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Final Report Summary - SAMUFLU (Self-amplifying RNA technology applied to the development of a universal influenza vaccine)

The aim of the SAMUFLU project was to develop a universal influenza vaccine based on a novel SAM® technology that consists of synthetic self-amplifying mRNA delivered by lipid nanoparticles. SAMUFLU objectives were to select hemagglutinin (HA) antigens from most relevant past seasonal and pandemic strains of influenza and prepare SAM(HA) vectors encoding single or combination of multiple HAs. The immunogenicity of these SAM(HA) replicons was tested in vivo in mice.
An extensive literature search for most relevant seasonal and pandemic influenza strains was carried out. Altogether, 20 strains were selected on the basis of their glycosylation pattern, and evolutionary and antigenic cartography. With the help of computational biology and published literature, SAM vectors were designed to express single or multiple HA. Recombinant plasmids containing full length HA genes were made and checked by standard molecular techniques. Recombinant DNA plasmids were transcribed into mRNA and capped using Vaccinia capping system. Integrity and expression of RNA were checked by standard in-vitro potency and Western blotting assays, respectively. Further, RNA vaccines were formulated with synthetic lipid nanoparticles (LNP) or cationic nanoemulsions (CNE) followed by characterization for particle size, RNA concentration and encapsulation efficiency. Immunogenicity of SAM(HA) formulations were characterized in BALB/c mice by measuring functional antibody titers using the hemagglutination-inhibition (HI) assay. In-depth analysis of HA-specific memory and effector CD4+ and CD8+ T-cells induced by SAM(HA) vaccine were also characterized by state-of-the-art flow cytometry techniques.
Single and multivalent SAM(HA) replicons were made and correctly expressed the full-length HA(s) they encoded in vitro. SAM(HA) formulated with LNP were then characterized for broadly-reactive immune responses. SAM(HA) formulations induced multifunctional cross-reactive CD4 and CD8 T cells, with effector cytokines profile and cytotoxic activity. Functional antibody responses are currently being assessed.
In summary, multivalent SAM vaccine containing full length influenza HA antigens induced broadly reactive immune responses in mice, supporting the SAM® platform as a promising strategy for the development of broad-spectrum universal influenza vaccines. Results from these studies can be extended to the development of SAM®-based multivalent vaccines and therapeutics against other pathogens and diseases.

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