Ii-Key/HER-2/neu MHC class-II antigenic epitope vaccine peptide for breast cancer.

PURPOSE: Cytotoxic T lymphocytes (CTL)- and T-helper cell-specific, and major histocompatibility complex (MHC) class-I and class-II peptides, respectively, of the HER-2/ neu protein, induce immune responses in patients. A major challenge in developing cancer peptide vaccines is breaking tolerance to tumor-associated antigens which are functionally self-proteins. An adequate CD4+ T-helper response is required for effective and lasting responses. METHODS: Stimulating anti-cancer CD4+ T cell responses by MHC class-II epitope peptides has been limited by their weak potency, at least compared with tight-binding MHC class-I epitope peptides. Previously, a potent T-cell response to a MHC class-II epitope was engineered by coupling the N-terminus of the pigeon cytochrome C [PGCC(95-104)] MHC class-II epitope to the C-terminus of an immunoregulatory segment of the Ii protein (hIi77-81, the Ii-Key peptide) through a polymethylene spacer. RESULTS: In vitro presentation of the MHC class-II epitope to a T hybridoma was enhanced greatly (>250 times). Now, an Ii-Key/HER-2/neu (777-789) MHC class-II epitope hybrid peptide stimulated lymphocytes from both a healthy donor and a patient with metastatic breast carcinoma. The in vitro primary stimulation with the hybrid peptide strongly activated IFN-gamma release, whereas the epitope-only peptide was weakly active. In fact, the hybrid stimulated IFN-gamma release as well as the wild-type peptide when augmented with IL-12; however, the hybrid was comparable to free peptide in stimulating IL-4 release. This pattern is consistent with preferential activation along a non-tolerogenic Th1 pathway. CONCLUSION: Such Ii-Key/MHC class-II epitope hybrid peptides have both diagnostic and therapeutic applications.

Toxicity, immunogenicity, and induction of E75-specific tumor-lytic CTLs by HER-2 peptide E75 (369-377) combined with granulocyte macrophage colony-stimulating factor in HLA-A2+ patients with metastatic breast and ovarian cancer.

To determine the toxicity and immunogenicity of the HER-2/neu, HLA-A2-restricted peptide E75 in patients with metastatic breast and ovarian cancer, 14 patients were vaccinated with escalating amounts of E75 (100, 500, and 1000 microg) mixed with 250 microg granulocyte macrophage colony-stimulating factor as adjuvant. Each vaccine dose was administered in a total volume of 1.5 ml divided into four intradermal injections and administered weekly for 4 weeks, followed by monthly boosts for a total of 10 injections. Vaccinations were well tolerated without significant toxicity. Blood was drawn before, at 8 weeks, and up to 13-16 months after vaccination for measurement of cellular immunity. Seven of 8 patients tested had significant delayed type hypersensitivity to E75 defined as >5 mm induration. Peripheral blood mononuclear cells from 5 of 9 patients tested proliferated to E75 with a stimulation index of > or = 2.0. Of 8 vaccinated patients tested for induction of a CTL response, 4 responded to stimulation by autologous dendritic cells plus cytokines by eliciting E75-specific lytic activity consistent with the presence of activated/memory cells, 2 others after in vitro stimulation with E75 + interleukin-12 +/- anti-CD152(33KD), whereas 2 others did not respond. Four patients with E75-specific CTLs present specifically recognized E75 on indicator tumors as demonstrated by cold-target inhibition of tumor lysis. These 4 patients showed E75-specific IFN-gamma production. peripheral blood mononuclear cell from 3 of these patients proliferated to E75, but stimulation indices were higher in the prevaccine samples. All 4 of the patients showed DTH responses to E75. These results demonstrate that vaccination with E75+ granulocyte macrophage colony-stimulating factor can induce both peptide-specific IFN-gamma and epitope specific CTLs, which lyse HER-2/neu+ tumors in stage IV patients.