CpG Oligonucleotides as Vaccine Adjuvants

Recent developments in peptide vaccines against Glioblastoma, a review and update

Glioblastoma multiforme (GBM) is the most prevalent invasive CNS tumor, with a high incidence rate and a high likelihood of recurrence in most patients. Despite available treatments, recurrent glioblastoma (rGBM) exhibits growing resistance to chemotherapy and radiotherapy, which necessitates the development of newer methods of treatment. Peptide vaccines, a type of cancer immunotherapy, have recently attracted attention as a potentially practical therapeutic approach because they target tumor-associated or tumor-specific antigens to generate an effective immune response against cancer cells. These vaccines have been included in several clinical trials, demonstrating their safety and effectiveness by eliciting protective immune responses. However, peptide vaccines for glioblastoma face challenges due to the complex nature of intracranial brain tumors that require innovative approaches and in-depth research to increase their efficacy. The main topics covered in this article include immunological inhibitors and immune characteristics of the CNS and GBM, the basis of immunity, and the significant results of clinical trials of peptide vaccine therapy for GBM. Additionally, it examines the potential causes of the low effectiveness of these vaccines and recommends future research to address the specific challenges associated with immunotherapy in GBM. The evaluation of preliminary phase studies and phase III clinical trials will provide insights into potential immunological responses, biosecurity precautions, and clinical outcomes, guiding future vaccination initiatives to promote higher effectiveness.

Malaria Vaccines: Current Achievements and Path Forward

Malaria remains a significant global health challenge. Although the recent approval of the liver-stage vaccines RTS, S and R21 marks significant progress in malaria control, challenges remain in achieving long-lasting and broad protection. In this review, we provide an overview of the current landscape of malaria control, especially anti-malaria vaccine development. We first review the development of the RTS, S and R21 vaccines, highlighting their efficacy and limitations. We then examine other vaccines in development, including attenuated whole-sporozoite vaccines, as well as blood-stage-targeting vaccines and transmission-blocking vaccines targeting a variety of different immunogens. Additionally, we discuss emerging technologies, such as mRNA-based platforms, nanoparticle delivery systems, and novel adjuvants, assessing their potential to enhance the efficacy and mitigate the waning immunity concerns of most malaria vaccines. We believe that the identification of novel immunogen candidates, together with continued innovation in vaccine design and delivery, will enable us to win the fight against malaria in the future.

Aptamer-ODN Chimeras: Enabling Cell-Specific ODN Targeting Therapy

Oligonucleotides (ODNs) such as siRNA, saRNA, and miRNA regulate gene expression through a variety of molecular mechanisms and show unique potential in the treatment of genetic diseases and rare diseases, but their clinical application is still limited by the efficiency of the delivery system, especially the problem of the insufficient targeting of extrahepatic tissues. As homologous nucleic acid molecules, aptamers have become a key tool to improve the targeted delivery of ODNs. Aptamer-ODN chimeras can not only bind to multiple proteins on the cell surface with high specificity and selectivity, but they can also internalize into cells. Furthermore, they outperform traditional delivery systems in terms of cost-effectiveness and chemical modification flexibility. This review systematically summarizes the origin and progress of aptamer-ODN chimera therapy, discusses some innovative design strategies, and proposes views on the future direction of aptamer-ODN chimeras.

Differential innate immune activation by four different CpG-ODNs in porcine and murine cells: Implications for vaccine design

Synthetic oligodeoxynucleotides containing unmethylated cytosine-guanine motifs (CpG-ODNs) are immunostimulants widely used as vaccine adjuvants. This study evaluated the innate immune responses induced by four CpG-ODNs: [2395 (class C), 1826, 1018, and 2007 (class B)] in porcine and murine cells, representing species of veterinary and preclinical interest, respectively. Porcine peripheral blood mononuclear cells and murine splenocytes were stimulated in vitro with each CpG-ODN, and the mRNA expression of IL-6, IL-12p40, IFN-β, IFN-γ, TNF, and TLR9 was assessed by RT-qPCR. In porcine cells, only CpG-ODN 2395 significantly upregulated IL-6, IL-12p40, and TLR9. In murine cells, all CpG-ODNs induced IL-6; CpG-ODNs 2395, 1826, and 1018 upregulated IL-12p40; and only CpG-ODN 2395 induced TLR9. Stimulation with CpG-ODNs 2395 and 1018 enhanced IFN-β and IFN-γ expression in porcine cells. In contrast, murine cells showed increased IFN-β levels in response to CpG-ODNs 2395 and 1826, and upregulated IFN-γ following stimulation with CpG-ODNs 2395, 1826, and 1018. TNF expression was exclusively induced in porcine cells by CpG-ODN 1018, 2395, and 2007. Notably, CpG-ODN 1826 exhibited species-specific activity in mice, inducing IL-6, IL-12p40, IFN-β, and IFN-γ. These findings reveal significant interspecies differences in CpG-ODN-induced immune responses, emphasizing the importance of species-specific considerations when selecting CpG-ODNs as vaccine adjuvants for preclinical and veterinary applications.

Metabolic adaptations driving innate immune memory: mechanisms and therapeutic implications

Immune memory is a hallmark of the adaptive immune system. However, recent research reveals that innate immune cells also retain memory of prior pathogen exposure that prompts enhanced responses to subsequent infections. This phenomenon is termed "innate immune memory" or "trained immunity." Notably, remodeling of cellular metabolism, which closely links to epigenetic reprograming, is a prominent feature of innate immune memory. Adaptations in glycolysis, the tricarboxylic acid cycle, oxidative phosphorylation, glutaminolysis, and lipid synthesis pathways are critical for establishing innate immune memory. This review provides an overview of the current understanding of how metabolic adaptations drive innate immune memory. This understanding is fundamental to understanding innate immune system functions and advancing therapies against infectious diseases.

A QS21 + CpG-Adjuvanted Trivalent HSV-2 Vaccine and Trivalent HSV-2 mRNA Vaccine Induce a Strong Immune Response, Protect Against HSV-2 Infection, and Cross-Protect Against HSV-1 Infection in Mice

BACKGROUND

HSV-2 infection continues to be a significant global health concern, as there are no approved vaccines despite numerous attempts at development.

METHODS

This study explored the immunogenicity and protective efficacy of aluminum- or QS21 + CpG-adjuvanted trivalent HSV-2 vaccines and a trivalent HSV-2 mRNA vaccine incorporating the gC2, gD2, and gE2 antigens.

RESULTS

Our results demonstrated that the QS21 + CpG-adjuvanted subunit vaccine and mRNA vaccines successfully induced robust antigen-specific humoral and cellular immune responses and provided significant protection against both HSV-2 and HSV-1 infection. These vaccines showed remarkable efficiency in reducing the viral load and preventing clinical symptoms in mice, highlighting their potential for clinical application. Conversely, the aluminum-adjuvanted vaccine exhibited limited effectiveness, emphasizing the superiority of the QS21 + CpG-adjuvanted and mRNA vaccines.

CONCLUSIONS

These findings provide valuable insights for the continued development of effective HSV vaccines and suggest promising strategies for preventing both HSV-2 and HSV-1 infection.

From genetic code to global health: the impact of nucleic acid vaccines on disease prevention and treatment

Vaccinology has revolutionized modern medicine, delivering groundbreaking solutions to prevent and control infectious diseases while pioneering innovative strategies to tackle non-infectious challenges, including cancer. Traditional vaccines faced inherent limitations, driving the evolution of next-generation vaccines such as subunit vaccines, peptide-based vaccines, and nucleic acid-based platforms. Among these, nucleic acid-based vaccines, including DNA and mRNA technologies, represent a major innovation. Pioneering studies in the 1990s demonstrated their ability to elicit immune responses by encoding specific antigens. Recent advancements in delivery systems and molecular engineering have overcome initial challenges, enabling their rapid development and clinical success. This review explores nucleic acid-based vaccines, including chemically modified variants, by examining their mechanisms, structural features, and therapeutic potential, while underscoring their pivotal role in modern immunization strategies and expanding applications across contemporary medicine.

An off-target effect of class A CpG-oligonucleotides on suppressing the cyclic GMP-AMP synthase signaling in fibroblastic reticular cells

Background

Class A CpG-oligonucleotides (ODNs), a Toll-like receptor 9 (TLR9) agonist, have been applied for treating inflammatory diseases and cancer in preclinical studies and clinical trials. A recent study has reported that class A ODNs can activate the Cyclic GMP-AMP synthase (cGAS) signaling to regulate the inflammatory response in human monocytes. However, it remains unknown whether class A ODNs can activate the cGAS pathways in other cell types, such as fibroblastic reticular cells (FRC), which play critical roles in modulating the immune environments during inflammatory diseases and cancer.

Methods

To understand the role of class A ODN in regulating the cGAS signaling in FRC, we treated mouse FRC and human fibroblast with class A ODN, a cGAS agonist (HT-DNA), and combined class A and HT-DNA.

Results

Unexpectedly, we found that class A ODNs suppress the cGAS level and downstream signaling in human and murine FRC. The class A ODN-induced suppression effect on cGAS is limited in FRC, but not other immune cell types, and is independent of TLR9. Performing pulldown assay and Mass spectrum, we found that class A ODNs regulate the cGAS level post translationally by interacting with cGAS and ZNF598, an E3 ubiquitin ligase.

Conclusion

Our data reveal an unrecognized off-target effect of class A ODN on suppressing the cGAS signaling in FRCs, which should be considered when designing class A ODN regimens for inflammatory diseases and cancer.

Mucosal immunotherapy targeting APC in lung disease

Several studies have demonstrated that the pulmonary immune response is primarily facilitated by antigen-presenting cells (APCs), and that both professional and non-professional APCs contribute to overall pulmonary immunity. APCs play unique roles and mechanisms in pathogen elimination and immunomodulation. Mucosal immunity exhibits potential advantages over traditional parenteral immunity in that it stimulates immune defenses in mucosal and systemic tissues, which is important for reducing the burden of lung disease. However, obtaining a comprehensive understanding of the crosstalk between mucosal immunity and APC in the context of various lung diseases remains challenging. This mini-review aimed to elucidate the mechanisms of novel mucosal immunity, targeting APC action during lung infections, allergies, and malignant tumorigenesis. This minreview provides important insights into more effective therapeutic approaches for various lung diseases.

DNA Nanostructures-Based In Situ Cancer Vaccines: Mechanisms and Applications

Current tumor vaccines suffer from inadequate immune responsive due to the insufficient release of tumor antigens, low tumor infiltration, and immunosuppressive microenvironment. DNA nanostructures with their ability to precisely engineer, controlled release, biocompatibility, and the capability to augment the immunogenicity of tumor microenvironment, have gained significant attention for their potential to revolutionize vaccine designing. This review summarizes various applications of DNA nanostructures in the construction of in situ cancer vaccines, which can generate tumor-associated antigens directly from damaged tumors for cancer immune-stimulation. The mechanisms and components of cancer vaccines are listed, the specific strategies for constructing in situ vaccines using DNA nanostructures are explored and their underlying mechanisms of action are elucidated. The immunogenic cell death (ICD) induced by chemotherapeutic agents, photothermal therapy (PTT), photodynamic therapy (PDT), and radiation therapy (RT) and the related cancer vaccines building strategies are systematically summarized. The applications of different DNA nanostructures in various cancer immunotherapy are elaborated, which exerts precise, long-lasting, and robust immune responses. The current challenges and future prospectives are proposed. This review provides a holistic understanding of the evolving role of DNA nanostructures for in situ vaccine development.

Clinical applications of oligonucleotides for cancer therapy

Oligonucleotide therapeutics (ONTs) represent a rapidly evolving modality for cancer treatment, capitalizing on their ability to modulate gene expression with high specificity. With more than 20 nucleic acid-based therapies that gained regulatory approval, advances in chemical modifications, sequence optimization, and novel delivery systems have propelled ONTs from research tools to clinical realities. ONTs, including siRNAs, antisense oligonucleotides, saRNA, miRNA, aptamers, and decoys, offer promising solutions for targeting previously "undruggable" molecules, such as transcription factors, and enhancing cancer immunotherapy by overcoming tumor immune evasion. The promise of ONT application in cancer treatment is exemplified by the recent FDA approval of the first oligonucleotide-based treatment to myeloproliferative disease. At the same time, there are challenges in delivering ONTs to specific tissues, mitigating off-target effects, and improving cellular uptake and endosomal release. This review provides a comprehensive overview of ONTs in clinical trials, emerging delivery strategies, and innovative therapeutic approaches, emphasizing the role of ONTs in immunotherapy and addressing hurdles that hinder their clinical translation. By examining advances and remaining challenges, we highlight opportunities for ONTs to revolutionize oncology and enhance patient outcomes.

Bacterial-Mediated In Situ Engineering of Tumour-Associated Macrophages for Cancer Immunotherapy

BACKGROUND/OBJECTIVES

Tumour-associated macrophages (TAMs) are critical components of the tumour microenvironment (TME), significantly influencing cancer progression and treatment resistance. This review aims to explore the innovative use of engineered bacteria to reprogram TAMs, enhancing their anti-tumour functions and improving therapeutic outcomes.

METHODS

We conducted a systematic review following a predefined protocol. Multiple databases were searched to identify relevant studies on TAMs, their phenotypic plasticity, and the use of engineered bacteria for reprogramming. Inclusion and exclusion criteria were applied to select studies, and data were extracted using standardised forms. Data synthesis was performed to summarise the findings, focusing on the mechanisms and therapeutic benefits of using non-pathogenic bacteria to modify TAMs.

RESULTS

The review summarises the findings that engineered bacteria can selectively target TAMs, promoting a shift from the tumour-promoting M2 phenotype to the tumour-fighting M1 phenotype. This reprogramming enhances pro-inflammatory responses and anti-tumour activity within the TME. Evidence from various studies indicates significant tumour regression and improved immune responses following bacterial therapy.

CONCLUSIONS

Reprogramming TAMs using engineered bacteria presents a promising strategy for cancer therapy. This approach leverages the natural targeting abilities of bacteria to modify TAMs directly within the tumour, potentially improving patient outcomes and offering new insights into immune-based cancer treatments. Further research is needed to optimise these methods and assess their clinical applicability.

Tumor microbiome: roles in tumor initiation, progression, and therapy

Over the past few years, the tumor microbiome is increasingly recognized for its multifaceted involvement in cancer initiation, progression, and metastasis. With the application of 16S ribosomal ribonucleic acid (16S rRNA) sequencing, the intratumoral microbiome, also referred to as tumor-intrinsic or tumor-resident microbiome, has also been found to play a significant role in the tumor microenvironment (TME). Understanding their complex functions is critical for identifying new therapeutic avenues and improving treatment outcomes. This review first summarizes the origins and composition of these microbial communities, emphasizing their adapted diversity across a diverse range of tumor types and stages. Moreover, we outline the general mechanisms by which specific microbes induce tumor initiation, including the activation of carcinogenic pathways, deoxyribonucleic acid (DNA) damage, epigenetic modifications, and chronic inflammation. We further propose the tumor microbiome may evade immunity and promote angiogenesis to support tumor progression, while uncovering specific microbial influences on each step of the metastatic cascade, such as invasion, circulation, and seeding in secondary sites. Additionally, tumor microbiome is closely associated with drug resistance and influences therapeutic efficacy by modulating immune responses, drug metabolism, and apoptotic pathways. Furthermore, we explore innovative microbe-based therapeutic strategies, such as engineered bacteria, oncolytic virotherapy, and other modalities aimed at enhancing immunotherapeutic efficacy, paving the way for microbiome-centered cancer treatment frameworks.

Augmented immunogenicity of the HPV16 DNA vaccine via dual adjuvant approach: integration of CpG ODN into plasmid backbone and co-administration with IL-28B gene adjuvant

Therapeutic human papillomavirus (HPV) DNA vaccine is an attractive option to control existed HPV infection and related lesions. The two early viral oncoproteins, E6 and E7, are continuously expressed in most HPV-related pre- and cancerous cells, and are ideal targets for therapeutic vaccines. We have previously developed an HPV 16 DNA vaccine encoding a modified E7/HSP70 (mE7/HSP70) fusion protein, which demonstrated significant antitumor effects in murine models. In this study, we employed multifaceted approach to enhance the potency of the HPV16 DNA vaccine. Strategies including inserting CpG oligodeoxynucleotide (CpG ODNs) into the vaccine vector backbone, selecting cytokine gene adjuvants, combining plasmids encoding mE6/HSP70 and mE7/HSP70, and utilizing electroporation for vaccination. Our findings revealed that mice immunized with CpG-modified vaccines, coupled with an IL-28B gene adjuvant exhibited heightened antigen-specific CD8+ T cell responses. Additionally, the combination of mE6/HSP70 and mE7/HSP70 plasmids synergistically enhanced the specific CD8+ T cell response. Furthermore, vaccination with CpG-modified mE7/HSP70 and mE6/HSP70 plasmids, alongside the Interleukin-28B (IL-28B) gene adjuvant, generated substantial preventive and therapeutic antitumor effects against HPV E6- and E7-expressing tumors in C57BL/6 mice. These results suggested that integrating these multiple strategies into an HPV DNA vaccine holds promise for effectively controlling HPV infection and related diseases.

Pulmonary Delivery of Nonviral Nucleic Acid-Based Vaccines With Spotlight on Gold Nanoparticles

Nucleic acid-based vaccines are leading-edge tools in developing next-generation preventative care. Much research has been done to convert vaccine gene therapy from an invasive to a noninvasive administration approach. The lung's large surface area and permeability make the pulmonary route a promising noninvasive delivery option for vaccines, with systemic and local applications. This review summarizes the challenges and the approaches that have been carried out to optimize the delivery of nucleic acids through the pulmonary route for vaccination purposes in recent years, with a spotlight on gold nanoparticles (AuNPs). Nonviral delivery systems have been widely explored, and AuNPs with their unique properties are emerging as promising tools for nucleic acid vaccines due to surface functionalization with mucus-penetrating polymers and targeting moieties that can bypass the barriers in pulmonary delivery and successfully deliver nucleic acids to the cells of interest. However, while promising, several challenges remain including selectively overcoming the lungs' immunological surveillance and adhesive mucus.

Enhancing antibody levels and T cell activity of quadrivalent influenza vaccine by combining it with CpG HP021

Influenza virus infections are a serious danger to people's health worldwide as they are responsible for seasonal flu outbreaks. There is an urgent need to improve the effectiveness and durability longevity of the immune response to influenza vaccines. We synthesized the CpG HP021 and examined the impact of it on the immune response to an influenza vaccine. In BALB/c mice, hemagglutination inhibition (HI) titers to the vaccine were increased four- to eightfold against H1N1, H3N2, BV, and BY viruses by 3 μg IIV4 + 40 μg CpG HP021 compared with those of the non-adjuvanted IIV4 group, and the CpG HP021 group had a broader HI activity. Additionally, the immune response was directed towards Type 1 T helper (Th1) cells due to the CpG HP021 adjuvant. The CpG HP021-adjuvanted IIV4 induced a higher number of T cells secreting interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), and increased the percentage of effector memory T cells in mice. In SD rats, the immune responses induced by IIV4 with CpG HP021 were similar to those in BALB/c mice. The development of CpG HP021 may expand the options for adjuvants in vaccines against infectious diseases.

Rational Design of an Epidermal Growth Factor Receptor Vaccine: Immunogenicity and Antitumor Research

The epidermal growth factor receptor (EGFR) is frequently overexpressed in a variety of human epithelial tumors, and its aberrant activation plays a pivotal role in promoting tumor growth, invasion, and metastasis. The clinically approved passive EGFR-related therapies have numerous limitations. Seven EGFR-ECD epitope peptides (EG1-7) were selected through bioinformatics epitope prediction tools including NetMHCpan-4.1, NetMHCIIpan-3.2, and IEDB Consensus (v2.18 and v2.22) and fused to the translocation domain of diphtheria toxin (DTT). The A549 tumor model was successfully established in a murine mouse model. The vaccine was formulated by combining the adjuvants Alum and CpG and subsequently assessed for its immunogenicity and anti-tumor efficacy. DTT-EG (3;5;6;7) vaccines elicited specific humoral and cellular immune responses and effectively suppressed tumor growth in both prophylactic and therapeutic mouse tumor models. The selected epitopes EG3 (HGAVRFSNNPALCNV145-159), EG5 (KDSLSINATNIKHFK346-360), EG6 (VKEITGFLLIQAWPE398-412), and EG7 (LCYANTINWKKLFGT469-483) were incorporated into vaccines for active immunization, representing a promising strategy for the treatment of tumors with overexpressed epidermal growth factor receptor (EGFR). The vaccine design and fusion method employed in this study demonstrate a viable approach toward the development of cancer vaccines.

Tumor cell membrane-based vaccines: A potential boost for cancer immunotherapy

Because therapeutic cancer vaccines can, in theory, eliminate tumor cells specifically with relatively low toxicity, they have long been considered for application in repressing cancer progression. Traditional cancer vaccines containing a single or a few discrete tumor epitopes have failed in the clinic, possibly due to challenges in epitope selection, target downregulation, cancer cell heterogeneity, tumor microenvironment immunosuppression, or a lack of vaccine immunogenicity. Whole cancer cell or cancer membrane vaccines, which provide a rich source of antigens, are emerging as viable alternatives. Autologous and allogenic cellular cancer vaccines have been evaluated as clinical treatments. Tumor cell membranes (TCMs) are an intriguing antigen source, as they provide membrane-accessible targets and, at the same time, serve as integrated carriers of vaccine adjuvants and other therapeutic agents. This review provides a summary of the properties and technologies for TCM cancer vaccines. Characteristics, categories, mechanisms, and preparation methods are discussed, as are the demonstrable additional benefits derived from combining TCM vaccines with chemotherapy, sonodynamic therapy, phototherapy, and oncolytic viruses. Further research in chemistry, biomedicine, cancer immunology, and bioinformatics to address current drawbacks could facilitate the clinical adoption of TCM vaccines.

An effective vaccine against influenza A virus based on the matrix protein 2 (M2)

The ever-increasing antigenic diversity of the hemagglutinin (HA) of influenza A virus (IAV) poses a significant challenge for effective vaccine development. Notably, the matrix protein 2 (M2) is a highly conserved 97 amino acid long transmembrane tetrameric protein present in the envelope of IAV. More than 99 % of IAV strains circulating in American swine herds share the identical pandemic (pdm) isoform of M2, making it an ideal target antigen for a vaccine that could elicit broadly protective immunity. Here, using soluble nanoscale membrane assemblies termed nanodiscs (NDs), we designed this membrane mimetic nanostructures displaying full-length M2 in its natural transmembrane configuration (M2ND). Intramuscular (IM) immunization of swine with M2ND mixed with conventional emulsion adjuvant elicited M2-specific IgG antibodies in the serum that recognized influenza virions and M2-specific interferon-γ secreting cells present in the blood. Intranasal (IN) immunization with M2ND adjuvanted with a mycobacterial extract elicited M2-specific IgA in mucosal secretions that also recognized IAV. Immunization with an influenza whole inactivated virus (WIV) vaccine supplemented with a concurrent IM injection of M2ND mixed with an emulsion adjuvant increased the level of protective immunity afforded by the former against a challenge with an antigenically distinct H3N2 IAV, as exhibited by an enhanced elimination of virus from the lung. The lone IM administration of the M2ND vaccine mixed with an emulsion adjuvant provided measurable protection as evidenced by a >10-fold reduction or complete elimination of the challenge virus from the lung, but it did not diminish the viral load in nasal secretions nor the extent of pneumonia that ensued after the virus challenge. In contrast, an improved formulation of the M2ND vaccine that incorporated synthetic CpG oligodeoxynucleotides (CpG-ODN) in the nanostructures administered alone, via the IN and IM routes combined, provided a significant level of protective immunity against IAV as evidenced by a decreased viral load in both the upper and lower respiratory tracts and fully eliminated the occurrence of pneumonia in 89 % of the pigs immunized with this biologic. Notably, to be effective, the M2 protein must be displayed in the ND assemblies, as shown by the observation that simply mixing M2 with empty NDs incorporating CpG-ODN (eND-CpG-ODN) did not provide protective immunity. This novel M2-based vaccine offers great promise to help increase the breadth of protection afforded by conventional WIV vaccines against the diversity of IAV in circulation and, plausibly, as a broadly protective stand-alone biologic.

New insights for the development of efficient DNA vaccines

Despite the great potential of DNA vaccines for a broad range of applications, ranging from prevention of infections, over treatment of autoimmune and allergic diseases to cancer immunotherapies, the implementation of such therapies for clinical treatment is far behind the expectations up to now. The main reason is the poor immunogenicity of DNA vaccines in humans. Consequently, the improvement of the performance of DNA vaccines in vivo is required. This mini-review provides an overview of the current state of DNA vaccines and the various strategies to enhance the immunogenic potential of DNA vaccines, including (i) the optimization of the DNA construct itself regarding size, nuclear transfer and transcriptional regulation; (ii) the use of appropriate adjuvants; and (iii) improved delivery, for example, by careful choice of the administration route, physical methods such as electroporation and nanomaterials that may allow cell type-specific targeting. Moreover, combining nanoformulated DNA vaccines with other immunotherapies and prime-boost strategies may help to enhance success of treatment.

A Multi-Functional Nanoadjuvant Coupling Manganese with Toll-Like 9 Agonist Stimulates Potent Innate and Adaptive Anti-Tumor Immunity

The effectiveness of Toll-like 9 agonists (CpG) as an adjuvant for tumor immunotherapy is restricted due to their insufficient ability to activate anti-tumor immunity. To address that, the common nutrient metal ions are explored (Mn2+, Cu2+, Ca2+, Mg2+, Zn2+, Fe3+, and Al3+), identifying Mn2+ as a key enhancer of CpG to mediate immune activation by augmenting the STING-NF-κB pathway. Mn2+ and CpG are then self-assembled with epigallocatechin gallate (EGCG) into a nanoadjuvant MPN/CpG. Local delivery of MPN/CpG effectively inhibits tumor growth in a B16 melanoma-bearing mouse model, reshaping the tumor microenvironment (TME) by repolarizing M2-type tumor-associated macrophages (TAMs) to an M1-type and boosting intra-tumoral infiltration of CD8+/CD4+ T lymphocytes and DCs. Furthermore, compared to free CpG, MPN/CpG exhibits heightened accumulation in lymph nodes, enhancing CpG uptake and DC activation, consequently inducing significant antigen-specific cytotoxic CD8+ T cell immune response and humoral immunity. In a prophylactic tumor-bearing mouse model, MPN/CpG vaccination with OVA antigen significantly delays B16-OVA melanoma growth and extends mouse survival. These findings underscore the potential of MPN/CpG as a multifunctional adjuvant platform to drive powerful innate and adaptive immunity and regulate TME against tumors.

The clinical potential of l-oligonucleotides: challenges and opportunities

Chemically modified nucleotides are central to the development of biostable research tools and oligonucleotide therapeutics. In this context, l-oligonucleotides, the synthetic enantiomer of native d-nucleic acids, hold great promise. As enantiomers, l-oligonucleotides share the same physical and chemical properties as their native counterparts, yet their inverted l-(deoxy)ribose sugars afford them orthogonality towards the stereospecific environment of biology. Notably, l-oligonucleotides are highly resistant to degradation by cellular nucleases, providing them with superior biostability. As a result, l-oligonucleotides are being increasingly utilized for the development of diverse biomedical technologies, including molecular imaging tools, diagnostic biosensors, and aptamer-based therapeutics. Herein, we present recent such examples that highlight the clinical potential of l-oligonucleotides. Additionally, we provide our perspective on the remaining challenges and practical considerations currently associated with the use of l-oligonucleotides and explore potential solutions that will lead to the broader adoption of l-oligonucleotides in clinical applications.

Continuous Treatment with IncobotulinumtoxinA Despite Presence of BoNT/A Neutralizing Antibodies: Immunological Hypothesis and a Case Report

Botulinum Neurotoxin A (BoNT/A) is a bacterial protein that has proven to be a valuable pharmaceutical in therapeutic indications and aesthetic medicine. One major concern is the formation of neutralizing antibodies (nAbs) to the core BoNT/A protein. These can interfere with the therapy, resulting in partial or complete antibody (Ab)-mediated secondary non-response (SNR) or immunoresistance. If titers of nAbs reach a level high enough that all injected BoNT/A molecules are neutralized, immunoresistance occurs. Studies have shown that continuation of treatment of neurology patients who had developed Ab-mediated partial SNR against complexing protein-containing (CPC-) BoNT/A was in some cases successful if patients were switched to complexing protein-free (CPF-) incobotulinumtoxinA (INCO). This seems to contradict the layperson's basic immunological understanding that repeated injection with the same antigen BoNT/A should lead to an increase in antigen-specific antibody titers. As such, we strive to explain how immunological memory works in general, and based on this, we propose a working hypothesis for this paradoxical phenomenon observed in some, but not all, neurology patients with immunoresistance. A critical factor is the presence of potentially immune-stimulatory components in CPC-BoNT/A products that can act as immunologic adjuvants and activate not only naïve, but also memory B lymphocyte responses. Furthermore, we propose that continuous injection of a BoN/TA formulation with low immunogenicity, e.g., INCO, may be a viable option for aesthetic patients with existing nAbs. These concepts are supported by a real-world case example of a patient with immunoresistance whose nAb levels declined with corresponding resumption of clinical response despite regular INCO injections.

Transforming vaccinology

The COVID-19 pandemic placed the field of vaccinology squarely at the center of global consciousness, emphasizing the vital role of vaccines as transformative public health tools. The impact of vaccines was recently acknowledged by the award of the 2023 Nobel Prize in Physiology or Medicine to Katalin Kariko and Drew Weissman for their seminal contributions to the development of mRNA vaccines. Here, we provide a historic perspective on the key innovations that led to the development of some 27 licensed vaccines over the past two centuries and recent advances that promise to transform vaccines in the future. Technological revolutions such as reverse vaccinology, synthetic biology, and structure-based design transformed decades of vaccine failures into successful vaccines against meningococcus B and respiratory syncytial virus (RSV). Likewise, the speed and flexibility of mRNA vaccines profoundly altered vaccine development, and the advancement of novel adjuvants promises to revolutionize our ability to tune immunity. Here, we highlight exciting new advances in the field of systems immunology that are transforming our mechanistic understanding of the human immune response to vaccines and how to predict and manipulate them. Additionally, we discuss major immunological challenges such as learning how to stimulate durable protective immune response in humans.

β-Glucan-A promising immunocyte-targeting drug delivery vehicle: Superiority, applications and future prospects

Drug delivery technologies that could convert promising therapeutics into successful therapies have been under broad research for many years. Recently, β-glucans, natural-occurring polysaccharides extracted from many organism species such as yeast, fungi and bacteria, have attracted increasing attention to serve as drug delivery carriers. With their unique structure and innate immunocompetence, β-glucans are considered as promising carriers for targeting delivery especially when applied in the vaccine construction and oral administration of therapeutic agents. In this review, we focus on three types of β-glucans applied in the drug delivery system including yeast β-glucan, Schizophyllan and curdlan, highlighting the benefits of β-glucan based delivery system. We summarize how β-glucans as delivery vehicles have aided various therapeutics ranging from macromolecules including proteins, peptides and nucleic acids to small molecular drugs to reach desired cells or organs in terms of loading strategies. We also outline the challenges and future directions for developing the next generation of β-glucan based delivery systems.

Identification of a novel DEC-205 binding peptide to develop dendritic cell-targeting nanovaccine for cancer immunotherapy

Cancer vaccine is regarded as an effective immunotherapy approach mediated by dendritic cells (DCs) which are crucial for antigen presentation and the initiation of adaptive immune responses. However, lack of DC-targeting properties significantly hampers the efficacy of cancer vaccines. Here, by using the phage display technique, peptides targeting the endocytic receptor DEC-205 primarily found on cDC1s were initially screened. An optimized hydrolysis-resistant peptide, hr-8, was identified and conjugated to PLGA-loaded antigen (Ag) and CpG adjuvant nanoparticles, resulting in a DC-targeting nanovaccine. The nanovaccine hr-8-PLGA@Ag/CpG facilitates dendritic cell maturation and improves antigen cross-presentation. The nanovaccine can enhance the antitumor immune response mediated by CD8+ T cells by encapsulating the nanovaccine with either exogenous OVA protein antigen or endogenous gp100/E7 antigenic peptide. As a result, strong antitumor effects are observed in both anti-PD-1 responsive B16-OVA and anti-PD-1 non-responsive B16 and TC1 immunocompetent tumor models. In summary, this study presents the initial documentation of a nanovaccine that targets dendritic cells via the novel DEC-205 binding peptide. This approach offers a new method for developing cancer vaccines that can potentially improve the effectiveness of cancer immunotherapy.

Cancer Nanovaccines: Nanomaterials and Clinical Perspectives

Cancer nanovaccines represent a promising frontier in cancer immunotherapy, utilizing nanotechnology to augment traditional vaccine efficacy. This review comprehensively examines the current state-of-the-art in cancer nanovaccine development, elucidating innovative strategies and technologies employed in their design. It explores both preclinical and clinical advancements, emphasizing key studies demonstrating their potential to elicit robust anti-tumor immune responses. The study encompasses various facets, including integrating biomaterial-based nanocarriers for antigen delivery, adjuvant selection, and the impact of nanoscale properties on vaccine performance. Detailed insights into the complex interplay between the tumor microenvironment and nanovaccine responses are provided, highlighting challenges and opportunities in optimizing therapeutic outcomes. Additionally, the study presents a thorough analysis of ongoing clinical trials, presenting a snapshot of the current clinical landscape. By curating the latest scientific findings and clinical developments, this study aims to serve as a comprehensive resource for researchers and clinicians engaged in advancing cancer immunotherapy. Integrating nanotechnology into vaccine design holds immense promise for revolutionizing cancer treatment paradigms, and this review provides a timely update on the evolving landscape of cancer nanovaccines.

A review of immune modulators and immunotherapy in infectious diseases

The human immune system responds to harmful foreign invaders frequently encountered by the body and employs defense mechanisms to counteract such assaults. Various exogenous and endogenous factors play a prominent role in maintaining the balanced functioning of the immune system, which can result in immune suppression or immune stimulation. With the advent of different immune-modulatory agents, immune responses can be modulated or regulated to control infections and other health effects. Literature provides evidence on various immunomodulators from different sources and their role in modulating immune responses. Due to the limited efficacy of current drugs and the rise in drug resistance, there is a growing need for new therapies for infectious diseases. In this review, we aim to provide a comprehensive overview of different immune-modulating agents and immune therapies specifically focused on viral infectious diseases.

Novel strategy for Poxviridae prevention: Thermostable combined subunit vaccine patch with intense immune response

Poxviruses gained international attention due to the sharp rise in monkeypox cases in recent years, highlighting the urgent need for the development of a secure and reliable vaccine. This study involved the development of an innovative combined subunit vaccine (CSV) targeting poxviruses, with lumpy skin disease virus (LSDV) serving as the model virus. To this end, the potential sites for poxvirus vaccines were fully evaluated to develop and purify four recombinant proteins. These proteins were then successfully delivered to the dermis in a mouse model by utilizing dissolvable microneedle patches (DMPs). This approach simplified the vaccination procedure and significantly mitigated the associated risk. CSV-loaded DMPs contained four recombinant proteins and a novel adjuvant, CpG, which allowed DMPs to elicit the same intensity of humoral and cellular immunity as subcutaneous injection. Following immunization with SC and DMP, the mice exhibited notable levels of neutralizing antibodies, albeit at a low concentration. It is noteworthy that the CSV loaded into DMPs remained stable for at least 4 months at room temperature, effectively addressing the storage and transportation challenges. Based on the study findings, CSV-loaded DMPs are expected to be utilized worldwide as an innovative technique for poxvirus inoculation, especially in underdeveloped regions. This novel strategy is crucial for the development of future poxvirus vaccines.

Recognition of Chlamydia trachomatis by Toll-like receptor 9 is altered during persistence

Toll-like receptor 9 (TLR9) is an innate immune receptor that localizes to endosomes in antigen presenting cells and recognizes single stranded unmethylated CpG sites on bacterial genomic DNA (gDNA). Previous bioinformatic studies have demonstrated that the genome of the human pathogen Chlamydia trachomatis contains TLR9 stimulatory motifs, and correlative studies have implied a link between human TLR9 (hTLR9) genotype variants and susceptibility to infection. Here, we present our evaluation of the stimulatory potential of C. trachomatis gDNA and its recognition by hTLR9- and murine TLR9 (mTLR9)-expressing cells. Utilizing reporter cell lines, we demonstrate that purified gDNA from C. trachomatis can stimulate hTLR9 signaling, albeit at lower levels than gDNA prepared from other Gram-negative bacteria. Interestingly, we found that while C. trachomatis is capable of signaling through hTLR9 and mTLR9 during live infections in HEK293 reporter cell lines, signaling only occurs at later developmental time points. Chlamydia-specific induction of hTLR9 is blocked when protein synthesis is inhibited prior to the RB-to-EB conversion, exacerbated by the inhibition of lipooligosaccharide biosynthesis, and is significantly altered during the induction of aberrance/persistence. Our observations support the hypothesis that chlamydial gDNA is released during the conversion between the pathogen's replicative and infectious forms and during treatment with antibiotics targeting peptidoglycan assembly. Given that C. trachomatis inclusions do not co-localize with TLR9-containing vacuoles in the pro-monocytic cell line U937, our findings also hint that chlamydial gDNA is capable of egress from the inclusion, and traffics to TLR9-containing vacuoles via an as yet unknown pathway.

Sani J, Raz A, Zakeri S, Dinparast Djadid N, Abouie Mehrizi A. Malaria transmission blocking activity of Anopheles stephensi alanyl aminopeptidase N antigen formulated with MPL, CpG, and QS21 adjuvants

BACKGROUNDS

Malaria, a preventive and treatable disease, is still responsible for annual deaths reported in most tropical regions, principally in sub-Saharan Africa. Subunit recombinant transmission-blocking vaccines (TBVs) have been proposed as promising vaccines to succeed in malaria elimination and eradication. Here, a provisional study was designed to assess the immunogenicity and functional activity of alanyl aminopeptidase N (APN1) of Anopheles stephensi, as a TBV candidate, administered with MPL, CpG, and QS21 adjuvants in the murine model.

METHODOLOGY/PRINCIPAL FINDINGS

The mouse groups were immunized with recombinant APN1 (rAPN1) alone or formulated with CpG, MPL, QS-21, or a combination of adjuvants (CMQ), and the elicited immune responses were evaluated after the third immunization. The standard membrane feeding assay (SMFA) measured the functional activity of antibodies against bacterial-expressed APN1 protein in adjuvanted vaccine groups on transmission of P. falciparum (NF54) to An. stephensi mosquitoes. Evaluation of mice vaccinated with rAPN1 formulated with distinct adjuvants manifested a significant increase in the high-avidity level of anti-APN1 IgG and IgG subclasses; however, rAPN1 induced the highest level of high-avidity anti-APN1 IgG1, IgG2a, and IgG2b antibodies in the immunized vaccine group 5 (APN1/CMQ). In addition, vaccine group 5 (receiving APN1/CMQ), had still the highest level of anti-APN1 IgG antibodies relative to other immunized groups after six months, on day 180. The SMFA data indicates a trend towards higher transmission-reducing activity in groups 2 and 5, which received the antigen formulated with CpG or a combination of three adjuvants.

CONCLUSIONS/SIGNIFICANCE

The results have shown the capability of admixture to stimulate high-affinity and long-lasting antibodies against the target antigen to hinder Plasmodium parasite development in the mid-gut of An. stephensi. The attained results authenticated APN1/CMQ and APN1/CpG as a potent APN1-based TBV formulation which will be helpful in designing a vaccine in the future.

Post-Vaccination Delivery of CpG ODNs Enhances the Th2-Associated Protective Immunity of the Smallpox DNA Vaccine

Potential threat of smallpox bioterrorism and concerns related to the adverse effects of currently licensed live-virus vaccines suggest the need to develop novel vaccines with better efficacy against smallpox. Use of DNA vaccines containing specific antigen-encoding plasmids prevents the risks associated with live-virus vaccines, offering a promising alternative to conventional smallpox vaccines. In this study, we investigated the efficiency of toll-like receptor (TLR) ligands in enhancing the immunogenicity of smallpox DNA vaccines. BALB/c mice were immunized with a DNA vaccine encoding the vaccinia virus L1R protein, along with the cytosine-phosphate-guanine (CpG) motif as a vaccine adjuvant, and their immune response was analyzed. Administration of B-type CpG oligodeoxynucleotides (ODNs) as TLR9 ligands 24 h after DNA vaccination enhanced the Th2-biased L1R-specific antibody immunity in mice. Moreover, B-type CpG ODNs improved the protective effects of the DNA vaccine against the lethal Orthopoxvirus challenge. Therefore, use of L1R DNA vaccines with CpG ODNs as adjuvants is a promising approach to achieve effective immunogenicity against smallpox infection.

Sensing of an HIV-1-Derived Single-Stranded RNA-Oligonucleotide Induces Arginase 1-Mediated Tolerance

Small synthetic oligodeoxynucleotides (ODNs) can mimic microbial nucleic acids by interacting with receptor systems and promoting immunostimulatory activities. Nevertheless, some ODNs can act differently on the plasmacytoid dendritic cell (pDC) subset, shaping their immunoregulatory properties and rendering them suitable immunotherapeutic tools in several clinical settings for treating overwhelming immune responses. We designed HIV-1-derived, DNA- and RNA-based oligonucleotides (gag, pol, and U5 regions) and assessed their activity in conferring a tolerogenic phenotype to pDCs in skin test experiments. RNA-but not DNA-oligonucleotides are capable of inducing tolerogenic features in pDCs. Interestingly, sensing the HIV-1-derived single-stranded RNA-gag oligonucleotide (RNA-gag) requires both TLR3 and TLR7 and the engagement of the TRIF adaptor molecule. Moreover, the induction of a suppressive phenotype in pDCs by RNA-gag is contingent upon the induction and activation of the immunosuppressive enzyme Arginase 1. Thus, our data suggest that sensing of the synthetic RNA-gag oligonucleotide in pDCs can induce a suppressive phenotype in pDCs, a property rendering RNA-gag a potential tool for therapeutic strategies in allergies and autoimmune diseases.

Alum/CpG adjuvant promotes immunogenicity of inactivated SARS-CoV-2 Omicron vaccine through enhanced humoral and cellular immunity

The SARS-CoV-2 Omicron variant, which was classified as a variant of concern (VOC) by the World Health Organization on 26 November 2021, has attracted worldwide attention for its high transmissibility and immune evasion ability. The existing COVID-19 vaccine has been shown to be less effective in preventing Omicron variant infection and symptomatic infection, which brings new challenges to vaccine development and application. Here, we evaluated the immunogenicity and safety of an Omicron variant COVID-19 inactivated vaccine containing aluminum and CpG adjuvants in a variety of animal models. The results showed that the vaccine candidate could induce high levels of neutralizing antibodies against the Omicron variant virus and binding antibodies, and significantly promoted cellular immune response. Meanwhile, the vaccine candidate was safe. Therefore, it provided more foundation for the development of aluminum and CpG as a combination adjuvant in human vaccines.

The circulating IL-35+ regulatory B cells are associated with thyroid associated opthalmopathy

BACKGROUND

Thyroid-associated ophthalmopathy (TAO) is the most common orbital disease in adults, potentially leading to disfigurement and visual impairment. However, the causes of TAO are not fully understood. IL-35+B cells are a newly identified regulatory B cells (Bregs) in maintaining immune balance in various autoimmune diseases. Yet, the influence of IL-35+Bregs in TAO remains unexplored.

METHODS

This study enrolled 36 healthy individuals and 14 TAO patients. We isolated peripheral blood mononuclear cells and stimulated them with IL-35 and CpG for 48 h. Flow cytometry was used to measure the percentages of IL-35+Bregs.

RESULTS

The percentage of circulating IL-35+Bregs was higher in TAO patients, and this increase correlated positively with disease activity. IL-35 significantly increased the generation of IL-35+Bregs in healthy individuals. However, B cells from TAO patients exhibited potential impairment in transitioning into IL-35+Breg phenotype under IL-35 stimulation.

CONCLUSIONS

Our results suggest a potential role of IL-35+Bregs in the development of TAO, opening new avenues for understanding disease mechanisms and developing therapeutic approaches.

Epstein-Barr Virus DNA Exacerbates Arthritis in a Mouse Model via Toll-like Receptor 9

Epstein-Barr virus (EBV) DNA is known to be shed upon reactivation of latent EBV. Based on our previous findings linking Toll-like receptor-9 (TLR9) to an EBV DNA-driven surge in IL-17A production, we aimed to examine the therapeutic potential of TLR9 inhibition in EBV DNA-exacerbated arthritis in a collagen-induced arthritis (CIA) mouse model. C57BL/6J mice were administered either collagen, EBV DNA + collagen, EBV DNA + collagen + TLR9 inhibitor, or only the TLR9 inhibitor. After 70 days, paw thicknesses, clinical scores, and gripping strength were recorded. Moreover, affected joints, footpads, and colons were histologically scored. Furthermore, the number of cells co-expressing IL-17A, IFN-γ, and FOXP3 in joint sections was determined by immunofluorescence assays. Significantly decreased paw thicknesses, clinical scores, and histological scores with a significantly increased gripping strength were observed in the group receiving EBV DNA + collagen + TLR9 inhibitor, compared to those receiving EBV DNA + collagen. Similarly, this group showed decreased IL-17A+ IFN-γ+, IL-17A+ FOXP3+, and IL-17A+ IFN-γ+ FOXP3+ foci counts in joints. We show that inhibiting TLR9 limits the exacerbation of arthritis induced by EBV DNA in a CIA mouse model, suggesting that TLR9 could be a potential therapeutic target for rheumatoid arthritis management in EBV-infected individuals.

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.

A Unique Combination of Mn2+ and Aluminum Adjuvant Acted the Synergistic Effect

Introduction

The development of combinatorial adjuvants is a promising strategy to boost vaccination efficiency. Accumulating evidence indicates that manganese exerts strong immunocompetence and will become an enormous potential adjuvant. Here, we described a novel combination of Mn2+ plus aluminum hydroxide (AH) adjuvant that significantly exhibited the synergistic immune effect. Methodology. Initially, IsdB3 proteins as the immune-dominant fragment of IsdB proteins derived from Staphylococcus aureus (S. aureus) were prepared. IsdB3 proteins were identified by western blotting. Furthermore, we immunized C57/B6 mice with IsdB3 proteins plus Mn2+ and AH adjuvant. After the second immunization, the proliferation of lymphocytes was measured by the cell counting kit-8 (CCK-8) and the level of IFN-γ, IL-4, IL-10, and IL-17 cytokine from spleen lymphocytes in mice and generation of the antibodies against IsdB3 in serum was detected with ELISA, and the protective immune response was assessed through S. aureus challenge.

Results

IsdB3 proteins plus Mn2+ and AH obviously stimulated the proliferation of spleen lymphocytes and increased the secretion of IFN-γ, IL-4, IL-10, and IL-17 cytokine in mice, markedly enhanced the generation of the antibodies against IsdB3 in serum, observably decreased bacterial load in organs, and greatly improved the survival rate of mice.

Conclusion

These data showed that the combination of Mn2+ and AH significantly acted a synergistic effect, reinforced the immunogenicity of IsdB3, and offered a new strategy to increase vaccine efficiency.

Trained immunity-inducing vaccines: Harnessing innate memory for vaccine design and delivery

While the efficacy of many current vaccines is well-established, various factors can diminish their effectiveness, particularly in vulnerable groups. Amidst emerging pandemic threats, enhancing vaccine responses is critical. Our review synthesizes insights from immunology and epidemiology, focusing on the concept of trained immunity (TRIM) and the non-specific effects (NSEs) of vaccines that confer heterologous protection. We elucidate the mechanisms driving TRIM, emphasizing its regulation through metabolic and epigenetic reprogramming in innate immune cells. Notably, we explore the extended protective scope of vaccines like BCG and COVID-19 vaccines against unrelated infections, underscoring their role in reducing neonatal mortality and combating diseases like malaria and yellow fever. We also highlight novel strategies to boost vaccine efficacy, incorporating TRIM inducers into vaccine formulations to enhance both specific and non-specific immune responses. This approach promises significant advancements in vaccine development, aiming to improve global public health outcomes, especially for the elderly and immunocompromised populations.

Lipid nanoparticle-encapsulated DNA vaccine robustly induce superior immune responses to the mRNA vaccine in Syrian hamsters

DNA vaccines for infectious diseases and cancer have been explored for years. To date, only one DNA vaccine (ZyCoV-D) has been authorized for emergency use in India. DNA vaccines are inexpensive and long-term thermostable, however, limited by the low efficiency of intracellular delivery. The recent success of mRNA/lipid nanoparticle (LNP) technology in the coronavirus disease 2019 (COVID-19) pandemic has opened a new application for nucleic acid-based vaccines. Here, we report that plasmid encoding a trimeric spike protein with LNP delivery (pTS/LNP), similar to those in Moderna's COVID-19 vaccine, induced more effective humoral responses than naked pTS or pTS delivered via electroporation. Compared with TSmRNA/LNP, pTS/LNP immunization induced a comparable level of neutralizing antibody titers and significant T helper 1-biased immunity in mice; it also prolonged the maintenance of higher antigen-specific IgG and neutralizing antibody titers in hamsters. Importantly, pTS/LNP immunization exhibits enhanced cross-neutralizing activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and protects hamsters from the challenge of SARS-CoV-2 (Wuhan strain and the Omicron BA.1 variant). This study indicates that pDNA/LNPs as a promising platform could be a next-generation vaccine technology.

Amphiphilic Block Copolymer Nanostructures as a Tunable Delivery Platform: Perspective and Framework for the Future Drug Product Development

Nanoformulation of active payloads or pharmaceutical ingredients (APIs) has always been an area of interest to achieve targeted, sustained, and efficacious delivery. Various delivery platforms have been explored, but loading and delivery of APIs have been challenging because of the chemical and structural properties of these molecules. Polymersomes made from amphiphilic block copolymers (ABCPs) have shown enormous promise as a tunable API delivery platform and confer multifold advantages over lipid-based systems. For example, a COVID booster vaccine comprising polymersomes encapsulating spike protein (ACM-001) has recently completed a Phase I clinical trial and provides a case for developing safe drug products based on ABCP delivery platforms. However, several limitations need to be resolved before they can reach their full potential. In this Perspective, we would like to highlight such aspects requiring further development for translating an ABCP-based delivery platform from a proof of concept to a viable commercial product.

Recognition of Chlamydia trachomatis by Toll-Like Receptor 9 is altered during persistence

Toll-like receptor 9 (TLR9) is an innate immune receptor that localizes to endosomes in antigen presenting cells and recognizes single stranded unmethylated CpG sites on bacterial genomic DNA. Previous bioinformatic studies have indicated that the genome of the human pathogen Chlamydia trachomatis contains TLR9 stimulatory motifs, and correlative studies have implied a link between human TLR9 (hTLR9) genotype variants and susceptibility to infection. Here we present our evaluation of the stimulatory potential of C. trachomatis gDNA and its recognition by hTLR9- and murine TLR9 (mTLR9)-expressing cells. We confirm that hTLR9 colocalizes with chlamydial inclusions in the pro-monocytic cell line, U937. Utilizing HEK293 reporter cell lines, we demonstrate that purified genomic DNA from C. trachomatis can stimulate hTLR9 signaling, albeit at lower levels than gDNA prepared from other Gram-negative bacteria. Interestingly, we found that while C. trachomatis is capable of signaling through hTLR9 and mTLR9 during live infections in non-phagocytic HEK293 reporter cell lines, signaling only occurs at later developmental time points. Chlamydia-specific induction of hTLR9 is blocked when protein synthesis is inhibited prior to the RB-to-EB conversion and exacerbated by the inhibition of lipooligosaccharide biosynthesis. The induction of aberrance / persistence also significantly alters Chlamydia-specific TLR9 signaling. Our observations support the hypothesis that chlamydial gDNA is released at appreciable levels by the bacterium during the conversion between its replicative and infectious forms and during treatment with antibiotics targeting peptidoglycan assembly.

TLR9 Monotherapy in Immune-Competent Mice Suppresses Orthotopic Prostate Tumor Development

Prostate cancer is ranked second in the world for cancer-related deaths in men, highlighting the lack of effective therapies for advanced-stage disease. Toll-like receptors (TLRs) and immunity have a direct role in prostate cancer pathogenesis, but TLR9 has been reported to contribute to both the progression and inhibition of prostate tumorigenesis. To further understand this apparent disparity, we have investigated the effect of TLR9 stimulation on prostate cancer progression in an immune-competent, syngeneic orthotopic mouse model of prostate cancer. Here, we utilized the class B synthetic agonist CPG-1668 to provoke a TLR9-mediated systemic immune response and demonstrate a significant impairment of prostate tumorigenesis. Untreated tumors contained a high abundance of immune-cell infiltrates. However, pharmacological activation of TLR9 resulted in smaller tumors containing significantly fewer M1 macrophages and T cells. TLR9 stimulation of tumor cells in vitro had no effect on cell viability or its downstream transcriptional targets, whereas stimulation in macrophages suppressed cancer cell growth via type I IFN. This suggests that the antitumorigenic effects of CPG-1668 were predominantly mediated by an antitumor immune response. This study demonstrated that systemic TLR9 stimulation negatively regulates prostate cancer tumorigenesis and highlights TLR9 agonists as a useful therapeutic for the treatment of prostate cancer.

A trimeric spike-based COVID-19 vaccine candidate induces broad neutralization against SARS-CoV-2 variants

COVID-19 pandemic caused by SARS-CoV-2 infection has an impact on global public health and social economy. The emerging immune escape of SARS-CoV-2 variants pose great challenges to the development of vaccines based on original strains. The development of second-generation COVID-19 vaccines to induce immune responses with broad-spectrum protective effects is a matter of great urgency. Here, a prefusion-stabilized spike (S) trimer protein based on B.1.351 variant was expressed and prepared with CpG7909/aluminum hydroxide dual adjuvant to investigate the immunogenicity in mice. The results showed that the candidate vaccine could induce a significant receptor binding domain-specific antibody response and a substantial interferon-γ-mediated immune response. Furthermore, the candidate vaccine also elicited robust cross-neutralization against the pseudoviruses of the original strain, Beta variant, Delta variant and Omicron variant. The vaccine strategy of S-trimer protein formulated with CpG7909/aluminum hydroxide dual adjuvant may be considered a means to increase vaccine effectiveness against future variants.

Enhancing TB Vaccine Efficacy: Current Progress on Vaccines, Adjuvants and Immunization Strategies

Tuberculosis (TB) remains a global infectious disease primarily transmitted via respiratory tract infection. Presently, vaccination stands as the primary method for TB prevention, predominantly reliant on the Bacillus Calmette-Guérin (BCG) vaccine. Although it is effective in preventing disseminated diseases in children, its impact on adults is limited. To broaden vaccine protection, efforts are underway to accelerate the development of new TB vaccines. However, challenges arise due to the limited immunogenicity and safety of these vaccines, necessitating adjuvants to bolster their ability to elicit a robust immune response for improved and safer immunization. These adjuvants function by augmenting cellular and humoral immunity against M. tuberculosis antigens via different delivery systems, ultimately enhancing vaccine efficacy. Therefore, this paper reviews and summarizes the current research progress on M. tuberculosis vaccines and their associated adjuvants, aiming to provide a valuable reference for the development of novel TB vaccines and the screening of adjuvants.

A TLR9 agonist synergistically enhances protective immunity induced by an Alum-adjuvanted H7N9 inactivated whole-virion vaccine

Antigen sparing is an important strategy for pandemic vaccine development because of the limitation of worldwide vaccine production during disease outbreaks. However, several clinical studies have demonstrated that the current aluminum (Alum)-adjuvanted influenza vaccines fail to sufficiently enhance immune responses to meet licensing criteria. Here, we used pandemic H7N9 as a model virus to demonstrate that a 10-fold lower amount of vaccine antigen combined with Alum and TLR9 agonist can provide stronger protective effects than using Alum as the sole adjuvant. We found that the Alum/CpG 1018 combination adjuvant could induce more robust virus-specific humoral immune responses, including higher total IgG production, hemagglutination-inhibiting antibody activity, and neutralizing antibody titres, than the Alum-adjuvanted formulation. Moreover, this combination adjuvant shifted the immune response toward a Th1-biased immune response. Importantly, the Alum/CpG 1018-formulated vaccine could confer better protective immunity against H7N9 challenge than that adjuvanted with Alum alone. Notably, the addition of CpG 1018 to the Alum-adjuvanted H7N9 whole-virion vaccine exhibited an antigen-sparing effect without compromising vaccine efficacy. These findings have significant implications for improving Alum-adjuvanted influenza vaccines using the approved adjuvant CpG 1018 for pandemic preparedness.

Expression of codon-optimized PDCoV-RBD protein in baculovirus expression system and immunogenicity evaluation in mice

Porcine deltacoronavirus (PDCoV) is a global epidemic enteropathogenic coronavirus that mainly infects piglets, and causes huge losses to the pig industry. However, there are still no commercial vaccines available for PDCoV prevention and controlment. Receptor-binding domain (RBD) is located at the S1 subunit of PDCoV and is the major target for developing viral inhibitor and vaccine. In this study, the characteristics of the RBD were analyzed by bioinformatic tools, and codon optimization was performed to efficiently express the PDCoV-RBD protein in the insect baculovirus expression system. The purified PDCoV-RBD protein was obtained and fully emulsified with CPG2395 adjuvant, aqueous adjuvant and Al(OH)3 adjuvant, respectively, to develop vaccines. The humoral and cellular immune responses were assessed on mice. The results showed that both the RBD/CPG2395 and RBD/aqueous adjuvant could induce stronger immune responses in mice than that of RBD/Al(OH)3. In addition, the PDCoV challenge infection was conducted and the RBD/CPG2395 could provide better protection against PDCoV in mice. Our study showed that the RBD protein has good antigenicity and can be used as a protective antigen, which provided a basis for the development of the PDCoV vaccine.

Immunogenicity of rabies virus G mRNA formulated with lipid nanoparticles and nucleic acid immunostimulators in mice

Rabies is a preventable zoonotic disease caused by rabies virus (RABV) with high mortality. Messenger RNA (mRNA) vaccines have opened up new avenues for vaccine development and pandemic preparedness with potent scalability, which may overcome the only licensed rabies inactived vaccine' shortcoming of time and cost wasting. Here, we designed an RABV mRNA vaccines expressed RABV G protein and capsulated with lipid nanoparticle (LNP) and different nucleic acid immunostimulator (CPG 1018, CPG 2395 and Poly I:C) and then assessed the immunogenicity and protective capacity in mice. While RABV mRNA capsulated with LNP and CPG 1018 could induce more potent humoral response with highest and durable RABV-G specific IgG titers and virus neutralizing titers, but also induced stronger RABV G-specific cell-mediated immunity (CMI) responses, including the highest proportions of interferon-γ (IFN-γ) and tumor necrosis factor alpha (TNFα)- producing CD4+/CD8 + T cells according to a flow cytometry assay in mice. In addition, in the pre- and post-exposure challenge assays, LNP + CPG 1018 capsulated RABV G mRNA induced 100 % protection against 25 LD50 of RABV infection with highest inhibition efficacy of viral replication with the decreased virus genome detected by qRT-PCR. These results showed that RABV G mRNA capsulated with LNP immune-stimulating nucleic acids CPG 1018 showed promise as a safe and economical rabies vaccine candidate.

Understanding nucleic acid sensing and its therapeutic applications

Nucleic acid sensing is involved in viral infections, immune response-related diseases, and therapeutics. Based on the composition of nucleic acids, nucleic acid sensors are defined as DNA or RNA sensors. Pathogen-associated nucleic acids are recognized by membrane-bound and intracellular receptors, known as pattern recognition receptors (PRRs), which induce innate immune-mediated antiviral responses. PRR activation is tightly regulated to eliminate infections and prevent abnormal or excessive immune responses. Nucleic acid sensing is an essential mechanism in tumor immunotherapy and gene therapies that target cancer and infectious diseases through genetically engineered immune cells or therapeutic nucleic acids. Nucleic acid sensing supports immune cells in priming desirable immune responses during tumor treatment. Recent studies have shown that nucleic acid sensing affects the efficiency of gene therapy by inhibiting translation. Suppression of innate immunity induced by nucleic acid sensing through small-molecule inhibitors, virus-derived proteins, and chemical modifications offers a potential therapeutic strategy. Herein, we review the mechanisms and regulation of nucleic acid sensing, specifically covering recent advances. Furthermore, we summarize and discuss recent research progress regarding the different effects of nucleic acid sensing on therapeutic efficacy. This study provides insights for the application of nucleic acid sensing in therapy.

Toll-like Receptor Ligands Enhance Vaccine Efficacy against a Virulent Newcastle Disease Virus Challenge in Chickens

To enhance the efficacy of the current Newcastle disease vaccine, we have selected potential adjuvants that target well-characterized pattern recognition receptors: the toll-like receptors (TLRs). Imiquimod is a small-molecule activator of TLR7, which is a sensor of dsDNA. ODN-1826 is a mimetic of CpG DNA and ligates TLR21 (a chicken homologue of TLR9 in mammals). The activation of TLRs leads to antiviral responses, including the induction of type I interferons (IFNs). In this study, birds were vaccinated intranasally with a live LaSota strain with or without imiquimod or ODN-1826 (50 µg/bird). Two weeks after vaccination, the birds were challenged with a virulent Newcastle disease virus (chicken/CA/212676/2002). Both adjuvants (imiquimod or ODN-1826) induced higher and more uniform antibody titers among vaccinated birds compared with the live vaccine-alone group. In addition, adjuvanted vaccines demonstrated greater protective efficacy in terms of the reduction in virus-shedding titer and the number of birds shedding the challenge virus at 2 and 4 days post-challenge. A differential expression of antiviral and immune-related genes was observed among groups from tissues (Harderian gland, trachea, cecal tonsil, and spleen) collected 1 and 3 days after treatment. These results demonstrate the potential of TLR-targeted adjuvants as mucosal vaccine enhancers and warrant a further characterization of immune correlates and optimization for efficacy.