Immunological Properties of Protein–Polymer Nanoparticles

Abstract

The covalent attachment of polymers to the surface of proteins and nanoparticles has been widely employed in the development of biomedical platforms capable of delaying or diminishing immune surveillance. The most widely employed polymer for these applications has been poly­(ethylene glycol) (PEG), yet recent evidence has suggested that other polymer architectures and compositions provide significantly better in vitro and in vivo properties of protein–polymer hybrid materials. Moreover, few direct comparisons of PEG to these polymers have been reported. Here we describe the assembly and characterization of a series of polymer conjugates of a representative immunogenic viruslike particle (VLP) using (poly­(oligo­(ethylene glycol) methacrylate), poly­(methacrylamido glucopyranose), and PEG, and an investigation of their ability to shield the protein from antibody recognition as a function of polymer loading density, chain length, architecture, and conjugation site. Increasing chain length and loading density were both found to significantly diminish antibody recognition of the VLP conjugates; the conformation adopted by different polymer architectures was also found to greatly influence antibody recognition. A direct comparison of these conjugates to PEGylated VLPs in vivo showed that all formulations gave rise to similar antibody titers that were significantly diminished relative to unmodified particles. Interestingly, the quality of the antibody response was impacted by the properties of the conjugate, with differences in observed affinity and avidity suggesting a complex dependence on loading density, chain length, and architecture.

Antigen- and scaffold-specific antibody responses to protein nanoparticle immunogens

“… 55 As for PEGylation, an approach called “protect, modify, deprotect” used poly-ethylene glycol (PEG) to focus immune responses to the conserved stem region of HA and boost cross-reactive antibody titers: antibody is first bound to the desired epitope, the immunogen is non-specifically PEGylated to reduce immunogenicity of all other surfaces, and then the antibody is removed to expose the desired epitope. 56 Although much work has focused on masking antigens, protein nanoparticles have also been glycosylated 57 and PEGylated (e.g., cowpea mosaic virus, 58 , 59 adenovirus, 60 , 61 , 62 ferritin, 63 dihydrolipoamide acetyltransferase complex, 64 and Qβ 65 ), but not in the context of a displayed antigen. Therefore, it remains unknown if sterically hindering B cell receptor (BCR) accessibility via scaffold masking can provide an antigen-specific immunofocusing benefit.…”

Integrating Biomaterials and Immunology to Improve Vaccines Against Infectious Diseases

“…One well-tested example of chemical conjugation of a recombinant antigen to the surface of a preassembled particle is the VLP formed from the capsid protein of the bacteriophage Qβ. [181][182][183] The amino group of the surface-exposed lysine residues on Qβ are modified with a bi-functional chemical cross-linker and subsequently reacted with a target antigen engineered to contain a reactive cysteine residue. surface.…”

“…The authors showed that immunization with VLPs displaying a single B-cell epitope minimally reduces Zika virus infection, whereas immunization with a mixture of VLPs displaying a combination of B-cell epitopes elicited antibodies that neutralized infections. 182 Hong et al later described the mechanism of this strong antibody response. The group found that the repetitive display of antigens on VLPs enhance vaccine interaction with B-cell receptors.…”

“…Display of antigens on recombinant VLPs can be achieved by either chemical conjugation or genetic fusion to the viral coat protein. One well-tested example of chemical conjugation of a recombinant antigen to the surface of a preassembled particle is the VLP formed from the capsid protein of the bacteriophage Qβ. − The amino group of the surface-exposed lysine residues on Qβ are modified with a bifunctional chemical cross-linker and subsequently reacted with a target antigen engineered to contain a reactive cysteine residue . The resulting VLP products present repetitive arrays of the target epitope on the particle surface.…”

Single-Point Mutations in Qβ Virus-like Particles Change Binding to Cells

“…Virus-like particles (VLPs) are hollow protein nanomaterials that hold great promise for applications in various fields ranging from materials science − to medicine. − VLPs are particularly attractive scaffolds for the generation of novel materials due to their genetic malleability − as well as their robust tolerance to extremes in temperature, pH, and solvent composition, − which allows for a diverse array of chemical modifications to be installed. − Combined with the fact that their base protein structure is demonstrably biocompatible, , it is unsurprising that VLPs have received substantial focus in the development of targeted therapeutics. ,− …”