Vaccine adjuvants to engage the cross-presentation pathway

A comprehensive review on targeting diverse immune cells for anticancer therapy: Beyond immune checkpoint inhibitors

Although immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment, primary resistance and acquired resistance continue to limit their efficacy for many patients. To address resistance and enhance the anti-tumor activity within the tumor immune microenvironment (TIME), numerous therapeutic strategies targeting both innate and adaptive immune cells have emerged. These include combination therapies with ICIs, chimeric antigen receptor T-cell (CAR-T), chimeric antigen receptor macrophages (CAR-Ms) or chimeric antigen receptor natural killer cell (CAR-NK) therapy, colony stimulating factor 1 receptor (CSF1R) inhibitors, dendritic cell (DC) vaccines, toll-like receptor (TLR) agonists, cytokine therapies, and chemokine inhibition. These approaches underscore the significant potential of the TIME in cancer treatment. This article provides a comprehensive and up-to-date review of the mechanisms of action of various innate and adaptive immune cells within the TIME, as well as the therapeutic strategies targeting each immune cell type, aiming to deepen the understanding of their therapeutic potential.

The genetic, biophysical and immunological studies of a self-adjuvanted protein nanoparticle

Adjuvant is required for boosting the immune responses for subunit vaccine. An emerging category of vaccine adjuvant is the self-assembling peptide that forms fibril and stimulates both humoral and cellular immunities. Based on our previous finding that a stabilized self-assembled protein nanoparticle (PNP), also called Vaccine Delivery system X (VADEX), assembled from a fusion protein composed of an amphipathic helical peptide and a superfolder green fluorescent protein can stimulate long lasting immune responses to an inserted peptide. In this report, we further introduced split-GFP technology into VADEX and evaluated the role of the amphipathic helical peptide integrity, thermal stability of PNP and the effect of self-adjuvant in antibody affinity maturation of this new platform, VADEX-pro. Our result shows the significance of amphipathic helical peptide sequence integrity in PNP assembly and the thermal stability. The immunological results provide the first evidence that the VADEX-pro PNP possess a self-adjuvant activity that is superior to a clinical stage adjuvant when evaluating the antibody binding affinity. Application of VADEX-pro based protein nanoparticle in vaccine and therapeutic antibody development will likely improve the quality of humoral immune responses.

Enhancing H11 Protein-Induced Immune Protection Against Haemonchus contortus in Goats: A Nano-Adjuvant Formulation Strategy

The only vaccine against Haemonchus contortus is limited by short-lived antibody persistence and the need for frequent booster immunizations. This study leveraged the advantages of nano-adjuvants in enhancing antigen presentation and immune regulation to evaluate the efficacy of novel adjuvants (IMX, AddaS03) and the conventional QuilA combined with H11 protein. Goats were divided into four groups (IMX + H11, AddaS03 + H11, QuilA + H11, and infected control). They were immunized three times and challenged with 6000 infective third-stage larvae (iL3s) of H. contortus on the day of the third immunization, with the experiment lasting for 98 days. The results showed that vaccination with IMX + H11 conferred the strongest protection, demonstrating 88.3% efficacy in fecal egg count (FEC) reduction and 75.8% efficacy against worm burden, followed by QuilA + H11 (85.2% FEC reduction and 68% worm burden reduction) and AddaS03 + H11 (79.4% FEC reduction and 61.3% worm burden reduction). Serum IgG analysis revealed high antibody levels in all immunized groups. Cytokine detection found that IMX + H11 significantly upregulated IL-2 and IFN-γ expression in PBMCs and TNF-α expression in splenocytes, activating Th1-type responses and immune memory. QuilA + H11 showed weaker Th1 activation, and AddaS03 + H11 faced limitations due to insufficient antibody persistence for long-term protection. These findings suggest that IMX can induce highly efficient humoral and cellular immunity, providing a new direction for the optimization of H. contortus vaccines and suggesting the importance of nano-adjuvants for precise regulation of immune patterns.

The recent advances in vaccine adjuvants

Vaccine adjuvants, as key components in enhancing vaccine immunogenicity, play a vital role in modern vaccinology. This review systematically examines the historical evolution and mechanisms of vaccine adjuvants, with particular emphasis on innovative advancements in aluminum-based adjuvants, emulsion-based adjuvants, and nucleic acid adjuvants (e.g., CpG oligonucleotides). Specifically, aluminum adjuvants enhance immune responses through particle formation/antigen adsorption, inflammatory cascade activation, and T-cell stimulation. Emulsion adjuvants amplify immunogenicity via antigen depot effects and localized inflammation, while nucleic acid adjuvants like CpG oligonucleotides directly activate B cells and dendritic cells to promote Th1-type immune responses and memory T-cell generation. The article further explores the prospective applications of these novel adjuvants in combating emerging pathogens (including influenza and SARS-CoV-2), particularly highlighting their significance in improving vaccine potency and durability. Moreover, this review underscores the critical importance of adjuvant development in next-generation vaccine design and provides theoretical foundations for creating safer, effective adjuvant.

Nanovehicles for delivery of antigens and adjuvants as cancer nanovaccines

Cancer vaccines offer a promising strategy for immunotherapy by stimulating the immune system to target and destroy cancer cells. Antigens and adjuvants have been recognized as important components for the preparation of cancer vaccines, with antigens as the keys for immune cells to recognize cancer cells and adjuvants stimulating potent immune effects. Nanovehicles offer great potential advantages for construction of cancer vaccines, including enhanced antigen loading, co-assembly of antigens and adjuvants, targeted delivery, and antigen and adjuvant effects. By leveraging diverse nanovehicles, along with tumor antigens and/or adjuvants, various cancer nanovaccines have been developed, resulting in enhanced immune responses and facilitating the creation of personalized vaccines. This review presents the progress of cancer nanovaccines in clinical trials, systematically summarizing the physicochemical properties and roles of nanovehicles in the delivery of antigens and adjuvants as cancer nanovaccines, including inorganic nanoparticles, polymeric nanovehicles, nanoengineered coordination polymers, lipid nanovehicles, biomimetic nanovehicles, virus-like particles, and self-assembled peptide vehicles. We further discuss challenges in clinical translation and provide insights into future advancements in cancer nanovaccines.

Cellular immune signatures and differences of four porcine circovirus type 2 vaccines to heterologous PCV2d infection

Multiple PCV2 vaccines originating from different antigens and formula are commercially available and have shown great effectiveness in protecting pigs from clinical disease. However, our understanding of the immune mechanisms underlying these vaccine-induced protection is fairly limited, except for antibody responses. Head-to-head comparisons of T-cell responses induced by these vaccines in pigs would provide valuable insights into the mechanisms of protective immunity against PCV2. Here, T-cell responses in peripheral blood of pigs after vaccination with four representative PCV2 vaccines, as well as local and systemic recall responses following challenge with a PCV2d strain were examined. All four PCV2 vaccines induce a rapid cellular immune response that could be detected as early as 7 days post-vaccination. Some vaccine-primed CD4 T cells exhibit multifunctionality, being capable of secreting double (IFNγ/TNFα) and even triple cytokines (IFNγ/TNFα/IL-2) simultaneously. In contrast, a weak CD8 T cell response was also detected in the vaccinated pigs but just IFNγ/TNFα double producer and lack of cytotoxicity. These vaccine-activated CD4 and CD8 T cells displayed phenotypes of effector memory or terminally-differentiated effector memory T cells, which rapidly expand to subsequent PCV2d challenges. Prior-vaccinated pigs exhibited a stronger T cell cytokine response post-challenge, being most evident in the spleen. Notably, the cellular immune response induced by different types of PCV2 vaccines exhibited high similarity in phenotypic and functional properties, while showing significant differences in kinetics and magnitude. These results advance our understanding of cell-mediated immune protection afforded by different PCV2 vaccines and unravel fundamental differences in cellular immune response induced by PCV2 vaccines utilizing diverse technologies.

Bioinspired Membrane-Based Cancer Vaccines for Immunotherapy: Progress and Perspectives

Cancer vaccines hold promise for tumor immunotherapy, with their success hinging on effective systems to boost anti-tumor immunity. Biological membranes are not only a delivery vehicle but also a source of antigens and adjuvants, garnering growing interest in vaccine research. This review starts with an introduction to the composition and mechanisms of cancer vaccines and describes the sources, advantages/disadvantages, engineering strategies, and applications of these membrane-based platforms for cancer vaccine development. This review also offers a critical analysis and discusses the further direction of the vaccine platform in view of clinical translation for tumor immunotherapy.

Multi-disciplinary approaches paving the way for clinically effective peptide vaccines for cancer

Cytotoxic CD8+ T lymphocyte (CTL) cells are central in mediating antitumor immunity. Induction of a robust CTL response requires, CTL interaction with professional antigen-presenting cells, such as dendritic cells, displaying onco-antigenic peptide, often derived from tumor-associated antigens (TAAs) or neoantigens, and costimulation via CD4+ T helper cells which then elicits an effector and memory immune response that targets and kills cancer cells. Despite the tumoricidal capacity of CTLs, cancer cells can escape immune surveillance and killing due to their immunosuppressive tumor microenvironment (TME). Therefore, to harness the CTL immune response and combat the effect of the TME, peptide-based T cell vaccines targeting specific onco-antigens, conjugated with adjuvants are a subject of ongoing research for cancer immunotherapy; particularly, multi-peptide vaccines, containing both CTL and CD4+ T helper cell epitopes along with an immunostimulant. Historically, peptide-based T cell vaccines have been investigated as a potential strategy for cancer immunotherapy. Despite initial enthusiasm, these peptide vaccines have not demonstrated success in clinical outcomes. However, recent advancements in our understanding of cancer immunology and the design of peptide vaccines targeting specific tumor antigens have paved the way for novel strategies in peptide-based immunotherapy. These advancements have reignited optimism surrounding the potential of peptide-based vaccines as a viable cancer therapeutic. This review explores the new strategies and discusses the exciting possibilities they offer. Specifically, this review develops an understanding of vaccine design and clinical outcomes, by discussing mechanisms of CTL effector and memory responses, and how peptide-based vaccines can induce and enhance these responses. It addresses the challenge of Major Histocompatibility Complex (MHC) restriction, which limits the effectiveness of traditional peptide vaccines in individuals with diverse MHC types. It also delves into the immunosuppressive tumor microenvironment and overcoming its inhibitory effects using peptide-based vaccines for efficient cancer cell elimination. The review aims to provide an understanding of the complexities faced by each field in vaccine design, enhancing dialogue and understanding among researchers by bringing together the chemistry of vaccine synthesis, cancer immunology, and clinical studies to support the development of a peptide-based vaccine.

Constructions and immunogenicity evaluations of two porcine epdemic diarrhea virus-like particle vaccines

Porcine epidemic diarrhea virus (PEDV), a swine enteropathogenic coronavirus, causing acute diarrhea, dehydration, and up to 100 % mortality in neonatal suckling piglets, leading to huge economic losses in the global swine industry. Vaccination remains the most promising and effective way to prevent and control PEDV. In this study, we produced PEDV virus-like particles (VLPs) composed of S, M, and E proteins with a baculovirus expression system and a mammalian expression system. The S, M, and E proteins were effectively expressed and successfully assembled into VLPs. Subsequently, S subunits and commercially inactivated vaccines were selected and compared with two VLPs vaccines for immune efficacy through mouse immunization. The results showed that both VLPs induced higher levels of IgG, IgA, and neutralizing antibody titers, lymphocyte proliferation indexes and T, B cell ratios. Compared with the baculovirus VLPs, the mammalian VLPs exhibited better effects in inducing neutralizing antibodies, lymphocyte proliferations, and IFN-γ. These data indicated that the PEDV VLPs vaccine constructed using the mammalian expression system has better immune efficacy and has the potential to serve as a novel PEDV vaccine.

Nanotechnology-based strategies for vaccine development: accelerating innovation and delivery

The key role and impact of nanotechnology in vaccine development became particularly prominent following the outbreak of the coronavirus disease 2019 (COVID-19) pandemic in 2019. Especially in the process of designing and optimising COVID-19 vaccines, the application of nanomaterials significantly accelerated vaccine development and efficient delivery. In this review, we categorised and evaluated conventional vaccines, including attenuated live vaccines, inactivated vaccines, and subunit vaccines, highlighting their advantages and limitations. We summarised the development history, mechanisms, and latest technologies of vaccine adjuvants, emphasising their critical role in immune responses. Furthermore, we focused on the application of nanotechnology in the vaccine field, detailing the characteristics of nanoparticle vaccines, including virus-like particles, lipid-based carriers, inorganic nanoparticles, and polymer-based carriers. We emphasised their potential advantages in enhancing vaccine stability and immunogenicity, as well as their ability to deliver vaccines and present antigens through various routes. Despite facing challenges such as low drug loading efficiency, issues with long-term storage, high costs, and difficulties in large-scale production, nano-vaccines hold promise for the future. This review underscores the pivotal role and prospects of nanotechnology in vaccine development, offering new pathways and strategies to address current and future disease challenges.

Exploring Clec9a in dendritic cell-based tumor immunotherapy for molecular insights and therapeutic potentials

The pivotal role of type 1 conventional dendritic cells (cDC1s) in the field of dendritic cell (DC)-based tumor immunotherapies has been gaining increasing recognition due to their superior antigen cross-presentation abilities and essential role in modulating immune responses. This review specifically highlights the C-type lectin receptor family 9 member A (Clec9a or DNGR-1), which is exclusively expressed on cDC1s and plays a pivotal role in augmenting antigen cross-presentation and cytotoxic T lymphocyte (CTL) responses while simultaneously mitigating off-target effects. These effects include the enhancement of the cDC1s cross-presentation, reducing autoimmune responses and systemic inflammation, as well as preventing the non-specific activation of other immune cells. Consequently, these actions may contribute to reduced toxicity and enhanced treatment efficacy in immunotherapy. The exceptional ability of Clec9a to cross-present dead cell-associated antigens and enhance both humoral and CTL responses makes it an optimal receptor for DC-based strategies aimed at strengthening antitumor immunity. This review provides a comprehensive overview of the molecular characterization, expression, and signaling mechanisms of Clec9a. Furthermore, it discusses the role of Clec9a in the induction and functional activation of Clec9a+ cDC1s, with a particular focus on addressing the challenges related to off-target effects and immune tolerance in the development of tumor vaccines. Additionally, this review explores the potential of Clec9a-targeted approaches to enhance the immunogenicity of tumor vaccines and addresses the utilization of Clec9a as a delivery target for specific agonists (such as STING agonists and αGC) to enhance their therapeutic effects. This novel approach leverages Clec9a's capacity to improve the precision and efficacy of these immunomodulatory molecules in tumor treatment. In summary, this review presents compelling evidence positioning Clec9a as a promising target for DC-based tumor immunotherapy, capable of enhancing the efficacy of vaccines and immune responses while minimizing adverse effects.

HLA I immunopeptidome of synthetic long peptide pulsed human dendritic cells for therapeutic vaccine design

Synthetic long peptides (SLPs) are a promising vaccine modality that exploit dendritic cells (DC) to treat chronic infections or cancer. Currently, the design of SLPs relies on in silico prediction and multifactorial T cells assays to determine which SLPs are best cross-presented on DC human leukocyte antigen class I (HLA-I). Furthermore, it is unknown how TLR ligand-based adjuvants affect DC cross-presentation. Here, we generated a unique, high-quality immunopeptidome dataset of human DCs pulsed with 12 hepatitis B virus (HBV)-based SLPs combined with either a TLR1/2 (Amplivant®) or TLR3 (PolyI:C) ligand. The obtained immunopeptidome reflected adjuvant-induced differences, but no differences in cross-presentation of SLPs. We uncovered dominant (cross-)presentation on B-alleles, and identified 33 unique SLP-derived HLA-I peptides, several of which were not in silico predicted and some were consistently found across donors. Our work puts forward DC immunopeptidomics as a valuable tool for therapeutic vaccine design.

The contributions of T cell-mediated immunity to protection from vaccine-preventable diseases: A primer

In the face of the ever-present burden of emerging and reemerging infectious diseases, there is a growing need to comprehensively assess individual- and population-level immunity to vaccine-preventable diseases (VPDs). Many of these efforts, however, focus exclusively on antibody-mediated immunity, ignoring the role of T cells. Aimed at clinicians, public health practioners, and others who play central roles in human vaccine research but do not have formal training in immunology, we review how vaccines against infectious diseases elicit T cell responses, what types of vaccines elicit T cell responses, and how T cell responses are measured. We then use examples to demonstrate six ways that T cells contribute to protection from VPD, including directly mediating protection, enabling antibody responses, reducing disease severity, increasing cross-reactivity, improving durability, and protecting special populations. We conclude with a discussion of challenges and solutions to more widespread consideration of T cell responses in clinical vaccinology.

A Pool of Bacterium-like Particles Displaying African Swine Fever Virus Antigens Induces Both Humoral and Cellular Immune Responses in Pigs

BACKGROUND/OBJECTIVES

African swine fever (ASF), caused by African swine fever virus (ASFV), poses a significant threat to the global swine industry. This underscores the urgent need for safe and effective ASF vaccines.

METHODS

Here, we constructed five bacterium-like particles (BLPs) that each display one of the five ASFV antigens (F317L, H171R, D117L, B602L, and p54) based on the Gram-positive enhancer matrix-protein anchor (GEM-PA) system. GEM is a bacterial particle that contains only peptidoglycan, while PA is composed of three lysin motifs (Lysm) derived from the C-terminus of the AcmA protein, capable of non-covalently binding to GEM. By fusing the ASFV antigens with PA, the ASFV antigens can be firmly attached to the surface of GEM. Subsequently, the piglets were immunized via intramuscular injection with a mixture of BLPs-F317L, BLPs-H171R, BLPs-D117L, BLPs-B602L, and BLPs-p54.

RESULTS

The results showed that the piglets developed detectable serum IgG antibodies 2 weeks after the first immunization, and these high antibody levels were maintained 4 weeks after the booster immunization. Moreover, these piglets produced more IFN-γ-producing lymphocytes than the control piglets.

CONCLUSIONS

The data indicate that the generated BLPs mixture can stimulate both humoral and cellular immune responses in piglets, these five ASFV proteins are promising antigens, and the BLPs generated represent candidate ASF vaccines.

Advancements in Nanoparticle-Based Adjuvants for Enhanced Tuberculosis Vaccination: A Review

Tuberculosis (TB) remains a leading cause of morbidity and mortality worldwide, necessitating the development of more effective vaccines. Nanoparticle-based adjuvants represent a promising approach to enhancing tuberculosis vaccine efficacy. This review focuses on the advantages of nanoparticulate-loaded vaccines, emphasizing their ability to improve antigen delivery, safety, and immunogenicity. We discuss the various types of nanoparticles and their unique physicochemical properties that contribute to improved antigen delivery and sustained immune activation. Additionally, we highlight the advantages of nanoparticle-based adjuvants in inducing strong cellular and humoral immunity, enhancing vaccine stability, and reducing adverse effects. Finally, we address current challenges and future perspectives in the application of these novel adjuvants, emphasizing their potential to transform TB vaccine strategies and ultimately contribute to better global health outcomes.

Basic Properties and Development Status of Aluminum Adjuvants Used for Vaccines

BACKGROUND

Aluminum adjuvants, renowned for their safety and efficacy, act as excellent adsorbents and vaccine immunogen enhancers, significantly contributing to innate, endogenous, and humoral immunity. An ideal adjuvant not only boosts the immune response but also ensures optimal protective immunity. Aluminum adjuvants are the most widely used vaccine adjuvants and have played a crucial role in both the prevention of existing diseases and the development of new vaccines. With the increasing emergence of new vaccines, traditional immune adjuvants are continually being researched and upgraded. The future of vaccine development lies in the exploration and integration of novel adjuvant technologies that surpass the capabilities of traditional aluminum adjuvants. One promising direction is the incorporation of nanoparticles, which offer precise delivery and controlled release of antigens, thereby enhancing the overall immune response.

CONCLUSIONS

This review summarizes the types, mechanisms, manufacturers, patents, advantages, disadvantages, and future prospects of aluminum adjuvants. Although aluminum adjuvants have certain limitations, their contribution to enhancing vaccine immunity is significant and cannot be ignored. Future research should continue to explore their mechanisms of action and address potential adverse reactions to achieve improved vaccine efficacy.

Effects of adding antibiotics to an inactivated oil-adjuvant avian influenza vaccine on vaccine characteristics and chick health

During poultry immunization, antibiotics are typically added to inactivated oil-adjuvant avian influenza (AI) vaccines. Here, we evaluated the effects of adding ceftiofur, a third-generation cephalosporin, to an AI vaccine on vaccine stability and structure and on chick growth, immune efficacy, blood concentrations, biochemical and immunological indices, and gut microbiota. The results demonstrated that neither aqueous ceftiofur sodium nor ceftiofur hydrochloride oil emulsion formed a stable mixture with the vaccine. Adding ceftiofur formulations, particularly ceftiofur hydrochloride, at >4% significantly destabilized the vaccine's water-in-oil structures. Adding ceftiofur also increased vaccine malabsorption at the injection site; specifically, adding ceftiofur hydrochloride reduced H5N8 and H7N9 antibody titers after the first immunization (P < 0.05) and H7N9 antibody titers after the second immunization (P < 0.01). Serum drug concentrations did not differ significantly between the groups with ceftiofur sodium and hydrochloride addition. Ceftiofur addition increased postvaccination chick weight loss; compared with the vaccine alone, ceftiofur sodium-vaccine mixture increased chick weight significantly (P < 0.05). Ceftiofur addition also increased stress indices and reduced antioxidant capacity significantly (P < 0.05 or P < 0.01). Vaccination-related immune stress reduced gut microbiota diversity in chicks; ceftiofur addition reversed this change. AI vaccine immunization significantly reduced the relative abundance of Lactobacillus and Muribaculaceae but significantly increased that of Bacteroides and Eubacterium coprostanoligenes group. Ceftiofur addition restored the gut microbiota structure; in particular, ceftiofur hydrochloride addition significantly increased the abundance of the harmful gut microbes Escherichia-Shigella and Enterococcus, whereas ceftiofur sodium addition significantly reduced it. The changes in gut microbiota led to alterations in metabolic pathways related to membrane transport, amino acids, and carbohydrates. In conclusion, adding ceftiofur to the AI vaccine had positive effects on chick growth and gut microbiota modulation; however, different antibiotic concentrations and formulations may disrupt vaccine structure, possibly affecting vaccine safety and immunization efficacy. Thus, the addition of antibiotics to oil-adjuvant vaccines is associated with a risk of immunization failure and should be applied to poultry with caution.

Evaluating the breadth of nucleic acid-based payloads delivered in lipid nanoparticles to establish fundamental differences in development

INTRODUCTION

Nucleic acid (NA)-based therapeutics have shown great potential for downregulating or augmenting gene expression, and for promising applications, e.g., protein-replacement therapy and vaccination, a comprehensive understanding of the requirements for their targeted delivery to specific tissues or cells is needed.

AREAS COVERED

In this review, we discuss clinical applications of four representative types of NA-based therapeutics, i.e. antisense oligonucleotides, small interfering RNA, messenger RNA, and circular RNA, with a focus on the lipid nanoparticle (LNP) technology used for intracellular delivery. The in vivo fate of LNPs is discussed to improve the understanding of trafficking of nanomedicines at the systemic and cellular levels. In addition, NA-based vaccines are discussed, focusing on targeting antigen-presenting cells and immune activation.

EXPERT OPINION

Optimization of delivery systems for NA-based therapeutics is mainly focused on the standard requirements of prolonged systemic circulation and enhancing endosomal escape. Depending on the final destination in specific target tissues or cells, strategies should be adjusted to achieve the desired biodistribution of NA-based payloads. More studies relating to the pharmacokinetics of both cargo and carrier are encouraged, because their in vivo fates may differ, considering the possibility of premature cargo release before reaching the target.

Application of biomimetic nanovaccines in cancer immunotherapy: A useful strategy to help combat immunotherapy resistance

Breakthroughs in actual clinical applications have begun through vaccine-based cancer immunotherapy, which uses the body's immune system, both humoral and cellular, to attack malignant cells and fight diseases. However, conventional vaccine approaches still face multiple challenges eliciting effective antigen-specific immune responses, resulting in immunotherapy resistance. In recent years, biomimetic nanovaccines have emerged as a promising alternative to conventional vaccine approaches by incorporating the natural structure of various biological entities, such as cells, viruses, and bacteria. Biomimetic nanovaccines offer the benefit of targeted antigen-presenting cell (APC) delivery, improved antigen/adjuvant loading, and biocompatibility, thereby improving the sensitivity of immunotherapy. This review presents a comprehensive overview of several kinds of biomimetic nanovaccines in anticancer immune response, including cell membrane-coated nanovaccines, self-assembling protein-based nanovaccines, extracellular vesicle-based nanovaccines, natural ligand-modified nanovaccines, artificial antigen-presenting cells-based nanovaccines and liposome-based nanovaccines. We also discuss the perspectives and challenges associated with the clinical translation of emerging biomimetic nanovaccine platforms for sensitizing cancer cells to immunotherapy.

Porphyromonas gingivalis Vaccine: Antigens and Mucosal Adjuvants

Porphyromonas gingivalis (Pg), a Gram-negative anaerobic bacterium found in dental plaque biofilm within periodontal pockets, is the primary pathogenic microorganism responsible for chronic periodontitis. Infection by Pg significantly impacts the development and progression of various diseases, underscoring the importance of eliminating this bacterium for effective clinical treatment. While antibiotics are commonly used to combat Pg, the rise of antibiotic resistance poses a challenge to complete eradication. Thus, the prevention of Pg infection is paramount. Research suggests that surface antigens of Pg, such as fimbriae, outer membrane proteins, and gingipains, can potentially be utilized as vaccine antigens to trigger protective immune responses. This article overviews these antigens, discusses advancements in mucosal adjuvants (including immunostimulant adjuvants and vaccine-delivery adjuvants), and their application in Pg vaccine development. Furthermore, the review examines the advantages and disadvantages of different immune pathways and common routes of Pg vaccine immunization. By summarizing the current landscape of Pg vaccines, addressing existing challenges, and highlighting the potential of mucosal vaccines, this review offers new insights for the advancement and clinical implementation of Pg vaccines.

A ferritin nanoparticle vaccine based on the hemagglutinin extracellular domain of swine influenza A (H1N1) virus elicits protective immune responses in mice and pigs

Introduction

Swine influenza viruses (SIVs) pose significant economic losses to the pig industry and are a burden on global public health systems. The increasing complexity of the distribution and evolution of different serotypes of influenza strains in swine herds escalates the potential for the emergence of novel pandemic viruses, so it is essential to develop new vaccines based on swine influenza.

Methods

Here, we constructed a self-assembling ferritin nanoparticle vaccine based on the hemagglutinin (HA) extracellular domain of swine influenza A (H1N1) virus using insect baculovirus expression vector system (IBEVS), and after two immunizations, the immunogenicities and protective efficacies of the HA-Ferritin nanoparticle vaccine against the swine influenza virus H1N1 strain in mice and piglets were evaluated.

Results

Our results demonstrated that HA-Ferritin nanoparticle vaccine induced more efficient immunity than traditional swine influenza vaccines. Vaccination with the HA-Ferritin nanoparticle vaccine elicited robust hemagglutinin inhibition titers and antigen-specific IgG antibodies and increased cytokine levels in serum. MF59 adjuvant can significantly promote the humoral immunity of HA-Ferritin nanoparticle vaccine. Furthermore, challenge tests showed that HA-Ferritin nanoparticle vaccine conferred full protection against lethal challenge with H1N1 virus and significantly decreased the severity of virus-associated lung lesions after challenge in both BALB/c mice and piglets.

Conclusion

Taken together, these results indicate that the hemagglutinin extracellular-based ferritin nanoparticle vaccine may be a promising vaccine candidate against SIVs infection.

Evaluation of different types of adjuvants in a malaria transmission-blocking vaccine

Adjuvants are critical components for vaccines, which enhance the strength and longevity of the antibody response and influence the types of immune response. Limited research has been conducted on the immunogenicity and protective efficacy of various adjuvants in malaria transmission-blocking vaccines (TBVs). In this study, we formulated a promising TBV candidate antigen, the P. berghei ookinete surface antigen PSOP25, with different types of adjuvants, including the TLR4 agonist monophosphoryl lipid A (MPLA), the TLR9 agonist cytosine phosphoguanosine oligodeoxynucleotides (CpG ODN 1826) (CpG), a saponin adjuvant QS-21, aluminum hydroxide (Alum), and two combination adjuvants MPLA + QS-21 and QS-21 + CpG. We demonstrated that adjuvanted vaccines results in elevated elicited antibody levels, increased proliferation of plasma cells, and efficient formation of germinal centers (GCs), leading to enhanced long-term protective immune responses. Furthermore, CpG group exhibited the most potent inhibition of ookinete formation and transmission-blocking activity. We found that the rPSOP25 with CpG adjuvant was more effective than MPLA, QS-21, MPLA + QS-21, QS-21 + CpG adjuvants in dendritic cells (DCs) activation and differentiation. Additionally, the CpG adjuvant elicited more rubust immune memory response than Alum adjuvant. CpG and QS-21 adjuvants could activate the Th1 response and promote the secretion of IFN-γ and TNF-α. PSOP25 induced a higher number of Tfh cells in splenocytes when combined with MPLA, CpG, and QS-21 + CpG; and there was no increase in these cell populations when PSOP25 was administered with Alum. In conclusion, CpG may confer enhanced efficacy for the rPSOP25 vaccine, as evidenced by the ability of the elicited antisera to induce protective immune responses and improved transmission-blocking activity.

Boosting the immunogenicity of the CoronaVac SARS-CoV-2 inactivated vaccine with Huoxiang Suling Shuanghua Decoction: a randomized, double-blind, placebo-controlled study

Introduction

In light of the public health burden of the COVID-19 pandemic, boosting the safety and immunogenicity of COVID-19 vaccines is of great concern. Numerous Traditional Chinese medicine (TCM) preparations have shown to beneficially modulate immunity. Based on pilot experiments in mice that showed that supplementation with Huoxiang Suling Shuanghua Decoction (HSSD) significantly enhances serum anti-RBD IgG titers after inoculation with recombinant SARS-CoV-2 S-RBD protein, we conducted this randomized, double-blind, placebo-controlled clinical trial aimed to evaluate the potential immunogenicity boosting effect of oral HSSD after a third homologous immunization with Sinovac's CoronaVac SARS-CoV-2 (CVS) inactivated vaccine.

Methods

A total of 70 participants were randomly assigned (1:1 ratio) to receive a third dose of CVS vaccination and either oral placebo or oral HSSD for 7 days. Safety aspects were assessed by recording local and systemic adverse events, and by blood and urine biochemistry and liver and kidney function tests. Main outcomes evaluated included serum anti-RBD IgG titer, T lymphocyte subsets, serum IgG and IgM levels, complement components (C3 and C4), and serum cytokines (IL-6 and IFN-γ). In addition, metabolomics technology was used to analyze differential metabolite expression after supplementation with HSSD.

Results

Following a third CVS vaccination, significantly increased serum anti-RBD IgG titer, reduced serum IL-6 levels, increased serum IgG, IgM, and C3 and C4 levels, and improved cellular immunity, evidenced by reduce balance deviations in the distribution of lymphocyte subsets, was observed in the HSSD group compared with the placebo group. No serious adverse events were recorded in either group. Serum metabolomics results suggested that the mechanisms by which HSSD boosted the immunogenicity of the CVS vaccine are related to differential regulation of purine metabolism, vitamin B6 metabolism, folate biosynthesis, arginine and proline metabolism, and steroid hormone biosynthesis.

Conclusion

Oral HSSD boosts the immunogenicity of the CVS vaccine in young and adult individuals. This trial provides clinical reference for evaluation of TCM immunomodulators to improve the immune response to COVID-19 vaccines.

Chemical and biological characterization of vaccine adjuvant QS-21 produced via plant cell culture

Many vaccines, including those using recombinant antigen subunits, rely on adjuvant(s) to enhance the efficacy of the host immune responses. Among the few adjuvants clinically approved, QS-21, a saponin-based immunomodulatory molecule isolated from the tree bark of Quillaja saponaria (QS) is used in complex formulations in approved effective vaccines. High demand of the QS raw material as well as manufacturing scalability limitation has been barriers here. We report for the first-time successful plant cell culture production of QS-21 having structural, chemical, and biologic, properties similar to the bark extracted product. These data ensure QS-21 and related saponins are broadly available and accessible to drug developers.

Construction and expression of Mycobacterium tuberculosis fusion protein SHR3 and its immunogenicity analysis in combination with various adjuvants

Tuberculosis (TB) today remains the leading cause of global deaths due to infectious bacterial pathogens. The Bacillus Calmette-Guérin (BCG) vaccine is the only vaccine clinically used to prevent TB. However, its limitations in preventing latent infection and TB reactivation mean that it does not provide comprehensive protection. In this study, we successfully constructed and expressed the multistage fusion protein, SHR3, and used whole blood IFN-γ release assay (WBIA) with flow cytometry to detect antigen specificity, further confirmed by enzyme-linked immunosorbent assay (ELISA). SHR3 and its subfractional proteins stimulated the level of IFN-γ production by lymphocytes from M. tb-infected patients, inducing the production of single-positive and double-positive CD4+ and CD8+ T cells with IFN-γ and IL-2, at levels significantly higher than those of healthy controls. The fusion protein and complex adjuvant group (SHR3/DMT) induced mice to produce significantly higher levels of IgG antibodies and their subclasses, with IgG2a/IgG1 results showing a convergent Th1-type response; mice in the BCG + SHR3/DMT group induced secretion of the highest levels of IL-2, and TNF-α, irrespective of stimulation with purified protein derivative or SHR3. These findings suggest that SHR3/DMT could be a potential subunit vaccine candidate that may serve as an effective booster vaccine after BCG primary immunization.

Bovine serum albumin nanoparticles containing Poly (I:C) can enhance the neutralizing antibody response induced by envelope protein of Orthoflavivirus zikaense

Since the Orthoflavivirus zikaense (ZIKV) has been considered a risk for Zika congenital syndrome development, developing a safe and effective vaccine has become a high priority. Numerous research groups have developed strategies to prevent ZIKV infection and have identified the domain III of the ZIKV envelope protein (zEDIII) as a promising target. Subunit antigens are often poorly immunogenic, necessitating the use of adjuvants and/or delivery systems to induce optimal immune responses. The subject of nanotechnology has substantial expansion in recent years in terms of research and applications. Nanoparticles could be used as drug delivery systems and to increase the immunogenicity and stability of a given antigen. This work aims to characterize and validate the potential of a vaccine formulation composed of domain zEDIII and bovine serum albumin nanoparticles containing polyinosinic-polycytidylic acid (NPPI). NPPI were uptake in vitro by immature bone marrow dendritic cells and histological analysis of the skin of mice treated with NPPI showed an increase in cellularity. Immunization assay showed that mice immunized with zEDIII in the presence of NPPI produced neutralizing antibodies. Through the passive transfer of sera from immunized mice to ZIKV-infected neonatal mice, it was demonstrated that these antibodies provide protection, mitigating weight loss, clinical or neurological signs induced by infection, and significantly increased survival rates. Protection was further substantiated by the reduction in the number of viable infectious ZIKV, as well as a decrease in inflammatory cytokines and tissue alterations in the brains of infected mice. Taken together, data presented in this study shows that NPPI + zEDIII is a promising vaccine candidate for ZIKV.

Immunogenicity and protective efficacy of a trimeric full-length S protein subunit vaccine for porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) has caused serious economic losses to the pig husbandry worldwide, and the effects of existing commercialized vaccines are suboptimal. Therefore, research to develop an efficacious vaccine for prevention and control of PEDV is essential. In this study, we designed and produced trimerized proteins of full-length PEDV spike (S) protein, S1 subunit, and a tandem of multiple epitopes of S protein using an efficient mammalian expression vector system in HEK 293F cells. The immunogenicity of two commercial adjuvants, M401 and M103, was also evaluated in mice. Enzyme-linked immunosorbent assays demonstrated that all immunized mice generated highly systemic PEDV S-specific IgG and IgA antibodies. Mice in S/M103-immunized group generated the highest neutralizing antibody titer with 1:96. Compared with control group, the subunit vaccines elicited multifunctional CD3+CD4+ and CD3+CD8+ T cells, B220+CD19+ B cells, and CD3-CD49b+ natural killer cells in the spleen. PEDV S/M103 vaccine, which had the best immune effect, was selected for further evaluation in piglets. Immunization with S/M103 vaccine induced high levels of S-specific IgG, IgA, and neutralizing antibodies, and increased the proliferation of peripheral blood mononuclear cells and the expression levels of interferon-γ and interleukin-4 in peripheral blood of piglets. Virus challenge test results showed significantly lower diarrheal index scores and fecal viral loads, and less pathological damage to the intestines in S/M103-immunized piglets than in controls, indicating that S/M103 provides good protection against the virulent virus challenge. Our findings suggest that trimeric PEDV S/M103 has potential as a clinical vaccine candidate.

Azoximer bromide and hydroxyapatite: promising immune adjuvants in cancer

Immune adjuvants are immune modulators that have been developed in the context of infectious vaccinations. There is currently a growing interest in immune adjuvants due to the development of immunotherapy against cancers. Immune adjuvant mechanisms of action are focused on the initiation and amplification of the inflammatory response leading to the innate immune response, followed by the adaptive immune response. The main activity lies in the support of antigen presentation and the maturation and functions of dendritic cells. Most immune adjuvants are associated with a vaccine or incorporated into the new generation of mRNA vaccines. Few immune adjuvants are used as drugs. Hydroxyapatite (HA) ceramics and azoximer bromide (AZB) are overlooked molecules that were used in early clinical trials, which demonstrated clinical efficacy and excellent tolerance profiles. HA combined in an autologous vaccine was previously developed in the veterinary field for use in canine spontaneous lymphomas. AZB, an original immune modulator derived from a class of heterochain aliphatic polyamines that is licensed in Russia, the Commonwealth of Independent States, and Slovakia for infectious and inflammatory diseases, is and now being developed for use in cancer with promising results. These two immune adjuvants can be combined in various immunotherapy strategies.

Gaston Ramon's Big Four

When immunology was still in its infancy, Gaston Ramon made several major contributions to humoral immunology [...].

Mn(iii)-mediated carbon-centered radicals generate an enhanced immunotherapeutic effect

A strategy for designing cancer therapeutic nanovaccines based on immunogenic cell death (ICD)-inducing therapeutic modalities is particularly attractive for optimal therapeutic efficacy. In this work, a highly effective cancer therapeutic nanovaccine (denoted as MPL@ICC) based on immunogenic photodynamic therapy (PDT) was rationally designed and fabricated. MPL@ICC was composed of a nanovehicle of MnO2 modified with a host-guest complex using amino pillar[6]arene and lactose-pyridine, a prodrug of isoniazid (INH), and chlorine e6 (Ce6). The nanovaccine exhibited excellent biosafety, good targeting ability to hepatoma cells and enrichment at tumor sites. Most importantly, it could modulate the tumor microenvironment (TME) to facilitate the existence of Mn(iii) and Mn(iii)-mediated carbon-centered radical generation with INH released from the prodrug in situ to further strengthen ICD. This is the first report on Mn(iii)-mediated generation of carbon-centered radicals for successful anti-tumor immunotherapy using ICD, which provides a novel strategy for designing highly efficient cancer therapeutic nanovaccines.

The role of TNC in atherosclerosis and drug development opportunities

Tenascin C (TNC), a rich glycoprotein of the extracellular matrix, exhibits a pro-atherosclerosis or anti-atherosclerosis effect depending on its location. TNC, especially its C domain/isoform (TNC-C), is strongly overexpressed in atherosclerotic plaque active areas but virtually undetectable in most normal adult tissues, suggesting that TNC is a promising delivery vector target for atherosclerosis-targeted drugs. Many delivery vectors were investigated by recognizing TNC-C, including G11, G11-iRGD, TN11, PL1, and PL3. F16 and FNLM were also investigated by recognizing TNC-A1 and TNC, respectively. Notably, iRGD was undergoing clinical trials. PL1 not only recognizes TNC-C but also the extra domain-B (EDB) of fibronectin (FN), which is also a promising delivery vector for atherosclerosis-targeted drugs, and several conjugate agents are undergoing clinical trials. The F16-conjugate agent F16IL2 is undergoing clinical trials. Therefore, G11-iRGD, PL1, and F16 have great development value. Furthermore, ATN-RNA and IMA950 were investigated in clinical trials as therapeutic drugs and vaccines by targeting TNC, respectively. Therefore, targeting TNC could greatly improve the success rate of atherosclerosis-targeted drugs and/or specific drug development. This review discussed the role of TNC in atherosclerosis, atherosclerosis-targeted drug delivery vectors, and agent development to provide knowledge for drug development targeting TNC.

Tumor vaccines: Toward multidimensional anti-tumor therapies

For decades, immunotherapies have offered hope for patients with advanced cancer. However, they show distinct benefits and limited clinical effects. Tumor vaccines have the potential to prime tumor-antigen-specific T cells and induce broad subsets of immune responses, ultimately eradicating tumor cells. Here, we classify tumor vaccines by their anti-tumor mechanisms, which include boosting the immune system, overcoming tumor immunosuppression, and modulating tumor angiogenesis. We focus on multidimensional tumor vaccine strategies using combinations of two or three of the above mechanisms, as these are superior to single-dimensional treatments. This review offers a perspective on tumor vaccine strategies and the future role of vaccine therapies in cancer treatment.

Antigen cross-presentation in dendric cells: From bench to bedside

Cross-presentation (XPT) is an adaptation of the cellular process in which dendritic cells (DCs) present exogenous antigens on major histocompatibility complex (MHC) class I molecules for recognition of the cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, resulting in immunity or tolerance. Recent advances in DCs have broadened our understanding of the underlying mechanisms of XPT and strengthened their application in tumor immunotherapy. In this review, we summarized the known mechanisms of XPT, including the receptor-mediated internalization of exogenous antigens, endosome escape, engagement of the other XPT-related proteins, and adjuvants, which significantly enhance the XPT capacity of DCs. Consequently, various strategies to enhance XPT can be adopted and optimized to improve outcomes of DC-based therapy.

Increases in Cellular Immune Responses Due to Positive Effect of CVC1302-Induced Lysosomal Escape in Mice

This study found a higher percentage of CD8+ T cells in piglets immunized with a CVC1302-adjuvanted inactivated foot-and-mouth disease virus (FMDV) vaccine. We wondered whether the CVC1302-adjuvanted inactivated FMDV vaccine promoted cellular immunity by promoting the antigen cross-presentation efficiency of ovalbumin (OVA) through dendritic cells (DCs), mainly via cytosolic pathways. This was demonstrated by the enhanced levels of lysosomal escape of OVA in the DCs loaded with OVA and CVC1302. The higher levels of ROS and significantly enhanced elevated lysosomal pH levels in the DCs facilitated the lysosomal escape of OVA. Significantly enhanced CTL activity levels was observed in the mice immunized with OVA-CVC1302. Overall, CVC1302 increased the cross-presentation of exogenous antigens and the cross-priming of CD8+ T cells by alkalizing the lysosomal pH and facilitating the lysosomal escape of antigens. These studies shed new light on the development of immunopotentiators to improve cellular immunity induced by vaccines.

Mechanism of Innate Immune Response Induced by Albizia julibrissin Saponin Active Fraction Using C2C12 Myoblasts

Albizia julibrissin saponin active fraction (AJSAF), is a prospective adjuvant with dual Th1/Th2 and Tc1/Tc2 potentiating activity. Its adjuvant activity has previously been proven to be strictly dependent on its spatial co-localization with antigens, highlighting the role of local innate immunity in its mechanisms. However, its potential targets and pathways remain unclear. Here, its intracellular molecular mechanisms of innate immune response were explored using mouse C2C12 myoblast by integrative analysis of the in vivo and in vitro transcriptome in combination with experimental validations. AJSAF elicited a temporary cytotoxicity and inflammation towards C2C12 cells. Gene set enrichment analysis demonstrated that AJSAF regulated similar cell death- and inflammatory response-related genes in vitro and in vivo through activating second messenger-MAPK-CREB pathways. AJSAF markedly enhanced the Ca2+, cAMP, and reactive oxygen species levels and accelerated MAPK and CREB phosphorylation in C2C12 cells. Furthermore, Ca2+ chelator, CREB inhibitor, and MAPK inhibitors dramatically blocked the up-regulation of IL-6, CXCL1, and COX2 in AJSAF-treated C2C12 cells. Collectively, these results demonstrated that AJSAF induced innate immunity via Ca2+-MAPK-CREB pathways. This study is beneficial for insights into the molecular mechanisms of saponin adjuvants.

Natural polysaccharides exert anti-tumor effects as dendritic cell immune enhancers

With the development of immunotherapy, the process of tumor treatment is also moving forward. Polysaccharides are biological response modifiers widely found in plants, animals, fungi, and algae and are mainly composed of monosaccharides covalently linked by glycosidic bonds. For a long time, polysaccharides have been widely used clinically to enhance the body's immunity. However, their mechanisms of action in tumor immunotherapy have not been thoroughly explored. Dendritic cells (DCs) are a heterogeneous population of antigen presenting cells (APCs) that play a crucial role in the regulation and maintenance of the immune response. There is growing evidence that polysaccharides can enhance the essential functions of DCs to intervene the immune response. This paper describes the research progress on the anti-tumor immune effects of natural polysaccharides on DCs. These studies show that polysaccharides can act on pattern recognition receptors (PRRs) on the surface of DCs and activate phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT), mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), Dectin-1/Syk, and other signalling pathways, thereby promoting the main functions of DCs such as maturation, metabolism, antigen uptake and presentation, and activation of T cells, and then play an anti-tumor role. In addition, the application of polysaccharides as adjuvants for DC vaccines, in combination with adoptive immunotherapy and immune checkpoint inhibitors (ICIs), as well as their co-assembly with nanoparticles (NPs) into nano drug delivery systems is also introduced. These results reveal the biological effects of polysaccharides, provide a new perspective for the anti-tumor immunopharmacological research of natural polysaccharides, and provide helpful information for guiding polysaccharides as complementary medicines in cancer immunotherapy.

Dendritic cell vaccine trials in gliomas: Untangling the lines

Glioblastoma is a deadly brain tumor without any significantly successful treatments to date. Tumor antigen-targeted immunotherapy platforms including peptide and dendritic cell (DC) vaccines, have extended survival in hematologic malignancies. The relatively "cold" tumor immune microenvironment and heterogenous nature of glioblastoma have proven to be major limitations to translational application and efficacy of DC vaccines. Furthermore, many DC vaccine trials in glioblastoma are difficult to interpret due to a lack of contemporaneous controls, absence of any control comparison, or inconsistent patient populations. Here we review glioblastoma immunobiology aspects that are relevant to DC vaccines, review the clinical experience with DC vaccines targeting glioblastoma, discuss challenges in clinical trial design, and summarize conclusions and directions for future research for the development of effective DC vaccines for patients.

MDA5 with Complete CARD2 Region Inhibits the Early Replication of H9N2 AIV and Enhances the Immune Response during Vaccination

Chicken melanoma differentiation-associated gene 5 (MDA5) is a member of the RLRs family that recognizes the viral RNAs invading cells and activates downstream interferon regulatory pathways, thereby inhibiting viral replication. The caspase activation and recruitment domain (CARD) is the most important region in MDA5 protein. However, the antiviral and immune enhancement of MDA5 with the CARD region remains unclear. In this study, two truncated MDA5 genes with different CARD regions, namely MDA5-1 with CARD1 plus partial CARD2 domain and MDA5-2 with CARD1 plus complete CARD2 domain, were cloned via reverse transcription PCR and ligated into plasmid Flag-N vector to be Flag-MDA5-1 and Flag-MDA5-2 plasmids. DF-1 cells were transfected with two plasmids for 24 h and then inoculated with H9N2 virus (0.1 MOI) for 6 h to detect the levels of IFN-β, PKR, MAVS, and viral HA, NA, and NS proteins expression. The results showed that MDA5-1 and MDA5-2 increased the expression of IFN-β and PKR, activated the downstream molecule MAVS production, and inhibited the expression of HA, NA, and NS proteins. The knockdown of MDA5 genes confirmed that MDA5-2 had a stronger antiviral effect than that of MDA5-1. Furthermore, the recombinant proteins MDA5-1 and MDA5-2 were combined with H9N2 inactivated vaccine to immunize SPF chickens subcutaneously injected in the neck three times. The immune response of the immunized chicken was investigated. It was observed that the antibody titers and expressions of immune-related molecules from the chicken immunized with MDA5-1 and MDA5-2 group were increased, in which the inducing function of MDA5-2 groups was the highest among all immunization groups. These results suggested that the truncated MDA5 recombinant proteins with complete CARD2 region could play vital roles in antiviral and immune enhancement. This study provides important material for the further study of the immunoregulatory function and clinical applications of MDA5 protein.

Surface immunogenic protein from Streptococcus agalactiae and Fissurella latimarginata hemocyanin are TLR4 ligands and activate MyD88- and TRIF dependent signaling pathways

The development of vaccine adjuvants is of interest for the management of chronic diseases, cancer, and future pandemics. Therefore, the role of Toll-like receptors (TLRs) in the effects of vaccine adjuvants has been investigated. TLR4 ligand-based adjuvants are the most frequently used adjuvants for human vaccines. Among TLR family members, TLR4 has unique dual signaling capabilities due to the recruitment of two adapter proteins, myeloid differentiation marker 88 (MyD88) and interferon-β adapter inducer containing the toll-interleukin-1 receptor (TIR) domain (TRIF). MyD88-mediated signaling triggers a proinflammatory innate immune response, while TRIF-mediated signaling leads to an adaptive immune response. Most studies have used lipopolysaccharide-based ligands as TLR4 ligand-based adjuvants; however, although protein-based ligands have been proven advantageous as adjuvants, their mechanisms of action, including their ability to undergo structural modifications to achieve optimal immunogenicity, have been explored less thoroughly. In this work, we characterized the effects of two protein-based adjuvants (PBAs) on TLR4 signaling via the recruitment of MyD88 and TRIF. As models of TLR4-PBAs, we used hemocyanin from Fissurella latimarginata (FLH) and a recombinant surface immunogenic protein (rSIP) from Streptococcus agalactiae. We determined that rSIP and FLH are partial TLR4 agonists, and depending on the protein agonist used, TLR4 has a unique bias toward the TRIF or MyD88 pathway. Furthermore, when characterizing gene products with MyD88 and TRIF pathway-dependent expression, differences in TLR4-associated signaling were observed. rSIP and FLH require MyD88 and TRIF to activate nuclear factor kappa beta (NF-κB) and interferon regulatory factor (IRF). However, rSIP and FLH have a specific pattern of interleukin 6 (IL-6) and interferon gamma-induced protein 10 (IP-10) secretion associated with MyD88 and TRIF recruitment. Functionally, rSIP and FLH promote antigen cross-presentation in a manner dependent on TLR4, MyD88 and TRIF signaling. However, FLH activates a specific TRIF-dependent signaling pathway associated with cytokine expression and a pathway dependent on MyD88 and TRIF recruitment for antigen cross-presentation. Finally, this work supports the use of these TLR4-PBAs as clinically useful vaccine adjuvants that selectively activate TRIF- and MyD88-dependent signaling to drive safe innate immune responses and vigorous Th1 adaptive immune responses.

Research progress of nanovaccine in anti-tumor immunotherapy

Tumor vaccines aim to activate dormant or unresponsive tumor-specific T lymphocytes by using tumor-specific or tumor-associated antigens, thus enhancing the body's natural defense against cancer. However, the effectiveness of tumor vaccines is limited by the presence of tumor heterogeneity, low immunogenicity, and immune evasion mechanisms. Fortunately, multifunctional nanoparticles offer a unique chance to address these issues. With the advantages of their small size, high stability, efficient drug delivery, and controlled surface chemistry, nanomaterials can precisely target tumor sites, improve the delivery of tumor antigens and immune adjuvants, reshape the immunosuppressive tumor microenvironment, and enhance the body's anti-tumor immune response, resulting in improved efficacy and reduced side effects. Nanovaccine, a type of vaccine that uses nanotechnology to deliver antigens and adjuvants to immune cells, has emerged as a promising strategy for cancer immunotherapy due to its ability to stimulate immune responses and induce tumor-specific immunity. In this review, we discussed the compositions and types of nanovaccine, and the mechanisms behind their anti-tumor effects based on the latest research. We hope that this will provide a more scientific basis for designing tumor vaccines and enhancing the effectiveness of tumor immunotherapy.

Modification of the antigenicity of cancer cells by conjugates consisting of hyaluronic acid and foreign antigens

Tumor-specific cytotoxic T-lymphocytes (CTLs) recognize tumor-associated antigens presented on major histocompatibility complex (MHC) class I molecules. However, it is difficult to induce potent CTLs by vaccination because the antigenicity is not so high, compared with that of foreign antigens derived from viruses and microbes. The affinity of binding to MHC class I molecules is proportional to the antigenicity of the antigen that they are presenting. Here, we prepared several conjugates consisting of hyaluronic acid (HA) as a carrier to cancer cells and ovalbumin (OVA) as a foreign protein and changed the antigens on cancer cells from intrinsic antigens to OVA fragments. The conjugate containing multiple HA and OVA molecules (100k4HA-3OVA) adopted a highly condensed structure and was well recognized by recombinant CD44 molecules in quartz crystal microbalance analysis and incorporated into cancer cells (CT26 cells). A mixture of CT26 cells treated with 100k4HA-3OVA and splenocytes including OVA-specific CTLs induced abundant secretion of IFN-γ into the supernatant. At 48 h after mixing with the CTLs, almost all CT26 cells had died. These results indicate that 100k4HA-3OVA is actively internalized into the cells through interaction between HA and CD44. Subsequently, CT26 cells present not only self-antigens, but also OVA fragments on MHC class I molecules and are recognized by OVA-specific CTLs. We thus succeeded in modifying the antigenicity from self- to non-self-antigens on cancer cells. Therefore, this foreign-antigen delivery using HA to cancer cells, followed by antigen replacement, could be used as a novel strategy for treating cancers.

HER2/neu-based vaccination with li-Key hybrid, GM-CSF immunoadjuvant and trastuzumab as a potent triple-negative breast cancer treatment

PURPOSE

Constituting 15 to 20% of breast cancer cases, the triple-negative subtype lacks effective treatments as being less responsive to hormone-associated therapies. Alternatively, a more powerful immunotherapeutic vaccination can trigger immune recognition and destruction against breast cancer by incorporating oncological antigens such as human epidermal growth factor receptor 2 (HER2/neu). Currently, HER2/neu-based vaccines have finished three phases with breast cancer patients, in conjunction with granulocyte-macrophage colony-stimulating factor (GM-CSF) that was proven to be a promising vaccine adjuvant in other cancer trials previously.

METHODS

Completed HER2/neu-based vaccine trials with GM-CSF immunoadjuvants for breast cancer were summarised, and additionally, the article discussed prominent findings of vaccine effectiveness in triple-negative breast cancer, regarding li-Key hybrid in vaccine design and co-administration of anti-HER2/neu trastuzumab.

RESULTS

Nine clinical trials of three HER2/neu epitopes, one with li-Key hybrid, were analysed with or without the presence of trastuzumab. Immunological responses and minimal toxicities were observed in these epitopes, and disease-free survival was especially improved in the triple-negative population.

CONCLUSION

HER2/neu-based peptide vaccine is a safe and effective approach against breast cancer, and its benefits can be potentially furthered by combining the li-Key hybrid vaccine with targeted drugs and adjuvants selected to enhance cross-presentation for exogenous vaccine antigens. Graphical abstract was created with Biorender.com (license number: HA24UHRBV4 and FP24UHRGDD).

Ultrasound Responsive Nanovaccine Armed with Engineered Cancer Cell Membrane and RNA to Prevent Foreseeable Metastasis

Cancer vaccine has been considered as a promising immunotherapy by inducing specific anti-tumor immune response. Rational vaccination at suitable time to efficiently present tumor associated antigen will boost tumor immunity and is badly needed. Here, a poly (lactic-co-glycolic acid) (PLGA)-based cancer vaccine of nanoscale is designed, in which engineered tumor cell membrane proteins, mRNAs, and sonosensitizer chlorin e6 (Ce6) are encapsulated at high efficiency. The nanosized vaccine can be efficiently delivered into antigen presentation cells (APCs) in lymph nodes after subcutaneous injection. In the APCs, the encapsulated cell membrane and RNA from engineered cells, which have disturbed splicing resembling the metastatic cells, provide neoantigens of metastatic cancer in advance. Moreover, the sonosensitizer Ce6 together with ultrasound irradiation promotes mRNA escape from endosome, and augments antigen presentation. Through 4T1 syngeneic mouse model, it has been proved that the proposed nanovaccine is efficient to elicit antitumor immunity and thus prevent cancer metastasis.

Adjuvant Effect of Whole-Cell Pertussis Component on Tetanus Toxoid Potency in Murine Model

There is currently an increasing interest in the development of new-generation purified antigen-based vaccines with a higher safety profile compared to conventional inactivated vaccines. The main problem of subunit vaccines is their lower immunogenicity compared to whole-cell vaccines and inducing weaker and shorter-lasting immune responses. In this paper, the results of the assay of the potency of the tetanus component combined with the diphtheria component and whole-cell pertussis vaccine (DTwP), diphtheria and tetanus vaccine (DT), and in monovalent tetanus vaccine (T) are presented. In the mice model, an adjuvant impact of the whole-cell pertussis component on the immune response against tetanus was observed. It was noticed that the potency of tetanus component in the DTwP vaccine was significantly higher than tetanus potency in DT and T vaccines, despite the same bounding ability unit of the tetanus toxoid in the vaccine formulations. The levels of induction of tetanus antibodies by the tested vaccines were also examined. There were no differences in the induction of humoral responses against tetanus by tested vaccines. This publication discusses the possible mechanisms of impact of the whole-cell pertussis component on the other vaccine antigens and the positive and negative aspects of using the whole-cell pertussis component as an adjuvant.

Bioengineered Bovine Papillomavirus L1 Protein Virus-like Particle (VLP) Vaccines for Enhanced Induction of CD8 T Cell Responses through Cross-Priming

Safe and effective T cell vaccines are needed for the treatment or prevention of cancers as well as infectious agents where vaccines for neutralizing antibodies have performed poorly. Recent research highlights an important role for tissue-resident memory T cells (T_RM cells) in protective immunity and the role of a subset of dendritic cells that are capable of cross-priming for the induction of T_RM cells. However, efficient vaccine technologies that operate through cross-priming and induce robust CD8+ T cell responses are lacking. We developed a platform technology by genetically engineering the bovine papillomavirus L1 major capsid protein to insert a polyglutamic acid/cysteine motif in place of wild-type amino acids in the HI loop. Virus-like particles (VLPs) are formed by self-assembly in insect cells infected with a recombinant baculovirus. Polyarginine/cysteine-tagged antigens are linked to the VLP by a reversible disulfide bond. The VLP possesses self-adjuvanting properties due to the immunostimulatory activity of papillomavirus VLPs. Polyionic VLP vaccines induce robust CD8+ T cell responses in peripheral blood and tumor tissues. A prostate cancer polyionic VLP vaccine was more efficacious than other vaccines and immunotherapies for the treatment of prostate cancer in a physiologically relevant murine model and successfully treated more advanced diseases than the less efficacious technologies. The immunogenicity of polyionic VLP vaccines is dependent on particle size, reversible linkage of the antigen to the VLP, and an interferon type 1 and Toll-like receptor (TLR)3/7-dependent mechanism.

Two Modes of Th1 Polarization Induced by Dendritic-Cell-Priming Adjuvant in Vaccination

Viral infections are usually accompanied by systemic cytokinemia. Vaccines need not necessarily mimic infection by inducing cytokinemia, but must induce antiviral-acquired immunity. Virus-derived nucleic acids are potential immune-enhancers and particularly good candidates as adjuvants in vaccines in mouse models. The most important nucleic-acid-sensing process involves the dendritic cell (DC) Toll-like receptor (TLR), which participates in the pattern recognition of foreign DNA/RNA structures. Human CD141+ DCs preferentially express TLR3 in endosomes and recognize double-stranded RNA. Antigen cross-presentation occurs preferentially in this subset of DCs (cDCs) via the TLR3-TICAM-1-IRF3 axis. Another subset, plasmacytoid DCs (pDCs), specifically expresses TLR7/9 in endosomes. They then recruit the MyD88 adaptor, and potently induce type I interferon (IFN-I) and proinflammatory cytokines to eliminate the virus. Notably, this inflammation leads to the secondary activation of antigen-presenting cDCs. Hence, the activation of cDCs via nucleic acids involves two modes: (i) with bystander effect of inflammation and (ii) without inflammation. In either case, the acquired immune response finally occurs with Th1 polarity. The level of inflammation and adverse events depend on the TLR repertoire and the mode of response to their agonists in the relevant DC subsets, and could be predicted by assessing the levels of cytokines/chemokines and T cell proliferation in vaccinated subjects. The main differences in the mode of vaccine sought in infectious diseases and cancer are defined by whether it is prophylactic or therapeutic, whether it can deliver sufficient antigens to cDCs, and how it behaves in the microenvironment of the lesion. Adjuvant can be selected on a case-to-case basis.

Immunisation with Transgenic L. tarentolae Expressing Gamma Glutamyl Cysteine Synthetase from Pathogenic Leishmania Species Protected against L. major and L. donovani Infection in a Murine Model

Leishmaniasis is a protozoan disease responsible for significant morbidity and mortality. There is no recommended vaccine to protect against infection. In this study, transgenic Leishmania tarentolae expressing gamma glutamyl cysteine synthetase (γGCS) from three pathogenic species were produced and their ability to protect against infection determined using models of cutaneous and visceral leishmaniasis. The ability of IL-2-producing PODS® to act as an adjuvant was also determined in L. donovani studies. Two doses of the live vaccine caused a significant reduction in L. major (p < 0.001) and L. donovani (p < 0.05) parasite burdens compared to their respective controls. In contrast, immunisation with wild type L. tarentolae, using the same immunisation protocol, had no effect on parasite burdens compared to infection controls. Joint treatment with IL-2-producing PODS® enhanced the protective effect of the live vaccine in L. donovani studies. Protection was associated with a Th1 response in L. major and a mixed Th1/Th2 response in L. donovani, based on specific IgG1 and IgG2a antibody and cytokine production from in vitro proliferation assays using antigen-stimulated splenocytes. The results of this study provide further proof that γGCS should be considered a candidate vaccine for leishmaniasis.

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.

TAP-ing into the cross-presentation secrets of dendritic cells

Viral blockade of the transporter associated with antigen processing (TAP) diminishes surface and endosomal recycling compartment levels of major histocompatibility complex class-I (MHC-I) in dendritic cells (DCs), and compromises both classical MHC-I presentation and canonical cross-presentation during infection to impair CD8 T-cell immunity. Virus-specific CD8 T cells are thought to be cross-primed mostly by uninfected TAP-sufficient DCs through cross-presentation of viral peptides from internalized virus-infected dying cells. The dilemma is that CD8 T cells primed to TAP-dependent viral peptides are mismatched to the TAP-independent epitopes presented on tissues infected with immune-evasive viruses. Noncanonical cross-presentation in DCs overcomes cell-intrinsic TAP blockade to nevertheless prime protective TAP-independent CD8 T cells best-matched against the infection. Exploitation of noncanonical cross-presentation may prevent chronic infections with immune-evasive viruses. It may also control immune-evasive cancers that have downmodulated TAP expression.