Enhancement of MHC-I Antigen Presentation via Architectural Control of pH-Responsive, Endosomolytic Polymer Nanoparticles

Abstract

Protein-based vaccines offer a number of important advantages over organism-based vaccines but generally elicit poor CD8(+) T cell responses. We have previously demonstrated that pH-responsive, endosomolytic polymers can enhance protein antigen delivery to major histocompatibility complex class I (MHC-I) antigen presentation pathways thereby augmenting CD8(+) T cell responses following immunization. Here, we describe a new family of nanocarriers for protein antigen delivery assembled using architecturally distinct pH-responsive polymers. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize linear, hyperbranched, and core-crosslinked copolymers of 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) that were subsequently chain extended with a hydrophilic N,N-dimethylacrylamide (DMA) segment copolymerized with thiol-reactive pyridyl disulfide (PDS) groups. In aqueous solution, polymer chains assembled into 25 nm micellar nanoparticles and enabled efficient and reducible conjugation of a thiolated protein antigen, ovalbumin. Polymers demonstrated pH-dependent membrane-destabilizing activity in an erythrocyte lysis assay, with the hyperbranched and cross-linked polymer architectures exhibiting significantly higher hemolysis at pH ≤ 7.0 than the linear diblock. Antigen delivery with the hyperbranched and cross-linked polymer architecture enhanced in vitro MHC-I antigen presentation relative to free antigen, whereas the linear construct did not have a discernible effect. The hyperbranched system elicited a four- to fivefold increase in MHC-I presentation relative to the cross-linked architecture, demonstrating the superior capacity of the hyperbranched architecture in enhancing MHC-I presentation. This work demonstrates that the architecture of pH-responsive, endosomolytic polymers can have dramatic effects on intracellular antigen delivery, and offers a promising strategy for enhancing CD8(+) T cell responses to protein-based vaccines.

RAFT Polymerization – Then and Now

“…The two cores (and a linear copolymer) were then used as macro-RAFT agents to control copolymerization of dimethyl acrylamide (DMA) and pyridyl disulfide methacrylamide (PDSMA) to produce star-nanogels (Scheme 22). This work (189) demonstrated that the architecture of pH-responsive, endosomolytic polymers can have a dramatic effect on intracellular antigen delivery, and indicated a promising strategy for enhancing CD8 + T cell responses to protein-based vaccines.…”

“…In a recent study on the preparation of a new family of nanocarriers for protein antigen delivery (189), two variants were exploited. In the first, a hyperbranched core was formed by copolymerization of BMA and 2-(N,N-diethylamino)ethyl methacrylate) (DEAEMA) was mediated by an "inimer" RAFT agent.…”

“…These will not be recounted in detail here. Significant developments have been made in electroactive and optoelectronic polymers (101) (organic semiconductors (202)(203)(204)(205), materials for organic light emitting diodes (204), photochromics (206)), the biomedical field (therapeutic delivery (184,(187)(188)(189)(207)(208)(209), surfaces (210,211) personal care (212)), and industrial applications (rheology control agents (213), surface functionalized membranes (214)) and many other areas.…”

Nanoparticles in Vaccine Delivery

“…These include peptide amphiphile micelles [9], pH responsive polymer-based nanoparticles [10], cationic liposomes [11], polysaccharide-based nanoparticles [12], and nanoparticles formed from biodegradable polymers such as p o l y l a c t i c -c o -g l y c o l i d e ( P L G A ) [ 1 3 -1 5 ] and polyanhydrides [16]. This theme issue includes a comprehensive review by Jewell and colleagues on the topic of harnessing biomaterials to engineer the lymph node microenvironment for immunity or tolerance [17].…”

“…Upon vaccination of mice with these micelles, a potent IgG1 antibody response was induced that was similar to responses obtained from co-administration of soluble peptide with two classical adjuvants. Stayton and colleagues report on the enhancement of MHC-I antigen presentation via architectural control of pH-responsive endosomolytic polymer nanoparticles [10]. In their study, increased MHC-I antigen presentation was observed in vitro with antigenloaded nanoparticles formulated from hyperbranched and cross-linked polymer structures compared to soluble antigen or antigen-loaded nanoparticles made from linear polymers.…”