Spatial and Temporal Adjuvant Delivery for Skin mRNA Vaccination

Abstract The success of COVID-19 mRNA vaccines has showcased the effectiveness of this technology in rapid design, manufacturing, and adaptation to emerging viral threats. However, several imitations remain, including their instability requiring cold-chain storage that limits their global distribution, the necessity for two doses for optimal efficacy, limited immunity to closely matched viral strains, and quick-waning immunity following the initial two doses. These limitations can be potentially addressed by potent adjuvants. However, traditional adjuvants, co-delivered with vaccines to enhance antigen-presenting cell (APC) recruitment and functionality, are unsuitable for mRNA vaccines, because the co-delivered adjuvant provokes innate immune responses that interfere with mRNA translation, reducing its immunogenicity. Our recent investigation demonstrated that mRNA vaccines, particularly when delivered intradermally, could be substantially augmented by adjuvant delivery at different times and locations relative to mRNA vaccination, effectively circumventing the interference with mRNA transcription and translation. The current proposal aims to determine whether intranasal (IN) or intradermal (ID) delivery of a newly developed adjuvant can expand the breadth and longevity of trivalent influenza (flu) mRNA vaccine administered via a microneedle array patch (MNP). Specifically, we will construct a trivalent self-amplifying mRNA (saRNA) flu vaccine, encapsulated within liposomes free of cationic or ionizable lipids using our proprietary technology, and then loaded into our caved MNP after lyophilization. The antigen expression, immunogenicity, and efficacy of this saRNA flu vaccine will be optimized and evaluated in mice. Aim 2 will define the optimal time window of IN or ID adjuvant delivery following MNP-saRNA- flu immunization. Antigens-specific T-cell responses and broad neutralization antibodies across homosubtypic and heterosubtypic flu strains will be assessed and compared with or without the adjuvant and between IN and ID adjuvant delivery. The longevity of the specific immune responses will be also monitored over several months. Aim 3 will validate the efficacy of MNP immunization, alongside delayed adjuvant delivery, against various flu viruses in young and aging mice. If successful, the innovative strategy can be extended to other respiratory viral vaccines, such as those for COVID-19, respiratory syncytial viruses, etc., broadening the breadth and efficacy of various RNA-based vaccines delivered parenterally.