Old and new adjuvants

Establishment of a novel adjuvant screening system for the development of intranasal vaccine adjuvants

Vaccine adjuvants play a pivotal role in enhancing the immunogenicity of vaccines. Some vaccine modalities, such as subunit vaccines and split vaccines, are inherently poorly immunogenic and benefit greatly from combination with adjuvants. Notable examples, such as the herpes zoster glycoprotein E subunit vaccine and the Novavax COVID-19 (NVX-CoV2373) vaccine, underscore the importance of adjuvants in vaccination. Mucosal vaccines, and intranasal vaccines in particular, are gaining increasing attention for their potential to combat respiratory viral infections more effectively than subcutaneous and intramuscular vaccines. This is because mucosal vaccines can induce immunoglobulin (Ig)A production at mucosal surfaces to prevent the transmission of respiratory viruses such as influenza and severe acute respiratory syndrome coronavirus 2. However, few adjuvanted mucosal vaccines have been approved to date. To address this gap, we developed an adjuvant screening system to identify adjuvants suitable for use in combination with intranasal vaccines from a list of existing approved drugs or pharmaceutical additives. By analyzing biomarker gene expression levels, our screening system was able to predict the adjuvanticity and toxicity of a given adjuvant candidate in a short time. Using this screening system, we have to date identified some pharmaceutical additives, which induced a robust antigen-specific IgA antibody response following a single intranasal administration, without significant leukopenic toxicity or type I interferon inducibility. In this review, we discuss the development of our novel adjuvant evaluation system and its potential to enhance the efficacy of mucosal vaccines.

Skin damage signals mediate allergic sensitization to spatially unlinked antigen

Our current understanding of immunity to pathogens suggests that anatomic coupling of antigens with danger signals is a required feature for the formation of immune memory. However, in the context of pathogen-independent inflammation, the stringency of this anatomical coupling is unclear. Here, we demonstrate that multiple modes of skin injury were sufficient to induce a humoral response to antigens introduced in the gut. Skin damage induced a narrow subset of endocrine cytokines that were necessary and sufficient for the priming of antigens introduced at various distal tissues. Thus, in addition to "local priming" of antigen entering through damaged skin, there also exists another paradigm of "remote priming" where anatomical coupling is not essential because of the dissemination of damage-associated intermediaries. Our findings have implications for understanding the fundamental mechanisms of the formation of humoral memory with wide implications for diseases such as food allergy and in vaccinology.

Metal-Protein Hybrid Materials: Unlocking New Frontiers in Biomedical Applications

Metal-protein hybrid materials represent a novel class of functional materials that exhibit exceptional physicochemical properties and tunable structures, rendering them remarkable applications in diverse fields, including materials engineering, biocatalysis, biosensing, and biomedicine. The design and development of multifunctional and biocompatible metal-protein hybrid materials have been the subject of extensive research and a key aspiration for practical applications in clinical settings. This review provides a comprehensive analysis of the design strategies, intrinsic properties, and biomedical applications of these hybrid materials, with a specific emphasis on their potential in cancer therapy, drug and vaccine delivery, antibacterial treatments, and tissue regeneration. Through rational design, stable metal-protein hybrid materials can be synthesized using straightforward methods, enabling them with therapeutic, delivery, immunomodulatory, and other desired functionalities. Finally, the review outlines the existing limitations and challenges associated with metal-protein hybrid materials and evaluates their potential for clinical translation, providing insights into their practical implementation within biomedical applications.

Computational identification of B and T-cell epitopes for designing a multi-epitope vaccine against SARS-CoV-2 spike glycoprotein

Although the peak of the COVID-19 pandemic has passed, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to pose a significant global threat and remains a public health concern. Given the ongoing risk and the substantial loss of life caused by the virus, continuous research into vaccine development is essential. This study employs immunoinformatics approaches to identify T-cell and B-cell epitopes for designing a multi-epitope peptide vaccine candidate targeting the Omicron variant. The proposed vaccine construct comprises 1435 amino acids, including eight linear B lymphocyte, seven cytotoxic T lymphocyte, and five helper T lymphocyte epitopes, along with appropriate adjuvants and linkers. The evaluation of the vaccine revealed high antigenicity, non-allergenicity, non-toxicity, and favorable physicochemical properties. To further assess its efficacy, molecular docking studies were performed to investigate interactions between the vaccine and key immune components, including Toll-like receptors and major histocompatibility complex molecules. Stability of these interactions was confirmed using molecular dynamics simulations in triplicate, conducted over 100 ns using GROMACS 2023 to compute key metrics, such as root mean square deviation, root mean square fluctuation, solvent-accessible surface area, and radius of gyration. The results demonstrate that the multi-epitope vaccine has the potential to elicit strong immune responses against the Omicron variant, providing a promising foundation for further experimental validation and clinical development in COVID-19 vaccine research.

Heightened innate immune state induced by viral vector leads to enhanced response to challenge and prolongs malaria vaccine protection

Cytomegalovirus is a promising vaccine vector; however, mechanisms promoting CD4 T cell responses to challenge, by CMV as a vector, are unknown. The ability of MCMV to prolong immunity generated by short-lived malaria vaccine was tested. MCMV provided non-specific protection to challenge with Plasmodium and increased interleukin-12 (IL-12) and CD8α+ dendritic cell (DC) numbers through prolonged MCMV-dependent interferon gamma (IFN-γ) production. This late innate response to MCMV increased IL-12 upon challenge and increased the polyclonal CD4 effector T cell response to Plasmodium, protecting in an IL-12-dependent manner. Although Plasmodium-vaccine-induced protection decayed by d200, MCMV restored protection through IFN-γ. Mechanistically, protection depended on MCMV-induced-IFN-γ increasing CD8α+ DCs and IL-12p40. MCMV expressing a Plasmodium epitope increased parasite-specific CD4 effector and effector memory T cells persisting after malaria vaccination, both phenotypes reported to protect. Overall, enhanced innate cell status, a mechanism of heterologous protection by MCMV, led to a stronger T cell response to challenge.

miR-147-3p in pathogenic CD4 T cells controls chemokine receptor expression for the development of experimental autoimmune diseases

Incomplete Freund's adjuvant (IFA) has long been used to trigger autoimmune diseases in animal models, such as experimental autoimmune encephalitis and collagen-induced arthritis. However, the molecular mechanisms that control CD4 T cell effector functions and lead to the development of autoimmune diseases are not well understood. A self-antigen and heat-killed Mycobacterium tuberculosis emulsified in IFA augmented the activation of CD4 T cells, leading to the differentiation of pathogenic CD4 T cells in the draining lymph nodes. In contrast, IFA emulsification did not elicit Foxp3+ regulatory T cell expansion. We found that pathogenic Th1 cells expressed miR-147-3p, which targets multiple genes to affect T cell function. Finally, miR-147-3p expressed in CXCR6+SLAMF6- Th1 cells was required for the onset of neurological symptoms through the control of CXCR3 expression. Our findings demonstrate that miR-147-3p expressed in pathogenic CD4 T cells regulates the migratory potential in peripheral tissues and impacts the development of autoimmune diseases.

Vaccine optimization for highly pathogenic avian influenza: Assessment of antibody responses and protection for virus-like particle vaccines in chickens

Background

Recent outbreaks of clade 2.3.4.4b highly pathogenic avian influenza (HPAI) H5N1 viruses in regions previously less affected since 2020 have raised global concerns. Implementing mass immunization or ring vaccination in poultry should be a countermeasure ready to contain disease outbreaks. This study focuses on developing a recombinant H5N2 vaccine based on virus-like particles (VLPs) against clade 2.3.4.4c, the predominant HPAI subclade in Taiwan since its emergence, leading to a large outbreak in 2015.

Methods

The study aimed to confirm the effectiveness of clade 2.3.4.4c H5N2 VLPs in protecting chickens and identify the best adjuvants for the VLP vaccine. We used Montanide 71VG-adjuvanted inactivated RG6 to establish the immunization protocol, followed by prime-boost H5N2-VLP immunizations. We compared adjuvants: 71VG, 71VG with VP3, and Alum with VP3. Serum samples were tested for antibodies against homologous vaccine antigens and cross-clade antigens by hemagglutination inhibition (HI) assays. Finally, we evaluated the protective efficacy by lethally challenging immunized chickens with H5 viruses from clade 1 or 2.3.4.4c.

Results

Poultry adjuvant 71VG significantly enhanced antibody responses in chickens with inactivated RG6 compared to unadjuvanted inactivated virus. While increasing antigen dosage enhanced 71VG adjuvanted RG6-induced antibody titers, the vaccine displayed minimal cross-reactivity against locally circulating HPAI H5N2. In contrast, H5N2-VLP containing the HA protein of clade 2.3.4.4c, adjuvanted with (FMDV) VP3 in 71VG, significantly promoted HI antibody responses. All H5N2-VLP immunized chickens survived lethal challenges with the local clade 2.3.4.4c H5 strain.

Conclusion

The study demonstrated the immunogenic potential of the VLP vaccine in chickens. Our findings offer insights for optimizing VLP vaccines, allowing the incorporation of the HA of currently circulating H5 viruses to effectively mitigate the impact of the rapidly evolving clade 2.3.4.4 H5 outbreaks.

Lipid Nanoparticle with 1,2-Di-O-octadecenyl-3-trimethylammonium-propane as a Component Lipid Confers Potent Responses of Th1 Cells and Antibody against Vaccine Antigen

Adjuvants are effective tools to enhance vaccine efficacy and control the type of immune responses such as antibody and T helper 1 (Th1)- or Th2-type responses. Several studies suggest that interferon (IFN)-γ-producing Th1 cells play a significant role against infections caused by intracellular bacteria and viruses; however, only a few adjuvants can induce a strong Th1-type immune response. Recently, several studies have shown that lipid nanoparticles (LNPs) can be used as vaccine adjuvants and that each LNP has a different adjuvant activity. In this study, we screened LNPs to develop an adjuvant that can induce Th1 cells and antibodies using a conventional influenza split vaccine (SV) as an antigen in mice. We observed that LNP with 1,2-di-O-octadecenyl-3-trimethylammonium-propane (DOTMA) as a component lipid (DOTMA-LNP) elicited robust SV-specific IgG1 and IgG2 responses compared with SV alone in mice and was as efficient as SV adjuvanted with other adjuvants in mice. Furthermore, DOTMA-LNPs induced robust IFN-γ-producing Th1 cells without inflammatory responses compared to those of other adjuvants, which conferred strong cross-protection in mice. We also demonstrated the high versatility of DOTMA-LNP as a Th1 cell-inducing vaccine adjuvant using vaccine antigens derived from severe acute respiratory syndrome coronavirus 2 and Streptococcus pneumoniae. Our findings suggest the potential of DOTMA-LNP as a safe and effective Th1 cell-inducing adjuvant and show that LNP formulations are potentially potent adjuvants to enhance the effectiveness of other subunit vaccines.

Analysis of the Immunostimulatory Effects of Cytokine-Expressing Internal Ribosome Entry Site-Based RNA Adjuvants and Their Applications

Developing new adjuvants that can effectively induce humoral and cellular immune responses while broadening the immune response is of great value. In this study, we aimed to develop single-stranded RNA adjuvants expressing (1) granulocyte monocyte colony-stimulating factor or (2) interleukin 18 based on the encephalomyocarditis virus internal ribosome entry site; we also tested their efficacy in combination with ovalbumin or inactivated influenza vaccines. Notably, cytokine-expressing RNA adjuvants increased the expression of antigen-presenting cell activation markers in mice. Specifically, when combined with ovalbumin, RNA adjuvants expressing granulocyte monocyte colony-stimulating factor increased CD4+ T-cell responses, while those expressing interleukin 18 increased CD8+ T-cell responses. Cytokine-expressing RNA adjuvants further increased the frequency of polyclonal T cells with the influenza vaccine and reduced the clinical illness scores and weight loss of mice after viral challenge. Collectively, our results suggest that cytokine-expressing RNA adjuvants can be applied to protein-based or inactivated vaccines to increase their efficacy.

Immunoinformatic based designing of potential immunogenic novel mRNA and peptide-based prophylactic vaccines against H5N1 and H7N9 avian influenza viruses

Influenza viruses are the most common cause of serious respiratory illnesses worldwide and are responsible for a significant number of annual fatalities. Therefore, it is crucial to look for new immunogenic sites that might trigger an effective immune response. In the present study, bioinformatics tools were used to design mRNA and multiepitope-based vaccines against H5N1 and H7N9 subtypes of avian influenza viruses. Several Immunoinformatic tools were employed to extrapolate T and B lymphocyte epitopes of HA and NA proteins of both subtypes. The molecular docking approach was used to dock the selected HTL and CTL epitopes with the corresponding MHC molecules. Eight (8) CTL, four (4) HTL, and Six (6) linear B cell epitopes were chosen for the structural arrangement of mRNA and of peptide-based prophylactic vaccine designs. Different physicochemical characteristics of the selected epitopes fitted with suitable linkers were analyzed. High antigenic, non-toxic, and non-allergenic features of the designed vaccines were noted at a neutral physiological pH. Codon optimization tool was used to check the GC content and CAI value of constructed MEVC-Flu vaccine, which were recorded to be 50.42% and 0.97 respectively. the GC content and CAI value verify the stable expression of vaccine in pET28a + vector. In-silico immunological simulation the MEVC-Flu vaccine construct revealed a high level of immune responses. The molecular dynamics simulation and docking results confirmed the stable interaction of TLR-8 and MEVC-Flu vaccine. Based on these parameters, vaccine constructs can be regarded as an optimistic choice against H5N1 and H7N9 strains of the influenza virus. Further experimental testing of these prophylactic vaccine designs against pathogenic avian influenza strains may clarify their safety and efficacy.Communicated by Ramaswamy H. Sarma.

Flublok Quadrivalent Vaccine Adjuvanted with R-DOTAP Elicits a Robust and Multifunctional CD4 T Cell Response That Is of Greater Magnitude and Functional Diversity Than Conventional Adjuvant Systems

It is clear that new approaches are needed to promote broadly protective immunity to viral pathogens, particularly those that are prone to mutation and escape from antibody-mediated immunity. CD4+ T cells, known to target many viral proteins and highly conserved peptide epitopes, can contribute greatly to protective immunity through multiple mechanisms. Despite this potential, CD4+ T cells are often poorly recruited by current vaccine strategies. Here, we have analyzed a promising new adjuvant (R-DOTAP), as well as conventional adjuvant systems AddaVax with or without an added TLR9 agonist CpG, to promote CD4+ T cell responses to the licensed vaccine Flublok containing H1, H3, and HA-B proteins. Our studies, using a preclinical mouse model of vaccination, revealed that the addition of R-DOTAP to Flublok dramatically enhances the magnitude and functionality of CD4+ T cells specific for HA-derived CD4+ T cell epitopes, far outperforming conventional adjuvant systems based on cytokine EliSpot assays and multiparameter flow cytometry. The elicited CD4+ T cells specific for HA-derived epitopes produce IL-2, IFN-γ, IL-4/5, and granzyme B and have multifunctional potential. Hence, R-DOTAP, which has been verified safe by human studies, can offer exciting opportunities as an immune stimulant for next-generation prophylactic recombinant protein-based vaccines.

Immune Epitopes of SARS-CoV-2 Spike Protein and Considerations for Universal Vaccine Development

Despite the success of global vaccination programs in slowing the spread of COVID-19, these efforts have been hindered by the emergence of new SARS-CoV-2 strains capable of evading prior immunity. The mutation and evolution of SARS-CoV-2 have created a demand for persistent efforts in vaccine development. SARS-CoV-2 Spike protein has been the primary target for COVID-19 vaccine development, but it is also the hotspot of mutations directly involved in host susceptibility and virus immune evasion. Our ability to predict emerging mutants and select conserved epitopes is critical for the development of a broadly neutralizing therapy or a universal vaccine. In this article, we review the general paradigm of immune responses to COVID-19 vaccines, highlighting the immunological epitopes of Spike protein that are likely associated with eliciting protective immunity resulting from vaccination in humans. Specifically, we analyze the structural and evolutionary characteristics of the SARS-CoV-2 Spike protein related to immune activation and function via the TLRs, B cells, and T cells. We aim to provide a comprehensive analysis of immune epitopes of Spike protein, thereby contributing to the development of new strategies for broad neutralization or universal vaccination.

Self-assembling peptides: Perspectives regarding biotechnological applications and vaccine development

Self-assembly involves a set of molecules spontaneously interacting in a highly coordinated and dynamic manner to form a specific supramolecular structure having new and clearly defined properties. Many examples of this occur in nature and many more came from research laboratories, with their number increasing every day via ongoing research concerning complex biomolecules and the possibility of harnessing it when developing new applications. As a phenomenon, self-assembly has been described on very different types of molecules (biomolecules including), so this review focuses on what is known about peptide self-assembly, its origins, the forces behind it, how the properties of the resulting material can be tuned in relation to experimental considerations, some biotechnological applications (in which the main protagonists are peptide sequences capable of self-assembly) and what is yet to be tuned regarding their research and development.

C-Phycocyanin and Phycocyanobilin as a Novel Adjuvant in Hepatitis B Vaccine

Background

Vaccine adjuvants are components that enhance immune responses to an antigen. Given the importance of adjuvants, research on novel adjuvants with higher efficacy and fewer adverse effects remains crucial. Spirulina (Arthrospira sp.), an aqueous, photosynthetic, filamentous, spiral, multicellular microalga also classified as a cyanobacterium, is well known for its high protein content, vitamins, essential fatty acids, and amino acids. C-phycocyanin (C-PC) is one of the most significant proteins in Spirulina.

Objectives

This study aimed to investigate the adjuvant capabilities of three Spirulina-derived substances-Spirulina extract, C-phycocyanin (C-PC), and phycocyanobilin (PCB)-in conjunction with the Hepatitis B surface antigen (HBsAg).

Methods

Vaccine groups received the vaccine and adjuvants three times at two-week intervals, administered either orally or by injection in encapsulated or naked forms. To use the injectable form while preventing antigenic effects from the C-PC protein portion, the PCB portion was isolated and used as an injectable adjuvant.

Results

The highest levels of interferon gamma (IFN-γ) and interleukin 4 (IL-4) stimulation were observed in the naked PCB form with the vaccine. In both oral and injectable forms of PCB and C-PC, results indicated an increased expression of Hepatitis B surface antibodies (HBsAb) in response to the antigen. The absence of a significant difference between C-PC and Spirulina extract in oral form suggested that the adjuvant effect of this microalga was primarily due to the C-PC compound. Additionally, the injectable form of PCB led to the highest HBsAb expression level. This enhancement of the humoral immune response indicated that these compounds have potential as adjuvants in both oral and injectable forms.

Conclusions

These findings suggest the potential for improved Hepatitis B vaccine efficacy with this novel adjuvant, paving the way for further evaluation with other vaccines.

Lentinan-functionalized graphene oxide hydrogel as a sustained antigen delivery system for vaccines

Hydrogel has been proven to have the ability to deliver antigens continuously to achieve slow vaccine delivery, which makes it a promising candidate for an adjuvant delivery platform. Meanwhile, graphene oxide (GO) has garnered significant attention due to its good biosafety, excellent surface area and easy modification. However, GO exists as weak colloidal particles and poses challenges in self-assembling into a hydrogel structure. Here, we propose an innovative strategy involving self-assembling lentinan-functionalized graphene oxide hydrogel ((LNT-GO Gel) by simply mixing lentinan (LNT)-functionalized GO with polyethylene imide (PEI), which can simultaneously encapsulate antigens, achieve long-lasting release of antigens and generate excellent adjuvant activity. The results indicated that the LNT-GO Gel can control the release of OVA at the injection site and confer targeted delivering capacity to lymph nodes. And the date demonstrates that LNT-GO Gel displays favorable safety and biodegradability in vivo. Moreover, LNT-GO Gel can enhance the activation and maturation of dendritic cells (DCs) in lymph node, induce stronger OVA-specific antibody response, and promote spleen T lymphocyte differentiation, which underscores that LNT-GO Gel has ability to generate stronger antigen-specific humoral and cellular immune responses. Collectively, these results demonstrate the adjuvant potential of the lentinan-functionalized graphene oxide hydrogel (LNT-GO Gel) for subunit vaccine.

In vivo evaluation of new adjuvant systems based on combination of Salmonella Typhi porins with particulate systems: Liposomes versus polymeric particles

Subunit vaccines that have weak immunogenic activity require adjuvant systems for enhancedcellular and long-acting humoral immune responses. Both lipid-based and polymeric-based particulate adjuvants have been widely investigated to induce the desired immune responses against the subunit vaccines. The adjuvant efficacy of these particulate adjuvants depends upon their physicochemical properties such as particle size, surface charge, shape and their composition. Previously, we showed in vitro effect of adjuvant systems based on combination of chitosan and Salmonella Typhi porins in microparticle or nanoparticle form, which were spherical with positive surface charge. In the present study, we have further developed an adjuvant system based on combination of porins with liposomes (cationic and neutral) and investigated the adjuvant effect of both the liposomal and polymeric systems in BALB/c mice using a model antigen, ovalbumin. Humoral immune responses were determined following priming and booster dose at 15-day intervals. In overall, IgM and IgG levels were induced in the presence of both the liposomal and polymeric adjuvant systems indicating the positive impact of combination with porins. The highest IgM levels were obtained on Day 8, and liposomal adjuvant systems were found to elicit significantly higher IgM levels compared to polymeric systems. IgG levels were increased significantly after booster, particularly more profound with the micro-sized polymeric system when compared to cationic liposomal system with nano-size. Our results demonstrated that the developed particulate systems are promising both as an adjuvant and delivery system, providing enhanced immune responses against subunit antigens, and have the potential for long-term protection.

Long-term safety and immunogenicity of an MF59-adjuvanted spike glycoprotein-clamp vaccine for SARS-CoV-2 in adults aged 18-55 years or ≥56 years: 12-month results from a randomised, double-blind, placebo-controlled, phase 1 trial

BACKGROUND

We previously demonstrated the safety and immunogenicity of an MF59-adjuvanted COVID-19 vaccine based on the SARS-CoV-2 spike glycoprotein stabilised in a pre-fusion conformation by a molecular clamp using HIV-1 glycoprotein 41 sequences. Here, we describe 12-month results in adults aged 18-55 years and ≥56 years.

METHODS

Phase 1, double-blind, placebo-controlled trial conducted in Australia (July 2020-December 2021; ClinicalTrials.govNCT04495933; active, not recruiting). Healthy adults (Part 1: 18-55 years; Part 2: ≥56 years) received two doses of placebo, 5 μg, 15 μg, or 45 μg vaccine, or one 45 μg dose of vaccine followed by placebo (Part 1 only), 28 days apart (n = 216; 24 per group). Safety, humoral immunogenicity (including against virus variants), and cellular immunogenicity were assessed to day 394 (12 months after second dose). Effects of subsequent COVID-19 vaccination on humoral responses were examined.

FINDINGS

All two-dose vaccine regimens were well tolerated and elicited strong antigen-specific and neutralising humoral responses, and CD4+ T-cell responses, by day 43 in younger and older adults, although cellular responses were lower in older adults. Humoral responses waned by day 209 but were boosted in those receiving authorised vaccines. Neutralising activity against Delta and Omicron variants was present but lower than against the Wuhan strain. Cross-reactivity in HIV diagnostic tests declined over time but remained detectable in most participants.

INTERPRETATION

The SARS-CoV-2 molecular clamp vaccine is well tolerated and evokes robust immune responses in adults of all ages. Although the HIV glycoprotein 41-based molecular clamp is not being progressed, the clamp concept represents a viable platform for vaccine development.

FUNDING

This study was funded by the Coalition for Epidemic Preparedness Innovations, the National Health and Medical Research Council of Australia, and the Queensland Government.

Immune Epitopes of SARS-CoV-2 Spike Protein and Considerations for Universal Vaccine Development

Despite the success of global vaccination programs in slowing the spread of COVID-19, these efforts have been hindered by the emergence of new SARS-CoV-2 strains capable of evading prior immunity. The mutation and evolution of SARS-CoV-2 have created a demand for persistent efforts in vaccine development. SARS-CoV-2 Spike protein has been the primary target for COVID-19 vaccine development, but it is also the hotspot of mutations directly involved in host susceptibility and immune evasion. Our ability to predict emerging mutants and select conserved epitopes is critical for the development of a broadly neutralizing therapy or a universal vaccine. In this article, we review the general paradigm of immune responses to COVID-19 vaccines, highlighting the immunological epitopes of Spike protein that are likely associated with eliciting protective immunity resulting from vaccination. Specifically, we analyze the structural and evolutionary characteristics of the SARS-CoV-2 Spike protein related to immune activation and function via the toll-like receptors (TLRs), B cells, and T cells. We aim to provide a comprehensive analysis of immune epitopes of Spike protein, thereby contributing to the development of new strategies for broad neutralization or universal vaccination.

Protocol for preparing murine tissue for comparative proteomics study of vaccine adjuvant mechanisms

Understanding the mechanisms of action of adjuvants at the tissue level is crucial to the development of more potent and safer versions for human use. Comparative tissue proteomics presents a novel tool to study their unique action mechanisms. Here, we present a protocol for preparing murine tissue for comparative proteomics study of vaccine adjuvant mechanisms. We describe steps for adjuvant treatment in live animals, tissue harvesting, and homogenization. We then detail protein extraction and digestion to prepare for liquid chromatography-tandem mass spectrometry analysis. For complete details on the use and execution of this protocol, please refer to Li et al.1.

Investigation of a subunit protein vaccine for HFRS based on a consensus sequence between envelope glycoproteins of HTNV and SEOV

Due to the global resurgence of hemorrhagic fever with renal syndrome (HFRS), more attention is being focused on this dangerous illness. In China and Korea, the only vaccines available are the virus-inactivated vaccine against Hantaan virus (HTNV) or Seoul virus (SEOV), but their efficacy and safety are inadequate. Therefore, it is important to develop new vaccines that are safer and more efficient to neutralize and regulate areas with a high prevalence of HFRS. We employed bioinformatics methods to design a recombinant protein vaccine based on conserved regions of protein consensus sequences in HTNV and SEOV membranes. The S2 Drosophila expression system was utilized to enhance protein expression, solubility and immunogenicity. After the Gn and Gc proteins of HTNV and SEOV were successfully expressed, mice were immunized, and the humoral immunity, cellular immunity, and in vivo protection of the HFRS universal subunit vaccine were systematically evaluated in mouse models. These results indicated that the HFRS subunit vaccine generated elevated levels of binding and neutralizing antibodies, particularly IgG1, compared to that of the traditional inactivated HFRS vaccine. Additionally, the spleen cells of immunized mice secreted IFN-r and IL-4 cytokines effectively. Moreover, the HTNV-Gc protein vaccine successfully protected suckling mice from HTNV infection and stimulated GC responses. In this research, a new scientific approach is investigated to develop a universal HFRS subunit protein vaccine that is capable of producing effective humoral and cellular immunity in mice. The results suggest that this vaccine could be a promising candidate for preventing HFRS in humans.

Self-Adjuvanting Calcium-Phosphate-Coated Microcrystal-Based Vaccines Induce Pyroptosis in Human and Livestock Immune Cells

Successful vaccines require adjuvants able to activate the innate immune system, eliciting antigen-specific immune responses and B-cell-mediated antibody production. However, unwanted secondary effects and the lack of effectiveness of traditional adjuvants has prompted investigation into novel adjuvants in recent years. Protein-coated microcrystals modified with calcium phosphate (CaP-PCMCs) in which vaccine antigens are co-immobilised within amino acid crystals represent one of these promising self-adjuvanting vaccine delivery systems. CaP-PCMCs has been shown to enhance antigen-specific IgG responses in mouse models; however, the exact mechanism of action of these microcrystals is currently unclear. Here, we set out to investigate this mechanism by studying the interaction between CaP-PCMCs and mammalian immune cells in an in vitro system. Incubation of cells with CaP-PCMCs induced rapid pyroptosis of peripheral blood mononuclear cells and monocyte-derived dendritic cells from cattle, sheep and humans, which was accompanied by the release of interleukin-1β and the activation of Caspase-1. We show that this pyroptotic event was cell-CaP-PCMCs contact dependent, and neither soluble calcium nor microcrystals without CaP (soluble PCMCs) induced pyroptosis. Our results corroborate CaP-PCMCs as a promising delivery system for vaccine antigens, showing great potential for subunit vaccines where the enhancement or find tuning of adaptive immunity is required.

Solidified saturated fats coating subunit vaccines greatly extended vaccine booster release and contributed to a Th1/Th2 mixed immune response in mice

Delayed release of vaccine coupled with a soluble vaccine acts as a primer and a booster with only a single administration, which would be very beneficial to livestock producers. We developed a subdermal pellet consisting of solid-phase pure stearic acid (SA) or palmitic acid (PA) that was used to encapsulate a small volume liquid vaccine consisting of fluorescently labeled *Ovalbumin (Cy5-*OVA) formulated with Emulsigen-D +/- Poly I:C (EMP) adjuvants. Mice were also immunized via the subcutaneous route with Cy5-*OVA-EMP (soluble liquid). The vaccine leached out of the pellet with very little dissolution of the fat itself resulting in the sustained subdermal delivery of antigens and adjuvants. Cy5-*OVA was still visible 60 days post administration in mice immunized with stearic acid-coated or palmitic acid-coated pellets. In these mice, persistently high IgG1 and IgG2a antibody titres were detected as well as significant IFNγ production at least 60 days post-injection. These responses were significantly higher than those observed after a single subcutaneous injection of the vaccine. A repeat trial with the pellets alone +/- the soluble vaccine showed comparable immune responses after surgical implantation of the pellet, suggesting that pellet alone may be sufficient. The PA-coated vaccines led to dermal inflammation in the mice that would limit usefulness of this vehicle, but this was largely absent when SA was used to coat the pellets. These data suggest that the SA-coated adjuvanted vaccine prolonged the release of the vaccine and triggered a comparable immune response to the mice that received the two liquid injections, and a single pellet vaccine should be tested as a novel immunization method for livestock.

Roles and Mechanisms of NLRP3 in Influenza Viral Infection

Pathogenic viral infection represents a major challenge to human health. Due to the vast mucosal surface of respiratory tract exposed to the environment, host defense against influenza viruses has perpetually been a considerable challenge. Inflammasomes serve as vital components of the host innate immune system and play a crucial role in responding to viral infections. To cope with influenza viral infection, the host employs inflammasomes and symbiotic microbiota to confer effective protection at the mucosal surface in the lungs. This review article aims to summarize the current findings on the function of NACHT, LRR and PYD domains-containing protein 3 (NLRP3) in host response to influenza viral infection involving various mechanisms including the gut-lung crosstalk.

Immunogenicity and efficacy analyses of EPC002, ECA006, and EPCP009 protein subunit combinations as tuberculosis vaccine candidates

Tuberculosis (TB) is the leading cause of death from infectious diseases worldwide, and developing a new TB vaccine is a priority for TB control. Combining multiple immunodominant antigens to form a novel multicomponent vaccine with broad-spectrum antigens to induce protective immune responses is a trend in TB vaccine development. In this study, we used T-cell epitope-rich protein subunits to construct three antigenic combinations: EPC002, ECA006, and EPCP009. Fusion expression of purified protein EPC002f (CFP-10-linker-ESAT-6-linker-nPPE18), ECA006f (CFP-10-linker-ESAT-6-linker-Ag85B), and EPCP009f (CFP-10-linker-ESAT-6-linker-nPPE18-linker-nPstS1) and recombinant purified protein mixtures EPC002m (mix of CFP-10, ESAT-6, and nPPE18), ECA006m (mix of CFP-10, ESAT-6, and Ag85B), and EPCP009m (mix of CFP-10, ESAT-6, nPPE18, and nPstS1) were used as antigens, formulated with alum adjuvant, and the immunogenicity and efficacy were analyzed using immunity experiments with BALB/c mice. All protein-immunized groups elicited higher levels of humoral immunity, including IgG and IgG1. The IgG2a/IgG1 ratio of the EPCP009m-immunized group was the highest, followed by that of the EPCP009f-immunized group, which was significantly higher than the ratios of the other four groups. The multiplex microsphere-based cytokine immunoassay revealed that EPCP009f and EPCP009m induced the production of a wider range of cytokines than EPC002f, EPC002m, ECA006f, and ECA006m, which included Th1-type (IL-2, IFN-γ, TNF-α), Th2-type (IL-4, IL-6, IL-10), Th17-type (IL-17), and other proinflammatory cytokines (GM-CSF, IL-12). The enzyme-linked immunospot assays demonstrated that the EPCP009f- and EPCP009m-immunized groups had significantly higher amounts of IFN-γ than the other four groups. The in vitro mycobacterial growth inhibition assay demonstrated that EPCP009m inhibited Mycobacterium tuberculosis (Mtb) growth most strongly, followed by EPCP009f, which was significantly better than that of the other four vaccine candidates. These results indicated that EPCP009m containing four immunodominant antigens exhibited better immunogenicity and Mtb growth inhibition in vitro and may be a promising candidate vaccine for the control of TB.

Fluorine-Functionalized Polyphosphazene Immunoadjuvant: Synthesis, Solution Behavior and In Vivo Potency

The inclusion of fluorine motifs in drugs and drug delivery systems is an established tool for modulating their biological potency. Fluorination can improve drug specificity or boost the vehicle's ability to cross cellular membranes. However, the approach has yet to be applied to vaccine adjuvants. Herein, the synthesis of fluorinated bioisostere of a clinical stage immunoadjuvant-poly[di(carboxylatophenoxy)phosphazene], PCPP-is reported. The structure of water-soluble fluoropolymer-PCPP-F, which contains two fluorine atoms per repeat unit-was confirmed using 1H, 31P and 19F NMR, and its molecular mass and molecular dimensions were determined using size-exclusion chromatography and dynamic light scattering. Insertion of fluorine atoms in the polymer side group resulted in an improved solubility in acidic solutions and faster hydrolytic degradation rate, while the ability to self-assemble with an antigenic protein, lysozyme-an important feature of polyphosphazene vaccine adjuvants-was preserved. In vivo assessment of PCPP-F demonstrated its greater ability to induce antibody responses to Hepatitis C virus antigen when compared to its non-fluorinated counterpart. Taken together, the superior immunoadjuvant activity of PCPP-F, along with its improved formulation characteristics, demonstrate advantages of the fluorination approach for the development of this family of macromolecular vaccine adjuvants.

Identification and characterization of miRNAs in spleens of sheep subjected to repetitive vaccination

Accumulative evidence has shown that short non-coding RNAs such as miRNAs can regulate the innate and adaptive immune responses. Aluminium hydroxide is a commonly used adjuvant in human and veterinary vaccines. Despite its extended use, its mechanism of action is not fully understood and very few in vivo studies have been done to enhance understanding at the molecular level. In this work, we took advantage of a previous long-term experiment in which lambs were exposed to three different treatments by parallel subcutaneous inoculations with aluminium-containing commercial vaccines, an equivalent dose of aluminium or mock injections. Spleen samples were used for miRNA-seq. A total of 46 and 16 miRNAs were found differentially expressed when animals inoculated with commercial vaccines or the adjuvant alone were compared with control animals, respectively. Some miRNAs previously related to macrophage polarization were found dysregulated exclusively by the commercial vaccine treatment but not in the aluminium inoculated animals. The dysregulated miRNAs in vaccine group let-7b-5p, miR-29a-3p, miR-27a and miR-101-3p are candidates for further research, since they may play key roles in the immune response induced by aluminium adjuvants added to vaccines. Finally, protein-protein interaction network analysis points towards leucocyte transendothelial migration as a specific mechanism in animals receiving adjuvant only.

Adjuvants approved for human use: What do we know and what do we need to know for designing good adjuvants?

Adjuvants represent one of the most significant biotechnological solutions regarding vaccine development, thereby broadening the amount of candidates which can now be used and tested in vaccine formulations targeting various pathogens, as antigens which were previously discarded due to their low or null immunogenicity can now be included. Adjuvant development research has grown side-by-side with an increasing body of knowledge regarding immune systems and their recognition of foreign microorganisms. Alum-derived adjuvants were used in human vaccines for many years, even though complete understanding of their vaccination-related mechanism of action was lacking. The amount of adjuvants approved for human use has increased recently in line with attempts to interact with and stimulate the immune system. This review is aimed at summarising what is known about adjuvants, focusing on those approved for use in humans, their mechanism of action and why they are so necessary for vaccine candidate formulations; it also discusses what the future may hold in this growing research field.

Virus-like Magnetic Mesoporous Silica Particles as a Universal Vaccination Platform against Pathogenic Infections

Vaccination is the most important way of population protection from life-threatening pathogenic infections. However, its efficiency is frequently compromised by a failure of strong antigen presentation and immune activation. Herein, we developed virus-like magnetic mesoporous silica nanoparticles as a universal vaccination platform (termed MagParV) for preventing pathogenic infections. This platform was constructed by integrating synthetic biology-based endoplasmic reticulum-targeting vesicles with magnetic mesoporous silica particles. This platform exhibited high antigen-loading capacity, strongly targeting the endoplasmic reticulum and promoting antigen presentation in dendritic cells. After prime-boost vaccination, the antigen-loading MagParV with AMF drastically elicited specific antibody production against corresponding antigens of fungal, bacterial, and viral pathogens. A systemic infection model further revealed that the platform effectively protected the mice from severe fungal systemic infections. This study realized synthetic biology-facilitated green manufacturing of vaccines, which is promising for magnetism-activated vaccination against different kinds of pathogenic infections.

A NF-κB-Based High-Throughput Screening for Immune Adjuvants and Inhibitors

The nuclear factor-κB (NF-κB) family is crucial for regulating immune and inflammatory responses. The activation of the immune cell signaling pathway usually activates NF-κB, causing a protective immune response. NF-κB can also cause excessive inflammatory responses by activating a cascade reaction of pro-inflammatory mediators such as cytokines. In this study, we used an NF-κB luciferase reporter gene system. Out of more than 800 compounds screened, four NF-κB agonists were identified with strong activity at nontoxic concentrations. Subsequently, the adjuvant effect was verified on mouse bone marrow-derived dendritic cells (BMDCs) and macrophages RAW264.7. It was found that fostamatinib (R788) disodium increased the production of IL-6, IL-12p40, and TNF-α, indicating that R788 disodium could induce the maturation of antigen-presenting cells (APCs). In addition, three compounds were screened to significantly inhibit NF-κB at nontoxic doses, including dehydrocostus lactone (DHL)-a known NF-κB inhibitor. The results showed that DHL significantly reduced the release of LPS-induced inflammatory cytokines (including TNF-α, IL-6, and IL-12). Our findings indicate that the NF-κB-based high-throughput screening can be used to discover potential immune adjuvants and anti-inflammatory molecules.

Mn-based cGAS-STING activation for tumor therapy

Immunotherapy has efficiently revolutionized the treatment of human neoplastic diseases. However, the overall responsive rate of current immunotherapy is still unsatisfactory, benefiting only a small proportion of patients. Therefore, significant attention has been paid to the modulation of tumor microenvironment (TME) for the enhancement of immunotherapy. Interestingly, recent studies have shown that cyclic GMP-AMP synthase-stimulator of interferon gene (cGAS-STING) was initially found as an innate immune sensor to recognize cytoplasmic DNA (such as bacterial, viral, micronuclei, and mitochondrial). It is a promising signaling pathway to activate antitumor immune responses via type I interferon production. Notably, Mn²⁺ was found to be a critical molecule to sensitize the activation of the cGAS-STING pathway for better immunotherapy. This activation led to the development of Mn²⁺-based strategies for tumor immunotherapy via the activation of the cGAS-STING pathway. In this critical review, we aimed to summarize the recent progress of this field, focusing on the following three aspects. First, we briefly introduced the signaling pathway of cGAS-STING activation, and its regulation effect on the antitumor immunity cycle has been discussed. Along with this, several agonists of the cGAS-STING pathway were introduced with their potential as immunotherapeutic drugs. Then, the basic biological functions of Mn²⁺ have been illustrated, focusing on its critical roles in the cGAS-STING pathway activation. Next, we systematically reviewed the Mn²⁺-based strategies for tumor immunotherapy, which can be classified by the methods based on Mn²⁺ alone or Mn²⁺ combined with other therapeutic modalities. We finally speculated the future perspectives of the field and provided rational suggestions to develop better Mn²⁺-based therapeutics.

Emerging adjuvants for intradermal vaccination

The majority of vaccines have been delivered into the muscular tissue. Skin contains large amounts of antigen-presenting cells and has been recognized as a more immunogenic site for vaccine delivery. Intradermal delivery has been approved to improve influenza vaccine efficacy and spare influenza vaccine doses. In response to the recent monkeypox outbreak, intradermal delivery has been also approved to stretch the limited monkeypox vaccine doses to immunize more people at risk. Incorporation of vaccine adjuvants is promising to further increase intradermal vaccine efficacy and spare more vaccine doses. Yet, intradermal vaccination is associated with more significant local reactions than intramuscular vaccination. Thus, adjuvants suitable to boost intradermal vaccination need to have a good local safety without inducing overt local reactions. This review introduces currently approved adjuvants in licensed human vaccines and their relative reactogenicity for intradermal delivery and then introduces emerging chemical and physical adjuvants with a good local safety to boost intradermal vaccination. The rational to develop physical adjuvants, the types of physical adjuvants, and the unique advantages of physical adjuvants to boost intradermal vaccination are also introduced in this review.

Comparative tissue proteomics reveals unique action mechanisms of vaccine adjuvants

Radiofrequency adjuvant (RFA) was recently developed to boost influenza vaccination without the safety concerns of chemical adjuvants due to their physical nature. Yet, the action mechanisms of RFA remain largely unknown. Omics techniques offer new opportunities to identify molecular mechanisms of RFA. This study utilized comparative tissue proteomics to explore molecular mechanisms of the physical RFA. Comparison of RFA and chemical adjuvant (Alum, AddaVax, MPL, MPL/Alum)-induced tissue proteome changes identified 14 exclusively induced proteins by RFA, among which heat shock protein (HSP) 70 was selected for further analysis due to its known immune-modulating functions. RFA showed much weakened ability to boost ovalbumin and pandemic influenza vaccination in HSP70 knockout than wild-type mice, hinting crucial roles of HSP70 in RFA effects. This study supports comparative tissue proteomics to be an effective tool to study molecular mechanisms of vaccine adjuvants.

Effective adjuvantation of nanograms of influenza vaccine and induction of cross-protective immunity by physical radiofrequency adjuvant

Novel adjuvants are highly demanded to aid in development of improved or new vaccines against existing or emerging infectious diseases. Considering commonly used Alum and MF59 adjuvants induce tissue stress and release of endogenous danger signals to mediate their adjuvant effects, physical modalities may be used to induce tissue stress and endogenous danger signal release to enhance vaccine-induced immune responses. Furthermore, physical adjuvants are less likely to induce significant systemic adverse reactions due to their localized effects. Recently we found non-invasive radiofrequency (RF) pretreatment of the skin could significantly enhance intradermal vaccine-induced immune responses in murine models that included pandemic influenza vaccine, pre-pandemic vaccine, and influenza internal antigen vaccine. It remained to be explored whether the physical RF adjuvant (RFA) could be used to boost seasonal influenza vaccination, spare vaccine doses, and induce cross-protective immunity. This study found the physical RFA could significantly enhance seasonal influenza vaccine-induced immune responses against each viral strain and robustly enhance low-dose (nanograms) H3N2 vaccine-induced immune responses and protection in murine models. RFA also induced cross-protective immunity against heterologous and heterosubtypic influenza viruses. Further studies found heat shock protein 70 (inducible endogenous danger signal) and myeloid differentiation primary response 88 adaptor played a crucial role in dose-sparing effects of RFA. These data strongly support further development of the physical RFA to boost influenza vaccination.

Single-stranded RNA adjuvant enhances the efficacy of 10-valent human papilloma virus-like particle vaccine

Following the development of various types of vaccines, the use of adjuvants to boost vaccine efficacy has become a focus of research. Aluminum hydroxide (alum), the most commonly used adjuvant, induces a certain immune response and ensures safety in human trials. However, alum mainly induces only a Th2 response; its Th1 response is weak. Thus, we previously developed a single-stranded ribose nucleic acid (ssRNA) adjuvant that induces a Th1 response through toll-like receptors. Here, we explored whether 10-valent human papilloma virus (HPV)-like particle (VLP) vaccine formulated with ssRNA adjuvant and alum helped enhance immune response and maintained memory response. The mice were immunized intramuscularly twice at 2-week intervals and were inoculated 4 days after the second boost (after about 1 year). Antibody response and T cell activation were measured by Elispot, ELISA using harvested serum and splenocytes. 10-valent HPV VLP vaccine formulated with ssRNA adjuvant and alum increased antigen-specific immune response than alum used alone. It increased each type-specific IgG1/IgG2c titers, and antigen-specific IFN-γ cells. Furthermore, the ssRNA adjuvant with alum induced memory response. In memory response, each type-specific IgG1/IgG2c, IFN-γ, and IL-6 cytokines, and neutralizing antibodies were increased by the ssRNA adjuvant with alum. Overall, the ssRNA adjuvant with alum induced memory responses and balanced Th1/Th2 responses. The ssRNA adjuvant and alum may help to enhanced prophylactic vaccine efficacy. This article is protected by copyright. All rights reserved.

Modulation of dendritic cell metabolism by an MPLA-adjuvanted allergen product for specific immunotherapy

Background

Recently, bacterial components were shown to enhance immune responses by shifting immune cell metabolism towards glycolysis and lactic acid production, also known as the Warburg Effect. Currently, the effect of allergen products for immunotherapy (AIT) and commercial vaccines on immune cell metabolism is mostly unknown.

Objective

To investigate the effect of AIT products (adjuvanted with either MPLA or Alum) on myeloid dendritic cell (mDC) metabolism and activation.

Methods

Bone marrow-derived mDCs were stimulated with five allergoid-based AIT products (one adjuvanted with MPLA, four adjuvanted with Alum) and two MPLA-adjuvanted vaccines and analyzed for their metabolic activation, expression of cell surface markers, and cytokine secretion by ELISA. mDCs were pre-incubated with either immunological or metabolic inhibitors or cultured in glucose- or glutamine-free culture media and subsequently stimulated with the MPLA-containing AIT product (AIT product 1). mDCs were co-cultured with allergen-specific CD4+ T cells to investigate the contribution of metabolic pathways to the T cell priming capacity of mDCs stimulated with AIT product 1.

Results

Both the MPLA-containing AIT product 1 and commercial vaccines, but not the Alum-adjuvanted AIT products, activated Warburg metabolism and TNF-α secretion in mDCs. Further experiments focused on AIT product 1. Metabolic analysis showed that AIT product 1 increased glycolytic activity while also inducing the secretion of IL-1β, IL-10, IL-12, and TNF-α. Both rapamycin (mTOR-inhibitor) and SP600125 (SAP/JNK MAPK-inhibitor) dose-dependently suppressed the AIT product 1-induced Warburg Effect, glucose consumption, IL-10-, and TNF-α secretion. Moreover, both glucose- and glutamine deficiency suppressed secretion of all investigated cytokines (IL-1β, IL-10, and TNF-α). Glucose metabolism in mDCs was also critical for the (Th1-biased) T cell priming capacity of AIT product 1-stimulated mDCs, as inhibition of mTOR signaling abrogated their ability to induce Th1-responses.

Conclusion

The AIT product and commercial vaccines containing the adjuvant MPLA were shown to modulate the induction of immune responses by changing the metabolic state of mDCs. Better understanding the mechanisms underlying the interactions between cell metabolism and immune responses will allow us to further improve vaccine development and AIT.

Safety and Efficacy of the Bordetella bronchiseptica Vaccine Combined with a Vegetable Oil Adjuvant and Multi-Omics Analysis of Its Potential Role in the Protective Response of Rabbits

Infectious respiratory diseases caused by Bordetella bronchiseptica (Bb) are seriously endangering the development of the rabbit industry in China. Unfortunately, no licensed vaccines are available for this pathogen. The present study was designed to determine whether the inactivated Bb antigen formulated with vegetable oil adjuvant (named E515) which contains soybean oil, vitamin E, and ginseng saponins, functions as a safe and effective vaccine (E515-Bb) against Bb infection in rabbits. Based on local and systemic reactions, both the E515 adjuvant alone and the E515-Bb vaccine exhibited good safety in rabbits. Immune response analysis implies that rabbits immunized with the E515-Bb vaccine produced significantly higher, earlier, and longer-lasting specific antibody responses and activated Th1/Th2/Th17 cell responses than those immunized with the aluminum hydroxide (Alum)-adjuvanted Bb vaccine (Alum-Bb) or Bb antigen alone. Moreover, the E515-Bb vaccine effectively protected rabbits from Bb infection. Additionally, integrated multi-omics analysis revealed that the immunoprotective effect of the E515-Bb vaccine was achieved through upregulation of the complement and coagulation cascades and cell adhesion molecule (CAM) pathways, and the downregulation of the P53 pathway. Overall, these results indicate that the E515-Bb vaccine is safe, elicits an efficient immune response and provides good protection against Bb infection in rabbits. Thus, the E515-adjuvanted Bb vaccine can be considered a promising candidate vaccine for preventing Bb infection.

Transient production of receptor-binding domain of SARS-CoV-2 in Nicotiana benthamiana plants induces specific antibodies in immunized mice

BACKGROUND

The COVID-19 pandemic caused by the SARS-CoV-2 coronavirus has currently affected millions of people around the world. To combat the rapid spread of COVID-19 there is an urgent need to implement technological platforms for the production of vaccines, drugs and diagnostic systems by the scientific community and pharmaceutical companies. The SARS-CoV-2 virus enters the cells by the interaction between the receptor-binding domain (RBD) present in the viral surface spike protein and its human receptor ACE2. The RBD protein is therefore considered as the target for potential subunit-based vaccines.

METHODS AND RESULTS

We evaluate the use of Nicotiana benthamiana plants as the host to transiently-producing recombinant RBD (RBDr) protein. The identity of the plant-produced RBDr was confirmed by immune assays and mass spectrometry. Immunogenicity was confirmed through the specific antibodies generated in all of the immunized mice compared to the PBS treated group.

CONCLUSIONS

In conclusions, the immunogenicity of the RBDr produced in N. benthamiana was confirmed. These findings support the use of plants as an antigen expression system for the rapid development of vaccine candidates.

Precise immunological evaluation rationalizes the design of a self-adjuvanting vaccine composed of glycan antigen, TLR1/2 ligand, and T-helper cell epitope

Sialyl-Tn (STn), overexpressed on various tumors, has been investigated for its application in anti-cancer vaccine therapy. However, Theratope, an STn-based vaccine, failed in the phase III clinical trial due to poor immunogenicity and epitope suppression by the foreign carrier protein. We therefore developed a self-adjuvanting STn based-vaccine, a conjugate of clustered STn (triSTn) antigen, TLR1/2 ligand (Pam3CSK4), and T-helper (Th) cell epitope, and found that this three-component self-adjuvanting vaccine effectively resulted in the production of anti-triSTn IgG antibodies. We herein analyzed immune responses induced by this self-adjuvanting vaccine in detail. We newly synthesized two-component vaccines, i.e., Pam3CSK4- or Th epitope-conjugated triSTn, as references to evaluate the immune-stimulating functions of Pam3CSK4 and Th epitope. Immunological evaluation of the synthesized vaccine candidates revealed that Pam3CSK4 was essential for antibody production, indicating that the uptake of triSTn antigen by antigen-presenting cells (APCs) was promoted by the recognition of Pam3CSK4 by TLR1/2. The function of the Th epitope was also confirmed. Th cell activation was important for boosting antibody production and IgG subclass switching. Furthermore, flow cytometric analyses of immune cells, including T cells, B cells, dendritic cells, and other monocytes, were first employed in the evaluation of self-adjuvanting vaccines and revealed that the three-component vaccine was able to induce antigen-specific immune responses for efficient antibody production without excessive inflammatory responses. Importantly, the co-administration of Freund's adjuvants was suggested to cause excessive myeloid cell accumulation and decreased plasma cell differentiation. These results demonstrate that vaccines can be designed to achieve the desired immune responses via the bottom-up construction of each immune element.

Two Conserved Phenylalanine Residues in the E1 Fusion Loop of Alphaviruses Are Essential for Viral Infectivity

Alphaviruses infect cells by a low pH-dependent fusion reaction between viral and host cell membranes that is mediated by the viral E1 glycoprotein. Most reported alphavirus E1 sequences include two phenylalanines (F87 and F95) in the fusion loop, yet the role of these residues in viral infectivity remains to be defined. Following introduction of wild type (WT), E1-F87A, and E1-F95A chikungunya virus (CHIKV) RNA genomes into cells, viral particle production was similar in magnitude. However, CHIKV E1-F87A and E1-F95A virions displayed impaired infectivity compared with WT CHIKV particles. Although WT, E1-F87A, and E1-F95A particles bound cells with similar efficiencies, E1-F87A and E1-F95A particles were unable to undergo fusion and entry into cells. Introduction of an F95A mutation in the E1 fusion loop of Mayaro virus or Venezuelan equine encephalitis virus also resulted in poorly infectious virions. We further tested whether an E1-F87A or E1-F95A mutation could be incorporated into a live-attenuated vaccine strain, CHIKV 181/25, to enhance vaccine safety. Infection of immunocompromised Ifnar1-/- and Irf3-/-Irf5-/-Irf7-/- mice with 181/25E1-F87A or 181/25E1-F95A resulted in 0% mortality, compared with 100% mortality following 181/25 infection. Despite this enhanced attenuation, surviving Ifnar1-/- and Irf3-/-Irf5-/-Irf7-/- mice were protected against virulent virus re-challenge. Moreover, single-dose immunization of WT mice with either 181/25, 181/25E1-F87A, or 181/25E1-F95A elicited CHIKV-specific antibody responses and protected against pathogenic CHIKV challenge. These studies define a critical function for residues E1-F87 and E1-F95 in alphavirus fusion and entry into target cells and suggest that incorporation of these mutations could enhance the safety of live-attenuated alphavirus vaccine candidates. IMPORTANCE Alphaviruses are human pathogens that cause both debilitating acute and chronic musculoskeletal disease and potentially fatal encephalitis. In this study, we determined that two highly conserved phenylalanine residues in the alphavirus E1 glycoprotein are required for fusion of viral and host cell membranes and viral entry into target cells. We further demonstrated that mutation of these phenylalanines results in a substantial loss of viral virulence but not immunogenicity. These data enhance an understanding of the viral determinants of alphavirus entry into host cells and could contribute to the development of new antivirals targeting these conserved phenylalanines or new live-attenuated alphavirus vaccines.

Vaccination against Atherosclerosis: Is It Real?

Atherosclerosis has been known in medicine for several centuries. As early as 1755, the Swedish anatomist Albrecht von Haller used the term "atheroma" to describe vascular lesions. Atherosclerosis may originate from an unbalanced diet or bad habits, and is mainly found in developed countries. Clinical trials have been conducted to establish the causes of atherosclerosis, and also to develop treatments for this disease. However, prevention of the disease has always been better than treatment, so vaccination may be the key to saving thousands of lives. The creation of a vaccine may be directly related to the study of autoimmune processes occurring in the body, immunity. This review considers the issues related to the involvement of the immune response in the development of atherosclerotic lesions. Modern concepts of atherogenesis, immune inflammation in atherosclerosis, and potential vaccine targets are also discussed. There is a particular focus on experimental and clinical data supporting the development of immune therapies to reduce cardiovascular risk.

Recent Advances in the Development of Toll-like Receptor Agonist-Based Vaccine Adjuvants for Infectious Diseases

Vaccines are powerful tools for controlling microbial infections and preventing epidemic diseases. Efficient inactive, subunit, or viral-like particle vaccines usually rely on a safe and potent adjuvant to boost the immune response to the antigen. After a slow start, over the last decade there has been increased developments on adjuvants for human vaccines. The development of adjuvants has paralleled our increased understanding of the molecular mechanisms for the pattern recognition receptor (PRR)-mediated activation of immune responses. Toll-like receptors (TLRs) are a group of PRRs that recognize microbial pathogens to initiate a host’s response to infection. Activation of TLRs triggers potent and immediate innate immune responses, which leads to subsequent adaptive immune responses. Therefore, these TLRs are ideal targets for the development of effective adjuvants. To date, TLR agonists such as monophosphoryl lipid A (MPL) and CpG-1018 have been formulated in licensed vaccines for their adjuvant activity, and other TLR agonists are being developed for this purpose. The COVID-19 pandemic has also accelerated clinical research of vaccines containing TLR agonist-based adjuvants. In this paper, we reviewed the agonists for TLR activation and the molecular mechanisms associated with the adjuvants’ effects on TLR activation, emphasizing recent advances in the development of TLR agonist-based vaccine adjuvants for infectious diseases.

Therapeutic DNA Vaccines against HPV-Related Malignancies: Promising Leads from Clinical Trials

In 2014 and 2021, two nucleic-acid vaccine candidates named MAV E2 and VGX-3100 completed phase III clinical trials in Mexico and U.S., respectively, for patients with human papillomavirus (HPV)-related, high-grade squamous intraepithelial lesions (HSIL). These well-tolerated but still unlicensed vaccines encode distinct HPV antigens (E2 versus E6+E7) to elicit cell-mediated immune responses; their clinical efficacy, as measured by HSIL regression or cure, was modest when compared with placebo or surgery (conization), but both proved highly effective in clearing HPV infection, which should help further optimize strategies for enhancing vaccine immunogenicity, toward an ultimate goal of preventing malignancies in millions of patients who are living with persistent, oncogenic HPV infection but are not expected to benefit from current, prophylactic vaccines. The major roadblocks to a highly efficacious and practical product remain challenging and can be classified into five categories: (i) getting the vaccines into the right cells for efficient expression and presentation of HPV antigens (fusion proteins or epitopes); (ii) having adequate coverage of oncogenic HPV types, beyond the current focus on HPV-16 and -18; (iii) directing immune protection to various epithelial niches, especially anogenital mucosa and upper aerodigestive tract where HPV-transformed cells wreak havoc; (iv) establishing the time window and vaccination regimen, including dosage, interval and even combination therapy, for achieving maximum efficacy; and (v) validating therapeutic efficacy in patients with poor prognosis because of advanced, recurrent or non-resectable malignancies. Overall, the room for improvements is still large enough that continuing efforts for research and development will very likely extend into the next decade.

Built-in adjuvants for use in vaccines

Vaccine refers to biological products that are produced using various pathogenic microorganisms for inoculation. The goal of vaccination is to induce a robust immune response against a specific antigen, thus preventing the organism from getting infected. In vaccines, adjuvants have been widely employed to enhance immunity against specific antigens. An ideal adjuvant should be stable, biodegradable, and low cost, not induce system rejection and promote an immune response. Various adjuvant components have been investigated across diverse applications. Typically, adjuvants are employed to meet the following objectives: (1) to improve the effectiveness of immunization with vaccines for specific populations, such as newborns and the elderly; (2) enhance the immunogenicity of highly purified or recombinant antigens; (3) allow immunization with a smaller dose of the vaccine, reducing drug dosage. In the present review, we primarily focus on chemically synthesized compounds that can be used as built-in adjuvants. We elaborate the classification of these compounds based on the induced immune activation mechanism and summarize their application in various vaccine types.

Adjuvants: Engineering Protective Immune Responses in Human and Veterinary Vaccines

Adjuvants are key components of many vaccines, used to enhance the level and breadth of the immune response to a target antigen, thereby enhancing protection from the associated disease. In recent years, advances in our understanding of the innate and adaptive immune systems have allowed for the development of a number of novel adjuvants with differing mechanisms of action. Herein, we review adjuvants currently approved for human and veterinary use, describing their use and proposed mechanisms of action. In addition, we will discuss additional promising adjuvants currently undergoing preclinical and/or clinical testing.

Tumor associated macrophage and microbe: The potential targets of tumor vaccine delivery

The occurrence and development of tumors depend on the tumor microenvironment (TME), which is made of various immune cells, activated fibroblasts, basement membrane, capillaries, and extracellular matrix. Tumor associated macrophages (TAMs) and microbes are important components in TME. Tumor cells can recruit and educate TAMs and microbes, and the hijacked TAMs and microbes can promote the progression of tumor reciprocally. Tumor vaccine delivery remodeling TME by targeting TAM and microbes can not only enhance the specificity and immunogenicity of antigens, but also contribute to the regulation of TME. Tumor vaccine design benefits from nanotechnology which is a suitable platform for antigen and adjuvant delivery to catalyze new candidate vaccines applying to clinical therapy at unparalleled speed. In view of the characteristics and mechanisms of TME development, vaccine delivery targeting and breaking the malignant interactions among tumor cells, TAMs, and microbes may serve as a novel strategy for tumor therapy.

Generation of a Liposomal Vaccine Adjuvant Based on Sulfated S-Lactosylarchaeol (SLA) Glycolipids

Vaccine formulations utilize adjuvants to enhance the level and breadth of the immune response to a target antigen. Liposomes composed of sulfated S-lactosylarchaeol (SLA) glycolipids can induce strong humoral and cell-mediated antigen-specific immune responses to co-administered antigens in mice. This has been demonstrated with a variety of protein antigens, where the protein is either encapsulated within or simply admixed with the archaeal liposomes (archaeosomes). In this process, a dried film of SLA glycolipid is hydrated in water or antigen solution to generate a large multilamellar (ML) liposomal suspension which is then size reduced by sonication to form unilamellar vesicles (UL) with a narrower size distribution. Herein, we describe the generation of liposomes based on the archaeal-based lipid SLA for use as an adjuvant in vaccine formulations.

Engineered Hydroxyapatite Nanoadjuvants with Controlled Shape and Aspect Ratios Reveal Their Immunomodulatory Potentials

Hydroxyapatite (HAP) has been formulated as adjuvants in vaccines for human use. However, the optimal properties required for HAP nanoparticles to elicit adjuvanticity and the underlying immunopotentiation mechanisms have not been fully elucidated. Herein, a library of HAP nanorods and nanospheres was synthesized to explore the effect of the particle shape and aspect ratio on the immune responses in vitro and adjuvanticity in vivo. It was demonstrated that long aspect ratio HAP nanorods induced a higher degree of cell membrane depolarization and subsequent uptake, and the internalized particles elicited cathepsin B release and mitochondrial reactive oxygen species generation, which further led to pro-inflammatory responses. Furthermore, the physicochemical property-dependent immunostimulation capacities were correlated with their humoral responses in a murine hepatitis B surface antigen immunization model, with long aspect ratio HAP nanorods inducing higher antigen-specific antibody productions. Importantly, HAP nanorods significantly up-regulated the IFN-γ secretion and CD107α expression on CD8⁺ T cells in immunized mice. Further mechanistic studies demonstrated that HAP nanorods with defined properties exerted immunomodulatory effects by enhanced antigen persistence and immune cell recruitments. Our study provides a rational design strategy for engineered nanomaterial-based vaccine adjuvants.

"World in motion" - emulsion adjuvants rising to meet the pandemic challenges

Emulsion adjuvants such as MF59 and AS03 have been used for more than two decades as key components of licensed vaccines, with over 100 million doses administered to diverse populations in more than 30 countries. Substantial clinical experience of effectiveness and a well-established safety profile, along with the ease of manufacturing have established emulsion adjuvants as one of the leading platforms for the development of pandemic vaccines. Emulsion adjuvants allow for antigen dose sparing, more rapid immune responses, and enhanced quality and quantity of adaptive immune responses. The mechanisms of enhancement of immune responses are well defined and typically characterized by the creation of an "immunocompetent environment" at the site of injection, followed by the induction of strong and long-lasting germinal center responses in the draining lymph nodes. As a result, emulsion adjuvants induce distinct immunological responses, with a mixed Th1/Th2 T cell response, long-lived plasma cells, an expanded repertoire of memory B cells, and high titers of cross-neutralizing polyfunctional antibodies against viral variants. Because of these various properties, emulsion adjuvants were included in pandemic influenza vaccines deployed during the 2009 H1N1 influenza pandemic, are still included in seasonal influenza vaccines, and are currently at the forefront of the development of vaccines against emerging SARS-CoV-2 pandemic variants. Here, we comprehensively review emulsion adjuvants, discuss their mechanism of action, and highlight their profile as a benchmark for the development of additional vaccine adjuvants and as a valuable tool to allow further investigations of the general principles of human immunity.