Eliciting B cell immunity against infectious diseases using nanovaccines

Self-Assembling protein nanoparticle platform for multivalent antigen delivery in vaccine development

Nanoparticle vaccines can efficiently and repeatedly display multivalent antigens, thereby improving the targeted delivery of antigens and inducing more durable immune responses, making them an important representative of novel vaccines. The global COVID-19 pandemic has accelerated the development of nanoparticle vaccines, offering a promising solution for the prevention and control of infectious diseases. Currently, the development of nanoparticle vaccines involves the use of various types of nanoparticles, including liposomes, polymers, inorganic materials, and emulsions. Protein nanoparticles candidate vaccines are attracting increasing attention because of their unique antigen presentation methods and self-assembly characteristics during their development, leading to a broad consensus on their promising future. Naturally self-assembling protein nanoparticles, such as ferritin, enhance antigen presentation, which aids in the activation of both humoral and cellular immune responses. This has led to significant advancements in the study of hepatitis B virus. Meanwhile, some synthetically engineered protein nanoparticles, such as mi3, and I53-50, can induce higher antibody titers through chemical conjugation with the SpyTag-SpyCatcher system, thereby providing better immunoprotection and showing promising prospects in the prevention of H1N1 and H3N2 influenza virus infections. This article reviews the unique advantages of protein nanoparticles as antigen delivery platforms, progress made in immunological design mechanisms, advances in the application of related adjuvants in preclinical and clinical trials, and the performance of commonly used computationally designed protein nanoparticles in preclinical trials, with a particular emphasis on the progress in the application of cationic nanoparticle vaccines. The aim is to provide future researchers with effective adjuvant strategies and high-quality selections for computationally designed protein nanoparticles, thereby promoting the clinical trial process of protein nanoparticles vaccines.

A Self-Assembled Nanovaccine with BA.4/5 Receptor-Binding Domain and CpG Oligodeoxynucleotides Induces Broad-Spectrum Neutralization against SARS-CoV-2 Omicron Subvariants

Over the past 3 years, SARS-CoV-2 Omicron has been circulating globally with the emergence of multiple subvariants, including BA.5, BA.5.2, XBB, XBB.1, EG.5.1, HK.3, BA.2.86, JN.1, and KP.2. To combat these Omicron subvariants, several vaccines based on receptor-binding domain (RBD) dimers have been developed; however, RBD dimer vaccines require frequent updates to cope with the emergence of new variants. In contrast, the development of a safe, effective, and broad-spectrum vaccine against multiple Omicron subvariants, including the latest JN.1 and KP.2, would be a one-size-fits-all solution. Here, we designed BA.4/5 RBD-PC7A conjugate micelles by displaying the BA.4/5 RBD in PC7A micelles. Remarkably, the micelles elicited potent neutralizing antibodies (NAbs) in rabbits, effectively neutralizing BA.5.2, XBB.1.18, and HK.3 infections. Moreover, the micelles alone were able to induce NAbs in mice against the BA.5 variant. When a cytosine-phosphate-guanine (CpG) adjuvant was added and electrostatically adsorbed to the micelles, there was a significant increase in the antibody titers of IgG1, IgG2b, and IgG2c. This enhancement facilitated the broad neutralization of various strains, including BA.5.2, XBB.1.18, HK.3, JN.1, and KP.2. Furthermore, the micelles adsorbed with CpG protected golden hamsters from infection with the BA.5.2 strain. This study presents a potent and broadly neutralizing nanovaccine that includes the BA.4/5 RBD antigen and a CpG adjuvant. It demonstrates efficacy against multiple Omicron subvariants, including BA.5, BA.5.2, XBB.1.18, HK.3, JN.1, and KP.2, highlighting its potential for clinical translation.

Immunogenicity assessment of a swine fever-swine circovirus type 2 duplex vaccine candidate created using the Zera nanoparticle delivery method

Classical swine fever virus (CSFV) and porcine circovirus (PCV) are the primary pathogens of swine fever and pig circovirus infections, respectively. Co-infections with these diseases result in severe economic losses for the swine sector. To prevent and control the disease, immunization is the primary technique for reducing co-infections and economic losses. In this work, we created a new nanoparticle vaccine using a Zera nanoparticle delivery system that expressed swine fever virus E0 and E2 proteins as well as porcine circovirus Cap proteins. We then inoculated BALB/c mice to test the vaccine's immunogenicity. The findings revealed that this nanoparticle vaccine could stimulate the mouse organism to produce high levels of humoral and cellular immunity, making it a promising candidate for the development of subunit vaccines against swine fever and swine circulatory-associated diseases. This study also provides ideas for other disease vaccines.

Hybrid Outer Membrane Vesicles with Genetically Engineering for Treatment of Implant-Associated Infections and Relapse Prevention Through Host Immunomodulation

Implant-associated infections (IAIs) are refractory to elimination, and the local immunosuppressive microenvironment (IME) exacerbates therapeutic difficulties, ultimately causing persistence and relapse. Therefore, exploring immunostrengthening treatments holds great promise for reversing IME and thoroughly eradicating chronic or repetitive infections. Bacterial outer membrane vesicles (OMVs) have emerged as potential immunostimulatory candidates; however, they lack active targeting capabilities and cause non-specific inflammatory side effects. In this study, bone marrow-derived mesenchymal stem cells (BMSCs) are genetically engineered to overexpress CXCR4 and isolated cell membranes (mBMSCCXCR4) for hybridization with OMVs derived from Escherichia coli (E. coli) to produce nanovesicles (mBMSCCXCR4@OMV). The resulting mBMSCCXCR4@OMV nanovesicles demonstrate excellent bone marrow targeting capability and are effectively taken up by bone marrow-derived macrophages, triggering the efficient transition to pro-inflammatory M1 status through TLR/NF-κB pathway. This alteration promotes innate bactericidal capacity and antigen presentation. Subsequent activation of T and B cells and inhibition of myeloid-derived suppressor cells (MDSCs) facilitated in vivo adaptive immunity in mouse models. Additionally, mBMSCCXCR4@OMV boosted memory B cell and bacteria-specific antibody responses. Together, these data highlight the potential of mBMSCCXCR4@OMV to eradicate complicated IAIs and provide whole-stage protection against postsurgical relapse, thus marking a significant immunotherapeutic advancement in the post-antibiotic era.

Leveraging core proteome data of Kingella kingae for multi-epitope vaccine design against TonB dependent receptor (TDR): an in silico approach

Kingella kingae is a Gram-negative bacterium that causes invasive infections in children and older or immunocompromised individuals, making it a significant public health concern. In this study, a pan-proteomic mediated vaccine target mining was attempted to identify potential vaccine targets in K. kingae. Currently, there is no vaccine available against this pathobiont. Therefore, we designed and validated an in silico vaccine construct by targeting the lactoferrin/transferrin-binding TonB-dependent receptor. Antigenic regions of the TonB receptor were mapped, and the predicted epitopes were anticipated to be effective in a broad range of the world population. Using their combinations with linkers and various adjuvants, 12 vaccine constructs were prepared. The best construct (C7) with no allergenicity and high antigenicity was subjected to molecular modeling, docking with important immune receptors of humans, and then molecular dynamics (MD) simulation. After binding validation and stability assessment, it was cloned into a pet-28a + plasmid vector. Immune response was also simulated, and the vaccine was observed to invoke B- and T-cell induction. These findings can help accelerate the development of a new vaccine against K. kingae or other pathogens targeting the homolog of TonB. Nevertheless, we propose additional testing of C7 construct for efficacy and safety in vitro and in vivo.

Exploring the immuno-nano nexus: A paradigm shift in tumor vaccines

Tumor vaccines have become a crucial strategy in cancer immunotherapy. Challenges of traditional tumor vaccines include inadequate immune activation and low efficacy of antigen delivery. Nanoparticles, with their tunable properties and versatile functionalities, have redefined the landscape of tumor vaccine design. In this review, we outline the multifaceted roles of nanoparticles in tumor vaccines, ranging from their capacity as delivery vehicles to their function as immunomodulatory adjuvants capable of stimulating anti-tumor immunity. We discuss how this innovative approach significantly boosts antigen presentation by leveraging tailored nanoparticles that facilitate efficient uptake by antigen-presenting cells. These nanoparticles have been meticulously designed to overcome biological barriers, ensuring optimal delivery to lymph nodes and effective interaction with the immune system. Overall, this review highlights the transformative power of nanotechnology in redefining the principles of tumor vaccines. The intent is to inform more efficacious and precise cancer immunotherapies. The integration of these advanced nanotechnological strategies should unlock new frontiers in tumor vaccine development, enhancing their potential to elicit robust and durable anti-tumor immunity.

DNA origami vaccines program antigen-focused germinal centers

Recruitment and expansion of rare precursor B cells in germinal centers (GCs) is a central goal of vaccination to generate broadly neutralizing antibodies (bnAbs) against challenging pathogens such as HIV. Multivalent immunogen display is a well-established method to enhance vaccine-induced B cell responses, typically accomplished by using natural or engineered protein scaffolds. However, these scaffolds themselves are targets of antibody responses, with the potential to generate competitor scaffold-specific B cells that could theoretically limit expansion and maturation of "on-target" B cells in the GC response. Here, we rationally designed T-independent, DNA-origami based virus-like particles (VLPs) with optimal antigenic display of the germline targeting HIV Env immunogen, eOD-GT8, and appropriate T cell help to achieve a potent GC response. In preclinical mouse models, these DNA-VLPs expanded significantly higher frequencies of epitope-specific GC B cells compared with a state-of-the-art clinical protein nanoparticle. Optimized DNA-VLPs primed germinal centers focused on the target antigen and rapidly expanded subdominant broadly neutralizing antibody precursor B cells for HIV with a single immunization. Thus, avoiding scaffold-specific responses augments priming of bnAb precursor B cells, and DNA-VLPs are a promising platform for promoting B cell responses towards challenging subdominant epitopes.

An in vitro nanocarrier-based B cell antigen loading system; tumor growth suppression via transfusion of the antigen-loaded B cells in vivo

B cell-based vaccines are expected to provide an alternative to DC-based vaccines. However, the efficacy of antigen uptake by B cells in vitro is relatively low, and efficient antigen-loading methods must be established before B cell-based vaccines are viable in clinical settings. We recently developed an in vitro system that efficiently loads antigens into isolated splenic B cells via liposomes decorated with hydroxyl PEG (HO-PEG-Lips). Therefore, the purpose of this study was to expand this system in order to achieve another approach to in vivo tumor growth suppression. By using HO-PEG-Lips as a carrier for model antigen OVA along with an adjuvant, α-galactosylceramide (GC), the amount of antigen loading to the B cells in vitro was increased compared with that of both free OVA and free GC. Transfusion of B cells treated with HO-PEG-Lips that encapsulated OVA and GC suppressed the growth of OVA-expressing murine thymoma (E.G7-OVA) tumors in vivo through strong induction of OVA-specific T cells. Under fluorescence microscopic observation, migration of the transfused B cells in the spleens of recipient mice were confirmed. Our results indicate that our novel antigen-loading system could become a promising approach to facilitate the development of cell-based therapeutic cancer vaccines utilizing B cells as alternative APCs.

Human immune organoids to decode B cell response in healthy donors and patients with lymphoma

Antibodies are produced when naive B cells differentiate into plasma cells within germinal centres (GCs) of lymphoid tissues. Patients with B cell lymphoma on effective immunotherapies exhibit diminished antibody production, leading to higher infection rates and reduced vaccine efficacy, even after B cell recovery. Current ex vivo models fail to sustain long-term GC reactions and effectively test B cell responses. Here we developed synthetic hydrogels mimicking the lymphoid tissue microenvironment, enabling human GCs from tonsils and peripheral blood mononuclear cell-derived B cells. Immune organoids derived from peripheral blood mononuclear cells maintain GC B cells and plasma cells longer than tonsil-derived ones and exhibit unique B cell programming, including GC compartments, somatic hypermutation, immunoglobulin class switching and B cell clones. Chemical inhibition of transcriptional and epigenetic processes enhances plasma cell formation. While integrating polarized CXCL12 protein in a lymphoid organ-on-chip modulates GC responses in healthy donor B cells, it fails with B cells derived from patients with lymphoma. Our system allows rapid, controlled modelling of immune responses and B cell disorders.

Programmable Macrophage Vesicle Based Bionic Self-Adjuvanting Vaccine for Immunization against Monkeypox Virus

The emergence of monkeypox has become a global health threat after the COVID-19 pandemic. Due to the lack of available specifically treatment against MPV, developing an available vaccine is thus the most prospective and urgent strategy. Herein, a programmable macrophage vesicle based bionic self-adjuvanting vaccine (AM@AEvs-PB) is first developed for defending against monkeypox virus (MPV). Based on MPV-related antigen-stimulated macrophage-derived vesicles, the nanovaccine is constructed by loading the mature virion (MV)-related intracellular protein (A29L/M1R) and simultaneously modifying with the enveloped virion (EV) antigen (B6R), enabling them to effectively promote antigen presentation and enhance adaptive immune through self-adjuvant strategy. Owing to the synergistic properties of bionic vaccine coloaded MV and EV protein in defensing MPV, the activation ratio of antigen-presenting cells is nearly four times than that of single antigen in the same dose, resulting in stronger immunity in host. Notably, intramuscular injection uptake of AM@AEvs-PB demonstrated vigorous immune-protective effects in the mouse challenge attempt, offering a promising strategy for pre-clinical monkeypox vaccine development.

Advanced technologies for the development of infectious disease vaccines

Vaccines play a critical role in the prevention of life-threatening infectious disease. However, the development of effective vaccines against many immune-evading pathogens such as HIV has proven challenging, and existing vaccines against some diseases such as tuberculosis and malaria have limited efficacy. The historically slow rate of vaccine development and limited pan-variant immune responses also limit existing vaccine utility against rapidly emerging and mutating pathogens such as influenza and SARS-CoV-2. Additionally, reactogenic effects can contribute to vaccine hesitancy, further undermining the ability of vaccination campaigns to generate herd immunity. These limitations are fuelling the development of novel vaccine technologies to more effectively combat infectious diseases. Towards this end, advances in vaccine delivery systems, adjuvants, antigens and other technologies are paving the way for the next generation of vaccines. This Review focuses on recent advances in synthetic vaccine systems and their associated challenges, highlighting innovation in the field of nano- and nucleic acid-based vaccines.

Drug-Free "Triboelectric Immunotherapy" Activating Immunity for Osteomyelitis Treatment and Recurrence Prevention

Treatment of osteomyelitis is clinically challenging with low therapeutic efficacy and high risk of recurrence owing to the immunosuppressive microenvironment. Existing therapies are limited by drug concentration and single regulatory effect on the immune network, and emphasize the role of anti-inflammatory effects in reducing osteoclast rather than the role of proinflammatory effects in accelerating infection clearance, which is not conducive to complete bacteria elimination and recurrence prevention. Herein, a direct-current triboelectric nanogenerator (DC-TENG) is established to perform antibacterial effects and modulate immunological properties of infectious microenvironments of osteomyelitis through electrical stimulation, namely triboelectric immunotherapy. Seeing from the results, the triboelectric immunotherapy successfully activates polarization to proinflammatory (M1) macrophages in vitro, accompanied by satisfying direct antibacterial effects. The antibacterial and osteogenic abilities of triboelectric immunotherapy are verified in rat cranial osteomyelitis models. The effects on the polarization and differentiation of immune-related cells in vivo are investigated by establishing in situ tibial osteomyelitis models and immunosurveillance models in C57 mice respectively, indicating the ability of activating immunity and producing immunological memory for in situ infection and secondary recurrence, thus accelerating healing and preventing relapse. This study provides an efficient, long-acting, multifunctional, and wearable triboelectric immunotherapy strategy for drug-free osteomyelitis treatment systems.

Amine headgroups in ionizable lipids drive immune responses to lipid nanoparticles by binding to the receptors TLR4 and CD1d

Lipid nanoparticles (LNPs) are the most clinically advanced delivery vehicle for RNA therapeutics, partly because of established lipid structure-activity relationships focused on formulation potency. Yet such knowledge has not extended to LNP immunogenicity. Here we show that the innate and adaptive immune responses elicited by LNPs are linked to their ionizable lipid chemistry. Specifically, we show that the amine headgroups in ionizable lipids drive LNP immunogenicity by binding to Toll-like receptor 4 and CD1d and by promoting lipid-raft formation. Immunogenic LNPs favour a type-1 T-helper-cell-biased immune response marked by increases in the immunoglobulins IgG2c and IgG1 and in the pro-inflammatory cytokines tumour necrosis factor, interferon γ and the interleukins IL-6 and IL-2. Notably, the inflammatory signals originating from these receptors inhibit the production of anti-poly(ethylene glycol) IgM antibodies, preventing the often-observed loss of efficacy in the LNP-mediated delivery of siRNA and mRNA. Moreover, we identified computational methods for the prediction of the structure-dependent innate and adaptive responses of LNPs. Our findings may help accelerate the discovery of well-tolerated ionizable lipids suitable for repeated dosing.

Emerging Cationic Nanovaccines

Cationic vaccines of nanometric sizes can directly perform the delivery of antigen(s) and immunomodulator(s) to dendritic cells in the lymph nodes. The positively charged nanovaccines are taken up by antigen-presenting cells (APCs) of the lymphatic system often originating the cellular immunological defense required to fight intracellular microbial infections and the proliferation of cancers. Cationic molecules imparting the positive charges to nanovaccines exhibit a dose-dependent toxicity which needs to be systematically addressed. Against the coronavirus, mRNA cationic nanovaccines evolved rapidly. Nowadays cationic nanovaccines have been formulated against several infections with the advantage of cationic compounds granting protection of nucleic acids in vivo against biodegradation by nucleases. Up to the threshold concentration of cationic molecules for nanovaccine delivery, cationic nanovaccines perform well eliciting the desired Th 1 improved immune response in the absence of cytotoxicity. A second strategy in the literature involves dilution of cationic components in biocompatible polymeric matrixes. Polymeric nanoparticles incorporating cationic molecules at reduced concentrations for the cationic component often result in an absence of toxic effects. The progress in vaccinology against cancer involves in situ designs for cationic nanovaccines. The lysis of transformed cancer cells releases several tumoral antigens, which in the presence of cationic nanoadjuvants can be systemically presented for the prevention of metastatic cancer. In addition, these local cationic nanovaccines allow immunotherapeutic tumor treatment.

Bioresponsive Immunotherapeutic Materials

The human immune system is an interaction network of biological processes, and its dysfunction is closely associated with a wide array of diseases, such as cancer, infectious diseases, tissue damage, and autoimmune diseases. Manipulation of the immune response network in a desired and controlled fashion has been regarded as a promising strategy for maximizing immunotherapeutic efficacy and minimizing side effects. Integration of "smart" bioresponsive materials with immunoactive agents including small molecules, biomacromolecules, and cells can achieve on-demand release of agents at targeted sites to reduce overdose-related toxicity and alleviate off-target effects. This review highlights the design principles of bioresponsive immunotherapeutic materials and discusses the critical roles of controlled release of immunoactive agents from bioresponsive materials in recruiting, housing, and manipulating immune cells for evoking desired immune responses. Challenges and future directions from the perspective of clinical translation are also discussed.

Structure-guided assembly of an influenza spike nanobicelle vaccine provides pan H1 intranasal protection

Development of intranasal vaccines for respiratory viruses has gained popularity. However, currently only a live-attenuated influenza vaccine is FDA-approved for intranasal administration. Here, we focused on influenza virus as it circulates seasonally, has pandemic potential, and has vaccine formulations that present hemagglutinin (HA) in different structural arrangements. These display differences have not been correlated with induction of pan-H1 antibodies or shown to provide intranasal protection. Using electron microscopy, biochemistry and animal studies, we identified HA complexes arranged as lipid discs with multiple trimeric HAs displayed along the perimeter, termed spike nanobicelles (SNB). We utilized a structure-guided approach to synthesize in vitro assembled spiked nanobicelles (IA-SNB) from a classical 1934 H1N1 influenza virus. IA-SNBs elicited pan-H1 antibodies and provided protection against antigenically divergent H1N1 viruses via intranasal immunizations. Viral glycoprotein spikes displayed as SNBs could aid in combating antigenic variation and provide innovative intranasal vaccines to aid universal influenza vaccine development.

Targeting Yezo Virus Structural Proteins for Multi-Epitope Vaccine Design Using Immunoinformatics Approach

A novel tick-borne orthonairovirus called the Yezo virus (YEZV), primarily transmitted by the Ixodes persulcatus tick, has been recently discovered and poses significant threats to human health. The YEZV is considered endemic in Japan and China. Clinical symptoms associated with this virus include thrombocytopenia, fatigue, headache, leukopenia, fever, depression, and neurological complications ranging from mild febrile illness to severe outcomes like meningitis and encephalitis. At present, there is no treatment or vaccine readily accessible for this pathogenic virus. Therefore, this research employed an immunoinformatics approach to pinpoint potential vaccine targets within the YEZV through an extensive examination of its structural proteins. Three structural proteins were chosen using specific criteria to pinpoint T-cell and B-cell epitopes, which were subsequently validated through interferon-gamma induction. Six overlapping epitopes for cytotoxic T-lymphocytes (CTL), helper T-lymphocytes (HTL), and linear B-lymphocytes (LBL) were selected to construct a multi-epitope vaccine, achieving a 92.29% coverage of the global population. These epitopes were then fused with the 50S ribosomal protein L7/L12 adjuvant to improve protection against international strains. The three-dimensional structure of the designed vaccine construct underwent an extensive evaluation through structural analysis. Following molecular docking studies, the YEZV vaccine construct emerged as a candidate for further investigation, showing the lowest binding energy (-78.7 kcal/mol) along with favorable physiochemical and immunological properties. Immune simulation and molecular dynamics studies demonstrated its stability and potential to induce a strong immune response within the host cells. This comprehensive analysis indicates that the designed vaccine construct could offer protection against the YEZV. It is crucial to conduct additional in vitro and in vivo experiments to verify its safety and effectiveness.

Lymph node-targeted STING agonist nanovaccine against chronic HBV infection

Chronic hepatitis B virus (HBV) infection is a global health problem that substantially increases the risk of developing liver disease. The development of a novel strategy to induce anti-HB seroconversion and achieve a long-lasting immune response against chronic HBV infection remains challenging. Here, we found that chronic HBV infection affected the signaling pathway involved in STING-mediated induction of host immune responses in dendritic cells (DCs) and then generated a lymph node-targeted nanovaccine that co-delivered hepatitis B surface antigen (HBsAg) and cyclic diguanylate monophosphate (c-di-GMP) (named the PP-SG nanovaccine). The feasibility and efficiency of the PP-SG nanovaccine for CHB treatment were evaluated in HBV-carrier mice. Serum samples were analyzed for HBsAg, anti-HBs, HBV DNA, and alanine aminotransferase levels, and liver samples were evaluated for HBV DNA and RNA and HBcAg, accompanied by an analysis of HBV-specific cellular and humoral immune responses during PP-SG nanovaccine treatment. The PP-SG nanovaccine increased antigen phagocytosis and DC maturation, efficiently and safely eliminated HBV, achieved a long-lasting immune response against HBV reinjection, and disrupted chronic HBV infection-induced immune tolerance, as characterized by the generation and multifunctionality of HBV-specific CD8+ T and CD4+ T cells and the downregulation of immune checkpoint molecules. HBV-carrier mice immunized with the PP-SG nanovaccine achieved partial anti-HBs seroconversion. The PP-SG nanovaccine can induce sufficient and persistent viral suppression and achieve anti-HBs seroconversion, rendering it a promising vaccine candidate for clinical chronic hepatitis B therapy.

Spatial immunophenotyping using multiplexed imaging of immune follicles in secondary lymphoid tissues

Secondary lymphoid organs (SLOs), including tonsils (TS), lymph nodes (LN), and Peyer's Patches, exhibit complementary immune functions. However, little is known about the spatial organization of immune cells and extracellular matrix (ECM) in the SLOs. Traditional imaging is limited to a few markers, confining our understanding of the differences between the SLOs. Herein, imaging mass cytometry addressed this gap by simultaneously profiling 25-plex proteins in SLO tissues at subcellular resolution. The antibody panel targeted immune, stromal, chemokine, epigenetic, and functional markers. For robust cell identification, a computational workflow SpatialVizPheno was developed to spatially phenotype 999,970 cells using two approaches, including manual gating and semi-supervised gating, iterative clustering, and annotation. LN exhibited the highest density of B cells while the intestinal tissues contained the highest proportion of regulatory and follicular helper T cells. SpatialVizPheno identified the most prevalent interaction between follicular dendritic cells and stromal cells (SCs), plasmablasts/plasma cells, and the SCs across the lymphoid tissues. Collagen-enriched regions were associated with the spatial orientation of B cell follicles in both TS and LN tissues, but not in intestinal lymphoid tissues. Such spatial differences of immunophenotypes and ECM in different SLO tissues can be used to quantify the relationship between cellular organization and ultimate immune responses.

A genetically engineered neuronal membrane-based nanotoxoid elicits protective immunity against neurotoxins

Given their dangerous effects on the nervous system, neurotoxins represent a significant threat to public health. Various therapeutic approaches, including chelating agents, receptor decoys, and toxin-neutralizing antibodies, have been explored. While prophylactic vaccines are desirable, it is oftentimes difficult to effectively balance their safety and efficacy given the highly dangerous nature of neurotoxins. To address this, we report here on a nanovaccine against neurotoxins that leverages the detoxifying properties of cell membrane-coated nanoparticles. A genetically modified cell line with constitutive overexpression of the α7 nicotinic acetylcholine receptor is developed as a membrane source to generate biomimetic nanoparticles that can effectively and irreversibly bind to α-bungarotoxin, a model neurotoxin. This abrogates the biological activity of the toxin, enabling the resulting nanotoxoid to be safely delivered into the body and processed by the immune system. When co-administered with an immunological adjuvant, a strong humoral response against α-bungarotoxin is generated that protects vaccinated mice against a lethal dose of the toxin. Overall, this work highlights the potential of using genetic modification strategies to develop nanotoxoid formulations against various biological threats.

Synthesis of a dendritic cell-targeted self-assembled polymeric nanoparticle for selective delivery of mRNA vaccines to elicit enhanced immune responses

Recent development of SARS-CoV-2 spike mRNA vaccines to control the pandemic is a breakthrough in the field of vaccine development. mRNA vaccines are generally formulated with lipid nanoparticles (LNPs) which are composed of several lipids with specific ratios; however, they generally lack selective delivery. To develop a selective delivery method for mRNA vaccine formulation, we reported here the synthesis of polymeric nanoparticles (PNPs) composed of a guanidine copolymer containing zwitterionic groups and a dendritic cell (DC)-targeted aryl-trimannoside ligand for encapsulation and selective delivery of an mRNA to dendritic cells. A DC-targeted SARS-CoV-2 spike mRNA-PNP vaccine was shown to elicit a stronger protective immune response in mice compared to the traditional mRNA-LNP vaccine and those without the selective delivery design. It is anticipated that this technology is generally applicable to other mRNA vaccines for DC-targeted delivery with enhanced immune response.

A Nanoparticle Vaccine Displaying Conserved Epitopes of the Preexisting Neutralizing Antibody Confers Broad Protection against SARS-CoV-2 Variants

The rapid development of the SARS-CoV-2 vaccine has been used to prevent the spread of coronavirus 2019 (COVID-19). However, the ongoing and future pandemics caused by SARS-CoV-2 variants and mutations underscore the need for effective vaccines that provide broad-spectrum protection. Here, we developed a nanoparticle vaccine with broad protection against divergent SARS-CoV-2 variants. The corresponding conserved epitopes of the preexisting neutralizing (CePn) antibody were presented on a self-assembling Helicobacter pylori ferritin to generate the CePnF nanoparticle. Intranasal immunization of mice with CePnF nanoparticles induced robust humoral, cellular, and mucosal immune responses and a long-lasting immunity. The CePnF-induced antibodies exhibited cross-reactivity and neutralizing activity against different coronaviruses (CoVs). CePnF vaccination significantly inhibited the replication and pathology of SARS-CoV-2 Delta, WIV04, and Omicron strains in hACE2 transgenic mice and, thus, conferred broad protection against these SARS-CoV-2 variants. Our constructed nanovaccine targeting the conserved epitopes of the preexisting neutralizing antibodies can serve as a promising candidate for a universal SARS-CoV-2 vaccine.

Interactions between nanoparticles and lymphatic systems: Mechanisms and applications in drug delivery

The lymphatic system has garnered significant attention in drug delivery research due to the advantages it offers, such as enhancing systemic exposure and enabling lymph node targeting for nanomedicines via the lymphatic delivery route. The journey of drug carriers involves transport from the administration site to the lymphatic vessels, traversing the lymph before entering the bloodstream or targeting specific lymph nodes. However, the anatomical and physiological barriers of the lymphatic system play a pivotal role in influencing the behavior and efficiency of carriers. To expedite research and subsequent clinical translation, this review begins by introducing the composition and classification of the lymphatic system. Subsequently, we explore the routes and mechanisms through which nanoparticles enter lymphatic vessels and lymph nodes. The review further delves into the interactions between nanomedicine and body fluids at the administration site or within lymphatic vessels. Finally, we provide a comprehensive overview of recent advancements in lymphatic delivery systems, addressing the challenges and opportunities inherent in current systems for delivering macromolecules and vaccines.

mRNA-LNP prime boost evolves precursors toward VRC01-like broadly neutralizing antibodies in preclinical humanized mouse models

Germline-targeting (GT) protein immunogens to induce VRC01-class broadly neutralizing antibodies (bnAbs) to the CD4-binding site of the HIV envelope (Env) have shown promise in clinical trials. Here, we preclinically validated a lipid nanoparticle-encapsulated nucleoside mRNA (mRNA-LNP) encoding eOD-GT8 60mer as a soluble self-assembling nanoparticle in mouse models. In a model with three humanized B cell lineages bearing distinct VRC01-precursor B cell receptors (BCRs) with similar affinities for eOD-GT8, all lineages could be simultaneously primed and undergo diversification and affinity maturation without exclusionary competition. Boosts drove precursor B cell participation in germinal centers; the accumulation of somatic hypermutations, including in key VRC01-class positions; and affinity maturation to boost and native-like antigens in two of the three precursor lineages. We have preclinically validated a prime-boost regimen of soluble self-assembling nanoparticles encoded by mRNA-LNP, demonstrating that multiple lineages can be primed, boosted, and diversified along the bnAb pathway.

Antigen-Clustered Nanovaccine Achieves Long-Term Tumor Remission by Promoting B/CD 4 T Cell Crosstalk

Current cancer vaccines using T cell epitopes activate antitumor T cell immunity through dendritic cell/macrophage-mediated antigen presentation, but they lack the ability to promote B/CD4 T cell crosstalk, limiting their anticancer efficacy. We developed antigen-clustered nanovaccine (ACNVax) to achieve long-term tumor remission by promoting B/CD4 T cell crosstalk. The topographic features of ACNVax were achieved using an iron nanoparticle core attached with an optimal number of gold nanoparticles, where the clusters of HER2 B/CD4 T cell epitopes were conjugated on the gold surface with an optimal intercluster distance of 5-10 nm. ACNVax effectively trafficked to lymph nodes and cross-linked with BCR, which are essential for stimulating B cell antigen presentation-mediated B/CD4 T cell crosstalk in vitro and in vivo. ACNVax, combined with anti-PD-1, achieved long-term tumor remission (>200 days) with 80% complete response in mice with HER2+ breast cancer. ACNVax not only remodeled the tumor immune microenvironment but also induced a long-term immune memory, as evidenced by complete rejection of tumor rechallenge and a high level of antigen-specific memory B, CD4, and CD8 cells in mice (>200 days). This study provides a cancer vaccine design strategy, using B/CD4 T cell epitopes in an antigen clustered topography, to achieve long-term durable anticancer efficacy through promoting B/CD4 T cell crosstalk.

Engineered mRNA Delivery Systems for Biomedical Applications

Messenger RNA (mRNA)-based therapeutic strategies have shown remarkable promise in preventing and treating a staggering range of diseases. Optimizing the structure and delivery system of engineered mRNA has greatly improved its stability, immunogenicity, and protein expression levels, which has led to a wider range of uses for mRNA therapeutics. Herein, a thorough analysis of the optimization strategies used in the structure of mRNA is first provided and delivery systems are described in great detail. Furthermore, the latest advancements in biomedical engineering for mRNA technology, including its applications in combatting infectious diseases, treating cancer, providing protein replacement therapy, conducting gene editing, and more, are summarized. Lastly, a perspective on forthcoming challenges and prospects concerning the advancement of mRNA therapeutics is offered. Despite these challenges, mRNA-based therapeutics remain promising, with the potential to revolutionize disease treatment and contribute to significant advancements in the biomedical field.

Development and Immunological Evaluation of a Multiantigen Thermostable Nanovaccine Adjuvanted with T-Cell-Activating Scaffold for African Swine Fever

African swine fever is an acute and highly contagious infectious disease with a mortality rate of up to 100%. The lack of commercial vaccines and drugs is a serious economic threat to the global pig industry. Cell-mediated immunity plays an essential role in protection against viral infection. We previously reported the rational design of a T-cell-activating thermostable scaffold (RPT) for antigen delivery and improved cellular immunity. We conjugated antigens P30, P54, P72, CD2 V, and CP312R to RPT, using a SpyCatcher/SpyTag covalent attachment strategy to construct nanovaccines (multiantigens-RPT). Multiantigens-RPT exhibited significantly higher thermal, storage, and freeze-thaw stability. The specific antibodies IgG and IgG2a of the multiantigen-RPT-immunized were higher than the antigens cocktail-immunized by approximately 10-100 times. ELISpot demonstrated that more IFN-γ-secreting cells were produced by the multiantigen-RPT-immunized than by the antigens cocktail-immunized. Delivery of the multiantigen nanovaccine by a T-cell-activating scaffold induced strong humoral and cellular immune responses in mice and pigs and is a potentially useful candidate vaccine for the African swine fever virus.

Modularized viromimetic polymer nanoparticle vaccines (VPNVaxs) to elicit durable and effective humoral immune responses

Virus-like particle (VLP) vaccines had shown great potential during the COVID-19 pandemic, and was thought to be the next generation of antiviral vaccine technology due to viromimetic structures. However, the time-consuming and complicated processes in establishing a current recombinant-protein-based VLP vaccine has limited its quick launch to the out-bursting pandemic. To simplify and optimize VLP vaccine design, we herein report a kind of viromimetic polymer nanoparticle vaccine (VPNVax), with subunit receptor-binding domain (RBD) proteins conjugated to the surface of polyethylene glycol-b-polylactic acid (PEG-b-PLA) nanoparticles for vaccination against SARS-CoV-2. The preparation of VPNVax based on synthetic polymer particle and chemical post-conjugation makes it possible to rapidly replace the antigens and construct matched vaccines at the emergence of different viruses. Using this modular preparation system, we identified that VPNVax with surface protein coverage of 20%-25% had the best immunostimulatory activity, which could keep high levels of specific antibody titers over 5 months and induce virus neutralizing activity when combined with an aluminum adjuvant. Moreover, the polymer nano-vectors could be armed with more immune-adjuvant functions by loading immunostimulant agents or chemical chirality design. This VPNVax platform provides a novel kind of rapidly producing and efficient vaccine against different variants of SARS-CoV-2 as well as other viral pandemics.

Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Enhancing antibody responses by multivalent antigen display on thymus-independent DNA origami scaffolds

Protein-based virus-like particles (P-VLPs) are commonly used to spatially organize antigens and enhance humoral immunity through multivalent antigen display. However, P-VLPs are thymus-dependent antigens that are themselves immunogenic and can induce B cell responses that may neutralize the platform. Here, we investigate thymus-independent DNA origami as an alternative material for multivalent antigen display using the receptor binding domain (RBD) of the SARS-CoV-2 spike protein, the primary target of neutralizing antibody responses. Sequential immunization of mice with DNA-based VLPs (DNA-VLPs) elicits protective neutralizing antibodies to SARS-CoV-2 in a manner that depends on the valency of the antigen displayed and on T cell help. Importantly, the immune sera do not contain boosted, class-switched antibodies against the DNA scaffold, in contrast to P-VLPs that elicit strong B cell memory against both the target antigen and the scaffold. Thus, DNA-VLPs enhance target antigen immunogenicity without generating scaffold-directed immunity and thereby offer an important alternative material for particulate vaccine design.

The mRNA vaccine, a swift warhead against a moving infectious disease target

INTRODUCTION

The rapid development of mRNA vaccines against SARS-CoV-2 has revolutionized vaccinology, offering hope for swift responses to emerging infectious diseases. Initially met with skepticism, mRNA vaccines have proven effective and safe, reducing vaccine hesitancy amid the evolving COVID-19 pandemic. The COVID-19 pandemic has demonstrated that the time required to modify mRNA vaccines to counter new mutant strains is significantly shorter than the time it takes for pathogens to mutate and generate new variants that can thrive in vaccinated populations. This highlights the notion that mRNA vaccine technology appears to be outpacing viruses in the ongoing evolutionary race.

AREAS COVERED

This review article offers valuable insights into several crucial aspects of mRNA vaccine development and deployment, including the fundamentals of mRNA vaccine design and synthesis, the utilization of delivery systems, considerations regarding vaccine safety, the longevity of the immune response, strategies for modifying the original mRNA vaccine to address emerging mutant strains, as well as addressing vaccine hesitancy and potential approaches to mitigate reluctance.

EXPERT OPINION

Challenges such as stability, storage, manufacturing complexities, production capacity, allergic reactions, long-term effects, accessibility, and misinformation must be addressed. Despite these hurdles, mRNA vaccine technology holds promise for revolutionizing future vaccination strategies.

DNA nanostructures as biomolecular scaffolds for antigen display

Nanoparticle-based vaccines offer a multivalent approach for antigen display, efficiently activating T and B cells in the lymph nodes. Among various nanoparticle design strategies, DNA nanotechnology offers an innovative alternative platform, featuring high modularity, spatial addressing, nanoscale regulation, high functional group density, and lower self-antigenicity. This review delves into the potential of DNA nanostructures as biomolecular scaffolds for antigen display, addressing: (1) immunological mechanisms behind nanovaccines and commonly used nanoparticles in their design, (2) techniques for characterizing protein NP-antigen complexes, (3) advancements in DNA nanotechnology and DNA-protein assembly approach, (4) strategies for precise antigen presentation on DNA scaffolds, and (5) current applications and future possibilities of DNA scaffolds in antigen display. This analysis aims to highlight the transformative potential of DNA nanoscaffolds in immunology and vaccinology. This article is categorized under: Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Nanovaccines for Advancing Long-Lasting Immunity against Infectious Diseases

Infectious diseases, particularly life-threatening pathogens such as small pox and influenza, have substantial implications on public health and global economies. Vaccination is a key approach to combat existing and emerging pathogens. Immunological memory is an essential characteristic used to evaluate vaccine efficacy and durability and the basis for the long-term effects of vaccines in protecting against future infections; however, optimizing the potency, improving the quality, and enhancing the durability of immune responses remains challenging and a focus for research involving investigation of nanovaccine technologies. In this review, we describe how nanovaccines can address the challenges for conventional vaccines in stimulating adaptive immune memory responses to protect against reinfection. We discuss protein and nonprotein nanoparticles as useful antigen platforms, including those with highly ordered and repetitive antigen array presentation to enhance immunogenicity through cross-linking with multiple B cell receptors, and with a focus on antigen properties. In addition, we describe how nanoadjuvants can improve immune responses by providing enhanced access to lymph nodes, lymphnode targeting, germinal center retention, and long-lasting immune response generation. Nanotechnology has the advantage to facilitate vaccine induction of long-lasting immunity against infectious diseases, now and in the future.

Thermostable T Cell Multiepitope Nanoparticle Antigens Inducing Potent Immune Responses against the Swine Fever Virus

African swine fever (ASF) is caused by the African swine fever virus (ASFV) and is a highly contagious, acute, febrile disease that has high morbidity and mortality rates in domestic and wild swine. However, a safe and effective vaccine against ASF remains unavailable as single antigens fail to provide sufficient protection. Therefore, a combination of multiple antigens with an efficient delivery system might be an alternative strategy. Herein, a de novo-designed antigen with multiple T-cell epitopes (TEPs) of ASFV was conjugated for surface display on self-assembled nanoparticles (NPs) of Aquifex aeolicus lumazine synthase (AaLS) and Quasibacillus thermotolerans encapsulin (QT) through the SpyCatcher/SpyTag system to construct nanovaccines (TEP-Spy-NPs). TEP-Spy-NPs exhibited significantly more thermal, storage, and freeze-thaw stability in comparison to TEP monomers. TEP-Spy-NPs were highly immunogenic and induced strong polyclonal antibody responses in mice and pigs. The specific antibody titers against the TEP of the TEP-Spy-AaLS and TEP-Spy-QT groups were significantly higher than those of the TEP monomer immune group after the second booster immunization. The antibody titer against TEP of the TEP-Spy-QT group was approximately twice that of the TEP-Spy-AaLS group in mice. ELISpot analysis demonstrated that more IFN-γ- and IL-2-secreting splenic lymphocytes were produced by TEP-Spy-AaLS- and TEP-Spy-QT-immunized mice than by TEP monomer-immunized mice. TEP-Spy-NPs elicited stronger cellular immunity and in vivo immunity in immunized pigs than did TEP monomers. Thus, the TEP nanovaccine successfully induced strong humoral and cellular immune responses in mice and pigs, and TEP-Spy-NPs have the potential as candidate vaccines for ASFV.

A gB nanoparticle vaccine elicits a protective neutralizing antibody response against EBV

Epstein-Barr virus (EBV) is a global public health concern, as it is known to cause multiple diseases while also being etiologically associated with a wide range of epithelial and lymphoid malignancies. Currently, there is no available prophylactic vaccine against EBV. gB is the EBV fusion protein that mediates viral membrane fusion and participates in host recognition, making it critical for EBV infection in both B cells and epithelial cells. Here, we present a gB nanoparticle, gB-I53-50 NP, that displays multiple copies of gB. Compared with the gB trimer, gB-I53-50 NP shows improved structural integrity and stability, as well as enhanced immunogenicity in mice and non-human primate (NHP) preclinical models. Immunization and passive transfer demonstrate a robust and durable protective antibody response that protects humanized mice against lethal EBV challenge. This vaccine candidate demonstrates significant potential in preventing EBV infection, providing a possible platform for developing prophylactic vaccines for EBV.

Nanovaccines: A game changing approach in the fight against infectious diseases

The field of nanotechnology has revolutionised global attempts to prevent, treat, and eradicate infectious diseases in the foreseen future. Nanovaccines have proven to be a valuable pawn in this novel technology. Nanovaccines are made up of nanoparticles that are associated with or prepared with components that can stimulate the host's immune system. In addition to their delivery capabilities, the nanocarriers have been demonstrated to possess intrinsic adjuvant properties, working as immune cell stimulators. Thus, nanovaccines have the potential to promote rapid as well as long-lasting humoral and cellular immunity. The nanovaccines have several possible benefits, including site-specific antigen delivery, increased antigen bioavailability, and a diminished adverse effect profile. To avail these benefits, several nanoparticle-based vaccines are being developed, including virus-like particles, liposomes, polymeric nanoparticles, nanogels, lipid nanoparticles, emulsion vaccines, exomes, and inorganic nanoparticles. Inspired by their distinctive properties, researchers are working on the development of nanovaccines for a variety of applications, such as cancer immunotherapy and infectious diseases. Although a few challenges still need to be overcome, such as modulation of the nanoparticle pharmacokinetics to avoid rapid elimination from the bloodstream by the reticuloendothelial system, The future prospects of this technology are also assuring, with multiple options such as personalised vaccines, needle-free formulations, and combination nanovaccines with several promising candidates.

Q fever immunology: the quest for a safe and effective vaccine

Q fever is an infectious zoonotic disease, caused by the Gram-negative bacterium Coxiella burnetii. Transmission occurs from livestock to humans through inhalation of a survival form of the bacterium, the Small Cell Variant, often via handling of animal parturition products. Q fever manifests as an acute self-limiting febrile illness or as a chronic disease with complications such as vasculitis and endocarditis. The current preventative human Q fever vaccine Q-VAX poses limitations on its worldwide implementation due to reactogenic responses in pre-sensitized individuals. Many strategies have been undertaken to develop a universal Q fever vaccine but with little success to date. The mechanisms of the underlying reactogenic responses remain only partially understood and are important factors in the development of a safe Q fever vaccine. This review provides an overview of previous and current experimental vaccines developed for use against Q fever and proposes approaches to develop a vaccine that establishes immunological memory while eliminating harmful reactogenic responses.

Recent Advances of Emerging Spleen-Targeting Nanovaccines for Immunotherapy

Vaccines provide a powerful tool to modulate the immune system for human disease prevention and treatment. Classical vaccines mainly initiate immune responses in the lymph nodes (LNs) after subcutaneous injection. However, some vaccines suffer from inefficient delivery of antigens to LNs, undesired inflammation, and slow immune induction when encountering the rapid proliferation of tumors. Alternatively, the spleen, as the largest secondary lymphoid organ with a high density of antigen-presenting cells (APCs) and lymphocytes, acts as an emerging target organ for vaccinations in the body. Upon intravenous administration, the rationally designed spleen-targeting nanovaccines can be internalized by the APCs in the spleen to induce selective antigen presentation to T and B cells in their specific sub-regions, thereby rapidly boosting durable cellular and humoral immunity. Herein, the recent advances of spleen-targeting nanovaccines for immunotherapy based on the anatomical architectures and functional zones of the spleen, as well as their limitations and perspectives for clinical applications are systematically summarized. The aim is to emphasize the design of innovative nanovaccines for enhanced immunotherapy of intractable diseases in the future.

Current status of nano-vaccinology in veterinary medicine science

Vaccination programmes provide a safe, effective and cost-efficient strategy for maintaining population health. In veterinary medicine, vaccination not only reduces disease within animal populations but also serves to enhance public health by targeting zoonoses. Nevertheless, for many pathogens, an effective vaccine remains elusive. Recently, nanovaccines have proved to be successful for various infectious and non-infectious diseases of animals. These novel technologies, such as virus-like particles, self-assembling proteins, polymeric nanoparticles, liposomes and virosomes, offer great potential for solving many of the vaccine production challenges. Their benefits include low immunotoxicity, antigen stability, enhanced immunogenicity, flexibility sustained release and the ability to evoke both humoral and cellular immune responses. Nanovaccines are more efficient than traditional vaccines due to ease of control and plasticity in their physio-chemical properties. They use a highly targeted immunological approach which can provide strong and long-lasting immunity. This article reviews the currently available nanovaccine technology and considers its utility for both infectious diseases and non-infectious diseases such as auto-immunity and cancer. Future research opportunities and application challenges from bench to clinical usage are also discussed.

Cell-targeted vaccines: implications for adaptive immunity

Recent advancements in immunology and chemistry have facilitated advancements in targeted vaccine technology. Targeting specific cell types, tissue locations, or receptors can allow for modulation of the adaptive immune response to vaccines. This review provides an overview of cellular targets of vaccines, suggests methods of targeting and downstream effects on immune responses, and summarizes general trends in the literature. Understanding the relationships between vaccine targets and subsequent adaptive immune responses is critical for effective vaccine design. This knowledge could facilitate design of more effective, disease-specialized vaccines.

Advanced subunit vaccine delivery technologies: From vaccine cascade obstacles to design strategies

Designing and manufacturing safe and effective vaccines is a crucial challenge for human health worldwide. Research on adjuvant-based subunit vaccines is increasingly being explored to meet clinical needs. Nevertheless, the adaptive immune responses of subunit vaccines are still unfavorable, which may partially be attributed to the immune cascade obstacles and unsatisfactory vaccine design. An extended understanding of the crosstalk between vaccine delivery strategies and immunological mechanisms could provide scientific insight to optimize antigen delivery and improve vaccination efficacy. In this review, we summarized the advanced subunit vaccine delivery technologies from the perspective of vaccine cascade obstacles after administration. The engineered subunit vaccines with lymph node and specific cell targeting ability, antigen cross-presentation, T cell activation properties, and tailorable antigen release patterns may achieve effective immune protection with high precision, efficiency, and stability. We hope this review can provide rational design principles and inspire the exploitation of future subunit vaccines.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

Engineered Ferritin Nanoparticle Vaccines Enable Rapid Screening of Antibody Functionalization to Boost Immune Responses

Employing monoclonal antibodies to target vaccine antigens to different immune cells within lymph nodes where adaptive immunity is initiated can provide a mechanism to fine-tune the magnitude or the quality of immune responses. However, studying the effects of different targeting antibodies head-to-head is challenging due to the lack of a feasible method that allows rapid screening of multiple antibodies for their impact on immunogenicity. Here self-assembling ferritin nanoparticles are prepared that co-display vaccine antigens and the Fc-binding domain of Staphylococcal protein A, allowing rapid attachment of soluble antibodies to the nanoparticle surface. Using this tunable system, ten antibodies targeting different immune cell subsets are screened, with targeting to Clec9a associated with higher serum antibody titers after immunization. Immune cell targeting using ferritin nanoparticles with anti-Clec9a antibodies drives concentrated deposition of antigens within germinal centers, boosting germinal center formation and robust antibody responses. However, the capacity to augment humoral immunity is antigen-dependent, with significant boosting observed for prototypic ovalbumin immunogens but reduced effectiveness with the SARS-CoV-2 RBD. This work provides a rapid platform for screening targeting antibodies, which will accelerate mechanistic insights into optimal delivery strategies for nanoparticle-based vaccines to maximize protective immunity.

Immunization against Zika by entrapping live virus in a subcutaneous self-adjuvanting hydrogel

The threat of new viral outbreaks has heightened the need for ready-to-use vaccines that are safe and effective. Here we show that a subcutaneous vaccine consisting of live Zika virus electrostatically entrapped in a self-adjuvanting hydrogel recruited immune cells at the injection site and provided mice with effective protection against a lethal viral challenge. The hydrogel prevented the escape of the viral particles and upregulated pattern recognition receptors that activated innate antiviral immunity. The local inflammatory niche facilitated the engulfment of the virus by immune cells infiltrating the hydrogel, the processing and cross-presentation of antigens and the expansion of germinal centre B cells and induced robust antigen-specific adaptive responses and immune memory. Inflammatory immune niches entrapping live viruses may facilitate the rapid development of safe and efficacious vaccines.

Advances in mRNA vaccines for viral diseases

Since the onset of the pandemic caused by severe acute respiratory syndrome coronavirus 2, messenger RNA (mRNA) vaccines have demonstrated outstanding performance. mRNA vaccines offer significant advantages over conventional vaccines in production speed and cost-effectiveness, making them an attractive option against other viral diseases. This article reviewed recent advances in viral mRNA vaccines and their delivery systems to provide references and guidance for developing mRNA vaccines for new viral diseases.

The position of Spy Tag/Catcher system in hepatitis B core protein particles affects the immunogenicity and stability of the synthetic vaccine

Presenting exogenous antigens on virus-like particles (VLPs) through "plug-and-display" decoration strategies based on SpyTag/SpyCatcher isopeptide bonding have emerged as attractive technology for vaccine synthesis. However, whether the position of ligation site in VLPs will impose effects on immunogenicity and physiochemical properties of the synthetic vaccine remains rarely investigated. Here in the present work, the well-established hepatitis B core (HBc) protein was used as chassis to construct dual-antigen influenza nanovaccines, with the conserved epitope peptides derived from extracellular domain of matrix protein M2 (M2e) and hemagglutinin (HA) as target antigens. The M2e antigen was genetically fused to the HBc in the MIR region, together with the SpyTag peptide, which was fused either in the MIR region or at the N-terminal of the protein, so that a recombinant HA antigen (rHA) linked to SpyCatcher can be displayed on it, at two different localizations. Both synthetic nanovaccines showed ability in inducing strong M2e and rHA-specific antibodies and cellular immunogenicity; nevertheless, the one in which rHA was conjugated by N-terminal Tag ligation, was superior to another one synthesized by linking the rHA to MIR region SpyTagged-HBc in all aspects, including higher antigen-specific immunogenicity responses, lower anti-HBc carrier antibody, as well as better dispersion stability. Surface charge and hydrophobicity properties of the two synthetic nanovaccines were analyzed, results revealed that linking the rHA to MIR region SpyTagged-HBc lead to more significant and disadvantageous alteration in physiochemical properties of the HBc chassis. This study will expand our knowledge on "plug-and-display" decoration strategies and provide helpful guidance for the rational design of HBc-VLPs based modular vaccines by using SpyTag/Catcher synthesis.

Enhancing antibody responses by multivalent antigen display on thymus-independent DNA origami scaffolds

Multivalent antigen display is a well-established principle to enhance humoral immunity. Protein-based virus-like particles (VLPs) are commonly used to spatially organize antigens. However, protein-based VLPs are limited in their ability to control valency on fixed scaffold geometries and are thymus-dependent antigens that elicit neutralizing B cell memory themselves, which can distract immune responses. Here, we investigated DNA origami as an alternative material for multivalent antigen display in vivo, applied to the receptor binding domain (RBD) of SARS-CoV2 that is the primary antigenic target of neutralizing antibody responses. Icosahedral DNA-VLPs elicited neutralizing antibodies to SARS-CoV-2 in a valency-dependent manner following sequential immunization in mice, quantified by pseudo- and live-virus neutralization assays. Further, induction of B cell memory against the RBD required T cell help, but the immune sera did not contain boosted, class-switched antibodies against the DNA scaffold. This contrasted with protein-based VLP display of the RBD that elicited B cell memory against both the target antigen and the scaffold. Thus, DNA-based VLPs enhance target antigen immunogenicity without generating off-target, scaffold-directed immune memory, thereby offering a potentially important alternative material for particulate vaccine design.

Stimuli-Responsive Polymeric Nanovaccines Toward Next-Generation Immunotherapy

The development of nanovaccines that employ polymeric delivery carriers has garnered substantial interest in therapeutic treatment of cancer and a variety of infectious diseases due to their superior biocompatibility, lower toxicity and reduced immunogenicity. Particularly, stimuli-responsive polymeric nanocarriers show great promise for delivering antigens and adjuvants to targeted immune cells, preventing antigen degradation and clearance, and increasing the uptake of specific antigen-presenting cells, thereby sustaining adaptive immune responses and improving immunotherapy for certain diseases. In this review, the most recent advances in the utilization of stimulus-responsive polymer-based nanovaccines for immunotherapeutic applications are presented. These sophisticated polymeric nanovaccines with diverse functions, aimed at therapeutic administration for disease prevention and immunotherapy, are further classified into several active domains, including pH, temperature, redox, light and ultrasound-sensitive intelligent nanodelivery systems. Finally, the potential strategies for the future design of multifunctional next-generation polymeric nanovaccines by integrating materials science with biological interface are proposed.

Lymph Node Follicle-Targeting STING Agonist Nanoshells Enable Single-Shot M2e Vaccination for Broad and Durable Influenza Protection

The highly conserved matrix protein 2 ectodomain (M2e) of influenza viruses presents a compelling vaccine antigen candidate for stemming the pandemic threat of the mutation-prone pathogen, yet the low immunogenicity of the diminutive M2e peptide renders vaccine development challenging. A highly potent M2e nanoshell vaccine that confers broad and durable influenza protectivity under a single vaccination is shown. Prepared via asymmetric ionic stabilization for nanoscopic curvature formation, polymeric nanoshells co-encapsulating high densities of M2e peptides and stimulator of interferon genes (STING) agonists are prepared. Robust and long-lasting protectivity against heterotypic influenza viruses is achieved with a single administration of the M2e nanoshells in mice. Mechanistically, molecular adjuvancy by the STING agonist and nanoshell-mediated prolongation of M2e antigen exposure in the lymph node follicles synergistically contribute to the heightened anti-M2e humoral responses. STING agonist-triggered T cell helper functions and extended residence of M2e peptides in the follicular dendritic cell network provide a favorable microenvironment that induces Th1-biased antibody production against the diminutive antigen. These findings highlight a versatile nanoparticulate design that leverages innate immune pathways for enhancing the immunogenicity of weak immunogens. The single-shot nanovaccine further provides a translationally viable platform for pandemic preparedness.

Single-component multilayered self-assembling protein nanoparticles presenting glycan-trimmed uncleaved prefusion optimized envelope trimmers as HIV-1 vaccine candidates

Uncleaved prefusion-optimized (UFO) design can stabilize diverse HIV-1 envelope glycoproteins (Envs). Single-component, self-assembling protein nanoparticles (1c-SApNP) can display 8 or 20 native-like Env trimers as vaccine candidates. We characterize the biophysical, structural, and antigenic properties of 1c-SApNPs that present the BG505 UFO trimer with wildtype and modified glycans. For 1c-SApNPs, glycan trimming improves recognition of the CD4 binding site without affecting broadly neutralizing antibodies (bNAbs) to major glycan epitopes. In mice, rabbits, and nonhuman primates, glycan trimming increases the frequency of vaccine responders (FVR) and steers antibody responses away from immunodominant glycan holes and glycan patches. The mechanism of vaccine-induced immunity is examined in mice. Compared with the UFO trimer, the multilayered E2p and I3-01v9 1c-SApNPs show 420 times longer retention in lymph node follicles, 20-32 times greater presentation on follicular dendritic cell dendrites, and up-to-4 times stronger germinal center reactions. These findings can inform future HIV-1 vaccine development.