HER-2/neu is a self-antigen expressed by tumors and nonmalignant epithelial tissues. The possibility of self-tolerance to HER-2/neu-derived epitopes has raised questions concerning their utility in antitumor immunotherapy. Altered HER-2/neu peptide ligands capable of eliciting enhanced immunity to tumor-associated HER-2/neu epitopes may circumvent this problem. The human CTL peptide HER-2/neu (435-443) [hHER-2(9 435 )] represents a xenogeneic altered peptide ligand of its mouse homologue, differing by one amino acid residue at position 4. In contrast to mHER-2(9 435 ), vaccination of HLA-A*0201 transgenic (HHD) mice with hHER-2(9 435 ) significantly increased the frequency of mHER-2(9 435 )-specific CTL and also induced strong protective and therapeutic immunity against the transplantable ALC tumor cell line transfected to coexpress HLA-A*0201 and hHER-2/neu or rHER-2/neu. Similar results were also obtained with wild-type C57BL/6 mice inoculated with HER-2/neu transfectants of ALC. Adoptive transfer of CD8 + CTL from mice immunized with hHER-2(9 435 ) efficiently protected naive syngeneic mice inoculated with ALC tumors. In conclusion, our results show that HER-2(9 435 ) serves as a tumor rejection molecule. They also propose a novel approach for generating enhanced immunity against a self-HER-2/neu CTL epitope by vaccinating with xenogeneic altered peptide ligands and provide useful insights for the design of improved peptide-based vaccines for the treatment of patients with HER-2/neu-overexpressing tumors.

During the last decade, a large number of tumor-associated antigens (TAA) have been identified, which can be recognized by T cells. This has led to renewed interest in the use of active immunization as a modality for the treatment of cancer. HER-2/neu is a 185-KDa receptor-like glycoprotein that is overexpressed by a variety of tumors including breast, ovarian, lung, prostate and colorectal carcinomata. Several immunogenic HER-2/neu peptides recognized by cytotoxic T lymphocytes (CTL) or helper T lymphocytes (TH) have been identified thus far. Patients with HER-2/neu over-expressing cancers exhibit increased frequencies of peripheral blood T cells recognizing immunogenic HER-2/neu peptides. Various protocols for generating T cell-mediated immune responses specific for HER-2/neu peptides have been examined in pre-clinical models or in clinical trials. Vaccination studies in animals utilizing HER-2/neu peptides have been successful in eliminating tumor growth. In humans, however, although immunological responses have been detected against the peptides used for vaccination, no clinical responses have been described. Because HER-2/neu is a self-antigen, functional immune responses against it may be limited through tolerance mechanisms. Therefore, it would be interesting to determine whether abrogation of tolerance to HER-2/neu using appropriate adjuvants and/or peptide analogs may lead to the development of immune responses to HER-2/neu epitopes that can be of relevance to cancer immunotherapy. Vaccine preparations containing mixtures of HER-2/neu peptides and peptide from other tumor-related antigens might also enhance efficacy of therapeutic vaccination.

IL-21 plays a role in the proliferation and maturation of NK cells developed from hematopoietic stem cells. In this study, we found that IL-21, in the presence of physiological concentration of hydrocortisone (HC), has a significant impact on the functions of NK cells derived from umbilical cord blood (CB) populations. We demonstrate that IL-21, in combination with Flt3-ligand, IL-15 and HC, induces high proliferative responses and, apart from enhancing NK-mediated cytotoxicity, it also induces a significant increase in lymphokine-activated killer activity of CB/CD34+-derived CD56+ cells. In addition, IL-21 induced changes in the CD56+ cell cytokine secretion profile. Thus, we observed increased levels of IL-10 and granulocyte macrophage colony-stimulating factor, whereas tumor necrosis factor-alpha levels decreased. IFN-gamma production was also modified by IL-21, depending on the presence or absence of IL-18. CB/CD34+ cells did not express the IL-21R ex vivo, but receptor expression was induced during their commitment to differentiation into CD56+ cells. Our data ascribe to IL-21 an essential role on NK cell development and function under conditions similar to the in vivo CB microenvironment.

Summary The present study investigated the ability of supernatants collected from cultures of healthy donor-derived peripheral blood mononuclear cells (HD-PBMCs) stimulated with anti-CD3 monoclonal antibody (MAb) (allogeneic CD3 supernatants; ACD3S) to induce, upon brief exposure, tumour-reactive cytotoxic lymphocytes in cancer patients' PBMCs. ACD3S enhanced natural killer (NK) and lymphokineactivated killer (LAK) cell-mediated cytotoxicity. ACD3S contained increased levels of interleukins (IL) 1, 2, 6, 7 and 12, as well as of granulocyte-macrophage colony-stimulating factor (GM-CSF), gamma-interferon (IFN-y) and tumour necrosis factor-a (TNF-a). MAbs against these cytokines significantly reduced the ACD3S-induced cytotoxicity. ACD3S-induced cytotoxicity was not inhibited by anti-CD4, CD8 and MHC class MAbs, but was markedly reduced in the presence of MAb against CD18. In contrast to HD-PBMC, ACD3S derived from cancer patients' lymphocytes exhibited lower levels of the above-mentioned cytokines and exerted reduced biological activity. In conclusion, ACD3S are able to activate, upon short-term incubation, tumour-reactive lymphocytes from cancer patients' PBMCs that lyse a variety of tumour targets, including autologous tumours. ACD3S contain high levels of certain cytokines that positively influence the induction of autologous tumour-reactive lymphocytes. Such supernatants can be collected easily from healthy donors and stored until use in clinical trials for adoptive cellular therapy of cancer. They may also be indicated in the construction of cytokine cocktails that have the ability to induce antitumour cytotoxicity.

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