Lipid Nanoparticle RBD-hFc mRNA Vaccine Protects hACE2 Transgenic Mice against a Lethal SARS-CoV-2 Infection

Emissive Lipid Nanoparticles as Biophotonic Contrast Agent for Site-Selective Solid Tumor Imaging in Pre-Clinical Models

Small organic dye-based fluorescent agents are highly potent in solid tumor imaging but face challenges such as poor photostability, nonspecific distribution, low circulation, and weak tumor binding. Nanocarriers overcome these issues with better physicochemical and biological performance, particularly in cancer imaging. Among the various nanosized carriers, lipid formulations are clinically approved but yet to be designed as bright nanocontrast agents for solid tumor diagnosis without affecting surrounding tissues. Herein, indocyanine green (ICG) encapsulated targetable lipid nanoparticles (698 ICG/LNPs) as safe contrast agents (∼200 nm) have been developed and tested for solid tumor imaging and biodistribution. Our findings reveal that nanoprecipitation produces ICG-LNPs with a unique assembly, which contributes to their high brightness with improved quantum yield (3.5%) in aqueous media. The bright, optically stable (30 days) biophotonic agents demonstrate rapid accumulation (within 1 h) and prolonged retention (for up to 168 h) at the primary tumor site, with better signal intensity following a one-time dose administration (17.7 × 109 LNP per dose). Incorporated folic acid (735 folic acid/LNPs) helps in selective tumor binding and the specific biodistribution of intravenously injected nanoparticles without affecting healthy tissues. Designed targetable ICG-LNP (634 MESF) demonstrates high-contrast fluorescence and resolution from the tumor area as compared to the targetable ICG-liposomal nanoparticles (532 MESF). Various in vitro and in vivo findings reveal that the cancer diagnostic efficacy elicited by designed bright lipid nanoparticles are comparable to reported clinically accepted imaging agents. Thus, such LNPs hold translational potential for cancer diagnosis at an early stage.

Oligonucleotide-Linked Lipid Nanoparticles as a Versatile mRNA Nanovaccine Platform

An effective delivery platform is crucial for the development of mRNA vaccines and therapeutics. Here, a versatile platform utilizing cholesterol-modified oligonucleotides (L-oligo) that bind to the mRNA within lipid nanoparticles (LNP), and enables the effective delivery of the mRNA into target cells is introduced. mRNA incorporated into LNPs via linkage with L-oligo, termed oligonucleotide-linked LNP (lnLNP), is superior in cellular uptake and transfection efficiency in target cells in vitro and in vivo, compared to the conventional LNP formulations. It is further applied lnLNP as an mRNA vaccine platform for SARS-CoV-2, demonstrating robust induction of neutralizing activity as well as polyfunctional SARS-CoV-2-specific T-cell response in vivo. The current strategy can be versatilely applied to different LNP platforms, for vaccine and therapeutic applications against various diseases, such as infections and cancers.

Inhalable hybrid nanovaccines with virus-biomimetic structure boost protective immune responses against SARS-CoV-2 variants

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with different antigenic variants, has posed a significant threat to public health. It is urgent to develop inhalable vaccines, instead of injectable vaccines, to elicit mucosal immunity against respiratory viral infections.

METHODS

We reported an inhalable hybrid nanovaccine (NVRBD-MLipo) to boost protective immunity against SARS-CoV-2 infection. Nanovesicles derived from genetically engineered 293T cells expressing RBD (NVRBD) were fused with pulmonary surfactant (PS)-biomimetic liposomes containing MPLA (MLipo) to yield NVRBD-MLipo, which possessed virus-biomimetic structure, inherited RBD expression and versatile properties.

RESULTS

In contrast to subcutaneous vaccination, NVRBD-MLipo, via inhalable vaccination, could efficiently enter the alveolar macrophages (AMs) to elicit AMs activation through MPLA-activated TLR4/NF-κB signaling pathway. Moreover, NVRBD-MLipo induced T and B cells activation, and high level of RBD-specific IgG and secretory IgA (sIgA), thus elevating protective mucosal and systemic immune responses, while reducing side effects. NVRBD-MLipo also demonstrated broad-spectrum neutralization activity against SARS-CoV-2 (WT, Delta, Omicron) pseudovirus, and protected immunized mice against WT pseudovirus infection.

CONCLUSIONS

This inhalable NVRBD-MLipo, as an effective and safe nanovaccine, holds huge potential to provoke robust mucosal immunity, and might be a promising vaccine candidate to combat respiratory infectious diseases, including COVID-19 and influenza.

Delivery of mRNA Vaccine with 1, 2-Diesters-Derived Lipids Elicits Fast Liver Clearance for Safe and Effective Cancer Immunotherapy

Messenger RNA (mRNA) vaccine is explored as a promising strategy for cancer immunotherapy, but the side effects, especially the liver-related damage caused by LNP, raise concerns about its safety. In this study, a novel library of 248 ionizable lipids comprising 1,2-diesters is designed via a two-step process involving the epoxide ring-opening reaction with carboxyl group-containing alkyl chains followed by an esterification reaction with the tertiary amines. Owing to the special chemical structure of 1,2-diesters, the top-performing lipids and formulations exhibit a faster clearance rate in the liver, contributing to increased stability and higher safety compared with DLin-MC3-DMA. Moreover, the LNP shows superior intramuscular mRNA delivery and elicits robust antigen-specific immune activation. The vaccinations delivered by the LNP system suppress tumor growth and prolong survival in both model human papillomavirus E7 and ovalbumin antigen-expressing tumor models. Finally, the structure of lipids which enhances the protein expression in the spleen and draining lymph nodes compared with ALC-0315 lipid in Comirnaty is further optimized. In conclusion, the 1, 2-diester-derived lipids exhibit rapid liver clearance and effective anticancer efficiency to different types of antigens-expressing tumor models, which may be a safe and universal platform for mRNA vaccines.

The advances of adjuvants in mRNA vaccines

The remarkable success of messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has propelled the rapid development of this vaccination technology in recent years. Over the last three decades, numerous studies have shown the considerable potential of mRNA vaccines that elicit protective immune responses against pathogens or cancers in preclinical studies or clinical trials. These effective mRNA vaccines usually contain specific adjuvants to obtain the desired immune effect. Vaccine adjuvants traditionally are immunopotentiators that bind to pattern recognition receptors (PRRs) of innate immune cells to increase the magnitude or achieve qualitative alteration of immune responses, finally enhancing the efficacy of vaccines. Generally, adjuvants are necessary parts of competent vaccines. According to the existing literature, adjuvants in mRNA vaccines can be broadly classified into three categories: 1) RNA with self-adjuvant characteristics, 2) components of the delivery system, and 3) exogenous immunostimulants. This review summarizes the three types of adjuvants used in mRNA vaccines and provides a comprehensive understanding of molecular mechanisms by which adjuvants exert their functions in mRNA vaccines.

The Dual Role of the Innate Immune System in the Effectiveness of mRNA Therapeutics

Advances in molecular biology have revolutionized the use of messenger RNA (mRNA) as a therapeutic. The concept of nucleic acid therapy with mRNA originated in 1990 when Wolff et al. reported successful expression of proteins in target organs by direct injection of either plasmid DNA or mRNA. It took decades to bring the transfection efficiency of mRNA closer to that of DNA. The next few decades were dedicated to turning in vitro-transcribed (IVT) mRNA from a promising delivery tool for gene therapy into a full-blown therapeutic modality, which changed the biotech market rapidly. Hundreds of clinical trials are currently underway using mRNA for prophylaxis and therapy of infectious diseases and cancers, in regenerative medicine, and genome editing. The potential of IVT mRNA to induce an innate immune response favors its use for vaccination and immunotherapy. Nonetheless, in non-immunotherapy applications, the intrinsic immunostimulatory activity of mRNA directly hinders the desired therapeutic effect since it can seriously impair the target protein expression. Targeting the same innate immune factors can increase the effectiveness of mRNA therapeutics for some indications and decrease it for others, and vice versa. The review aims to present the innate immunity-related 'barriers' or 'springboards' that may affect the development of immunotherapies and non-immunotherapy applications of mRNA medicines.

A single-dose F1-based mRNA-LNP vaccine provides protection against the lethal plague bacterium

Messenger RNA (mRNA) lipid nanoparticle (LNP) vaccines have emerged as an effective vaccination strategy. Although currently applied toward viral pathogens, data concerning the platform's effectiveness against bacterial pathogens are limited. Here, we developed an effective mRNA-LNP vaccine against a lethal bacterial pathogen by optimizing mRNA payload guanine and cytosine content and antigen design. We designed a nucleoside-modified mRNA-LNP vaccine based on the bacterial F1 capsule antigen, a major protective component of Yersinia pestis, the etiological agent of plague. Plague is a rapidly deteriorating contagious disease that has killed millions of people during the history of humankind. Now, the disease is treated effectively with antibiotics; however, in the case of a multiple-antibiotic-resistant strain outbreak, alternative countermeasures are required. Our mRNA-LNP vaccine elicited humoral and cellular immunological responses in C57BL/6 mice and conferred rapid, full protection against lethal Y. pestis infection after a single dose. These data open avenues for urgently needed effective antibacterial vaccines.

A PEG-lipid-free COVID-19 mRNA vaccine triggers robust immune responses in mice

COVID-19 mRNA vaccines represent a completely new category of vaccines and play a crucial role in controlling the COVID-19 pandemic. In this study, we have developed a PEG-lipid-free two-component mRNA vaccine (PFTCmvac) by formulating mRNA encoding the receptor binding domain (RBD) of SARS-CoV-2 into lipid-like nanoassemblies. Without using polyethylene glycol (PEG)-lipids, the self-assembled PFTCmvac forms thermostable nanoassemblies and exhibits a dose-dependent cellular uptake and membrane disruption, eventually leading to high-level protein expression in both mammalian cells and mice. Vaccination with PFTCmvac elicits strong humoral and cellular responses in mice, without evidence of significant adverse reactions. In addition, the vaccine platform does not trigger complement activation in human serum, even at a high serum concentration. Collectively, the PEG-lipid-free two-component nanoassemblies provide an alternative delivery technology for COVID-19 mRNA vaccines and opportunities for the rapid production of new mRNA vaccines against emerging infectious diseases.

Nanotechnology-based strategies against SARS-CoV-2 variants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has already infected more than 500 million people globally (as of May 2022), creating the coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology has played a pivotal role in the fight against SARS-CoV-2 in various aspects, with the successful development of the two highly effective nanotechnology-based messenger RNA vaccines being the most profound. Despite the remarkable efficacy of mRNA vaccines against the original SARS-CoV-2 strain, hopes for quickly ending this pandemic have been dampened by the emerging SARS-CoV-2 variants, which have brought several new pandemic waves. Thus, novel strategies should be proposed to tackle the crisis presented by existing and emerging SARS-CoV-2 variants. Here, we discuss the SARS-CoV-2 variants from biological and immunological perspectives, and the rational design and development of novel and potential nanotechnology-based strategies to combat existing and possible future SARS-CoV-2 variants. The lessons learnt and design strategies developed from this battle against SARS-CoV-2 variants could also inspire innovation in the development of nanotechnology-based strategies for tackling other global infectious diseases and their future variants.

Development of transgenic models susceptible and resistant to SARS-CoV-2 infection in FVB background mice

Coronavirus disease (COVID-19), caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is currently spreading globally. To overcome the COVID-19 pandemic, preclinical evaluations of vaccines and therapeutics using K18-hACE2 and CAG-hACE2 transgenic mice are ongoing. However, a comparative study on SARS-CoV-2 infection between K18-hACE2 and CAG-hACE2 mice has not been published. In this study, we compared the susceptibility and resistance to SARS-CoV-2 infection between two strains of transgenic mice, which were generated in FVB background mice. K18-hACE2 mice exhibited severe weight loss with definitive lethality, but CAG-hACE2 mice survived; and differences were observed in the lung, spleen, cerebrum, cerebellum, and small intestine. A higher viral titer was detected in the lungs, cerebrums, and cerebellums of K18-hACE2 mice than in the lungs of CAG-hACE2 mice. Severe pneumonia was observed in histopathological findings in K18-hACE2, and mild pneumonia was observed in CAG-hACE2. Atrophy of the splenic white pulp and reduction of spleen weight was observed, and hyperplasia of goblet cells with villi atrophy of the small intestine was observed in K18-hACE2 mice compared to CAG-hACE2 mice. These results indicate that K18-hACE2 mice are relatively susceptible to SARS-CoV-2 and that CAG-hACE2 mice are resistant to SARS-CoV-2. Based on these lineage-specific sensitivities, we suggest that K18-hACE2 mouse is suitable for highly susceptible model of SARS-CoV-2, and CAG-hACE2 mouse is suitable for mild susceptible model of SARS-CoV-2 infection.

Matrix Metalloproteinases Expression Is Associated with SARS-CoV-2-Induced Lung Pathology and Extracellular-Matrix Remodeling in K18-hACE2 Mice

The COVID-19 pandemic caused by the SARS-CoV-2 infection induced lung inflammation characterized by cytokine storm and fulminant immune response of both resident and migrated immune cells, accelerating alveolar damage. In this work we identified members of the matrix metalloprotease (MMPs) family associated with lung extra-cellular matrix (ECM) destruction using K18-hACE2-transgenic mice (K18-hACE2) infected intranasally with SARS-CoV-2. Five days post infection, the lungs exhibited overall alveolar damage of epithelial cells and massive leukocytes infiltration. A substantial pulmonary increase in MMP8, MMP9, and MMP14 in the lungs post SARS-CoV-2 infection was associated with degradation of ECM components including collagen, laminin, and proteoglycans. The process of tissue damage and ECM degradation during SARS-CoV-2 lung infection is suggested to be associated with activity of members of the MMPs family, which in turn may be used as a therapeutic intervention.

Comparison of Immune Responses Elicited by SARS-CoV-2 mRNA and Recombinant Protein Vaccine Candidates

After the outbreak of COVID-19, billions of vaccines with different types have been administrated, including recombinant protein vaccines and mRNA vaccines. Although both types of SARS-CoV-2 vaccine can protect people from viral infection, their differences in humoral and cellular immune responses are still not clearly understood. In this study, we made a head-to-head comparison between an mRNA vaccine candidate and a recombinant protein vaccine we developed previously. Results demonstrated that both vaccine candidates could elicit high specific binding and neutralizing antibody titers in BALB/c mice, but with bias towards different IgG subtypes. Besides, the mRNA vaccine candidate induces higher cellular immune responses than the recombinant protein vaccine. To date, this is the first reported study to directly compare the immune responses of both arms between SARS-CoV-2 mRNA and recombinant vaccines.

Nanotechnology-enabled immunoengineering approaches to advance therapeutic applications

Immunotherapy has reached clinical success in the last decade, with the emergence of new and effective treatments such as checkpoint blockade therapy and CAR T-cell therapy that have drastically improved patient outcomes. Still, these therapies can be improved to limit off-target effects, mitigate systemic toxicities, and increase overall efficacies. Nanoscale engineering offers strategies that enable researchers to attain these goals through the manipulation of immune cell functions, such as enhancing immunity against cancers and pathogens, controlling the site of immune response, and promoting tolerance via the delivery of small molecule drugs or biologics. By tuning the properties of the nanomaterials, such as size, shape, charge, and surface chemistry, different types of immune cells can be targeted and engineered, such as dendritic cells for immunization, or T cells for promoting adaptive immunity. Researchers have come to better understand the critical role the immune system plays in the progression of pathologies besides cancer, and developing nanoengineering approaches that seek to harness the potential of immune cell activities can lead to favorable outcomes for the treatment of injuries and diseases.

Advances in mRNA and other vaccines against MERS-CoV

Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human coronavirus (CoV). Belonging to the same beta-CoV genus as severe acute respiratory syndrome coronavirus-1 (SARS-CoV-1) and SARS-CoV-2, MERS-CoV has a significantly higher fatality rate with limited human-to-human transmissibility. MERS-CoV causes sporadic outbreaks, but no vaccines have yet been approved for use in humans, thus calling for continued efforts to develop effective vaccines against this important CoV. Similar to SARS-CoV-1 and SARS-CoV-2, MERS-CoV contains 4 structural proteins, among which the surface spike (S) protein has been used as a core component in the majority of currently developed MERS-CoV vaccines. Here, we illustrate the importance of the MERS-CoV S protein as a key vaccine target and provide an update on the currently developed MERS-CoV vaccines, including those based on DNAs, proteins, virus-like particles or nanoparticles, and viral vectors. Additionally, we describe approaches for designing MERS-CoV mRNA vaccines and explore the role and importance of naturally occurring pseudo-nucleosides in the design of effective MERS-CoV mRNA vaccines. This review also provides useful insights into designing and evaluating mRNA vaccines against other viral pathogens.

Recent advances in nanotechnology-based COVID-19 vaccines and therapeutic antibodies

COVID-19 has caused a global pandemic and millions of deaths. It is imperative to develop effective countermeasures against the causative viral agent, SARS-CoV-2 and its many variants. Vaccines and therapeutic antibodies are the most effective approaches for preventing and treating COVID-19, respectively. SARS-CoV-2 enters host cells through the activities of the virus-surface spike (S) protein. Accordingly, the S protein is a prime target for vaccines and therapeutic antibodies. Dealing with particles with dimensions on the scale of nanometers, nanotechnology has emerged as a critical tool for rapidly designing and developing safe, effective, and urgently needed vaccines and therapeutics to control the COVID-19 pandemic. For example, nanotechnology was key to the fast-track approval of two mRNA vaccines for their wide use in human populations. In this review article, we first explore the roles of nanotechnology in battling COVID-19, including protein nanoparticles (for presentation of protein vaccines), lipid nanoparticles (for formulation with mRNAs), and nanobodies (as unique therapeutic antibodies). We then summarize the currently available COVID-19 vaccines and therapeutics based on nanotechnology.

Binding between an amine cationic surfactant and DNA and surface properties of the resultant aggregates

Binding between cetyltrimethylammonium bromide, a cationic surfactant, and a variety of lengths of single stranded DNA was measured using fluorescence polarization and a simple cooperative model was used to obtain dissociation constants on the order of 1 × 10^-5 for the aggregates that formed. Aggregation depended on strand length where strands much shorter than 40 nucleotides (for example strands of 24-nucleotides) were too short to form the same size aggregates. Other factors such as salt concentration and temperature also affected aggregate formation: increasing either the salt concentration or performing binding at the highest temperature studied (60 °C) made it more difficult for aggregates to form. Both heating and dilution of aggregates caused the anisotropy signal to decrease, which suggested that the complexes fell apart under these conditions. Force spectroscopy of aggregate surfaces showed that both electrostatic and hydrophobic adhesive forces were present between aggregates and derivatized AFM tips. These findings can be used to better understand the stability of cationic surfactant-DNA aggregates and may provide guidance for lipid nanoparticle design used in vaccine development and therapeutics.

Animal models for SARS-CoV-2 infection and pathology

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiology of coronavirus disease 2019 (COVID-19) pandemic. Current variants including Alpha, Beta, Gamma, Delta, and Lambda increase the capacity of infection and transmission of SARS-CoV-2, which might disable the in-used therapies and vaccines. The COVID-19 has now put an enormous strain on health care system all over the world. Therefore, the development of animal models that can capture characteristics and immune responses observed in COVID-19 patients is urgently needed. Appropriate models could accelerate the testing of therapeutic drugs and vaccines against SARS-CoV-2. In this review, we aim to summarize the current animal models for SARS-CoV-2 infection, including mice, hamsters, nonhuman primates, and ferrets, and discuss the details of transmission, pathology, and immunology induced by SARS-CoV-2 in these animal models. We hope this could throw light to the increased usefulness in fundamental studies of COVID-19 and the preclinical analysis of vaccines and therapeutic agents.

Lipid-Based Nanoparticles for Delivery of Vaccine Adjuvants and Antigens: Toward Multicomponent Vaccines

Despite the many advances that have occurred in the field of vaccine adjuvants, there are still unmet needs that may enable the development of vaccines suitable for more challenging pathogens (e.g., HIV and tuberculosis) and for cancer vaccines. Liposomes have already been shown to be highly effective as adjuvant/delivery systems due to their versatility and likely will find further uses in this space. The broad potential of lipid-based delivery systems is highlighted by the recent approval of COVID-19 vaccines comprising lipid nanoparticles with encapsulated mRNA. This review provides an overview of the different approaches that can be evaluated for the design of lipid-based vaccine adjuvant/delivery systems for protein, carbohydrate, and nucleic acid-based antigens and how these strategies might be combined to develop multicomponent vaccines.