In situ vaccination via tissue-targeted cDC1 expansion enhances the immunogenicity of chemoradiation and immunotherapy
Brandon Lam, … , Chien-Fu Hung, T.-C. Wu
Brandon Lam, … , Chien-Fu Hung, T.-C. Wu
Published November 2, 2023
Citation Information: J Clin Invest. 2024;134(1):e171621. https://doi.org/10.1172/JCI171621.
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Research Article Immunology

In situ vaccination via tissue-targeted cDC1 expansion enhances the immunogenicity of chemoradiation and immunotherapy

Abstract

Even with the prolific clinical use of next-generation cancer therapeutics, many tumors remain unresponsive or become refractory to therapy, creating a medical need. In cancer, DCs are indispensable for T cell activation, so there is a restriction on cytotoxic T cell immunity if DCs are not present in sufficient numbers in the tumor and draining lymph nodes to take up and present relevant cancer antigens. To address this bottleneck, we developed a therapeutic based on albumin fused with FMS-related tyrosine kinase 3 ligand (Alb-Flt3L) that demonstrated superior pharmacokinetic properties compared with Flt3L, including significantly longer half-life, accumulation in tumors and lymph nodes, and cross-presenting-DC expansion following a single injection. We demonstrated that Alb-Flt3L, in combination with standard-of-care chemotherapy and radiation therapy, serves as an in situ vaccination strategy capable of engendering polyclonal tumor neoantigen–specific immunity spontaneously. In addition, Alb-Flt3L–mediated tumor control synergized with immune checkpoint blockade delivered as anti–PD-L1. The mechanism of action of Alb-Flt3L treatment revealed a dependency on Batf3, type I IFNs, and plasmacytoid DCs. Finally, the ability of Alb-Flt3L to expand human DCs was explored in humanized mice. We observed significant expansion of human cross-presenting-DC subsets, supporting the notion that Alb-Flt3L could be used clinically to modulate human DC populations in future cancer therapeutic regimens.

Authors

Brandon Lam, Yu Jui Kung, John Lin, Ssu-Hsueh Tseng, Hsin-Fang Tu, Claire Huang, Brandon Lee, Esteban Velarde, Ya Chea Tsai, Rafael Villasmil, Sung Taek Park, Deyin Xing, Chien-Fu Hung, T.-C. Wu

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Figure 1

Alb-Flt3L has favorable pharmacokinetic properties and induces superior DC expansion compared with Flt3L.

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Alb-Flt3L has favorable pharmacokinetic properties and induces superior ...
C57BL/6 mice were inoculated with 2 × 105 TC-1 tumor cells and utilized to determine tissue localization and biodistribution once tumors reached approximately 0.5 cm in diameter. Alexa Fluor 647–labeled Alb-Flt3L or Flt3L was injected intravenously at equimolar amounts. Four, 24, and 48 hours after injection, mice were euthanized and tissues were imaged for fluorescent activity using IVIS. (A) Representative images of lymph nodes (inguinal, axillary, and brachial) obtained from mice as described and kinetics curves showing average radiance at the indicated time points (n = 5). (B) Representative images of tumors taken from mice as described and kinetics curves showing average radiance at the indicated time points. In A and B: top image, Alb-Flt3L; middle image, Flt3L; bottom image, PBS control (n = 5). (C) Half-life of Alb-Flt3L or Flt3L. Mice were injected with Alb-Flt3L or Flt3L at equimolar amounts. Blood was collected at the indicated time points and serum was separated (n = 3). Anti-Flt3L ELISA was performed to determine the amount of Alb-Flt3L or Flt3L remaining in circulation. Curves show detected levels and half-life (t1/2) calculated by curve fit. To explore kinetics of DC expansion in vivo, C57BL/6 mice were injected with either Flt3L or Alb-Flt3L. Mice were euthanized and spleens were collected on the indicated days. Cells from the spleens were used for flow cytometry. (D–F) Representative gating, percentage frequency, and counts respectively of (D) cDC1s, (E) cDC2s, and pDCS (F) (n = 3). To assay in vivo expansion of DCs in diverse conditions, WT, FcRn–/–, or Batf3–/– C57BL/6 mice were injected with Alb-Flt3L, Flt3L, or vehicle control (naive). Five days later, mice were euthanized and splenocytes were analyzed by flow cytometry. (G–I) Frequency of (G) cDC1s, (H) cDC2s, or (I) pDCs following treatment of the indicated mice with the indicated condition (n = 5). Significance determined using 2-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.