Antigen Experienced T Cells from Peripheral Blood Recognize p53 Neoantigens.

Abstract

The purpose of this study was to evaluate antigen experienced T cells in peripheral blood lymphocytes (PBL) for responses to p53 neoantigens. PBLs from patients with a mutated <i>TP53</i> tumor were sorted for antigen-experienced T cells and <i>in vitro</i> stimulation (IVS) was performed with p53 neoantigens. The IVS cultures were stimulated with antigen-presenting cells expressing p53 neoantigens, enriched for 41BB/OX40 and grown with rapid expansion protocol. T-cell responses were not observed in the PBLs of 4 patients who did not have tumor-infiltrating lymphocyte (TIL) responses to mutated <i>TP53</i>. In contrast, 5 patients with TIL responses to mutated <i>TP53</i> also had similar T-cell responses in their PBLs, indicating that the PBLs and TILs were congruent in p53 neoantigen reactivity. CD4⁺ and CD8⁺ T cells were specific for p53^R175H, p53^Y220C, or p53^R248W neoantigens, including a 78% reactive T-cell culture against p53^R175H and HLA-A*02:01. Tracking <i>TCRB</i> clonotypes (clonality, top ranked, and <i>TP53</i> mutation-specific) supported the enrichment of p53 neoantigen-reactive T cells from PBLs. The same T-cell receptor (TCR) from the TIL was found in the IVS cultures in three cases and multiple unique TCRs were found in another patient. <i>TP53</i> mutation-specific T cells also recognized tumor cell lines bearing the appropriate human leukocyte antigen restriction element and <i>TP53</i> mutation, indicating these T cells could recognize processed and presented p53 neoantigens. PBL was a noninvasive source of T cells targeting <i>TP53</i> mutations for cell therapy and can provide a window into intratumoral p53 neoantigen immune responses.<i>See related commentary by Olivera et al., p. 1203</i>.