Improved humoral immunity and protection against influenza virus infection with a 3D porous biomaterial vaccine

Abstract

New vaccine platforms that properly activate humoral immunity and generate neutralizing antibodies are required to combat emerging and re-emerging pathogens, including influenza virus. Biomaterial scaffolds with macroscale porosity have demonstrated tremendous promise in regenerative medicine where they have been shown to allow immune cell infiltration and subsequent activation, but whether these types of materials can serve as an immunization platform is unknown. We developed an injectable immunization platform that uses a slurry of antigen-loaded hydrogel microparticles that anneal to form a porous scaffold with high surface area for antigen uptake by infiltrating immune cells as the biomaterial degrades to maximize humoral immunity. Antigen-loaded-microgels elicited a robust cellular humoral immune response, with increased CD4+ T follicular helper (Tfh) cells and prolonged germinal center (GC) B cells comparable to the commonly used adjuvant, aluminum hydroxide (Alum). By simply increasing the weight fraction of polymer material, we enhanced material stiffness and further increased antigen-specific antibody titers superior to Alum. Vaccinating mice with inactivated influenza virus loaded into this more highly crosslinked formulation elicited a strong antibody response and provided better protection against a high dose viral challenge than Alum. Thus, we demonstrate that by tuning physical and chemical properties alone, we can enhance adjuvanticity and promote humoral immunity and protection against a pathogen, leveraging two different types of antigenic material: individual protein antigen and inactivated virus. The flexibility of the platform may enable design of new vaccines to enhance innate and adaptive immune cell programming to generate and tune high affinity antibodies, a promising approach to generate long-lasting immunity against specific pathogens.

A novel microporous biomaterial vaccine platform for long-lasting antibody mediated immunity against viral infection

“…IgG1 antibodies closely matched total IgG titers, confirming the type 2 biased as previously shown ( Supplemental Fig. 1 ) (27). Furthermore, temporal analysis of a single titration from each group demonstrated that while the anti-RBD IgG levels from Alum(S) were higher than PBS(S), VaxMAP(S) had consistently elevated antigen-specific antibodies compared to both groups ( Fig.…”

“…IgG1 antibodies closely matched total IgG titers, confirming the type 2 biased as previously shown (Supplemental Fig. 1) (27). Furthermore, temporal analysis of a single titration from each group demonstrated that while the anti-RBD IgG (which was not certified by peer review) is the author/funder.…”

“…The other solution contained a 7.5 mM dicysteine modified Matrix Metalloprotease (MMP) peptide substrate (Ac-GCRDGPQGIWGQDRCG-NH2) (Bachem). RGD, K-and Q-peptides were added for cell adhesion and secondary annealing as previously reported (23,(25)(26)(27)(28). The pre-prepared aqueous PEG-VS and MMP-peptide solutions were mixed in a 1:1 volume ratio, forming the "prehydrogel solution".…”

“…Early formulation of MAPs have shown the ability to elicit tissue regeneration by activating antigen-specific antibody responses in mice loaded with antigen (25). Proof of concept work showed that MAP loaded with immunogens can elicit antigen specific immunity and tuning hydrogel stiffness can serve an adjuvant role, enhancing antibody responses (27). However, given the need for microfluidic fabrication, with the necessity to incorporate antigenic material during manufacturing, the ability to develop the MAP as a tunable immunization platform for medical purposes was limited.…”

“…Recently, a new class of biomaterial scaffolds -granular hydrogelswere created with a hyper-porous geometry to allow for optimal cell infiltration while minimizing the host foreign body response (24). Microporous annealed particle (MAP) hydrogels are a flowable suspension of concentrated viscoelastic microspheres 'building blocks' that transition in situ to form a robust porous scaffold (23,(25)(26)(27). Significantly more immune cells can be exposed to the loaded antigen as they migrate through the hyper-porous space around annealed MAP building blocks, and as the scaffold containing the antigen slowly degrades, antigen will be released from the scaffold.…”