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

Characterizing TLR4 agonist EmT4™ as an anti-Mycobacterium tuberculosis vaccine adjuvant

Tuberculosis (TB) is again the deadliest infectious disease globally, and more efficacious vaccines are needed to reduce this mortality. Successful subunit TB vaccines need antigens and adjuvants that are immunogenic, inexpensive, and accessible. Here we evaluated the potential of synthetically produced Monophosphoryl lipid A (SyMLP), a TLR4-agonist, formulated in an oil-in-water emulsion (EmT4™) in combination with selected fusion proteins, to drive an effective vaccine-mediated immunogenic response in C57BL/6 mice against Mycobacterium tuberculosis (M.tb) HN878 and H37Rv challenge. We first observed that EmT4™ enhances activation of C57BL/6 bone-marrow derived macrophages and dendritic cells measured by CD40, CD86, and MHCII expression by flow cytometry. EmT4™ did not induce safety signals in a scaled tolerability study. In immunogenicity studies, mice immunized 3 times 3 weeks apart with ID93 antigen + EmT4™ produced a significantly higher magnitude of circulating proinflammatory cytokines and ID93-specific immunoglobulin G (IgG) antibodies pre- and post-challenge with M.tb than saline control animals. Ex vivo ID93 restimulated splenocytes and lung cells elicited significant polyfunctional CD4+ T-helper 1 responses. Importantly, ID93 + EmT4™ immunizations significantly reduced bacterial burden in C57BL/6 mice 4 weeks post-challenge. Interestingly, EmT4™ paired with a next generation protein fusion ID91 also afforded prophylactic protection against M.tb HN878 challenge in both young (6 to 8 wk) and aged (20 mo) immunocompromised Beige mice. These protection and immunogenicity findings suggest that synthetically derived EmT4™ adjuvant is not only suitable to help backfill the preclinical TB vaccine candidate pipeline but is also suitable for the needs of the global community.

ARNAX is an ideal adjuvant for COVID-19 vaccines to enhance antigen-specific CD4+ and CD8+ T-cell responses and neutralizing antibody induction

ARNAX is a synthetic nucleotide-based Toll-like receptor 3 (TLR3) ligand that specifically stimulates the TLR3/TIR domain-containing adaptor molecule 1 (TICAM-1) pathway without activating inflammatory responses. ARNAX activates cellular immunity via cross-presentation; hence, its practical application has been demonstrated in cancer immunotherapy. Given the importance of cellular immunity in virus infections, ARNAX is expected to be a more effective vaccine adjuvant for virus infections than alum, an adjuvant approved for human use that mainly enhances humoral immunity. In the present study, the trimeric recombinant spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was prepared as a vaccine antigen and formulated with ARNAX. When T-cell and neutralizing antibody responses were evaluated in immunized mice, antigen formulated with ARNAX generated significantly larger numbers of antigenspecific CD4+ and CD8+ T cells, as well as higher titers of neutralizing antibodies, compared to antigen alone or antigen formulated with alum. In experiments where immunized mice were challenged with a SARS-CoV-2 mouse-adapted virus derived from the ancestral strain, immunization with antigen formulated with ARNAX reduced virus titers in the lungs at 3 days post-infection to a much greater extent than did immunization with either antigen alone or that formulated with alum. These results show that ARNAX potently enhances the levels of both cellular and humoral immunity above those seen with alum, providing significantly greater viral clearing responses. Thus, ARNAX may act as a useful adjuvant for prophylactic vaccines, particularly for viral infectious diseases.

IMPORTANCE

Cellular immunity is a critical immunological defense system against virus infections. However, aluminum salts, the most widely used adjuvant for vaccines for human use, do not promote strong cellular immunity. To prepare for the next pandemic of viral origin, the development of Th1-type adjuvants with low adverse reactions that induce cellular immunity is necessary. ARNAX is a TLR3 agonist consisting of DNA-RNA hybrid nucleic acid, which is expected to be an adjuvant that induces cellular immunity. The present study using a coronavirus disease 2019 mouse model demonstrated that ARNAX potently induces cellular immunity in addition to humoral immunity with minimal induction of inflammatory cytokines. Therefore, ARNAX has the potential to be used as a potent and welltolerated adjuvant for vaccines against pandemic viruses emerging in the future.

The Yin and Yang of TLR4 in COVID-19

Various pattern recognition receptors (PRRs), including toll-like receptors (TLRs), play a crucial role in recognizing invading pathogens as well as damage-associated molecular patterns (DAMPs) released in response to infection. The resulting signaling cascades initiate appropriate immune responses to eliminate these pathogens. Current evidence suggests that SARS-CoV-2-driven activation of TLR4, whether through direct recognition of the spike glycoprotein (alone or in combination with endotoxin) or by sensing various TLR4-activating DAMPs or alarmins released during viral infection, acts as a critical mediator of antiviral immunity. However, TLR4 exerts a dual role in COVID-19, demonstrating both beneficial and deleterious effects. Dysregulated TLR4 signaling is implicated in the proinflammatory consequences linked to the immunopathogenesis of COVID-19. Additionally, TLR4 polymorphisms contribute to severity of the disease. Given its significant immunoregulatory impact on COVID-19 immunopathology and host immunity, TLR4 has emerged as a key target for developing inhibitors and immunotherapeutic strategies to mitigate the adverse effects associated with SARS-CoV-2 and related infections. Furthermore, TLR4 agonists are also being explored as adjuvants to enhance immune responses to SARS-CoV-2 vaccines.

Exploring Lymph Node Stroma Ageing: Immune Implications and Future Directions

Ageing is an inevitable biological process that impacts the immune system, leading to immunosenescence and inflammaging, which contribute to increased susceptibility to infections, autoimmune diseases and cancers in individuals over the age of 65. This review focuses on the ageing of lymph node stromal cells (LNSCs), which are crucial for maintaining lymph node (LN) structure and function. Age-related changes in LNs, such as fibrosis and lipomatosis, disrupt the LN architecture and reduce immune cell recruitment and function, impairing immune responses to infections and vaccinations. The review discusses the structural and functional decline of various LNSC subsets, including fibroblastic reticular cells (FRCs), lymphatic endothelial cells (LECs) and blood endothelial cells (BECs), highlighting their roles in immune cell activation and homeostasis. Potential strategies to restore aged LNSC function, such as enhancing LNSC activation during vaccination and using senotherapeutics, are explored. Outstanding questions regarding the mechanisms of LNSC ageing and how ageing of the LN stroma might impact autoimmune disorders are also addressed. This review aims to stimulate further research into the characterisation of aged LNSCs and the development of therapeutic interventions to improve immune function in the older adults.

A VZV-gE subunit vaccine decorated with mPLA elicits protective cellular immmune responses against varicella-zoster virus

Herpes zoster is an acute infectious skin disease caused by the reactivation of latent varicella-zoster virus, vaccination, such as subunit vaccine with good safety, can effectively prevent shingles through increasing immunity of the body. However, protein antigens are prone to degradation and inactivation, which alone is generally not sufficient to induce potent immune effect. In this study, the liposomal vaccine platform modified with mPLA (TLR4 agonist) was developed to improve the immunogenicity of glycoprotein E (VZV-gE) derived from herpes zoster virus. The thin-film dispersion and freeze-drying methods were employed to encapsulate VZV-gE against degradation, enhance liposomal stability, and achieve better redissolution effects with an optimized cryoprotectant. The in vitro results presented that mPLA could effectively enhance the uptake of VZV-gE with DC2.4. In vivo immune effect evaluation showed that the prepared subunit vaccines could induce stronger IgG, IgG1, and IgG2a antibody levels in the mouse serum, improving humoral immune effects. And the secretion levels of Th1 cytokines (IFN-γ, IL-2) and Th2 cytokines (IL-4, IL-10) in the splenocytes were significantly increased, inducing protective cellular immune responses. Overall, this work presented that combining immunomodulatory adjuvants decorated nanocarriers to develop subunit vaccine platforms was a promising strategy to prevent the occurrence of herpes zoster effectively.

Two recombinant cytomegalovirus antigens formulated with the SPA14 adjuvant system: Impact of temperature, pH and excipients on the stability of each antigen and adjuvant component

By evaluating the stability profiles of each component of a vaccine candidate (antigens, adjuvants), formulation conditions to mitigate vaccine instability can be identified. In this work, two recombinant Cytomegalovirus (CMV) glycoprotein antigens (gB, Pentamer) were formulated with SPA14, a novel liposome-based adjuvant system containing a synthetic TLR4 agonist (E6020) and a saponin (QS21). Analytical characterization and accelerated stability studies were performed with the two CMV antigens, formulated with and without SPA14, under various conditions (temperature, pH, excipients). For the antigens, the Pentamer was less stable than gB, and the addition of SPA14 adjuvant had negligible impact. For the SPA14 components, minor pH shifts (caused by the buffer's temperature dependent pKa shifts) destabilized the liposome (particle size by DLS) and QS21, but E6020 was unaffected (integrity by RP-UHPLC and LC-MS, respectively). The addition of chelators and free radical scavengers stabilized both the QS21 and E6020 components, consistent with oxidative degradation catalyzed by trace metal-ions. Interestingly, QS21 and E6020 also displayed improved storage stability in the presence of the protein antigens. These results are discussed in terms of developing key stability-indicating assays to optimize formulation conditions to stabilize the two CMV antigens and the three components of the SPA14 adjuvant system.

Combination adjuvant improves influenza virus immunity by downregulation of immune homeostasis genes in lymphocytes

Adjuvants play a central role in enhancing the immunogenicity of otherwise poorly immunogenic vaccine antigens. Combining adjuvants has the potential to enhance vaccine immunogenicity compared with single adjuvants, although the cellular and molecular mechanisms of combination adjuvants are not well understood. Using the influenza virus hemagglutinin H5 antigen, we define the immunological landscape of combining CpG and MPLA (TLR-9 and TLR-4 agonists, respectively) with a squalene nanoemulsion (AddaVax) using immunologic and transcriptomic profiling. Mice immunized and boosted with recombinant H5 in AddaVax, CpG+MPLA, or AddaVax plus CpG+MPLA (IVAX-1) produced comparable levels of neutralizing antibodies and were equally well protected against the H5N1 challenge. However, after challenge with H5N1 virus, H5/IVAX-1-immunized mice had 100- to 300-fold lower virus lung titers than mice receiving H5 in AddaVax or CpG+MPLA separately. Consistent with enhanced viral clearance, unsupervised expression analysis of draining lymph node cells revealed the combination adjuvant IVAX-1 significantly downregulated immune homeostasis genes, and induced higher numbers of antibody-producing plasmablasts than either AddaVax or CpG+MPLA. IVAX-1 was also more effective after single-dose administration than either AddaVax or CpG+MPLA. These data reveal a novel molecular framework for understanding the mechanisms of combination adjuvants, such as IVAX-1, and highlight their potential for the development of more effective vaccines against respiratory viruses.

Modulating Neuroinflammation as a Prospective Therapeutic Target in Alzheimer's Disease

The recent approval of lecanemab highlights that the amyloid beta (Aβ) protein is an important pathological target in Alzheimer's disease (AD) and further emphasizes the significance of neuroinflammatory pathways in regulating Aβ accumulation. Indeed, Aβ accumulation triggers microglia activation, which are key mediators in neuroinflammation. The inflammatory responses in this process can lead to neuronal damage and functional decline. Microglia secrete proinflammatory cytokines that accelerate neuronal death and release anti-inflammatory cytokines and growth factors contributing to neuronal recovery and protection. Thus, microglia play a dual role in neurodegeneration and neuroprotection, complicating their function in AD. Therefore, elucidating the complex interactions between Aβ protein, microglia, and neuroinflammation is essential for developing new strategies for treating AD. This review investigates the receptors and pathways involved in activating microglia and aims to enhance understanding of how these processes impact neuroinflammation in AD, as well as how they can be regulated. This review also analyzed studies reported in the existing literature and ongoing clinical trials. Overall, these studies will contribute to understanding the regulatory mechanisms of neuroinflammation and developing new therapies that can slow the pathological progression of AD.

A central role of stimulator of interferon genes' adaptor protein in defensive immune response

Cytotoxic DNAs, methylation, histones and histones binding proteins are speculated to induce DNA sensors. Under stressed condition, the antigenic patterns, PAMPs and DAMPs, trigger the hyperactive innate response through DNA, DNA-RNA hybrids, oligonucleotides, histones and mtDNA to initiate cGAMP-STING-IFN I cascade. HSV -1&2, HIV, Varicella- Zoster virus, Polyomavirus, Cytomegalovirus, and KSHV negatively regulate the STING-MAVS-TBK-1/1KKE pathway. Implications in STING-PKR-ER regulation often run into causing senescence and organ fibrosis. Post-translational modifications such as, phosphorylation, ubiquitination, SUMOylation, hydrolysis etc. downstream the processing of cGAS-STING that determine the fate of disease prognosis. Self-DNA under normal circumstances is removed through DNase III action; however, its deficiency is the great cause of RA diseases. Regular STING activation in chronic diseases could lead to exacerbate the neurodegenerative disorders due to constant mtDNA leakage. 2' 3' cGAMP or CDN or its associates are being explored as STING agonist therapeutics to treat solid/metastatic tumors to help infiltrate the immune cells, cytokines and chemokines to regulate the protective response. Liposomes, polymer nanoparticles, and cell-derived nanoparticles are also meant to increase the drug efficiency and stability for desired immune response to enhance the IFN I production. This review highlights the implications of cGAMP-STING- IFN I cascade and related pathways involved in the disease prognosis, therapeutics and considering the gaps on different aspects to utilize its greater potential in disease control.

Assessing human B cell responses to influenza virus vaccines and adjuvants in a PBMC-derived in vitro culture system

In vitro systems based on human peripheral blood mononuclear cells (PBMCs) can bridge the gap between preclinical and clinical vaccine evaluation but have so far mainly been exploited to assess vaccine effects on antigen-presenting cells and T cells. Our study aimed to assess whether B cells present in PBMCs also respond to vaccines and reflect the effects of different vaccine formulations and adjuvants. We stimulated PBMCs with whole inactivated virus (WIV) or split virus (SIV) H5N1 influenza vaccine, with or without the addition of the adjuvant cytosine phosphoguanine (CpG) ODN 2395, and collected the cells and supernatants at different timepoints. B cell subsets were measured by flow cytometry, immunoglobulin (IgG) levels by ELISA, B cell-related genes by qPCR, and cytokine levels by intracellular staining. B cells differentiated more readily to plasmablasts and plasma cells and produced more IgG when PBMC cultures were stimulated with WIV than when stimulated with SIV. In line, PRDM1, XBP1, and AICDA, genes associated with the differentiation of B cells to antibody-secreting cells, were expressed at higher levels in WIV- than in SIV-stimulated PBMCs. The combination of WIV and CpG consistently induced the highest levels of antibody-secreting cell differentiation, IgG production, and B-cells secreting IL-6 and IL-10. Taken together, B cells in human PBMC cultures show distinct responses to different types of vaccines and vaccine/CpG combinations. This underlines the suitability of unfractionated PBMCs for evaluating vaccine effects on different types of human immune cells before running costly clinical trials.

Lipoprotein Signal Peptide as Adjuvants: Leveraging Lipobox-Driven TLR2 Activation in Modern Vaccine Design

Toll-like receptor 2 (TLR2) signaling is a pivotal component of immune system activation, and it is closely linked to the lipidation of bacterial proteins. This lipidation is guided by bacterial signal peptides (SPs), which ensure the precise targeting and membrane anchoring of these proteins. The lipidation process is essential for TLR2 recognition and the activation of robust immune responses, positioning lipidated bacterial proteins as potent immunomodulators and adjuvants for vaccines against bacterial-, viral-, and cancer-related antigens. The structural diversity and cleavage pathways of bacterial SPs are critical in determining lipidation efficiency and protein localization, influencing their immunogenic potential. Recent advances in bioinformatics have significantly improved the prediction of SP structures and cleavage sites, facilitating the rational design of recombinant lipoproteins optimized for immune activation. Moreover, the use of SP-containing lipobox motifs, as adjuvants to lipidate heterologous proteins, has expanded the potential of vaccines targeting a broad range of pathogens. However, challenges persist in expressing lipidated proteins, particularly within heterologous systems. These challenges can be addressed by optimizing expression systems, such as engineering E. coli strains for enhanced lipidation. Thus, lipoprotein signal peptides (SPs) demonstrate remarkable versatility as adjuvants in vaccine development, diagnostics, and immune therapeutics, highlighting their essential role in advancing immune-based strategies to combat diverse pathogens.

Epigenetic modulation of immune cells: Mechanisms and implications

Epigenetic modulation of the immune response entails modifiable and inheritable modifications that do not modify the DNA sequence. While there have been many studies on epigenetic changes in tumor cells, there is now a growing focus on epigenetically mediated changes in immune cells of both the innate and adaptive systems. These changes have significant implications for both the body's response to tumors and the development of potential therapeutic vaccines. This study primarily discusses the key epigenetic alterations, with a specific emphasis on pseudouridination, as well as non-coding RNAs and their transportation, which can lead to the development of cancer and the acquisition of new phenotypic traits by immune cells. Furthermore, the advancement of therapeutic vaccinations targeting the tumor will be outlined.

Co-adjuvanting Nod2-stimulating bacteria with a TLR7 agonist elicits potent protective immunity against respiratory virus infection

OBJECTIVES

This study investigates the synergistic effect of combining the TLR7 agonist Imiquimod with either the Nod2 agonist (muramyl dipeptide; MDP) or commensal bacteria as nasal vaccine adjuvants to enhance immunity against respiratory viruses.

METHODS

Mice assessed immune responses, including antibody and cytokine profiles, after intranasal immunization with antigen and adjuvant combinations. BMDCs were cultured with these components to measure cytokine production. Germinal center formation and hapten-specific antibodies were evaluated using OT-II T-cell transfer and hapten-ovalbumin. Commensal bacteria from healthy nasal cavities were screened for Nod2-stimulating activity using a reporter assay. Protective efficacy against viral pathogens was evaluated using an influenza A infection model and a pseudovirus system for SARS-CoV-2 neutralizing antibodies.

RESULTS

Screening identified Imiquimod as a potent enhancer of adaptive immune responses during nasal immunization, showing synergy with MDP. This combination elevated IL-12p40 and IL-6 levels, enhanced antibody production, and promoted T follicular helper cell differentiation. The Imiquimod-MDP combination provided robust protection against influenza and SARS-CoV-2. Screening of commensal bacteria revealed differential Nod2-stimulating capacities, with Staphylococcus aureus exhibiting superior synergy with Imiquimod compared to Staphylococcus epidermidis. Notably, this synergism was abolished in Nod2-deficient mice, and pretreatment with S. aureus significantly enhanced the protective efficacy of Imiquimod against influenza compared to S. epidermidis.

CONCLUSIONS

Combining Imiquimod with MDP or high Nod2-stimulating bacteria offers a promising strategy for nasal vaccine adjuvants. These combinations effectively boost humoral and cellular immune responses, providing strong protection against respiratory viruses.

Advances in protein subunit vaccines against H1N1/09 influenza

The A/H1N1pdm09 influenza virus, which caused the 2009 pandemic, has since become a recurring strain in seasonal influenza outbreaks. Given the ongoing threat of influenza, protein subunit vaccines have garnered significant attention for their safety and effectiveness. This review seeks to highlight the latest developments in protein subunit vaccines that specifically target the A/H1N1pdm09 virus. It will also examine the structure and replication cycle of influenza A viruses and compare different types of influenza vaccines. Additionally, the review will address key aspects of H1N1 protein subunit vaccine development, such as antigen selection, protein expression systems, and the use of adjuvants. The role of animal models in evaluating these vaccines will also be discussed. Despite challenges like antigenic variability and the complexities of vaccine production and distribution, protein subunit vaccines remain a promising option for future influenza prevention efforts.

Synthesis and biological evaluation of lipid A derived from commensal Bacteroides

The inflammation-inducing properties of lipopolysaccharides (LPS) of Gram-negative bacteria reside in their lipid A moiety. Bacillus fragilis, which is a commensal Gram-negative bacterium, biosynthesises lipid A that is structurally distinct from that of E. coli and other enteric bacteria. It is composed of a β1,6-linked glucosamine (GlcN) disaccharide that is only phosphorylated at the anomeric center. The major species of B. fragilis has five fatty acids and the amine of the distal GlcN moiety carries the unusual (R)-3-(13-methyltetradecanoyloxy)-1.5-methylhexadecanoic acid. A recent study indicates that the LPS of B. fragilis has anti-viral activity by selective induction of interferon (IFN)-β and is protective in mouse models of vesicular stomatitis virus (VSV) and influenza A. Heterogeneity in the structures of LPS and lipid A and possible contamination with other inflammatory components make it difficult to unambiguously define the immune-modulatory properties of LPS or lipid A. Therefore, we developed a synthetic approach for the preparation of the unusual major lipid A species derived from B. fragilis, which includes a synthetic approach for (R)-3-(13-methyltetradecanoyloxy)-1.5-methylhexadecanoic acid by the Wittig olefination to install the terminal isopropyl moiety. The proinflammatory and antiviral responses of synthetic B. fragilis lipid A were investigated in several cell lines and primary human monocytes by examining the production of interleukin (IL)-6 and IFN-β. It was found that B. fragilis does not induce the production of IL-6 and IFN-β but can partially antagonize the production of pro-inflammatory cytokines induced by E. coli LPS and lipid A.

Developing a chimeric multiepitope vaccine against Nipah virus (NiV) through immunoinformatics, molecular docking and dynamic simulation approaches

Nipah virus (NiV) is a highly lethal zoonotic pathogen that poses a significant threat to human and animal health. Unfortunately, no effective treatments have been developed for this deadly zoonotic disease. Therefore, we designed a chimeric multiepitope vaccine targeting the Nipah virus (NiV) glycoprotein and fusion protein through immunoinformatic approaches. Therefore, the vaccine was developed by combining promising and potential antigenic MHC-I, MHC-II, and B-cell epitopes obtained from the selected proteins. When combined, the MHC-I and MHC-II epitopes offered 100 % global population coverage. The physicochemical characterization also exhibited favorable properties, including solubility and potential functional stability of the vaccine within the body (GRAVY score of -0.308). Structural analyses unveiled a well-stabilized secondary and tertiary structure with a Ramachandran score of 84.4 % and a Z score of -5.02. Findings from docking experiments with TLR-2 (-1089.3 kJ/mol) and TLR-4 (-1016.7 kJ/mol) showed a strong affinity of the vaccine towards the receptor. Molecular dynamics simulations revealed unique conformational dynamics among the "vaccine-apo," "vaccine-TLR-2," and "vaccine-TLR-4″ complexes. Consequently, the complexes exhibited significant compactness, flexibility, and exposure to solvents. The results of the codon optimization were remarkable, as the vaccine showed a significant amount of expression in the E. coli vector (GC content of 45.36 % and a CAI score of 1.0). The results of immune simulations, however, showed evidence of both adaptive and innate immune responses induced by the vaccine. Therefore, we highly recommend further research on this chimeric multiepitope vaccine to establish its efficacy and safety against the Nipah virus (NiV).

In silico and immunoinformatics based multiepitope subunit vaccine design for protection against visceral leishmaniasis

Visceral leishmaniasis (VL) is a vector-borne neglected tropical protozoan disease with high fatality and no certified vaccine. Conventional vaccine preparation is challenging and tedious. Here in this work, we created a global multiepitope subunit vaccination against VL utilizing innovative immunoinformatics technique based on the extensively conserved epitopic regions of the PrimPol protein of Leishmania donovani consisting of four subunits which were analyzed and studied, out of which DNA primase large subunit and DNA polymerase α subunit B were evaluated as antigens by Vaxijen 2.0. The multiepitope vaccine design includes a single adjuvant β-defensins, eight CTL epitopes, eight HTL epitopes, seven linear BCL epitopes and one discontinuous BCL epitope to induce innate, cellular and humoral immune responses against VL. The Expasy ProtParam tool characterized the physiochemical parameters of the vaccine. At the same time, SOLpro evaluated our vaccine constructs to be soluble upon expression. We also modeled the stable tertiary structure of our vaccine construct through Robetta modeling for molecular docking studies with toll-like receptor proteins through HADDOCK 2.4. Simulations based on molecular dynamics revealed an intact vaccine and TLR8 complex, supporting our vaccine design's immunogenicity. Also, the immune simulation of our vaccine by the C-ImmSim server demonstrated the potency of the multiepitope vaccine construct to induce proper immune response for host defense. Codon optimization and in silico cloning of our vaccine further assured high expression. The outcomes of our study on multiepitope vaccine design significantly produced a potential candidate against VL and can potentially eradicate the disease in the future after clinical investigations.Communicated by Ramaswamy H. Sarma.

Evaluation of the adjuvant effect of imiquimod and CpG ODN 1826 in chimeric DNA vaccine against Japanese encephalitis

Vaccines represent a significant milestone in the history of human medical science and serve as the primary means for controlling infectious diseases. In recent years, the geographical distribution of Japanese encephalitis viruses (JEV) of various genotypes has become increasingly complex, which provides a rationale for the development of safer and more effective vaccines. The advent of subunit and nucleic acid vaccines, especially propelled by advancements in genetic engineering since the 1980s, has accelerated the application of novel adjuvants. These novel vaccine adjuvants have diversified into toll-like receptor (TLR) agonists, complex adjuvants, nanoparticles and so on. However, the efficacy of adjuvant combinations can vary depending on the host system, disease model, or vaccine formulation, sometimes resulting in competitive or counteractive effects. In our previous study, we constructed a pJME-LC3 chimeric DNA vaccine aimed at inducing an immune response through autophagy induction. Building on this, we investigated the impact of the TLR7/8 agonist imiquimod (IMQ) and the TLR9 agonist CpG ODN 1826 as adjuvants on the immunogenicity of the Japanese encephalitis chimeric DNA vaccine. Our findings indicate that the combination of the pJME-LC3 vaccine with IMQ and CpG ODN 1826 adjuvants enhanced the innate immune response, promoting the maturation and activation of antigen-presenting cells in the early immune response. Furthermore, it played a regulatory and optimizing role in subsequent antigen-specific immune responses, resulting in effective cellular and humoral immunity and providing prolonged immune protection. The synergistic effect of IMQ and CpG ODN 1826 as adjuvants offers a novel approach for the development of Japanese encephalitis nucleic acid vaccines.

Immunological Strategies in Gastric Cancer: How Toll-like Receptors 2, -3, -4, and -9 on Monocytes and Dendritic Cells Depend on Patient Factors?

(1) Introduction: Toll-like receptors (TLRs) are key in immune response by recognizing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). In gastric cancer (GC), TLR2, TLR3, TLR4, and TLR9 are crucial for modulating immune response and tumor progression. (2) Objective: This study aimed to assess the percentage of dendritic cells and monocytes expressing TLR2, TLR3, TLR4, and TLR9, along with the concentration of their soluble forms in the serum of GC patients compared to healthy volunteers. Factors such as disease stage, tumor type, age, and gender were also analyzed. (3) Materials and Methods: Blood samples from newly diagnosed GC patients and healthy controls were immunophenotyped using flow cytometry to assess TLR expression on dendritic cell subpopulations and monocytes. Serum-soluble TLRs were measured by ELISA. Statistical analysis considered clinical variables such as tumor type, stage, age, and gender. (4) Results: TLR expression was significantly higher in GC patients, except for TLR3 on classical monocytes. Soluble forms of all TLRs were elevated in GC patients, with significant differences based on disease stage but not tumor type, except for serum TLR2, TLR4, and TLR9. (5) Conclusions: Elevated TLR expression and soluble TLR levels in GC patients suggest a role in tumor pathogenesis and progression, offering potential biomarkers and therapeutic targets.

FcRider: a recombinant Fc nanoparticle with endogenous adjuvant activities for hybrid immunization

Active immunization (vaccination) induces long-lasting immunity with memory, which takes weeks to months to develop. Passive immunization (transfer of neutralizing antibodies) provides immediate protection, yet with high cost and effects being comparatively short-lived. No currently approved adjuvants are compatible with formulations to combine active and passive immunizations, not to mention their huge disparities in administration routes and dosage. To solve this, we engineered the Fc fragment of human IgG1 into a hexamer nanoparticle and expressed its afucosylated form in Fut8-/- CHO cells, naming it "FcRider." FcRider is highly soluble with long-term stability, easily produced at high levels equivalent to those of therapeutic antibodies, and is amenable to conventional antibody purification schemes. Most importantly, FcRider possesses endogenous adjuvant activities. Using SWHEL B cell receptor (BCR) transgenic mice, we found that HEL-FcRider induced GL7+ germinal center B cells and HEL-specific IgG. Similarly, immunizing mice with UFO-BG-FcRider, a fusion containing the stabilized human immunodeficiency virus-1 (HIV-1) Env protein as immunogen, promoted somatic hypermutation and generation of long CDR3 of the IgG heavy chains. Intramuscular injection of (Fba + Met6)3-FcRider, a fusion with two peptide epitopes from Candida albicans cell surface, stimulated strong antigen-specific IgG titers. In three different models, we showed that afucosylated FcRider functions as a multivalent immunogen displayer and stimulates antigen-specific B cells without any exogenous adjuvant. As an antibody derivative, afucosylated FcRider could be a novel platform combining vaccines and therapeutic antibodies, integrating active and passive immunizations into single-modality "hybrid immunization" to provide complete and long-lasting protection against infections, and may open new avenues in cancer immunotherapy as well.

Safety and efficacy of toll-like receptor agonists as therapeutic agents and vaccine adjuvants for infectious diseases in animals: a systematic review

Introduction

Strengthening global health security relies on adequate protection against infectious diseases through vaccination and treatment. Toll-like receptor (TLR) agonists exhibit properties that can enhance immune responses, making them potential therapeutic agents or vaccine adjuvants.

Methods

We conducted an extensive systematic review to assess the efficacy of TLR agonists as therapeutic agents or vaccine adjuvants for infectious diseases and their safety profile in animals, excluding rodents and cold-blooded animals. We collected qualitative and available quantitative data on the efficacy and safety outcomes of TLR agonists and employed descriptive analysis to summarize the outcomes.

Results

Among 653 screened studies, 51 met the inclusion criteria. In this review, 82% (42/51) of the studies used TLR agonists as adjuvants, while 18% (9/51) applied TLR agonist as therapeutic agents. The predominant TLR agonists utilized in animals against infectious diseases was CpG ODN, acting as a TLR9 agonist in mammals, and TLR21 agonists in chickens. In 90% (46/51) of the studies, TLR agonists were found effective in stimulating specific and robust humoral and cellular immune responses, thereby enhancing the efficacy of vaccines or therapeutics against infectious diseases in animals. Safety outcomes were assessed in 8% (4/51) of the studies, with one reporting adverse effects.

Discussion

Although TLR agonists are efficacious in enhancing immune responses and the protective efficacy of vaccines or therapeutic agents against infectious diseases in animals, a thorough evaluation of their safety is imperative to in-form future clinical applications in animal studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=323122.

Structure-Activity Relationship Studies in Benzothiadiazoles as Novel Vaccine Adjuvants

Extracellular vesicles (EVs) can transfer antigens and immunomodulatory molecules, and such EVs released by antigen-presenting cells equipped with immunostimulatory functions have been utilized for vaccine formulations. A prior high-throughput screening campaign led to the identification of compound 634 (1), which enhanced EV release and increased intracellular Ca2+ influx. Here, we performed systematic structure-activity relationship (SAR) studies to investigate the scaffold for its potency as a vaccine adjuvant. Synthesized compounds were analyzed in vitro for CD63 reporter activity (a marker for EV biogenesis) in human THP-1 cells, induction of Ca2+ influx, IL-12 production, and cell viability in murine bone-marrow-derived dendritic cells. The SAR studies indicated that the ester functional group was requisite, and the sulfur atom of the benzothiadiazole ring replaced with a higher selenium atom (9f) or a bioisosteric ethenyl group (9h) retained potency. Proof-of-concept vaccination studies validated the potency of the selected compounds as novel vaccine adjuvants.

Orchestrated Codelivery of Peptide Antigen and Adjuvant to Antigen-Presenting Cells by Using an Engineered Chimeric Peptide Enhances Antitumor T-Cell Immunity

The intrinsic pharmacokinetic limitations of traditional peptide-based cancer vaccines hamper effective cross-presentation and codelivery of antigens (Ag) and adjuvants, which are crucial for inducing robust antitumor CD8+ T-cell responses. In this study, we report the development of a versatile strategy that simultaneously addresses the different pharmacokinetic challenges of soluble subunit vaccines composed of Ags and cytosine-guanosine oligodeoxynucleotide (CpG) to modulate vaccine efficacy via translating an engineered chimeric peptide, eTAT, as an intramolecular adjuvant. Linking Ags to eTAT enhanced cytosolic delivery of the Ags. This, in turn, led to improved activation and lymph node-trafficking of Ag-presenting cells and Ag cross-presentation, thus promoting Ag-specific T-cell immune responses. Simple mixing of eTAT-linked Ags and CpG significantly enhanced codelivery of Ags and CpG to the Ag-presenting cells, and this substantially augmented the adjuvant effect of CpG, maximized vaccine immunogenicity, and elicited robust and durable CD8+ T-cell responses. Vaccination with this formulation altered the tumor microenvironment and exhibited potent antitumor effects, with generally further enhanced therapeutic efficacy when used in combination with anti-PD1. Altogether, the engineered chimeric peptide-based orchestrated codelivery of Ag and adjuvant may serve as a promising but simple strategy to improve the efficacy of peptide-based cancer vaccines.

Display of FliC131 on the Surface of Lactococcus lactis as a Strategy to Increase its Adjuvanticity for Mucosal Immunization

Research on innovative mucosal adjuvants is essential to develop new vaccines for safe mucosal application. In this work, we propose the development of a Lactococcus lactis that expresses a variant of flagellin on its surface (FliC131*), to increase the adjuvanticity of the living cell and cell wall-derived particles (CWDP). We optimized the expression of FliC131*, and confirmed its identity and localization by Western blot and flow cytometry. We also generated CWDP containing FliC131* (CDWP-FliC131*) and evaluated their storage stability. Lastly, we measured the human TLR5 stimulating activity in vitro and assessed the adjuvanticity in vivo using ovalbumin (OVA) as a model antigen. As a result, we generated L. lactis/pCWA-FliC131*, that expresses and displays FliC131* on its surface, obtained the corresponding CWDP-FliC131*, and showed that both activated hTLR5 in vitro in a dose-dependent manner. Furthermore, CWDP-FliC131* retained this biological activity after being lyophilized and stored for a year. Finally, intranasal immunization of mice with OVA plus live L. lactis/pCWA-FliC131* or CWDP-FliC131* induced OVA-specific IgG and IgA in serum, intestinal lavages, and bronchoalveolar lavages. Our work demonstrates the potential of this recombinant L. lactis with an enhanced adjuvant effect, prompting its further evaluation for the design of novel mucosal vaccines.

Immune profiling of age and adjuvant-specific activation of human blood mononuclear cells in vitro

Vaccination reduces morbidity and mortality due to infections, but efficacy may be limited due to distinct immunogenicity at the extremes of age. This raises the possibility of employing adjuvants to enhance immunogenicity and protection. Early IFNγ production is a hallmark of effective vaccine immunogenicity in adults serving as a biomarker that may predict effective adjuvanticity. We utilized mass cytometry (CyTOF) to dissect the source of adjuvant-induced cytokine production in human blood mononuclear cells (BMCs) from newborns (~39-week-gestation), adults (~18-63 years old) and elders (>65 years of age) after stimulation with pattern recognition receptors agonist (PRRa) adjuvants. Dimensionality reduction analysis of CyTOF data mapped the BMC compartment, elucidated age-specific immune responses and profiled PRR-mediated activation of monocytes and DCs upon adjuvant stimulation. Furthermore, we demonstrated PRRa adjuvants mediated innate IFNγ induction and mapped NK cells as the key source of TLR7/8 agonist (TLR7/8a) specific innate IFNγ responses. Hierarchical clustering analysis revealed age and TLR7/8a-specific accumulation of innate IFNγ producing γδ T cells. Our study demonstrates the application of mass cytometry and cutting-edge computational approaches to characterize immune responses across immunologically distinct age groups and may inform identification of the bespoke adjuvantation systems tailored to enhance immunity in distinct vulnerable populations.

In vivo quantitative characterization of nano adjuvant transport in the tracheal layer by photoacoustic imaging

Adjuvants are indispensable ingredients in vaccine formulations. Evaluating the in vivo transport processes of adjuvants, particularly for inhalation formulations, presents substantial challenges. In this study, a nanosized adjuvant aluminum hydroxide (AlOOH) was synthesized and labeled with indocyanine green (ICG) and bovine serum albumin (BSA) to achieve strong optical absorption ability and high biocompatibility. The adjuvant nanomaterials (BSA@ICG@AlOOH, BIA) were delivered as an aerosol into the airways of mice, its distribution was monitored using photoacoustic imaging (PAI) in vivo. PAI results illustrated the gradual cross-layer transmission process of BIA in the tracheal layer, traversing approximately 250 µm from the inner layer of the trachea to the outer layer. The results were consistent with pathology. While the intensity of the BIA reduced by approximately 46.8% throughout the transport process. The ability of PAI for quantitatively characterized the dynamic transport process of adjuvant within the tracheal layer may be widely used in new vaccine development.

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

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

Unraveling the Complexities of Toll-like Receptors: From Molecular Mechanisms to Clinical Applications

Toll-like receptors (TLRs) are vital components of the innate immune system, serving as the first line of defense against pathogens by recognizing a wide array of molecular patterns. This review summarizes the critical roles of TLRs in immune surveillance and disease pathogenesis, focusing on their structure, signaling pathways, and implications in various disorders. We discuss the molecular intricacies of TLRs, including their ligand specificity, signaling cascades, and the functional consequences of their activation. The involvement of TLRs in infectious diseases, autoimmunity, chronic inflammation, and cancer is explored, highlighting their potential as therapeutic targets. We also examine recent advancements in TLR research, such as the development of specific agonists and antagonists, and their application in immunotherapy and vaccine development. Furthermore, we address the challenges and controversies surrounding TLR research and outline future directions, including the integration of computational modeling and personalized medicine approaches. In conclusion, TLRs represent a promising frontier in medical research, with the potential to significantly impact the development of novel therapeutic strategies for a wide range of diseases.

Vaccine adjuvants: current status, research and development, licensing, and future opportunities

Vaccines represent one of the most significant inventions in human history and have revolutionized global health. Generally, a vaccine functions by triggering the innate immune response and stimulating antigen-presenting cells, leading to a defensive adaptive immune response against a specific pathogen's antigen. As a key element, adjuvants are chemical materials often employed as additives to increase a vaccine's efficacy and immunogenicity. For over 90 years, adjuvants have been essential components in many human vaccines, improving their efficacy by enhancing, modulating, and prolonging the immune response. Here, we provide a timely and comprehensive review of the historical development and the current status of adjuvants, covering their classification, mechanisms of action, and roles in different vaccines. Additionally, we perform systematic analysis of the current licensing processes and highlights notable examples from clinical trials involving vaccine adjuvants. Looking ahead, we anticipate future trends in the field, including the development of new adjuvant formulations, the creation of innovative adjuvants, and their integration into the broader scope of systems vaccinology and vaccine delivery. The article posits that a deeper understanding of biochemistry, materials science, and vaccine immunology is crucial for advancing vaccine technology. Such advancements are expected to lead to the future development of more effective vaccines, capable of combating emerging infectious diseases and enhancing public health.

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.

Enhancing Control of Leishmania infantum Infection: A Multi-Epitope Nanovaccine for Durable T-Cell Immunity

Canine leishmaniosis (CanL) is a growing health problem for which vaccination is a crucial tool for the control of disease. The successful development of an effective vaccine against this disease relies on eliciting a robust and enduring T-cell immune response involving the activation of CD4+ Th1 and CD8+ T-cells. This study aimed to evaluate the immunogenicity and prophylactic efficacy of a novel nanovaccine comprising a multi-epitope peptide, known as HisDTC, encapsulated in PLGA nanoparticles against Leishmania infantum infection in the murine model. The encapsulation strategy was designed to enhance antigen loading and sustain release, ensuring prolonged exposure to the immune system. Our results showed that mice immunized with PLGA-encapsulated HisDTC exhibited a significant reduction in the parasite load in the liver and spleen over both short and long-term duration. This reduction was associated with a cellular immune profile marked by elevated levels of pro-inflammatory cytokines, such as IFN-γ, and the generation of memory T cells. In conclusion, the current study establishes that PLGA-encapsulated HisDTC can promote effective and long-lasting T-cell responses against L. infantum in the murine model. These findings underscore the potential utility of multi-epitope vaccines, in conjunction with appropriate delivery systems, as an alternative strategy for CanL control.

Vaccine Strategies to Elicit Mucosal Immunity

Vaccines are essential tools to prevent infection and control transmission of infectious diseases that threaten public health. Most infectious agents enter their hosts across mucosal surfaces, which make up key first lines of host defense against pathogens. Mucosal immune responses play critical roles in host immune defense to provide durable and better recall responses. Substantial attention has been focused on developing effective mucosal vaccines to elicit robust localized and systemic immune responses by administration via mucosal routes. Mucosal vaccines that elicit effective immune responses yield protection superior to parenterally delivered vaccines. Beyond their valuable immunogenicity, mucosal vaccines can be less expensive and easier to administer without a need for injection materials and more highly trained personnel. However, developing effective mucosal vaccines faces many challenges, and much effort has been directed at their development. In this article, we review the history of mucosal vaccine development and present an overview of mucosal compartment biology and the roles that mucosal immunity plays in defending against infection, knowledge that has helped inform mucosal vaccine development. We explore new progress in mucosal vaccine design and optimization and novel approaches created to improve the efficacy and safety of mucosal vaccines.

Innovative translational platforms for rapid developing clinical vaccines against COVID-19 and other infectious disease

A vaccine is a biological preparation that contains the antigen capable of stimulating the immune system to form the defense against pathogens. Vaccine development often confronts big challenges, including time/energy-consuming, low efficacy, lag to pathogen emergence and mutation, and even safety concern. However, these seem now mostly conquerable through constructing the advanced translational platforms that can make innovative vaccines, sometimes, potentiated with a distinct multifunctional VADS (vaccine adjuvant delivery system), as evidenced by the development of various vaccines against the covid-19 pandemic at warp speed. Particularly, several covid-19 vaccines, such as the viral-vectored vaccines, mRNA vaccines and DNA vaccines, regarded as the innovative ones that are rapidly made via the high technology-based translational platforms. These products have manifested powerful efficacy while showing no unacceptable safety profile in clinics, allowing them to be approved for massive vaccination at also warp speed. Now, the proprietary translational platforms integrated with the state-of-the-art biotechnologies, and even the artificial intelligence (AI), represent an efficient mode for rapid making innovative clinical vaccines against infections, thus increasingly attracting interests of vaccine research and development. Herein, the advanced translational platforms for making innovative vaccines, together with their design principles and immunostimulatory efficacies, are comprehensively elaborated.

A novel CpG ODN compound adjuvant enhances immune response to spike subunit vaccines of porcine epidemic diarrhea virus

CpG oligodeoxynucleotides (CpG ODNs) boost the humoral and cellular immune responses to antigens through interaction with Toll-like receptor 9 (TLR9). These CpG ODNs have been extensively utilized in human vaccines. In our study, we evaluated five B-type CpG ODNs that have stimulatory effects on pigs by measuring the proliferation of porcine peripheral blood mononuclear cells (PBMCs) and assessing interferon gamma (IFN-γ) secretion. Furthermore, this study examined the immunoenhancing effects of the MF59 and CpG ODNs compound adjuvant in mouse and piglet models of porcine epidemic diarrhea virus (PEDV) subunit vaccine administration. The in vitro screening revealed that the CpG ODN named CpG5 significantly stimulated the proliferation of porcine PBMCs and elevated IFN-γ secretion levels. In the mouse vaccination model, CpG5 compound adjuvant significantly bolstered the humoral and cellular immune responses to the PEDV subunit vaccines, leading to Th1 immune responses characterized by increased IFN-γ and IgG2a levels. In piglets, the neutralizing antibody titer was significantly enhanced with CpG5 compound adjuvant, alongside a considerable increase in CD8+ T lymphocytes proportion. The combination of MF59 adjuvant and CpG5 exhibits a synergistic effect, resulting in an earlier, more intense, and long-lasting immune response in subunit vaccines for PEDV. This combination holds significant promise as a robust candidate for the development of vaccine adjuvant.

Gaston Ramon's Big Four

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

Development and evaluation of a multi-epitope subunit vaccine against Mycoplasma synoviae infection

Mycoplasma synoviae is an extremely significant avian pathogen, causing substantial financial harm to poultry farmers worldwide, and impacting both chicken and turkey production. Multi-epitope vaccines offer higher immunity and lower allergenicity compared to conventional vaccines. In this study, our objective is to develop a multi-epitope vaccine for M. synoviae (MSMV) and to evaluate the immune responses and protective efficacy of MSMV in chickens. We successfully identified a total of 14 B-cell, 5 MHC-I, and 16 MHC-II binding epitopes from the immunodominant proteins RS01790, BMP, GrpE, RS00900, and RS00275. Subsequently, we synthesized the multi-epitope vaccine by connecting all conserved epitopes using appropriate linkers. The resulting MSMV demonstrated notable antigenicity, non-allergenic properties, and stability. Notably, the MSMV effectively stimulated high levels of antibody production in chickens. Furthermore, MSMV the vaccine elicited a robust cellular immune response in chickens, characterized by a well-balanced Th1/Th2-type cytokine profile and enhanced lymphocyte proliferation. In immune protection experiments, the vaccinated chickens exhibited reduced air sac lesion scores and tracheal mucosal thickness compared to their non-vaccinated chickens. Additionally, vaccinated chickens displayed lower M. synoviae loads in throat swabs. These findings collectively suggested that the MSMV holds significant potential as a promising vaccine candidate for managing M. synoviae infections.

TLR agonists as vaccine adjuvants in the prevention of viral infections: an overview

Tol-like receptor (TLR) agonists, as potent adjuvants, have gained attention in vaccine research for their ability to enhance immune responses. This study focuses on their application in improving vaccine efficacy against key viral infections, including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus, and flaviviruses, including West Nile virus, dengue virus, and chikungunya virus. Vaccines are crucial in preventing microbial infections, including viruses, and adjuvants play a vital role in modulating immune responses. However, there are still many diseases for which effective vaccines are lacking or have limited immune response, posing significant threats to human health. The use of TLR agonists as adjuvants in viral vaccine formulations holds promise in improving vaccine effectiveness. By tailoring adjuvants to specific pathogens, such as HBV, HCV, HIV, SARS-CoV-2, influenza virus, and flavivirus, protective immunity against chronic and emerging infectious disease can be elicited.

Enhancing Inactivated Yellow Fever 17D Vaccine-Induced Immune Responses in Balb/C Mice Using Alum/CpG

There are some concerns about the safety of live attenuated yellow fever vaccines (YF-live), particularly viscerotropic adverse events, which have a high mortality rate. The cellular production of the vaccine will not cause these adverse effects and has the potential to extend applicability to those who have allergic reactions, immunosuppression, and age. In this study, inactivated yellow fever (YF) was prepared and adsorbed with Alum/CpG. The cellular and humoral immunities were investigated in a mouse model. The results showed that Alum/CpG (20 μg/mL) could significantly increase the binding and neutralizing activities of the antibodies against YF. Moreover, the antibody level at day 28 after one dose was similar to that of the attenuated vaccine, but significantly higher after two doses. At the same time, Alum/CpG significantly increased the levels of IFN-γ and IL-4 cytokines.

Baseline immune states (BIS) associated with vaccine responsiveness and factors that shape the BIS

Vaccines are among the greatest inventions in medicine, leading to the elimination or control of numerous diseases, including smallpox, polio, measles, rubella, and, most recently, COVID-19. Yet, the effectiveness of vaccines varies among individuals. In fact, while some recipients mount a robust response to vaccination that protects them from the disease, others fail to respond. Multiple clinical and epidemiological factors contribute to this heterogeneity in responsiveness. Systems immunology studies fueled by advances in single-cell biology have been instrumental in uncovering pre-vaccination immune cell types and genomic features (i.e., the baseline immune state, BIS) that have been associated with vaccine responsiveness. Here, we review clinical factors that shape the BIS, and the characteristics of the BIS associated with responsiveness to frequently studied vaccines (i.e., influenza, COVID-19, bacterial pneumonia, malaria). Finally, we discuss potential strategies to enhance vaccine responsiveness in high-risk groups, focusing specifically on older adults.

Immunoinformatics-based multi-epitope vaccine design for the re-emerging monkeypox virus

BACKGROUND

On May 7, 2022, WHO reported a new monkeypox case. By May 2023 over 80,000 cases had been reported worldwide outside previously endemic nations. (This primarily affected the men who have sex with men (MSM) community in rich nations). The present research aims to develop a multi-epitope vaccine for the monkeypox virus (MPXV) using structural and cell surface proteins.

METHODS

The first part of the research involved retrieving protein sequences. The Immune Epitope Database (IEDB) was then used to analyze the B and T lymphocyte epitopes. After analyzing the sensitizing properties, toxicity, antigenicity, and molecular binding, appropriate linkers were utilizedto connect selected epitopes to adjuvants, and the structure of the vaccine was formulated. Algorithms from the field of immunoinformatics predicted the secondary and tertiary structures of vaccines. The physical, chemical, and structural properties were refined and validated to achieve maximum stability. Molecular docking and molecular dynamic simulations were subsequently employed to assess the vaccine's efficacy. Afterward, the ability of the vaccine to interact with toll-like receptors 3 and 4 (TLR3 and TLR4) was evaluated. Finally, the optimized sequence was then introduced into the Escherichia coli (E. coli) PET30A + vector.

RESULTS

An immunoinformatics evaluation suggested that such a vaccine might be safe revealed that this vaccine is safe, hydrophilic, temperature- and condition-stable, and can stimulate innate immunity by binding to TLR3 and TLR4.

CONCLUSION

Our findings suggest that the first step in MPXV pathogenesis is structural and cell surface epitopes. In this study, the most effective and promising epitopes were selected and designed throughprecision servers. Furthermore,through the utilization of multi-epitope structures and a combination of two established adjuvants, this research has the potential to be a landmarkin developing an antiviralvaccine against MPXV. However, additional in vitro and in vivo tests are required to confirm these results.

Interplay of Chemokines Receptors, Toll-like Receptors, and Host Immunological Pathways

A comprehensive framework has been established for understanding immunological pathways, which can be categorized into eradicated and tolerable immune responses. Toll-like receptors (TLRs) are associated with specific immune responses. TH1 immunity is related to TLR7, TLR8, and TLR9, while TH2 immunity is associated with TLR1, TLR2, and TLR6. TH22 immunity is linked to TLR2, TLR4, and TLR5, and THαβ (Tr1) immunity is related to TLR3, TLR7, and TLR9. The chemokine receptor CXCR5 is a marker of follicular helper T cells, and other chemokine receptors can also be classified within a framework based on host immunological pathways. On the basis of a literature review on chemokines and immunological pathways, the following associations were identified: CCR5 with TH1 responses, CCR1 with TH1-like responses, CCR4 (basophils) and CCR3 (eosinophils) with TH2 and TH9 responses, CCR10 with TH22 responses, CCR6 with TH17 responses, CXCR3 with THαβ responses, CCR8 with regulatory T cells (Treg), and CCR2 with TH3 responses. These findings contribute to the identification of biomarkers for immune cells and provide insights into host immunological pathways. Understanding the chemokine and Toll-like receptor system is crucial for comprehending the function of the innate immune system, as well as adaptive immune responses.

Influence of the Composition of Cationic Liposomes on the Performance of Cargo Immunostimulatory RNA

In this study, the impact of different delivery systems on the cytokine-inducing, antiproliferative, and antitumor activities of short immunostimulatory double-stranded RNA (isRNA) was investigated. The delivery systems, consisting of the polycationic amphiphile 1,26-bis(cholest-5-en-3-yloxycarbonylamino)-7,11,16,20 tetraazahexacosan tetrahydrochloride (2X3), and the lipid-helper dioleoylphosphatidylethanolamine (DOPE), were equipped with polyethylene glycol lipoconjugates differing in molecular weight and structure. The main findings of this work are as follows: (i) significant activation of MCP-1 and INF-α, β, and γ production in CBA mice occurs under the action of isRNA complexes with liposomes containing lipoconjugates with long PEG chains, while activation of MCP-1 and INF-γ, but not INF-α or β, was observed under the action of isRNA lipoplexes containing lipoconjugates with short PEG chains; (ii) a pronounced antiproliferative effect on B16 melanoma cells in vitro, as well as an antitumor and hepatoprotective effect in vivo, was induced by isRNA pre-complexes with non-pegylated liposomes, while complexes containing lipoconjugates with long-chain liposomes were inactive; (iii) the antitumor activity of isRNA correlated with the efficiency of its accumulation in the cells and did not explicitly depend on the activation of cytokine and interferon production. Thus, the structure of the delivery system plays a vital role in determining the response to isRNA and allows for the choice of a delivery system depending on the desired effect.

Role of toll-like receptors in the pathogenesis of COVID-19: Current and future perspectives

The coronavirus disease 2019 (COVID-19) pandemic underlines a persistent threat of respiratory tract infectious diseases and warrants preparedness for a rapid response. At present, COVID-19 has had a serious social impact and imposed a heavy global burden on public health. The exact pathogenesis of COVID-19 has not been fully elucidated. Since the outbreak of COVID-19, a renewed attention has been brought to Toll-like receptors (TLRs). Available data and new findings have demonstrated that the interaction of human TLRs and SARS-CoV-2 is a vital mediator of COVID-19 immunopathogenesis. TLRs such as TLR2, 4, 7 and 8 are potentially important in viral combat and activation of immunity in patients with COVID-19. Therapeutics targeting TLRs are currently considered promising options against the pandemic. A number of TLR-targeting immunotherapeutics are now being investigated in preclinical studies and different phases of clinical trials. In addition, innovative vaccines based on TLRs under development could be a promising approach for building a new generation of vaccines to solve the current challenges. In this review, we summarize recent progress in the role of TLRs in COVID-19, focusing the new candidate drugs targeting TLRs, the current technology and potential paths forward for employing TLR agonists as vaccine adjuvants.

Development of nucleic acid medicines based on chemical technology

Oligonucleotide-based therapeutics have attracted attention as an emerging modality that includes the modulation of genes and their binding proteins related to diseases, allowing us to take action on previously undruggable targets. Since the late 2010s, the number of oligonucleotide medicines approved for clinical uses has dramatically increased. Various chemistry-based technologies have been developed to improve the therapeutic properties of oligonucleotides, such as chemical modification, conjugation, and nanoparticle formation, which can increase nuclease resistance, enhance affinity and selectivity to target sites, suppress off-target effects, and improve pharmacokinetic properties. Similar strategies employing modified nucleobases and lipid nanoparticles have been used for developing coronavirus disease 2019 mRNA vaccines. In this review, we provide an overview of the development of chemistry-based technologies aimed at using nucleic acids for developing therapeutics over the past several decades, with a specific emphasis on the structural design and functionality of chemical modification strategies.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

Factor VIII trafficking to CD4+ T cells shapes its immunogenicity and requires several types of antigen-presenting cells

Despite >80 years of clinical experience with coagulation factor VIII (FVIII) inhibitors, surprisingly little is known about the in vivo mechanism of this most serious complication of replacement therapy for hemophilia A. These neutralizing antidrug alloantibodies arise in ∼30% of patients. Inhibitor formation is T-cell dependent, but events leading up to helper T-cell activation have been elusive because of, in part, the complex anatomy and cellular makeup of the spleen. Here, we show that FVIII antigen presentation to CD4+ T cells critically depends on a select set of several anatomically distinct antigen-presenting cells, whereby marginal zone B cells and marginal zone and marginal metallophilic macrophages but not red pulp macrophages (RPMFs) participate in shuttling FVIII to the white pulp in which conventional dendritic cells (DCs) prime helper T cells, which then differentiate into follicular helper T (Tfh) cells. Toll-like receptor 9 stimulation accelerated Tfh cell responses and germinal center and inhibitor formation, whereas systemic administration of FVIII alone in hemophilia A mice increased frequencies of monocyte-derived and plasmacytoid DCs. Moreover, FVIII enhanced T-cell proliferation to another protein antigen (ovalbumin), and inflammatory signaling-deficient mice were less likely to develop inhibitors, indicating that FVIII may have intrinsic immunostimulatory properties. Ovalbumin, which, unlike FVIII, is absorbed into the RPMF compartment, fails to elicit T-cell proliferative and antibody responses when administered at the same dose as FVIII. Altogether, we propose that an antigen trafficking pattern that results in efficient in vivo delivery to DCs and inflammatory signaling, shape the immunogenicity of FVIII.

Two peptides derivate from Acinetobacter baumannii outer membrane protein K as vaccine candidates: a comprehensive in silico study

BACKGROUND

The lack of appropriate vaccines is an obstacle to the effective management of A. baumannii infections. Peptide vaccines offer an attractive and promising preventive strategy against A. baumannii.

OBJECTIVE

In this study, we identified specific T cell epitopes of A. baumannii outer membrane protein K (OMPK) using comprehensive bioinformatics and detailed molecular docking analysis.

METHODS

Both class-I and class-II T cell epitopes of A. baumannii OMPK were predicted by three tools namely IEDB, SYFPEITHI, and ProPred. The predicted epitopes were shortlisted based on several analyses including prediction scoring, clustering, exclusion of human similarity, considering immunogenicity and cytokine production, and removal of toxic and/or allergen epitopes. The epitopic peptides with high prediction scores and appropriate properties containing both class-I and class-II T cell epitopes were selected. Two of these class I/II epitopic peptides were chosen for molecular docking studies and assessing their physicochemical properties as vaccine candidates.

RESULTS

The results showed many T-cell epitopes of OMPK that could be evaluated for possible immunogenicity. Two of these epitopes (containing both class-I and II epitopes) had high prediction scores, were predicted by several tools, attached to several HLAs, and had the best docking score. They had different physicochemical properties and were conserved among Acinetobacter species.

DISCUSSION

We identified the A. baumannii OMPK high immunogenic class-I and class-II T cell epitopes and introduced two promising high immunogenic peptides as vaccine candidates. It is recommended to perform in vitro/in vivo investigation of these peptides to determine their true efficacy and efficiency.

Practical Considerations for Next-Generation Adjuvant Development and Translation

Over the last several years, there has been increased interest from academia and the pharmaceutical/biotech industry in the development of vaccine adjuvants for new and emerging vaccine modalities. Despite this, vaccine adjuvant development still has some of the longest timelines in the pharmaceutical space, from discovery to clinical approval. The reasons for this are manyfold and range from complexities in translation from animal to human models, concerns about safety or reactogenicity, to challenges in sourcing the necessary raw materials at scale. In this review, we will describe the current state of the art for many adjuvant technologies and how they should be approached or applied in the development of new vaccine products. We postulate that there are many factors to be considered and tools to be applied earlier on in the vaccine development pipeline to improve the likelihood of clinical success. These recommendations may require a modified approach to some of the common practices in new product development but would result in more accessible and practical adjuvant-containing products.

A state-of-the-art methodology for high-throughput in silico vaccine discovery against protozoan parasites and exemplified with discovered candidates for Toxoplasma gondii

Vaccine discovery against eukaryotic parasites is not trivial as highlighted by the limited number of known vaccines compared to the number of protozoal diseases that need one. Only three of 17 priority diseases have commercial vaccines. Live and attenuated vaccines have proved to be more effective than subunit vaccines but adversely pose more unacceptable risks. One promising approach for subunit vaccines is in silico vaccine discovery, which predicts protein vaccine candidates given thousands of target organism protein sequences. This approach, nonetheless, is an overarching concept with no standardised guidebook on implementation. No known subunit vaccines against protozoan parasites exist as a result of this approach, and consequently none to emulate. The study goal was to combine current in silico discovery knowledge specific to protozoan parasites and develop a workflow representing a state-of-the-art approach. This approach reflectively integrates a parasite's biology, a host's immune system defences, and importantly, bioinformatics programs needed to predict vaccine candidates. To demonstrate the workflow effectiveness, every Toxoplasma gondii protein was ranked in its capacity to provide long-term protective immunity. Although testing in animal models is required to validate these predictions, most of the top ranked candidates are supported by publications reinforcing our confidence in the approach.

Efficiency of Interferon-γ in Activating Dendritic Cells and Its Potential Synergy with Toll-like Receptor Agonists

Interferon-γ (IFN-γ) is a cytokine that plays an important role in immune regulation, especially in the activation and differentiation of immune cells. Toll-like receptors (TLRs) are a family of pattern-recognition receptors that sense structural motifs related to pathogens and alert immune cells to the invasion. Both IFN-γ and TLR agonists have been used as immunoadjuvants to augment the efficacy of cancer immunotherapies and vaccines against infectious diseases or psychoactive compounds. In this study, we aimed to explore the potential of IFN-γ and TLR agonists being applied simultaneously to boost dendritic cell activation and the subsequent antigen presentation. In brief, murine dendritic cells were treated with IFN-γ and/or the TLR agonists, polyinosinic-polycytidylic acid (poly I:C), or resiquimod (R848). Next, the dendritic cells were stained for an activation marker, a cluster of differentiation 86 (CD86), and the percentage of CD86-positive cells was measured by flow cytometry. From the cytometric analysis, IFN-γ efficiently stimulated a considerable number of the dendritic cells, while the TLR agonists by themselves could merely activate a few compared to the control. The combination of IFN-γ with poly I:C or R848 triggered a higher amount of dendritic cell activation than IFN-γ alone. For instance, 10 ng/mL IFN-γ with 100 µg/mL poly I:C achieved 59.1% cell activation, which was significantly higher than the 33.4% CD86-positive cells obtained by 10 ng/mL IFN-γ. These results suggested that IFN-γ and TLR agonists could be applied as complementary systems to promote dendritic cell activation and antigen presentation. There might be a synergy between the two classes of molecules, but further investigation is warranted to ascertain the interaction of their promotive activities.