Utilizing nanotechnology to improve the activation of CD8 T cells for cancer immunotherapy

The immune system can be manipulated to recognize and eliminate cancerous cells. Many of these manipulations aim to increase the proliferation and activation of tumor-targeting cytotoxic CD8+ T cells through direct stimulation or attenuation of immuno-inhibitory checkpoint pathways. Here, I use nanotechnology to develop platforms that can enhance and/or target immuno-stimulatory properties by controlling the kinetics, costimulation, and nanoscale delivery of immunotherapies. I first developed a nanoparticle that converts inhibitory signals in the tumor microenvironment to T cell stimulatory signals. By tethering checkpoint blockade and co-stimulatory molecules to a single platform, I made particles that physically link tumor cells and T cells while inhibiting checkpoint activity and activating T cells. These particles delayed or eliminated tumor growth in several murine models at doses 10-100x less than soluble inhibitory and co-stimulatory molecules and resulted in a systemic memory immune response while localizing the nanoparticles to the tumor microenvironment. Next, I developed a modified type of artificial antigen presenting cell (aAPC) that boosts CD8+ T cell activation for adoptive cell transfer. T cell signaling components were separated onto distinct superparamagnetic nanoparticles and activation was induced by clustering the particles with a magnetic field. This platform streamlined the application of various combinations of co-stimulatory molecules together with a single antigen-specific receptor to increase the expansion of antigen-specific T cells and extend their persistence in vivo. Finally, I developed more effective biodegradable aAPC by modifying the particle material and through combination with checkpoint blockade. Biodegradable aAPC synergized with anti-PD-1 checkpoint blockade to delay the growth of established murine melanoma. A new type of polymeric aAPC also activated antigen-specific CD8+ T cells at doses 100x less than previous particle formulations

Separating T Cell Targeting Components onto Magnetically Clustered Nanoparticles Boosts Activation

T cell activation requires the coordination of a variety of signaling molecules including T cell receptor-specific signals and costimulatory signals. Altering the composition and distribution of costimulatory molecules during stimulation greatly affects T cell functionality for applications such as adoptive cell therapy (ACT), but the large diversity in these molecules complicates these studies. Here, we develop and validate a reductionist T cell activation platform that enables streamlined customization of stimulatory conditions. This platform is useful for the optimization of ACT protocols as well as the more general study of immune T cell activation. Rather than decorating particles with both signal 1 antigen and signal 2 costimulus, we use distinct, monospecific, paramagnetic nanoparticles, which are then clustered on the cell surface by a magnetic field. This allows for rapid synthesis and characterization of a small number of single-signal nanoparticles which can be systematically combined to explore and optimize T cell activation. By increasing cognate T cell enrichment and incorporating additional costimulatory molecules using this platform, we find significantly higher frequencies and numbers of cognate T cells stimulated from an endogenous population. The magnetic field-induced association of separate particles thus provides a tool for optimizing T cell activation for adoptive immunotherapy and other immunological studies

Dual Targeting Nanoparticle Stimulates the Immune System To Inhibit Tumor Growth

We describe the development of a nanoparticle platform that overcomes the immunosuppressive tumor microenvironment. These nanoparticles are coated with two different antibodies that simultaneously block the inhibitory checkpoint PD-L1 signal and stimulate T cells <i>via</i> the 4-1BB co-stimulatory pathway. These “immunoswitch” particles significantly delay tumor growth and extend survival in multiple <i>in vivo</i> models of murine melanoma and colon cancer in comparison to the use of soluble antibodies or nanoparticles separately conjugated with the inhibitory and stimulating antibodies. Immunoswitch particles enhance effector-target cell conjugation and bypass the requirement for <i>a priori</i> knowledge of tumor antigens. The use of the immunoswitch nanoparticles resulted in an increased density, specificity, and <i>in vivo</i> functionality of tumor-infiltrating CD8+ T cells. Changes in the T cell receptor repertoire against a single tumor antigen indicate immunoswitch particles expand an effective set of T cell clones. Our data show the potential of a signal-switching approach to cancer immunotherapy that simultaneously targets two stages of the cancer immunity cycle resulting in robust antitumor activity