IL-1) has been shown to possess adjuvant activity for a variety of infectious and tumour antigens. However, the numerous side effects associated with the proinflammatory action of IL-1 represent a serious disadvantage for its use as a vaccine adjuvant. It was therefore of great interest that a nonpeptide contained in the IL-1 beta sequence (residues 163-171 corresponding to the sequence VQGEESNDK) is devoid of all proinflammatory activities but maintains the immunostimulating activity of the whole IL-1 beta. Thus, peptide 163-171 was successfully employed in animals to potentiate the specific immune response against T-helper-dependent cellular antigens, T helper-independent polysaccharidic antigens and recombinant as well as synthetic antigenic preparations derived from human pathogens. Furthermore, IL-1 and peptide 163-171 have been successfully used in tumour vaccines in experimental systems. It can therefore be concluded that peptide 163-171 is potentially a good candidate as vaccine adjuvant for human use.

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.

Comparison of human interleukin-1 beta and its 163-171 peptide in bone resorption and the immune response

Human interleukin-1 beta (IL-1 beta) caused a dose- and time-dependent enhancement of the release of 45Ca from prelabeled mouse calvaria in organ culture. In addition, IL-1 beta dose-dependently stimulated the formation of prostaglandin E2 (PGE2) and 6-keto-PGF1 alpha in the calvarial bones. However, IL-1 beta-induced 45Ca release was only partially inhibited by blocking the PGE2 response with indomethacin, suggesting that enhanced PGE2 formation in response to IL-1 beta is not necessary to obtain a bone resorptive effect, but that prostaglandins potentiate the action of IL-1 beta. The synthetic nonapeptide VQGEESNDK, corresponding to the fragment 163-171 of human IL-1 beta, administered simultaneously with antigen (SRBC) to C3H/HeN male mice, induced a dose-dependent enhancement of specific antibody-producing cells in the spleen (PFC). The degree of PFC stimulation was comparable to that caused by native human IL-1 beta. In mouse bone cultures, neither 45Ca release nor prostanoid formation was stimulated by fragment 163-171. These data indicate that (1) IL-1 beta-induced stimulation of bone resorption is dissociable from IL-1 beta-induced increase of prostanoid biosynthesis and (2) the epitope of the IL-1 beta molecule involved in the immunostimulatory effects may be different from that involved in the stimulatory effects on bone resorption.

Binding and internalization of the 163-171 fragment of human IL-1 beta

The mechanisms of cell association of the human interleukin (IL-1 beta) immunostimulatory fragment 163-171 have been studied. The fragment was able to associate abundantly to both IL-1R- and IL-1R+ cells. Binding was strictly temperature dependent, was not saturable and could be inhibited by excess amounts of unlabelled 163-171 peptide but not by IL-1 beta, suggesting that the 163-171 fragment is not an IL-1R-binding domain of IL-1 beta. The fragment is readily internalized by cells by a cytochalasin-insensitive mechanism and it localizes mainly in the cytoplasm. It is concluded that the active domain 163-171 of IL-1 beta can be taken up by cells through a receptor-independent, temperature-dependent mechanisms and that its ability to activate cellular functions is based on IL-1R-independent intracellular pathways.