Zinc Carnosine Metal–Organic Coordination Polymer as a Potent Broadly Active Influenza Vaccine Platform with In Vitro Shelf-Stability

Abstract

Current seasonal influenza vaccines are limited in that they need to be reformulated every year in order to account for the constant mutation of the virus. Hemagglutinin (HA) immunogens have been developed using a computationally optimized broadly reactive antigen (COBRA) methodology, which are able to elicit an antibody response that neutralizes antigenically distinct influenza strains; however, subunit proteins are not immunogenic enough on their own to generate a substantial immune response. Due to this, different delivery strategies and adjuvants can be used to improve immunogenicity. Recently, we reported a new coordination polymer composed of the dipeptide carnosine and zinc (ZnCar) that is able to deliver protein antigens along with CpG to generate a potent immune response. In the present work, ZnCar was used to deliver the COBRA HA immunogen Y2 and the adjuvant CpG. We incorporated Y2 into ZnCar using two different methods to assess which would be the most immunogenic. Mice vaccinated with Y2 and CpG complexed with ZnCar showed an improved humoral and cellular response when compared to mice vaccinated with soluble Y2 and CpG. Further, we demonstrate in vitro that when Y2 and CpG are coordinated with ZnCar, they are protected from degradation at 40 °C for 3 months or 24 °C for 6 months. Overall, ZnCar shows promise as a delivery vehicle for subunit vaccines, given its superior immunogenicity and in vitro storage stability.

Clinical and Preclinical Methods of Heat-Stabilization of Human Vaccines

“…55,56 Interestingly, Hendy et al show with a zinc-carnosine complexation polymer that incorporates the protein antigen at the time of formation results in reduced thermostability compared to protein added after the polymer is formed, with the protein complexing to the zinc via its HIStag. 52 This would imply that encapsulation is not required for heat-stability for this biomineralization method. Biomineralization is a nascent approach to heat-stable vaccines and certainly will continue to grow in exciting ways as the field progresses.…”

“…In some cases, crystallization sites have been added to the vaccine element (e.g., virus) to facilitate the encapsulation of the biologic . A popular approach is the use of metal and organic coordination polymers. − These platforms form a polymer comprised of an inorganic metal linked with an organic (usually dipeptide) linker. They can form 1D or 2D and 3D structures (Figure ) with 2D and 3D structures referred to as metal–organic frameworks (MOFs). , Interestingly, Hendy et al show with a zinc-carnosine complexation polymer that incorporates the protein antigen at the time of formation results in reduced thermostability compared to protein added after the polymer is formed, with the protein complexing to the zinc via its HIS-tag .…”

“…Synthesized by mixing a ZnCar suspension with an aliquot of HA, CpG, or COBRA Y2 to promote adsorption. Reprinted with permission from ref . Copyright 2023 American Chemical Society.…”