Enhancement of subunit vaccine delivery with zinc-carnosine coordination polymer through the addition of mannan.

Vaccines represent a pivotal health advancement for preventing infection. However, because carrier systems with repeated administration can invoke carrier-targeted immune responses that diminish subsequent immune responses (e.g., PEG antibodies), there is a continual need to develop novel vaccine platforms. Zinc carnosine microparticles (ZnCar MPs), which are composed of a one-dimensional coordination polymer formed between carnosine and the metal ion zinc, have exhibited efficacy in inducing an immune response against influenza. However, ZnCar MPs' limited suspendability hinders clinical application. In this study, we address this issue by mixing mannan, a polysaccharide derived from yeast, with ZnCar MPs. We show that the addition of mannan increases the suspendability of this promising vaccine formulation. Additionally, since mannan is an adjuvant, we illustrate that the addition of mannan increases the antibody response and T cell response when mixed with ZnCar MPs. Mice vaccinated with mannan + OVA/ZnCar MPs had elevated serum IgG and IgG1 levels in comparison to vaccination without mannan. Moreover, in the mannan + OVA/ZnCar MPs vaccinated group, mucosal washes demonstrated increased IgG, IgG1, and IgG2c titers, and antigen recall assays showed enhanced IFN-γ production in response to MHC-I and MHC-II immunodominant peptide restimulation, compared to the vaccination without mannan. These findings suggest that the use of mannan mixed with ZnCar MPs holds potential for subunit vaccination and its improved suspendability further promotes clinical translation.

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

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.

Metal-Organic Coordination Polymer for Delivery of a Subunit Broadly Acting Influenza Vaccine.

A zinc-carnosine (ZnCar) metal-organic coordination polymer was fabricated in biologically relevant N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer for use as a vaccine platform. In vitro, ZnCar exhibited significantly less cytotoxicity than a well-established zeolitic imidazolate framework (ZIF-8). Adsorption of CpG on the ZnCar surface resulted in enhanced innate immune activation compared to soluble CpG. The model antigen ovalbumin (OVA) was encapsulated in ZnCar and exhibited acid-sensitive release in vitro. When injected intramuscularly on days 0 and 21 in C57BL/6 mice, OVA-specific serum total IgG and IgG1 were significantly greater in all groups with ZnCar and antigen compared to soluble controls. Th1-skewed IgG2c antibodies were significantly greater in OVA and CpG groups delivered with ZnCar for all time points, regardless of whether the antigen and adjuvant were co-formulated in one material or co-delivered in separate materials. When broadly acting Computationally Optimized Broadly Reactive Antigen (COBRA) P1 influenza hemagglutinin (HA) was ligated to ZnCar via its His-tag, significantly greater antibody levels were observed at all time points compared to soluble antigen and CpG. ZnCar-formulated antigen elicited increased peptide presentation to B3Z T cells in vitro and production of IL-2 after ex vivo antigen recall of splenocytes isolated from vaccinated mice. Overall, this work displays the formation of a zinc-carnosine metal-organic coordination polymer that can be applied as a platform for recombinant protein-based vaccines.