T cell priming by high avidity neoantigens in lymph nodes augments adoptive immunotherapy.

Adoptive transfer of T lymphocytes specific for tumor-associated neoantigens can elicit immunity against solid tumors in patients. However, how these antigens impact T cell function, effector differentiation, and persistence remains unclear. We examined how an identical CD8+ T cell product was shaped by melanoma expressing either a low-avidity tumor-associated antigen or high-avidity neoantigen, and kinetically profiled T cell differentiation in these two contexts across host tissues. High-avidity neoantigen expression was sufficient to activate naïve CD8+ T cells - leading to robust tumor regression and long-term protective immunity upon tumor rechallenge. Mechanistically, transferred naïve CD8+ T cells reacting to high-avidity neoantigen exhibited enhanced cytokine production, heightened effector function, and sustained persistence compared to the low-avidity wild-type tumors. Antitumor activity to these high-avidity tumors was preserved even in the absence of functional host T and B lymphocytes, and early lymph node trafficking was found to be essential for ACT efficacy. Expanded effector or stem-memory T cells were compared to the naïve pmel-1 T cell product. Stem-memory but not effector-memory cells exhibited similar antitumor efficacy and lymph node trafficking patterns to the naïve cells in mice with high-avidity neoantigen tumors. These findings highlight how differential tumor antigens shape divergent cellular fate and uncover a critical role of T cell trafficking in lymph nodes in shaping high-avidity neoantigen-specific antitumor responses.