Stable Vaccine Research Articles

Cooperative Assembly of Self-Adjusting α-Helical Coiled Coils along the Length of an mRNA Chain to Form a Thermodynamically Stable Nanotube Carrier.

Although mRNA delivery technology is very promising, problems in safety and transport arise due to the intrinsically low thermodynamic stability of the current mRNA carriers. Considering that mRNAs are filamentous and a nanotube is one of the most thermodynamically stable shapes among nanoassemblies, a nanotube is one of the most stable supramolecular structures that can be assembled with mRNA. Here, we develop a nanotube-shaped filamentous mRNA delivery platform that shows exceptionally high thermodynamic stability. The key to the development of the mRNA nanotube is the design of self-adjusting supramolecular building blocks (SABs) that have two disparate properties, i.e., dynamic property and stiffness, in a single molecule. The counterbalance of the dynamic property and stiffness in SABs enables the coating of mRNA by winding its way through the flexible and irregular mRNA chain via cooperative interactions. SAB nanotubes with targeting ligands installed show a high uptake efficiency in mammalian cells and controllable gene expression behavior. Thus, the mRNA nanotube provides an enabling technology toward the development of safe and stable mRNA vaccines and therapeutics.

Designing of Multi-Epitope Peptide Vaccine Based on Outer Membrane Proteins OmpF, OmpC, and PgtE of Salmonella enterica Typhi

Consumption of contaminated water and foods by Salmonella Typhi cause the most common enteric disease known as Typhoid fever in both humans and animals. Despite the existence of various vaccines but infectious diseases remain a major cause of mortality worldwide. Nowadays, in-silico tools design a reliable and stable vaccine to combat such infections. The study aimed to design and evaluate a multi-epitope vaccine based on the outer-membrane proteins of Salmonella Typhi. B-cells and T-cells epitopes were predicted. Predicted epitopes were connected by AAY, KK, and GPGPG linkers. Heparin-Binding Hemagglutinin Adhesin (HBHA) has been attached to the N-terminal of the final vaccine as a potent immune adjuvant. Epitope’s antigenicity, allergenicity, immunogenicity, and physicochemical characteristics were defined using in-silico tools. Molecular docking of vaccine-TLR4 was done. ∆G of vaccine-TLR4 is -3.91×104 Kcal mol-1 with 1.93 RMSD. The results indicated protein was stable and non-allergen. In conclusion, the multi-epitope vaccine base on outer membrane proteins of the Salmonella Typhi bacterium might be considered to combat typhoid fever.

Domain-based mRNA vaccines encoding spike protein N-terminal and receptor binding domains confer protection against SARS-CoV-2.

With the success of messenger RNA (mRNA) vaccines against coronavirus disease 2019, strategies can now focus on improving vaccine potency, breadth, and stability. We designed and evaluated domain-based mRNA vaccines encoding the wild-type spike protein receptor binding domain (RBD) or N-terminal domain (NTD) alone or in combination. An NTD-RBD-linked candidate vaccine, mRNA-1283, showed improved antigen expression, antibody responses, and stability at refrigerated temperatures (2° to 8°C) compared with the clinically available mRNA-1273, which encodes the full-length spike protein. In BALB/c mice administered mRNA-1283 as a primary series, booster, or variant-specific booster, similar or greater immune responses from viral challenge were observed against wild-type, beta, delta, or omicron (BA.1) viruses compared with mRNA-1273-immunized mice, especially at lower vaccine dosages. K18-hACE2 mice immunized with mRNA-1283 or mRNA-1273 as a primary series demonstrated similar degrees of protection from challenge with SARS-CoV-2 Delta and Omicron variants at all vaccine dosages. These results support clinical assessment of mRNA-1283, which has now entered clinical trials (NCT05137236).

An immunoinformatics and extended molecular dynamics approach for designing a polyvalent vaccine against multiple strains of Human T-lymphotropic virus (HTLV).

Human T-lymphotropic virus (HTLV), a group of retroviruses belonging to the oncovirus family, has long been associated with various inflammatory and immunosuppressive disorders. At present, there is no approved vaccine capable of effectively combating all the highly pathogenic strains of HTLV that makes this group of viruses a potential threat to human health. To combat the devastating impact of any potential future outbreak caused by this virus group, our study employed a reverse vaccinology approach to design a novel polyvalent vaccine targeting the highly virulent subtypes of HTLV. Moreover, we comprehensively analyzed the molecular interactions between the designed vaccine and corresponding Toll-like receptors (TLRs), providing valuable insights for future research on preventing and managing HTLV-related diseases and any possible outbreaks. The vaccine was designed by focusing on the envelope glycoprotein gp62, a crucial protein involved in the infectious process and immune mechanisms of HTLV inside the human body. Epitope mapping identified T cell and B cell epitopes with low binding energies, ensuring their immunogenicity and safety. Linkers and adjuvants were incorporated to enhance the vaccine's stability, antigenicity, and immunogenicity. Initially, two vaccine constructs were formulated, and among them, vaccine construct-2 exhibited superior solubility and structural stability. Molecular docking analyses also revealed strong binding affinity between the vaccine construct-2 and both targeted TLR2 and TLR4. Molecular dynamics simulations demonstrated enhanced stability, compactness, and consistent hydrogen bonding within TLR-vaccine complexes, suggesting a strong binding affinity. The stability of the complexes was further corroborated by contact, free energy, structure, and MM-PBSA analyses. Consequently, our research proposes a vaccine targeting multiple HTLV subtypes, offering valuable insights into the molecular interactions between the vaccine and TLRs. These findings should contribute to developing effective preventive and treatment approaches against HTLV-related diseases and preventing possible outbreaks. However, future research should focus on in-depth validation through experimental studies to confirm the interactions identified in silico and to evaluate the vaccine's efficacy in relevant animal models and, eventually, in clinical trials.

Construction of a Delivery Platform for Vaccine Based on Modified Nanotubes: Sustainable Prevention against Plant Viral Disease, Simplified Preparation Method, and Protection of Plasmid.

Control of plant viral diseases through cross-protection conferred by an attenuated vaccine is an important strategy for plant protection. However, the mutated site of an attenuated vaccine may not be stably inherited, while viruses have evolved efficient repair mechanisms for the maintenance of genomic integrity. Here, the wide host range and broad selection of mutation sites in cucumber mosaic virus (CMV) enabled construction of an attenuated vaccine through insertional mutation of the CMV 2b protein. CMV-R2E was stably inherited in tobacco for more than 10 generations and had a high relative control efficacy of CMV. Then, the use of polyetherimide (PEI)-modified functionalized carboxylated single-walled carbon nanotubes (PSWNTs) was investigated for vaccine delivery to address the problems of poor stability, complex procedure on field application, and exacting storage conditions with Agrobacterium inoculation. After co-incubating at a 1:300 ratio for 30 min, the vaccine and PSWNTs combined to form pCMV-R2E@PSWNTs, which resulted in a significant increase in the average height of the nanoparticles from 6.56 to 72.34 nm. The relative control efficacy of pCMV-R2E@PSWNTs to CMV was found to be 90.37%. Furthermore, the protective effect of PSWNTs on plasmids was investigated under various environmental conditions and the potential plant toxicity of pCMV-R2E@PSWNTs was assessed, providing a theoretical basis for field application of the vaccine nano-delivery system. A highly effective, stable viral vaccine for plants was thus developed and combined with nanocarriers to address the problems of field application. This approach has the potential to enable wider use of attenuated vaccines for sustainable prevention against plant viral disease in the field.

Deep Learning-based Predictive Model of mRNA Vaccine Deterioration: An Analysis of the Stanford COVID-19 mRNA Vaccine Dataset

The emergence of SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has resulted in a global health crisis leading to widespread illness, death, and daily life disruptions. Having a vaccine for COVID-19 is crucial to controlling the spread of the virus which will help to end the pandemic and restore normalcy to society. Messenger RNA (mRNA) molecules vaccine has led the way as the swift vaccine candidate for COVID-19, but it faces key probable restrictions including spontaneous deterioration. To address mRNA degradation issues, Stanford University academics and the Eterna community sponsored a Kaggle competition.This study aims to build a deep learning (DL) model which will predict deterioration rates at each base of the mRNA molecule. A sequence DL model based on a bidirectional gated recurrent unit (GRU) is implemented. The model is applied to the Stanford COVID-19 mRNA vaccine dataset to predict the mRNA sequences deterioration by predicting five reactivity values for every base in the sequence, namely reactivity values, deterioration rates at high pH, at high temperature, at high pH with Magnesium, and at high temperature with Magnesium. The Stanford COVID-19 mRNA vaccine dataset is split into the training set, validation set, and test set. The bidirectional GRU model minimizes the mean column wise root mean squared error (MCRMSE) of deterioration rates at each base of the mRNA sequence molecule with a value of 0.32086 for the test set which outperformed the winning models with a margin of (0.02112). This study would help other researchers better understand how to forecast mRNA sequence molecule properties to develop a stable COVID-19 vaccine.

Cyclodextrin in Vaccines: Enhancing Efficacy and Stability

Cyclodextrins, a family of cyclic oligosaccharides, have received considerable interest in the field of pharmaceuticals due to their unique molecular structure and versatile properties. In the context of vaccines, cyclodextrins can effectively encapsulate antigens, ensuring their protection from degradation and improving their immunogenicity. Cyclodextrins offer stability advantages to vaccines by preventing the degradation of labile vaccine components during storage and transportation. Furthermore, cyclodextrins can serve as adjuvants, potentiating the immune response triggered by vaccines. Their unique structure and interaction with the immune system enhance the recognition of antigens by immune cells, leading to an improved activation of both innate and adaptive immune responses. This adjuvant effect contributes to the development of robust and long-lasting immune protection against targeted pathogens. Owing to the distinctive attributes inherent to nanoparticles, their integration into vaccine formulations has assumed an imperative role. Through the encapsulation of vaccine antigens/adjuvants within cyclodextrin nanoparticles, the potency and stability of vaccines can be notably enhanced. In particular, the capacity of amphiphilic cyclodextrins to form nanoparticles through self-assembly without surfactants or co-solvents is a captivating prospect for their application as carrier systems for antigens. In conclusion, cyclodextrins present a promising platform for enhancing the efficacy and stability of vaccines. Their ability to encapsulate antigens, stabilize labile vaccine components and act as adjuvants demonstrates their potential to revolutionize vaccine formulation and delivery. Further research and development in this field will facilitate the translation of cyclodextrin-based vaccine technologies into practical and impactful immunization strategies, ultimately benefiting global health and disease prevention.

Assessing the physicochemical stability and intracellular trafficking of mRNA-based COVID-19 vaccines

The emergence of SARS-CoV-2 in Wuhan, China in 2019 has had a profound impact on humanity in every facet. While vaccines against this viral pathogen have been approved a year later, limitations to this therapeutic intervention persist, such as drug sensitivity to transportation and storage conditions, as well as significant financial losses from non-injected resuspended vials.Our research delves into the effects of thermal denaturation (4 – 40 °C) and light irradiation (720 and 10460 kJ/m2) on the mRNA-based vaccines BNT162b2 from BioNTech/Pfizer and mRNA-1273 from Moderna. We also investigated vaccine stability following incubation in syringes to simulate potential interactions with silicon oil. By assaying the effects of these stressors via biochemical and biophysical methods, we aim to elucidate the physicochemical properties, integrity, and stability of these mRNA-based vaccines.Furthermore, the incorporation of a fluorophore into both vaccines allowed us to monitor their localization within cells and assess their capacity to evade vesicular transport mechanisms, thus evaluating the differences between the two formulations.A comprehensive understanding of the aforementioned attributes can enable the establishment of optimal storage and manipulation conditions for these vaccines, thereby ensuring their safe and efficacious application while minimizing the waste of functional and safe therapeutic agents.

Intradermal administration of DNA vaccine targeting Omicron SARS-CoV-2 via pyro-drive jet injector provides the prolonged neutralizing antibody production via germinal center reaction

Emerging SARS-CoV-2 Omicron variants are highly contagious with enhanced immune escape mechanisms against the initially approved COVID-19 vaccines. Therefore, we require stable alternative-platform vaccines that confer protection against newer variants of SARS-CoV-2. We designed an Omicron B.1.1.529 specific DNA vaccine using our DNA vaccine platform and evaluated the humoral and cellular immune responses. SD rats intradermally administered with Omicron-specific DNA vaccine via pyro-drive jet injector (PJI) thrice at 2-week intervals elicited high antibody titers against the Omicron subvariants as well as the ancestral strain. Indeed, the Omicron B.1.1.529-specific antibody titer and neutralizing antibody were higher than that of other strains. Longitudinal monitoring indicated that anti-spike (ancestral and Omicron) antibody titers decreased toward 30 weeks after the first vaccination dose. However, neutralization activity remained unaltered. Germinal center formation was histologically detected in lymph nodes in rats immunized with Omicron DNA vaccine. Ancestral spike-specific immune cell response was slightly weaker than Omicron spike-specific response in splenocytes with Omicron-adapted DNA vaccine, evaluated by ELISpot assay. Collectively, our findings suggest that Omicron targeting DNA vaccines via PJI can elicit robust durable antibody production mediated by germinal center reaction against this new variant as well as partially against the spike protein of other SARS-CoV-2 variants.

Recent Advancement in mRNA Vaccine Development and Applications.

Messenger RNA (mRNA) vaccine development for preventive and therapeutic applications has evolved rapidly over the last decade. The mRVNA vaccine has proven therapeutic efficacy in various applications, including infectious disease, immunotherapy, genetic disorders, regenerative medicine, and cancer. Many mRNA vaccines have made it to clinical trials, and a couple have obtained FDA approval. This emerging therapeutic approach has several advantages over conventional methods: safety; efficacy; adaptability; bulk production; and cost-effectiveness. However, it is worth mentioning that the delivery to the target site and in vivo degradation and thermal stability are boundaries that can alter their efficacy and outcomes. In this review, we shed light on different types of mRNA vaccines, their mode of action, and the process to optimize their development and overcome their limitations. We also have explored various delivery systems focusing on the nanoparticle-mediated delivery of the mRNA vaccine. Generally, the delivery system plays a vital role in enhancing mRNA vaccine stability, biocompatibility, and homing to the desired cells and tissues. In addition to their function as a delivery vehicle, they serve as a compartment that shields and protects the mRNA molecules against physical, chemical, and biological activities that can alter their efficiency. Finally, we focused on the future considerations that should be attained for safer and more efficient mRNA application underlining the advantages and disadvantages of the current mRNA vaccines.

Enhancing effect of chitosan nanoparticles on the immune efficacy of Bordetella bronchiseptica outer membrane vesicles

The outer membrane vesicle (OMV) of bacteria is a bilayer membrane vesicle with a diameter of about 10–300 nm that is secreted during the growth of Gram-negative bacteria. OMV is considered as a high-quality vaccine candidate antigen because of its natural immunogenicity and non-replicability. Although the excellent antigenicity of OMV has been widely confirmed, its instability and heterogeneity greatly affect its immune effect. Many studies have demonstrated that in combination with nanoparticles can enhance the stability of OMV. In this study, OMVs were used to coat chitosan nanoparticles (CNPs) and obtain a stable OMV vaccine. The characteristics, including morphology, hydrodynamic size, and zeta potential were evaluated. The immune protection of CNP-OMV and anti-infection efficacy were examined and compared in vivo and in vitro. The results showed that the CNP-OMV were homogenous with a size of 139 nm and a stable core–shell structure. And CNP-OMV could significantly increase the cell proliferation, phagocytosis and TNF-α, IL-6 and IL-10 secretion of RAW264.7 in vitro. In vivo, CNP-OMV could significantly increase the levels of anti-Bb and OMV IgG antibodies. Levels of blood lymphocyte, and Th1 (IFN-γ, IL-12), Th2 (IL-4, IL-5), and Th17 (IL-17, TNF-α) type cytokines in the serum were all significantly increased. At the same time, CNP-OMV could significantly reduce the bacterial invading the lungs of challenged rabbits. And CNP-OMV could largely protect the lungs from injury. The above results showed that CNP-OMV had a good immune efficacy and could resist the infection of Bordetella bronchiseptica. This study provided a scientific basis for the development of novel effective and safe vaccine against Bordetella bronchiseptica, and also provided a new idea for the development of new bacterial vaccine.

Development and Characterization of an In Vitro Cell-Based Assay to Predict Potency of mRNA-LNP-Based Vaccines.

Messenger RNA (mRNA) vaccines have emerged as a flexible platform for vaccine development. The evolution of lipid nanoparticles as effective delivery vehicles for modified mRNA encoding vaccine antigens was demonstrated by the response to the COVID-19 pandemic. The ability to rapidly develop effective SARS-CoV-2 vaccines from the spike protein genome, and to then manufacture multibillions of doses per year was an extraordinary achievement and a vaccine milestone. Further development and application of this platform for additional pathogens is clearly of interest. This comes with the associated need for new analytical tools that can accurately predict the performance of these mRNA vaccine candidates and tie them to an immune response expected in humans. Described here is the development and characterization of an imaging based in vitro assay able to quantitate transgene protein expression efficiency, with utility to measure lipid nanoparticles (LNP)-encapsulated mRNA vaccine potency, efficacy, and stability. Multiple biologically relevant adherent cell lines were screened to identify a suitable cell substrate capable of providing a wide dose-response curve and dynamic range. Biologically relevant assay attributes were examined and optimized, including cell monolayer morphology, antigen expression kinetics, and assay sensitivity to LNP properties, such as polyethylene glycol-lipid (or PEG-lipid) composition, mRNA mass, and LNP size. Collectively, this study presents a strategy to quickly optimize and develop a robust cell-based potency assay for the development of future mRNA-based vaccines.

Advances of Nanotechnology Toward Vaccine Development Against Animal Infectious Diseases

AbstractVaccines are the most effective means of controlling infectious diseases. Increasingly epidemics have driven the development of vaccines for human use. However, insufficient attention has been paid to preventing animal epidemics. The spread of animal epidemics directly affects food and nutritional safety, the economy, and outbreaks of zoonotic diseases, which can eventually threaten human health. Reducing safety risks, saving production costs, adapting to mass vaccination, and improving immunogenicity are important that must be considered in animal vaccines. Nanotechnology in vaccine development provides unique advantages in meeting these challenges, both at in vitro preparation and in vivo immune response levels. In terms of in vitro vaccine formulation, nanoparticles offer the possibility to provide multiple antigen display sites, maintain antigen conformation, and improve vaccine stability, which facilitates the development of vaccines with enhanced immunogenicity and thermal stability. In terms of in vivo vaccine‐induced immunity, nanoparticles show superior immunostimulatory activity which facilitates multiple immune response processes, including antigen delivery, cellular uptake, antigen presentation, and lymphocyte activation, thus markedly augmenting vaccine‐mediated immune responses. Herein, the application of nanotechnology to vaccine development and the characteristics of animal vaccines are reviewed, aiming to provide general guidelines for the design of future vaccines against animal infectious diseases and promote harmonious coexistence of humans and animals.

Stability of polymeric cationic niosomes and their plasmid DNA-based complexes as gene delivery carriers

This study aims to explore the stability of lipo-polymeric niosomes/niosome-based pCMS-EGFP complexes under different storage temperatures (25 °C, 4 °C, and −20 °C). To date, the question of nucleic acid-complex stability is one of the most vital issues in gene delivery applications. The need for stable vaccines during the COVID-19 pandemic has merely highlighted it. In the case of niosomes as gene carriers, the scientific literature still lacks comprehensive stability studies. In this study, the physicochemical features of niosomes/nioplexes in terms of size, surface charge, and polydispersity index (PDI), along with transfection efficiency, and cytotoxicity in NT2 cells were evaluated for 8 weeks. Compared to day 0, the physicochemical features of the niosomes stored at 25 °C and −20 °C changed dramatically in terms of size, zeta potential, and PDI, while remaining in reasonable values when stored at 4 °C. However, niosomes and nioplexes stored at 4 °C and −20 °C showed nearly stable transfection efficiency values, yet an obvious decrease at 25 °C. This article provides a proof of concept into the stability of polymeric cationic niosomes and their nioplexes as promising gene delivery vehicles. Moreover, it highlights the practical possibility of storing nioplexes at 4 °C for up to 2 months, as an alternative to niosomes, for gene delivery purposes.

Impact of aluminum adjuvants on the stability of pneumococcal polysaccharide-protein conjugate vaccines

Development of a vaccine drug product requires formulation optimization to ensure that the vaccine’s effectiveness is preserved upon storage throughout the shelf-life of the product. Although aluminum adjuvants have been widely used in vaccine formulations to safely and effectively potentiate an immune response, careful attention must be directed towards ensuring that the type of aluminum adjuvant does not impact the stability of the antigenic composition. PCV15 is a polysaccharide-protein conjugate vaccine comprising the pneumococcal polysaccharide (PnPs) serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F), each individually conjugated to the protein carrier CRM197. PCV15 was formulated with either amorphous aluminum hydroxyphosphate sulfate adjuvant (AAHS) or aluminum phosphate adjuvant (AP) and examined for both stability and immunogenicity. Using a collection of methods to evaluate vaccine stability, it was discovered that certain PCV15 serotypes (e.g., 6A, 19A, 19F) formulated with AAHS resulted in a reduction of immunogenicity in vivo and a reduction in recoverable dose as tested by an in vitro potency assay. The same polysaccharide-protein conjugates formulated with AP were stable regarding all measures tested. Moreover, the reduction in potency of certain serotypes correlated with chemical degradation of the polysaccharide antigen caused by the aluminum adjuvant as measured by reducing polyacrylamide gel electrophoresis (SDS-PAGE), High-Pressure Size Exclusion Chromatography coupled with UV detection (HPSEC-UV) and ELISA immunoassay. This study suggests a formulation, which includes AAHS, may negatively impact the stability of a pneumococcal polysaccharide-protein conjugate vaccine that contains phosphodiester groups. This decrease in stability would likely result in a decrease in the “active” concentration of antigen dose, and herein, it is shown that such instability directly compromised vaccine immunogenicity in an animal model. The results presented in this study help to explain critical degradation mechanisms of pneumococcal polysaccharide-protein conjugate vaccines.

Correlating physicochemical and biological properties to define critical quality attributes of a rAAV vaccine candidate

Recombinant adeno-associated viruses (rAAVs) are a preferred vector system in clinical gene transfer. A fundamental challenge to formulate and deliver rAAVs as stable and efficacious vaccines is to elucidate interrelationships between the vector's physicochemical properties and biological potency. To this end, we evaluated an rAAV-based coronavirus disease 2019 (COVID-19) vaccine candidate that encodes the Spike antigen (AC3) and is produced by a commercially viable process. First, state-of-the-art analytical techniques were employed to determine key structural attributes of AC3, including primary and higher-order structures, particle size, empty/full capsid ratios, aggregates, and multi-step thermal degradation pathway analysis. Next, several quantitative potency measures for AC3 were implemented, and data were correlated with the physicochemical analyses on thermally stressed and control samples. Results demonstrate links between decreasing AC3 physical stability profiles, invitro transduction efficiency in a cell-based assay, and, importantly, invivo immunogenicity in a mouse model. These findings are discussed in the general context of future development of rAAV-based vaccine candidates as well as specifically for the rAAV vaccine application under study.

Designing a bioadjuvant candidate vaccine targeting infectious bursal disease virus (IBDV) using viral VP2 fusion and chicken IL-2 antigenic epitope: A bioinformatics approach

Infectious Bursal Disease (IBD) is a common and contagious viral infection that significantly affects the poultry industry. This severely suppresses the immune system in chickens, thereby threating their health and well-being. Vaccination is the most effective strategy for preventing and controlling this infectious agent. The development of VP2-based DNA vaccines combined with biological adjuvants has recently received considerable attention due to their effectiveness in eliciting both humoral and cellular immune responses. In this study, we applied bioinformatics tools to design a fused bioadjuvant candidate vaccine from the full-length sequence of the VP2 protein of IBDV isolated in Iran using the antigenic epitope of chicken IL-2 (chiIL-2). Furthermore, to improve the antigenic epitope presentation and to maintain the three-dimensional structure of the chimeric gene construct, the P2A linker (L) was used to fuse the two fragments.Our in-silico analysis for the design of a candidate vaccine indicates that a continuous sequence of amino acid residues ranging from 105 to 129 in chiIL-2 is proposed as a B cell epitope by epitope prediction servers. The final 3D structure of the VP2-L-chiIL-2105-129 was subjected to physicochemical property determination, molecular dynamic simulation, and antigenic site determination. The results of these analyses led to the development of a stable candidate vaccine that is non-allergenic and has the potential for antigenic surface display potential and adjuvant activity. Finally, it is necessary to investigate the immune response induced by our proposed vaccine in avian hosts. Notably, increasing the immunogenicity of DNA vaccines can be achieved by combining antigenic proteins with molecular adjuvants using the principle of rational vaccine design.

Broad immunity to SARS-CoV-2 variants of concern mediated by a SARS-CoV-2 receptor-binding domain protein vaccine.

The SARS-CoV-2 global pandemic has fuelled the generation of vaccines at an unprecedented pace and scale. However, many challenges remain, including: the emergence of vaccine-resistant mutant viruses, vaccine stability during storage and transport, waning vaccine-induced immunity, and concerns about infrequent adverse events associated with existing vaccines. We report on a protein subunit vaccine comprising the receptor-binding domain (RBD) of the ancestral SARS-CoV-2 spike protein, dimerised with an immunoglobulin IgG1 Fc domain. These were tested in conjunction with three different adjuvants: a TLR2 agonist R4-Pam2Cys, an NKT cell agonist glycolipid α-Galactosylceramide, or MF59® squalene oil-in-water adjuvant, using mice, rats and hamsters. We also developed an RBD-human IgG1 Fc vaccine with an RBD sequence of the immuno-evasive beta variant (N501Y, E484K, K417N). These vaccines were also tested as a heterologous third dose booster in mice, following priming with whole spike vaccine. Each formulation of the RBD-Fc vaccines drove strong neutralising antibody (nAb) responses and provided durable and highly protective immunity against lower and upper airway infection in mouse models of COVID-19. The 'beta variant' RBD vaccine, combined with MF59® adjuvant, induced strong protection in mice against the beta strain as well as the ancestral strain. Furthermore, when used as a heterologous third dose booster, the RBD-Fc vaccines combined with MF59® increased titres of nAb against other variants including alpha, delta, delta+, gamma, lambda, mu, and omicron BA.1, BA.2 and BA.5. These results demonstrated that an RBD-Fc protein subunit/MF59® adjuvanted vaccine can induce high levels of broadly reactive nAbs, including when used as a booster following prior immunisation of mice with whole ancestral-strain spike vaccines. This vaccine platform offers a potential approach to augment some of the currently approved vaccines in the face of emerging variants of concern, and it has now entered a phase I clinical trial. This work was supported by grants from the Medical Research Future Fund (MRFF) (2005846), The Jack Ma Foundation, National Health and Medical Research Council of Australia (NHMRC; 1113293) and Singapore National Medical Research Council (MOH-COVID19RF-003). Individual researchers were supported by an NHMRC Senior Principal Research Fellowship (1117766), NHMRC Investigator Awards (2008913 and 1173871), Australian Research Council Discovery Early Career Research Award (ARC DECRA; DE210100705) and philanthropic awards from IFM investors and the A2 Milk Company.

Oral tablet vaccination against SARS-CoV-2 spike boosts cross-reactive serum and mucosal neutralizing antibodies following mRNA vaccination: a phase 2 clinical trial

Abstract Current SARS-CoV-2 intramuscular vaccines do not induce the breadth of immunity needed to halt the development of new variants. New strategies that elicit immunity at the site of infection could induce cross-reactive mucosal responses that decrease transmission. We developed a room-temperature stable oral tablet vaccine composed of recombinant adenovirus type 5 expressing the spike gene of SARS-CoV-2. In an open label phase 2 clinical trial (NCT05067933), 66 subjects, either naïve or previously mRNA vaccinated, received 2 doses of a low or a high dose 28 days apart. The vaccine was well tolerated with a benign safety profile. Among previously vaccinated subjects, oral tablet vaccination was able to boost serum IgG and IgA at 29 and 57 days post-vaccination. The serum neutralizing antibodies increased 1.6-fold, from 481 AU/ml to 778 AU/ml at Day 57. The subjects with lower starting titers had greater increases after oral boosting. Most subjects in the vaccinated cohorts had an increase in SARS-CoV-2 IgA in the nose or saliva. This mucosal IgA was not only cross-reactive against SARS-CoV-2 variants but also SARS-CoV-1 and MERS. These samples demonstrated surrogate neutralizing activity against both Wuhan and omicron BA4/5, despite the vaccine expressing Wuhan antigens, highlighting the ability of mucosal vaccination to elicit cross-reactive responses. Overall, this vaccine was safe and well tolerated. It induced cross-reactive immunity in both the serum and more importantly, in the mucosa, the site of infection. This offers an ideal platform for boosting immune responses that could decrease transmission rates and extend protection to emerging variants. It also offers unique advantages in distribution to curb future pandemics.

Threat of resurgence or hope for global eradication of poliovirus?

Recent outbreaks of poliomyelitis in countries that have been free of cases for decades highlight the challenges of eradicating polio in a globalized interconnected world beset with a novel viral pandemic. We provide an epidemiological update, advancements in vaccines, and amendments in public health strategy of poliomyelitis in this review. Last year, new cases of wild poliovirus type 1 (WPV1) were documented in regions previously documented to have eradicated WPV1 and reports of circulating vaccine-derived poliovirus type 2 (cVDPV2) and 3 (cVDPV3) in New York and Jerusalem made international headlines. Sequencing of wastewater samples from environmental surveillance revealed that the WPV1 strains were related to WPV1 lineages from endemic countries and the cVDPV2 strains from New York and Jerusalem were not only related to each other but also to environmental isolates found in London. The evidence of importation of WPV1 cases from endemic countries, and global transmission of cVDPVs justifies renewed efforts in routine vaccination programs and outbreak control measures that were interrupted by the COVID-19 pandemic. After the novel oral poliovirus vaccine type 2 (nOPV2) received emergency authorization for containment of cVDPV2 outbreaks in 2021, subsequent reduced incidence, transmission rates, and vaccine adverse events, alongside increased genetic stability of viral isolates substantiates the safety and efficacy of nOPV2. The nOPV1 and nOPV3 vaccines, against type 1 and 3 cVDPVs, and measures to increase accessibility and efficacy of inactivated poliovirus vaccine (IPV) are in development. A revised strategy utilizing more genetically stable vaccine formulations, with uninterrupted vaccination programs and continued active surveillance optimizes the prospect of global poliomyelitis eradication.