The perfect mix: recent progress in adjuvant research

Induction of protective immune responses at respiratory mucosal sites

Many pathogens enter the host through mucosal sites. Thus, interfering with pathogen entry through local neutralization at mucosal sites therefore is an effective strategy for preventing disease. Mucosally administered vaccines have the potential to induce protective immune responses at mucosal sites. This manuscript delves into some of the latest developments in mucosal vaccination, particularly focusing on advancements in adjuvant technologies and the role of these adjuvants in enhancing vaccine efficacy against respiratory pathogens. It highlights the anatomical and immunological complexities of the respiratory mucosal immune system, emphasizing the significance of mucosal secretory IgA and tissue-resident memory T cells in local immune responses. We further discuss the differences between immune responses induced through traditional parenteral vaccination approaches vs. mucosal administration strategies, and explore the protective advantages offered by immunization through mucosal routes.

The 2nd China Vaccinology Integrated Innovation & Teaching Development Conference: Promoting the construction of vaccinology discipline system

The 2nd China Vaccinology Integrated Innovation & Teaching Development Conference was held in Sun Yat-sen University, Shenzhen, 18-19, November 2023. Over 200 participants in the field of Vaccinology gathered together to address challenges and issues relevant to vaccine education and training courses, research, and public health programs in China. The conference themed "Promoting the Integrated and Innovative Development of Vaccinology through Collective Efforts." The conference was organized by the China Association of Vaccine (CAV) and hosted by Vaccinology Education Professional Committee of CAV, and School of Public Health (Shenzhen), Sun Yat-sen University. Other partners included the Medical Virology Branch of the Chinese Medical Association, the editorial committee of the Chinese Journal of Preventive Medicine, Human Vaccines & Immunotherapeutics, and the People's Medical Publishing House. The 1st conference was held in Hangzhou, in October 2020.

Vaccines and the Eye: Current Understanding of the Molecular and Immunological Effects of Vaccination on the Eye

Vaccination is a public health cornerstone that protects against numerous infectious diseases. Despite its benefits, immunization implications on ocular health warrant thorough investigation, particularly in the context of vaccine-induced ocular inflammation. This review aimed to elucidate the complex interplay between vaccination and the eye, focusing on the molecular and immunological pathways implicated in vaccine-associated ocular adverse effects. Through an in-depth analysis of recent advancements and the existing literature, we explored various mechanisms of vaccine-induced ocular inflammation, such as direct infection by live attenuated vaccines, immune complex formation, adjuvant-induced autoimmunity, molecular mimicry, hypersensitivity reactions, PEG-induced allergic reactions, Type 1 IFN activation, free extracellular RNA, and specific components. We further examined the specific ocular conditions associated with vaccination, such as uveitis, optic neuritis, and retinitis, and discussed the potential impact of novel vaccines, including those against SARS-CoV-2. This review sheds light on the intricate relationships between vaccination, the immune system, and ocular tissues, offering insights into informed discussions and future research directions aimed at optimizing vaccine safety and ophthalmological care. Our analysis underscores the importance of vigilance and further research to understand and mitigate the ocular side effects of vaccines, thereby ensuring the continued success of vaccination programs, while preserving ocular health.

Transmission-Blocking Vaccines against Schistosomiasis Japonica

Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can generate 1000-2200 eggs per day, which is about 3- to 15-fold greater than the egg output of other schistosome species. Bovines (water buffalo and cattle) are the predominant definitive hosts and are estimated to generate up to 90% of parasite eggs released into the environment in rural endemic areas where these hosts and humans are present. Here, we highlight the necessity of developing veterinary transmission-blocking vaccines for bovines to better control the disease and review potential vaccine candidates. We also point out that the approach to producing efficacious transmission-blocking animal-based vaccines before moving on to human vaccines is crucial. This will result in effective and feasible public health outcomes in agreement with the One Health concept to achieve optimum health for people, animals, and the environment. Indeed, incorporating a veterinary-based transmission vaccine, coupled with interventions such as human mass drug administration, improved sanitation and hygiene, health education, and snail control, would be invaluable to eliminating zoonotic schistosomiasis.

Immuno-Enhancing Effect of Ginsenoside Rh2 Liposomes on Foot-and-Mouth Disease Vaccine

The adjuvant is essential for vaccines because it can enhance or directly induce a strong immune response associated with vaccine antigens. Ginsenoside Rh2 (Rh2) had immunomodulatory effects but was limited by poor solubility and hemolysis. In this study, Rh2 liposomes (Rh2-L) were prepared by ethanol injection methods. The Rh2-L effectively dispersed in a double emulsion adjuvant system to form a Water-in-Oil-in-Water (W/O/W) emulsion and had no hemolysis. The physicochemical properties of the adjuvants were tested, and the immune activity and auxiliary effects indicated by the Foot-and-Mouth disease (FMDV) antigen were evaluated. Compared with the mice vaccinated with the FMD vaccine prepared with the double emulsion adjuvant alone, those with the FMD vaccine prepared with the double emulsion adjuvant containing Rh2-L had significantly higher neutralizing antibody titer and splenocyte proliferation rates and showed higher cellular and humoral immune responses. The results demonstrated that Rh2-L could further enhance the immune effect of the double emulsion adjuvant against Foot-and-Mouth Disease.

A Self-Immolative DNA Nanogel Vaccine toward Cancer Immunotherapy

The development of precisely engineered vehicles for intracellular delivery and the controlled release of payloads remains a challenge. DNA-based nanomaterials offer a promising solution based on the A-T-G-C alphabet-dictated predictable assembly and high programmability. Herein, we present a self-immolative DNA nanogel vaccine, which can be tracelessly released in the intracellular compartments and activate the immune response. Three building blocks with cytosine-rich overhang domains are designed to self-assemble into a DNA nanogel framework with a controlled size. Two oligo agonists and one antigen peptide are conjugated to the building blocks via an acid-labile chemical linker. Upon internalization into acidic endosomes, the formation of i-motif configurations leads to dissociation of the DNA nanogel vaccine. The acid-labile chemical linker is cleaved, releasing the agonists and antigen in their traceless original form to activate antigen-presenting cells and an immune response. This study presents a novel strategy for constructing delivery platforms for intracellularly stimuli-triggered traceless release of therapeutics.

Nanoscale coordination polymer synergizes photodynamic therapy and toll-like receptor activation for enhanced antigen presentation and antitumor immunity

While activating antitumor immunity with toll-like receptor (TLR) agonists provides a promising approach toward cancer immunotherapy, existing TLR agonists, including resiquimod (R848), have shown poor tumor selectivity and ineffective TLR activation in tumors for optimal antitumor effects. We hypothesized that improved delivery of TLR agonists to tumors and their effective combination with tumor antigens could significantly enhance their antitumor efficacy. Here, we report a novel nanoscale coordination polymer, Ce6/R848, for the co-delivery of Ce6 photosensitizer to elicit immunogenic cell death via photodynamic therapy (PDT) and cholesterol-conjugated R848 (Chol-R848) for tumor-selective TLR7/8 activation. Upon light irradiation, Ce6-mediated PDT released tumor antigens while selectively delivered R848 activated TLR7/8 in the tumors to synergistically activate antigen-presenting cells and prime T cells for enhanced innate and adaptive antitumor immune responses. Ce6/R848 achieved a 50% cure rate and 99.4% inhibition of tumor growth in subcutaneous MC38 colorectal tumors with minimal systemic toxicity.

Structural informatics approach for designing an epitope-based vaccine against the brain-eating Naegleria fowleri

Primary Amoebic Meningoencephalitis (PAM), a severe lethal brain disease, is caused by a parasite, Naegleria fowleri, also known as the "brain-eating amoeba". The chances of a patient's recovery after being affected by this parasite are very low. Only 5% of people are known to survive this life-threatening infection. Despite the fact that N. fowleri causes a severe, fatal infection, there is no proper treatment available to prevent or cure it. In this context, it is necessary to formulate a potential vaccine that could be able to combat N. fowleri infection. The current study aimed at developing a multi-epitope subunit vaccine against N. fowleri by utilizing immunoinformatics techniques and reverse vaccinology approaches. The T- and B-cell epitopes were predicted by various tools. In order to choose epitopes with the ability to trigger both T- and B-cell-mediated immune responses, the epitopes were put through a screening pipeline including toxicity, antigenicity, cytokine-inductivity, and allergenicity analysis. Three vaccine constructs were designed from the generated epitopes linked with linkers and adjuvants. The modeled vaccines were docked with the immune receptors, where vaccine-1 showed the highest binding affinity. Binding affinity and stability of the docked complex were confirmed through normal mode analysis and molecular dynamic simulations. Immune simulations developed the immune profile, and in silico cloning affirmed the expression probability of the vaccine construct in Escherichia coli (E. coli) strain K12. This study demonstrates an innovative preventative strategy for the brain-eating amoeba by developing a potential vaccine through immunoinformatics and reverse vaccinology approaches. This study has great preventive potential for Primary Amoebic Meningoencephalitis, and further research is required to assess the efficacy of the designed vaccine.

Chemotherapy-Induced Neoantigen Nanovaccines Enhance Checkpoint Blockade Cancer Immunotherapy

Chemotherapeutics have the potential to increase the efficacy of cancer immunotherapies by stimulating the production of damage-associated molecular patterns (DAMPs) and eliciting mutations that result in the production of neoantigens, thereby increasing the immunogenicity of cancerous lesions. However, the dose-limiting toxicity and limited immunogenicity of chemotherapeutics are not sufficient to induce a robust antitumor response. We hypothesized that cancer cells in vitro treated with ultrahigh doses of various chemotherapeutics artificially increased the abundance, variety, and specificity of DAMPs and neoantigens, thereby improving chemoimmunotherapy. The in vitro chemotherapy-induced (IVCI) nanovaccines manufactured from cell lysates comprised multiple neoantigens and DAMPs, thereby exhibiting comprehensive antigenicity and adjuvanticity. Our IVCI nanovaccines exhibited enhanced immune responses in CT26 tumor-bearing mice, with a significant increase in CD4+/CD8+ T cells in tumors in combination with immune checkpoint inhibitors. The concept of IVCI nanovaccines provides an idea for manufacturing and artificial enhancement of immunogenicity vaccines to improve chemoimmunotherapy.

Biogenetic Vesicle-Based Cancer Vaccines with Tunable Surface Potential and Immune Potency

Cancer vaccines are designed to motivate antigen-specific immune responses and facilitate tumor regression with minimal side effects. To fully exert the potential of vaccines, rationally designed formulations that effectively deliver antigens and trigger potent immune reactions are urgently needed. This study demonstrates a simple and controllable vaccine-developing strategy that assembles tumor antigens into bacterial outer membrane vesicles (OMVs), natural delivery vehicles with intrinsic immune adjuvant properties, via electrostatic interaction. This OMV-delivered vaccine (OMVax) stimulated both innate and adaptive immune responses, leading to enhanced metastasis inhibition and prolonged survival of tumor-bearing mice. Moreover, the influence of different surface charged OMVax on antitumor immunity activation is investigated and declined immune response activation occurred with increased positive surface charge. Together, these findings suggest a simple vaccine formulation that can be enhanced by optimizing the surface charges of vaccine formulations.

Vaccine adjuvants: mechanisms and platforms

Adjuvants are indispensable components of vaccines. Despite being widely used in vaccines, their action mechanisms are not yet clear. With a greater understanding of the mechanisms by which the innate immune response controls the antigen-specific response, the adjuvants' action mechanisms are beginning to be elucidated. Adjuvants can be categorized as immunostimulants and delivery systems. Immunostimulants are danger signal molecules that lead to the maturation and activation of antigen-presenting cells (APCs) by targeting Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) to promote the production of antigen signals and co-stimulatory signals, which in turn enhance the adaptive immune responses. On the other hand, delivery systems are carrier materials that facilitate antigen presentation by prolonging the bioavailability of the loaded antigens, as well as targeting antigens to lymph nodes or APCs. The adjuvants' action mechanisms are systematically summarized at the beginning of this review. This is followed by an introduction of the mechanisms, properties, and progress of classical vaccine adjuvants. Furthermore, since some of the adjuvants under investigation exhibit greater immune activation potency than classical adjuvants, which could compensate for the deficiencies of classical adjuvants, a summary of the adjuvant platforms under investigation is subsequently presented. Notably, we highlight the different action mechanisms and immunological properties of these adjuvant platforms, which will provide a wide range of options for the rational design of different vaccines. On this basis, this review points out the development prospects of vaccine adjuvants and the problems that should be paid attention to in the future.

Progress towards Adjuvant Development: Focus on Antiviral Therapy

In recent decades, vaccines have been extraordinary resources to prevent pathogen diffusion and cancer. Even if they can be formed by a single antigen, the addition of one or more adjuvants represents the key to enhance the response of the immune signal to the antigen, thus accelerating and increasing the duration and the potency of the protective effect. Their use is of particular importance for vulnerable populations, such as the elderly or immunocompromised people. Despite their importance, only in the last forty years has the search for novel adjuvants increased, with the discovery of novel classes of immune potentiators and immunomodulators. Due to the complexity of the cascades involved in immune signal activation, their mechanism of action remains poorly understood, even if significant discovery has been recently made thanks to recombinant technology and metabolomics. This review focuses on the classes of adjuvants under research, recent mechanism of action studies, as well as nanodelivery systems and novel classes of adjuvants that can be chemically manipulated to create novel small molecule adjuvants.

Addressing practical issues in the smooth implementation of revised guidelines for non-clinical studies of vaccines for infectious disease prevention

Herein, we investigated possible practical issues for the smooth implementation of the revised Japanese Guidelines for Non-clinical Studies of Vaccines for the Prevention of Infectious Diseases, which were raised in response to public comments on the proposed guideline revision and a gap analysis of the World Health Organization and European Medicines Agency guidelines. We identified main issues such as the non-clinical safety studies of adjuvants and evaluation of local cumulative tolerance in toxicity studies. The revised Japanese Pharmaceuticals and Medical Devices Agency (PMDA)/Ministry of Health, Labour and Welfare (MHLW) guidelines require non-clinical safety studies for vaccines containing new adjuvants, but additional safety pharmacology studies or safety studies in two animal species may be required if non-clinical safety studies raise any concerns (i.e., systemic distribution). Adjuvant biodistribution studies may aid in understanding vaccine characteristics. The evaluation of local cumulative tolerance in non-clinical studies, which was the focus of the Japanese review, can be omitted by including a warning in the package insert to avoid injection to the same site. The study's findings will be reflected in a Q&A to be released by the Japanese MHLW. We hope that this study will contribute to the global and harmonized development of vaccines.

Instigation of the epoch of nanovaccines in cancer immunotherapy

Cancer is an unprecedented proliferation of cells leading to abnormalities in differentiation and maturation. Treatment of primary and metastatic cancer is challenging. In addition to surgery, chemotherapy and radiation therapies have been conventionally used; however, they suffer from severe toxicity and non-specificity. Immunotherapy, the science of programming the body's own defense system against cancer has gained tremendous attention in the last few decades. However, partial immunogenic stimulation, premature degradation and inability to activate dendritic and helper T cells has resulted in limited clinical success. The era of nanomedicine has brought about several breakthroughs in various pharmaceutical and biomedical fields. Hereby, we review and discuss the interplay of tumor microenvironment (TME) and the immunological cascade and how they can be employed to develop nanoparticle-based cancer vaccines and immunotherapies. Nanoparticles composed of lipids, polymers and inorganic materials contain useful properties suitable for vaccine development. Proteinaceous vaccines derived from mammalian viruses, bacteriophages and plant viruses also have unique advantages due to their immunomodulation capabilities. This review accounts for all such considerations. Additionally, we explore how attributes of nanotechnology can be utilized to develop successful nanomedicine-based vaccines for cancer therapy. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

A Brighton Collaboration standardized template with key considerations for a benefit/risk assessment for the Medigen COVID-19 protein vaccine

The Brighton Collaboration Benefit-Risk Assessment of VAccines by TechnolOgy (BRAVATO) Working Group has prepared standardized templates to describe the key considerations for the benefit-risk assessment of several vaccine platform technologies, including protein subunit vaccines. This article uses the BRAVATO template to review the features of the MVC-COV1901 vaccine, a recombinant protein subunit vaccine based on the stabilized pre-fusion SARS-CoV-2 spike protein S-2P, adjuvanted with CpG 1018 and aluminum hydroxide, manufactured by Medigen Vaccine Biologics Corporation in Taiwan. MVC-COV1901 vaccine is indicated for active immunization to prevent COVID-19 caused by SARS-CoV-2 in individuals 12 years of age and older. The template offers details on basic vaccine information, target pathogen and population, characteristics of antigen and adjuvant, preclinical data, human safety and efficacy data, and overall benefit-risk assessment. The clinical development program began in September 2020 and based on demonstration of favorable safety and immunogenicity profiles in 11 clinical trials in over 5,000 participants, it has been approved for emergency use based on immunobridging results for adults in Taiwan, Estwatini, Somaliland, and Paraguay. The main clinical trials include placebo-controlled phase 2 studies in healthy adults (CT-COV-21), adolescents (CT-COV-22), and elderly population (CT-COV-23) as well as 3 immunobridging phase 3 trials (CT-COV-31, CT-COV-32, and CT-COV-34) in which MVC-COV1901 was compared to AZD1222. There are also clinical trials studying MVC-COV1901 as homologous and heterologous boosters (CT-COV-24 and CT-COV-25). The totality of evidence based on ∼3 million vaccinees to date includes a mostly clean safety profile, with adverse events mostly being mild and self-limiting in both clinical development and post-marketing experience, proven immunogenic response, and real-world effectiveness data. The immunogenic profile demonstrates that MVC-COV1901 induces high levels of neutralizing and binding antibodies against SARS-CoV-2. There is a dose-dependent response and a significant correlation between binding and neutralizing antibody activity. Antigen-specific T-cell responses, particularly a Th1-biased immune response characterized by high levels of interferon gamma and IL-2 cytokines, have also been observed. Coupled with this, MVC-COV1901 has favorable thermostability and better safety profiles when compared to other authorized vaccines from different platforms, which make it potentially a good candidate for vaccine supply chains in global markets.

A "trained immunity" inducer-adjuvanted nanovaccine reverses the growth of established tumors in mice

Innate immune cells are critical in antitumor immune surveillance and the development of antitumor adaptive cellular immunity. Trained innate immune cells demonstrate immune memory-like characteristics, producing more vigorous immune responses to secondary homologous or heterologous stimuli. This study aimed to investigate whether inducing trained immunity is beneficial when using a tumor vaccine to promote antitumor adaptive immune responses. A biphasic delivery system was developed with the trained immunity inducer Muramyl Dipeptide (MDP) and specific tumor antigen human papillomavirus (HPV) E7 peptide encapsulated by poly(lactide-co-glycolide)-acid(PLGA) nanoparticles (NPs), and the NPs along with another trained immunity agonist, β-glucan, were further embedded in a sodium alginate hydrogel. The nanovaccine formulation demonstrated a depot effect for E7 at the injection site and targeted delivery to the lymph nodes and dendritic cells (DCs). The antigen uptake and maturation of DCs were significantly promoted. A trained immunity phenotype, characterized by increased production of IL-1β, IL-6, and TNF-α, was induced in vitro and in vivo in response to secondary homologous or heterologous stimulation. Furthermore, prior innate immune training enhanced the antigen-specific INF-γ-expressing immune cell response elicited by subsequent stimulation with the nanovaccine. Immunization with the nanovaccine completely inhibited the growth of TC-1 tumors and even abolished established tumors in mice. Mechanistically, the inclusion of β-glucan and MDP significantly enhanced the responses of tumor-specific effector adaptive immune cells. The results strongly suggest that the controlled release and targeted delivery of an antigen and trained immunity inducers with an NP/hydrogel biphasic system can elicit robust adaptive immunity, which provides a promising tumor vaccination strategy.

Evaluation of the Association of Recombinant Proteins NanH and PknG from Corynebacterium pseudotuberculosis Using Different Adjuvants as a Recombinant Vaccine in Mice

Caseous lymphadenitis is a chronic contagious disease that causes economic losses worldwide. Treatments are ineffective, thus demonstrating the importance of vaccination. In this study, rNanH and rPknG proteins from Corynebacterium pseudotuberculosis were associated with saponin or aluminum hydroxide adjuvants. Three experimental groups (10 animals each) were immunized with sterile 0.9% saline solution (G1), rNanH + rPknG + Saponin (G2), rNanH + rPknG + Al(OH)3 (G3). The mice received two vaccine doses 21 days apart. Animals were challenged 21 days after the last immunization and evaluated for 50 days, with endpoint criteria applied when needed. The total IgG production levels of the experimental groups increased significantly on day 42 when compared to the control (p < 0.05). When tested against rNanH, G2 had a better rate of anti-rNanH antibodies compared to G3. In the anti-rPknG ELISA, the levels of total IgG, IgG1, and IgG2a antibodies were higher in G2. The vaccines generated partial protection, with 40% of the animals surviving the challenge. The association of recombinant NanH and PknG proteins led to promising protection rates in mice, and although using different adjuvants did not interfere with the survival rate, it influenced the immune response generated by the vaccine formulations.

Immunogenicity of Different Types of Adjuvants and Nano-Adjuvants in Veterinary Vaccines: A Comprehensive Review

Vaccination is the best way to prevent and reduce the damage caused by infectious diseases in animals and humans. So, several vaccines are used for prophylactic purposes before the pathogen infects, while therapeutic vaccines strengthen the immune system after infection with the pathogen. Adjuvants are molecules, compounds, or macromolecules that enhance non-specific immunity and, in collaboration with antigen(s), can improve the body's immune responses and change the type of immune response. The potential and toxicity of adjuvants must be balanced to provide the safest stimulation with the fewest side effects. In order to overcome the limitations of adjuvants and the effective and controlled delivery of antigens, attention has been drawn to nano-carriers that can be a promising platform for better presenting and stimulating the immune system. Some studies show that nanoparticles have a more remarkable ability to act as adjuvants than microparticles. Because nano-adjuvants inactively target antigen-presenting cells (APCs) and change their chemical surface, nanoparticles also perform better in targeted antigen delivery because they cross biological barriers more easily. We collected and reviewed various types of nano-adjuvants with their specific roles in immunogenicity as a prominent strategy used in veterinary vaccines in this paper.

Nonclinical safety assessments of a novel synthetic toll-like receptor 4 agonist and saponin based adjuvant

A full nonclinical safety package was performed to support the clinical use of SPA14, a novel liposome-based vaccine adjuvant containing the synthetic toll-like receptor 4 agonist E6020 and saponin QS21. E6020 and QS21 were tested negative for their potential genotoxic effects in Ames, micronucleus, or mouse-lymphoma TK (thymidine kinase) assay. To evaluate the potential local and systemic effects of SPA14, two toxicity studies were performed in rabbits. In the first dose range finding toxicity study, rabbits received two intramuscular injections of SPA14 at increasing doses of E6020 combined with two antigens, a control (saline), the two antigens alone, or the antigens adjuvanted with a liposome-based adjuvant AS01B. No systemic toxicity was detected, supporting the dose of 5 μg of E6020 for the subsequent pivotal study. In the second repeated dose toxicity study, rabbits received four intramuscular injections of SPA14 alone, a control (saline), SPA14 combined with two antigens, the two antigens alone, or the antigens combined with AF03 adjuvant, which is a squalene-based emulsion. SPA14 alone or in combination with the antigens was well tolerated and did not cause any systemic toxicity. Finally, two safety pharmacology studies were conducted to assess potential cardiovascular and respiratory effects of E6020 and SPA14 in conscious telemetered cynomolgus monkeys and beagle dogs, respectively. One subcutaneous injection of E6020 in monkeys and one intramuscular injection of SPA14 in dogs had no consequences on respiratory and cardiovascular functions. Altogether these results support the clinical development of SPA14.

From design to clinic: Engineered peptide nanomaterials for cancer immunotherapy

Immunotherapy has revolutionized the field of cancer therapy. Nanomaterials can further improve the efficacy and safety of immunotherapy because of their tunability and multifunctionality. Owing to their natural biocompatibility, diverse designs, and dynamic self-assembly, peptide-based nanomaterials hold great potential as immunotherapeutic agents for many malignant cancers, with good immune response and safety. Over the past several decades, peptides have been developed as tumor antigens, effective antigen delivery carriers, and self-assembling adjuvants for cancer immunotherapy. In this review, we give a brief introduction to the use of peptide-based nanomaterials for cancer immunotherapy as antigens, carriers, and adjuvants, and to their current clinical applications. Overall, this review can facilitate further understanding of peptide-based nanomaterials for cancer immunotherapy and may pave the way for designing safe and efficient methods for future vaccines or immunotherapies.

Innovative Vaccine Strategy: Self-Adjuvanting Conjugate Vaccines

Self-adjuvanting vaccines, covalent conjugates between antigens and adjuvants, are chemically well-defined compared with conventional vaccines formulated through mixing antigens with adjuvants. Innate immune receptor ligands effectively induce acquired immunity through the activation of innate immunity, thereby enhancing host immune responses. Thus, innate immune receptor ligands are often used as adjuvants in self-adjuvanting vaccines. In a self-adjuvanting vaccine, the covalent linkage of antigen and adjuvant enables their simultaneous uptake into immune cells where the adjuvant consequently induces antigen-specific immune responses. Importantly, self-adjuvanting vaccines do not require immobilization to carrier proteins or co-administration of additional adjuvants and thus avoid inducing undesired immune responses. Because of these excellent properties, self-adjuvanting vaccines are expected to be candidates for next-generation vaccines. Here, we take an overview of vaccine adjuvants, mainly focusing on those utilized in self-adjuvanting vaccines and then we review recent reports on self-adjuvanting conjugate vaccines.

In-depth review of delivery carriers associated with vaccine adjuvants: current status and future perspectives

INTRODUCTION

Vaccines are powerful tools for controlling microbial infections and preventing epidemics. To enhance the immune response to antigens, effective subunit vaccines or mRNA vaccines often require the combination of adjuvants or delivery carriers. In recent years, with the rapid development of immune mechanism research and nanotechnology, various studies based on the optimization of traditional adjuvants or various novel carriers have been intensified, and the construction of vaccine adjuvant delivery systems (VADS) with both adjuvant activity and antigen delivery has become more and more important in vaccine research.

AREAS COVERED

This paper reviews the common types of vaccine adjuvant delivery carriers, classifies the VADS according to their basic carrier types, introduces the current research status and future development trend, and emphasizes the important role of VADS in novel vaccine research.

EXPERT OPINION

As the number of vaccine types increases, conventional aluminum adjuvants show limitations in effectively stimulating cellular immune responses, limiting their use in therapeutic vaccines for intracellular infections or tumors. In contrast, the use of conventional adjuvants as VADS to carry immunostimulatory molecules or deliver antigens can greatly enhance the immune boosting effect of classical adjuvants. A comprehensive understanding of the various delivery vehicles will further facilitate the development of vaccine adjuvant research.

Therapeutic Vaccination for HPV-Mediated Cancers

Purpose of Review

The goal of this narrative review is to educate clinicians regarding the foundational concepts, efficacy, and future directions of therapeutic vaccines for human papillomavirus (HPV)-mediated cancers.

Recent Findings

Therapeutic HPV vaccines deliver tumor antigens to stimulate an immune response to eliminate tumor cells. Vaccine antigen delivery platforms are diverse and include DNA, RNA, peptides, proteins, viral vectors, microbial vectors, and antigen-presenting cells. Randomized, controlled trials have demonstrated that therapeutic HPV vaccines are efficacious in patients with cervical intraepithelial neoplasia. In patients with HPV-mediated malignancies, evidence of efficacy is limited. However, numerous ongoing studies evaluating updated therapeutic HPV vaccines in combination with immune checkpoint inhibition and other therapies exhibit significant promise.

Summary

Therapeutic vaccines for HPV-mediated malignancies retain a strong biological rationale, despite their limited efficacy to date. Investigators anticipate they will be most effectively used in combination with other regimens, such as immune checkpoint inhibition.

In silico approach to design a multi-epitopic vaccine candidate targeting the non-mutational immunogenic regions in envelope protein and surface glycoprotein of SARS-CoV-2

The novel corona virus (COVID-19) is a causative agent for severe acute respiratory syndrome (SARS-CoV-2) and responsible for the current human pandemic situation which has caused global social and economic commotion. The currently available vaccines use whole viruses whereas there is scope for peptide based vaccines. Thus, the global raise in statistics of this infection at an alarming rate evoked us to determine a novel and effective vaccine candidate against SARS-CoV-2. To find the potential vaccine candidate targets, immunoinformatics approaches were used to analyze the mutations in the envelope protein and surface glycoprotein and determine the conserved region; further specific T-cell epitopes VSLVKPSFY, SLVKPSFYV, RVKNLNSSR, SEETGTLIV, LVKPSFYVY, LTDEMIAQY, YLQPRTFLL, RLFRKSNLK, SPRRARSVA, AEIRASANL, TLLALHRSY, YSRVKNLNS and FELLHAPAT and B-cells epitopes TLAILTALRLCAYCCN and AGTITSGWTFGAGAAL were identified. The 3 D structure of epitope was predicted, refined and validated. The molecular docking analysis of multi-epitope vaccine candidates with TLR receptors, predicted effective binding. Overall, using bioinformatics approach this multi-epitopic target facilitates the proof of concept for SARS-CoV-2 conserved epitopic vaccine design.Communicated by Ramaswamy H. Sarma.

Breast Cancer Vaccine Containing a Novel Toll-like Receptor 7 Agonist and an Aluminum Adjuvant Exerts Antitumor Effects

Mucin 1 (MUC1) has received increasing attention due to its high expression in breast cancer, in which MUC1 acts as a cancer antigen. Our group has been committed to the development of small-molecule TLR7 (Toll-like receptor 7) agonists, which have been widely investigated in the field of tumor immunotherapy. In the present study, we constructed a novel tumor vaccine (SZU251 + MUC1 + Al) containing MUC1 and two types of adjuvants: a TLR7 agonist (SZU251) and an aluminum adjuvant (Al). Immunostimulatory responses were first verified in vitro, where the vaccine promoted the release of cytokines and the expression of costimulatory molecules in mouse BMDCs (bone marrow dendritic cells) and spleen lymphocytes. Then, we demonstrated that SZU251 + MUC1 + Al was effective and safe against a tumor expressing the MUC1 antigen in both prophylactic and therapeutic schedules in vivo. The immune responses in vivo were attributed to the increase in specific humoral and cellular immunity, including antibody titers, CD4⁺, CD8⁺ and activated CD8⁺ T cells. Therefore, our vaccine candidate may have beneficial effects in the prevention and treatment of breast cancer patients.

Current status and development prospects of aquatic vaccines

Diseases are a significant impediment to aquaculture's sustainable and healthy growth. The aquaculture industry is suffering significant financial losses as a result of the worsening water quality and increasing frequency of aquatic disease outbreaks caused by the expansion of aquaculture. Drug control, immunoprophylaxis, ecologically integrated control, etc. are the principal control strategies for fish infections. For a long time, the prevention and control of aquatic diseases have mainly relied on the use of various antibiotics and chemical drugs. However, long-term use of chemical inputs not only increases pathogenic bacteria resistance but also damages the fish and aquaculture environments, resulting in drug residues in aquatic products, severely impeding the development of the aquaculture industry. The development and use of aquatic vaccines are the safest and most effective ways to prevent aquatic animal diseases and preserve the health and sustainability of aquaculture. To give references for the development and implementation of aquatic vaccines, this study reviews the development history, types, inoculation techniques, mechanisms of action, development prospects, and challenges encountered with aquatic vaccines.

A specific Leishmania infantum polyepitope vaccine triggers Th1-type immune response and protects against experimental visceral leishmaniasis

The development of an immunogenic, effective, and safe vaccine is essential as an alternative for disease control. The present study aimed to evaluate the immunogenicity and efficacy potential of a polyepitope T-cell antigen candidate against visceral leishmaniasis in a murine model. BALB/c mice were immunized with three doses subcutaneously with Poly-T Leish alone or adjuvanted with Saponin plus Monophosphoryl lipid A, with 15-day intervals between doses, and challenged with 10⁷ stationary-phase Leishmania infantum promastigotes via tail vein. Immunogenicity and parasitism in spleen and liver of immunized mice were evaluated 45 days post-challenge. Our results revealed that the immunization with Poly-T Leish and Poly-T Leish/SM increases the percentage of specific T (CD4⁺ and CD8⁺) lymphocytes proliferation in vitro after antigen-specific stimulation. Also, Poly-T Leish and Poly-T Leish/SM groups showed a high percentage of IFN-γ and TNF-α-producing T cells, meanwhile, the Poly-T Leish/SM group also showed an increased percentage of multifunctional T cells producing double and triple-positive (IFN-γ⁺TNF-α⁺IL-2⁺) cytokines. The immunization with Poly-T Leish or Poly-T Leish/SM stimulated a decreased IL-4 and IL-10 compared to the Saline and adjuvant group. Poly-T Leish/SM immunized mice exhibit a noteworthy reduction in the parasite burden (spleen and liver) through real-time PCR (96%). Moreover, we observed higher nitrite secretion in 120-hour stimulated-culture supernatant using Griess method. We demonstrated that the Poly-T Leish/SM candidate was potentially immunogenic, providing enhancement of protective immune mechanisms, and conferred protection reducing parasitism. Our candidate was considered potential against visceral leishmaniasis, and eventually, could be tested in phase I and II clinical trials in dogs.

Protein-Based Adjuvants for Vaccines as Immunomodulators of the Innate and Adaptive Immune Response: Current Knowledge, Challenges, and Future Opportunities

New-generation vaccines, formulated with subunits or nucleic acids, are less immunogenic than classical vaccines formulated with live-attenuated or inactivated pathogens. This difference has led to an intensified search for additional potent vaccine adjuvants that meet safety and efficacy criteria and confer long-term protection. This review provides an overview of protein-based adjuvants (PBAs) obtained from different organisms, including bacteria, mollusks, plants, and humans. Notably, despite structural differences, all PBAs show significant immunostimulatory properties, eliciting B-cell- and T-cell-mediated immune responses to administered antigens, providing advantages over many currently adopted adjuvant approaches. Furthermore, PBAs are natural biocompatible and biodegradable substances that induce minimal reactogenicity and toxicity and interact with innate immune receptors, enhancing their endocytosis and modulating subsequent adaptive immune responses. We propose that PBAs can contribute to the development of vaccines against complex pathogens, including intracellular pathogens such as Mycobacterium tuberculosis, those with complex life cycles such as Plasmodium falciparum, those that induce host immune dysfunction such as HIV, those that target immunocompromised individuals such as fungi, those with a latent disease phase such as Herpes, those that are antigenically variable such as SARS-CoV-2 and those that undergo continuous evolution, to reduce the likelihood of outbreaks.

Multicomponent encapsulation into fully degradable protein nanocarriers via interfacial azide-alkyne click reaction in miniemulsion allows the co-delivery of immunotherapeutics

Encapsulation of multiple adjuvants along with antigens into nanocarriers allows a co-delivery to antigen-presenting cells for the synergistic induction of robust immune responses. However, loading cargoes of different molar masses, polarities, and solubilities in high efficiencies remains a challenge. Therefore, we developed a strategy to encapsulate a triple combination of the so-called adjuvants, i.e. with Resiquimod (R848), muramyl dipeptide (MDP) and polyinosinic-polycytidylic acid (Poly(I : C)) into human serum albumin (HSA) nanocarriers. The loading is conducted in situ while the nanocarrier is formed by an orthogonal and metal-free click reaction at the interface of an inverse miniemulsion. By this unique approach, high encapsulation efficiency without harming the cargo during the nanocarrier formation process and regardless of their physical properties is achieved, thus keeping their bioactivity. Furthermore, we demonstrated high control over the encapsulation efficiency and varying the amount of each cargo did not influence the efficiency of multicomponent encapsulation. Azide-modified HSA was crosslinked with hexanediol dipropiolate (HDDP) at the interface of a water-in-oil miniemulsion. Varying the crosslinker amount allowed us to tailor the density and degradation rates of the protein shell. Additional installation of disulfide bonds into the crosslinker created redox-responsive nanocarriers, which degraded both by protease and under reducing conditions with dithiothreitol. The prepared HSA nanocarriers were efficiently taken up by dendritic cells and exhibited an additive cell activation and maturation, exceeding the nanocarriers loaded with only a single drug. This general protocol allows the orthogonal and metal-free encapsulation of various drugs or adjuvants at defined concentrations into the protein nanocarriers.

Fiction and Facts about BCG Imparting Trained Immunity against COVID-19

The Bacille Calmette-Guérin or BCG vaccine, the only vaccine available against Mycobacterium tuberculosis can induce a marked Th1 polarization of T-cells, characterized by the antigen-specific secretion of IFN-γ and enhanced antiviral response. A number of studies have supported the concept of protection by non-specific boosting of immunity by BCG and other microbes. BCG is a well-known example of a trained immunity inducer since it imparts ‘non-specific heterologous’ immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the recent pandemic. SARS-CoV-2 continues to inflict an unabated surge in morbidity and mortality around the world. There is an urgent need to devise and develop alternate strategies to bolster host immunity against the coronavirus disease of 2019 (COVID-19) and its continuously emerging variants. Several vaccines have been developed recently against COVID-19, but the data on their protective efficacy remains doubtful. Therefore, urgent strategies are required to enhance system immunity to adequately defend against newly emerging infections. The concept of trained immunity may play a cardinal role in protection against COVID-19. The ability of trained immunity-based vaccines is to promote heterologous immune responses beyond their specific antigens, which may notably help in defending against an emergency situation such as COVID-19 when the protective ability of vaccines is suspicious. A growing body of evidence points towards the beneficial non-specific boosting of immune responses by BCG or other microbes, which may protect against COVID-19. Clinical trials are underway to consider the efficacy of BCG vaccination against SARS-CoV-2 on healthcare workers and the elderly population. In this review, we will discuss the role of BCG in eliciting trained immunity and the possible limitations and challenges in controlling COVID-19 and future pandemics.

Investigating preparation and characterisation of diphtheria toxoid-loaded on sodium alginate nanoparticles

This paper aims to investigate the preparation and characterisation of the alginate nanoparticles (NPs) as antigen delivery system loaded by diphtheria toxoid (DT). For this purpose, both the loading capacity (LC) and Loading efficiency (LE) of the alginate NPs burdened by DT are evaluated. Moreover, the effects of different concentrations of sodium alginate and calcium chloride on the NPs physicochemical characteristics are surveyed in addition to other physical conditions such as homogenization time and rate. To do so, the NPs are characterised using particle size and distribution, zeta potential, scanning electron microscopy, encapsulation efficiency, in vitro release study and FT‐IR spectroscopy. Subsequently, the effects of homogenization time and rate on the NPs are assessed. At the meantime, the NPs LC and efficiency in several DT concentrations are estimated. The average size of the NPs was 400.7 and 276.6 nm for unloaded and DT loaded, respectively. According to the obtained results, the zeta potential of the blank and DT loaded NPs are estimated as −23.7 mV and −21.2 mV, respectively. Whereas, the LC and LE were >80% and >90%, in that order. Furthermore, 95% of the releasing DT loaded NPs occurs at 140 h in the sustained mode without any bursting release. It can be concluded that the features of NPs such as morphology and particle size are strongly depended on the calcium chloride, sodium alginate concentrations and physicochemical conditions in the NPs formation process. In addition, appropriate concentrations of the sodium alginate and calcium ions would lead to obtaining the desirable NPs formation associated with the advantageous LE, LC (over 80%) and sustained in vitro release profile. Ultimately, the proposed NPs can be employed in vaccine formulation for the targeted delivery, controlled and slow antigen release associated with the improved antigen stability.

Aluminum hydroxide adjuvant diverts the uptake and trafficking of genetically detoxified pertussis toxin to lysosomes in macrophages

Aluminum salts have been successfully utilized as adjuvants to enhance the immunogenicity of vaccine antigens since the 1930s. However, the cellular mechanisms behind the immune adjuvanticity effect of these materials in antigen‐presenting cells are poorly understood. In this study, we investigated the uptake and trafficking of aluminum oxy‐hydroxide (AlOOH), in RAW 264.7 murine and U‐937 human macrophages‐like cells. Furthermore, we determined the impact that the adsorption to AlOOH particulates has on the trafficking of a Bordetella pertussis vaccine candidate, the genetically detoxified pertussis toxin (gdPT). Our results indicate that macrophages internalize AlOOH by constitutive macropinocytosis assisted by the filopodial protrusions that capture the adjuvant particles. Moreover, we show that AlOOH has the capacity to nonspecifically adsorb IgG, engaging opsonic phagocytosis, which is a feature that may allow for more effective capture and uptake of adjuvant particles by antigen‐presenting cells (APCs) at the site of vaccine administration. We found that AlOOH traffics to endolysosomal compartments that hold degradative properties. Importantly, while we show that gdPT escapes degradative endolysosomes and traffics toward the retrograde pathway, as reported for the wild‐type pertussis toxin, the adsorption to AlOOH diverts gdPT to traffic to the adjuvant’s lysosome‐type compartments, which may be key for MHC‐II‐driven antigen presentation and activation of CD4⁺ T cell. Thus, our findings establish a direct link between antigen adsorption to AlOOH and the intracellular trafficking of antigens within antigen‐presenting cells and bring to light a new potential mechanism for aluminum adjuvancy. Moreover, the in‐vitro single‐cell approach described herein provides a general framework and tools for understanding critical attributes of other vaccine formulations.

Systemically Administered TLR7/8 Agonist and Antigen-Conjugated Nanogels Govern Immune Responses against Tumors

The generation of specific humoral and cellular immune responses plays a pivotal role in the development of effective vaccines against tumors. Especially the presence of antigen-specific, cytotoxic T cells influences the outcome of therapeutic cancer vaccinations. Different strategies, ranging from delivering antigen-encoding mRNAs to peptides or full antigens, are accessible but often suffer from insufficient immunogenicity and require immune-boosting adjuvants as well as carrier platforms to ensure stability and adequate retention. Here, we introduce a pH-responsive nanogel platform as a two-component antitumor vaccine that is safe for intravenous application and elicits robust immune responses in vitro and in vivo. The underlying chemical design allows for straightforward covalent attachment of a model antigen (ovalbumin) and an immune adjuvant (imidazoquinoline-type TLR7/8 agonist) onto the same nanocarrier system. In addition to eliciting antigen-specific T and B cell responses that outperform mixtures of individual components, our two-component nanovaccine leads in prophylactic and therapeutic studies to an antigen-specific growth reduction of different tumors expressing ovalbumin intracellularly or on their surface. Regarding the versatile opportunities for functionalization, our nanogels are promising for the development of highly customized and potent nanovaccines.

Liposomes as Adjuvants and Vaccine Delivery Systems

The review considers liposomes as systems of substantial interest as adjuvant carriers in vaccinology due to their versatility and maximal biocompatibility. Research and development on the use of liposomes and lipid nanoparticles to create subunit vaccines for the prevention and treatment of infectious diseases has been going on for several decades. In recent years, the area has seen serious progress due to the improvement of the technology of industrial production of various high-grade lipids suitable for parenteral administration and the emergence of new technologies and equipment for the production of liposomal preparations. When developing vaccines, it is necessary to take into account how the body’s immune system (innate and adaptive immunity) functions. The review briefly describes some of the fundamental mechanisms underlying the mobilization of immunity when encountering an antigen, as well as the influence of liposome carriers on the processes of internalization of antigens by immunocompetent cells and ways of immune response induction. The results of the studies on the interactions of liposomes with antigen-presenting cells in function of the liposome size, charge, and phase state of the bilayer, which depends on the lipid composition, are often contradictory and should be verified in each specific case. The introduction of immunostimulant components into the composition of liposomal vaccine complexes—ligands of the pathogen-associated molecular pattern receptors—permits modulation of the strength and type of the immune response. The review briefly discusses liposome-based vaccines approved for use in the clinic for the treatment and prevention of infectious diseases, including mRNA-loaded lipid nanoparticles. Examples of liposomal vaccines that undergo various stages of clinical trials are presented.

Immunometabolism in biofilm infection: lessons from cancer

BACKGROUND

Biofilm is a community of bacteria embedded in an extracellular matrix, which can colonize different human cells and tissues and subvert the host immune reactions by preventing immune detection and polarizing the immune reactions towards an anti-inflammatory state, promoting the persistence of biofilm-embedded bacteria in the host.

MAIN BODY OF THE MANUSCRIPT

It is now well established that the function of immune cells is ultimately mediated by cellular metabolism. The immune cells are stimulated to regulate their immune functions upon sensing danger signals. Recent studies have determined that immune cells often display distinct metabolic alterations that impair their immune responses when triggered. Such metabolic reprogramming and its physiological implications are well established in cancer situations. In bacterial infections, immuno-metabolic evaluations have primarily focused on macrophages and neutrophils in the planktonic growth mode.

CONCLUSION

Based on differences in inflammatory reactions of macrophages and neutrophils in planktonic- versus biofilm-associated bacterial infections, studies must also consider the metabolic functions of immune cells against biofilm infections. The profound characterization of the metabolic and immune cell reactions could offer exciting novel targets for antibiofilm therapy.

Fundamentals of Fish Vaccination

Fish health management has become a critical component of disease control and is invaluable for improved harvests and sustainable aquaculture. Vaccination is generally accepted as the most effective prophylactic measure for fish disease prevention, on environmental, social, and economic grounds. Although the historical approach for developing fish vaccines was based on the principle of Louis Pasteur's "isolate, inactivate and inject," but their weak immunogenicity and low efficacies in many cases, have shifted the focus of fish vaccine development from traditional to next-generation technologies. However, before any fish vaccine can be successfully commercialized, several hurdles need to be overcome regarding the production cost, immunogenicity, effectiveness, mode of administration, environmental safety, and associated regulatory concerns. In this context, the chapter summarises the basic aspects of fish vaccination such as type of vaccine, modalities of vaccine delivery, the immunological basis of fish immunization as well as different challenges associated with the development process and future opportunities.

CAvant® WO-60 as an Effective Immunological Adjuvant for Avian Influenza and Newcastle Disease Vaccine

Despite the immunogenicity of vaccines currently used in poultry, several pathogens, including avian influenza virus (AIV) and Newcastle disease virus (NDV), cause enormous economic losses to the global poultry industry. The efficacy of vaccines can be improved by the introduction of effective adjuvants. This study evaluated a novel water-in-oil emulsion adjuvant, CAvant® WO-60, which effectively enhanced both the immunogenicity of conserved influenza antigen sM2HA2 and inactivated whole H9N2 antigen (iH9N2). CAvant® WO-60 induced both humoral and cell-mediated immunity in mice and provided 100% protection from challenge with 10 LD50 of A/Aquatic bird/Korea/W81/2005 (H5N2) and A/Chicken/Korea/116/2004 (H9N2) AIV. Importantly, immunization of chickens with iH9N2 plus inactivated NDV LaSota (iNDV) bivalent inactivated vaccine emulsified in CAvant® WO-60 induced seroprotective levels of antigen-specific antibody responses. Taken together, these results suggested that CAvant® WO-60 is a promising adjuvant for poultry vaccines.

Engineering mannosylated pickering emulsions for the targeted delivery of multicomponent vaccines

While research on cancer vaccines has made great strides in the field of immunotherapy, the targeted delivery of multiple effective components (rational-tailored antigens and adjuvants) remains a challenge. Here, we utilized the unique hierarchical structures of Pickering emulsions (particles, oil core, and water-oil interface) to develop mannosylated (M) Pickering emulsions (PE) that target antigen presenting cells and synergistically deliver antigenic peptides and the TLR9 agonist CpG (C) as an enhanced cancer vaccine (MPE-C). We chemically linked mannose residues to PLGA/PLAG-PEG nanoparticles and produced a dense array of mannose on the nanopatterned surface of Pickering emulsions, allowing for increased cellular targeting. Together with the inherent deformability of the oily core, MPE-C increased the droplet-cellular contact area and provoked the cellular recognition of mannose and CpG for enhanced immune activation. We found that MPE-C attracted a large number of APCs to the local site of administration, evidently increasing cellular uptake and activation. Additionally, we observed increased antigen-specific cellular immune responses, with potent anti-tumor effects against both E.G7-OVA and B16-MUCI tumors. Furthermore, MPE-C combined with PD-1 antibodies produced a significant tumor regression, resulting in synergistic increases in anti-tumor effects. Thus, through the strategic loading of mannose, antigens, and CpG, Pickering emulsions could serve as a targeted delivery platform for enhanced multicomponent cancer vaccines.

Chitosan nanoparticle formulation attenuates poly (I:C) induced innate immune responses against inactivated virus vaccine in Atlantic salmon (Salmo salar)

Many vaccine formulations, in particular vaccines based on inactivated virus, needs adjuvants to boost immunogenicity. In aquaculture, mineral and plant oil are used as adjuvant in commercial vaccines, and the advent of oil-adjuvanted vaccines was crucial to aquaculture development. Nevertheless, some of these approved vaccines display suboptimal performance in the field compared to experimental conditions. Therefore, there is a need to improve adjuvants and delivery methods for fish vaccines against viruses. We used RNA sequencing of Atlantic salmon head kidney to analyse the difference in gene expression 24 h after injection of different experimental vaccine formulations. We compared five different formulations in addition to a PBS control: inactivated virus alone (group V), soluble poly (I:C) (group P), nanoparticles containing poly (I:C) (group N), soluble poly (I:C) + inactivated virus (group PV) and finally nanoparticles containing poly (I:C) + inactivated virus (group NV). Our results showed poly (I:C)'s ability as adjuvant and its capacity influence innate immune genes expression in Atlantic salmon. Soluble poly (I:C) upregulated multiple immune related genes and was more effective compared to poly (I:C) formulated into chitosan nanoparticles (more than 10 fold increase in differentially expressed genes, DEGs). However, inclusion of inactivated ISA virus in the nanoparticle vaccine, increased the number of DEGs fivefold suggesting a synergistic effect of adjuvant and antigen. Our results indicate that the way poly (I:C) is formulated and the presence of antigen is important for the magnitude of the innate immune response in Atlantic salmon.

A Combined Adjuvant TF-Al Consisting of TFPR1 and Aluminum Hydroxide Augments Strong Humoral and Cellular Immune Responses in Both C57BL/6 and BALB/c Mice

TFPR1 is a novel adjuvant for protein and peptide antigens, which has been demonstrated in BALB/c mice in our previous studies; however, its adjuvanticity in mice with different genetic backgrounds remains unknown, and its adjuvanticity needs to be improved to fit the requirements for various vaccines. In this study, we first compared the adjuvanticity of TFPR1 in two commonly used inbred mouse strains, BALB/c and C57BL/6 mice, in vitro and in vivo, and demonstrated that TFPR1 activated TLR2 to exert its immune activity in vivo. Next, to prove the feasibility of TFPR1 acting as a major component of combined adjuvants, we prepared a combined adjuvant, TF-Al, by formulating TFPR1 and alum at a certain ratio and compared its adjuvanticity with that of TFPR1 and alum alone using OVA and recombinant HBsAg as model antigens in both BALB/c and C57BL/6 mice. Results showed that TFPR1 acts as an effective vaccine adjuvant in both BALB/c mice and C57BL/6 mice, and further demonstrated the role of TLR2 in the adjuvanticity of TFPR1 in vivo. In addition, we obtained a novel combined adjuvant, TF-Al, based on TFPR1, which can augment antibody and cellular immune responses in mice with different genetic backgrounds, suggesting its promise for vaccine development in the future.

Delivery of nanovaccine towards lymphoid organs: recent strategies in enhancing cancer immunotherapy

With the in-depth exploration on cancer therapeutic nanovaccines, increasing evidence shows that the poor delivery of nanovaccines to lymphoid organs has become the culprit limiting the rapid induction of anti-tumor immune response. Unlike the conventional prophylactic vaccines that mainly form a depot at the injection site to gradually trigger durable immune response, the rapid proliferation of tumors requires an efficient delivery of nanovaccines to lymphoid organs for rapid induction of anti-tumor immunity. Optimization of the physicochemical properties of nanovaccine (e.g., size, shape, charge, colloidal stability and surface ligands) is an effective strategy to enhance their accumulation in lymphoid organs, and nanovaccines with dynamic structures are also designed for precise targeted delivery of lymphoid organs or their subregions. The recent progress of these nanovaccine delivery strategies is highlighted in this review, and the challenges and future direction are also discussed.

Mechanism of a COVID-19 nanoparticle vaccine candidate that elicits a broadly neutralizing antibody response to SARS-CoV-2 variants

Vaccines that induce potent neutralizing antibody (NAb) responses against emerging variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are essential for combating the coronavirus disease 2019 (COVID-19) pandemic. We demonstrated that mouse plasma induced by self-assembling protein nanoparticles (SApNPs) that present 20 rationally designed S2GΔHR2 spikes of the ancestral Wuhan-Hu-1 strain can neutralize the B.1.1.7, B.1.351, P.1, and B.1.617 variants with comparable potency. The adjuvant effect on vaccine-induced immunity was investigated by testing 16 formulations for the multilayered I3-01v9 SApNP. Using single-cell sorting, monoclonal antibodies (mAbs) with diverse neutralization breadth and potency were isolated from mice immunized with the receptor binding domain (RBD), S2GΔHR2 spike, and SApNP vaccines. The mechanism of vaccine-induced immunity was examined in the mouse model. Compared with the soluble spike, the I3-01v9 SApNP showed sixfold longer retention, fourfold greater presentation on follicular dendritic cell dendrites, and fivefold stronger germinal center reactions in lymph node follicles.

Overcoming Chemoimmunotherapy-Induced Immunosuppression by Assemblable and Depot Forming Immune Modulating Nanosuspension

The deficiency of antigen-specific T cells and the induction of various treatment-induced immunosuppressions still limits the clinical benefit of cancer immunotherapy. Although the chemo-immunotherapy adjuvanted with Toll-like receptor 7/8 agonist (TLR 7/8a) induces immunogenic cell death (ICD) and in situ vaccination effect, indoleamine 2,3-dioxygenase (IDO) is also significantly increased in the tumor microenvironment (TME) and tumor-draining lymph node (TDLN), which offsets the activated antitumor immunity. To address the treatment-induced immunosuppression, an assemblable immune modulating suspension (AIMS) containing ICD inducer (paclitaxel) and supra-adjuvant (immune booster; R848 as a TLR 7/8a, immunosuppression reliever; epacadostat as an IDO inhibitor) is suggested and shows that it increases cytotoxic T lymphocytes and relieves the IDO-related immunosuppression (TGF-β, IL-10, myeloid-derived suppressor cells, and regulatory T cells) in both TME and TDLN, by the formation of in situ depot in tumor bed as well as by the efficient migration into TDLN. Local administration of AIMS increases T cell infiltration in both local and distant tumors and significantly inhibits the metastasis of tumors to the lung. Reverting treatment-induced secondary immunosuppression and reshaping "cold tumor" into "hot tumor" by AIMS also increases the response rate of immune checkpoint blockade therapy, which promises a new nanotheranostic strategy in cancer immunotherapy.

Plasmodium falciparum Malaria Vaccines and Vaccine Adjuvants

Malaria-a parasite vector-borne disease-is a global health problem, and Plasmodium falciparum has proven to be the deadliest among Plasmodium spp., which causes malaria in humans. Symptoms of the disease range from mild fever and shivering to hemolytic anemia and neurological dysfunctions. The spread of drug resistance and the absence of effective vaccines has made malaria disease an ever-emerging problem. Although progress has been made in understanding the host response to the parasite, various aspects of its biology in its mammalian host are still unclear. In this context, there is a pressing demand for the development of effective preventive and therapeutic strategies, including new drugs and novel adjuvanted vaccines that elicit protective immunity. The present article provides an overview of the current knowledge of anti-malarial immunity against P. falciparum and different options of vaccine candidates in development. A special emphasis has been made on the mechanism of action of clinically used vaccine adjuvants.

Azoximer Bromide: Mystery, Serendipity, and Promise

Azoximer bromide (AZB) was identified as an immunomodulator, and was initially developed and currently successfully indicated as one of several natural polyelectrolytes, a vaccine adjuvant, and an effective agent for the treatment of infectious and inflammatory diseases of viral, bacterial, and fungal origin. AZB has the potential to increase an individual's resistance to local and general infection and is indicated for the treatment of viral infections, and has also demonstrated clinical efficacy in the treatment of a variety of secondary immunodeficiencies. However, AZB may offer long-term promise beyond use against infection. Multiple clinical trials and research studies in cancer patients have reported favourable outcomes with AZB as well as an optimal safety and tolerability profile. The findings raise the possibility of direct antitumor properties. This literature review analyses the novel mechanisms that mediate the AZB direct anticancer effects. Overall, the evidence suggests that AZB has the hallmark of an agent that could be used to support existing cancer treatments at different stages of disease.

Mechanism of a COVID-19 nanoparticle vaccine candidate that elicits a broadly neutralizing antibody response to SARS-CoV-2 variants

Vaccines that induce potent neutralizing antibody (NAb) responses against emerging variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are essential for combating the coronavirus disease 2019 (COVID-19) pandemic. We demonstrated that mouse plasma induced by self-assembling protein nanoparticles (SApNPs) that present 20 rationally designed S2GΔHR2 spikes of the ancestral Wuhan-Hu-1 strain can neutralize the B.1.1.7, B.1.351, P.1, and B.1.617 variants with the same potency. The adjuvant effect on vaccine-induced immunity was investigated by testing 16 formulations for the multilayered I3-01v9 SApNP. Using single-cell sorting, monoclonal antibodies (mAbs) with diverse neutralization breadth and potency were isolated from mice immunized with the receptor binding domain (RBD), S2GΔHR2 spike, and SApNP vaccines. The mechanism of vaccine-induced immunity was examined in mice. Compared with the soluble spike, the I3-01v9 SApNP showed 6-fold longer retention, 4-fold greater presentation on follicular dendritic cell dendrites, and 5-fold stronger germinal center reactions in lymph node follicles.

Bursal peptide BP-IV as a novel immunoadjuvant enhances the protective efficacy of an epitope peptide vaccine containing T and B cell epitopes of the H9N2 avian influenza virus

Short peptide antigens covering conserved T or B cell epitopes have been investigated in influenza vaccines. Bursal pentapeptide V (BPP-V) and bursal peptide IV (BP-IV) are small molecular peptides that were isolated and identified from the bursa of Fabricius (BF) and induce a strong immune response at both the humoural and cellular levels. To explore the molecular adjuvant potential of BPP-V and BP-IV with an epitope vaccine, an epitope peptide (HA_284-298, GNCVVQCQTERGGLN) rich in T and B cell epitopes for the H9N2 avian influenza virus (AIV) haemagglutinin (HA) protein was selected. BPP-V and BP-IV were coupled with the epitope peptide sequence to form BPP-V and BP-IV-epitope vaccines, respectively. The immunoefficacy of BPP-V and BP-IV-epitope peptide vaccines was evaluated. The results showed that the epitope peptide had weak immunogenicity. The BPP-V-epitope peptide vaccine promoted only the secretion of anti-HA IgG and IgG1 antibodies. The BP-IV-epitope peptide vaccine not only promoted the production of anti-HA IgG and IgG1 antibodies but also significantly induced the production of the IgG2a antibody. The BP-IV-epitope peptide vaccine significantly promoted the production of interleukin (IL-4) and interferon-γ (IFN-γ) (the BPP-V epitope peptide vaccine promoted only the production of IL-4), enhanced the cytotoxic T lymphocyte (CTL) response, and increased the proportion of CD3⁺ T lymphocytes. Moreover, the BP-IV-epitope peptide vaccine promoted a cell-mediated immune response similar to that of the AIV vaccine group. Furthermore, BPP-V and BP-IV-epitope peptide vaccines could also accelerate the clearance of pulmonary virus and reduce pathological damage after the challenge with H9N2 AIV. This study demonstrates the potential of BP-IV as an effective adjuvant for the epitope peptide vaccine for the H9N2 AIV.

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

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

The Status and Prospects of Epstein-Barr Virus Prophylactic Vaccine Development

Epstein–Barr virus (EBV) is a human herpesvirus that is common among the global population, causing an enormous disease burden. EBV can directly cause infectious mononucleosis and is also associated with various malignancies and autoimmune diseases. In order to prevent primary infection and subsequent chronic disease, efforts have been made to develop a prophylactic vaccine against EBV in recent years, but there is still no vaccine in clinical use. The outbreak of the COVID-19 pandemic and the global cooperation in vaccine development against SARS-CoV-2 provide insights for next-generation antiviral vaccine design and opportunities for developing an effective prophylactic EBV vaccine. With improvements in antigen selection, vaccine platforms, formulation and evaluation systems, novel vaccines against EBV are expected to elicit dual protection against infection of both B lymphocytes and epithelial cells. This would provide sustainable immunity against EBV-associated malignancies, finally enabling the control of worldwide EBV infection and management of EBV-associated diseases.

Immunogenicity of antigens from outer membrane vesicles of Neisseria meningitidis associated with bilayer fragment of dioctadecyldimethylammonium in Swiss adult mice

Purpose

In the present study, meningococcal serogroup B outer membrane vesicles (OMVs) were associated with bilayer fragments of a cationic lipid, dioctadecyldimethylammonium (DDA-BF), used as adjuvant, in an antigenic preparation tested in adult female outbred mice. This adjuvant was compared to the traditional adjuvant aluminum hydroxide.

Materials and Methods

The potential in generating humoral response was evaluated by enzyme-linked immunosorbent assay (ELISA). Individual serum was collected and immunoglobulin G (IgG), IgG1, IgG2a, and IgG2b were quantified. Analyses were carried out 15 and 60 days after immunization. Antibodies avidity index were also analyzed by ELISA. Immunoblot and dot-ELISA were carried out to evaluate specific reaction for homologous strains and cross-reactive antigens present in other meningococcal strains isolated in 2011–2012 year, in Brazil. Delayed type hypersensitivity was used as indicative of cellular immunity and compared between two experimental groups, 24 hours after homologous strain challenge.

Results

The OMVs of Neisseria meningitidis, and N. lactamica (related species) were characterized by electrophoretic separation of proteins in 13% polyacrylamide gel. The strains presented antigens in the range of 8 to 130 kDa, showing a heterogeneous protein migration pattern. In the group immunized with OMVs/DDA-BF, we found no significant production of total IgG 15 days after the first immunization. On the other hand, 60 days after first immunization both adjuvants act benefiting total IgG production similarly. The antibodies of the IgG isotype produced by animals immunized after one or two doses after first immunization, showed intermediate and high avidity, independent on the adjuvant used. In both experimental groups the swelling of the footpads was significantly higher than those of the controls, suggesting that only one dose was enough to stimulate the generation of cellular immunity.

Conclusion

The use of this cationic adjuvant for N. meningitidis OMVs preparation revealed good potential for future new antigen preparation for N. meningitidis vaccine.