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

Abstract

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(776-790) 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-gamma-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(435-443) CTL epitope, as illustrated by either IFN-gamma ELISPOT assays or specific autologous tumor cell lysis. Hybrid peptide-specific CD4+ T cells strongly enhanced the antitumor efficacy of HER-2/neu(435-443) 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(776-790) 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(776-790) hybrid peptides.

A new era in anticancer peptide vaccines

“…41,42 We also observed strong immunogenicity with HER-2/neu(776-790), which is an extended analog of the p776 to p788 peptide. [43][44][45] CD4-positive T cells primed with the p776 to p790 peptide exhibited an extensive capacity to synergize with syngeneic CTLs for the rejection of HER-2/neu-positive tumors. [43][44][45] Both the p776 to p790 peptide and the p776 to p788 peptide encompass in their sequences the nonamers GVGSPYVSRL (p776-p784), VGSPYVSRL (p777-p785), and PYVSRLLGI (p780-788), which bind with intermediate to high affinity to the HLA-A2.1/A68, HLA-A11, and HLA-A3 alleles, respectively.…”

“…[43][44][45] CD4-positive T cells primed with the p776 to p790 peptide exhibited an extensive capacity to synergize with syngeneic CTLs for the rejection of HER-2/neu-positive tumors. [43][44][45] Both the p776 to p790 peptide and the p776 to p788 peptide encompass in their sequences the nonamers GVGSPYVSRL (p776-p784), VGSPYVSRL (p777-p785), and PYVSRLLGI (p780-788), which bind with intermediate to high affinity to the HLA-A2.1/A68, HLA-A11, and HLA-A3 alleles, respectively. Thus, the p776 to p790 peptide may function as a multipeptide vaccine that contains overlapping T h and CTL epitope motifs, thereby acting as a powerful inducer of antitumor immune responses.…”

Results from a Phase I Clinical Study of the Novel Ii-Key/HER-2/neu(776–790) Hybrid Peptide Vaccine in Patients with Prostate Cancer

“…19). To assess whether immune responses elicited in vivo reflected reactivity against the native HER-2/ neu peptide, we evaluated immune responses against both AE36 and AE37.…”

“…Covalent linkage of this Ii-Key segment to MHC class II epitopes significantly augments antigen presentation (13)(14)(15)(16). Work from our laboratory has shown that the HER-2/neu(776-790) epitope serves as a compelling tumor antigen and that CD4 + T cells primed with the synthetic HER-2/neu(776-790) peptide help autologous CTL for increased antitumor activity (17)(18)(19). In a series of studies (14,(17)(18)(19)(20), we have shown that the Ii-Key/ HER-2/neu(776-790) hybrid (AE37) induces more potent immunologic responses both in vitro and in vivo compared with the nonmodified HER-2/neu(776-790) peptide (AE36).…”

“…Work from our laboratory has shown that the HER-2/neu(776-790) epitope serves as a compelling tumor antigen and that CD4 + T cells primed with the synthetic HER-2/neu(776-790) peptide help autologous CTL for increased antitumor activity (17)(18)(19). In a series of studies (14,(17)(18)(19)(20), we have shown that the Ii-Key/ HER-2/neu(776-790) hybrid (AE37) induces more potent immunologic responses both in vitro and in vivo compared with the nonmodified HER-2/neu(776-790) peptide (AE36). Recently, Holmes et al (21) conducted a phase I study of the AE37 hybrid peptide in HER-2/neu-positive breast cancer patients and showed strong immunologic responses to the vaccine.…”