Neoantigen-specific CD4+ T cells in human melanoma have diverse differentiation states and correlate with CD8+ T cell, macrophage, and B cell function.

CD4+ T cells that recognize tumor antigens are required for immune checkpoint inhibitor efficacy in murine models, but their contributions in human cancer are unclear. We used single-cell RNA sequencing and T cell receptor sequences to identify signatures and functional correlates of tumor-specific CD4+ T cells infiltrating human melanoma. Conventional CD4+ T cells that recognize tumor neoantigens express CXCL13 and are subdivided into clusters expressing memory and T follicular helper markers, and those expressing cytolytic markers, inhibitory receptors, and IFN-γ. The frequency of CXCL13+ CD4+ T cells in the tumor correlated with the transcriptional states of CD8+ T cells and macrophages, maturation of B cells, and patient survival. Similar correlations were observed in a breast cancer cohort. These results identify phenotypes and functional correlates of tumor-specific CD4+ T cells in melanoma and suggest the possibility of using such cells to modify the tumor microenvironment.

A therapeutic cancer vaccine delivers antigens and adjuvants to lymphoid tissues using genetically modified T cells.

Therapeutic vaccines that augment T cell responses to tumor antigens have been limited by poor potency in clinical trials. In contrast, the transfer of T cells modified with foreign transgenes frequently induces potent endogenous T cell responses to epitopes in the transgene product, and these responses are undesirable, because they lead to rejection of the transferred T cells. We sought to harness gene-modified T cells as a vaccine platform and developed cancer vaccines composed of autologous T cells modified with tumor antigens and additional adjuvant signals (Tvax). T cells expressing model antigens and a broad range of tumor neoantigens induced robust and durable T cell responses through cross-presentation of antigens by host DCs. Providing Tvax with signals such as CD80, CD137L, IFN-ß, IL-12, GM-CSF, and FLT3L enhanced T cell priming. Coexpression of IL-12 and GM-CSF induced the strongest CD4+ and CD8+ T cell responses through complimentary effects on the recruitment and activation of DCs, mediated by autocrine IL-12 receptor signaling in the Tvax. Therapeutic vaccination with Tvax and adjuvants showed antitumor activity in subcutaneous and metastatic preclinical mouse models. Human T cells modified with neoantigens readily activated specific T cells derived from patients, providing a path for clinical translation of this therapeutic platform in cancer.