Pattern recognition receptor agonists in pathogen vaccines mediate antitumor T-cell cross-priming

• Published in: Journal for immunotherapy of cancer Vol. 11; no. 7; p. e007198
• Main Authors: Aleynick, Mark, Svensson-Arvelund, Judit, Pantsulaia, Gvantsa, Kim, Kristy, Rose, Samuel A, Upadhyay, Ranjan, Yellin, Michael, Marsh, Henry, Oreper, Daniel, Jhunjhunwala, Suchit, Moussion, Christine Carine, Merad, Miriam, Brown, Brian D, Brody, Joshua D
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group Ltd 01.07.2023; BMJ Publishing Group LTD; BMJ Publishing Group
• Series: Original research
• Subjects: Adjuvants; Adjuvants, Immunologic; Animals; Antigen Presentation; Antigens; Cancer; CD8-Positive T-Lymphocytes; Cross-Priming; Cytokines; Dendritic Cells; Flow cytometry; Gene Editing; Genome editing; Humans; Immunization; Immunotherapy; Immunotherapy, Active; Mice; Oncolytic and Local Immunotherapy; Pathogens; Patients; Pattern recognition; Rabies; Statistical significance; Tumors; Vaccination; Vaccines; Variance analysis; Immunotherapy, Active; Dendritic Cells; Antigen Presentation; Adjuvants, Immunologic; Vaccination; Active; Immunotherapy; Immunologic
• ISSN: 2051-1426; 2051-1426
• DOI: 10.1136/jitc-2023-007198

BackgroundCancer immunotherapies are generally effective in patients whose tumors contain a priori primed T-cells reactive to tumor antigens (TA). One approach to prime TA-reactive T-cells is to administer immunostimulatory molecules, cells, or pathogens directly to the tumor site, that is, in situ vaccination (ISV). We recently described an ISV using Flt3L to expand and recruit dendritic cells (DC), radiotherapy to load DC with TA, and pattern recognition receptor agonists (PRRa) to activate TA-loaded DC. While ISV trials using synthetic PRRa have yielded systemic tumor regressions, the optimal method to activate DCs is unknown.MethodsTo discover optimal DC activators and increase access to clinical grade reagents, we assessed whether viral or bacterial components found in common pathogen vaccines are an effective source of natural PRRa (naPRRa). Using deep profiling (155-metric) of naPRRa immunomodulatory effects and gene editing of specific PRR, we defined specific signatures and molecular mechanisms by which naPRRa potentiate T-cell priming.ResultsWe observed that vaccine naPRRa can be even more potent in activating Flt3L-expanded murine and human DCs than synthetic PRRa, promoting cross-priming of TA-reactive T-cells. We developed a mechanistically diverse naPRRa combination (BCG, PedvaxHIB, Rabies) and noted more potent T-cell cross-priming than with any single naPRRa. The naPRRa triplet—as part of Flt3L-primed ISV—induced greater intratumoral CD8 T-cell infiltration, T-cells reactive to a newly defined tumorous neoantigen, durable tumor regressions.ConclusionsThis work provides rationale for the translation of pathogen vaccines as FDA-approved clinical-grade DC activators which could be exploited as immune-stimulants for early phase trials.