# Tim-3-targeted vaccines overcome tumor immunosuppression and reduce cDC1 dependence to elicit potent anti-tumor immunity

## TL;DR

A new type of cancer vaccine that targets Tim-3 can activate strong immune responses even when key immune cells are missing or dysfunctional.

## Contribution

Tim-3-targeted vaccines can elicit potent anti-tumor immunity without strict dependence on cDC1s.

## Key findings

- Tim-3-targeted vaccines deliver antigens to both cDC1s and cDC2s, enhancing cross-priming in tumor-bearing and DC-impaired mice.
- A single dose of Tim-3–neoantigen vaccine eradicated large tumors in a CD8-dependent manner.
- Tim-3-targeted vaccines retain anti-tumor activity even in the absence of cDC1s.

## Abstract

The limited efficacy of DC vaccines and immune checkpoint blockade (ICB) partly reflects the scarcity and dysfunction of cDC1s in tumors. Tim-3-targeted vaccines deliver antigens to Tim-3+ antigen-presenting cells, including both cDC1s and cDC2s, and elicit robust, durable CD8 T cell responses. Tim-3-targeted vaccination enhances cross-priming in tumor-bearing and DC-impaired mice and counteracts tumor- and DC-mediated immunosuppression. Although cDC1 deficiency reduces CD8 T cell responses, Tim-3-targeted vaccines retain anti-tumor activity when cDC1s are genetically absent, demonstrating that cDC1s contribute to but are not strictly required for efficacy. A single dose of Tim-3–neoantigen vaccine eradicated large tumors in a CD8-dependent manner, offering a strategy to overcome immunotherapy barriers and expand treatment options for patients unresponsive to current therapies.

Conventional type 1 dendritic cells (cDC1s) are specialized for cross-presenting tumor antigens and determining the efficacy of immunotherapies, including immune checkpoint blockade and adoptive cell therapy. However, their rarity and tumor-induced dysfunction severely limit CD8 T cell priming and represent a central bottleneck to therapeutic efficacy. While strategies such as anti–DEC-205-mediated antigen delivery and Flt3L-driven DC expansion can enhance host DC function, their reliance on functional cDC1s remains a significant constraint. We developed Tim-3-targeted vaccines by conjugating tumor antigens or neoantigens to anti–Tim-3 antibodies. These vaccines delivered antigens to both cDC1s and cDC2s, and elicited robust, durable CD8 T cell responses. Remarkably, Tim-3-targeted vaccines endowed cDC2s with efficient cross-presentation capacity that matched that of cDC1s. In tumor-bearing mice or in CD11c-β-cateninactive mice, which model β-catenin-driven DC dysfunction, Tim-3-targeted vaccination restored cross-priming and counteracted tumor- and DC-mediated immunosuppression. In Batf3−/− mice lacking cDC1s, anti-Tim-3-based vaccines still elicited significant CD8 T cell cross-priming and tumor control—albeit both were reduced compared to wild-type mice— demonstrating that cDC1s contribute to but are not essential for Tim-3-targeted vaccine–induced CD8 T cell priming and anti-tumor efficacy. Strikingly, a single dose of anti-Tim-3–neoantigen vaccination eradicated large established MC38 tumors in a CD8 T cell–dependent manner. Together, these data identify Tim-3-targeted vaccines as a next-generation cancer vaccine platform that broadens DC engagement, reduces reliance on cDC1s, and overcomes tumor- and DC-mediated immunosuppression, addressing key limitations of current DC-based cancer vaccines.