Structural Alterations of Antigens at the Material Interface: An Early Decision Toolbox Facilitating Safe-by-Design Nanovaccine Development

Abstract

Nanomaterials have found extensive interest in the development of novel vaccines, as adjuvants and/or carriers in vaccination platforms. Conjugation of protein antigens at the particle surface by non-covalent adsorption is the most widely used approach in licensed particulate vaccines. Hence, it is essential to understand proteins’ structural integrity at the material interface in order to develop safe-by-design nanovaccines. In this study, we utilized two model proteins, the wild-type allergen Bet v 1 and its hypoallergenic fold variant (BM4), to compare SiO2 nanoparticles with Alhydrogel® as particulate systems. A set of biophysical and functional assays including circular dichroism spectroscopy and proteolytic degradation was used to examine the antigens’ structural integrity at the material interface. Conjugation of both biomolecules to the particulate systems decreased their proteolytic stability. However, we observed qualitative and quantitative differences in antigen processing concomitant with differences in their fold stability. These changes further led to an alteration in IgE epitope recognition. Here, we propose a toolbox of biophysical and functional in vitro assays for the suitability assessment of nanomaterials in the early stages of vaccine development. These tools will aid in safe-by-design innovations and allow fine-tuning the properties of nanoparticle candidates to shape a specific immune response.

Surface Functionalization of Silica Nanoparticles: Strategies to Optimize the Immune-Activating Profile of Carrier Platforms

“…As the initial step, the SiNPs and functionalized SiNPs were characterized for their primary size and morphology. The TEM images of the particles displayed a uniform spherical shape with a primary size of 51.02 ± 3.80 nm (SiNP), 47.31 ± 4.72 nm (SiNP_A) and 50.42 ± 4.57 nm (SiNP_M) ( Figure 1 ) [ 22 ].…”

“…Allergens are known to form a stable corona on the particle interface [ 43 ]. We have previously demonstrated that silica nanoparticles both mesoporous and nonporous adsorb Bet v 1, effectively forming a biocorona [ 22 , 44 ]. The efficiency of binding was determined by SDS-PAGE and BCA assay.…”

“…Dendritic cells derived from human peripheral blood monocytes, termed monocyte-derived dendritic cells (moDCs) were used as APCs to study immune effects. We have previously observed alterations in the antigen processing patterns when Bet v 1 was conjugated to SiNPs due to the structural alteration of the protein at the nanomaterial interface [ 22 ]. Thus, the immune effects of the particles with and without conjugation to Bet v 1 (the model protein) were also explored here.…”

Immunotoxicity of nanomaterials in health and disease: Current challenges and emerging approaches for identifying immune modifiers in susceptible populations

“…Protein adsorption onto the NM surface can favor conformational changes in the protein, thereby imposing destabilization of the native protein fold, reducing their thermal and pH stability and eventually leading to protein denaturation. Allergens adsorbed onto the surface of amorphous silica NPs have been reported to induce changes in the fold stability, especially in the alpha‐helical structures of Bet v 1 (the major birch pollen allergen), thereby altering the immunological response (L. Johnson et al, 2021 ), while the formation of the tubulin protein corona on the surface of titanium dioxide (TiO 2 ) NPs imposed an inhibitory effect on tubulin polymerization, an important step in cell division. The interaction with NPs altered the folding of both tubulin and microtubule proteins eliciting functional alterations (Gheshlaghi et al, 2008 ).…”

Mechanistic insights into silica nanoparticle–allergen interactions on antigen presenting cell function in the context of allergic reactions

“…In general, when allergenic proteins bind to nanoparticles, this can induce structural alterations. 21,22 In addition, they may bind in a non-randomized manner and, thus, selectively hide or expose allergenic epitopes on their surface. 23,24 Consequently, their biological effects may change, increasing or decreasing the immune response towards them.…”