AN HLA-RESTRICTED, P53 SPECIFIC IMMUNE-RESPONSE FROM HLA TRANSGENIC P53 KNOCKOUT MICE

Background: p53 is over-expressed in most human malignancies and is th erefore an attractive target for immunotherapy. Unfortunately, a human cytotoxic T cell response to p53 is difficult to generate. p53 knocko ut transgenic mice may provide a model to circumvent immunologic toler ance to p53 and develop high-affinity p53-specific cytotoxic T lymphoc ytes (CTL). Methods: p53 knockout, HLA A2.1 transgenic mice were gener ated and immunized with the immunodominant wild-type p53 nonamer pepti de epitope p53149-157. Two weeks later splenocytes were harvested and stimulated in vitro with acid-treated, p53 peptide-pulsed syngeneic bl ast cells. Cultures were restimulated weekly with acid-treated, p53 pe ptide-pulsed Jurkat cells transfected with the HLA A2.1 gene. Peptide- specific cytotoxic activity was measured by chromium release assay, an d the resulting CD8+ effecters were cloned via limiting dilution. Resu lts: P53 peptide-specific CTL were generated against p53149-157. Clone s generated from the p53149-157 cell line demonstrated high affinity a nd specificity for p53149-157 when presented by HLA A2.1+ antigen-pres enting cells. The p53149-157 CTL killed only cells overexpressing p53 cells that were HLA A2.1+ and did not kill cells with normal levels of p53 expression or those that were HLA A2.1-. Conclusion: HLA transgen ic mice not previously exposed to the p53 protein provide a useful mod el for generating high-affinity p53-specific CTL.