Induction of p53-Specific Immunity by a p53 Synthetic Long Peptide Vaccine in Patients Treated for Metastatic Colorectal Cancer

Abstract

Purpose: The tumor-associated self-antigen p53 is commonly overexpressed in cancer, including colorectal cancer, and can serve as a target for immunotherapy. The safety and immunogenicity of a p53 synthetic long peptide (p53-SLP) vaccine were investigated in patients treated for metastatic colorectal cancer. Experimental Design:Ten patients were vaccinated twice with a set of 10 overlapping p53-SLP in a phase I/II trial. Both the safety and the breadth, magnitude, and polarization of vaccineinduced p53-specificTcells was evaluated in blood samples drawn before and after vaccination by IFN-g enzyme-linked immunospot, proliferation, cytokine secretion, and multiparameter flow cytometry. The migratory capacity of p53-specificT cells was evaluated by assessing their presence in a biopsy of the second vaccination site. Results: Toxicity was limited to grade 1/2, mostly at the vaccination site. p53-specific T-cell responses were induced in 9 of 10 colorectal cancer patients as measured by IFN-g enzymelinked immunospot, proliferation, and cytokine bead array. In 6 of 9 tested patients, p53-specific T-cell reactivity persisted at least 6 months. Furthermore, p53-specific T cells isolated from the vaccination site were characterized as CD4 + T cells producing bothT-helper types 1and 2 cytokines on stimulation with p53 peptide and p53 protein. Multiparameter flow cytometry revealed that only a minor population of the p53-specific CD4 + Tcells was optimally polarized. Conclusions: The p53-SLP vaccine is safe and capable to induce p53-specificT-cell responses in patients treated for colorectal cancer. New trials should focus on improving the polarization of the p53-SLP vaccine-induced T-cell response.

Long-peptide vaccination with driver gene mutations in p53 and Kras induces cancer mutation-specific effector as well as regulatory T cell responses

“…The responses against mutated peptides were overall higher than those against wt peptides arguing for mutation specificity of the tumor Ag specific T cell pool in CRC patients and for immunogenicity of the chosen mutations and long peptide sequences. Our observations are in accordance with investigations defining the preexistence of intrinsic and vaccination-induced TC responses against wt and mutated Kras 15,40 and p53 64,65 sequences in patients with gastrointestinal cancers.…”

CD20 alternative splicing isoform generates immunogenic CD4 helper T epitopes

“…Briefly, these mice are H-2 Class I and IA Class II knockout, and their CD8 T and CD4 T cells are restricted by the sole HLA-A*0201 and HLA-DR1*0101 molecules, respectively. 11,15 For D393-CD20 [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] (20mer) and D393-CD20 33-41 (9mer) immunization, mice were injected twice with 100 lg of D393-CD20 20mer or 50 mg of D393-CD20 9mer were emulsified in incomplete Freund adjuvant (IFA, Sigma-Aldrich). All peptide vaccinations were done subcutaneously at the base of the tail at Days 1 and 14.…”

“…2c). To further investigate the promiscuous HLA-DR binding capacity of D393-CD20 [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] peptide and the degeneracy of T cell recognition, the reactivity of the CD4 T cell clones was evaluated against various HLA-DR-positive and D393-CD20-negative loaded with the D393-CD20 [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] peptide. CD4 T cell clones from patient P#1 (HLA-DRB1*04 homozygote) and patient P#7 (HLA-DRB1*04 and -DRB1*11) were reactive against the HLA-DRB1*04 positive cell line FaDu loaded with the cognate peptide (Fig.…”

“…The three first amino-acids used to name these peptides are indicated in boldface. T cell lines were obtained from healthy donors' PBMCs after two rounds of in vitro stimulation in microplates with 10 lg/mL of D393-CD20 [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] peptide. Specific responses were assessed by CD4 and IFN-g staining.…”

“…24 We then evaluated the capacity of the D393-CD20 28-47 long peptide (LP) to prime HLA-A2-restricetd CTL response. To this end, mice were immunized either with the D393-CD20 [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] LP or with the HLA-A2-restricted D393-CD20 derived short peptide D393-CD20 [33][34][35][36][37][38][39][40][41] (SP). As shown in Figure 5b, higher IFN-g producing specific-CTL were detected ex vivo after immunization with the D393-CD20 28-47 LP than with the SP.…”