Ii-Key/HER-2/neu(776-90) hybrid peptides induce more effective immunological responses over the native peptide in lymphocyte cultures from patients with HER-2/neu+ tumors
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- Sotiriadou, N.N., Kallinteris, N.L., Gritzapis, A.D. et al. Cancer Immunol Immunother (2007) 56: 601. doi:10.1007/s00262-006-0213-z
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We have demonstrated that coupling an immunoregulatory segment of the MHC class II-associated invariant chain (Ii), the Ii-Key peptide, to a promiscuous MHC class II epitope significantly enhances its presentation to CD4+ T cells. Here, a series of homologous Ii-Key/HER-2/neu(776-90) hybrid peptides, varying systematically in the length of the epitope(s)-containing segment, are significantly more potent than the native peptide in assays using T cells from patients with various types of tumors overexpressing HER-2/neu. In particular, priming normal donor and patient PBMCs with Ii-Key hybrid peptides enhances recognition of the native peptide either pulsed onto autologous dendritic cells (DCs) or naturally presented by IFN-γ-treated autologous tumor cells. Moreover, patient-derived CD4+ T cells primed with the hybrid peptides provide a significantly stronger helper effect to autologous CD8+ T cells specific for the HER-2/neu(435-43) CTL epitope, as illustrated by either IFN-γ ELISPOT assays or specific autologous tumor cell lysis. Hybrid peptide-specific CD4+ T cells strongly enhanced the antitumor efficacy of HER-2/neu(435-43) peptide-specific CTL in the therapy of xenografted SCID mice inoculated with HER-2/neu overexpressing human tumor cell lines. Our data indicate that the promiscuously presented vaccine peptide HER-2/neu(776-90) is amenable to Ii-Key-enhancing effects and supports the therapeutic potential of vaccinating patients with HER-2/neu+ tumors with such Ii-Key/HER-2/neu(776-90) hybrid peptides.