Hydrogel Matrix for In Vivo Expansion of Tumor-Specific T cells

Introduction:: T cell-based immunotherapies such as chimeric antigen receptor T cell therapy (CAR T), have seen some clinical success; however, these therapies are still currently limited to a select few cancer types and have price tags that further limit accessibility for patients. Here, we create an injectable biomaterial-based platform for the in vivo activation of naïve, antigen-specific T cells, removing the need for expensive and lengthy ex vivo expansion steps. The matrix provides both structural and molecular cues to activate naïve T cells, and works in concert with the host immune system to create a robust anti-tumor response.


Materials and Methods:: Thiol-modified HA is cross-linked with PEDGA in the presence of thiol-modified signals 1 (here, KbOVA) and 2 (anti CD28)³. The cross-linked gel is passed through a mesh to form microparticles (MPs) (Fig. 1A). MPs are either plated with naïve B6 CD8+ T cells in vitro or MPs are mixed with naïve B6 CD8+ T cells and injected subcutaneously into mice. On day 9, cells harvested from the in vitro and in vivo expansions to analyze for enrichment of antigen-specific cells (Fig. 1A and 1B). MPs were also tested therapeutic tumor model, in which B16-OVA tumor cells were injected on one flank on day 0 and naïve B5 CD8+ T cells and MPs were injected on the opposite flank on day 6. Survival was monitored (Fig. 1D).


Results, Conclusions, and Discussions:: To test the ability of MPs to expand antigen-specific cells both in vitro and in vivo, we incubated naïve B6 CD8+ T cells with MPs expressing KbOVA, aCD28, and IL2, either in a tissue culture plate or in a subcutaneous injection. By day 9, we can detect significant expansion of OVA-specific CD8+ T cells both in vitro and in vivo (Fig. 1A, B). Interestingly, in vivo expanded cells showed even higher (6-fold) enrichment for antigen-specific cells compared to in vitro expanded cells. We hypothesize that the injectable MPs create a dynamic space that develops into a lymph-node mimicking microenvironment that allows cells to benefit from auto- and para-crine signaling within the T cell microenvironment (Fig. 1C). To test the therapeutic efficacy of this platform, B16-OVA tumor cells were injected on one flank on day 0 and naïve B56 CD8+ T cells and MPs were injected on the opposite flank on day 6, with and without immune checkpoint blockade. MP treatment alone extended survival in this tumor model, and the addition of anti-PD1 further increased this effect (Figure 1D).





Along with other recent translational advances, the MP-based scaffold for de novo, in vivo antigen-specific T cell responses has the potential to make immunotherapy more widely accessible to patients. aLN platforms can inspire new studies to enrich our understanding of the immunological functions of T cells, the mechanism of immune niche formation, and the interactions between immune cells and biomaterials. These studies will also provide insights into new strategies to combat a broader range of medical conditions such as autoimmune disorders, infectious diseases, and tissue remodeling.


Acknowledgements (Optional): : NKL would like to thank everyone in the Mao, Schneck, and Spangler labs for their help. Special thank you to John W. Hickey for his training and endless support. Finally, this work was possible thanks to our funding sources from the NIH and NSF.


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