Mild Innate Immune Activation Overrides Efficient Nanoparticle-Mediated RNA Delivery

Recent strategies for enhanced delivery of mRNA to the lungs

mRNA-based therapies have emerged as a transformative tool in modern medicine, gaining significant attention following their successful use in COVID-19 vaccines. Delivery to the lungs offers several compelling advantages for mRNA delivery. The lungs are one of the most vascularized organs in the body, which provides an extensive surface area that can facilitate efficient drug transport. Local delivery to the lungs bypasses gastrointestinal degradation, potentially enhancing therapeutic efficacy. In addition, the extensive capillary network of the lungs provides an ideal target for systemic delivery. However, developing effective mRNA therapies for the lungs presents significant challenges. The complex anatomy of the lungs and the body's immune response to foreign particles create barriers to delivery. This review discusses key approaches for overcoming these challenges and improving mRNA delivery to the lungs. It examines both local and systemic delivery strategies aimed at improving lung delivery while mitigating off-target effects. Although substantial progress has been made in lung-targeted mRNA therapies, challenges remain in optimizing cellular uptake and achieving therapeutic efficacy within pulmonary tissues. The continued refinement of delivery strategies that enhance lung-specific targeting while minimizing degradation is critical for the clinical success of mRNA-based pulmonary therapies.

Generation of an inflammatory niche in a hydrogel depot through recruitment of key immune cells improves efficacy of mRNA vaccines

Messenger RNA (mRNA) delivered in lipid nanoparticles (LNPs) rose to the forefront of vaccine candidates during the COVID-19 pandemic due to scalability, adaptability, and potency. Yet, there remain critical areas for improvements of these vaccines in durability and breadth of humoral responses. In this work, we explore a modular strategy to target mRNA/LNPs to antigen-presenting cells with an injectable polymer-nanoparticle (PNP) hydrogel technology, which recruits key immune cells and forms an immunological niche in vivo. We characterize this niche on a single-cell level and find it is highly tunable through incorporation of adjuvants like MPLAs and 3M-052. Delivering commercially available severe acute respiratory syndrome coronavirus 2 mRNA vaccines in PNP hydrogels improves the durability and quality of germinal center reactions, and the magnitude, breadth, and durability of humoral responses. The tunable immune niche formed within PNP hydrogels effectively skews immune responses based on encapsulated adjuvants, creating opportunities to precisely modulate mRNA/LNP vaccines for various indications from infectious diseases to cancers.

The time course of in vivo cellular responses to LNPs

Cells actively respond to drug delivery systems. However, the time course of cellular responses to lipid nanoparticles (LNPs) remains unclear. Here we characterized the transcriptomic response to LNPs carrying mRNA at different timepoints in vivo. Exposure to LNPs altered the expression of signaling pathways including endocytosis and lysosomal pathways as soon as one hour after administration. These pathways returned to their baseline state by 24 hours. Our data are consistent with the hypothesis that cells actively yet transiently respond to LNPs.

Generation of an inflammatory niche in an injectable hydrogel depot through recruitment of key immune cells improves efficacy of mRNA vaccines

Messenger RNA (mRNA) delivered in lipid nanoparticles (LNPs) rose to the forefront of vaccine candidates during the COVID-19 pandemic due in part to scalability, adaptability, and potency. Yet there remain critical areas for improvements of these vaccines in durability and breadth of humoral responses. In this work, we explore a modular strategy to target mRNA/LNPs to antigen presenting cells with an injectable polymer-nanoparticle (PNP) hydrogel depot technology which recruits key immune cells and forms an immunological niche in vivo. We characterize this niche on a single cell level and find it is highly tunable through incorporation of adjuvants like MPLAs and 3M-052. Delivering commercially available SARS-CoV-2 mRNA vaccines in PNP hydrogels improves the durability and quality of germinal center reactions, and the magnitude, breadth, and durability of humoral responses. The tunable immune niche formed within PNP hydrogels effectively skews immune responses based on encapsulated adjuvants, creating opportunities to precisely modulate mRNA/LNP vaccines for various indications from infectious diseases to cancers.

Enhancing RNA-lipid nanoparticle delivery: Organ- and cell-specificity and barcoding strategies

Recent advancements in RNA therapeutics highlight the critical need for precision gene delivery systems that target specific organs and cells. Lipid nanoparticles (LNPs) have emerged as key vectors in delivering mRNA and siRNA, offering protection against enzymatic degradation, enabling targeted delivery and cellular uptake, and facilitating RNA cargo release into the cytosol. This review discusses the development and optimization of organ- and cell-specific LNPs, focusing on their design, mechanisms of action, and therapeutic applications. We explore innovations such as DNA/RNA barcoding, which facilitates high-throughput screening and precise adjustments in formulations. We address major challenges, including improving endosomal escape, minimizing off-target effects, and enhancing delivery efficiencies. Notable clinical trials and recent FDA approvals illustrate the practical applications and future potential of LNP-based RNA therapies. Our findings suggest that while considerable progress has been made, continued research is essential to resolve existing limitations and bridge the gap between preclinical and clinical evaluation of the safety and efficacy of RNA therapeutics. This review highlights the dynamic progress in LNP research. It outlines a roadmap for future advancements in RNA-based precision medicine.

COVID-19 vaccine adverse events: Evaluating the pathophysiology with an emphasis on sulfur metabolism and endotheliopathy

In this narrative review, we assess the pathophysiology of severe adverse events that presented after vaccination with DNA and mRNA vaccines against COVID-19. The focus is on the perspective of an undersulfated and degraded glycocalyx, considering its impact on immunomodulation, inflammatory responses, coagulation and oxidative stress. The paper explores various factors that lead to glutathione and inorganic sulfate depletion and their subsequent effect on glycocalyx sulfation and other metabolites, including hormones. Components of COVID-19 vaccines, such as DNA and mRNA material, spike protein antigen and lipid nanoparticles, are involved in possible cytotoxic effects. The common thread connecting these adverse events is endotheliopathy or glycocalyx degradation, caused by depleted glutathione and inorganic sulfate levels, shear stress from circulating nanoparticles, aggregation and formation of protein coronas; leading to imbalanced immune responses and chronic release of pro-inflammatory cytokines, ultimately resulting in oxidative stress and systemic inflammatory response syndrome. By understanding the underlying pathophysiology of severe adverse events, better treatment options can be explored.

mRNA-delivery of IDO1 suppresses T cell-mediated autoimmunity

Indoleamine-2,3-dioxygenase (IDO)1 degrades tryptophan, obtained through dietary intake, into immunoregulatory metabolites of the kynurenine pathway. Deficiency or blockade of IDO1 results in the enhancement of autoimmune severity in rodent models and increased susceptibility to developing autoimmunity in humans. Despite this, therapeutic modalities that leverage IDO1 for the treatment of autoimmunity remain limited. Here, we use messenger (m)RNA formulated in lipid nanoparticles (LNPs) to deliver a human IDO1 variant containing the myristoylation site of Src to anchor the protein to the inner face of the plasma membrane. This membrane-anchored IDO1 has increased protein production, leading to increased metabolite changes, and ultimately ameliorates disease in three models of T cell-mediated autoimmunity: experimental autoimmune encephalomyelitis (EAE), rat collagen-induced arthritis (CIA), and acute graft-versus-host disease (aGVHD). The efficacy of IDO1 is correlated with hepatic expression and systemic tryptophan depletion. Thus, the delivery of membrane-anchored IDO1 by mRNA suppresses the immune response in several well-characterized models of autoimmunity.

Lipid Nanoparticles Elicit Reactogenicity and Sickness Behavior in Mice Via Toll-Like Receptor 4 and Myeloid Differentiation Protein 88 Axis

mRNA therapeutics encapsulated in lipid nanoparticles (LNPs) offer promising avenues for treating various diseases. While mRNA vaccines anticipate immunogenicity, the associated reactogenicity of mRNA-loaded LNPs poses significant challenges, especially in protein replacement therapies requiring multiple administrations, leading to adverse effects and suboptimal therapeutic outcomes. Historically, research has primarily focused on the reactogenicity of mRNA cargo, leaving the role of LNPs understudied in this context. Adjuvanticity and pro-inflammatory characteristics of LNPs, originating at least in part from ionizable lipids, may induce inflammation, activate toll-like receptors (TLRs), and impact mRNA translation. Knowledge gaps remain in understanding LNP-induced TLR activation and its impact on induction of animal sickness behavior. We hypothesized that ionizable lipids in LNPs, structurally resembling lipid A from lipopolysaccharide, could activate TLR4 signaling via MyD88 and TRIF adaptors, thereby propagating LNP-associated reactogenicity. Our comprehensive investigation utilizing gene ablation studies and pharmacological receptor manipulation proves that TLR4 activation by LNPs triggers distinct physiologically meaningful responses in mice. We show that TLR4 and MyD88 are essential for reactogenic signal initiation, pro-inflammatory gene expression, and physiological outcomes like food intake and body weight─robust metrics of sickness behavior in mice. The application of the TLR4 inhibitor TAK-242 effectively reduces the reactogenicity associated with LNPs by mitigating TLR4-driven inflammatory responses. Our findings elucidate the critical role of the TLR4-MyD88 axis in LNP-induced reactogenicity, providing a mechanistic framework for developing safer mRNA therapeutics and offering a strategy to mitigate adverse effects through targeted inhibition of this pathway.

Lipid nanoparticle (LNP) mediated mRNA delivery in cardiovascular diseases: Advances in genome editing and CAR T cell therapy

Cardiovascular diseases (CVDs) are the leading cause of global mortality among non-communicable diseases. Current cardiac regeneration treatments have limitations and may lead to adverse reactions. Hence, innovative technologies are needed to address these shortcomings. Messenger RNA (mRNA) emerges as a promising therapeutic agent due to its versatility in encoding therapeutic proteins and targeting "undruggable" conditions. It offers low toxicity, high transfection efficiency, and controlled protein production without genome insertion or mutagenesis risk. However, mRNA faces challenges such as immunogenicity, instability, and difficulty in cellular entry and endosomal escape, hindering its clinical application. To overcome these hurdles, lipid nanoparticles (LNPs), notably used in COVID-19 vaccines, have a great potential to deliver mRNA therapeutics for CVDs. This review highlights recent progress in mRNA-LNP therapies for CVDs, including Myocardial Infarction (MI), Heart Failure (HF), and hypercholesterolemia. In addition, LNP-mediated mRNA delivery for CAR T-cell therapy and CRISPR/Cas genome editing in CVDs and the related clinical trials are explored. To enhance the efficiency, safety, and clinical translation of mRNA-LNPs, advanced technologies like artificial intelligence (AGILE platform) in RNA structure design, and optimization of LNP formulation could be integrated. We conclude that the strategies to facilitate the extra-hepatic delivery and targeted organ tropism of mRNA-LNPs (SORT, ASSET, SMRT, and barcoded LNPs) hold great prospects to accelerate the development and translation of mRNA-LNPs in CVD treatment.

Robust anti-tumor immunity through the integration of targeted lipid nanoparticle-based mRNA nanovaccines with PD-1/PD-L1 blockade

Tumor mRNA vaccines present a personalized approach in cancer immunotherapy, encoding distinct tumor antigens to evoke robust immune responses and offering the potential against emerging tumor variants. Despite this, the clinical advancement of tumor mRNA vaccines has been hampered by their limited delivery capacity and inefficient activation of antigen-presenting cells (APCs). Herein, we employed microfluidics technology to engineer mannose-modified lipid-based nanovaccines for specifically targeting APCs. The encapsulation process efficiently entrapped the cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) agonist along with mRNA encoding antigens. The targeted nanovaccines (TNVs) exhibited a narrow particle size distribution, ensuring consistent and efficient delivery. These TNVs significantly enhanced gene expression of mRNA, facilitating antigen presentation and immune activation. When compared to non-targeted nanovaccines, TNVs outperformed in terms of antigen presentation and immune activation. Furthermore, the combination of anti-PD-L1 antibodies with TNVs elicited a synergistic anti-tumor effect. This was attributed to the anti-PD-L1 antibodies' ability to overcome the immune suppression of tumor cells. Our findings suggest that the combination treatment elicited the most robust anti-tumor immune activation and immune memory effect. These results indicate that integrating tumor mRNA vaccines with immune checkpoint inhibitors or other immunostimulatory agents may be crucial for enhancing the immune response.

Helper Lipid-Enhanced mRNA Delivery for Treating Metabolic Dysfunction-Associated Fatty Liver Disease

Lipid nanoparticles (LNPs) represent the forefront of mRNA delivery platforms, yet achieving precise delivery to specific cells remains a challenge. The current targeting strategies complicate the formulation and impede the regulatory approval process. Here, through a straightforward regulation of helper lipids within LNPs, we introduce an engineered LNP designed for targeted delivery of mRNA into hepatocytes for metabolic dysfunction-associated fatty liver disease (MAFLD) treatment. The optimized LNP, supplied with POPC as the helper lipid, exhibits a 2.49-fold increase in mRNA transfection efficiency in hepatocytes compared to that of FDA-approved LNPs. CTP:phosphocholine cytidylyltransferase α mRNA is selected for delivery to hepatocytes through the optimized LNP system for self-calibration of phosphatidylcholine levels to prevent lipid droplet expansion in MAFLD. This strategy effectively regulates lipid homeostasis, while demonstrating proven biosafety. Our results present a mRNA therapy for MAFLD and open a new avenue for discovering potent lipids enabling mRNA delivery to specific cells.

Engineering aspects of lipid-based delivery systems: In vivo gene delivery, safety criteria, and translation strategies

Defects in the genome cause genetic diseases and can be treated with gene therapy. Due to the limitations encountered in gene delivery, lipid-based supramolecular colloidal materials have emerged as promising gene carrier systems. In their non-functionalized form, lipid nanoparticles often demonstrate lower transgene expression efficiency, leading to suboptimal therapeutic outcomes, specifically through reduced percentages of cells expressing the transgene. Due to chemically active substituents, the engineering of delivery systems for genetic drugs with specific chemical ligands steps forward as an innovative strategy to tackle the drawbacks and enhance their therapeutic efficacy. Despite intense investigations into functionalization strategies, the clinical outcome of such therapies still needs to be improved. Here, we highlight and comprehensively review engineering aspects for functionalizing lipid-based delivery systems and their therapeutic efficacy for developing novel genetic cargoes to provide a full snapshot of the translation from the bench to the clinics. We outline existing challenges in the delivery and internalization processes and narrate recent advances in the functionalization of lipid-based delivery systems for nucleic acids to enhance their therapeutic efficacy and safety. Moreover, we address clinical trials using these vectors to expand their clinical use and principal safety concerns.

Physiological Barriers and Strategies of Lipid-Based Nanoparticles for Nucleic Acid Drug Delivery

Lipid-based nanoparticles (LBNPs) are currently the most promising vehicles for nucleic acid drug (NAD) delivery. Although their clinical applications have achieved success, the NAD delivery efficiency and safety are still unsatisfactory, which are, to a large extent, due to the existence of multi-level physiological barriers in vivo. It is important to elucidate the interactions between these barriers and LBNPs, which will guide more rational design of efficient NAD vehicles with low adverse effects and facilitate broader applications of nucleic acid therapeutics. This review describes the obstacles and challenges of biological barriers to NAD delivery at systemic, organ, sub-organ, cellular, and subcellular levels. The strategies to overcome these barriers are comprehensively reviewed, mainly including physically/chemically engineering LBNPs and directly modifying physiological barriers by auxiliary treatments. Then the potentials and challenges for successful translation of these preclinical studies into the clinic are discussed. In the end, a forward look at the strategies on manipulating protein corona (PC) is addressed, which may pull off the trick of overcoming those physiological barriers and significantly improve the efficacy and safety of LBNP-based NADs delivery.

Strategies to reduce the risks of mRNA drug and vaccine toxicity

mRNA formulated with lipid nanoparticles is a transformative technology that has enabled the rapid development and administration of billions of coronavirus disease 2019 (COVID-19) vaccine doses worldwide. However, avoiding unacceptable toxicity with mRNA drugs and vaccines presents challenges. Lipid nanoparticle structural components, production methods, route of administration and proteins produced from complexed mRNAs all present toxicity concerns. Here, we discuss these concerns, specifically how cell tropism and tissue distribution of mRNA and lipid nanoparticles can lead to toxicity, and their possible reactogenicity. We focus on adverse events from mRNA applications for protein replacement and gene editing therapies as well as vaccines, tracing common biochemical and cellular pathways. The potential and limitations of existing models and tools used to screen for on-target efficacy and de-risk off-target toxicity, including in vivo and next-generation in vitro models, are also discussed.

From structural design to delivery: mRNA therapeutics for cancer immunotherapy

mRNA therapeutics have emerged as powerful tools for cancer immunotherapy in accordance with their superiority in expressing all sequence-known proteins in vivo. In particular, with a small dosage of delivered mRNA, antigen-presenting cells (APCs) can synthesize mutant neo-antigens and multi-antigens and present epitopes to T lymphocytes to elicit antitumor effects. In addition, expressing receptors like chimeric antigen receptor (CAR), T-cell receptor (TCR), CD134, and immune-modulating factors including cytokines, interferons, and antibodies in specific cells can enhance immunological response against tumors. With the maturation of in vitro transcription (IVT) technology, large-scale and pure mRNA encoding specific proteins can be synthesized quickly. However, the clinical translation of mRNA-based anticancer strategies is restricted by delivering mRNA into target organs or cells and the inadequate endosomal escape efficiency of mRNA. Recently, there have been some advances in mRNA-based cancer immunotherapy, which can be roughly classified as modifications of the mRNA structure and the development of delivery systems, especially the lipid nanoparticle platforms. In this review, the latest strategies for overcoming the limitations of mRNA-based cancer immunotherapies and the recent advances in delivering mRNA into specific organs and cells are summarized. Challenges and opportunities for clinical applications of mRNA-based cancer immunotherapy are also discussed.

Lymph node macrophages drive innate immune responses to enhance the anti-tumor efficacy of mRNA vaccines

mRNA vaccines are promising for cancer treatment. Efficient delivery of mRNAs encoding tumor antigens to antigen-presenting cells (APCs) is critical to elicit anti-tumor immunity. Herein, we identified a novel lipid nanoparticle (LNP) formulation, L17-F05, for mRNA vaccines by screening 34 ionizable lipids and 28 LNP formulations using human primary APCs. Subcutaneous delivery of L17-F05 mRNA vaccine encoding Gp100 and Trp2 inhibited tumor growth and prolonged the survival of mice bearing B16F10 melanoma. L17-F05 efficiently delivered mRNAs to conventional dendritic cells (cDCs) and macrophages in draining lymph nodes (dLNs). cDCs functioned as the main APCs by presenting antigens along with enhanced expression of co-stimulatory molecules. Macrophages triggered innate immune responses centered on type-I interferon (IFN-I) in dLNs. Lymph node (LN) macrophage depletion attenuated APC maturation and anti-tumor activity of L17-F05 mRNA vaccines. Loss-of-function studies revealed that L17-F05 works as a self-adjuvant by activating the stimulator of interferon genes (STING) pathway in macrophages. Collectively, the self-adjuvanticity of L17-F05 triggered innate immune responses in LN macrophages via the STING-IFN-I pathway, contributing to APC maturation and potent anti-tumor activity of L17-F05 mRNA vaccines. Our findings provide strategies for further optimization of mRNA vaccines based on the innate immune response driven by LN macrophages.

Comparative analysis of lipid Nanoparticle-Mediated delivery of CRISPR-Cas9 RNP versus mRNA/sgRNA for gene editing in vitro and in vivo

The discovery that the bacterial defense mechanism, CRISPR-Cas9, can be reprogrammed as a gene editing tool has revolutionized the field of gene editing. CRISPR-Cas9 can introduce a double-strand break at a specific targeted site within the genome. Subsequent intracellular repair mechanisms repair the double strand break that can either lead to gene knock-out (via the non-homologous end-joining pathway) or specific gene correction in the presence of a DNA template via homology-directed repair. With the latter, pathological mutations can be cut out and repaired. Advances are being made to utilize CRISPR-Cas9 in patients by incorporating its components into non-viral delivery vehicles that will protect them from premature degradation and deliver them to the targeted tissues. Herein, CRISPR-Cas9 can be delivered in the form of three different cargos: plasmid DNA, RNA or a ribonucleoprotein complex (RNP). We and others have recently shown that Cas9 RNP can be efficiently formulated in lipid-nanoparticles (LNP) leading to functional delivery in vitro. In this study, we compared LNP encapsulating the mRNA Cas9, sgRNA and HDR template against LNP containing Cas9-RNP and HDR template. Former showed smaller particle sizes, better protection against degrading enzymes and higher gene editing efficiencies on both reporter HEK293T cells and HEPA 1-6 cells in in vitro assays. Both formulations were additionally tested in female Ai9 mice on biodistribution and gene editing efficiency after systemic administration. LNP delivering mRNA Cas9 were retained mainly in the liver, with LNP delivering Cas9-RNPs additionally found in the spleen and lungs. Finally, gene editing in mice could only be concluded for LNP delivering mRNA Cas9 and sgRNA. These LNPs resulted in 60 % gene knock-out in hepatocytes. Delivery of mRNA Cas9 as cargo format was thereby concluded to surpass Cas9-RNP for application of CRISPR-Cas9 for gene editing in vitro and in vivo.

Nano-Bio Interactions: Exploring the Biological Behavior and the Fate of Lipid-Based Gene Delivery Systems

Gene therapy for many diseases is rapidly becoming a reality, as demonstrated by the recent approval of various nucleic acid-based therapeutics. Non-viral systems such as lipid-based carriers, lipid nanoparticles (LNPs), for delivering different payloads including small interfering RNA, plasmid DNA, and messenger RNA have been particularly extensively explored and developed for clinical uses. One of the most important issues in LNP development is delivery to extrahepatic tissues. To achieve this, various lipids and lipid-like materials are being examined and screened. Several LNP formulations that target extrahepatic tissues, such as the spleen and the lungs have been developed by adjusting the lipid compositions of LNPs. However, mechanistic details of how the characteristics of LNPs affect delivery efficiency remains unclear. The purpose of this review is to provide an overview of LNP-based nucleic acid delivery focusing on LNP components and their structures, as well as discussing biological factors, such as biomolecular corona and cellular responses related to the delivery efficiency.

Lipid Nanoparticle (LNP) Delivery Carrier-Assisted Targeted Controlled Release mRNA Vaccines in Tumor Immunity

In recent years, lipid nanoparticles (LNPs) have attracted extensive attention in tumor immunotherapy. Targeting immune cells in cancer therapy has become a strategy of great research interest. mRNA vaccines are a potential choice for tumor immunotherapy, due to their ability to directly encode antigen proteins and stimulate a strong immune response. However, the mode of delivery and lack of stability of mRNA are key issues limiting its application. LNPs are an excellent mRNA delivery carrier, and their structural stability and biocompatibility make them an effective means for delivering mRNA to specific targets. This study summarizes the research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity. The role of LNPs in improving mRNA stability, immunogenicity, and targeting is discussed. This review aims to systematically summarize the latest research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity to provide new ideas and strategies for tumor immunotherapy, as well as to provide more effective treatment plans for patients.

Nanoparticle-Mediated Delivery of Anti-PU.1 siRNA via Localized Intracisternal Administration Reduces Neuroinflammation

Neuroinflammation is a hallmark of neurodegenerative disorders including Alzheimer's disease (AD). Microglia, the brain's immune cells, express many of the AD-risk loci identified in genome wide association studies and present a promising target for anti-inflammatory RNA therapeutics but are difficult to transfect with current methods. Here, several lipid nanoparticle (LNP) formulations are examined, and a lead candidate that supports efficient RNA delivery in cultures of human stem cell-derived microglia-like cells (iMGLs) and animal models of neuroinflammation is identified. The lead microglia LNP (MG-LNP) formulation shows minimal toxicity and improves delivery efficiency to inflammatory iMGLs, suggesting a preference for delivery into activated microglia. Intraperitoneal injection of the MG-LNP formulation generates widespread expression of the delivered reporter construct in all organs, whereas local intracisternal injection directly into the cerebrospinal fluid leads to preferential expression in the brain. It is shown that LNP-mediated delivery of siRNA targeting the PU.1 transcription factor, a known AD-risk locus, successfully reduces PU.1 levels in iMGLs and reduces neuroinflammation in mice injected with LPS and in CK-p25 mice that mimic the chronic neuroinflammation seen in AD patients. The LNP formulation represents an effective RNA delivery vehicle when applied intrathecally and can be broadly utilized to test potential neuroinflammation-directed gene therapies.

In Vivo Prime Editing by Lipid Nanoparticle Co-delivery of Chemically Modified pegRNA and Prime Editor mRNA

Prime editing has gained significant attention as a next-generation gene editing technology, owing to its unique advantages. However, realizing its potential in vivo requires effective delivery strategies. While adeno-associated virus (AAV) has been employed for in vivo delivery of prime editors in research settings, it presents inherent limitations related to vector size, ongoing expression, and inability to re-dose patients. Conversely, lipid nanoparticles (LNPs) do not face these limitations and are emerging as a leading non-viral approach for the delivery of gene editors. In this study, we demonstrate successful co-delivery of chemically modified pegRNA and prime editor mRNA using LNPs for in vivo prime editing. We investigate the impact of pegRNA chemical modifications on editing efficiency and explore different re-dosing regimens. In a daily-repeat dose regimen, we saw striking liver toxicity and no increase in editing; by contrast, weekly-repeat dosing was well tolerated and enabled 1.8-fold increase in editing efficacy. Furthermore, in the NSG immunodeficient mouse model, the efficacy of LNP-delivered prime editing was enhanced by 2.8-fold. In addition, the nature of the ionizable lipids and phospholipids strongly influenced prime editing efficiency in vivo. Overall, these findings will greatly contribute to the future development of LNPs as a robust platform for delivering prime editors in vivo, fostering progress in prime editing research and therapeutic applications.

Cellular Trafficking of Nanotechnology-Mediated mRNA Delivery

Messenger RNA (mRNA)-based therapy has emerged as a powerful, safe, and rapidly scalable therapeutic approach that involves technologies for both mRNA itself and the delivery vehicle. Although there are some unique challenges for different applications of mRNA therapy, a common challenge for all mRNA therapeutics is the transport of mRNA into the target cell cytoplasm for sufficient protein expression. This review is focused on the behaviors at the cellular level of nanotechnology-mediated mRNA delivery systems, which have not been comprehensively reviewed yet. First, the four main therapeutic applications of mRNA are introduced, including immunotherapy, protein replacement therapy, genome editing, and cellular reprogramming. Second, common types of mRNA cargos and mRNA delivery systems are summarized. Third, strategies to enhance mRNA delivery efficiency during the cellular trafficking process are highlighted, including accumulation to the cell, internalization into the cell, endosomal escape, release of mRNA from the nanocarrier, and translation of mRNA into protein. Finally, the challenges and opportunities for the development of nanotechnology-mediated mRNA delivery systems are presented. This review can provide new insights into the future fabrication of mRNA nanocarriers with desirable cellular trafficking performance.

Dendritic Cell-Mimicking Nanoparticles Promote mRNA Delivery to Lymphoid Organs

Spleen and lymphoid organs are important targets for messenger RNA (mRNA) delivery in various applications. Current nanoparticle delivery methods rely on drainage to lymph nodes from intramuscular or subcutaneous injections. In difficult-to-transfect antigen-presenting cells (APCs), such as dendritic cells (DCs), effective mRNA transfection remains a significant challenge. In this study, a lymphatic targeting carrier using DC membranes is developed, that efficiently migrated to lymphoid organs, such as the spleen and lymph nodes. The nanoparticles contained an ionizable lipid (YK009), which ensured a high encapsulation efficacy of mRNA and assisted mRNA with endosomal escape after cellular uptake. Dendritic cell-mimicking nanoparticles (DCMNPs) showed efficient protein expression in both the spleen and lymph nodes after intramuscular injections. Moreover, in immunized mice, DCMNP vaccination elicited Spike-specific IgG antibodies, neutralizing antibodies, and Th1-biased SARS-CoV-2-specific cellular immunity. This work presents a powerful vaccine formula using DCMNPs, which represents a promising vaccine candidate for further research and development.

RNA Nanomedicine: Delivery Strategies and Applications

Delivery of RNA using nanomaterials has emerged as a new modality to expand therapeutic applications in biomedical research. However, the delivery of RNA presents unique challenges due to its susceptibility to degradation and the requirement for efficient intracellular delivery. The integration of nanotechnologies with RNA delivery has addressed many of these challenges. In this review, we discuss different strategies employed in the design and development of nanomaterials for RNA delivery. We also highlight recent advances in the pharmaceutical applications of RNA delivered via nanomaterials. Various nanomaterials, such as lipids, polymers, peptides, nucleic acids, and inorganic nanomaterials, have been utilized for delivering functional RNAs, including messenger RNA (mRNA), small interfering RNA, single guide RNA, and microRNA. Furthermore, the utilization of nanomaterials has expanded the applications of functional RNA as active pharmaceutical ingredients. For instance, the delivery of antigen-encoding mRNA using nanomaterials enables the transient expression of vaccine antigens, leading to immunogenicity and prevention against infectious diseases. Additionally, nanomaterial-mediated RNA delivery has been investigated for engineering cells to express exogenous functional proteins. Nanomaterials have also been employed for co-delivering single guide RNA and mRNA to facilitate gene editing of genetic diseases. Apart from the progress made in RNA medicine, we discuss the current challenges and future directions in this field.

On the mechanism of tissue-selective gene delivery by lipid nanoparticles

The era of nucleic acid nanomedicine has arrived, as evidenced by Patisiran, a small interfering RNA (siRNA) encapsulated lipid nanoparticle (LNP), and mRNA-loaded LNPs used in COVID-19 vaccines. The diversity of nano-designs for delivering nucleic acid molecules tested in Phase II/III clinical trials reflects the potential of these technologies. These breakthroughs in non-viral gene delivery, including the use of LNPs, have attracted substantial interest worldwide for developing more effective drugs. A next step in this field is to target tissues other than the liver, which requires significant research efforts and material development. However, mechanistic studies in this area are lacking. This study compares two types of LNPs with different tissue-selectivity for delivering plasmid DNA (pDNA), one being liver-selective and the other spleen-selective, in an effort to understand the mechanisms responsible for differences in gene expression of delivered genes. We observed little difference in the biodistribution of these two LNPs despite the 100-1000-fold differences in gene expression. We then quantified the amount of delivered pDNA and mRNA expression in each tissue by quantitative real-time PCR (qPCR) to evaluate various intracellular processes, such as nuclear delivery, transcription and translation. The results showed a >100-fold difference in the translation step but there were little differences in amount of pDNA delivered to the nucleus or the amount of mRNA expression for the two LNP deliveries. Our findings suggest that endogenous factors affect gene expression efficiency not the extent of biodistribution.

Ushering in the era of tRNA medicines

Long viewed as an intermediary in protein translation, there is a growing awareness that tRNAs are capable of myriad other biological functions linked to human health and disease. These emerging roles could be tapped to leverage tRNAs as diagnostic biomarkers, therapeutic targets, or even as novel medicines. Furthermore, the growing array of tRNA-derived fragments, which modulate an increasingly broad spectrum of cellular pathways, is expanding this opportunity. Together, these molecules offer drug developers the chance to modulate the impact of mutations and to alter cell homeostasis. Moreover, because a single therapeutic tRNA can facilitate readthrough of a genetic mutation shared across multiple genes, such medicines afford the opportunity to define patient populations not based on their clinical presentation or mutated gene but rather on the mutation itself. This approach could potentially transform the treatment of patients with rare and ultrarare diseases. In this review, we explore the diverse biology of tRNA and its fragments, examining the past and present challenges to provide a comprehensive understanding of the molecules and their therapeutic potential.

The promise of RNA-based therapeutics in revolutionizing heart failure management - a narrative review of current evidence

This review elucidates the potential of RNA-based therapeutics to revolutionize heart failure (HF) management. Through a comprehensive analysis of relevant studies, this review reveals the promising prospects of these novel interventions in personalized treatment strategies, targeted modulation of specific molecular pathways, and the attainment of synergistic effects via combination therapies. Moreover, the regenerative capacity of RNA-based therapeutics for cardiac repair and the inherent advantages associated with noninvasive routes of administration are explored. Additionally, the studies accentuate the significance of diligent monitoring of disease progression and treatment response, ensuring safety and considering long-term outcomes. While ongoing research endeavours and technological advancements persist in addressing extant challenges and limitations, the transformative potential of RNA-based therapeutics in HF management offers a beacon of hope for enhanced patient outcomes.

Therapeutic extracellular vesicle production is substantially increased by inhibition of cellular cholesterol biosynthesis

Extracellular vesicles (EVs) are a new therapeutic modality with the promise to treat many diseases through their ability to deliver diverse molecular cargo. As with other emerging modalities transitioning into the industrialization phase, all aspects of the manufacturing process are rich with opportunities to enhance the ability to deliver these medicines to patients. With the goal of improving cell culture EV productivity, we have utilized high throughput siRNA screens to identify the underlying genetic pathways that regulate EV productivity to inform rational host cell line engineering and media development approaches. The screens identified multiple metabolic pathways of potential interest; one of which was validated and shown to be a ready implementable, cost-effective strategy to increase EV titers. We show that both EV volumetric and specific productivity from HEK293 and CHO-S were increased in a dose and cell line-dependent manner up to ninefold when cholesterol synthesis was inhibited by the inclusion of statins in the cell culture media. In addition, we show in response to statin treatment, elevation of EV markers in mesenchymal stem cell (MSC) cell culture media suggesting this approach can also be applicable to MSC EVs. Furthermore, we show that the EVs produced from statin-treated HEK293 cultures are effectively loaded by both endogenous and exogenous loading methods and have equivalent in vitro or in vivo potency relative to EVs from untreated cultures.

Biomimetic Mineralized CRISPR/Cas RNA Nanoparticles for Efficient Tumor-Specific Multiplex Gene Editing

CRISPR/Cas9 systems have great potential to achieve sophisticated gene therapy and cell engineering by editing multiple genomic loci. However, to achieve efficient multiplex gene editing, the delivery system needs adequate capacity to transfect all CRISPR/Cas9 RNA species at the required stoichiometry into the cytosol of each individual cell. Herein, inspired by biomineralization in nature, we develop an all-in-one biomimetic mineralized CRISPR/Cas9 RNA delivery system. This system allows for precise control over the coencapsulation ratio between Cas9 mRNA and multiple sgRNAs, while also exhibiting a high RNA loading capacity. In addition, it enhances the storage stability of RNA at 4 °C for up to one month, and the surface of the nanoparticles can be easily functionalized for precise targeting of RNA nanoparticles in vivo at nonliver sites. Based on the above characteristics, as a proof-of-concept, our system was able to achieve significant gene-editing at each target gene (Survivin: 31.9%, PLK1: 24.41%, HPV: 23.2%) and promote apoptosis of HeLa cells in the mouse model, inhibiting tumor growth without obvious off-target effects in liver tissue. This system addresses various challenges associated with multicomponent RNA delivery in vivo, providing an innovative strategy for the RNA-based CRISPR/Cas9 gene editing.

Recent Advances in Messenger Ribonucleic Acid (mRNA) Vaccines and Their Delivery Systems: A Review

Messenger ribonucleic acid (mRNA) was found as the intermediary that transfers genetic information from DNA to ribosomes for protein synthesis in 1961. The emergency use authorization of the two covid-19 mRNA vaccines, BNT162b2 and mRNA-1273, is a significant achievement in the history of vaccine development. Because they are generated in a cell-free environment using the in vitro transcription (IVT) process, mRNA vaccines are risk-free. Moreover, chemical modifications to the mRNA molecule, such as cap structures and changed nucleosides, have proved critical in overcoming immunogenicity concerns, achieving sustained stability, and achieving effective, accurate protein production in vivo. Several vaccine delivery strategies (including protamine, lipid nanoparticles (LNPs), polymers, nanoemulsions, and cell-based administration) were also optimized to load and transport RNA into the cytosol. LNPs, which are composed of a cationic or a pH-dependent ionizable lipid layer, a polyethylene glycol (PEG) component, phospholipids, and cholesterol, are the most advanced systems for delivering mRNA vaccines. Moreover, modifications of the four components that make up the LNPs showed to increase vaccine effectiveness and reduce side effects. Furthermore, the introduction of biodegradable lipids improved LNP biocompatibility. Furthermore, mRNA-based therapies are expected to be effective treatments for a variety of refractory conditions, including infectious diseases, metabolic genetic diseases, cancer, cardiovascular and cerebrovascular diseases. Therefore, the present review aims to provide the scientific community with up-to-date information on mRNA vaccines and their delivery systems.

From Bench to Bedside: Implications of Lipid Nanoparticle Carrier Reactogenicity for Advancing Nucleic Acid Therapeutics

In biomedical applications, nanomaterial-based delivery vehicles, such as lipid nanoparticles, have emerged as promising instruments for improving the solubility, stability, and encapsulation of various payloads. This article provides a formal review focusing on the reactogenicity of empty lipid nanoparticles used as delivery vehicles, specifically emphasizing their application in mRNA-based therapies. Reactogenicity refers to the adverse immune responses triggered by xenobiotics, including administered lipid nanoparticles, which can lead to undesirable therapeutic outcomes. The key components of lipid nanoparticles, which include ionizable lipids and PEG-lipids, have been identified as significant contributors to their reactogenicity. Therefore, understanding the relationship between lipid nanoparticles, their structural constituents, cytokine production, and resultant reactogenic outcomes is essential to ensure the safe and effective application of lipid nanoparticles in mRNA-based therapies. Although efforts have been made to minimize these adverse reactions, further research and standardization are imperative. By closely monitoring cytokine profiles and assessing reactogenic manifestations through preclinical and clinical studies, researchers can gain valuable insights into the reactogenic effects of lipid nanoparticles and develop strategies to mitigate undesirable reactions. This comprehensive review underscores the importance of investigating lipid nanoparticle reactogenicity and its implications for the development of mRNA-lipid nanoparticle therapeutics in various applications beyond vaccine development.

The use of RNA-based treatments in the field of cancer immunotherapy

Over the past several decades, mRNA vaccines have evolved from a theoretical concept to a clinical reality. These vaccines offer several advantages over traditional vaccine techniques, including their high potency, rapid development, low-cost manufacturing, and safe administration. However, until recently, concerns over the instability and inefficient distribution of mRNA in vivo have limited their utility. Fortunately, recent technological advancements have mostly resolved these concerns, resulting in the development of numerous mRNA vaccination platforms for infectious diseases and various types of cancer. These platforms have shown promising outcomes in both animal models and humans. This study highlights the potential of mRNA vaccines as a promising alternative approach to conventional vaccine techniques and cancer treatment. This review article aims to provide a thorough and detailed examination of mRNA vaccines, including their mechanisms of action and potential applications in cancer immunotherapy. Additionally, the article will analyze the current state of mRNA vaccine technology and highlight future directions for the development and implementation of this promising vaccine platform as a mainstream therapeutic option. The review will also discuss potential challenges and limitations of mRNA vaccines, such as their stability and in vivo distribution, and suggest ways to overcome these issues. By providing a comprehensive overview and critical analysis of mRNA vaccines, this review aims to contribute to the advancement of this innovative approach to cancer treatment.

Biodegradable lipophilic polymeric mRNA nanoparticles for ligand-free targeting of splenic dendritic cells for cancer vaccination

Nanoparticle (NP)-based mRNA cancer vaccines hold great promise to realize personalized cancer treatments. To advance this technology requires delivery formulations for efficient intracellular delivery to antigen-presenting cells. We developed a class of bioreducible lipophilic poly(beta-amino ester) nanocarriers with quadpolymer architecture. The platform is agnostic to the mRNA sequence, with one-step self-assembly allowing for delivery of multiple antigen-encoding mRNAs as well as codelivery of nucleic acid-based adjuvants. We examined structure-function relationships for NP-mediated mRNA delivery to dendritic cells (DCs) and identified that a lipid subunit of the polymer structure was critical. Following intravenous administration, the engineered NP design facilitated targeted delivery to the spleen and preferential transfection of DCs without the need for surface functionalization with targeting ligands. Treatment with engineered NPs codelivering antigen-encoding mRNA and toll-like receptor agonist adjuvants led to robust antigen-specific CD8+ T cell responses, resulting in efficient antitumor therapy in in vivo models of murine melanoma and colon adenocarcinoma.

Nanoparticle-based immunotherapeutics: from the properties of nanocores to the differential effects of administration routes

The engagement with the immune system is one of the main cornerstones in the development of nanotechnologies for therapy and diagnostics. Recent advances have made possible the tuning of features like size, shape and biomolecular modifications that influence such interactions, however, the capabilities for immune modulation of nanoparticles are still not well defined and exploited. This review focuses on recent advances made in preclinical research for the application of nanoparticles to modulate immune responses, and the main features making them relevant for such applications. We review and discuss newest evidence in the field, which include in vivo experiments with an extensive physicochemical characterization as well as detailed study of the induced immune response. We emphasize the need of incorporating knowledge about immune response development and regulation in the design and application of nanoparticles, including the effect by parameters such as the administration route and the differential interactions with immune subsets.

Nanoparticle stereochemistry-dependent endocytic processing improves in vivo mRNA delivery

Stereochemistry can alter small-molecule pharmacokinetics, safety and efficacy. However, it is unclear whether the stereochemistry of a single compound within a multicomponent colloid such as a lipid nanoparticle (LNP) can influence its activity in vivo. Here we report that LNPs containing stereopure 20α-hydroxycholesterol (20α) delivered mRNA to liver cells up to 3-fold more potently than LNPs containing a mixture of both 20α- and 20β-hydroxycholesterols (20mix). This effect was not driven by LNP physiochemical traits. Instead, in vivo single-cell RNA sequencing and imaging revealed that 20mix LNPs were sorted into phagocytic pathways more than 20α LNPs, resulting in key differences between LNP biodistribution and subsequent LNP functional delivery. These data are consistent with the fact that nanoparticle biodistribution is necessary, but not sufficient, for mRNA delivery, and that stereochemistry-dependent interactions between LNPs and target cells can improve mRNA delivery.

The Transcriptional Response to Lung-Targeting Lipid Nanoparticles in Vivo

Lipid nanoparticles (LNPs) have delivered RNA to hepatocytes in patients, underscoring the potential impact of nonliver delivery. Scientists can shift LNP tropism to the lung by adding cationic helper lipids; however, the biological response to these LNPs remains understudied. To evaluate the hypothesis that charged LNPs lead to differential cellular responses, we quantified how 137 LNPs delivered mRNA to 19 cell types in vivo. Consistent with previous studies, we observed helper lipid-dependent tropism. After identifying and individually characterizing three LNPs that targeted different tissues, we studied the in vivo transcriptomic response to these using single-cell RNA sequencing. Out of 835 potential pathways, 27 were upregulated in the lung, and of these 27, 19 were related to either RNA or protein metabolism. These data suggest that endogenous cellular RNA and protein machinery affects mRNA delivery to the lung in vivo.

Lipid nanoparticles technology in vaccines: Shaping the future of prophylactic medicine

Throughout decades, the intrinsic power of the immune system to fight pathogens has inspired researchers to develop techniques that enable the prevention or treatment of infections via boosting the immune response against the target pathogens, which has led to the evolution of vaccines. The recruitment of Lipid nanoparticles (LNPs) as either vaccine delivery platforms or immunogenic modalities has witnessed a breakthrough recently, which has been crowned with the development of effective LNPs-based vaccines against COVID-19. In the current article, we discuss some principles of such a technology, with a special focus on the technical aspects from a translational perspective. Representative examples of LNPs-based vaccines against cancer, COVID-19, as well as other infectious diseases, autoimmune diseases, and allergies are highlighted, considering the challenges and promises. Lastly, the key features that can improve the clinical translation of this area of endeavor are inspired.

A Polymeric Nanoparticle Formulation for Targeted mRNA Delivery to Fibroblasts

Messenger RNA (mRNA)-based therapies offer enhanced control over the production of therapeutic proteins for many diseases. Their clinical implementation warrants formulations capable of delivering them safely and effectively to target sites. Owing to their chemical versatility, polymeric nanoparticles can be designed by combinatorial synthesis of different ionizable, cationic, and aromatic moieties to modulate cell targeting, using inexpensive formulation steps. Herein, 152 formulations are evaluated by high-throughput screening using a reporter fibroblast model sensitive to functional delivery of mRNA encoding Cre recombinase. Using in vitro and in vivo models, a polymeric nanoformulation based on the combination of 3 specific monomers is identified to transfect fibroblasts much more effectively than other cell types populating the skin, with superior performance than lipid-based transfection agents in the delivery of Cas9 mRNA and guide RNA. This tropism can be explained by receptor-mediated endocytosis, involving CD26 and FAP, which are overexpressed in profibrotic fibroblasts. Structure-activity analysis reveals that efficient mRNA delivery required the combination of high buffering capacity and low mRNA binding affinity for rapid release upon endosomal escape. These results highlight the use of high-throughput screening to rapidly identify chemical features towards the design of highly efficient mRNA delivery systems targeting fibrotic diseases.

mRNA-From COVID-19 Treatment to Cancer Immunotherapy

This review provides an overview covering mRNA from its use in the COVID-19 pandemic to cancer immunotherapy, starting from the selection of appropriate antigens, tumor-associated and tumor-specific antigens, neoantigens, the basics of optimizing the mRNA molecule in terms of stability, efficacy, and tolerability, choosing the best formulation and the optimal route of administration, to summarizing current clinical trials of mRNA vaccines in tumor therapy.

Intradermally delivered mRNA-encapsulating extracellular vesicles for collagen-replacement therapy

The success of messenger RNA therapeutics largely depends on the availability of delivery systems that enable the safe, effective and stable translation of genetic material into functional proteins. Here we show that extracellular vesicles (EVs) produced via cellular nanoporation from human dermal fibroblasts, and encapsulating mRNA encoding for extracellular-matrix α1 type-I collagen (COL1A1) induced the formation of collagen-protein grafts and reduced wrinkle formation in the collagen-depleted dermal tissue of mice with photoaged skin. We also show that the intradermal delivery of the mRNA-loaded EVs via a microneedle array led to the prolonged and more uniform synthesis and replacement of collagen in the dermis of the animals. The intradermal delivery of EV-based COL1A1 mRNA may make for an effective protein-replacement therapy for the treatment of photoaged skin.

Poly (beta-amino ester) as an in vivo nanocarrier for therapeutic nucleic acids

Therapeutic nucleic acids are an emerging class of therapy for treating various diseases through immunomodulation, protein replacement, gene editing, and genetic engineering. However, they need a vector to effectively and safely reach the target cells. Most gene and cell therapies rely on ex vivo gene delivery, which is laborious, time-consuming, and costly; therefore, devising a systematic vector for effective and safe in vivo delivery of therapeutic nucleic acids is required to target the cells of interest in an efficient manner. Synthetic nanoparticle vector poly beta amino ester (PBAE), a class of degradable polymer, is a promising candidate for in vivo gene delivery. PBAE is considered the most potent in vivo vector due to its excellent transfection performance and biodegradability. PBAE nanoparticles showed tunable charge density, diverse structural characteristics, excellent encapsulation capacity, high stability, stimuli-responsive release, site-specific delivery, potent binding to nucleic acids, flexible binding ability to various conjugates, and effective endosomal escape. These unique properties of PBAE are an essential contribution to in vivo gene delivery. The current review discusses each of the components used for PBAE synthesis and the impact of various environmental and physicochemical factors of the body on PBAE nanocarrier.

Substituting racemic ionizable lipids with stereopure ionizable lipids can increase mRNA delivery

Lipid nanoparticles (LNPs) have delivered siRNA and mRNA drugs in humans, underscoring the potential impact of improving the therapeutic window of next-generation LNPs. To increase the LNP therapeutic window, we applied lessons from small-molecule chemistry to ionizable lipid design. Specifically, given that stereochemistry often influences small-molecule safety and pharmacokinetics, we hypothesized that the stereochemistry of lipids within an LNP would influence mRNA delivery. We tested this hypothesis in vivo using 128 novel LNPs that included stereopure derivatives of C12-200, an ionizable lipid that when formulated into LNPs delivers RNA in mice and non-human primates but is not used clinically due to its poor tolerability. We found that a novel C12-200-S LNP delivered up to 2.8-fold and 6.1-fold more mRNA in vivo than its racemic and C12-200-R controls, respectively. To identify the potential causes leading to increased delivery, we quantified LNP biophysical traits and concluded that these did not change with stereochemistry. Instead, we found that stereopure LNPs were better tolerated than racemic LNPs in vivo. These data suggest that LNP-mediated mRNA delivery can be improved by designing LNPs to include stereopure ionizable lipids.

Nonclinical Safety Assessment of Lipid Nanoparticle-and Emulsion-Based Self-Amplifying mRNA Vaccines in Rats

Vaccines containing mRNA with the capacity to self-amplify represent an alternative to the mRNA vaccines that came to prominence during the COVID-19 pandemic. To gain further insights on the safety profile of self-amplifying mRNA- (SAM-) vaccines, this preclinical toxicology study in rats evaluated the effect of (i) the type of delivery system (lipid nanoparticle [LNP] vs cationic nano-emulsion [CNE]); (ii) antigen-encoding sequence (rabies glycoprotein G vs SARS-CoV-2 Spike); and (iii) RNA amplification. Further analyses also evaluated gene expression in peripheral blood after vaccination, and the biodistribution of vaccine RNA. The SAM vaccines administered as two doses 2-weeks apart had acceptable safety profiles in rats, with respect to clinical signs, blood biochemistry, and macroscopic and microscopic pathology. A transient increase in ALT/AST ratio occurred only in female rats and in the absence of muscle and liver damage was dependent on RNA amplification and appeared related to the greater quantities of vaccine RNA in the muscle and livers of female rats vs male rats. The RNA and delivery-vehicle components, but not the nature of the antigen-coding sequence or the requirement for RNA amplification, affected aspects of the stimulation of innate-immune activity, which was consistent with the transient activation of type I and type II interferon signaling. The delivery vehicle, LNP, differed from CNE as vaccine RNA in CNE compositions appeared independently to stimulate innate-immune activity at 4 hours after vaccination. Our analysis supports further studies to assess whether these differences in innate-immune activity affect safety and efficacy of the SAM vaccine.

Regulatory circular RNAs in viral diseases: applications in diagnosis and therapy

Circular RNA (circRNA) forms closed loops via back-splicing in precursor mRNA, resisting exonuclease degradation. In higher eukaryotes, protein-coding genes create circRNAs through exon back-splicing. Unlike mRNAs, circRNAs possess unique production and structural traits, bestowing distinct cellular functions and biomedical potential. In this review, we explore the pivotal roles of viral circRNAs and associated RNA in various biological processes. Analysing the interactions between viral circRNA and host cellular machinery yields fresh insights into antiviral immunity, catalysing the development of potential therapeutics. Furthermore, circRNAs serve as enduring biomarkers in viral diseases due to their stable translation within specific tissues. Additionally, a deeper understanding of translational circRNA could expedite the establishment of circRNA-based expression platforms, meeting the rising demand for broad-spectrum viral vaccines. We also highlight the applications of circular RNA in biomarker studies as well as circRNA-based therapeutics. Prospectively, we expect a technological revolution in combating viral infections using circRNA.

The Extent to Which Lipid Nanoparticles Require Apolipoprotein E and Low-Density Lipoprotein Receptor for Delivery Changes with Ionizable Lipid Structure

Lipid nanoparticles (LNPs) have delivered therapeutic RNA to hepatocytes in humans. Adsorption of apolipoprotein E (ApoE) onto these clinical LNP-mRNA drugs has been shown to facilitate hepatocyte entry via the low-density lipoprotein receptor (LDLR). Since ApoE-LDLR trafficking is conserved in mice, non-human primates, and humans, characterizing this mechanism eased clinical transition. Recently, LNPs have delivered mRNA to non-hepatocytes in mice and non-human primates, suggesting they can target new cell types via ApoE- and LDLR-independent pathways. To test this hypothesis, we quantified how 60 LNPs delivered mRNA with cell type resolution in wild-type mice and three knockout mouse strains related to lipid trafficking: ApoE^-/-, LDLR^-/-, and PCSK9^-/-. These data suggest that the hydrophobic tail length of diketopiperazine-based lipids can be changed to drive ApoE- and LDLR-independent delivery in vivo. More broadly, the results support the hypothesis that endogenous LNP trafficking can be tuned by modifying lipid chemistry.

The landscape of mRNA nanomedicine

Messenger RNA (mRNA) is an emerging class of therapeutic agent for the prevention and treatment of a wide range of diseases. The recent success of the two highly efficacious mRNA vaccines produced by Moderna and Pfizer-BioNTech to protect against COVID-19 highlights the huge potential of mRNA technology for revolutionizing life science and medical research. Challenges related to mRNA stability and immunogenicity, as well as in vivo delivery and the ability to cross multiple biological barriers, have been largely addressed by recent progress in mRNA engineering and delivery. In this Review, we present the latest advances and innovations in the growing field of mRNA nanomedicine, in the context of ongoing clinical translation and future directions to improve clinical efficacy.

mRNA Vaccines Against SARS-CoV-2 Variants Delivered by Lipid Nanoparticles Based on Novel Ionizable Lipids

SARS-CoV-2 variants are now still challenging all the approved vaccines, including mRNA vaccines. There is an urgent need to develop new generation mRNA vaccines with more powerful efficacy and better safety against SARS-CoV-2 variants. In this study, a new set of ionizable lipids named 4N4T are constructed and applied to form novel lipid nanoparticles called 4N4T-LNPs. Leading 4N4T-LNPs exhibit much higher mRNA translation efficiency than the approved SM-102-LNPs. To test the effectiveness of the novel delivery system, the DS mRNA encoding the full-length S protein of the SARS-CoV-2 variant is synthesized and loaded in 4N4T-LNPs. The obtained 4N4T-DS mRNA vaccines successfully trigger robust and durable humoral immune responses against SARS-CoV-2 and its variants including Delta and Omicron. Importantly, the novel vaccines have higher RBD-specific IgG titers and neutralizing antibody titers than SM-102-based DS mRNA vaccine. Besides, for the first time, the types of mRNA vaccine-induced neutralizing antibodies are found to be influenced by the chemical structure of ionizable lipids. 4N4T-DS mRNA vaccines also induce strong Th1-skewed T cell responses and have good safety. This work provides a novel vehicle for mRNA delivery that is more effective than the approved LNPs and shows its application in vaccines against SARS-CoV-2 variants.

Pre-exposure to mRNA-LNP inhibits adaptive immune responses and alters innate immune fitness in an inheritable fashion

Hundreds of millions of SARS-CoV-2 mRNA-LNP vaccine doses have already been administered to humans. However, we lack a comprehensive understanding of the immune effects of this platform. The mRNA-LNP-based SARS-CoV-2 vaccine is highly inflammatory, and its synthetic ionizable lipid component responsible for the induction of inflammation has a long in vivo half-life. Since chronic inflammation can lead to immune exhaustion and non-responsiveness, we sought to determine the effects of pre-exposure to the mRNA-LNP on adaptive immune responses and innate immune fitness. We found that pre-exposure to mRNA-LNPs or LNP alone led to long-term inhibition of the adaptive immune response, which could be overcome using standard adjuvants. On the other hand, we report that after pre-exposure to mRNA-LNPs, the resistance of mice to heterologous infections with influenza virus increased while resistance to Candida albicans decreased. The diminished resistance to Candida albicans correlated with a general decrease in blood neutrophil percentages. Interestingly, mice pre-exposed to the mRNA-LNP platform can pass down the acquired immune traits to their offspring, providing better protection against influenza. In summary, the mRNA-LNP vaccine platform induces long-term unexpected immunological changes affecting both adaptive immune responses and heterologous protection against infections. Thus, our studies highlight the need for more research to determine this platform's true impact on human health.

Influence of protein corona on the interaction of glycogen-siRNA constructs with ex vivo human blood immune cells

Glycogen-nucleic acid constructs i.e., glycoplexes are emerging promising platforms for the alteration of gene expression and transcription. Understanding the interaction of glycoplexes with human blood components, such as serum proteins and peripheral blood mononuclear cells (PBMCs), is important to overcome immune cell activation and control biodistribution upon administration of the glycoplexes in vivo. Herein, we investigated the interactions of polyethylene glycol (PEG)ylated and non-PEGylated glycoplexes carrying siRNA molecules with PBMCs isolated from the blood of healthy donors. We found that both types of glycoplexes were non-toxic and were primarily phagocytosed by monocytes without triggering a pro-inflammatory interleukin 6 cytokine production. Furthermore, we investigated the role of the protein corona on controlling the internalization efficiency in immune cells - we found that the adsorption of serum proteins, in particular haptoglobin, alpha-1-antitrypsin and apolipoprotein A-II, onto the non-PEGylated glycoplexes, significantly reduced the uptake of the glycoplexes by PBMCs. Moreover, the non-PEGylated glycoplexes were efficient in the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) knockdown in monocytic THP-1 cell line. This study provides an insight into the rational design of glycogen-based nanocarriers for the safe delivery of siRNA without eliciting unwanted immune cell activation and efficient siRNA activity upon its delivery.

Helper-Polymer Based Five-Element Nanoparticles (FNPs) for Lung-Specific mRNA Delivery with Long-Term Stability after Lyophilization

Lipid nanoparticles (LNPs) carrying therapeutic mRNAs hold great promise in treating lung-associated diseases like viral infections, tumors, and genetic disorders. However, because of their thermodynamically unstable nature, traditional LNPs carrying mRNAs need to be stored at low temperatures, which hinders their prevalence. Herein, an efficient lung-specific mRNA delivery platform named five-element nanoparticles (FNPs) is developed in which helper-polymer poly(β-amino esters) (PBAEs) and DOTAP are used in combination. The new strategy endows FNPs with high stability by increasing the charge repulsion between nanoparticles and the binding force of the aliphatic chains within the nanoparticles. The structure-activity relationship (SAR) shows that PBAEs with E1 end-caps, higher degrees of polymerization, and longer alkyl side chains exhibit higher hit rates. Lyophilized FNP formulations can be stably stored at 4 °C for at least 6 months. Overall, a novel delivery platform with high efficiency, specificity, and stability was developed for advancing mRNA-based therapies for lung-associated diseases.