Visualization of early events in mRNA vaccine delivery in non-human primates via PET–CT and near-infrared imaging

RNA vaccines: The dawn of a new age for tuberculosis?

Since 2019, there has been a growing focus on mRNA vaccines for infectious disease prevention, particularly following the emergence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). mRNA vaccines offer advantages such as rapid production and the ability to induce robust cellular and antibody responses, which are essential for combating infections that require cell-mediated immunity, including Tuberculosis (TB). This review explores recent progress in TB mRNA vaccines and addresses several key areas: (1) the urgent need for new TB vaccines; (2) current advancements in TB vaccine development, and the advantages and challenges of mRNA technology; (3) the design and characteristics of TB mRNA vaccines; (4) the immunological mechanisms of TB mRNA vaccines; (5) manufacturing processes for TB mRNA vaccines; and (6) safety and regulatory considerations. This interdisciplinary review aims to provide insights for researchers working to address critical questions in TB mRNA vaccine development.

Engineered multi-domain lipid nanoparticles for targeted delivery

Engineered lipid nanoparticles (LNPs) represent a breakthrough in targeted drug delivery, enabling precise spatiotemporal control essential to treat complex diseases such as cancer and genetic disorders. However, the complexity of the delivery process-spanning diverse targeting strategies and biological barriers-poses significant challenges to optimizing their design. To address these, this review introduces a multi-domain framework that dissects LNPs into four domains: structure, surface, payload, and environment. Engineering challenges, functional mechanisms, and characterization strategies are analyzed across each domain, along with a discussion of advantages, limitations, and in vivo fate (e.g., biodistribution and clearance). The framework also facilitates comparisons with natural exosomes and exploration of alternative administration routes, such as intranasal and intraocular delivery. We highlight current characterization techniques, such as cryo-TEM and multiscale molecular dynamics simulations, as well as the recently emerging artificial intelligence (AI) applications-ranging from LNP structure screening to the prospective use of generative models for de novo design beyond traditional experimental and simulation paradigms. Finally, we examine how engineered LNPs integrate active, passive, endogenous, and stimuli-responsive targeting mechanisms to achieve programmable delivery, potentially surpassing biological sophistication in therapeutic performance.

Investigating the stability of RNA-lipid nanoparticles in biological fluids: Unveiling its crucial role for understanding LNP performance

Lipid nanoparticles (LNPs) are the most established and clinically advanced platform for RNA delivery. While significant efforts have been made to improve RNA delivery efficiency for improved protein production, the interplay between physiological stability, target specificity, and therapeutic efficacy of RNA-LNPs remains largely unexplored. This review highlights the crucial, yet often overlooked, impact of in vivo stability or instability of RNA-LNPs in contact with biological fluids on delivery performance. We discuss the various factors, including lipid composition, particle surface properties and interactions with proteins in physiological conditions, and provide an overview of the current methods for assessing RNA-LNP stability in biological fluids, such as dynamic laser light scattering, liquid chromatography, and fluorescent and radiolabeled techniques. In the final part, we propose strategies for enhancing stability, with a focus on shielding lipids. Therefore, this work highlights the importance of investigating and understanding the balance between stability and instability of LNPs in the biological context to achieve a more meaningful correlation between formulation properties and in vivo performance.

Enhanced mRNA delivery via incorporating hydrophobic amines into lipid nanoparticles

Lipid nanoparticles (LNPs) have shown promising performance in mRNA delivery. Nevertheless, a thorough understanding of the relationship between mRNA delivery efficacy and the structure of LNPs remains imperative. In this study, we systematically investigated the effects of additional hydrophobic amines on the physicochemical properties of mRNA LNPs and their delivery efficacy. The results indicated that this influence depended on the chemical structure of the additional amines and the structure of the lipid carriers. The appropriate addition of the hydrophobic amine 2C8 to lipid carriers with structural 2C8 or 2C6 tails significantly increased their mRNA delivery efficiency. In contrast, the addition of hydrophobic amine C18 to LNPs resulted in a decrease in mRNA delivery efficiency, while the addition of hydrophobic amines 2C6 and C8, as well as alkanes C12' and C16', had relatively little effect on mRNA delivery. Further investigations demonstrated that the appropriate addition of 2C8 could reduce LNP size, moderate internal hydrophobicity and LNP stability, facilitate mRNA release, enhance cellular uptake, and improve intracellular transportation of LNPs, thereby achieving superior mRNA delivery efficiency. These findings highlight the important role of additional hydrophobic amines in mRNA delivery with LNPs and provide valuable insights for the advancement of mRNA delivery carriers.

Re-adenylation by TENT5A enhances efficacy of SARS-CoV-2 mRNA vaccines

Despite the widespread use of mRNA vaccines against COVID-19, little is known about the metabolism of therapeutic RNAs. Here we use nanopore sequencing1-3 to analyse individual therapeutic mRNA molecules, focusing on their poly(A) tails. We show that the Moderna mRNA-1273 vaccine4 has a poly(A) tail of around 100 nucleotides, followed by an mΨCmΨAG sequence. In cell lines, mRNA-1273 undergoes rapid degradation initiated by mΨCmΨAG removal, followed by CCR4-NOT-mediated deadenylation. However, in medically relevant preclinical models, particularly in macrophages, mRNA-1273 poly(A) tails are extended to up to 200 nucleotides by the TENT5A poly(A) polymerase5-7, which is induced by the vaccine. Re-adenylation, which stabilizes target mRNAs, is consistently observed in synthetic mRNAs that encode proteins targeted to the endoplasmic reticulum, such as ovalbumin or antigens from Zika virus8 or the malaria parasite9. The extent of re-adenylation varies: the BioNTech-Pfizer BNT162b2 vaccine10 shows less potent re-adenylation than mRNA-1273, which correlates with a smaller proportion of membrane-associated BNT162b2. This highlights the crucial role of spatial accessibility to ER-resident TENT5A in determining re-adenylation efficiency. In vivo, TENT5A is expressed in immune cells that take up mRNA vaccine, and TENT5A deficiency reduces specific immunoglobulin production for mRNA vaccines after immunization in mice. Overall, our findings reveal a principle for enhancing the efficacy of therapeutic mRNAs, paving the way for improvement.

Diverse priming outcomes under conditions of very rare precursor B cells

Rare naive B cells have special pathogen-recognition features that enable outsized contributions to protective immunity but infrequently participate in immune responses. We investigatee how germline-targeting vaccine delivery and adjuvant selection affect priming of exceptionally rare BG18-like HIV broadly neutralizing antibody-precursor B cells (<1-in-50 million) in non-human primates. Only escalating dose (ED) priming immunization using the saponin adjuvant SMNP elicited detectable BG18-like cells in germinal centers (GCs) compared with other conditions. All groups had strong GC responses, but only ED+SMNP and bolus+SMNP induced BG18-like memory B cells in >50% of animals. One group had vaccine-specific GC responses equivalent to ED+SMNP but scarce BG18-like B cells. Following homologous boosting, BG18-like memory B cells were present in a bolus priming group but with lower somatic hypermutation and affinities than ED+SMNP. This outcome inversely associated with post-prime antibody titers, suggesting antibody feedback significantly influences rare precursor B cell responses. Thus, antigen and inflammatory stimuli extensively impact priming and affinity maturation of rare B cells.

Tailoring mRNA lipid nanoparticles for antifungal vaccines

Vaccination is one of the most effective public health measures for preventing and managing infectious diseases. Despite intensive efforts from the relatively small medical mycology community, developing effective vaccines against invasive fungal infections remains a scientific challenge. This is predominantly due to large antigenic repertoires, complicated life cycles, and the capacity of fungal pathogens to evade the host immune system. Additionally, antifungal vaccines often need to work for at-risk individuals who are immunodeficient. We anticipate that the success of mRNA vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its exploration for various infectious diseases and cancers will usher a new wave of antifungal vaccine research. Herein, we discuss recent advancements and key scientific areas that need to be explored to actualize the development of effective antifungal mRNA vaccines.

The immunogenic potential of an optimized mRNA lipid nanoparticle formulation carrying sequences from virus and protozoan antigens

BACKGROUND

Lipid nanoparticles (LNP) are a safe and effective messenger RNA (mRNA) delivery system for vaccine applications, as shown by the COVID-19 mRNA vaccines. One of the main challenges faced during the development of these vaccines is the production of new and versatile LNP formulations capable of efficient encapsulation and delivery to cells in vivo. This study aimed to develop a new mRNA vaccine formulation that could potentially be used against existing diseases as well as those caused by pathogens that emerge every year.

RESULTS

Using firefly luciferase (Luc) as a reporter mRNA, we evaluated the physical-chemical properties, stability, and biodistribution of an LNP-mRNA formulation produced using a novel lipid composition and a microfluidic organic-aqueous precipitation method. Using mRNAs encoding a dengue virus or a Leishmania infantum antigen, we evaluated the immunogenicity of LNP-mRNA formulations and compared them with the immunization with the corresponding recombinant protein or plasmid-encoded antigens. For all tested LNP-mRNAs, mRNA encapsulation efficiency was higher than 85%, their diameter was around 100 nm, and their polydispersity index was less than 0.3. Following an intramuscular injection of 10 µg of the LNP-Luc formulation in mice, we detected luciferase activity in the injection site, as well as in the liver and spleen, as early as 6 h post-administration. LNPs containing mRNA encoding virus and parasite antigens were highly immunogenic, as shown by levels of antigen-specific IgG antibody as well as IFN-γ production by splenocytes of immunized animals that were similar to the levels that resulted from immunization with the corresponding recombinant protein or plasmid DNA.

CONCLUSIONS

Altogether, these results indicate that these novel LNP-mRNA formulations are highly immunogenic and may be used as novel vaccine candidates for different infectious diseases.

A-910823, a squalene-based emulsion adjuvant, enhances robust and broad immune responses of quadrivalent influenza vaccine in ferrets

Robust and broad protective immunity is typically elicited by co-administration of an adjuvant with vaccine antigens. A-910823, a squalene-based emulsion adjuvant, has been approved in Japan. It effectively enhances the humoral and cellular immunity of S-268019-b, a recombinant COVID-19 vaccine; however, the adjuvant effects of A-910823 on other vaccines, including influenza vaccine, have not been evaluated. Here, a ferret model was employed to investigate the adjuvant effects of A-910823 when combined with split-inactivated quadrivalent influenza vaccine (QIV). We demonstrate that combination of A-910823 with QIV enhances the neutralizing antibody titer and its breadth against non-vaccine strains. Also, the protective efficacy of A-910823-adjuvanted QIV against virus challenge has been confirmed. Of note, QIV combined with A-910823 caused only minor detectable side effects, whereas a significant increase in fever was observed after two doses of mRNA-LNP in ferrets. This study provides information on the effectiveness and safety of A-910823-adjuvanted QIV and suggests the usefulness of the ferret model for evaluating vaccine-induced reactogenicity.

Monitoring mRNA vaccine antigen expression in vivo using PET/CT

Noninvasive visualization of the distribution and persistence of mRNA vaccine antigen expression in mammalian systems has implications for the development and evaluation of future mRNA vaccines. Here, we genetically fuse E. coli dihydrofolate reductase (eDHFR) to the delta furin diproline modified SARS-CoV-2 spike glycoprotein (S2P∆f) mRNA vaccine and image its expression in female mice and male non-human primates using [18F]fluoropropyl-trimethoprim ([18F]FP-TMP). Whole body positron emission tomography (PET) imaging revealed transient expression of the vaccine antigen in the injection site and draining lymph nodes (dLNs). Fusion of eDHFR did not impact S2P immunogenicity and no humoral or cellular immune response was detected against eDHFR in either species. In this work, we show that eDHFR can be used as an mRNA-encoded PET reporter gene to monitor the spatiotemporal dynamics of mRNA vaccine antigen expression in vivo. This technique could be applied in clinical translation of future mRNA vaccines or therapeutics.

Visualizing lipid nanoparticle trafficking for mRNA vaccine delivery in non-human primates

mRNA delivered using lipid nanoparticles (LNPs) has become an important subunit vaccine modality, but mechanisms of action for mRNA vaccines remain incompletely understood. Here, we synthesized a metal chelator-lipid conjugate enabling positron emission tomography (PET) tracer labeling of LNP/mRNA vaccines for quantitative visualization of vaccine trafficking in live mice and non-human primates (NHPs). Following intramuscular injection, we observed LNPs distributing through injected muscle tissue, simultaneous with rapid trafficking to draining lymph nodes (dLNs). Deltoid injection of LNPs mimicking human vaccine administration led to stochastic LNP delivery to three different sets of dLNs. LNP uptake in dLNs was confirmed by histology, and cellular analysis of tissues via flow cytometry identified antigen-presenting cells as the primary immune cell type responsible for early LNP uptake and mRNA translation. These results provide insights into the biodistribution of mRNA vaccines administered at clinically relevant doses, injection volumes, and injection sites in an important large animal model for vaccine development.

Improving the Efficacy of Cancer mRNA Vaccines

mRNA vaccines consist of antigen-encoding mRNA, which produces the antigenic protein upon translation. Coupling antigen production with innate immune activation can generate a potent, antigen-specific T-cell response. Clinical reports have demonstrated the ability of mRNA vaccines to elicit an anticancer immune response against various tumor types. Here, we discuss strategies to enhance the potency of mRNA vaccines. We provide an overview of existing knowledge regarding the activation and trafficking mechanisms of mRNA vaccines and share optimization strategies to boost mRNA-mediated antigen production. In addition, we address methods to target mRNA vaccines to dendritic cells and lymph nodes, key initiators of the immune response. Finally, we review strategies for enhancing immune activation using adjuvants compatible with mRNA vaccines. mRNA vaccines offer unique advantages that can be utilized for oncology applications. However, significant work is needed to understand their underlying mechanisms and develop technologies to improve their effectiveness.

Advances in Engineered Phages for Disease Treatment

Phage therapy presents a promising solution for combating multidrug-resistant (MDR) bacterial infections and other bacteria-related diseases, attributed to their innate ability to target and lyse bacteria. Recent clinical successes, particularly in treating MDR-related respiratory and post-surgical infections, validated the therapeutic potential of phage therapy. However, the complex microenvironment within the human body poses significant challenges to phage activity and efficacy in vivo. To overcome these barriers, recent advances in phage engineering have aimed to enhance targeting accuracy, improve stability and survivability, and explore synergistic combinations with other therapeutic modalities. This review provides a comprehensive overview of phage therapy, emphasizing the application of engineered phages in antibacterial therapy, tumor therapy, and vaccine development. Furthermore, the review highlights the current challenges and future trends for advancing phage therapy toward broader clinical applications.

DDO-adjuvanted influenza A virus nucleoprotein mRNA vaccine induces robust humoral and cellular type 1 immune responses and protects mice from challenge

A challenge in viral vaccine development is to produce vaccines that generate both neutralizing antibodies to prevent infection and cytotoxic CD8+ T-cells that target conserved viral proteins and can eliminate infected cells to control virus spread. mRNA technology offers an opportunity to design vaccines based on conserved CD8-targeting epitopes, but achieving robust antigen-specific CD8+ T-cells remains a challenge. Here, we tested the viral-derived oligonucleotide DDO268 as an adjuvant in the context of a model influenza A virus (IAV) nucleoprotein (NP) mRNA vaccine in C57BL/6 mice. DDO268 when co-packaged with mRNA in lipid nanoparticles is sensed by RIG I-like receptors and safely induces local type I interferon (IFN) production followed by dendritic cells type 1 activation and migration to the draining lymph nodes. This early response triggered by DDO268 improved the generation of IgG2c antibodies and antigen-specific Th1 CD4+ and CD8+ T-cells (IFNγ+TNFα+IL2+) that provided enhanced protection against lethal IAV challenge. In addition, the inclusion of DDO268 reduced the antigen dose required to achieve protection. These results highlight the potential of DDO268 as an effective mRNA vaccine adjuvant and show that an IAV NP mRNA/DDO268 vaccine is a promising approach for generating protective immunity against conserved internal IAV epitopes.IMPORTANCEVaccines that generate neutralizing antibodies and cytotoxic CD8+ T-cells targeting conserved epitopes are ideal for effective protection against viruses. mRNA vaccines combined with the right adjuvant offer a promising solution to this challenge. We show that the virus-derived oligonucleotide DDO268 enhances antibody and T-cell responses to an influenza A virus (IAV) nucleoprotein mRNA vaccine in mice. DDO268 safely induces local type I interferon production and stimulates dendritic cell activation providing enhanced protection against IAV challenge. In addition, the adjuvant activity of DDO268 allows for the use of lower antigen doses during vaccination.

mRNA Vaccines: Design Principles, Mechanisms, and Manufacturing-Insights From COVID-19 as a Model for Combating Infectious Diseases

The full approval of two SARS-CoV-2 mRNA vaccines, Comirnaty and Spikevax, has greatly accelerated the development of numerous mRNA vaccine candidates targeting infectious diseases and cancer. mRNA vaccines provide a rapid, safe, and versatile manufacturing process while eliciting strong humoral and cellular immune responses, making them particularly beneficial for addressing emerging pandemics. Recent advancements in modified nucleotides and lipid nanoparticle delivery systems have further emphasized the potential of this vaccine platform. Despite these transformative opportunities, significant improvements are needed to enhance vaccine efficacy, stability, and immunogenicity. This review outlines the fundamentals of mRNA vaccine design, the manufacturing process, and administration strategies, along with various optimization approaches. It also offers a comprehensive overview of the mRNA vaccine candidates developed since the onset of the COVID-19 pandemic, the challenges posed by emerging SARS-CoV-2 variants, and current strategies to address these variants. Finally, we discuss the potential of broad-spectrum and combined mRNA vaccines and examine the challenges and future prospects of the mRNA vaccine platform.

Dendritic-cell-targeting virus-like particles as potent mRNA vaccine carriers

Messenger RNA vaccines lack specificity for dendritic cells (DCs)-the most effective cells at antigen presentation. Here we report the design and performance of a DC-targeting virus-like particle pseudotyped with an engineered Sindbis-virus glycoprotein that recognizes a surface protein on DCs, and packaging mRNA encoding for the Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or for the glycoproteins B and D of herpes simplex virus 1. Injection of the DC-targeting SARS-CoV-2 mRNA vaccine in the footpad of mice led to substantially higher and durable antigen-specific immunoglobulin-G titres and cellular immune responses than untargeted virus-like particles and lipid-nanoparticle formulations. The vaccines also protected the mice from infection with SARS-CoV-2 or with herpes simplex virus 1. Virus-like particles with preferential uptake by DCs may facilitate the development of potent prophylactic and therapeutic vaccines.

Target product profile for cell-based and gene-based therapies to achieve a cure for HIV

This target product profile (TPP) highlights the minimal and optimal characteristics for ex-vivo and in-vivo cell and gene therapy-based products aimed at achieving an HIV cure (ie, durable antiretroviral-free viral control). The need for an effective, safe, scalable, affordable, accessible, and acceptable cure for HIV infection remains a major global priority. The possibilities for cell and gene therapy-based products for an HIV cure are rapidly expanding. In a multi-stakeholder consensus process of clinical experts and civil society, including representatives from low-income and middle-income countries, participants generally agreed on the optimal targets, whereas consensus on the minimal targets was not reached on every parameter. There was less agreement on the minimal targets for ex-vivo than in-vivo therapies given the complexity of ex-vivo interventions. The TPP is planned to be updated at regular intervals. Building a TPP, such as this one, is an important process for stakeholder engagement and aligning ambitions for the development of products that are acceptable to both clinicians and civil society.

Early Diagnosis of Liver Injury and Real-Time Evaluation of Photothermal Therapy Efficacy with a Viscosity-Responsive NIR-II Smart Molecule

The early diagnosis of liver injury and in situ real-time monitoring of tumor therapy efficacy are important for the enhancement of personalized precision therapy but remain challenging due to the lack of reliable in vivo visualization tools with integrated diagnostic, therapeutic, and efficacy monitoring functions. Herein, a smart second near-infrared window (NIR-II) molecule (BITX-OH) is rationally designed for diagnosis and therapy by vinyl-bridging hydroxyl diphenyl xanthine unit and benzo[cd]indolium skeleton. BITX-OH exhibits high selectivity and sensitivity toward viscosity, exhibiting a significant enhancement (1167-fold) in NIR-II fluorescence at 962 nm. With the assistance of BITX-OH and NIR-II fluorescence imaging, early diagnosis and therapeutic evaluation of non-alcoholic fatty liver (NAFL), as well as in-site real-time monitoring of hepatic fibrosis (HF) in live mice have been successfully achieved, which is at least several hours earlier than the typical clinical test. Notably, BITX-OH displays excellent photothermal conversion efficiency when exposed to an 808 nm laser, which can induce tumor ablation and increase viscosity, thereby enhancing NIR-II fluorescence for the real-time evaluation of photothermal therapy (PTT). This viscosity-based "self-monitoring" strategy provides a convenient and reliable platform for timely obtaining therapeutic feedback to avoid over- or under-treatment, thus enabling personalized precision therapy.

Advancing Cancer Vaccines with Radionuclide Imaging

Cancer vaccines are emerged as a beacon of hope in the fight against cancer. However, the lack of effective methods to directly observe their in vivo behavior and monitor therapeutic responses hinders their translation into clinical settings. Radionuclide imaging allows for non-invasive and real-time visualization of vaccine biodistribution and immunological response, offering valuable insights into the effectiveness of cancer vaccines and aiding in patient stratification. In this review, the latest advances and potential applications of radionuclide imaging in cancer vaccines are discussed, with a specific focus on strategies for visualizing the spatiotemporal distribution of vaccines in vivo and monitoring treatment efficacy. The challenges and considerations for implementing these techniques in clinical practice are also highlighted, aiming to inform and guide future research in this field.

Decoding trends in mRNA vaccine research: A comprehensive bibliometric study

BACKGROUND

In recent years, infectious diseases like COVID-19 have had profound global socio-economic impacts. mRNA vaccines have gained prominence due to their rapid development, industrial adaptability, simplicity, and responsiveness to new variants. Notably, the 2023 Nobel Prize in Physiology or Medicine recognized significant contributions to mRNA vaccine research.

METHODS

Our study employed a comprehensive bibliometric analysis using the Web of Science Core Collection (WoSCC) database, encompassing 5,512 papers on mRNA vaccines from 2003 to 2023. We generated cooperation maps, co-citation analyses, and keyword clustering to evaluate the field's developmental history and achievements.

RESULTS

The analysis yielded knowledge maps highlighting countries/institutions, influential authors, frequently published and highly cited journals, and seminal references. Ongoing research hotspots encompass immune responses, stability enhancement, applications in cancer prevention and treatment, and combating infectious diseases using mRNA technology.

CONCLUSIONS

mRNA vaccines represent a transformative development in infectious disease prevention. This study provides insights into the field's growth and identifies key research priorities, facilitating advancements in vaccine technology and addressing future challenges.

mRNA vaccines as cancer therapies

ABSTRACT

Cancer remains a major global health challenge, with conventional treatments like chemotherapy and radiotherapy often hindered by significant side effects, lack of specificity, and limited efficacy in advanced cases. Among emerging therapeutic strategies, mRNA vaccines have shown remarkable potential due to their adaptability, rapid production, and capability for personalized cancer treatment. This review provides an in-depth analysis of messenger RNA (mRNA) vaccines as a therapeutic approach for cancer immunotherapy, focusing on their molecular biology, classification, mechanisms, and clinical studies. Derived from reported literature and data on clinicaltrials.gov, it examines studies on mRNA vaccines encoding tumor-specific antigens (TSAs), tumor-associated antigens (TAAs), immunomodulators, and chimeric antigen receptors (CARs) across various cancer types. The review highlights the ability of mRNA vaccines to encode TSAs and TAAs, enabling personalized cancer treatments, and classifies these vaccines into non-replicating and self-amplifying types. It further explores their mechanisms of action, including antigen presentation and immune activation, while emphasizing findings from clinical studies that demonstrate the potential of mRNA vaccines in cancer therapy. Despite their promise, challenges remain in enhancing delivery systems, improving immunogenicity, and addressing tumor heterogeneity. Overcoming these obstacles will require further investigation to fully harness the potential of mRNA vaccines in personalized cancer treatment.

Diverse priming outcomes under conditions of very rare precursor B cells

Rare B cells can have special pathogen-recognition features giving them the potential to make outsized contributions to protective immunity. However, rare naive B cells infrequently participate in immune responses. We investigated how germline-targeting vaccine antigen delivery and adjuvant selection affect priming of exceptionally rare BG18-like HIV broadly neutralizing antibody-precursor B cells (~1 in 50 million) in non-human primates. Only escalating dose (ED) priming immunization using the saponin adjuvant SMNP elicited detectable BG18-like cells in germinal centers (GCs). All groups had strong GC responses, but only ED+SMNP and bolus+SMNP induced BG18-like memory B cells in >50% of animals. One group had vaccine-specific GC responses equivalent to ED+SMNP, but BG18-like memory B cells were rarely detected. Following homologous boosting, BG18-like memory B cells were more frequent in a bolus priming group, but had lower somatic hypermutation and affinities. This outcome was inversely associated with post-prime antibody titers, suggesting antibody feedback can significantly influence rare precursor B cell responses.

The Immunologic Downsides Associated with the Powerful Translation of Current COVID-19 Vaccine mRNA Can Be Overcome by Mucosal Vaccines

The action of mRNA-based vaccines requires the expression of the antigen in cells targeted by lipid nanoparticle-mRNA complexes. When the vaccine antigen is not fully retained by the producer cells, its local and systemic diffusion can have consequences depending on both the levels of antigen expression and its biological activity. A peculiarity of mRNA-based COVID-19 vaccines is the extraordinarily high amounts of the Spike antigen expressed by the target cells. In addition, vaccine Spike can be shed and bind to ACE-2 cell receptors, thereby inducing responses of pathogenetic significance including the release of soluble factors which, in turn, can dysregulate key immunologic processes. Moreover, the circulatory immune responses triggered by the vaccine Spike is quite powerful, and can lead to effective anti-Spike antibody cross-binding, as well as to the emergence of both auto- and anti-idiotype antibodies. In this paper, the immunologic downsides of the strong efficiency of the translation of the mRNA associated with COVID-19 vaccines are discussed together with the arguments supporting the idea that most of them can be avoided with the advent of next-generation, mucosal COVID-19 vaccines.

Effect of Anti-PEG Antibody on Immune Response of mRNA-Loaded Lipid Nanoparticles

Lipid nanoparticle-encapsulated mRNA (mRNA-LNP) vaccines have been approved for use to combat coronavirus disease 2019 (COVID-19). The mRNA-LNPs contain PEG-conjugated lipids. Clinical studies have reported that mRNA-LNPs induce the production of anti-PEG antibodies, but the anti-PEG antibodies do not affect the production of neutralizing antibodies. However, the detailed influence of anti-PEG antibodies on mRNA-LNP vaccines remains unclear. Therefore, in this study, we prepared ovalbumin (OVA) as a model antigen-encoding mRNA-loaded LNP (mRNA-OVA-LNP), and we determined whether anti-PEG antibodies could affect the antigen-specific immune response of mRNA-OVA-LNP vaccination in mice pretreated with PEG-modified liposomes to induce the production of anti-PEG antibodies. After intramuscular (i.m.) injection of the mRNA-LNP, the anti-PEG antibodies did not change the expression of protein or induction of cytokine and cellular immune response but did slightly increase the induction of antigen-specific antibodies. Furthermore, repeated mRNA-LNP i.m. injection induced the production of anti-PEG IgM and anti-PEG IgG. Our results suggest that mRNA-LNP induces the production of anti-PEG antibodies, but the priming of the antigen-specific immune response of mRNA-LNP vaccination is not notably affected by anti-PEG antibodies.

mRNA vaccines for infectious diseases - advances, challenges and opportunities

The concept of mRNA-based vaccines emerged more than three decades ago. Groundbreaking discoveries and technological advancements over the past 20 years have resolved the major roadblocks that initially delayed application of this new vaccine modality. The rapid development of nucleoside-modified COVID-19 mRNA vaccines demonstrated that this immunization platform is easy to develop, has an acceptable safety profile and can be produced at a large scale. The flexibility and ease of antigen design have enabled mRNA vaccines to enter development for a wide range of viruses as well as for various bacteria and parasites. However, gaps in our knowledge limit the development of next-generation mRNA vaccines with increased potency and safety. A deeper understanding of the mechanisms of action of mRNA vaccines, application of novel technologies enabling rational antigen design, and innovative vaccine delivery strategies and vaccination regimens will likely yield potent novel vaccines against a wide range of pathogens.

DDO-adjuvanted influenza A virus nucleoprotein mRNA vaccine induces robust humoral and cellular type 1 immune responses and protects mice from challenge

A challenge in viral vaccine development is to produce vaccines that generate both neutralizing antibodies to prevent infection and cytotoxic CD8+ T-cells that target conserved viral proteins and can eliminate infected cells to control virus spread. mRNA vaccines offer an opportunity to design vaccines based on conserved CD8-targeting epitopes, but achieving robust antigen-specific CD8+ T-cells remains a challenge. Here we tested the viral-derived oligonucleotide DDO268 as an adjuvant in the context of a model influenza A virus (IAV) nucleoprotein (NP) mRNA vaccine in C57BL/6 mice. DDO268 safely induced local type I interferon (IFN) production, stimulated dendritic cells type 1 (DC1) activation and migration to the draining lymph nodes, and improved the generation of IgG2c antibodies and antigen-specific effector Th1 CD4+ and CD8+ T-cells (IFNγ+TNFα+IL2+) when co-packaged with NP mRNA. The DDO268 adjuvanted vaccine provided enhanced protection against lethal IAV challenge and reduced the antigen dose required to achieve this protection. These results highlight the potential of DDO268 as an effective mRNA vaccine adjuvant and show that an IAV NP mRNA/DDO268 vaccine is a promising approach for generating protective immunity against conserved IAV epitopes.

Maturation of germinal center B cells after influenza virus vaccination in humans

Germinal centers (GC) are microanatomical lymphoid structures where affinity-matured memory B cells and long-lived bone marrow plasma cells are primarily generated. It is unclear how the maturation of B cells within the GC impacts the breadth and durability of B cell responses to influenza vaccination in humans. We used fine needle aspiration of draining lymph nodes to longitudinally track antigen-specific GC B cell responses to seasonal influenza vaccination. Antigen-specific GC B cells persisted for at least 13 wk after vaccination in two out of seven individuals. Monoclonal antibodies (mAbs) derived from persisting GC B cell clones exhibit enhanced binding affinity and breadth to influenza hemagglutinin (HA) antigens compared with related GC clonotypes isolated earlier in the response. Structural studies of early and late GC-derived mAbs from one clonal lineage in complex with H1 and H5 HAs revealed an altered binding footprint. Our study shows that inducing sustained GC reactions after influenza vaccination in humans supports the maturation of responding B cells.

Advancing mRNA Therapeutics: The Role and Future of Nanoparticle Delivery Systems

The coronavirus (COVID-19) pandemic has underscored the critical role of mRNA-based vaccines as powerful, adaptable, readily manufacturable, and safe methodologies for prophylaxis. mRNA-based treatments are emerging as a hopeful avenue for a plethora of conditions, encompassing infectious diseases, cancer, autoimmune diseases, genetic diseases, and rare disorders. Nonetheless, the in vivo delivery of mRNA faces challenges due to its instability, suboptimal delivery, and potential for triggering undesired immune reactions. In this context, the development of effective drug delivery systems, particularly nanoparticles (NPs), is paramount. Tailored with biophysical and chemical properties and susceptible to surface customization, these NPs have demonstrated enhanced mRNA delivery in vivo and led to the approval of several NPs-based formulations for clinical use. Despite these advancements, the necessity for developing a refined, targeted NP delivery system remains imperative. This review comprehensively surveys the biological, translational, and clinical progress in NPs-mediated mRNA therapeutics for both the prevention and treatment of diverse diseases. By addressing critical factors for enhancing existing methodologies, it aims to inform the future development of precise and efficacious mRNA-based therapeutic interventions.

Controlling the speed of antigens transport in dendritic cells improves humoral and cellular immunity for vaccine

Vaccines are an effective intervention for preventing infectious diseases. Currently many vaccine strategies are designed to improve vaccine efficacy by controlling antigen release, typically involving various approaches at the injection site. Yet, strategies for intracellular slow-release of antigens in vaccines are still unexplored. Our study showed that controlling the degradation of antigens in dendritic cells and slowing their transport from early endosomes to lysosomes markedly enhances both antigen-specific T-cell immune responses and germinal center B cell responses. This leads to the establishment of sustained humoral and cellular immunity in vivo imaging and flow cytometry indicated this method not only prolongs antigen retention at the injection site but also enhances antigen concentration in lymph nodes, surpassing traditional Aluminium (Alum) adjuvants. Additionally, we demonstrated that the slow antigen degradation induces stronger follicular helper T cell responses and increases proportions of long-lived plasma cells and memory B cells. Overall, these findings propose that controlling the speed of antigens transport in dendritic cells can significantly boost vaccine efficacy, offering an innovative avenue for developing highly immunogenic next-generation vaccines.

Carboxylesterase Activatable Molecular Probe for Personalized Treatment Guidance by Analyte-Induced Molecular Transformation

Accurate visualization of tumor microenvironment is of great significance for personalized medicine. Here, we develop a near-infrared (NIR) fluorescence/photoacoustic (FL/PA) dual-mode molecular probe (denoted as NIR-CE) for distinguishing tumors based on carboxylesterase (CE) level by an analyte-induced molecular transformation (AIMT) strategy. The recognition moiety for CE activity is the acetyl unit of NIR-CE, generating the pre-product, NIR-CE-OH, which undergoes spontaneous hydrogen atom exchange between the nitrogen atoms in the indole group and the phenol hydroxyl group, eventually transforming into NIR-CE-H. In cellular experiments and in vivo blind studies, the human hepatoma cells and tumors with high level of CE were successfully distinguished by both NIR FL and PA imaging. Our findings provide a new molecular imaging strategy for personalized treatment guidance.

Multi-compartmental diversification of neutralizing antibody lineages dissected in SARS-CoV-2 spike-immunized macaques

The continued evolution of SARS-CoV-2 underscores the need to understand qualitative aspects of the humoral immune response elicited by spike immunization. Here, we combine monoclonal antibody (mAb) isolation with deep B cell receptor (BCR) repertoire sequencing of rhesus macaques immunized with prefusion-stabilized spike glycoprotein. Longitudinal tracing of spike-sorted B cell lineages in multiple immune compartments demonstrates increasing somatic hypermutation and broad dissemination of vaccine-elicited B cells in draining and non-draining lymphoid compartments, including the bone marrow, spleen and, most notably, periaortic lymph nodes. Phylogenetic analysis of spike-specific monoclonal antibody lineages identified through deep repertoire sequencing delineates extensive intra-clonal diversification that shaped neutralizing activity. Structural analysis of the spike in complex with a broadly neutralizing mAb provides a molecular basis for the observed differences in neutralization breadth between clonally related antibodies. Our findings highlight that immunization leads to extensive intra-clonal B cell evolution where members of the same lineage can both retain the original epitope specificity and evolve to recognize additional spike variants not previously encountered.

Reactogenicity Differences between Adjuvanted, Protein-Based and Messenger Ribonucleic Acid (mRNA)-Based COVID-19 Vaccines

Participants in studies investigating COVID-19 vaccines commonly report reactogenicity events, and concerns about side effects may lead to a reluctance to receive updated COVID-19 vaccinations. A real-world, post hoc analysis, observational 2019nCoV-406 study was conducted to examine reactogenicity within the first 2 days after vaccination with either a protein-based vaccine (NVX-CoV2373) or an mRNA vaccine (BNT162b2 or mRNA-1273) in individuals who previously completed a primary series. Propensity score adjustments were conducted to address potential confounding. The analysis included 1130 participants who received a booster dose of NVX-CoV2373 (n = 303) or an mRNA vaccine (n = 827) during the study period. Within the first 2 days after vaccination, solicited systemic reactogenicity events (adjusted) were reported in 60.5% of participants who received NVX-CoV2373 compared with 84.3% of participants who received an mRNA vaccine; moreover, 33.9% and 61.4%, respectively, reported ≥3 systemic reactogenicity symptoms. The adjusted mean (95% CI) number of systemic symptoms was 1.8 (1.6-2.0) and 3.2 (3.0-3.4), respectively. Local reactogenicity events (adjusted) were reported in 73.4% and 91.7% of participants who received NVX-CoV2373 and mRNA vaccines, respectively; the adjusted mean (95% CI) number of local symptoms was 1.5 (1.33-1.61) and 2.4 (2.31-2.52), respectively. These results support the use of adjuvanted, protein-based NVX-CoV2373 as an immunization option with lower reactogenicity than mRNAs.

A Polyplatin with Hands-Holding Near-Infrared-II Fluorophores and Prodrugs at a Precise Ratio for Tracking Drug Fate with Realtime Readout and Treatment Feedback

The in vivo fate of chemotherapeutic drugs plays a vital role in understanding the therapeutic outcome, side effects, and the mechanism. However, the lack of imaging abilities of drugs, tedious labeling processes, and premature leakage of imaging agents result in loss of fidelity between the drugs and imaging signals. Herein, an amphiphilic polymer is created by copolymerization of a near-infrared-II (NIR-II) fluorophore tracer (T) and an anticancer Pt(IV) prodrug (D) of cisplatin in a hand-holding manner into one polymer chain for the first time. The obtained PolyplatinDT is capable of delivering the drugs and the fluorophores concomitantly at a precise D/T ratio, thereby resulting in tracking the platinum drugs and even readout of them in real-time via NIR-II imaging. PolyplatinDT can self-assemble into nanoparticles, referred to as NanoplatinDT. Furthermore, a caspase-3 cleavable peptide that serves as an apoptosis reporter is attached to NanoplatinDT, resulting in NanoplatinDTR that are capable of simultaneously tracking platinum drugs and evaluating the therapeutic efficacy. Overall, it is reported here the design of the first theranostic polymer with anticancer drugs, drug tracers, and drug efficacy reporters that can work in concert to provide insight into the drug fate and mechanism of action.

Visualizing lipid nanoparticle trafficking for mRNA vaccine delivery in non-human primates

mRNA delivered using lipid nanoparticles (LNPs) has become an important subunit vaccine modality, but mechanisms of action for mRNA vaccines remain incompletely understood. Here, we synthesized a metal chelator-lipid conjugate enabling positron emission tomography (PET) tracer labeling of LNP/mRNA vaccines for quantitative visualization of vaccine trafficking in live non-human primates (NHPs). Following i.m. injection, we observed LNPs distributing through injected muscle tissue, simultaneous with rapid trafficking to draining lymph nodes (dLNs). Deltoid injection of LNPs mimicking human vaccine administration led to stochastic LNP delivery to 3 different sets of dLNs. LNP uptake in dLNs was confirmed by histology, and cellular analysis of tissues via flow cytometry identified antigen-presenting cells as the primary cell type responsible for early LNP uptake and mRNA translation. These results provide insights into the biodistribution of mRNA vaccines administered at clinically relevant doses, injection volumes, and injection sites in an important large animal model for vaccine development.

COVID-19: Post infection implications in different age groups, mechanism, diagnosis, effective prevention, treatment, and recommendations

SARS-CoV-2 is a highly contagious pathogen that predominantly caused the COVID-19 pandemic. The persistent effects of COVID-19 are defined as an inflammatory or host response to the virus that begins four weeks after initial infection and persists for an undetermined length of time. Chronic effects are more harmful than acute ones thus, this review explored the long-term effects of the virus on various human organs, including the pulmonary, cardiovascular, and neurological, reproductive, gastrointestinal, musculoskeletal, endocrine, and lymphoid systems and found that SARS-CoV-2 adversely affects these organs of older adults. Regarding diagnosis, the RT-PCR is a gold standard method of diagnosing COVID-19; however, it requires specialized equipment and personnel for performing assays and a long time for results production. Therefore, to overcome these limitations, artificial intelligence employed in imaging and microfluidics technologies is the most promising in diagnosing COVID-19. Pharmacological and non-pharmacological strategies are the most effective treatment for reducing the persistent impacts of COVID-19 by providing immunity to post-COVID-19 patients by reducing cytokine release syndrome, improving the T cell response, and increasing the circulation of activated natural killer and CD8 T cells in blood and tissues, which ultimately reduces fever, nausea, fatigue, and muscle weakness and pain. Vaccines such as inactivated viral, live attenuated viral, protein subunit, viral vectored, mRNA, DNA, or nanoparticle vaccines significantly reduce the adverse long-term virus effects in post-COVID-19 patients; however, no vaccine was reported to provide lifetime protection against COVID-19; consequently, protective measures such as physical separation, mask use, and hand cleansing are promising strategies. This review provides a comprehensive knowledge of the persistent effects of COVID-19 on people of varying ages, as well as diagnosis, treatment, vaccination, and future preventative measures against the spread of SARS-CoV-2.

Distinct dynamics of mRNA LNPs in mice and nonhuman primates revealed by in vivo imaging

The characterization of vaccine distribution to relevant tissues after in vivo administration is critical to understanding their mechanisms of action. Vaccines based on mRNA lipid nanoparticles (LNPs) are now being widely considered against infectious diseases and cancer. Here, we used in vivo imaging approaches to compare the trafficking of two LNP formulations encapsulating mRNA following intramuscular administration: DLin-MC3-DMA (MC3) and the recently developed DOG-IM4. The mRNA formulated in DOG-IM4 LNPs persisted at the injection site, whereas mRNA formulated in MC3 LNPs rapidly migrated to the draining lymph nodes. Furthermore, MC3 LNPs induced the fastest increase in blood neutrophil counts after injection and greater inflammation, as shown by IL-1RA, IL-15, CCL-1, and IL-6 concentrations in nonhuman primate sera. These observations highlight the influence of the nature of the LNP on mRNA vaccine distribution and early immune responses.

[« ReNAissance » of biotherapies with RNA]

Many diseases originate from either the absence or defective expression of a given protein. For some of them, the lacking protein is secreted or can be taken up by cells when delivered exogenously. In such cases, therapies initially involved administering the physiological protein extracted from human tissues. Subsequently, genetic engineering enabled the production of proteins through cell fermentation after introducing the corresponding gene. For many other pathologies, the deficient protein cannot be delivered exogenously. Thus, an endogenous production of the therapeutic protein by the cells themselves is necessary. Messenger RNA (mRNA) technology, like its predecessor DNA, aims to supplement the genetic information needed to produce the therapeutic protein within the cells. However, unlike DNA-based therapies, mRNA transfer allows for transient expression of the protein of interest, which offers an advantage in numerous pathologies. Nonetheless, mastering the quantity, quality, and spatio-temporal regulation of protein production encoded by therapeutic mRNA remains a significant challenge for the development of this approach.

Distinct components of nucleoside-modified messenger RNA vaccines cooperate to instruct efficient germinal center responses

Nucleoside-modified mRNA vaccines elicit protective antibodies through their ability to promote T follicular helper (Tfh) cells. The lipid nanoparticle (LNP) component of mRNA vaccines possesses inherent adjuvant activity. However, to what extent the nucleoside-modified mRNA can be sensed and contribute to Tfh cell responses remains largely undefined. Herein, we deconvoluted the signals induced by LNP and mRNA that instruct dendritic cells (DCs) to promote Tfh cell differentiation. We demonstrated that the nucleoside-modified mRNA drives the production of type I interferons that act on DCs to induce their maturation and the induction of Th1-biased Tfh responses. Conversely, LNP favors the acquisition of a Tfh cell-inducing program in DCs, a stronger Th2 polarization in Tfh cells, and allows for rapid mRNA translation by DCs within the draining lymph node. Our work unravels distinct adjuvant features of mRNA and LNP necessary for the induction of Tfh cells, with implications for vaccine design.

Modulation of innate immune response to mRNA vaccination after SARS-CoV-2 infection or sequential vaccination in humans

mRNA vaccines are likely to become widely used for the prevention of infectious diseases in the future. Nevertheless, a notable gap exists in mechanistic data, particularly concerning the potential effects of sequential mRNA immunization or preexisting immunity on the early innate immune response triggered by vaccination. In this study, healthy adults, with or without documented prior SARS-CoV-2 infection, were vaccinated with the BNT162b2/Comirnaty mRNA vaccine. Prior infection conferred significantly stronger induction of proinflammatory and type I IFN-related gene signatures, serum cytokines, and monocyte expansion after the prime vaccination. The response to the second vaccination further increased the magnitude of the early innate response in both study groups. The third vaccination did not further increase vaccine-induced inflammation. In vitro stimulation of PBMCs with TLR ligands showed no difference in cytokine responses between groups, or before or after prime vaccination, indicating absence of a trained immunity effect. We observed that levels of preexisting antigen-specific CD4 T cells, antibody, and memory B cells correlated with elements of the early innate response to the first vaccination. Our data thereby indicate that preexisting memory formed by infection may augment the innate immune activation induced by mRNA vaccines.

Carrier-free mRNA vaccine induces robust immunity against SARS-CoV-2 in mice and non-human primates without systemic reactogenicity

Carrier-free naked mRNA vaccines may reduce the reactogenicity associated with delivery carriers; however, their effectiveness against infectious diseases has been suboptimal. To boost efficacy, we targeted the skin layer rich in antigen-presenting cells (APCs) and utilized a jet injector. The jet injection efficiently introduced naked mRNA into skin cells, including APCs in mice. Further analyses indicated that APCs, after taking up antigen mRNA in the skin, migrated to the lymph nodes (LNs) for antigen presentation. Additionally, the jet injection provoked localized lymphocyte infiltration in the skin, serving as a physical adjuvant for vaccination. Without a delivery carrier, our approach confined mRNA distribution to the injection site, preventing systemic mRNA leakage and associated systemic proinflammatory reactions. In mouse vaccination, the naked mRNA jet injection elicited robust antigen-specific antibody production over 6 months, along with germinal center formation in LNs and the induction of both CD4- and CD8-positive T cells. By targeting the SARS-CoV-2 spike protein, this approach provided protection against viral challenge. Furthermore, our approach generated neutralizing antibodies against SARS-CoV-2 in non-human primates at levels comparable to those observed in mice. In conclusion, our approach offers a safe and effective option for mRNA vaccines targeting infectious diseases.

Strategies for non-viral vectors targeting organs beyond the liver

In recent years, nanoparticles have evolved to a clinical modality to deliver diverse nucleic acids. Rising interest in nanomedicines comes from proven safety and efficacy profiles established by continuous efforts to optimize physicochemical properties and endosomal escape. However, despite their transformative impact on the pharmaceutical industry, the clinical use of non-viral nucleic acid delivery is limited to hepatic diseases and vaccines due to liver accumulation. Overcoming liver tropism of nanoparticles is vital to meet clinical needs in other organs. Understanding the anatomical structure and physiological features of various organs would help to identify potential strategies for fine-tuning nanoparticle characteristics. In this Review, we discuss the source of liver tropism of non-viral vectors, present a brief overview of biological structure, processes and barriers in select organs, highlight approaches available to reach non-liver targets, and discuss techniques to accelerate the discovery of non-hepatic therapies.

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.

Incorporation of poly(γ-glutamic acid) in lipid nanoparticles for enhanced mRNA delivery efficiency in vitro and in vivo

Messenger RNA (mRNA)-based therapy shows immense potential for broad biomedical applications. However, the development of safe and efficacious mRNA delivery vectors remains challenging due to delivery barriers and inefficient intracellular payload release. Herein, we presented a simple strategy to boost the mRNA intracellular release by incorporation of anionic poly(γ-glutamic acid) (PGA) into an ionizable lipid-based LNP/mRNA. We systematically investigated the impact of PGA incorporation on mRNA transfection both in vitro and in vivo. The molecular weights and formulation ratios of PGA greatly affected the transfection efficacy of LNP/mRNA. From in vitro study, the optimized LNP/mRNA/PGA was formulated by incorporation of PGA with the molecular weight of 80 kDa or 200 kDa and the charge ratio (N/P/C) of 25/1/1. The optimized formulation achieved around 3-fold mRNA expression in HeLa cells compared to the bare LNP/mRNA. The intracellular releasing study using specific DNA probe revealed that this enhancement of transfection efficacy was attributed to the elevated mRNA release into cytoplasm. Moreover, the optimized LNP/mRNA/PGA achieved up to 5-fold or 3-fold increase of luciferase mRNA expression in vivo after being injected into mice systematically or intramuscularly, respectively. In addition, the incorporation of PGA did not significantly alter the biodistribution profile of the complexes on both organ and cellular levels. Therefore, our work provides a simple strategy to boost mRNA delivery, which holds great promise to improve the efficacy of mRNA therapeutics for various biomedical applications. STATEMENT OF SIGNIFICANCE: The process of designing and screening potent mRNA carriers is complicated and time-consuming, while the efficacy is not always satisfying due to the delivery barriers and inefficient mRNA release. This work presented an alternative strategy to boost the mRNA delivery efficacy by incorporating an anionic natural polymer poly(γ-glutamic acid) (PGA) into LNP/mRNA complexes. The optimized LNP/mRNA/PGA achieved up to 3-fold and 5-fold increase in transfection efficacy in vitro and in vivo, respectively. Intracellular releasing analysis revealed that the enhancement of transfection efficacy was mainly attributed to the elevated intracellular release of mRNA. In addition, the incorporation of PGA did not alter the biodistribution or the biosafety profile of the complexes. These findings indicate that PGA incorporation is a promising strategy to improve the efficacy of mRNA therapeutics.

mRNA vaccine trafficking and resulting protein expression after intramuscular administration

The mRNA vaccine route from injection site to critical immunologic tissues, as well as the localization of protein antigen following intramuscular (i.m.) administration, is crucial to generating an effective immune response. Here, we quantified mRNA at the injection site, lymph nodes, and in select tissues. mRNA was primarily present 24 h after administration and then rapidly degraded from local and systemic tissues. Histological analyses of mRNA and expressed protein at the site of administration and in the lymph nodes following i.m. administration of our vaccine in rodents and nonhuman primates (NHPs) were completed, and mRNA and protein expression were detected in tissue resident and infiltrating immune cells at the injection site. In addition, high levels of protein expression were observed within subcapsular and medullary sinus macrophages in draining lymph nodes. More important, results were similar between rodents and NHPs, indicating cross-species similarities.

Lipid nanoparticle structure and delivery route during pregnancy dictate mRNA potency, immunogenicity, and maternal and fetal outcomes

Treating pregnancy-related disorders is exceptionally challenging because the threat of maternal and/or fetal toxicity discourages the use of existing medications and hinders new drug development. One potential solution is the use of lipid nanoparticle (LNP) RNA therapies, given their proven efficacy, tolerability, and lack of fetal accumulation. Here, we describe LNPs for efficacious mRNA delivery to maternal organs in pregnant mice via several routes of administration. In the placenta, our lead LNP transfected trophoblasts, endothelial cells, and immune cells, with efficacy being structurally dependent on the ionizable lipid polyamine headgroup. Next, we show that LNP-induced maternal inflammatory responses affect mRNA expression in the maternal compartment and hinder neonatal development. Specifically, pro-inflammatory LNP structures and routes of administration curtailed efficacy in maternal lymphoid organs in an IL-1β-dependent manner. Further, immunogenic LNPs provoked the infiltration of adaptive immune cells into the placenta and restricted pup growth after birth. Together, our results provide mechanism-based structural guidance on the design of potent LNPs for safe use during pregnancy.

Circular RNA vaccines with long-term lymph node-targeting delivery stability after lyophilization induce potent and persistent immune responses

IMPORTANCE

messenger RNA (mRNA) vaccines are a key technology in combating existing and emerging infectious diseases. However, the inherent instability of mRNA and the nonspecificity of lipid nanoparticle-encapsulated (LNP) delivery systems result in the need for cold storage and a relatively short-duration immune response to mRNA vaccines. Herein, we develop a novel vaccine in the form of circRNAs encapsulated in LNPs, and the circular structure of the circRNAs enhances their stability. Lyophilization is considered the most effective method for the long-term preservation of RNA vaccines. However, this process may result in irreversible damage to the nanoparticles, particularly the potential disruption of targeting modifications on LNPs. During the selection of lymph node-targeting ligands, we found that LNPs modified with mannose maintained their physical properties almost unchanged after lyophilization. Additionally, the targeting specificity and immunogenicity remained unaffected. In contrast, even with the addition of cryoprotectants such as sucrose, the physical properties of LNPs were impaired, leading to an obvious decrease in immunogenicity. This may be attributed to the protective role of mannose on the surface of LNPs during lyophilization. Freshly prepared and lyophilized mLNP-circRNA vaccines elicited comparable immune responses in both the rabies virus model and the SARS-CoV-2 model. Our data demonstrated that mLNP-circRNA vaccines elicit robust immune responses while improving stability after lyophilization, with no compromise in tissue targeting specificity. Therefore, mannose-modified LNP-circRNA vaccines represent a promising vaccine design strategy.

Breaking the mold with RNA-a "RNAissance" of life science

In the past decade, RNA therapeutics have gone from being a promising concept to one of the most exciting frontiers in healthcare and pharmaceuticals. The field is now entering what many call a renaissance or "RNAissance" which is being fueled by advances in genetic engineering and delivery systems to take on more ambitious development efforts. However, this renaissance is occurring at an unprecedented pace, which will require a different way of thinking if the field is to live up to its full potential. Recognizing this need, this article will provide a forward-looking perspective on the field of RNA medical products and the potential long-term innovations and policy shifts enabled by this revolutionary and game-changing technological platform.

mRNA vaccine designs for optimal adjuvanticity and delivery

Adjuvanticity and delivery are crucial facets of mRNA vaccine design. In modern mRNA vaccines, adjuvant functions are integrated into mRNA vaccine nanoparticles, allowing the co-delivery of antigen mRNA and adjuvants in a unified, all-in-one formulation. In this formulation, many mRNA vaccines utilize the immunostimulating properties of mRNA and vaccine carrier components, including lipids and polymers, as adjuvants. However, careful design is necessary, as excessive adjuvanticity and activation of improper innate immune signalling can conversely hinder vaccination efficacy and trigger adverse effects. mRNA vaccines also require delivery systems to achieve antigen expression in antigen-presenting cells (APCs) within lymphoid organs. Some vaccines directly target APCs in the lymphoid organs, while others rely on APCs migration to the draining lymph nodes after taking up mRNA vaccines. This review explores the current mechanistic understanding of these processes and the ongoing efforts to improve vaccine safety and efficacy based on this understanding.

Tailor made: the art of therapeutic mRNA design

mRNA medicine is a new and rapidly developing field in which the delivery of genetic information in the form of mRNA is used to direct therapeutic protein production in humans. This approach, which allows for the quick and efficient identification and optimization of drug candidates for both large populations and individual patients, has the potential to revolutionize the way we prevent and treat disease. A key feature of mRNA medicines is their high degree of designability, although the design choices involved are complex. Maximizing the production of therapeutic proteins from mRNA medicines requires a thorough understanding of how nucleotide sequence, nucleotide modification and RNA structure interplay to affect translational efficiency and mRNA stability. In this Review, we describe the principles that underlie the physical stability and biological activity of mRNA and emphasize their relevance to the myriad considerations that factor into therapeutic mRNA design.