Polyanhydride Nanoparticles Induce Low Inflammatory Dendritic Cell Activation Resulting in CD8⁺ T Cell Memory and Delayed Tumor Progression

Ross Darling,¹ Sujata Senapati,² John Christiansen,¹ Luman Liu,² Amanda E Ramer-Tait,³ Balaji Narasimhan,^2,4 Michael Wannemuehler<sup>1,4

1</sup>Department of Veterinary Microbiology and Preventative Medicine, Iowa State University, Ames, IA, USA; ²Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, USA; ³Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, USA; ⁴Nanovaccine Institute, Iowa State University, Ames, IA, USA

Correspondence: Michael Wannemuehler; Balaji Narasimhan Email mjwannem@iastate.edu; nbalaji@iastate.edu

Introduction: Adjuvants and immunotherapies designed to activate adaptive immunity to eliminate infectious disease and tumors have become an area of interest aimed at providing a safe and effective strategy to prevent or eliminate disease. Existing approaches would benefit from the development of immunization regimens capable of inducing efficacious cell-mediated immunity directed toward CD8⁺ T cell-specific antigens. This goal is critically dependent upon appropriate activation of antigen-presenting cells (APCs) most notably dendritic cells (DCs). In this regard, polyanhydride particles have been shown to be effectively internalized by APCs and induce activation.
Methods: Here, a prophylactic vaccine regimen designed as a single-dose polyanhydride nanovaccine encapsulating antigen is evaluated for the induction of CD8⁺ T cell memory in a model system where antigen-specific protection is restricted to CD8⁺ T cells. Bone marrow-derived dendritic cells (BMDCs) are used as an in vitro model system to evaluate the magnitude and phenotype of APC activation. Primary DCs, particularly those with described ability to activate CD8⁺ T cells, are also evaluated for their in vitro responses to polyanhydride nanoparticles.
Results: Herein, polyanhydride nanoparticles are shown to induce potent in vitro upregulation of costimulatory molecules on the cell surface of BMDCs. In contrast to the classically used TLR agonists, nanoparticles did not induce large amounts of pro-inflammatory cytokines, did not induce characteristic metabolic response of DCs, nor produce innate antimicrobial effector molecules, such as nitric oxide (NO). The polyanhydride nanovaccine results in protective CD8⁺ T cell responses as measured by inhibition of tumor progression and survival.
Discussion: Together, these results suggest that the use of a polyanhydride-based nanovaccine can be an effective approach to inducing antigen-specific CD8⁺ T cell memory by providing antigen delivery and DC activation while avoiding overt inflammatory responses typically associated with traditional adjuvants.

Keywords: nanovaccine, metabolism, nitric oxide, T cell memory, inflammation