DNA from bacteria, but not from vertebrates, induces interferons, activates natural killer cells and inhibits tumor growth

The interactions between CpG oligodeoxynucleotides and Toll-like receptors in Pacific white shrimp Litopenaeus vannamei

CpG oligodeoxynucleotides (ODNs), as a novel type of adjuvant with immunomodulatory effects, are recognized by Toll-like receptors (TLRs) in Litopenaeus vannamei. In the present study, eleven LvTLRs-pCMV recombinants (rLvTLRs) were constructed to investigate the relationships between various CpG ODNs and different LvTLRs in human embryonic kidney 293T (HEK293T) cells, which was further confirmed by bio-layer interferometry (BLI) technique. The results of dual luciferase reporter assay showed that every LvTLR could activate multiple downstream genes, mainly including NF-κB, CREB, ISRE, IL-6-promoter, TNF-α-promoter and Myc, thereby inducing main signaling pathways in shrimps. Most CpG ODNs possessed affinities to more than one LvTLR, while each LvTLR could recognize multiple CpG ODNs, and the widely recognized ligands within CpG ODNs are A-class and B-class. Moreover, BLI analysis showed that CpG 2216, Cpg 2006, CpG 2143 and CpG 21425 exhibited dose-dependent affinity to the expressed TLR protein, which were consistent with the results in HEK293T cells. It suggested that the interactions of CpG ODNs with LvTLRs were indispensable for the immune regulation triggered by CpG ODNs, and these findings would lay foundations for studying the activations of LvTLRs to immune signaling pathways and shedding lights on the immune functions and mechanisms of CpG ODNs.

Immunological Response to Subcutaneous and Intranasal Administration of SARS-CoV-2 Spike Protein in Mice

In novel coronavirus infection (COVID-19), the outbreak of acute lung injury due to trans-airway infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the starting point of severe disease. The COVID-19 pandemic highlights the need for a vaccine that prevents not only the disease but also its infection. Currently, the SARS-CoV-2 vaccine is administered via intramuscular injection and is generally not immunogenic to the mucosa. As a result, current vaccinations fail to reduce viral shedding and transmission and ultimately do not prevent infection. We established a mouse vaccine model in which a single dose of S1 protein and aluminum oxide gel (alum) subcutaneous vaccine was followed by a booster dose of S1 protein and CpG oligodeoxynucleotide intranasal vaccine. The group that received two doses of the intranasal vaccine booster showed a significant increase in IgG and IgA antibody titers against S1 and RBD in serum and BAL, and a significant difference in neutralizing antibody titers, particularly in BAL. One intranasal vaccine booster did not induce sufficient immunity, and the vaccine strategy with two booster intranasal doses produced systemic neutralizing antibodies and mucus-neutralizing antibodies against SARS-CoV-2. It will be an important tool against the emergence of new viruses and the next pandemic.

Antibody Response Following the Intranasal Administration of SARS-CoV-2 Spike Protein-CpG Oligonucleotide Vaccine

The new coronavirus infection causes severe respiratory failure following respiratory tract infection with severe acute respiratory syndrome-related coronavirus (SARS-CoV-2). All currently approved vaccines are administered intramuscularly; however, intranasal administration enhances mucosal immunity, facilitating the production of a less invasive vaccine with fewer adverse events. Herein, a recombinant vaccine combining the SARS-CoV-2 spike protein receptor-binding domain (RBD), or S1 protein, with CpG-deoxyoligonucleotide (ODN) or aluminum hydroxide (alum) adjuvants was administered intranasally or subcutaneously to mice. Serum-specific IgG titers, IgA titers in the alveolar lavage fluid, and neutralizing antibody titers were analyzed. The nasal administration of RBD protein did not increase serum IgG or IgA titers in the alveolar lavage fluid. However, a significant increase in serum IgG was observed in the intranasal group administered with S1 protein with CpG-ODN and the subcutaneous group administered with S1 protein with alum. The IgA and IgG levels increased significantly in the alveolar lavage fluid only after the intranasal administration of the S1 protein with CpG-ODN. The neutralizing antibody titers in serum and bronchoalveolar lavage were significantly higher in the intranasal S1-CpG group than in every other group. Hence, the nasal administration of the S1 protein vaccine with CpG adjuvant might represent an effective vaccine candidate.

Emerging Roles of cGAS-STING Signaling in Mediating Ocular Inflammation

Cyclic GMP-AMP (cGAMP) synthase (cGAS), a sensor of cytosolic DNA, recognizes cytoplasmic nucleic acids to activate the innate immune responses via generation of the second messenger cGAMP and subsequent activation of the stimulator of interferon genes (STINGs). The cGAS-STING signaling has multiple immunologic and physiological functions in all human vital organs. It mediates protective innate immune defense against DNA-containing pathogen infection, confers intrinsic antitumor immunity via detecting tumor-derived DNA, and gives rise to autoimmune and inflammatory diseases upon aberrant activation by cytosolic leakage of self-genomic and mitochondrial DNA. Disruptions in these functions are associated with the pathophysiology of various immunologic and neurodegenerative diseases. Recent evidence indicates important roles of the cGAS-STING signaling in mediating inflammatory responses in ocular inflammatory and inflammation-associated diseases, such as keratitis, diabetic retinopathy, age-related macular degeneration, and uveitis. In this review, we summarize the recently emerging evidence of cGAS-STING signaling in mediating ocular inflammatory responses and affecting pathogenesis of these complex eye diseases. We attempt to provide insightful perspectives on future directions of investigating cGAS-STING signaling in ocular inflammation. Understanding how cGAS-STING signaling is modulated to mediate ocular inflammatory responses would allow future development of novel therapeutic strategies to treat ocular inflammation and autoimmunity.

DNA/Magnetic Nanoparticles Composite to Attenuate Glass Surface Nanotopography for Enhanced Mesenchymal Stem Cell Differentiation

Mesenchymal stem cells (MSCs) have extensive pluripotent potential to differentiate into various cell types, and thus they are an important tool for regenerative medicine and biomedical research. In this work, the differentiation of hTERT-transduced adipose-derived MSCs (hMSCs) into chondrocytes, adipocytes and osteoblasts on substrates with nanotopography generated by magnetic iron oxide nanoparticles (MNPs) and DNA was investigated. Citrate-stabilized MNPs were synthesized by the chemical co-precipitation method and sized around 10 nm according to microscopy studies. It was shown that MNPs@DNA coatings induced chondrogenesis and osteogenesis in hTERT-transduced MSCs. The cells had normal morphology and distribution of actin filaments. An increase in the concentration of magnetic nanoparticles resulted in a higher surface roughness and reduced the adhesion of cells to the substrate. A glass substrate modified with magnetic nanoparticles and DNA induced active chondrogenesis of hTERT-transduced MSC in a twice-diluted differentiation-inducing growth medium, suggesting the possible use of nanostructured MNPs@DNA coatings to obtain differentiated cells at a reduced level of growth factors.

Approaches of the Innate Immune System to Ameliorate Adaptive Immunotherapy for B-Cell Non-Hodgkin Lymphoma in Their Microenvironment

A dominant paradigm being developed in immunotherapy for hematologic malignancies is of adaptive immunotherapy that involves chimeric antigen receptor (CAR) T cells and bispecific T-cell engagers. CAR T-cell therapy has yielded results that surpass those of the existing salvage immunochemotherapy for patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) after first-line immunochemotherapy, while offering a therapeutic option for patients with follicular lymphoma (FL) and mantle cell lymphoma (MCL). However, the role of the innate immune system has been shown to prolong CAR T-cell persistence. Cluster of differentiation (CD) 47-blocking antibodies, which are a promising therapeutic armamentarium for DLBCL, are novel innate immune checkpoint inhibitors that allow macrophages to phagocytose tumor cells. Intratumoral Toll-like receptor 9 agonist CpG oligodeoxynucleotide plays a pivotal role in FL, and vaccination may be required in MCL. Additionally, local stimulator of interferon gene agonists, which induce a systemic anti-lymphoma CD8⁺ T-cell response, and the costimulatory molecule 4-1BB/CD137 or OX40/CD134 agonistic antibodies represent attractive agents for dendritic cell activations, which subsequently, facilitates initiation of productive T-cell priming and NK cells. This review describes the exploitation of approaches that trigger innate immune activation for adaptive immune cells to operate maximally in the tumor microenvironment of these lymphomas.

Sequence Does Not Matter: The Biomedical Applications of DNA-Based Coatings and Cores

Biomedical applications of DNA are diverse but are usually associated with specific recognition of target nucleotide sequences or proteins and with gene delivery for therapeutic or biotechnological purposes. However, other aspects of DNA functionalities, like its nontoxicity, biodegradability, polyelectrolyte nature, stability, thermo-responsivity and charge transfer ability that are rather independent of its sequence, have recently become highly appreciated in material science and biomedicine. Whereas the latest achievements in structural DNA nanotechnology associated with DNA sequence recognition and Watson–Crick base pairing between complementary nucleotides are regularly reviewed, the recent uses of DNA as a raw material in biomedicine have not been summarized. This review paper describes the main biomedical applications of DNA that do not involve any synthesis or extraction of oligo- or polynucleotides with specified sequences. These sequence-independent applications currently include some types of drug delivery systems, biocompatible coatings, fire retardant and antimicrobial coatings and biosensors. The reinforcement of DNA properties by DNA complexation with nanoparticles is also described as a field of further research.

Macrophage Reprogramming and Cancer Therapeutics: Role of iNOS-Derived NO

Nitric oxide and its production by iNOS is an established mechanism critical to tumor promotion or suppression. Macrophages have important roles in immunity, development, and progression of cancer and have a controversial role in pro- and antitumoral effects. The tumor microenvironment consists of tumor-associated macrophages (TAM), among other cell types that influence the fate of the growing tumor. Depending on the microenvironment and various cues, macrophages polarize into a continuum represented by the M1-like pro-inflammatory phenotype or the anti-inflammatory M2-like phenotype; these two are predominant, while there are subsets and intermediates. Manipulating their plasticity through programming or reprogramming of M2-like to M1-like phenotypes presents the opportunity to maximize tumoricidal defenses. The dual role of iNOS-derived NO also influences TAM activity by repolarization to tumoricidal M1-type phenotype. Regulatory pathways and immunomodulation achieve this through miRNA that may inhibit the immunosuppressive tumor microenvironment. This review summarizes the classical physiology of macrophages and polarization, iNOS activities, and evidence towards TAM reprogramming with current information in glioblastoma and melanoma models, and the immunomodulatory and therapeutic options using iNOS or NO-dependent strategies.

Abundant CpG-sequences in human genomes inhibit KIR3DL2-expressing NK cells

Killer Immunoglobulin-like Receptors (KIR) comprise a diverse, highly polymorphic family of cell-surface glycoproteins that are principally expressed by Natural Killer (NK) cells. These innate immune lymphocytes fulfill vital functions in human reproduction and immune responses to viral infection. KIR3DL2 is an inhibitory NK cell receptor that recognizes a common epitope of the HLA-A3 and HLA-A11 class I glycoproteins of the major histocompatibility complex. KIR3DL2 also binds exogenous DNA containing the CpG motif. This interaction causes internalization of the KIR-DNA. Exogenous CpG-DNA typically activates NK cells, but the specificity of KIR3DL2-DNA binding and internalization is unclear. We hypothesized that KIR3DL2 binds exogenous DNA in a sequence-specific manner that differentiates pathogen DNA from self-DNA. In testing this hypothesis, we surveyed octameric CpG-DNA sequences in the human genome, and in reference genomes of all bacteria, fungi, viruses, and parasites, with focus on medically relevant species. Among all pathogens, the nucleotides flanking CpG motifs in the genomes of parasitic worms that infect humans are most divergent from those in the human genome. We cultured KIR3DL2⁺NKL cells with the commonest CpG-DNA sequences in either human or pathogen genomes. DNA uptake was negatively correlated with the most common CpG-DNA sequences in the human genome. These CpG-DNA sequences induced inhibitory signaling in KIR3DL2⁺NKL cells. In contrast, KIR3DL2⁺NKL cells lysed more malignant targets and produced more IFNγ after culture with CpG-DNA sequences prevalent in parasitic worms. By applying functional immunology to evolutionary genomics, we conclude that KIR3DL2 allows NK cells to differentiate self-DNA from pathogen DNA.

Synthetic Hexanucleotides as a Tool to Overcome Excessive Neutrophil Activation Caused by CpG-Containing Oligonucleotides

Mimicking bacterial DNA, synthetic CpG-containing oligodeoxyribonucleotides (CpG-ODNs) have a powerful immunomodulatory potential. Their practical application is mainly associated with the production of vaccines, where they are used as adjuvants, as well as in local antimicrobial therapy. CpG-ODNs act on a wide variety of immune cells, including neutrophilic granulocytes. On the one hand, the stimulatory effect provides both the direct implementation of their antimicrobial and fungicidal mechanisms, and an avalanche-like strengthening of the immune signal due to interaction with other participants in the immune process. On the other hand, hyperactivation of neutrophilic granulocytes can have negative consequences. In particular, the formation of unreasonably high amounts of reactive oxygen species leads to tissue damages and, as a consequence, a spontaneous aggravation and prolongation of the inflammatory process. Under physiological conditions, a large number of DNA fragments are present in inflammation foci: both of microbial and self-tissue origin. We investigated effects of several short modified hexanucleotides on the main indicators of neutrophil activation, as well as their influence on the immunomodulatory activity of known synthetic CpG-ODNs. The results obtained show that short oligonucleotides partially inhibit the prooxidant effect of synthetic CpG-ODNs without significantly affecting the ability of the latter to overcome bacteria-induced pro-survival effects on neutrophilic granulocytes.

CpG-Adjuvanted Hepatitis B Vaccine (HEPLISAV-B®) Update

Introduction: HEPLISAV-B is a hepatitis B vaccine composed of rHBsAg mixed with a synthetic oligonucleotide containing CpG motifs that stimulate innate immunity through TLR9. This vaccine was recently approved by FDA in view of its superior efficacy.Areas covered: Published literature on HEPLISAV-B was critically reviewed. Four randomized controlled trials among 7,056 subjects receiving 2 doses of HEPLISAV-B and 3,214 subjects receiving 3 doses of Engerix-B showed superior seroprotection rate (SPR) (anti-HBs ≥10 mIU/mL) of 90-100%, compared with 71-90% in those receiving Engerix-B. Furthermore, the seroprotection rate was also significantly higher in HEPLISAV-B compared with Engerix-B recipients in persons with traditionally poor vaccine responses such as older adults, diabetics, and those with chronic kidney disease. The safety profiles among 9,871 subjects were similar between HEPLISAV-B and Engerix-B .Expert opinion: HEPLISAV-B, a CpG adjuvant mixed with HBsAg, is more efficacious and produced earlier seroprotection compared to existing vaccines, with a favorable safety profile. The shorter, two-dose regimen, earlier seroprotection, higher adherence, and a higher seroprotection rate, especially in populations with traditionally poor vaccine response, makes this an important therapeutic option in hepatitis B vaccination.

CpG Adjuvant in Allergen-Specific Immunotherapy: Finding the Sweet Spot for the Induction of Immune Tolerance

Prevalence and incidence of IgE-mediated allergic diseases have increased over the past years in developed and developing countries. Allergen-specific immunotherapy (AIT) is currently the only curative treatment available for allergic diseases that has long-term efficacy. Although AIT has been proven successful as an immunomodulatory therapy since its beginnings, it still faces several unmet needs and challenges today. For instance, some patients can experience severe side effects, others are non-responders, and prolonged treatment schedules can lead to lack of patient adherence and therapy discontinuation. A common strategy to improve AIT relies on the use of adjuvants and immune modulators to boost its effects and improve its safety. Among the adjuvants tested for their clinical efficacy, CpG oligodeoxynucleotide (CpG-ODN) was investigated with limited success and without reaching phase III trials for clinical allergy treatment. However, recently discovered immune tolerance-promoting properties of CpG-ODN place this adjuvant again in a prominent position as an immune modulator for the treatment of allergic diseases. Indeed, it has been shown that the CpG-ODN dose and concentration are crucial in promoting immune regulation through the recruitment of pDCs. While low doses induce an inflammatory response, high doses of CpG-ODN trigger a tolerogenic response that can reverse a pre-established allergic milieu. Consistently, CpG-ODN has also been found to stimulate IL-10 producing B cells, so-called B regulatory cells (Bregs). Accordingly, CpG-ODN has shown its capacity to prevent and revert allergic reactions in several animal models showing its potential as both preventive and active treatment for IgE-mediated allergy. In this review, we describe how CpG-ODN-based therapies for allergic diseases, despite having shown limited success in the past, can still be exploited further as an adjuvant or immune modulator in the context of AIT and deserves additional attention. Here, we discuss the past and current knowledge, which highlights CpG-ODN as a potential adjuvant to be reevaluated for the enhancement of AIT when used in appropriate conditions and formulations.

Intestinal Bacteria Encapsulated by Biomaterials Enhance Immunotherapy

The human intestine contains thousands of bacterial species essential for optimal health. Aside from their pathogenic effects, these bacteria have been associated with the efficacy of various treatments of diseases. Due to their impact on many human diseases, intestinal bacteria are receiving increasing research attention, and recent studies on intestinal bacteria and their effects on treatments has yielded valuable results. Particularly, intestinal bacteria can affect responses to numerous forms of immunotherapy, especially cancer therapy. With the development of precision medicine, understanding the factors that influence intestinal bacteria and how they can be regulated to enhance immunotherapy effects will improve the application prospects of intestinal bacteria therapy. Further, biomaterials employed for the convenient and efficient delivery of intestinal bacteria to the body have also become a research hotspot. In this review, we discuss the recent findings on the regulatory role of intestinal bacteria in immunotherapy, focusing on immune cells they regulate. We also summarize biomaterials used for their delivery.

The role of bacterial DNA containing CpG motifs in diseases

Bacterial DNA containing unmethylated CpG motifs can activate immune cells to release proinflammatory cytokines. Here, the role of bacterial DNA containing CpG motifs in diseases with a focus on arthritis is discussed. Our studies demonstrate that the intraarticular injection of bacterial DNA and oligodeoxynucleotides containing CpG motifs (CpG ODN) induced arthritis. The induction of arthritis involves the role of macrophages over other cells such as neutrophils, NK cells, and lymphocytes. TNF-α and TNFRI play an important role in the development of arthritis. NF-κB also plays a critical regulatory role in arthritis. Systemic anti-inflammatory treatment, along with antibiotic therapy, has beneficial effects on the course and the outcome of bacterial arthritis. Thus, future treatment strategies for bacterial arthritis should include attempts to minimizing bacterial growth while blocking the proinflammatory effects of the bacterial DNA. Significant therapeutic efficiency has also been shown by CpG ODN-mediated Th1 immune activation in mouse models of cancer, infectious disease, and allergy/asthma.

Animal Models for the Study of Nucleic Acid Immunity: Novel Tools and New Perspectives

Unresolved inflammation fosters and supports a wide range of human pathologies. There is growing evidence for a role played by cytosolic nucleic acids in initiating and supporting pathological chronic inflammation. In particular, the cGAS-STING pathway has emerged as central to the mounting of nucleic acid-dependent type I interferon responses, leading to the identification of small-molecule modulators of STING that have raised clinical interest. However, several new challenges have emerged, representing potential obstacles to efficient clinical translation. Indeed, the current literature underscores that nucleic acid-induced inflammatory responses are subjected to several layers of regulation, further suggesting complex coordination at the cell-type, tissue or organism level. Untangling the underlying processes is paramount to the identification of specific therapeutic strategies targeting deleterious inflammation. Herein, we present an overview of human pathologies presenting with deregulated interferon levels and with accumulation of cytosolic nucleic acids. We focus on the central role of the STING adaptor protein in these pathologies and discuss how in vivo models have forged our current understanding of nucleic acid immunity. We present our opinion on the advantages and limitations of zebrafish and mice models to highlight their complementarity for the study of inflammatory human pathologies and the development of therapeutics. Finally, we discuss high-throughput screening strategies that generate multi-parametric datasets that allow integrative analysis of heterogeneous information (imaging and omics approaches). These approaches are likely to structure the future of screening strategies for the treatment of human pathologies.

The Central Role and Possible Mechanisms of Bacterial DNAs in Sepsis Development

The pathological roles of bacterial DNA have been documented many decades ago. Bacterial DNAs are different from mammalian DNAs; the latter are heavily methylated. Mammalian cells have sensors such as TLR-9 to sense the DNAs with nonmethylated CpGs and distinguish them from host DNAs with methylated CpGs. Further investigation has identified many other types of DNA sensors distributed in a variety of cellular compartments. These sensors not only sense foreign DNAs, including bacterial and viral DNAs, but also sense damaged DNAs from the host cells. The major downstream signalling pathways includeTLR-9-MyD88-IKKa-IRF-7/NF-κB pathways to increase IFN/proinflammatory cytokine production, STING-TBK1-IRF3 pathway to increase IFN-beta, and AIM2-ASC-caspas-1 pathway to release IL-1beta. The major outcome is to activate host immune response by inducing cytokine production. In this review, we focus on the roles and potential mechanisms of DNA sensors and downstream pathways in sepsis. Although bacterial DNAs play important roles in sepsis development, bacterial DNAs alone are unable to cause severe disease nor lead to death. Priming animals with bacterial DNAs facilitate other pathological factors, such as LPS and other virulent factors, to induce severe disease and lethality. We also discuss compartmental distribution of DNA sensors and pathological significance as well as the transport of extracellular DNAs into cells. Understanding the roles of DNA sensors and signal pathways will pave the way for novel therapeutic strategies in many diseases, particularly in sepsis.

SARS-CoV-2 will constantly sweep its tracks: a vaccine containing CpG motifs in 'lasso' for the multi-faced virus

During the current COVID-19 pandemic, the global ratio between the dead and the survivors is approximately 1 to 10, which has put humanity on high alert and provided strong motivation for the intensive search for vaccines and drugs. It is already clear that if we follow the most likely scenario, which is similar to that used to create seasonal influenza vaccines, then we will need to develop improved vaccine formulas every year to control the spread of the new, highly mutable coronavirus SARS-CoV-2. In this article, using well-known RNA viruses (HIV, influenza viruses, HCV) as examples, we consider the main successes and failures in creating primarily highly effective vaccines. The experience accumulated dealing with the biology of zoonotic RNA viruses suggests that the fight against COVID-19 will be difficult and lengthy. The most effective vaccines against SARS-CoV-2 will be those able to form highly effective memory cells for both humoral (memory B cells) and cellular (cross-reactive antiviral memory T cells) immunity. Unfortunately, RNA viruses constantly sweep their tracks and perhaps one of the most promising solutions in the fight against the COVID-19 pandemic is the creation of 'universal' vaccines based on conservative SARS-CoV-2 genome sequences (antigen-presenting) and unmethylated CpG dinucleotides (adjuvant) in the composition of the phosphorothioate backbone of single-stranded DNA oligonucleotides (ODN), which can be effective for long periods of use. Here, we propose a SARS-CoV-2 vaccine based on a lasso-like phosphorothioate oligonucleotide construction containing CpG motifs and the antigen-presenting unique ACG-containing genome sequence of SARS-CoV-2. We found that CpG dinucleotides are the most rare dinucleotides in the genomes of SARS-CoV-2 and other known human coronaviruses, and hypothesized that their higher frequency could be responsible for the unwanted increased lethality to the host, causing a ‘cytokine storm’ in people who overexpress cytokines through the activation of specific Toll-like receptors in a manner similar to TLR9-CpG ODN interactions. Interestingly, the virus strains sequenced in China (Wuhan) in February 2020 contained on average one CpG dinucleotide more in their genome than the later strains from the USA (New York) sequenced in May 2020. Obviously, during the first steps of the microevolution of SARS-CoV-2 in the human population, natural selection tends to select viral genomes containing fewer CpG motifs that do not trigger a strong innate immune response, so the infected person has moderate symptoms and spreads SARS-CoV-2 more readily. However, in our opinion, unmethylated CpG dinucleotides are also capable of preparing the host immune system for the coronavirus infection and should be present in SARS-CoV-2 vaccines as strong adjuvants.

Progress in the Use of Antisense Oligonucleotides for Vaccine Improvement

: Antisense oligonucleotides (ASOs) are synthetically prepared short single-stranded deoxynucleotide sequences that have been validated as therapeutic agents and as a valuable tool in molecular driving biology. ASOs can block the expression of specific target genes via complementary hybridization to mRNA. Due to their high specificity and well-known mechanism of action, there has been a growing interest in using them for improving vaccine efficacy. Several studies have shown that ASOs can improve the efficacy of vaccines either by inducing antigen modification such as enhanced expression of immunogenic molecules or by targeting certain components of the host immune system to achieve the desired immune response. However, despite their extended use, some problems such as insufficient stability and low cellular delivery have not been sufficiently resolved to achieve effective and safe ASO-based vaccines. In this review, we analyze the molecular bases and the research that has been conducted to demonstrate the potential use of ASOs in vaccines.

Intrapulmonary Delivery of CpG-ODN Microdroplets Provides Protection Against Escherichia coli Septicemia in Neonatal Broiler Chickens

Synthetic oligodeoxynucleotides (ODN) containing unmethylated cytosine phosphodiester guanine (CpG) motifs (CpG-ODN) are effective immunostimulatory agents against a variety of viral, bacterial, and protozoan diseases in different animals including poultry. We have recently demonstrated that in ovo injection of CpG-ODN confers protection in neonatal chickens against bacterial septicemias. The objective of this study was to investigate the effectiveness of needle-free intrapulmonary (IPL) delivery of CpG-ODN microdroplets against Escherichia coli infection in neonatal chicks. In the present study, we used 880 chicks in total keeping 40 chicks per group. Chicks were delivered CpG-ODN or saline by IPL at the day 1 of hatch. Three days later, chicks were challenged with two doses (1 × 10⁴ CFU, n = 20 or 1 × 10⁵ CFU, n = 20) of E. coli. Chicks treated with CpG-ODN by the IPL route had significantly lower clinical signs and bacterial load compared to the group treated with saline ( P < 0.05). CpG-ODN-treated groups were significantly protected against E. coli septicemia. We observed dose- and exposure time-dependent immunoprotective effects of IPL CpG-ODN in chicks. We found that IPL delivery of CpG-ODN can induce protective immunity as early as 6 hr that remains effective at least until day 5 post-treatment. Moreover, there were no adverse effects of IPL delivery of CpG-ODN on growth or mortality up to 42 days of age. Based on these findings, it can be suggested that CpG-ODN delivery by IPL route can be a promising alternative to antibiotics for inducing protective immunity in chicks during the critical first week of neonatal life.

Characterization of genomic DNA of lactic acid bacteria for activation of plasmacytoid dendritic cells

Background

Lactococcus lactis strain Plasma (LC-Plasma) possesses strong stimulatory activity for plasmacytoid dendritic cells (pDCs) via the TLR9-Myd88 pathway. To reveal the effective lactic acid bacteria (LAB) genome structure for pDCs stimulatory activity, we performed in vitro screening, using randomly selected 200 bp DNA fragments from the LC-Plasma genome.

Results

We found that the CpG motif copy number in the fragments was positively and significantly correlated with pDCs stimulatory activity (R = 0.491, p < 0.01). However, the determination coefficient (R²) was 0.24, which means other factors affecte activity. We found that the G + C contents of the fragment showed a significant negative correlation with activity (R = − 0.474, p < 0.01). The correlation between pDCs stimulatory activity and the copy number of CpG motifs was greatly increased when DNA fragments were stratified by G + C contents.

We also performed bioinformatics analysis and a screening of LAB strains with high pDCs stimulatory activity. Species with a high copy number of CpG motifs in the low-G + C region of their genomes had higher probability of inducing high-pDCs stimulatory activity. L. lactis subsp. lactis, Leuconostoc mesenteroides, and Pediococcus pentosaceus were three typical examples of LAB that had high pDCs stimulatory activity.

Conclusions

Our data suggested that the G + C content of DNA is one of the critical factors for pDCs stimulatory activity by DNA fragments. Furthermore, we found that the copy number in the low-G + C regions strongly affected the pDCs stimulatory activity of whole cells of LAB strains. These results should be useful for the design of new DNA fragments containing CpG motifs. This study also demonstrated an in silico screening method for identifying bacterial species that are able to activate pDCs.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1458-y) contains supplementary material, which is available to authorized users.

The protective effects of nasal PcrV-CpG oligonucleotide vaccination against Pseudomonas aeruginosa pneumonia

An effective vaccine against Pseudomonas aeruginosa would be hugely beneficial to people who are susceptible to the serious infections it can cause. Vaccination against PcrV of the P. aeruginosa type III secretion system is a potential prophylactic strategy for improving the incidence and prognosis of P. aeruginosa pneumonia. Here, the effect of nasal PcrV adjuvanted with CpG oligodeoxynucleotide (CpG) was compared with a nasal PcrV/aluminum hydroxide gel (alum) vaccine. Seven groups of mice were vaccinated intranasally with one of the following: 1, PcrV-CpG; 2, PcrV-alum; 3, PcrV alone; 4, CpG alone; 5, alum alone; 6 and 7, saline control. Fifty days after the first immunization, anti-PcrV IgG, IgA and IgG isotype titers were measured; significant increases in these titers were detected only in the PcrV-CpG vaccinated mice. The vaccinated mice were then intratracheally infected with a lethal dose of P. aeruginosa and their body temperatures and survival monitored for 24 hr, edema, bacteria, myeloperoxidase activity and lung histology also being evaluated at 24 hr post-infection. It was found that 73% of the PcrV-CpG-vaccinated mice survived, whereas fewer than 30% of the mice vaccinated with PcrV-alum or adjuvant alone survived. Lung edema and other inflammation-related variables were less severe in the PcrV-CpG group. The significant increase in PcrV-specific IgA titers detected following PcrV-CpG vaccination is probably a component of the disease protection mechanism. Overall, our data show that intranasal PcrV-CpG vaccination has potential efficacy for clinical application against P. aeruginosa pneumonia.

BCG-induced cytokine release in bladder cancer cells is regulated by Ca2+ signaling

Bacillus Calmette-Guérin (BCG) is widely used in the clinic to effectively treat superficial urinary bladder cancer. However, a significant proportion of patients who fail to respond to BCG risk cystectomy or death. Though more than 3 million cancer treatments with BCG occur annually, surprisingly little is known about the initial signaling cascades activated by BCG. Here, we report that BCG induces a rapid intracellular Ca²⁺ (calcium ion) signal in bladder cancer cells that is essential for activating the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and for synthesizing and secreting proinflammatory cytokines, including interleukin 8 (IL-8). A similar Ca²⁺ response was observed when cells were exposed to the supernatant of BCG. Studying cellular molecular mechanisms involved in the BCG signaling event, we found pivotal roles for phospholipase C and the Toll-like receptor 4. Further assessment revealed that this signaling pathway induces synthesis of IL-8, whereas exocytosis appeared to be controlled by global Ca²⁺ signaling. These results shed new light on the molecular mechanisms underlying BCG treatment of bladder cancer, which can help in improving therapeutic efficacy and reducing adverse side effects.

Vaccine adjuvants CpG (oligodeoxynucleotides ODNs), MPL (3-O-deacylated monophosphoryl lipid A) and naloxone-enhanced Th1 immune response to the Plasmodium vivax recombinant thrombospondin-related adhesive protein (TRAP) in mice

Despite considerable efforts toward vaccine development over decades, there is no available effective vaccine against Plasmodium vivax. Thrombospondin-related adhesive protein of P. vivax (PvTRAP) is essential for sporozoite motility and invasions into mosquito's salivary gland and vertebrate's hepatocyte; hence, it is a promising target for pre-erythrocytic vaccine. In the current investigation, the role of antibodies and cellular immune responses induced by purified recombinant PvTRAP (rPvTRAP) delivered in three adjuvants, naloxone (NLX), CpG oligodeoxynucleotides ODN1826 (CpG-ODN), and 3-O-deacylated monophosphoryl lipid A (MPL), alone and in combination was evaluated in immunized C57BL/6 mice. The highest level and the avidity of anti-PvTRAP IgG (mean OD_490nm 2.55), IgG2b (mean OD_490nm 1.68), and IgG2c (mean OD_490nm 1.466) were identified in the group received rPvTRA/NLX-MPL-CpG. This group also presented the highest IgG2c/IgG1 (2.58) and IgG2b/IgG1 (2.95) ratio when compared to all other groups, and among the adjuvant groups, the lowest IgG2c/IgG1 (1.86) and IgG2b/IgG1 (2.25) ratio was observed in mice receiving rPvTRAP/NLX. Mice receiving rPvTRAP/adjuvants induced significantly the higher levels of interferon gamma (IFN-γ), low level of detectable IL-10, and no detectable IL-4 production. The present result revealed that PvTRAP is immunogenic and its administration with CPG, MPL, and NLX in C57BL/6 mice induced Th1 immune response. Besides, the rPvTRAP delivery in the mixed formulation of those adjuvants had more potential to increase the level, avidity, and persistence of anti-TRAP antibodies. However, it warrants further assessment to test the blocking activity of the produced antibodies in immunized mice with different adjuvant formulations.

Utilizing DNA for functionalization of biomaterial surfaces

DNA sequences are widely used for gene transfer into cells including a number of substrate surface-based supporting systems, but due to its singular structure property profile, DNA also offers multiple options for noncanonical applications. The special case of using DNA and oligodeoxyribonucleotide (ODN) structures for surface functionalization of biomedical implants is summarized here with the major focus on (a) immobilization or anchoring of nucleic acid structures on substrate surfaces, (b) incorporation of biologically active molecules (BAM) into such systems, and (c) biological characteristics of the resulting surfaces in vitro and in vivo. Sterilizations issues, important for potential clinical applications, are also considered.

Suppression of Allergic Response by CpG Motif Oligodeoxynucleotide–House-Dust Mite Conjugate in Animal Model of Allergic Rhinitis

Background

Although there have been many therapeutic options for allergic disease, the true allergen desensitization remains a challenging goal. The classic immunotherapy has a limited efficacy, is inconvenient, and has a risk of anaphylaxis. Recent reports revealed that immunostimulatory DNA sequences (ISS-oligdeoxynucleotide [ODN], CpG motif) act as a strong Th1 response–inducing adjuvants and that DNA-based vaccination might be an effective therapeutic option. In this study, we investigate whether ISS-ODN/Dermatophagoides farinae (Der f) conjugate has antiallergic effects in the allergic rhinitis mouse model, sensitive to house-dust mites. Der f is the most common allergen-inducing allergic rhinitis in Korea.

Methods

C57BL/6 mice were sensitized with crude extract of Der f. After injection of ISS-ODN or ISS-ODN/Der f conjugate, several parameters of allergic response were evaluated.

Results

Scratching and sneezing symptoms and eosinophilic infiltration into nasal mucosa were suppressed by injection with ISS-ODN only and ISS-ODN/Der f conjugate. Interleukin-5 level was decreased and interferon γ level was increased in nasal lavage fluid by injection of ISS-ODN/Der f conjugate. Der f–specific immunoglobulin E was decreased by injection of ISS-ODN or Der f /ISS-ODN conjugate; however, these were not statistically significant. Transforming growth factor β1 secreted by cultured splenocyte was increased significantly in ISS-ODN/Der f conjugate group.

Conclusion

These results suggest ISS-ODN/Der f conjugate induces an antiallergic effect and induces an increase in transforming growth factor β1 level in the allergic rhinitis model using Der f allergen. Allergic response developed by Der f allergen could be more effectively reduced by injection with ISS-ODN/Der f conjugate than by injection with ISS-ODN only.

Nucleic Acid Immunity

Organisms throughout biology need to maintain the integrity of their genome. From bacteria to vertebrates, life has established sophisticated mechanisms to detect and eliminate foreign genetic material or to restrict its function and replication. Tremendous progress has been made in the understanding of these mechanisms which keep foreign or unwanted nucleic acids from viruses or phages in check. Mechanisms reach from restriction-modification systems and CRISPR/Cas in bacteria and archaea to RNA interference and immune sensing of nucleic acids, altogether integral parts of a system which is now appreciated as nucleic acid immunity. With inherited receptors and acquired sequence information, nucleic acid immunity comprises innate and adaptive components. Effector functions include diverse nuclease systems, intrinsic activities to directly restrict the function of foreign nucleic acids (e.g., PKR, ADAR1, IFIT1), and extrinsic pathways to alert the immune system and to elicit cytotoxic immune responses. These effects act in concert to restrict viral replication and to eliminate virus-infected cells. The principles of nucleic acid immunity are highly relevant for human disease. Besides its essential contribution to antiviral defense and restriction of endogenous retroelements, dysregulation of nucleic acid immunity can also lead to erroneous detection and response to self nucleic acids then causing sterile inflammation and autoimmunity. Even mechanisms of nucleic acid immunity which are not established in vertebrates are relevant for human disease when they are present in pathogens such as bacteria, parasites, or helminths or in pathogen-transmitting organisms such as insects. This review aims to provide an overview of the diverse mechanisms of nucleic acid immunity which mostly have been looked at separately in the past and to integrate them under the framework nucleic acid immunity as a basic principle of life, the understanding of which has great potential to advance medicine.

CpG Oligodeoxynucleotide Inhibits Cockroach-Induced Asthma via Induction of IFN-γ⁺ Th1 Cells or Foxp3⁺ Regulatory T Cells in the Lung

Purpose

CpG oligodeoxynucleotide (CpG-ODN), a TLR9 agonist, activates innate immunity and induces Th1 response. Although the immune modulatory effect of CpG-ODN has been extensively studied, its function in cockroach extract-induced allergic asthma has not been studied. Here, we investigated the inhibitory function of CpG-ODN in cockroach extract-induced asthma in mice with different treatment schemes.

Methods

Scheme 1: BALB/C mice were intra-nasally co-administered by cockroach extract and CpG-ODN twice a week for 3 weeks; Scheme 2: The mice were intra-nasally pre-treated with CpG-ODN at day 0 and cockroach allergen challenge was performed from day 3 as in scheme 1. Scheme 3: Cockroach allergen challenge was performed as in scheme 1 and CpG-ODN was post-treated at day 21. Then, BAL cell count, flow cytometric analysis of alveolar macrophages, regulatory T cells, and lung tissue histology, Th1 and Th2 cytokines, serum IgE, cockroach specific IgE, IgG1/IgG2a ratio, and airway hyper-responsiveness were evaluated.

Results

Mice with repeated intra-nasal exposure to CpG-ODN showed a dramatic decrease in eosinophilic inflammation, goblet cell hyperplasia, and airway hyper-responsiveness with reduction of IL-13, IL-5, and serum IgE, cockroach specific IgE and IgG1/IgG2a ratio. This inhibitory function might be related to the up-regulation of IL-10 and CD4⁺Foxp3⁺ regulatory T cells in the lung. Interestingly, one-time challenge of CpG-ODN either prior or posterior to cockroach extract exposure could modulate airway inflammation and hyper-responsiveness via increase of Th1 response.

Conclusions

Collectively, our data suggest that CpG-ODN treatment modulates Th2 inflammation in the lung by induction of regulatory T cells or Th1 response in a cockroach-induced asthma model.

Structure, mechanism and therapeutic utility of immunosuppressive oligonucleotides

Synthetic oligodeoxynucleotides that can down-regulate cellular elements of the immune system have been developed and are being widely studied in preclinical models. These agents vary in sequence, mechanism of action, and cellular target(s) but share the ability to suppress a plethora of inflammatory responses. This work reviews the types of immunosuppressive oligodeoxynucleotide (Sup ODN) and compares their therapeutic activity against diseases characterized by pathologic levels of immune stimulation ranging from autoimmunity to septic shock to cancer (see graphical abstract). The mechanism(s) underlying the efficacy of Sup ODN and the influence size, sequence and nucleotide backbone on function are considered.

CpG oligodeoxynucleotides as mucosal adjuvants

Bacterial DNA comprising palindromic sequences and containing unmethylated CpG is recognized by toll-like receptor 9 of plasmacytoid dendritic cells (pDCs) and induces the production of interferon-α and chemokines, leading to the activation of a Th1 immune response. Therefore, synthetic equivalents of bacterial DNA (CpG oligodeoxynucleotides) have been developed for clinical applications. They are usually phosphorothioated for in vivo use; this approach also leads to adverse effects as reported in mouse models.Mucosal vaccines that induce both mucosal and systemic immunity received substantial attention in recent years. For their development, phosphodiester-linked oligodeoxynucleotides, including the sequence of a palindromic CpG DNA may be advantageous as adjuvants because their target pDCs are present right there, in the mucosa of the vaccination site. In addition, the probability of adverse effects is believed to be low. Here, we review the discovery of such CpG oligodeoxynucleotides and their possible use as mucosal adjuvants.

Heparan sulfate mimetic PG545-mediated antilymphoma effects require TLR9-dependent NK cell activation

Heparan sulfate (HS) is an essential component of the extracellular matrix (ECM), which serves as a barrier to tumor invasion and metastasis. Heparanase promotes tumor growth by cleaving HS chains of proteoglycan and releasing HS-bound angiogenic growth factors and facilitates tumor invasion and metastasis by degrading the ECM. HS mimetics, such as PG545, have been developed as antitumor agents and are designed to suppress angiogenesis and metastasis by inhibiting heparanase and competing for the HS-binding domain of angiogenic growth factors. However, how PG545 exerts its antitumor effect remains incompletely defined. Here, using murine models of lymphoma, we determined that the antitumor effects of PG545 are critically dependent on NK cell activation and that NK cell activation by PG545 requires TLR9. We demonstrate that PG545 does not activate TLR9 directly but instead enhances TLR9 activation through the elevation of the TLR9 ligand CpG in DCs. Specifically, PG545 treatment resulted in CpG accumulation in the lysosomal compartment of DCs, leading to enhanced production of IL-12, which is essential for PG545-mediated NK cell activation. Overall, these results reveal that PG545 activates NK cells and that this activation is critical for the antitumor effect of PG545. Moreover, our findings may have important implications for improving NK cell-based antitumor therapies.

Protection of Neonatal Broiler Chickens Following in ovo Delivery of Oligodeoxynucleotides Containing CpG Motifs (CpG-ODN) Formulated with Carbon Nanotubes or Liposomes

Unformulated oligodeoxynucleotides (ODN) containing CpG motifs (CpG-ODN) have been shown to stimulate the innate immune system against a variety of bacterial, viral, and protozoan infections in a variety of vertebrate species. We have previously shown that in ovo delivery of unformulated CpG-ODN was able to significantly protect neonatal broiler chickens against Escherichia coli or Salmonella Typhimurium infections. The objectives of this study were to examine the safety and immunoprotective effects of CpG-ODN formulated with 2 types of carbon nanotubes (CNTs) or 2 types of lipid-surfactant (LSC) delivery systems in neonatal broilers against E. coli septicemia. Embryonated eggs, which had been incubated for 18 days, received either 50 μg of CNT-CpG-ODN, 50 μg of LSC-CpG-ODN, 50 μg of unformulated CpG-ODN, or saline. Four days after exposure to CpG-ODN (day 1 posthatch), 1 x 10(4) or 1 x 10(5) colony-forming units of a virulent strain of E. coli isolated from a turkey with septicemia were inoculated subcutaneously in the neck. Clinical signs, pathology, bacterial isolations from the air sacs, and mortality were observed for 8 days following challenge with E. coli. Bacterial isolations and pathologic observations were conducted immediately after birds were dead or euthanatized. The survival rate of birds in groups receiving saline following E. coli infection was 20% to 30%. In contrast, birds receiving CpG-ODN formulations had a significantly higher survival rate of 60% to 80% (P < 0.01). Bacterial loads and clinical scores were significantly lower (P < 0.05) in groups treated with CNT- or LSC-CpG-ODN compared to the groups receiving CpG-ODN or saline. Moreover, there is no evidence of any adverse effects of these formulations in any organs or in growth rates of birds until 42 days of age. This is the first time that CpG-ODN formulated with CNT and LSC have been demonstrated to have an immunomodulatory effect against an E. coli infection in neonatal broiler chickens following in ovo delivery.

Covalent modification of cell surfaces with TLR agonists improves & directs immune stimulation

We present a primary example of a cell surface modified with a synergistic combination of agonists to tune immune stimulation. A model cell line, Lewis Lung Carcinoma, was covalently modified with CpG-oligonucleotides and lipoteichoic acid, both Toll-like receptor (TLR) agonists. The immune-stimulating constructs provided greater stimulation of NF-κB in a model cell line and bone marrow-derived dendritic cells than the components unconjugated in solution.

Immunotherapeutic potential of CpG oligodeoxynucleotides in veterinary species

Innate immunity plays a critical role in host defense against infectious diseases by discriminating between self and infectious non-self. The recognition of infectious non-self involves germ-line encoded pattern recognition receptors (PRRs) that recognize pathogen-associated molecular patterns (PAMPs). The PAMPs are the components of pathogenic microbes which include not only the cell wall constituents but also the unmethylated 2'-deoxy-ribo-cytosine-phosphate-guanosine (CpG) motifs. These CpG motifs present within bacterial and viral DNA are recognized by toll-like receptor 9 (TLR9), and signaling by this receptor triggers a proinflammatory cytokine response which, in turn, influences both innate and adaptive immune responses. The activation of TLR9 with synthetic CpG oligodeoxynucleotides (ODNs) induces powerful Th1-like immune responses. It has been shown to provide protection against infectious diseases, allergy and cancer in laboratory animal models and some domestic animal species. With better understanding of the basic biology and immune mechanisms, it would be possible to exploit the potential of CpG motifs for animal welfare. The research developments in the area of CpG and TLR9 and the potential applications in animal health have been reviewed in this article.

Reactivation of immune responses against Mycobacterium tuberculosis by boosting with the CpG oligomer in aged mice primarily vaccinated with Mycobacterium bovis BCG

BACKGROUND

Mycobacterium bovis bacillus Calmette Guérin (BCG) vaccine, which has been inoculated to more than one billion people world-wide, has significant effect in preventing tuberculous meningitis and miliary tuberculosis (TB) in neonate and early childhood. However, BCG fails to adequately protect against pulmonary TB and reactivation of latent infections in adults. To overcome this problem, adequate booster is urgently desired in adult who received prior BCG vaccination, and appropriate animal models that substitute human cases would be highly valuable for further experimentation.

FINDINGS

The booster effect of the synthesized CpG oligomer (Oligo-B) on aged mice which had been primarily vaccinated with BCG at the age of 4-week old. The specific Th1 type reaction, production of interferon-γ, in response to TB antigens, purified protein derivatives (PPD) and protection against challenge with Mycobacterium tuberculosis (MTB) H37Rv decreased with increasing age and were not observed in 89-week old mice. In order to rejuvenate the Th1 type response against PPD and protection activity against MTB infection, Oligo-B, which is known to augment Th1 responses, was administered as a booster to 81-90-week old mice (late 50's in human equivalent) vaccinated with BCG at 4-week old. The boosting with Oligo-B increased the number of CD4+ CD44high CD62Lhigh, central memory type T cell. Furthermore, the Oligo-B boosting rejuvenated the ability of mice to protect against infection with MTB H37Rv.

CONCLUSIONS

Th1-adjuvant CpG oligo DNA, such as Oligo-B, may be a promising booster when coupled with BCG priming.

Early development of the Toll-like receptor 9 agonist, PF-3512676, for the treatment of patients with advanced cancers

BACKGROUND

Unmethylated oligodeoxynucleotides (ODNs) with cytosine-phosphate-guanine (CpG) motifs can potently activate the immune system through Toll-like receptor (TLR) 9. PF-3512676 is a synthetic CpG ODN that induces strong Th1-type immune responses through TLR9 and is now in clinical development.

OBJECTIVE

To review discovery and development of synthetic CpG ODNs and their effects on immune cells and to relate preclinical and early clinical development of PF-3512676.

METHODS

A literature search was performed on databases available through the National Library of Medicine (PubMed), the European Society of Medical Oncology and the American Society of Clinical Oncology.

RESULTS/CONCLUSIONS

Unmethylated CpG motifs were identified as the element of bacillus Calmette-Guérin responsible for immunostimulatory activity. Preclinical studies identified the mechanism of action (i.e., TLR9) and an optimal human sequence for antitumor activity. On the basis of preclinical studies, PF-3512676, a B-class CpG ODN, was selected for further clinical development. Phase I/II clinical trials have shown PF-3512676 to be well tolerated and to have antitumor activity as a single agent in patients with several types of advanced cancer, and to show promise as a vaccine adjuvant.

Oligonucleotide and Parylene Surface Coating of Polystyrene and ePTFE for Improved Endothelial Cell Attachment and Hemocompatibility

In vivo self-endothelialization by endothelial cell adhesion on cardiovascular implants is highly desirable. DNA-oligonucleotides are an intriguing coating material with nonimmunogenic characteristics and the feasibility of easy and rapid chemical fabrication. The objective of this study was the creation of cell adhesive DNA-oligonucleotide coatings on vascular implant surfaces. DNA-oligonucleotides immobilized by adsorption on parylene (poly(monoaminomethyl-para-xylene)) coated polystyrene and ePTFE were resistant to high shear stress (9.5 N/m²) and human blood serum for up to 96 h. Adhesion of murine endothelial progenitor cells, HUVECs and endothelial cells from human adult saphenous veins as well as viability over a period of 14 days of HUVECs on oligonucleotide coated samples under dynamic culture conditions was significantly enhanced (P < 0.05). Oligonucleotide-coated surfaces revealed low thrombogenicity and excellent hemocompatibility after incubation with human blood. These properties suggest the suitability of immobilization of DNA-oligonucleotides for biofunctionalization of blood vessel substitutes for improved in vivo endothelialization.

Comparison of safety and immunogenicity of two doses of investigational hepatitis B virus surface antigen co-administered with an immunostimulatory phosphorothioate oligodeoxyribonucleotide and three doses of a licensed hepatitis B vaccine in healthy adults 18-55 years of age

BACKGROUND

The currently licensed aluminum-hydroxide-adjuvanted hepatitis B vaccines require three doses over a 6-month period to achieve high rates of protection in adults. We compared tolerability and immunogenicity of two doses of an investigational hepatitis B vaccine using hepatitis B surface antigen adjuvanted with an immunostimulatory phosphorothioate oligodeoxyribonucleotide (HBV-ISS) to three doses of a licensed alum-adjuvanted vaccine (HBV-Eng).

METHODS

In this randomized, observer-blind study, healthy adults received two doses of HBV-ISS at 0 and 4 weeks or three doses of HBV-Eng at 0, 4, and 24 weeks. The primary immunogenicity endpoint was the seroprotection rate (antibody ≥ 10 mIU/mL) 8 weeks after the second dose of HBV-ISS compared to 4 weeks after the third dose of HBV-Eng.

RESULTS

A total of 2415 participants were randomized in a ratio of 3:1 to HBV-ISS (n=1809) and HBV-Eng (n=606). The percentage of subjects exhibiting a seroprotective immune response at the primary time point was significantly higher (95.1%) for HBV-ISS than for HBV-Eng (81.1%). Superiority of the seroprotective rates for HBV-ISS was demonstrated at all time points measured. Geometric mean concentrations were also significantly higher in the HBV-ISS group at all time points measured except at week 28 (24 weeks post-second dose of HBV-ISS and 4 weeks post-third dose HBV-ISS) at which time the antibody concentrations were similar. Both vaccines were welltolerated although injection-site reactions were reported at a higher rate in HBV-ISS recipients.

CONCLUSIONS

A short, two-dose regimen of HBV-ISS induced a superior antibody response than a three-dose regimen of a licensed hepatitis B vaccine and was well tolerated.

Identification of cytosine-phosphorothioate-guanine oligodeoxynucleotide sequences that induce interferon-γ production in feline immune cells

Unmethylated CpG-ODN are known to enhance Th1-type immune response. However, optimal sequences of CpG-ODN for activating Th1-type immune cells vary among species. It is necessary to identify the effective CpG-ODN sequences in each species. In the present study, in order to identify the sequences of CpG-ODN that produce fIFN-γ in cats, 14 kinds of ODN were synthesized and examined regarding their ability to induce fIFN-γ in feline PBMC and splenocytes. It was shown that some CpG-ODN significantly induced fIFN-γ production in splenocytes, but not in PBMC. We found that three kinds of CpG-ODN (no. 2, 5'-ggTGCATCGATGCAGggggG-3'; no. 5, 5'-ggTGCGTCGACGCAGggggG-3'; no. 10, 5'-ggTGCTACGTAGCAGggggG-3') specifically and significantly induced fIFN-γ production in feline splenocytes. The reverse sequences, GpC-ODN, do not cause significant fIFN-γ production. The fIFN-γ production inductivity of a mixture of CpG-ODN nos. 2, 5 and 10 was higher than those of individual CpG-ODN. When the CpG-ODN mixture was encapsulated in an MCL and administrated to cats, the number of fIFN-γ(+) cells in PBMC significantly increased. CpG-ODN nos. 2, 5 and 10 should be useful to elicit a Th1-type immune response as a vaccine adjuvant in cats.

An in silico DNA vaccine against Listeria monocytogenes

Listeria monocytogenes causes listeriosis with mortality rate >20%. Listeriolysin-O (LLO), a pore-forming hemolysin, belongs to the family of cholesterol-dependent toxins (CDTX) and plays roles in the pathogenicity. In this study bioinformatic analyses were carried out on LLO sequence as a major immunodominant listerial antigen toward designing a DNA vaccine stimulating cytotoxic T-lymphocytes (CTLs). Mouse and human constructs were designed based on predicted T cell epitopes and MHC class I binders, which were then tandemly fused together. LLO-derived construct codons and a variety of critical gene expression efficiency parameters were optimized. Post-translational modifications such as glycosylation, phosphorylation were analysed. The constructs corresponded to LLO sequences of L. monocytogenes in BLAST search. Neither human nor mouse construct was allergen. Secretory pathway was location of the human construct that enhances immune induction and contribute to the efficacy of the vaccine candidate. mRNAs from optimized DNA sequences of both human and mouse constructs are more stable than the native and are suitable for initiation of translation. The constructs contain several sites for phosphorylation that could improve its degradation and subsequent entry into the MHC class I pathway. Addition of GPI anchor, myristoylation and ubiquitin signals or proline (P), glutamic acid (E), serine (S), threonine (T) (PEST)-like motifs at the N-terminal of constructs increase efficacy of the DNA vaccine. Close physical contact between the favorable immunogen and the suitable CpG oligodeoxynucleotides (CpG ODN) promotes immune response. Vectors for checking the expression of constructs in mammalian cells and for harboring the foreign genes as DNA vaccine are suggested.

Delivery of calf thymus DNA to tumor by folate receptor targeted cationic liposomes

Calf thymus DNA (ctDNA) has been shown to stimulate macrophages to produce cytokines both in vitro and in vivo when complexed with cationic liposomes. In addition, direct cytotoxicity of ctDNA has been found in tissue culture and in mice. In this study, ctDNA and folate receptor targeted cationic liposome complexes (ctDNA-F-CLs) were prepared and evaluated in FR (+) tumors. In addition, the underlying mechanism for the anti-cancer activity of ctDNA-F-CLs was investigated. Selective uptake of ctDNA-F-CLs was observed in FR (+) KB and L1210JF cells using flow cytometry. In RAW264.7 cells and DBA/2 mice, ctDNA-F-CLs and ctDNA-N-CLs significantly induced TNF-α and IL-6 production compared to free ctDNA. However, no significant difference in cytokine production was observed between ctDNA-N-CLs and ctDNA-F-CLs. In tumor bearing DBA/2 mice, ctDNA-F-CLs significantly increased INF-γ and IL-6 production compared to ctDNA-N-CLs. Furthermore in L1210JF cells, ctDNA-F-CLs had significantly increased cytotoxicity compared to ctDNA-N-CLs. Tumor cell apoptosis was also found in co-culture of RAW264.7 cells and ctDNA-F-CLs treated L1210JF cells. In L1210JF tumor bearing mice, ctDNA-F-CLs were found to significantly inhibit tumor growth and prolong the median survival time (MeST). In contrast, ctDNA-N-CLs and free ctDNA showed similar activities for tumor inhibition and animal survival. Moreover, the anti-cancer effect of ctDNA-F-CL was further enhanced by combination with anti-cancer drug doxorubicin. These results suggest that ctDNA-F-CLs are a promising agent for treatment of FR-positive tumors.

DNA vaccine expressing repeated carcinoembryonic antigen (CEA)(625-667) induces strong immunity in mice

The efficacy of immunization with DNA plasmids for single truncated carcinoembryonic antigen (CEA) peptide or triple repeated CEA peptides in mice was evaluated. A DNA fragment the truncated CEA gene (nucleotide 625-667) encoding two helper T lymphocyte (HTL) epitopes was amplified by PCR and cloned for generating recombinant plasmids for single CEA(625-667) (pcDNA-CEA(625-667)) or triple CEA(625-667) (pcDNA-triCEA(625-667)), respectively. Subsequently, groups of BALB/c female mice were intramuscularly injected with pcDNA-CEA(625-667,) pcDNA-triCEA(625-667) or control pcDNA3.0 vector, respectively. Ten days after the last immunization, the frequency of splenic CD4(+) and CD8(+) T cells in the mice was determined by flow cytometry. The antigen-specific proliferation of splenic T cells and cytokine production ex vivo were analyzed by (3)H-TdR uptake and cytokine ELISA, respectively. The levels of serum antibodies against CEA in the mice were detected by Western blot and ELISA. Although immunization with plasmid for the CEA(625-667) peptide(s) did not alter the frequency of CD4(+) and CD8(+) T cells in mice, vaccination with plasmid for CEA peptide induced strong antigen-specific T cell proliferation, particularly for the plasmid encoding the triple-repeated CEA peptides, accompanied by significantly elevated levels of IFN-γ secreted by T cells from the mice immunized with triple-repeated peptides. Furthermore, immunization with the plasmid for CEA peptide stimulated higher levels of antigen-specific antibody responses in mice. Vaccination with the plasmid for the triple repeated CEA peptides induced stronger Th1 responses. Our findings may be useful for the development of effective DNA vaccine for the immunotherapy of cancer.

Identification and analysis of a CpG motif that protects turbot (Scophthalmus maximus) against bacterial challenge and enhances vaccine-induced specific immunity

Oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs in certain contexts are known to be immunostimulatory in vertebrate systems. CpG ODNs with immune effects have been identified for many fish species but, to our knowledge, not for turbot. In this study, a turbot-effective CpG ODN, ODN 205, was identified and a plasmid, pCN5, was constructed which contains the CpG motif of ODN 205. When administered into turbot via intraperitoneal (i.p.) injection, both ODN 205 and pCN5 could (i) inhibit bacterial dissemination in blood in dose and time dependent manners, and (ii) protect against lethal bacterial challenge. Immunological analyses showed that in vitro treatment with ODN 205 stimulated peripheral blood leukocyte proliferation, while i.p. injection with ODN 205 enhanced the respiratory burst activity, chemiluminescence response, and acid phosphatase activity of turbot head kidney macrophages. pCN5 treatment-induced immune responses similar to those induced by ODN 205 treatment except that pCN5 could also enhance serum bactericidal activity in a calcium-independent manner. To examine whether ODN 205 and pCN5 had any effect on specific immunity, ODN 205 and pCN5 were co-administered into turbot with a Vibrio harveyi subunit vaccine, DegQ. The results showed that pCN5, but not ODN 205, significantly increased the immunoprotective efficacy of DegQ and enhanced the production of specific serum antibodies in the vaccinated fish. Further analysis indicated that vaccination with DegQ in the presence of pCN5 upregulated the expression of the genes encoding MHC class IIalpha, IgM, Mx, and IL-8 receptor. Taken together, these results demonstrate that ODN 205 and pCN5 can stimulate the immune system of turbot and induce protection against bacterial challenge. In addition, pCN5 also possesses adjuvant property and can potentiate vaccine-induced specific immunity.

The combination of TLR-9 adjuvantation and electroporation-mediated delivery enhances in vivo antitumor responses after vaccination with HPV-16 E7 encoding DNA

Therapeutic DNA vaccination is an attractive adjuvant option to conventional methods in the fight against cancer, like surgery radiotherapy and chemotherapy. Despite strong antitumor effects that were observed in small animals with different antigens, DNA-based vaccines remain weakly immunogenic in large animals and primates compared to protein-based vaccines. Here, we sought to enhance the immunogenicity of a therapeutic nontransforming cervical cancer DNA vaccine (HPV-16 E7SH) by introduction of a highly optimized CpG cassette into the plasmid backbone as well as by an optimized DNA delivery using an advanced electroporation (EP) technology. By integrating the means for agent administration and EP into a single device, this technology enables a simple, one-step procedure that facilitates reproducibility. We found that highly optimized CpG motifs alone triggers an enhanced IFN-γ and granzyme B response in Elispot assays as well as stronger tumor regression. Furthermore, these effects could be dramatically enhanced when the CpG cassette containing plasmid was administered via the newly developed EP technology. These data suggest that an optimized application of CpG-enriched DNA vaccines may be an attractive strategy for the treatment of cancer. Collectively, these results provide a basis for the transfer of preclinical therapeutic DNA-based immunization studies into successful clinical cancer trials.

Synthetic oligodeoxynucleotides induce gastritis in mice

To investigate whether DNA directly induces gastritis and/or peptic ulcer, we injected synthetic DNA including CpG motif (CpG-DNA) to mouse stomach. BALB/c mice were injected with either saline, acetic acid (AA), CpG-DNA, or Control-DNA. Mice were sacrificed, and sections of the stomachs were stained with hematoxylin and eosin. The lesions were histopathologically scored from 0 to 4 based on the extent of the inflammation. Populations of neutrophils and mononuclear cells infiltrated to the lesion were calculated. IFN-y mRNA expression at the injection site was analyzed by RT-PCR. The number of CpG motifs included in the complete genomes of H. pylori HP26695 and J99, Escherichia coli O157, and Salmonella Typhi was determined by genomic analysis of these bacteria. Intragastric injection with CpG-DNA induced gastritis, and statistical analysis of histological scores revealed a significant difference between saline vs CpG-DNA (p = 0.037). The population of mononuclear cells infiltrated to the lesions was significantly higher in mice injected with CpG-DNA than that injected with AA (p = 0.0061). IFN-gamma mRNA expression was detected in the CpG-DNA group. While H. pylori includes multiple CpG motifs in its genome, it has fewer than the other pathogenic gram-negative bacilli. We conclude that synthetic DNA including CpG motif directly causes gastritis in mice and induces IFN-gamma production in the stomach. Bacterial DNA including CpG motif is known to stimulate innate immunity and to cause inflammation. Thus, H. pylori genomic DNA may be one of the virulent factors involved in H. pylori infection.

LL-37 promotes rapid sensing of CpG oligodeoxynucleotides by B lymphocytes and plasmacytoid dendritic cells

LL-37 is a cationic antimicrobial peptide derived from neutrophils and keratinocytes. It plays an important role in protection against bacterial infection in the skin and mucosal surfaces. However, its role within the blood compartment remains unclear given that serum inhibits its bactericidal property. In this study, we show that LL-37 promotes very rapid and highly efficient sensing of CpG motifs in bacterial DNA by human B lymphocytes and plasmacytoid dendritic cells (pDCs) in serum-containing media and in whole blood. LL-37 allowed detection of CpG oligodeoxynucleotide (ODN) within minutes of exposure. Without LL-37, 20-30 times more CpG was required to produce the same effect. The promotion of CpG detection by LL-37 was independent of the backbone of the ODN, as the effect was observed not only in ODNs with modified phosphorothioate backbone, but also in ODNs with natural phosphodiester backbone, as found in genomic DNA. Unmethylated CpG motifs within the phosphodiester ODN and LL-37-mediated delivery are required for pDCs to respond. In keeping with the above, cells responded to CpG-rich bacterial DNA and LL-37, but not to human DNA and LL-37. The ability of LL-37 to enhance delivery of CpG to stimulate immune cells is independent of its amphipathic structure and its bactericidal property. LL-37 aids the delivery of CpG to B cells and pDCs, but not T cells. These findings are pertinent to rapid recognition of microbial DNA and are highly relevant to contemporary studies of CpG/TLR9 agonists in vaccines and cancer therapy.