Gene Gun-delivered RNA vaccines.

PROJECT SUMMARY COVID-19 launched mRNA vaccines to the forefront as the most effective and rapid strategy to respond to the pandemic. mRNA vaccines require formulation in lipid nanoparticles (LNPs) to protect the mRNA from degradation and to achieve efficient intracellular delivery. However, LNP-mRNA vaccines pose a real risk of causing transient myocarditis and a requirement for ultra-cold storage to maintain stability. Gene gun (GG) delivery holds considerable potential to improve the safety and stability of RNA vaccines. GG delivery results in the direct microinjection of DNA and/or RNA vaccine-coated gold microparticles into cells of the epidermis. Delivery into the highly immunocompetent skin layer, including direct transfection of local antigen presenting cells, results in robust immunogenicity with very low doses of DNA or RNA. In addition, the dry, nuclease-free formulation holds potential to offer stable ambient formulation that could obviate the need for ultra-cold storage. GG delivery to the epidermis is also needle-free and pain-free and eliminates the need for LNP formulation that may contribute to the rare adverse events, including myocarditis associated with mRNA/LNP vaccines. Furthermore, GG delivery into the skin, in contrast to the muscle, elicits robust mucosal antibody and T cell responses that could enhance protection from mucosally transmitted diseases. In the 1990s, PowderJect Vaccines developed a prototype clinical GG that showed, for first time, the ability of a DNA vaccine to induce protective levels of immunity in humans. Orlance has since implemented engineering improvements to this device resulting in enhanced dose delivery, immunogenicity, and field-/clinic-friendly features such as battery power, automatic dose advancement, and lock-out functions. Historically, the GG delivered only DNA vaccines but due to its physical mechanism of intracellular delivery, we have found that GG can also efficiently deliver RNA vaccines in a dry formulation that could offer significant advantages in warmer temperature stability, efficacy at lower doses, and improved safety/reactogenicity. Indeed, our preliminary studies show that the GG can effectively deliver RNA vaccines and GG delivery of low doses of RNA induces comparable immunogenicity as RNA vaccines delivered in LNPs. In Phase I SBIR, we will optimize RNA formulations for GG delivery. With further optimization, we hypothesize that GG delivery of RNA vaccines will offer substantial advantages over current mRNA/LNP vaccines with respect to stability and safety while achieving comparable systemic immunogenicity and superior mucosal immunogenicity. In Aim 1, we will identify an optimum formulation for GG delivery of RNA vaccines including maximum loading, functional integrity, stability, and immunogenicity. In Aim 2, we will determine if GG delivery of influenza and SARS-CoV-2 RNA vaccines are stable at room temperature or 4°C and can induce comparable or superior systemic or mucosal immune responses with lower reactogenicity when compared LNP/RNA vaccines. If successful, these studies will provide an alternative RNA vaccine delivery strategy with advantages in mucosal immunity, safety, stability, dose sparing, and pain/needle-free delivery.