Comparison of Physicochemical Properties of LipoParticles as mRNA Carrier Prepared by Automated Microfluidic System and Bulk Method

An LNP-mRNA vaccine protects fish against rhabdovirus infection

mRNA vaccines are poised to revolutionize disease prevention, following the approval of their administration to humans against SARS-CoV-2. Although they have been extensively studied for human applications, their potential in the veterinary field has not been explored yet. No mRNA vaccines have yet been reported for fish, despite the urgent need for new vaccines against emerging pathogens in aquaculture. As fish are ectotherms, temperature has an impact on their immune response and on many other biological parameters, including the composition of membrane lipids. It is therefore crucial to identify whether mRNA delivery systems are suitable for in vivo expression in fish for vaccine purposes. In the present study, we developed a proof of concept for mRNA vaccination in rainbow trout, a salmonid, demonstrating the efficacy of current vaccine delivery systems in fish. We used lipid nanoparticles (LNPs), which represent the most advanced delivery technology for mRNA. LNPs use a combination of lipid components that form an encapsulating structure offering protection and promote endosome escape of the mRNA to allow its expression. In vitro assays showed that LNPs are a powerful vehicle for mRNA delivery in fish cells without substantial toxicity. In vivo imaging in adult zebrafish (Danio rerio) demonstrated that intramuscular injection of LNP-formulated egfp mRNA resulted in local expression of eGFP for up to 7 days. An LNP-based mRNA vaccine candidate encoding the viral haemorrhagic septicaemia virus (VHSV) glycoprotein induced neutralizing antibodies in rainbow trout (Oncorhynchus mykiss) and offers almost complete protection against a lethal viral challenge. Our data constitute a first proof of concept of mRNA vaccination in fish, paving the way for new developments in veterinary vaccines for aquaculture.

Technological breakthroughs and advancements in the application of mRNA vaccines: a comprehensive exploration and future prospects

mRNA vaccines utilize single-stranded linear DNA as a template for in vitro transcription. The mRNA is introduced into the cytoplasm via the corresponding delivery system to express the target protein, which then performs its relevant biological function. mRNA vaccines are beneficial in various fields, including cancer vaccines, infectious disease vaccines, protein replacement therapy, and treatment of rare diseases. They offer advantages such as a simple manufacturing process, a quick development cycle, and ease of industrialization. Additionally, mRNA vaccines afford flexibility in adjusting antigen designs and combining sequences of multiple variants, thereby addressing the issue of frequent mutations in pathogenic microorganisms. This paper aims to provide an extensive review of the global development and current research status of mRNA vaccines, with a focus on immunogenicity, classification, design, delivery vector development, stability, and biomedical application. Moreover, the study highlights current challenges and offers insights into future directions for development.

Delineating effect of headgroup and preparation method on transfection versus toxicity of DNA-loaded lipid nanocarriers

Aim: To perform a parallel comparison of key parameters affecting the safety and efficiency of lipid-based nanovectors (i.e., complexing headgroups, composition and preparation method). Materials & methods: Various cationic and ionizable headgroups were screened for formulating lipoplexes with GFP-plasmid DNA. Ethanol injection and microfluidics were used to prepare nanoparticles with GFP-plasmid DNA complexed on the surface or within the interior of lipid bilayers. Results: Lipoplexes composed of sphingomyelin 102 exhibited the highest transfection efficiency given their higher cellular uptake in BRAF inhibitor-resistant melanoma cells. Lipid nanoparticles demonstrated acceptable transfection efficiency and high spheroid penetration while protecting plasmid DNA under simulated physiological conditions. Conclusion: Selecting the right complexing lipid and preparation method is critical for developing lipid nanocarriers to treat intractable diseases.

DLin-MC3-Containing mRNA Lipid Nanoparticles Induce an Antibody Th2-Biased Immune Response Polarization in a Delivery Route-Dependent Manner in Mice

mRNA-based vaccines have made a leap forward since the SARS-CoV-2 pandemic and are currently used to develop anti-infectious therapies. If the selection of a delivery system and an optimized mRNA sequence are two key factors to reach in vivo efficacy, the optimal administration route for those vaccines remains unclear. We investigated the influence of lipid components and immunization route regarding the intensity and quality of humoral immune responses in mice. The immunogenicity of HIV-p55Gag encoded mRNA encapsulated into D-Lin-MC3-DMA or GenVoy-ionizable lipid-based LNPs was compared after intramuscular or subcutaneous routes. Three sequential mRNA vaccines were administrated followed by a heterologous boost composed of p24-HIV protein antigen. Despite equivalent IgG kinetic profiles of general humoral responses, IgG1/IgG2a ratio analysis showed a Th2/Th1 balance toward a Th1-biased cellular immune response when both LNPs were administrated via the intramuscular route. Surprisingly, a Th2-biased antibody immunity was observed when DLin-containing vaccine was injected subcutaneously. A protein-based vaccine boost appeared to reverse this balance to a cellular-biased response correlated to an increase in antibody avidity. Our finding suggests that the intrinsic adjuvant effect of ionizable lipids appears to be dependent on the delivery route used, which could be relevant to reach potent and long-lasting immunity after mRNA-based immunization.