Generating p53-specific cytotoxic T lymphocytes by recombinant adenoviral vector-based vaccination in mice, but not man
Mutations and aberrant expression of the p53 tumor suppressor protein are the most frequent molecular alterations in human malignancy. Peptides derived from the wild-type (wt) p53 protein and presented by major histocompatibility complex (MHC) molecules for T lymphocyte recognition are believed to serve as universal tumor-associated antigens for cancer immunotherapy. We studied the immunogeneicity of a recombinant replication-defective adenoviral vector encoding human full-length wt p53 (rAd/hup53) in human leukocyte antigen (HLA)-A2Kb-transgenic (Tg) mice and man. The generation of p53 epitope-specific cytotoxic T lymphocytes (CTLs) in p53-proficient and p53-deficient A2Kb-Tg mice was affected by self-tolerance and a selective inability of rAd/hup53 to induce p53.264-272 peptide-reactive effector cells. To extend this study into a pilot clinical trial, six advanced-stage cancer patients received sequential injections of rAd/hup53. The treatment was well tolerated. To date, no evidence for objective tumor responses was observed. An amplification of humoral and cellular anti-adenoviral immune responses was demonstrated in all patients following rAd/hup53 vaccination. However, p53-reactive antibodies and HLA-A*0201 (A2.1)-restricted CTLs specific for wt p53 epitopes were not generated. Tailoring p53-based cancer immunotherapy thus requires the interference with p53-specific self-tolerance and the induction of the entire repertoire of p53-reactive T lymphocytes.