Generation of Stable CD4+and CD8+T Cell Lines from Patients Immunized withrasOncogene-Derived Peptides Reflecting Codon 12 Mutations

• Published in: Cellular immunology 1997-12, Vol.182 (2), p.137-151
• Main Authors: Abrams, Scott I., Khleif, Samir N., Bergmann-Leitner, Elke S., Kantor, Judith A., Chung, Yoomie, Hamilton, J.Michael, Schlom, Jeffrey
• Format: Article
• Language: English
• ISSN: 0008-8749; 1090-2163
• DOI: 10.1006/cimm.1997.1224

Previous studies have identified and characterized both murinein vivoand humanin vitroT cell responses reflecting specific mutations in therasproto-oncogenes at codon 12, 13, or 61. In an attempt to determine whether peptide epitopes reflecting point mutations in therasoncogenes are immunogenic in humans for the production of CD4+and/or CD8+T cell responses, a phase I clinical trial was initiated in metastatic carcinoma patients whose primary tumors harbor mutations in the K-rasproto-oncogenes at codon 12. The peptides used here as immunogens, which were administered in Detox adjuvant, spanned therassequence 5–17 and reflected the amino acid substitution of glycine (Gly) at position 12 to aspartic acid (Asp), cysteine (Cys), or valine (Val). Three of eight evaluable patients have demonstrated peptide-specific cell-mediated immunity, as determined by the production of T cell lines resulting from the vaccination. First, an antigen (Ag)-specific, major histocompatibility complex (MHC) class II (DP)-restricted CD4+T cell line was establishedin vitrofrom postvaccination lymphocytes of a non-small cell lung carcinoma patient whose primary tumor contained a Cys12 mutation when cultured on the immunizing peptide. Moreover, CD4+proliferation was inducible against the corresponding mutant K-rasprotein, suggesting productive T cell receptor recognition of exogenously processed Ag. Second, an Ag-specific, MHC class I (HLA-A2)-restricted CD8+cytotoxic T lymphocyte (CTL) line was establishedin vitrofrom postvaccination lymphocytes of a colon carcinoma patient whose primary tumor contained an Asp12 mutation. To that end, a 10-mer peptide, nested within the 13-mer immunizing peptide, was identified [i.e.,ras5-14(Asp12)], which was shown to bind to HLA-A2 and display specific functional capacity for expansion of thein vivoprimed CD8+CTL precursors. Third, both Ag-specific, MHC class II (DQ)-restricted CD4+and MHC class I-restricted (HLA-A2) CD8+T cell lines were generated from a single patient with duodenal carcinoma whose primary tumor contained a Val12 mutation when cultured on the immunizing 13-mer peptide or a nested 10-mer peptide [i.e.,ras5-14(Val12)], respectively. Evidence is thus provided that vaccination with mutantrasoncogene peptides in adjuvant may induce specific anti-rascellular immune responses, with no detectable cross-reactivity toward normal proto-rassequences. Moreover, we have identified for the first time human HLA-A2-restricted, CD8+CTL epitopes refl