Poly(2‐propylacrylic acid)/poly(lactic‐co‐glycolic acid) blend microparticles as a targeted antigen delivery system to direct either CD4⁺ or CD8⁺ T cell activation

Abstract

Poly(lactic‐co‐glycolic acid) (PLGA) based microparticles (MPs) are widely investigated for their ability to load a range of molecules with high efficiency, including antigenic proteins, and release them in a controlled manner. Micron‐sized PLGA MPs are readily phagocytosed by antigen presenting cells, and localized to endosomes. Due to low pH and digestive enzymes, encapsulated protein cargo is largely degraded and processed in endosomes for MHC‐II loading and presentation to CD4+ T cells, with very little antigen delivered into the cytosol, limiting MHC‐I antigenic loading and presentation to CD8+ T cells. In this work, PLGA was blended with poly(2‐propylacrylic acid) (PPAA), a membrane destabilizing polymer, in order to incorporate an endosomal escape strategy into PLGA MPs as an easily fabricated platform with diverse loading capabilities, as a means to enable antigen presentation to CD8+ T cells. Ovalbumin (OVA)‐loaded MPs were fabricated using a water‐in‐oil double emulsion with a 0% (PLGA only), 3 and 10% PPAA composition. MPs were subsequently determined to have an average diameter of 1 µm, with high loading and a release profile characteristic of PLGA. Bone marrow derived dendritic cells (DCs) were then incubated with MPs in order to evaluate localization, processing, and presentation of ovalbumin. Endosomal escape of OVA was observed only in DC groups treated with PPAA/PLGA blends, which promoted high levels of activation of CD8+ OVA‐specific OT‐I T cells, compared to DCs treated with OVA‐loaded PLGA MPs which were unable activate CD8+ T cells. In contrast, DCs treated with OVA‐loaded PLGA MPs promoted OVA‐specific OT‐II CD4+ T cell activation, whereas PPAA incorporation into the MP blend did not permit CD4+ T cell activation. These studies demonstrate PLGA MP blends containing PPAA are able to provide an endosomal escape strategy for encapsulated protein antigen, enabling the targeted delivery of antigen for tunable presentation and activation of either CD4+ or CD8+ T cells.

Poly(propylacrylic acid)-peptide nanoplexes as a platform for enhancing the immunogenicity of neoantigen cancer vaccines

“…While most particulate vaccines have leveraged physicochemical (e.g., size, surface chemistry) or formulation properties (e.g., co-encapsulation of an adjuvant) to harness endogenous mechanisms of cross-presentation by specific DC subsets [22], another promising strategy has been to design antigen carriers that exploit endosomal escape mechanisms to “short circuit” endo/lysosomal antigen trafficking and actively enhance delivery of antigenic cargo to the cytosol for processing via the classical MHC-I presentation pathway [27–30]. One such carrier with pH-dependent membrane destabilizing activity is poly(propyl acrylic acid) (pPAA), a linear amphiphilic polyanion with a pKa of 6.7 that has been previously explored as a carrier to enhance cytosolic delivery of protein antigens and peptide therapeutics [31–35]. Inspired by the simplicity, speed, and scalability achieved via electrostatic self-assembly of polyplexes used commonly in nucleic acid-based vaccines [36, 37], we postulated that peptide antigen-loaded nanoparticles with endosome-destabilizing activity could be generated through facile mixing of polyanionic pPAA and peptide antigens synthesized with a cationic oligolysine tail (Fig.…”

Engineering immunomodulatory biomaterials for type 1 diabetes

“…Applying the wealth of knowledge gained from the combination of biomaterial systems with metabolically active insulin for improved glucose control 76 , particle platforms could be designed for the sustained release of T1D autoantigens to generate long-lasting antigenspecific tolerance. Moreover, nano-or microparticle delivery can modulate antigen processing and presentation by APCs 77 . According to traditional immunological paradigms, antigen taken up by endocytosis is processed and presented on MHC-II molecules to CD4 + T-cells.…”

“…Microparticles of different size encapsulating distinct factors can serve as a multipronged platform to target and modulate specific immune cell subsets (Fig 1b) 77 . For example, encapsulation of a dendritic cell chemokine, multiple pro-tolerogenic factors, and a T1Dantigen into distinct microparticles and subsequent administration in NOD mice 96 prevents diabetes onset 96 .…”

At the bench: Engineering the next generation of cancer vaccines

“…These strategies are most commonly used with liposomal formulations, in which lipids are coformulated with endosomolytic polymers or cell penetrating peptides or proteins . Blends of PLGA and endosomolytic polymers have also been used to enhance antigen cross‐presentation . Another strategy involves inclusion of photosensitizing molecules into a vaccine delivery vehicle, which facilitates light triggered in situ generation of ROS species for endosomal membrane destabilization following particle uptake .…”