Induction of Potent Neutralizing Antibody Responses by a Designed Protein Nanoparticle Vaccine for Respiratory Syncytial Virus

Rapid and efficient immune response induced by a designed modular cholera toxin B subunit (CTB)-based self-assembling nanoparticle

Modular self-assembling nanoparticle vaccines, represent a cutting-edge approach in immunology with the potential to revolutionize vaccine design and efficacy. Although many innovative efficient modular self-assembling nanoparticles have been designed for vaccination, the immune activation characteristics underlying such strong protection remain poorly understood, limiting the further expansion of such nanocarrier. Here, we prepared a novel modular nanovaccine, which self-assembled via a pentamer cholera toxin B subunit (CTB) domain and an unnatural trimer domain, presenting S. Paratyphi A O-polysaccharide antigen, and investigated its rapid immune activation mechanism. The nanovaccine efficiently targets draining lymph nodes and antigen-presenting cells, facilitating co-localization with Golgi and endoplasmic reticulum. In addition, dendritic cells, macrophages, B cells, and neutrophils potentially participate in antigen presentation, unveiling a dynamic change of the vaccines in lymph nodes. Single-cell RNA sequencing at early stage and iN vivo/iN vitro experiments reveal its potent humoral immune response capabilities and protection effects. This nanoparticle outperforms traditional CTB carriers in eliciting robust prophylactic effects in various infection models. This work not only provides a promising and efficient candidate vaccine, but also promotes the design and application of the new type of self-assembled nanoparticle, offering a safe and promising vaccination strategy for infection diseases.

Nanoparticles in Subunit Vaccines: Immunological Foundations, Categories, and Applications

Subunit vaccines, significant in next-generation vaccine development, offer precise targeting of immune responses by focusing on specific antigens. However, this precision often comes at the cost of eliciting strong and durable immunity, posing a great challenge to vaccine design. To address this limitation, recent advancements in nanoparticles (NPs) are utilized to enhance antigen delivery efficiency and boost vaccine efficacy. This review examines how the physicochemical properties of NPs influence various stages of the immune response during vaccine delivery and analyzes how different NP types contribute to immune activation and enhance vaccine performance. It then explores the unique characteristics and immune activation mechanisms of these NPs, along with their recent advancements, and highlights their application in subunit vaccines targeting infectious diseases and cancer. Finally, it discusses the challenges in NP-based vaccine development and proposes future directions for innovation in this promising field.

Protein nanoparticle vaccines induce potent neutralizing antibody responses against MERS-CoV

Middle East respiratory syndrome coronavirus (MERS-CoV) is a betacoronavirus that causes severe respiratory illness in humans. There are no licensed vaccines against MERS-CoV and only a few candidates in phase I clinical trials. Here, we develop MERS-CoV vaccines utilizing a computationally designed protein nanoparticle platform that has generated safe and immunogenic vaccines against various enveloped viruses, including a licensed vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Two-component nanoparticles displaying spike (S)-derived antigens induce neutralizing responses and protect mice against challenge with mouse-adapted MERS-CoV. Epitope mapping reveals the dominant responses elicited by immunogens displaying the prefusion-stabilized S-2P trimer, receptor binding domain (RBD), or N-terminal domain (NTD). An RBD nanoparticle elicits antibodies targeting multiple non-overlapping epitopes in the RBD. Our findings demonstrate the potential of two-component nanoparticle vaccine candidates for MERS-CoV and suggest that this platform technology could be broadly applicable to betacoronavirus vaccine development.

Hierarchical design of pseudosymmetric protein nanocages

Discrete protein assemblies ranging from hundreds of kilodaltons to hundreds of megadaltons in size are a ubiquitous feature of biological systems and perform highly specialized functions1,2. Despite remarkable recent progress in accurately designing new self-assembling proteins, the size and complexity of these assemblies has been limited by a reliance on strict symmetry3. Here, inspired by the pseudosymmetry observed in bacterial microcompartments and viral capsids, we developed a hierarchical computational method for designing large pseudosymmetric self-assembling protein nanomaterials. We computationally designed pseudosymmetric heterooligomeric components and used them to create discrete, cage-like protein assemblies with icosahedral symmetry containing 240, 540 and 960 subunits. At 49, 71 and 96 nm diameter, these nanocages are the largest bounded computationally designed protein assemblies generated to date. More broadly, by moving beyond strict symmetry, our work substantially broadens the variety of self-assembling protein architectures that are accessible through design.

Four-component protein nanocages designed by programmed symmetry breaking

Four, eight or twenty C3 symmetric protein trimers can be arranged with tetrahedral, octahedral or icosahedral point group symmetry to generate closed cage-like structures1,2. Viruses access more complex higher triangulation number icosahedral architectures by breaking perfect point group symmetry3-9, but nature appears not to have explored similar symmetry breaking for tetrahedral or octahedral symmetries. Here we describe a general design strategy for building higher triangulation number architectures starting from regular polyhedra through pseudosymmetrization of trimeric building blocks. Electron microscopy confirms the structures of T = 4 cages with 48 (tetrahedral), 96 (octahedral) and 240 (icosahedral) subunits, each with 4 distinct chains and 6 different protein-protein interfaces, and diameters of 33 nm, 43 nm and 75 nm, respectively. Higher triangulation number viruses possess very sophisticated functionalities; our general route to higher triangulation number nanocages should similarly enable a next generation of multiple antigen-displaying vaccine candidates10,11 and targeted delivery vehicles12,13.

Designed, Programmable Protein Cages Utilizing Diverse Metal Coordination Geometries Show Reversible, pH-Dependent Assembly

The rational design and production of a novel series of engineered protein cages are presented, which have emerged as versatile and adaptable platforms with significant applications in biomedicine. These protein cages are assembled from multiple protein subunits, and precise control over their interactions is crucial for regulating assembly and disassembly, such as the on-demand release of encapsulated therapeutic agents. This approach employs a homo-undecameric, ring-shaped protein scaffold with strategically positioned metal binding sites. These engineered proteins can self-assemble into highly stable cages in the presence of cobalt or zinc ions. Furthermore, the cages can be disassembled on demand by employing external triggers such as chelating agents and changes in pH. Interestingly, for certain triggers, the disassembly process is reversible, allowing the cages to reassemble upon reversal or outcompeting of triggering conditions/agents. This work offers a promising platform for the development of advanced drug delivery systems and other biomedical applications.

Development of KSHV vaccine platforms and chimeric MHV68-K-K8.1 glycoprotein for evaluating the in vivo immunogenicity and efficacy of KSHV vaccine candidates

Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus 8 is an etiological agent of Kaposi's Sarcoma, multicentric Castleman's disease, and primary effusion lymphoma. Considering the high seroprevalence reaching up to 80% in sub-Saharan Africa, an effective vaccine is crucial for preventing KSHV infection. However, vaccine development has been limited due to the lack of an effective animal model that supports KSHV infection. Murine Herpesvirus 68 (MHV68), a natural mouse pathogen persisting lifelong post-infection, presents a promising model for KSHV infection. In this study, we developed KSHV vaccine and a chimeric MHV68 carrying the KSHV glycoprotein, serving as a surrogate challenge virus for testing KSHV vaccines in a mouse model. Among KSHV virion glycoproteins, K8.1 is the most abundant envelope glycoprotein with the highest immunogenicity. We developed two K8.1 vaccines: K8.1 mRNA-lipid nanoparticle (LNP) vaccine and K8.126-87-Ferritin (FT) nanoparticle vaccines. Both induced humoral responses in immunized mice, whereas K8.1 mRNA LNP also induced T cell responses. Using BACmid-mediated homologous recombination, the MHV68 M7 (gp150) gene was replaced with KSHV K8.1 gene to generate chimeric MHV68-K-K8.1. MHV68-K-K8.1 established acute and latent infection in the lungs and spleens of infected mice, respectively. Mice immunized with K8.1 mRNA LNP or K8.126-87-FT showed a reduction of MHV68-K-K8.1 titer but not MHV68 wild type (WT) titer in the lung. In addition, viral reactivation of MHV68-K-K8.1 was also significantly reduced in K8.1 mRNA LNP-immunized mice. This study demonstrates the effectiveness of two vaccine candidates in providing immunity against KSHV K8.1 and introduces a surrogate MHV68 system for evaluating vaccine efficacy in vivo.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) is a prevalent virus that establishes lifelong persistent infection in humans and is linked to several malignancies. While antiretroviral therapy has reduced Kaposi's Sarcoma (KS) complications in people with HIV, KS still affects individuals with well-controlled HIV, older men without HIV, and transplant recipients. Despite its significant impact on human health, however, research on KSHV vaccine has been limited, mainly due to the lack of interest and the absence of a suitable animal model. This study addresses these challenges by developing KSHV K8.1 vaccine with two platforms, mRNA lipid nanoparticle (LNP) and FT nanoparticle. Additionally, chimeric virus, MHV68-K-K8.1, was created to evaluate KSHV vaccine efficacy in vivo. Vaccination of K8.1 mRNA LNP or K8.126-87-FT significantly reduced MHV68-K-K8.1 titers. Developing an effective KSHV vaccine requires an innovative approach to ensure safety and efficacy, especially for the immunocompromised population and people with limited healthcare resources. This study could be a potential blueprint for future KSHV vaccine development.

Atomic molecular dynamics simulation advances of de novo-designed proteins

Proteins are vital biological macromolecules that execute biological functions and form the core of synthetic biological systems. The history of de novo protein has evolved from initial successes in subordinate structural design to more intricate protein creation, challenging the complexities of natural proteins. Recent strides in protein design have leveraged computational methods to craft proteins for functions beyond their natural capabilities. Molecular dynamics (MD) simulations have emerged as a crucial tool for comprehending the structural and dynamic properties of de novo-designed proteins. In this study, we examined the pivotal role of MD simulations in elucidating the sampling methods, force field, water models, stability, and dynamics of de novo-designed proteins, highlighting their potential applications in diverse fields. The synergy between computational modeling and experimental validation continued to play a crucial role in the creation of novel proteins tailored for specific functions and applications.

Self-assembled protein vesicles as vaccine delivery platform to enhance antigen-specific immune responses

Self-assembling protein nanoparticles are beneficial platforms for enhancing the often weak and short-lived immune responses elicited by subunit vaccines. Their benefits include multivalency, similar sizes as pathogens and control of antigen orientation. Previously, the design, preparation, and characterization of self-assembling protein vesicles presenting fluorescent proteins and enzymes on the outer vesicle surface have been reported. Here, a full-size model antigen protein, ovalbumin (OVA), was genetically fused to the recombinant vesicle building blocks and incorporated into protein vesicles via self-assembly. Characterization of OVA protein vesicles showed room temperature stability and tunable size. Immunization of mice with OVA protein vesicles induced strong antigen-specific humoral and cellular immune responses. This work demonstrates the potential of protein vesicles as a modular platform for delivering full-size antigen proteins that can be extended to pathogen antigens to induce antigen specific immune responses.

Protein Cage Directed Assembly of Binary Nanoparticle Superlattices

Inorganic nanoparticles can be assembled into superlattices with unique optical and magnetic properties arising from collective behavior. Protein cages can be utilized to guide this assembly by encapsulating nanoparticles and promoting their assembly into ordered structures. However, creating ordered multi-component structures with different protein cage types and sizes remains a challenge. Here, the co-crystallization of two different protein cages (cowpea chlorotic mottle virus and ferritin) characterized by opposing surface charges and unequal diameter is shown. Precise tuning of the electrostatic attraction between the cages enabled the preparation of binary crystals with dimensions up to several tens of micrometers. Additionally, binary metal nanoparticle superlattices are achieved by loading gold and iron oxide nanoparticles inside the cavities of the protein cages. The resulting structure adopts an AB2 FCC configuration that also impacts the dipolar coupling between the particles and hence the optical properties of the crystals, providing key insight for the future preparation of plasmonic and magnetic nanoparticle metamaterials.

Vaccine and therapeutic agents against the respiratory syncytial virus: resolved and unresolved issue

Respiratory syncytial virus (RSV) is a predominant pathogen responsible for respiratory tract infections among infants, the elderly, and immunocompromised individuals. In recent years, significant progress has been made in innovative vaccines and therapeutic agents targeting RSV. Nevertheless, numerous challenges and bottlenecks persist in the prevention and treatment of RSV infections. This review will provide an overview of the resolved and unresolved issues surrounding the development of vaccines and therapeutic agents against RSV. As of September 2024, three RSV vaccines against acute lower respiratory infections (ALRI) have been approved globally. Additionally, there have been notable progress in the realm of passive immunoprophylactic antibodies, with the monoclonal antibody nirsevimab receiving regulatory approval for the prevention of RSV infections in infants. Furthermore, a variety of RSV therapeutic agents are currently under clinical investigation, with the potential to yield breakthrough advancements in the foreseeable future. This review delineates the advancements and challenges faced in vaccines and therapeutic agents targeting RSV. It aims to provide insights that will guide the development of effective preventive and control measures for RSV.

The respiratory syncytial virus vaccine and monoclonal antibody landscape: the road to global access

Respiratory syncytial virus (RSV) is the second most common pathogen causing infant mortality. Additionally, RSV is a major cause of morbidity and mortality in older adults (age ≥60 years) similar to influenza. A protein-based maternal vaccine and monoclonal antibody (mAb) are now market-approved to protect infants, while an mRNA and two protein-based vaccines are approved for older adults. First-year experience protecting infants with nirsevimab in high-income countries shows a major public health benefit. It is expected that the RSV vaccine landscape will continue to develop in the coming years to protect all people globally. The vaccine and mAb landscape remain active with 30 candidates in clinical development using four approaches: protein-based, live-attenuated and chimeric vector, mRNA, and mAbs. Candidates in late-phase trials aim to protect young infants using mAbs, older infants and toddlers with live-attenuated vaccines, and children and adults using protein-based and mRNA vaccines. This Review provides an overview of RSV vaccines highlighting different target populations, antigens, and trial results. As RSV vaccines have not yet reached low-income and middle-income countries, we outline urgent next steps to minimise the vaccine delay.

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.

Liquid Phase Exfoliation of Protein Parent Crystals into Nanosheets and Fibrils Based on Orthogonal Supramolecular Interactions

Proteins are attractive building blocks for fabricating diverse and precise nanomaterials. However, the facile fabrication of multidimensional artificial assemblies is highly challenging. Here, inspired by the large-scale production technique of inorganic nanomaterials, we demonstrate the application of liquid phase exfoliation (LPE) on native protein ConA by the design of synthetic ligands. These ligands provide distinct in-plane and out-of-plane supramolecular interactions, allowing the generation of multidimensional architectures based on the same protein by dissociating a single interaction in solution, including 3D porous protein crystals, 2D sizable nanosheets, and 1D fibrils. Importantly, the exfoliated 2D sheets were dozens of times larger than the self-assembled nanosheets, resulting in a dramatic enhancement of the intrinsic bioactivity of the building blocks by receptor clustering and less endocytosis. These findings enable the successful application of LPE on biomacromolecules and open up an alternative avenue to generate advanced multidimensional nanomaterials, without the need for complex protein design and careful adjustment of self-assembly conditions.

Rational design of uncleaved prefusion-closed trimer vaccines for human respiratory syncytial virus and metapneumovirus

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) cause human respiratory diseases and are major targets for vaccine development. In this study, we design uncleaved prefusion-closed (UFC) trimers for the fusion protein (F) of both viruses by examining mutations critical to F metastability. For RSV, we assess four previous prefusion F designs, including the first and second generations of DS-Cav1, SC-TM, and 847A. We then identify key mutations that can maintain prefusion F in a native-like, closed trimeric form (up to 76%) without introducing any interprotomer disulfide bond. For hMPV, we develop a stable UFC trimer with a truncated F2-F1 linkage and an interprotomer disulfide bond. Dozens of UFC constructs are characterized by negative-stain electron microscopy (nsEM), x-ray crystallography (11 RSV-F structures and one hMPV-F structure), and antigenic profiling. Using an optimized RSV-F UFC trimer as bait, we identify three potent RSV neutralizing antibodies (NAbs) from a phage-displayed human antibody library, with a public NAb lineage targeting sites Ø and V and two cross-pneumovirus NAbs recognizing site III. In mouse immunization, rationally designed RSV-F and hMPV-F UFC trimers induce robust antibody responses with high neutralizing titers. Our study provides a foundation for future prefusion F-based RSV and hMPV vaccine development.

Nanocarriers for intracellular delivery of proteins in biomedical applications: strategies and recent advances

Protein drugs are of great importance in maintaining the normal functioning of living organisms. Indeed, they have been instrumental in combating tumors and genetic diseases for decades. Among these pharmaceutical agents, those that target intracellular components necessitate the use of therapeutic proteins to exert their effects within the targeted cells. However, the use of protein drugs is limited by their short half-life and potential adverse effects in the physiological environment. The advent of nanoparticles offers a promising avenue for prolonging the half-life of protein drugs. This is achieved by encapsulating proteins, thereby safeguarding their biological activity and ensuring precise delivery into cells. This nanomaterial-based intracellular protein drug delivery system mitigates the rapid hydrolysis and unwarranted diffusion of proteins, thereby minimizing potential side effects and circumventing the limitations inherent in traditional techniques like electroporation. This review examines established protein drug delivery systems, including those based on polymers, liposomes, and protein nanoparticles. We delve into the operational principles and transport mechanisms of nanocarriers, discussing the various considerations essential for designing cutting-edge delivery platforms. Additionally, we investigate innovative designs and applications of traditional cytosolic protein delivery systems in medical research and clinical practice, particularly in areas like tumor treatment, gene editing and fluorescence imaging. This review sheds light on the current restrictions of protein delivery systems and anticipates future research avenues, aiming to foster the continued advancement in this field.

Evaluation of adenoviral vector Ad19a encoding RSV-F as novel vaccine against respiratory syncytial virus

Respiratory syncytial virus (RSV) is the leading cause of severe lower respiratory tract infections in infants and toddlers. Since natural infections do not induce persistent immunity, there is the need of vaccines providing long-term protection. Here, we evaluated a new adenoviral vector (rAd) vaccine based on the rare serotype rAd19a and compared the immunogenicity and efficacy to the highly immunogenic rAd5. Given as an intranasal boost in DNA primed mice, both vectors encoding the F protein provided efficient protection against a subsequent RSV infection. However, intramuscular immunization with rAd19a vectors provoked vaccine-enhanced disease after RSV infection compared to non-vaccinated animals. While mucosal IgA antibodies and tissue-resident memory T-cells in intranasally vaccinated mice rapidly control RSV replication, a strong anamnestic systemic T-cell response in absence of local immunity might be the reason for immune-mediated enhanced disease. Our study highlighted the potential benefits of developing effective mucosal against respiratory pathogens.

Modular Nano-Antigen Display Platform for Pigs Induces Potent Immune Responses

Multivalent presentation of antigens using nanoparticles (NPs) as a platform is an effective strategy to enhance the immunogenicity of subunit vaccines and thus induce a high level of organismal immune response. Our previous results showed that pre-existing porcine circovirus type 2 (PCV2) antibodies could increase the antibody levels of nanoparticle vaccines carried in PCV2 VLPs. Here, we have established a generalized nanoantigen display platform, Cap-Cat virus-like particles (VLPs). By combining PCV2 VLPs with the modular linker element SpyTag003/SpyCatcher003 system, four porcine-derived viral protective antigens with different sizes and multimeric structures: the PRRSV B-cell epitope, the PEDV COE monomer, the CSFV E2 dimer, and the SIV HA trimer were efficiently demonstrated to elicit a strong immune response in mice. Crucially, the modification of antigens by the Cap-Cat VLPs platform enhanced the Th2 response and improved the Th1 response. The use of the platform demonstrates that HA antigen protects against lethal attacks by influenza viruses and reduces viral load in the lungs. We have demonstrated that the Cap-Cat VLPs platform demonstrates that antigens enhance the immune response by improving the processes of DC uptake, transport, lymph node (LN) localization, and immune cell activation. This "plug-and-display" assembly strategy facilitates the use of the Cap-Cat VLPs nanoantigen display platform for more applications and thus facilitates the development of more efficient, general-purpose porcine subunit vaccines.

An Integrated Signaling Threshold Initiates IgG Response toward Virus-like Immunogens

Class-switched neutralizing Ab (nAb) production is rapidly induced upon many viral infections. However, due to the presence of multiple components in virions, the precise biochemical and biophysical signals from viral infections that initiate nAb responses remain inadequately defined. Using a reductionist system of synthetic virus-like structures, in this study, we show that a foreign protein on a virion-sized liposome can serve as a stand-alone danger signal to initiate class-switched nAb responses without T cell help or TLR but requires CD19. Introduction of internal nucleic acids (iNAs) obviates the need for CD19, lowers the epitope density (ED) required to elicit the Ab response, and transforms these structures into highly potent immunogens that rival conventional virus-like particles in their ability to elicit strong Ag-specific IgG. As early as day 5 after immunization, structures harboring iNAs and decorated with just a few molecules of surface Ag at doses as low as 100 ng induced all IgG subclasses of Ab in mice and reproduced the IgG2a/2c restriction that is long observed in live viral infections. These findings reveal a shared mechanism for the nAb response in mice. High ED is capable but not necessary for driving Ab secretion. Instead, even a few molecules of surface Ag, when combined with nucleic acids within these structures, can trigger strong IgG production. As a result, the signaling threshold for induction of IgG in individual B cells is set by dual signals originating from both ED on the surface and the presence of iNAs within viral particulate immunogens.

Chiral Intranasal Nanovaccines as Antivirals for Respiratory Syncytial Virus

This study aimed to develop an intranasal nanovaccine by combining chiral nanoparticles with the RSV pre-fusion protein (RSV protein) to create L-nanovaccine (L-Vac). The results showed that L-NPs increased antigen attachment in the nasal cavity by 3.83 times and prolonged its retention time to 72 h. In vivo experimental data demonstrated that the intranasal immunization with L-Vac induced a 4.86-fold increase in secretory immunoglobulin A (sIgA) secretion in the upper respiratory tract, a 1.85-fold increase in the lower respiratory tract, and a 20.61-fold increase in RSV-specific immunoglobin G (IgG) titer levels in serum, compared with the commercial Alum Vac, while the neutralizing activity against the RSV authentic virus is 1.66-fold higher. The mechanistic investigation revealed that L-Vac activated the tumor necrosis factor (TNF) signaling pathway in nasal epithelial cells (NECs), in turn increasing the expression levels of interleukin-6 (IL-6) and C-C motif chemokine ligand 20 (CCL20) by 1.67-fold and 3.46-fold, respectively, through the downstream nuclear factor kappa-B (NF-κB) signaling pathway. Meanwhile, CCL20 recruited dendritic cells (DCs) and L-Vac activated the Toll-like receptor signaling pathway in DCs, promoting IL-6 expression and DCs maturation, and boosted sIgA production and T-cell responses. The findings suggested that L- Vac may serve as a candidate for the development of intranasal medicine against various types of respiratory infections.

Immunity and Protective Efficacy of a Plant-Based Tobacco Mosaic Virus-like Nanoparticle Vaccine against Influenza a Virus in Mice

BACKGROUND

The rapid production of influenza vaccines is crucial to meet increasing pandemic response demands. Here, we developed plant-made vaccines comprising centralized consensus influenza hemagglutinin (HA-con) proteins (H1 and H3 subtypes) conjugated to a modified plant virus, tobacco mosaic virus (TMV) nanoparticle (TMV-HA-con).

METHODS

We compared immune responses and protective efficacy against historical H1 or H3 influenza A virus infections among TMV-HA-con, HA-con protein combined with AddaVax™ adjuvant, and whole-inactivated virus vaccine (Fluzone®).

RESULTS

Immunogenicity studies demonstrated robust IgG, IgM, and IgA responses in the TMV-HA-con and HA-con protein vaccinated groups, with relatively low induction of interferon (IFN)-γ+ T-cell responses across all vaccinated groups. The TMV-HA-con and HA-con protein groups displayed partial protection (100% and 80% survival) with minimal weight loss following challenge with two H1N1 strains. The HA-con protein group exhibited 80% and 100% survival against two H3 strains, whereas the TMV-HA-con groups showed reduced protection (20% survival). The Fluzone® group conferred 20-100% survival against two H1N1 strains and one H3N1 strain, but did not protect against H3N2 infection.

CONCLUSIONS

Our findings indicate that TMV-HA and HA-con protein vaccines with adjuvant induce protective immune responses against influenza A virus infections. Furthermore, our results underscore the potential of plant-based production using TMV-like nanoparticles for developing influenza A virus candidate vaccines.

Design and immunogenicity of an HIV-1 clade C pediatric envelope glycoprotein stabilized by multiple platforms

Various design platforms are available to stabilize soluble HIV-1 envelope (Env) trimers, which can be used as antigenic baits and vaccine antigens. However, stabilizing HIV-1 clade C trimers can be challenging. Here, we stabilized an HIV-1 clade C trimer based on an Env isolated from a pediatric elite-neutralizer (AIIMS_329) using multiple platforms, including SOSIP.v8.2, ferritin nanoparticles (NP) and an I53-50 two-component NP, followed by characterization of their biophysical, antigenic, and immunogenic properties. The stabilized 329 Envs showed binding affinity to trimer-specific HIV-1 broadly neutralizing antibodies (bnAbs), with negligible binding to non-neutralizing antibodies (non-nAbs). Negative-stain electron microscopy (nsEM) confirmed the native-like conformation of the Envs. Multimerization of 329 SOSIP.v8.2 on ferritin and two-component I53-50 NPs improved the overall affinity to HIV-1 bnAbs and immunogenicity in rabbits. These stabilized HIV-1 clade C 329 Envs demonstrate the potential to be used as antigenic baits and as components of multivalent vaccine candidates in future.

Glycoprotein E-Displaying Nanoparticles Induce Robust Neutralizing Antibodies and T-Cell Response against Varicella Zoster Virus

The Varicella zoster virus (VZV), responsible for both varicella (chickenpox) and herpes zoster (shingles), presents significant global health challenges. While primary VZV infection primarily affects children, leading to chickenpox, reactivation in later life can result in herpes zoster and associated post-herpetic neuralgia, among other complications. Vaccination remains the most effective strategy for VZV prevention, with current vaccines largely based on the attenuated vOka strains. Although these vaccines are generally effective, they can induce varicella-like rashes and have sparked concerns regarding cell virulence. As a safer alternative, subunit vaccines circumvent these issues. In this study, we developed a nanoparticle-based vaccine displaying the glycoprotein E (gE) on ferritin particles using the SpyCatcher/SpyTag system, termed FR-gE. This FR-gE nanoparticle antigen elicited substantial gE-specific binding and VZV-neutralizing antibody responses in BALB/c and C57BL/6 mice-responses that were up to 3.2-fold greater than those elicited by the subunit gE while formulated with FH002C, aluminum hydroxide, or a liposome-based XUA01 adjuvant. Antibody subclass analysis revealed that FR-gE produced comparable levels of IgG1 and significantly higher levels of IgG2a compared to subunit gE, indicating a Th1-biased immune response. Notably, XUA01-adjuvanted FR-gE induced a significant increase in neutralizing antibody response compared to the live attenuated varicella vaccine and recombinant vaccine, Shingrix. Furthermore, ELISPOT assays demonstrated that immunization with FR-gE/XUA01 generated IFN-γ and IL-2 levels comparable to those induced by Shingrix. These findings underscore the potential of FR-gE as a promising immunogen for the development of varicella and herpes zoster vaccines.

Global progress in clinical research on human respiratory syncytial virus vaccines

Human respiratory syncytial virus (hRSV) not only affects newborns but also older adults, contributing to a substantial worldwide burden of disease. However, only three approved hRSV vaccines remain commercially available to date. The development of a safe, practical and broad-spectrum vaccine suitable for all age groups remains extremely challenging. Using five different approaches-live-attenuated, recombinant-vector, subunit, particle-based, and mRNA-nearly 30 hRSV vaccine candidates are currently conducting clinical trials worldwide; moreover, > 30 vaccines are under preclinical evaluation. This review presents a comprehensive overview of these hRSV vaccines along with prospects for the development of infectious disease vaccines in the post-COVID-19 pandemic era.

Novel Administration Routes, Delivery Vectors, and Application of Vaccines Based on Biotechnologies: A Review

Traditional vaccines can be classified into inactivated vaccines, live attenuated vaccines, and subunit vaccines given orally or via intramuscular (IM) injection or subcutaneous (SC) injection for the prevention of infectious diseases. Recently, recombinant protein vaccines, DNA vaccines, mRNA vaccines, and multiple/alternative administering route vaccines (e.g., microneedle or inhalation) have been developed to make vaccines more secure, effective, tolerable, and universal for the public. In addition to preventing infectious diseases, novel vaccines have currently been developed or are being developed to prevent or cure noninfectious diseases, including cancer. These vaccine platforms have been developed using various biotechnologies such as viral vectors, nanoparticles, mRNA, recombination DNA, subunit, novel adjuvants, and other vaccine delivery systems. In this review, we will explore the development of novel vaccines applying biotechnologies, such as vaccines based on novel administration routes, vaccines based on novel vectors, including viruses and nanoparticles, vaccines applied for cancer prevention, and therapeutic vaccines.

Reversibly photoswitchable protein assemblies with collagen affinity for in vivo photoacoustic imaging of tumors

Recent advancements in photoacoustic (PA) imaging have leveraged reversibly photoswitchable chromophores, known for their dual absorbance states, to enhance imaging sensitivity through differential techniques. Yet, their deployment in tumor imaging has faced obstacles in achieving targeted delivery with high efficiency and specificity. Addressing this challenge, we introduce innovative protein assemblies, DrBphP-CBD, by genetically fusing a photosensory module from Deinococcus radiodurans bacterial phytochrome (DrBphP) with a collagen-binding domain (CBD). These protein assemblies form sub-100-nanometer structures composed of 24 DrBphP dimers and 12 CBD trimers, presenting 24 protein subunits. Their affinity for collagens, combined with impressive photoswitching contrast, markedly improves PA imaging precision. In various tumor models, intravenous administration of DrBphP-CBD has demonstrated enhanced tumor targeting and retention, augmenting contrast in PA imaging by minimizing background noise. This strategy underscores the clinical potential of DrBphP-CBD as PA contrast agents, propelling photoswitchable chromoproteins to the forefront of precise cancer diagnosis.

Saponin nanoparticle adjuvants incorporating Toll-like receptor agonists drive distinct immune signatures and potent vaccine responses

Over the past few decades, the development of potent and safe immune-activating adjuvant technologies has become the heart of intensive research in the constant fight against highly mutative and immune evasive viruses such as influenza, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and human immunodeficiency virus (HIV). Herein, we developed a highly modular saponin-based nanoparticle platform incorporating Toll-like receptor agonists (TLRas) including TLR1/2a, TLR4a, and TLR7/8a adjuvants and their mixtures. These various TLRa-saponin nanoparticle adjuvant constructs induce unique acute cytokine and immune-signaling profiles, leading to specific T helper responses that could be of interest depending on the target disease for prevention. In a murine vaccine study, the adjuvants greatly improved the potency, durability, breadth, and neutralization of both COVID-19 and HIV vaccine candidates, suggesting the potential broad application of these adjuvant constructs to a range of different antigens. Overall, this work demonstrates a modular TLRa-SNP adjuvant platform that could improve the design of vaccines and affect modern vaccine development.

Mechanical control of antigen detection and discrimination by T and B cell receptors

The adaptive immune response is orchestrated by just two cell types, T cells and B cells. Both cells possess the remarkable ability to recognize virtually any antigen through their respective antigen receptors-the T cell receptor (TCR) and B cell receptor (BCR). Despite extensive investigations into the biochemical signaling events triggered by antigen recognition in these cells, our ability to predict or control the outcome of T and B cell activation remains elusive. This challenge is compounded by the sensitivity of T and B cells to the biophysical properties of antigens and the cells presenting them-a phenomenon we are just beginning to understand. Recent insights underscore the central role of mechanical forces in this process, governing the conformation, signaling activity, and spatial organization of TCRs and BCRs within the cell membrane, ultimately eliciting distinct cellular responses. Traditionally, T cells and B cells have been studied independently, with researchers working in parallel to decipher the mechanisms of activation. While these investigations have unveiled many overlaps in how these cell types sense and respond to antigens, notable differences exist. To fully grasp their biology and harness it for therapeutic purposes, these distinctions must be considered. This review compares and contrasts the TCR and BCR, placing emphasis on the role of mechanical force in regulating the activity of both receptors to shape cellular and humoral adaptive immune responses.

Duck CD40L as an adjuvant enhances systemic immune responses of avian flavivirus DNA vaccine

Under the dual pressure of emerging zoonoses and the difficulty in eliminating conventional zoonoses, the strategic management of bird diseases through vaccination represents a highly efficacious approach to disrupting the transmission of zoonotic pathogens to humans. Immunization with a DNA vaccine yielded limited protection against avian pathogen infection. To improve its immunogenicity, the extracellular domain of duck-derived CD40L (designated as dusCD40L) was employed as a bio-adjuvant. Our findings unequivocally established the evolutionary conservation of dusCD40L across avian species. Notably, dusCD40L exhibited a compelling capacity to elicit robust immune responses from both B and T lymphocytes. Furthermore, when employed as an adjuvant, dusCD40L demonstrated a remarkable capacity to significantly augment the titers of neutralizing antibodies and the production of IFNγ elicited by a DNA vaccine encoding the prM-E region of an avian flavivirus, namely, the Tembusu virus (TMUV). Moreover, dusCD40L could strengthen virus clearance of the prM-E DNA vaccine in ducks post-TMUV challenge. This research study presents a highly effective adjuvant for advancing the development of DNA vaccines targeting TMUV in avian hosts. Additionally, it underscores the pivotal role of duCD40L as a potent adjuvant in the context of vaccines designed to combat zoonotic infections in avian species.

Opportunities and challenges in design and optimization of protein function

The field of protein design has made remarkable progress over the past decade. Historically, the low reliability of purely structure-based design methods limited their application, but recent strategies that combine structure-based and sequence-based calculations, as well as machine learning tools, have dramatically improved protein engineering and design. In this Review, we discuss how these methods have enabled the design of increasingly complex structures and therapeutically relevant activities. Additionally, protein optimization methods have improved the stability and activity of complex eukaryotic proteins. Thanks to their increased reliability, computational design methods have been applied to improve therapeutics and enzymes for green chemistry and have generated vaccine antigens, antivirals and drug-delivery nano-vehicles. Moreover, the high success of design methods reflects an increased understanding of basic rules that govern the relationships among protein sequence, structure and function. However, de novo design is still limited mostly to α-helix bundles, restricting its potential to generate sophisticated enzymes and diverse protein and small-molecule binders. Designing complex protein structures is a challenging but necessary next step if we are to realize our objective of generating new-to-nature activities.

Self-Assembly of Polymers and Their Applications in the Fields of Biomedicine and Materials

Polymer self-assembly can prepare various shapes and sizes of pores, making it widely used. The complexity and diversity of biomolecules make them a unique class of building blocks for precise assembly. They are particularly suitable for the new generation of biomaterials integrated with life systems as they possess inherent characteristics such as accurate identification, self-organization, and adaptability. Therefore, many excellent methods developed have led to various practical results. At the same time, the development of advanced science and technology has also expanded the application scope of self-assembly of synthetic polymers. By utilizing this technology, materials with unique shapes and properties can be prepared and applied in the field of tissue engineering. Nanomaterials with transparent and conductive properties can be prepared and applied in fields such as electronic displays and smart glass. Multi-dimensional, controllable, and multi-level self-assembly between nanostructures has been achieved through quantitative control of polymer dosage and combination, chemical modification, and composite methods. Here, we list the classic applications of natural- and artificially synthesized polymer self-assembly in the fields of biomedicine and materials, introduce the cutting-edge technologies involved in these applications, and discuss in-depth the advantages, disadvantages, and future development directions of each type of polymer self-assembly.

A nanoparticle vaccine displaying varicella-zoster virus gE antigen induces a superior cellular immune response than a licensed vaccine in mice and non-human primates

Herpes zoster (HZ), also known as shingles, remains a significant global health issue and most commonly seen in elderly individuals with an early exposure history to varicella-zoster virus (VZV). Currently, the licensed vaccine Shingrix, which comprises a recombinant VZV glycoprotein E (gE) formulated with a potent adjuvant AS01B, is the most effective shingles vaccine on the market. However, undesired reactogenicity and increasing global demand causing vaccine shortage, prompting the development of novel shingles vaccines. Here, we developed novel vaccine candidates utilising multiple nanoparticle (NP) platforms to display the recombinant gE antigen, formulated in an MF59-biosimilar adjuvant. In naïve mice, all tested NP vaccines induced higher humoral and cellular immune responses than Shingrix, among which, the gEM candidate induced the highest cellular response. In live attenuated VZV (VZV LAV)-primed mouse and rhesus macaque models, the gEM candidate elicited superior cell-mediated immunity (CMI) over Shingrix. Collectively, we demonstrated that NP technology remains a suitable tool for developing shingles vaccine, and the reported gEM construct is a highly promising candidate in the next-generation shingles vaccine development.

Magnetically Induced Thermal Effects on Tobacco Mosaic Virus-Based Nanocomposites for a Programmed Disassembly of Protein Cages

Protein cages are promising tools for the controlled delivery of therapeutics and imaging agents when endowed with programmable disassembly strategies. Here, we produced hybrid nanocomposites made of tobacco mosaic virus (TMV) and magnetic iron oxide nanoparticles (IONPs), designed to disrupt the viral protein cages using magnetically induced release of heat. We studied the effects of this magnetic hyperthermia on the programmable viral protein capsid disassembly using (1) elongated nanocomposites of TMV coated heterogeneously with magnetic iron oxide nanoparticles (TMV@IONPs) and (2) spherical nanocomposites of polystyrene (PS) on which we deposited presynthesized IONPs and TMV via layer-by-layer self-assembly (PS@IONPs/TMV). Notably, we found that the extent of the disassembly of the protein cages is contingent upon the specific absorption rate (SAR) of the magnetic nanoparticles, that is, the heating efficiency, and the relative position of the protein cage within the nanocomposite concerning the heating sources. This implies that the spatial arrangement of components within the hybrid nanostructure has a significant impact on the disassembly process. Understanding and optimizing this relationship will contribute to the critical spatiotemporal control for targeted drug and gene delivery using protein cages.

The recent advancements in protein nanoparticles for immunotherapy

In recent years, the advancement of nanoparticle-based immunotherapy has introduced an innovative strategy for combatting diseases. Compared with other types of nanoparticles, protein nanoparticles have obtained substantial attention owing to their remarkable biocompatibility, biodegradability, ease of modification, and finely designed spatial structures. Nature provides several protein nanoparticle platforms, including viral capsids, ferritin, and albumin, which hold significant potential for disease treatment. These naturally occurring protein nanoparticles not only serve as effective drug delivery platforms but also augment antigen delivery and targeting capabilities through techniques like genetic modification and covalent conjugation. Motivated by nature's originality and driven by progress in computational methodologies, scientists have crafted numerous protein nanoparticles with intricate assembly structures, showing significant potential in the development of multivalent vaccines. Consequently, both naturally occurring and de novo designed protein nanoparticles are anticipated to enhance the effectiveness of immunotherapy. This review consolidates the advancements in protein nanoparticles for immunotherapy across diseases including cancer and other diseases like influenza, pneumonia, and hepatitis.

Advances in virus-like particle-based SARS-CoV-2 vaccines

The Coronavirus Disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has incurred devastating human and economic losses. Vaccination remains the most effective approach for controlling the COVID-19 pandemic. Nonetheless, the sustained evolution of SARS-CoV-2 variants has provoked concerns among the scientific community regarding the development of next-generation COVID-19 vaccines. Among these, given their safety, immunogenicity, and flexibility to display varied and native epitopes, virus-like particle (VLP)-based vaccines represent one of the most promising next-generation vaccines. In this review, we summarize the advantages and characteristics of VLP platforms, strategies for antigen display, and current clinical trial progress of SARS-CoV-2 vaccines based on VLP platforms. Importantly, the experience and lessons learned from the development of SARS-CoV-2 VLP vaccines provide insights into the development of strategies based on VLP vaccines to prevent future coronavirus pandemics and other epidemics.

Capsid virus-like particle display improves recombinant influenza neuraminidase antigen stability and immunogenicity in mice

Supplementing influenza vaccines with additional protective antigens such as neuraminidase (NA) is a promising strategy for increasing the breadth of the immune response. Here, we improved the immunogenicity and stability of secreted recombinant NA (rNA) tetramers by covalently conjugating them onto the surface of AP205 capsid virus-like particles (cVLPs) using a Tag/Catcher ligation system. cVLP display increased the induction of IgG2a subclass anti-NA antibodies, which exhibited cross-reactivity with an antigenically distant homologous NA. It also reduced the single dose rNA amounts needed for protection against viral challenge in mice, demonstrating a dose-sparing effect. Moreover, effective cVLP-display was achieved across different NA subtypes, even when the conjugation was performed shortly before administration. Notably, the rNA-cVLP immunogenicity was retained upon mixing or co-administering with commercial vaccines. These results highlight the potential of this approach for bolstering the protective immune responses elicited by influenza vaccines.

Protein Nanoparticles as Vaccine Platforms for Human and Zoonotic Viruses

Vaccines are one of the most effective medical interventions, playing a pivotal role in treating infectious diseases. Although traditional vaccines comprise killed, inactivated, or live-attenuated pathogens that have resulted in protective immune responses, the negative consequences of their administration have been well appreciated. Modern vaccines have evolved to contain purified antigenic subunits, epitopes, or antigen-encoding mRNAs, rendering them relatively safe. However, reduced humoral and cellular responses pose major challenges to these subunit vaccines. Protein nanoparticle (PNP)-based vaccines have garnered substantial interest in recent years for their ability to present a repetitive array of antigens for improving immunogenicity and enhancing protective responses. Discovery and characterisation of naturally occurring PNPs from various living organisms such as bacteria, archaea, viruses, insects, and eukaryotes, as well as computationally designed structures and approaches to link antigens to the PNPs, have paved the way for unprecedented advances in the field of vaccine technology. In this review, we focus on some of the widely used naturally occurring and optimally designed PNPs for their suitability as promising vaccine platforms for displaying native-like antigens from human viral pathogens for protective immune responses. Such platforms hold great promise in combating emerging and re-emerging infectious viral diseases and enhancing vaccine efficacy and safety.

A suite of designed protein cages using machine learning and protein fragment-based protocols

Designed protein cages and related materials provide unique opportunities for applications in biotechnology and medicine, but their creation remains challenging. Here, we apply computational approaches to design a suite of tetrahedrally symmetric, self-assembling protein cages. For the generation of docked conformations, we emphasize a protein fragment-based approach, while for sequence design of the de novo interface, a comparison of knowledge-based and machine learning protocols highlights the power and increased experimental success achieved using ProteinMPNN. An analysis of design outcomes provides insights for improving interface design protocols, including prioritizing fragment-based motifs, balancing interface hydrophobicity and polarity, and identifying preferred polar contact patterns. In all, we report five structures for seven protein cages, along with two structures of intermediate assemblies, with the highest resolution reaching 2.0 Å using cryo-EM. This set of designed cages adds substantially to the body of available protein nanoparticles, and to methodologies for their creation.

Adjuvants for cancer mRNA vaccines in the era of nanotechnology: strategies, applications, and future directions

Research into mRNA vaccines is advancing rapidly, with proven efficacy against coronavirus disease 2019 and promising therapeutic potential against a variety of solid tumors. Adjuvants, critical components of mRNA vaccines, significantly enhance vaccine effectiveness and are integral to numerous mRNA vaccine formulations. However, the development and selection of adjuvant platforms are still in their nascent stages, and the mechanisms of many adjuvants remain poorly understood. Additionally, the immunostimulatory capabilities of certain novel drug delivery systems (DDS) challenge the traditional definition of adjuvants, suggesting that a revision of this concept is necessary. This review offers a comprehensive exploration of the mechanisms and applications of adjuvants and self-adjuvant DDS. It thoroughly addresses existing issues mentioned above and details three main challenges of immune-related adverse event, unclear mechanisms, and unsatisfactory outcomes in old age group in the design and practical application of cancer mRNA vaccine adjuvants. Ultimately, this review proposes three optimization strategies which consists of exploring the mechanisms of adjuvant, optimizing DDS, and improving route of administration to improve effectiveness and application of adjuvants and self-adjuvant DDS.

Rapid production of COVID-19 subunit vaccine candidates and their immunogenicity evaluation in pigs

The emergence of various variants of concern (VOCs) necessitates the development of more efficient vaccines for COVID-19. In this study, we established a rapid and robust production platform for a novel subunit vaccine candidate based on eukaryotic HEK-293 T cells. The immunogenicity of the vaccine candidate was evaluated in pigs. The results demonstrated that the pseudovirus neutralizing antibody (pNAb) titers reached 7751 and 306 for the SARS-CoV-2 Delta and Omicron variants, respectively, after the first boost. Subsequently, pNAb titers further increased to 10,201 and 1350, respectively, after the second boost. Additionally, ELISPOT analysis revealed a robust T-cell response characterized by IFN-γ (171 SFCs/106 cells) and IL-2 (101 SFCs/106 cells) production. Our study demonstrates that a vaccine candidate based on the Delta variant spike protein may provide strong and broad protection against the prototype SARS-CoV-2 and VOCs. Moreover, the strategy for the efficient and stable expression of recombinant proteins utilizing HEK-293 T cells can be employed as a universal platform for future vaccine development.

Growing Glycans in Rosetta: Accurate de novo glycan modeling, density fitting, and rational sequon design

Carbohydrates and glycoproteins modulate key biological functions. However, experimental structure determination of sugar polymers is notoriously difficult. Computational approaches can aid in carbohydrate structure prediction, structure determination, and design. In this work, we developed a glycan-modeling algorithm, GlycanTreeModeler, that computationally builds glycans layer-by-layer, using adaptive kernel density estimates (KDE) of common glycan conformations derived from data in the Protein Data Bank (PDB) and from quantum mechanics (QM) calculations. GlycanTreeModeler was benchmarked on a test set of glycan structures of varying lengths, or "trees". Structures predicted by GlycanTreeModeler agreed with native structures at high accuracy for both de novo modeling and experimental density-guided building. We employed these tools to design de novo glycan trees into a protein nanoparticle vaccine to shield regions of the scaffold from antibody recognition, and experimentally verified shielding. This work will inform glycoprotein model prediction, glycan masking, and further aid computational methods in experimental structure determination and refinement.

Nanoparticle display of neuraminidase elicits enhanced antibody responses and protection against influenza A virus challenge

Current Influenza virus vaccines primarily induce antibody responses against variable epitopes in hemagglutinin (HA), necessitating frequent updates. However, antibodies against neuraminidase (NA) can also confer protection against influenza, making NA an attractive target for the development of novel vaccines. In this study, we aimed to enhance the immunogenicity of recombinant NA antigens by presenting them multivalently on a nanoparticle carrier. Soluble tetrameric NA antigens of the N1 and N2 subtypes, confirmed to be correctly folded by cryo-electron microscopy structural analysis, were conjugated to Mi3 self-assembling protein nanoparticles using the SpyTag-SpyCatcher system. Immunization of mice with NA-Mi3 nanoparticles induced higher titers of NA-binding and -inhibiting antibodies and improved protection against a lethal challenge compared to unconjugated NA. Additionally, we explored the co-presentation of N1 and N2 antigens on the same Mi3 particles to create a mosaic vaccine candidate. These mosaic nanoparticles elicited antibody titers that were similar or superior to the homotypic nanoparticles and effectively protected against H1N1 and H3N2 challenge viruses. The NA-Mi3 nanoparticles represent a promising vaccine candidate that could complement HA-directed approaches for enhanced potency and broadened protection against influenza A virus.

VLPs generated by the fusion of RSV-F or hMPV-F glycoprotein to HIV-Gag show improved immunogenicity and neutralizing response in mice

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) vaccines have been long overdue. Structure-based vaccine design created a new momentum in the last decade, and the first RSV vaccines have finally been approved in older adults and pregnant individuals. These vaccines are based on recombinant stabilized pre-fusion F glycoproteins administered as soluble proteins. Multimeric antigenic display could markedly improve immunogenicity and should be evaluated in the next generations of vaccines. Here we tested a new virus like particles-based vaccine platform which utilizes the direct fusion of an immunogen of interest to the structural human immunodeficient virus (HIV) protein Gag to increase its surface density and immunogenicity. We compared, in mice, the immunogenicity of RSV-F or hMPV-F based immunogens delivered either as soluble proteins or displayed on the surface of our VLPs. VLP associated F-proteins showed better immunogenicity and induced superior neutralizing responses. Moreover, when combining both VLP associated and soluble immunogens in a heterologous regimen, VLP-associated immunogens provided added benefits when administered as the prime immunization.

Point mutation in a virus-like capsid drives symmetry reduction to form tetrahedral cages

Protein capsids are a widespread form of compartmentalization in nature. Icosahedral symmetry is ubiquitous in capsids derived from spherical viruses, as this geometry maximizes the internal volume that can be enclosed within. Despite the strong preference for icosahedral symmetry, we show that simple point mutations in a virus-like capsid can drive the assembly of unique symmetry-reduced structures. Starting with the encapsulin from Myxococcus xanthus, a 180-mer bacterial capsid that adopts the well-studied viral HK97 fold, we use mass photometry and native charge detection mass spectrometry to identify a triple histidine point mutant that forms smaller dimorphic assemblies. Using cryoelectron microscopy, we determine the structures of a precedented 60-mer icosahedral assembly and an unexpected 36-mer tetrahedron that features significant geometric rearrangements around a new interaction surface between capsid protomers. We subsequently find that the tetrahedral assembly can be generated by triple-point mutation to various amino acids and that even a single histidine point mutation is sufficient to form tetrahedra. These findings represent a unique example of tetrahedral geometry when surveying all characterized encapsulins, HK97-like capsids, or indeed any virus-derived capsids reported in the Protein Data Bank, revealing the surprising plasticity of capsid self-assembly that can be accessed through minimal changes in the protein sequence.

Melatonin suppresses TLR4-mediated RSV infection in the central nervous cells by inhibiting NLRP3 inflammasome formation and autophagy

Respiratory syncytial virus (RSV) infects neuronal cells in the central nervous system (CNS), resulting in neurological symptoms. In the present study, we intended to explore the mechanism of RSV infection-induced neuroinflammatory injury from the perspective of the immune response and sought to identify effective protective measures against the injury. The findings showed that toll-like receptor 4 (TLR4) was activated after RSV infection in human neuronal SY5Y cells. Furthermore, TLR4 activation induced autophagy and apoptosis in neuronal cells, promoted the formation of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, and increased the secretion of downstream inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-18 (IL-18) and tumour necrosis factor-α (TNF-α). Interestingly, blockade of TLR4 or treatment with exogenous melatonin significantly suppressed TLR4 activation as well as TLR4-mediated apoptosis, autophagy and immune responses. Therefore, we infer that melatonin may act on the TLR4 to ameliorate RSV-induced neuronal injury, which provides a new therapeutic target for RSV infection.

Fusion then fission: splitting and reassembly of an artificial fusion-protein nanocage

A split-protein system is a simple approach to introduce new termini which are useful as modification sites in protein engineering, but has been adapted mainly for monomeric proteins. Here we demonstrate the design of split subunits of the 60-mer artificial fusion-protein nanocage TIP60. The subunit fragments successfully reformed the cage structure in the same manner as prior to splitting. One of the newly introduced terminals at the interior surface can be modified using a tag peptide and green fluorescent protein. Therefore, the termini could serve as a versatile modification site for incorporating a wide variety of functional peptides and proteins.

Biomaterial engineering strategies for B cell immunity modulations

B cell immunity has a penetrating effect on human health and diseases. Therapeutics aiming to modulate B cell immunity have achieved remarkable success in combating infections, autoimmunity, and malignancies. However, current treatments still face significant limitations in generating effective long-lasting therapeutic B cell responses for many conditions. As the understanding of B cell biology has deepened in recent years, clearer regulation networks for B cell differentiation and antibody production have emerged, presenting opportunities to overcome current difficulties and realize the full therapeutic potential of B cell immunity. Biomaterial platforms have been developed to leverage these emerging concepts to augment therapeutic humoral immunity by facilitating immunogenic reagent trafficking, regulating T cell responses, and modulating the immune microenvironment. Moreover, biomaterial engineering tools have also advanced our understanding of B cell biology, further expediting the development of novel therapeutics. In this review, we will introduce the general concept of B cell immunobiology and highlight key biomaterial engineering strategies in the areas including B cell targeted antigen delivery, sustained B cell antigen delivery, antigen engineering, T cell help optimization, and B cell suppression. We will also discuss our perspective on future biomaterial engineering opportunities to leverage humoral immunity for therapeutics.

Macromolecular Cargo Encapsulation via In Vitro Assembly of Two-Component Protein Nanoparticles

Self-assembling protein nanoparticles are a promising class of materials for targeted drug delivery. Here, the use of a computationally designed, two-component, icosahedral protein nanoparticle is reported to encapsulate multiple macromolecular cargoes via simple and controlled self-assembly in vitro. Single-stranded RNA molecules between 200 and 2500 nucleotides in length are encapsulated and protected from enzymatic degradation for up to a month with length-dependent decay rates. Immunogenicity studies of nanoparticles packaging synthetic polymers carrying a small-molecule TLR7/8 agonist show that co-delivery of antigen and adjuvant results in a more than 20-fold increase in humoral immune responses while minimizing systemic cytokine secretion associated with free adjuvant. Coupled with the precise control over nanoparticle structure offered by computational design, robust and versatile encapsulation via in vitro assembly opens the door to a new generation of cargo-loaded protein nanoparticles that can combine the therapeutic effects of multiple drug classes.

Design of a symmetry-broken tetrahedral protein cage by a method of internal steric occlusion

Methods in protein design have made it possible to create large and complex, self-assembling protein cages with diverse applications. These have largely been based on highly symmetric forms exemplified by the Platonic solids. Prospective applications of protein cages would be expanded by strategies for breaking the designed symmetry, for example, so that only one or a few (instead of many) copies of an exterior domain or motif might be displayed on their surfaces. Here we demonstrate a straightforward design approach for creating symmetry-broken protein cages able to display singular copies of outward-facing domains. We modify the subunit of an otherwise symmetric protein cage through fusion to a small inward-facing domain, only one copy of which can be accommodated in the cage interior. Using biochemical methods and native mass spectrometry, we show that co-expression of the original subunit and the modified subunit, which is further fused to an outward-facing anti-GFP DARPin domain, leads to self-assembly of a protein cage presenting just one copy of the DARPin protein on its exterior. This strategy of designed occlusion provides a facile route for creating new types of protein cages with unique properties.

Impact of Protein Nanoparticle Shape on the Immunogenicity of Antimicrobial Glycoconjugate Vaccines

Protein self-assembling nanoparticles (NPs) can be used as carriers for antigen delivery to increase vaccine immunogenicity. NPs mimic the majority of invading pathogens, inducing a robust adaptive immune response and long-lasting protective immunity. In this context, we investigated the potential of NPs of different sizes and shapes-ring-, rod-like, and spherical particles-as carriers for bacterial oligosaccharides by evaluating in murine models the role of these parameters on the immune response. Oligosaccharides from Neisseria meningitidis type W capsular polysaccharide were conjugated to ring-shape or nanotubes of engineered Pseudomonas aeruginosa Hemolysin-corregulated protein 1 (Hcp1cc) and to spherical Helicobacter pylori ferritin. Glycoconjugated NPs were characterized using advanced technologies such as High-Performance Liquid Chromatography (HPLC), Asymmetric Flow-Field Flow fractionation (AF4), and Transmission electron microscopy (TEM) to verify their correct assembly, dimensions, and glycosylation degrees. Our results showed that spherical ferritin was able to induce the highest immune response in mice against the saccharide antigen compared to the other glycoconjugate NPs, with increased bactericidal activity compared to benchmark MenW-CRM197. We conclude that shape is a key attribute over size to be considered for glycoconjugate vaccine development.