CpG motif identification for veterinary and laboratory species demonstrates that sequence recognition is highly conserved

Efficacy of different AV7909 dose regimens in a nonclinical model of pulmonary anthrax

Pulmonary anthrax caused by exposure to inhaled Bacillus anthracis, the most lethal form of anthrax disease, is a continued military and public health concern for the United States. The vaccine AV7909, consisting of the licensed anthrax drug substance AVA adjuvanted with CpG7909, induces high levels of toxin neutralizing antibodies in healthy adults using fewer doses than AVA. This study compares the ability of one- or two-dose regimens of AV7909 to induce a protective immune response in guinea pigs challenged with a lethal dose of aerosolized B. anthracis spores 6 weeks after the last vaccine dose. The results indicated that AV7909 was less effective when delivered as a single dose compared to the two-dose regimen that resulted in dose-dependent protection against death. The toxin neutralizing assay (TNA) titer and anti-PA IgG responses were proportional to the protective efficacy, with a 50% TNA neutralizing factor (NF50) greater than 0.1 associated with survival in animals receiving two doses of vaccine. The strong protection at relatively low TNA NF50 titers in this guinea pig model supports the exploration of lower doses in clinical trials to determine if these protective levels of neutralizing antibodies can be achieved in humans; however, protection with a single dose may not be feasible.

Immunopromoter improves liver apoptosis and immune response in Shaoxing ducklings

Antibiotics as feed additives, play a vital role in animal husbandry. However, overused antibiotics could cause endogenous infections in animals, and even endanger human health through the food chain. And immunopotentiators can make the low immune function improve and accelerate the induction of immune response. The aim of this study was to investigate the effects of five different immunopotentiators on the expression of liver apoptosis and immune factor related genes in Shaoxing ducklings (Anas Platyrhynchos). A total of 150 one-day-old Shaoxing ducklings were randomly divided into six groups including saline, chlorogenic acid, β-D-glucan, astragalus flavone, CpG DNA and chicken IgG, which were injected subcutaneously into the neck, respectively. At 18 days old, the liver tissues were collected to detecte the mRNA and protein expression levels of inflammatory and apoptosis-related genes. The results showed that compared with the control group, the mRNA and protein levels of liver Bcl2 with chlorogenic acid, β-D-glucan, astragalus flavone, CpG-DNA and chicken IgG were significantly decreased (p < 0.05), while the expression level of Caspase3 was up-regulated in some different degrees. In addition,The expression levels of liver iNOS and COX2 were significantly increased after the injection of five immunopotentiators (p < 0.05), and the mRNA levels of IFN-α, IFN-β, IL-1β, RIG-I, TLR3 and TLR7 genes were also significantly up-regulated compared with the control group (p < 0.05). In conclusion, chlorogenic acid, β-D-glucan, astragalus flavone, CpG-DNA and chicken IgG can be used as immunopotentiators to regulate duck innate immunity. This study provides a new way to prevent important infectious diseases of ducks, and also provides a certain reference for the application of antibiotic substitutes in animal production.

Post-genomic platform for development of oligonucleotide vaccines against RNA viruses: diamond cuts diamond

The coronavirus pandemic has starkly demonstrated the need to create highly effective vaccines against various viral diseases. The emerging new platforms for vaccine creation (adenovirus vectors and mRNA vaccines) have shown their worth in the fight against the prevention of coronavirus infection. However, adenovirus vectors and mRNA vaccines have a serious disadvantage: as a rule, only the S protein of the coronavirus is presented as an antigen. This tactic for preventing infection allows the ever-mutating virus to escape quickly from the immunity protection provided by such vaccines. Today, viral genomic databases are well-developed, which makes it possible to create new vaccines on a fundamentally new post-genomic platform. In addition, the technology for the synthesis of nucleic acids is currently experiencing an upsurge in demand in various fields of molecular biology. The accumulated experience suggests that the unique genomic sequences of viruses can act as antigens that trigger powerful humoral and cellular immunity. To achieve this effect, the following conditions must be created: the structure of the nucleic acid must be single-stranded, have a permanent 3D nanostructure, and have a unique sequence absent in the vaccinated organism. Oligonucleotide vaccines are able to resist the rapidly changing genomic sequences of RNA viruses by using conserved regions of their genomes to generate a long-term immune response, acting according to the adage that a diamond cuts a diamond. In addition, oligonucleotide vaccines will not contribute to antibody-dependent enhanced infection, since the nucleic acid of the coronavirus is inside the viral particle. It is obvious that new epidemics and pandemics caused by RNA viruses will continue to arise periodically in the human population. The creation of new, safe, and effective platforms for the production of vaccines that can flexibly change and adapt to new subtypes of viruses is very urgent and at this moment should be considered as a strategically necessary task.

Sharpening up tumor microenvironment to enhance the efficacy of immune checkpoint blockade on head and neck cancer using a CpG-oligodeoxynucleotide

Head and neck cancers are a type of life-threatening cancers characterized by an immunosuppressive tumor microenvironment. Only less than 20% of the patients respond to immune checkpoint blockade therapy, indicating the need for a strategy to increase the efficacy of immunotherapy for this type of cancers. Previously, we identified a type B CpG-oligodeoxynucleotide (CpG-ODN) called CpG-2722, which has the universal activity of eliciting an immune response in grouper, mouse, and human cells. In this study, we further characterized and compared its cytokine-inducing profiles with different types of CpG-ODNs. The antitumor effect of CpG-2722 was further investigated alone and in combination with an immune checkpoint inhibitor in a newly developed syngeneic orthotopic head and neck cancer animal model. Along with other inflammatory cytokines, CpG-2722 induces the gene expressions of interleukin-12 and different types of interferons, which are critical for the antitumor response. Both CpG-2722 and anti-programmed death (PD)-1 alone suppressed tumor growth. Their tumor suppression efficacies were further enhanced when CpG-2722 and anti-PD-1 were used in combination. Mechanistically, CpG-2722 shaped a tumor microenvironment that is favorable for the action of anti-PD-1, which included promoting the expression of different cytokines such as IL-12, IFN-β, and IFN-γ, and increasing the presence of plasmacytoid dendritic cells, M1 macrophages, and CD8 positive T cells. Overall, CpG-2722 provided a priming effect for CD8 positive T cells by sharpening the tumor microenvironment, whereas anti-PD-1 released the brake for their tumor-killing effect, resulting in an enhanced efficacy of the combined CpG-2722 and anti-PD-1.

M2e conjugated gold nanoparticle influenza vaccine displays thermal stability at elevated temperatures and confers protection to ferrets

Currently approved influenza vaccines are not only limited in breadth of protection but also have a limited shelf-life of 12-18 months when stored under appropriate conditions (2-8 °C). Inadvertent alteration in storage temperatures during manufacturing, transportation, distribution until delivery to patient, can damage the vaccine thus reducing its efficacy. A thermally stable vaccine can decrease the economic burden by reducing reliance on refrigeration system and can also enhance outreach of the vaccination program by allowing transportation to remote areas of the world where refrigerated conditions are scarce. We have previously developed a broadly protective influenza A vaccine by coupling the highly conserved extracellular region of the matrix 2 protein (M2e) of influenza A virus to gold nanoparticles (AuNPs) and upon subsequent addition of toll-like receptor 9 agonist - CpG, as an adjuvant, have shown its breadth of protection in a mouse model. In this study, we show that the vaccine is thermally stable when stored at 4 °C for 3 months, 37 °C for 3 months and 50 °C for 2 weeks in its lyophilized form, and later it was possible to readily reconstitute it in water without aggregation. Intranasal vaccination of mice using reconstituted vaccine induced M2e-specific IgG and IgG subtypes in serum similar to the freshly formulated vaccine, and fully protected mice against lethal influenza A challenge. Immunization of ferrets intranasally or intramuscularly with the vaccine induced M2e-specific IgG and there was reduced virus level in nasal wash of ferrets immunized through intranasal route.

Efficacy of the AV7909 anthrax vaccine candidate in guinea pigs and nonhuman primates following two immunizations two weeks apart

The anthrax vaccine candidate AV7909 is being developed as a next-generation vaccine for post-exposure prophylaxis (PEP) against inhalational anthrax. In clinical studies, two vaccinations with AV7909 administered either two or four weeks apart induced an enhanced immune response compared to BioThrax® (Anthrax Vaccine Adsorbed) (AVA). Anthrax toxin-neutralizing antibody (TNA) levels on Day 70 following initial vaccination that were associated with protection of animals exposed to inhalational anthrax were previously reported for the 0, 4-week AV7909 vaccination regimen. The current study shows that a 0, 2-week AV7909 vaccination regimen protected guinea pigs (GPs) and nonhuman primates (NHPs) against a lethal inhalational anthrax challenge on Days 28 and 70 after the first immunization. An earlier induction of protective TNA levels using a 0, 2-week AV7909 vaccination regimen may provide benefit over the currently approved AVA PEP 0, 2, and 4-week vaccination regimen.

Toll-Like Receptor 21 of Chicken and Duck Recognize a Broad Array of Immunostimulatory CpG-oligodeoxynucleotide Sequences

CpG-oligodeoxynucleotides (CpG-ODNs) mimicking the function of microbial CpG-dideoxynucleotides containing DNA (CpG-DNA) are potent immune stimuli. The immunostimulatory activity and the species-specific activities of a CpG-ODN depend on its nucleotide sequence properties, including CpG-hexamer motif types, spacing between motifs, nucleotide sequence, and length. Toll-like receptor (TLR) 9 is the cellular receptor for CpG-ODNs in mammalian species, while TLR21 is the receptor in avian species. Mammalian cells lack TLR21, and avian cells lack TLR9; however, both TLRs are expressed in fish cells. While nucleotide sequence properties required for a CpG-ODN to strongly activate mammalian TLR9 and its species-specific activities to different mammalian TLR9s are better studied, CpG-ODN activation of TLR21 is not yet well investigated. Here we characterized chicken and duck TLR21s and investigated their activation by CpG-ODNs. Chicken and duck TLR21s contain 972 and 976 amino acid residues, respectively, and differ from TLR9s as they do not have an undefined region in their ectodomain. Cell-based TLR21 activation assays were established to investigate TLR21 activation by different CpG-ODNs. Unlike grouper TLR21, which was preferentially activated by CpG-ODN with a GTCGTT hexamer motif, chicken and duck TLR21s do not distinguish among different CpG-hexamer motifs. Additionally, these two poultry TLR21s were activated by CpG-ODNs with lengths ranging from 15 to 31 nucleotides and with different spacing between CpG-hexamer motifs. These suggested that compared to mammalian TLR9 and grouper TLR21, chicken and duck TLR21s have a broad CpG-ODN sequence recognition profile. Thus, they could also recognize a wide array of DNA-associated molecular patterns from microbes. Moreover, CpG-ODNs are being investigated as antimicrobial agents and as vaccine adjuvants for different species. This study revealed that there are more optimized CpG-ODNs that can be used in poultry farming as anti-infection agents compared to CpG-ODN choices available for other species.

Developmental and reproductive safety evaluation of AV7909 anthrax vaccine candidate in rats

The AV7909 vaccine, consists of the Anthrax Vaccine Adsorbed (AVA) bulk drug substance and the immunostimulatory Toll‐like receptor 9 agonist oligodeoxynucleotide adjuvant CPG 7909. The purpose of this research was to evaluate the potential maternal, reproductive, and developmental toxicity of AV7909 in rats to support licensure for use in women of childbearing potential. Groups of first generation (F₀) female Sprague Dawley rats were dosed by intramuscular injection with water for injection, adjuvant or AV7909 at a volume of 0.5 ml/dose. Each rat received three vaccinations: 14 days prior to start of the mating period, on the first day of the mating period and on gestation day (GD) 7. There was no maternal mortality. Body weights, weight gain, and food consumption were comparable between groups. Findings in F₀ females were limited to transient injection site edema and nodules consistent with immunostimulatory effects of the vaccine and adjuvant. Administration of AV7909 did not affect mating, fertility, pregnancy, embryo‐fetal viability, growth, or morphologic development, parturition, maternal care of offspring or postnatal survival, growth, or development. There was no evidence of systemic inflammation in pregnant rats, based on evaluation of serum concentrations of the acute phase proteins alpha‐2‐macroglobulin and alpha‐1‐acid glycoprotein on GD 21. Anthrax lethal toxin‐neutralizing antibodies were detected in AV7909‐vaccinated F₀ females. The antibodies were also detected in the sera of fetuses and F₁ pups. Exposure of the fetuses and pups to maternally derived anthrax lethal toxin‐neutralizing antibodies was not associated with developmental toxicity.

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.

Treatment with Class A CpG Oligodeoxynucleotides in Cats with Naturally Occurring Feline Parvovirus Infection: A Prospective Study

Feline parvovirus (FPV) causes severe gastroenteritis and leukopenia in cats; the outcome is poor. Information regarding specific treatments is lacking. Class A CpG oligodeoxynucleotides (CpG-A) are short single-stranded DNAs, stimulating type I interferon production. In cats, CpG-A induced an antiviral response in vivo and inhibited FPV replication in vitro. The aim was to prospectively investigate the effects of CpG-A on survival, clinical score, hematological findings, antiviral response (cytokines), viremia, and fecal shedding (real-time qPCR) in cats naturally infected with FPV. Forty-two FPV-infected cats were randomized to receive 100 µg/kg of CpG-A (n = 22) or placebo (n = 20) subcutaneously, on admission and after 48 h. Blood and fecal samples were collected on admission, after 1, 3, and 7 days. All 22 cats showed short duration pain during CpG-A injections. The survival rate, clinical score, leukocyte and erythrocyte counts, viremia, and fecal shedding at any time-point did not differ between cats treated with CpG-A (50%) and placebo (40%). Antiviral myxovirus resistance (Mx) gene transcription increased in both groups from day 1 to 3 (p = 0.005). Antibodies against FPV on admission were associated with survival in cats (p = 0.002). In conclusion, CpG-A treatment did not improve the outcome in cats with FPV infection. FPV infection produced an antiviral response.

Adjuvant Effect of Toll-Like Receptor 9 Activation on Cancer Immunotherapy Using Checkpoint Blockade

Immunotherapy using checkpoint blockade has revolutionized cancer treatment, improving patient survival and quality of life. Nevertheless, the clinical outcomes of such immunotherapy are highly heterogeneous between patients. Depending on the cancer type, the patient response rates to this immunotherapy are limited to 20–30%. Based on the mechanism underlying the antitumor immune response, new therapeutic strategies have been designed with the aim of increasing the effectiveness and specificity of the antitumor immune response elicited by checkpoint blockade agents. The activation of toll-like receptor 9 (TLR9) by its synthetic agonists induces the antitumor response within the innate immunity arm, generating adjuvant effects and priming the adaptive immune response elicited by checkpoint blockade during the effector phase of tumor-cell killing. This review first describes the underlying mechanisms of action and current status of monotherapy using TLR9 agonists and immune checkpoint inhibitors for cancer immunotherapy. The rationale for combining these two agents is discussed, and evidence indicating the current status of such combination therapy as a novel cancer treatment strategy is presented.

Current Status and Trends in Prophylaxis and Management of Anthrax Disease

Bacillus anthracis has been identified as a potential military and bioterror agent as it is relatively simple to produce, with spores that are highly resilient to degradation in the environment and easily dispersed. These characteristics are important in describing how anthrax could be used as a weapon, but they are also important in understanding and determining appropriate prevention and treatment of anthrax disease. Today, anthrax disease is primarily enzootic and found mostly in the developing world, where it is still associated with considerable mortality and morbidity in humans and livestock. This review article describes the spectrum of disease caused by anthrax and the various prevention and treatment options. Specifically we discuss the following; (1) clinical manifestations of anthrax disease (cutaneous, gastrointestinal, inhalational and intravenous-associated); (2) immunology of the disease; (3) an overview of animal models used in research; (4) the current World Health Organization and U.S. Government guidelines for investigation, management, and prophylaxis; (5) unique regulatory approaches to licensure and approval of anthrax medical countermeasures; (6) the history of vaccination and pre-exposure prophylaxis; (7) post-exposure prophylaxis and disease management; (8) treatment of symptomatic disease through the use of antibiotics and hyperimmune or monoclonal antibody-based antitoxin therapies; and (9) the current landscape of next-generation product candidates under development.

Development of a guinea pig inhalational anthrax model for evaluation of post-exposure prophylaxis efficacy of anthrax vaccines

A next-generation anthrax vaccine candidate, AV7909, is being developed for post-exposure prophylaxis (PEP) of inhalational anthrax in combination with the recommended course of antimicrobial therapy. Clinical efficacy studies of anthrax countermeasures in humans are not ethical or feasible, therefore, licensure of AV7909 for PEP is being pursued under the US Food and Drug Administration (FDA) Animal Rule, which requires that evidence of effectiveness be demonstrated in an animal model of anthrax, where results of studies in such a model can establish reasonable likelihood of AV7909 to produce clinical benefit in humans. Initial development of a PEP model for inhalational anthrax included evaluation of post-exposure ciprofloxacin pharmacokinetics (PK), tolerability and survival in guinea pigs treated with various ciprofloxacin dosing regimens. Three times per day (TID) intraperitoneal (IP) dosing with 7.5 mg/kg of ciprofloxacin initiated 1 day following inhalational anthrax challenge and continued for 14 days was identified as a well tolerated partially curative ciprofloxacin treatment regimen. The added benefit of AV7909 vaccination was evaluated in guinea pigs given the partially curative ciprofloxacin treatment regimen. Groups of ciprofloxacin-treated guinea pigs were vaccinated. 1 and 8 days post-challenge with serial dilutions of AV7909, a 1:16 dilution of AVA, or normal saline. A group of untreated guinea pigs was included as a positive control to confirm lethal B. anthracis exposure. Post-exposure vaccination with the AV7909 anthrax vaccine candidate administered in combination with the partially curative ciprofloxacin treatment significantly increased survival of guinea pigs compared to ciprofloxacin treatment alone. These results suggest that the developed model can be useful in demonstrating added value of the vaccine for PEP.

Intranasal treatment with CpG-B oligodeoxynucleotides protects CBA mice from lethal equine herpesvirus 1 challenge by an innate immune response

Equine herpesvirus 1 (EHV-1) is the causative agent of a number of equine disease manifestations, including severe disease of the central nervous system, respiratory infections, and abortion storms. Our results showed that intranasal treatment with CpG-B oligodeoxynucleotides (ODN 1826) protected CBA mice from pathogenic EHV-1 RacL11 challenge. The IFN-γ gene and seven interferon-stimulated genes (ISGs) were upregulated 39.4- to 260.3-fold at 8 h postchallenge in the lungs of RacL11-challenged mice that had been treated with CpG-B ODN. Interestingly, IFN-γ gene expression was upregulated by 26-fold upon RacL11 challenge in CpG-B ODN-treated mice lungs as compared to that of CpG-A ODN (ODN 1585)-treated mice lungs; however, the seven ISGs were upregulated by 2.4-5.0-fold, suggesting that IFN-γ is a major factor in the protection of CBA mice from the lethal challenge. Pre-treatment with IFN-γ significantly reduced EHV-1 yield in murine alveolar macrophage MH-S cells, but not in mouse lung epithelial MLE12 cells. These results suggest that CpG-B ODN may be used as a prophylactic agent in horses and provide a basis for more effective treatment of EHV-1 infection.

Immunostimulatory Activities of CpG-Oligodeoxynucleotides in Teleosts: Toll-Like Receptors 9 and 21

Toll-like receptors (TLRs) are pattern-recognition receptors that detect a wide variety of microbial pathogens for the initiation of host defense immunological responses. Thirteen TLRs have been identified in mammals, and teleosts contain 22 mammalian or non-mammalian TLRs. Of these, TLR9 and TLR21 are the cytosine-phosphate-guanosine-oligodeoxynucleotides (CpG-ODNs) recognition TLRs in teleosts. TLR9 is a mammalian TLR expressed in teleost but not in the avian species. TLR21 is a non-mammalian TLR expressed in both teleost and the avian species. Synthetic CpG-ODNs are potent immunostimulants that are being studied for their application against tumors, allergies, and infectious diseases, and as a vaccine adjuvant in humans. The immunostimulatory effects of CpG-ODNs as vaccine adjuvants and their antimicrobial function in domestic animals and teleosts are also being investigated. Most of our current knowledge about the molecular basis for the immunostimulatory activity of CpG-ODNs comes from earlier studies of the interaction between CpG-ODN and TLR9. More recent studies indicate that in addition to TLR9, TLR21 is another receptor for CpG-ODN recognition in teleosts to initiate immune responses. Whether these two receptors have differential functions in mediating the immunostimulatory activity of CpG-ODN in teleost has not been well-studied. Nevertheless, the existence of two recognition TLRs suggests that the molecular basis for the immunostimulatory activity of CpG-ODN in teleosts is different and more complex than in mammals. This article reviews the current knowledge of TLR9 and TLR21 activation by CpG-ODNs. The key points that need to be considered for CpG-ODNs as immunostimulants with maximum effectiveness in activation of immune responses in teleosts are discussed. This includes the structure/activity relationship of CpG-ODN activities for TLR9 and TLR21, the structure/functional relationship of these two TLRs, and differential expression levels and tissue distributions for these two TLRs.

Intranasal delivery of a formulation containing stage-specific recombinant proteins of Fasciola hepatica cathepsin L5 and cathepsin B2 triggers an anti-fecundity effect and an adjuvant-mediated reduction in fluke burden in sheep

Fasciola hepatica infection continues to be a major problem in the agriculture sector, particularly in sheep and cattle. Cathepsin L and B proteases are major components of the excretory/secretory material of the parasite, and their roles in several important aspects of parasite invasion and survival has led to their use as targets in rational vaccine design. Previous studies in rats demonstrated that the use of stage-specific antigens, cathepsin B2 and cathepsin L5, as part of a multivalent vaccine, was able to confer significant protection against challenge. In the present study, recombinant versions of cathepsin L5 and cathepsin B2 produced in yeast were used in combination to vaccinate sheep. Intramuscular and intranasal forms of administration were applied, and sheep were subsequently challenged with 150 F. hepatica metacercariae. Intramuscular vaccination was able to induce a strong systemic antibody response against both antigens, but failed to confer significant protection. Conversely, no elevated antibody response was detected against the vaccine antigens following nasal vaccination; however, a reduction in parasite egg viability (>92%) and a statistically significant (p = 0.006), predominantly adjuvant-mediated reduction in worm burdens was observed.

CpG-oligodeoxynucleotides developed for grouper toll-like receptor (TLR) 21s effectively activate mouse and human TLR9s mediated immune responses

Synthetic phosphorothiolate-modified CpG-oligodeoxynucleotides (CpG-ODNs) are potent immune stimuli. Toll-like receptor (TLR) 9 and TLR21 are their cellular receptors in different species. The structural requirements for CpG-ODN to strongly activate TLR9 have been relatively well studied, but studies on TLR21 are in their infancy. Therefore, in this study, we investigated the interaction between CpG-ODNs and TLR21s from groupers (Epinephelus spp.), which are economically important fish species. We cloned the cDNA of giant grouper (E. lanceolatus) TLR21, and compared its sequence with orange-spotted grouper (E. coioides) TLR21A and TLR21B. These three receptors were activated by CpG-ODNs containing the GTCGTT motif but not by those containing the GACGTT motif. We developed two CpG-ODNs that contained 19 phosphorothiolated deoxynucleotides with one or two GTCGTT motifs. These CpG-ODNs had better activity on grouper TLR21s than currently developed CpG-ODNs, and produced similar immune stimulatory profiles when applied to cells isolated from orange-spotted grouper. The developed CpG-ODNs also effectively activated both human and mouse TLR9-mediated NF-κB activation and cytokine productions. These findings suggest that the GTCGTT motif is required for CpG-ODNs to activate grouper TLR21s, and that the CpG-ODNs that were developed for grouper TLR21s contain structures that effectively activate human and mouse TLR9s.

Phosphodiester backbone of the CpG motif within immunostimulatory oligodeoxynucleotides augments activation of Toll-like receptor 9

Toll-like receptor 9 (TLR9) stimulatory CpG-containing oligodeoxynucleotides (ODNs) with phosphorothioate backbones have successfully replaced the naturally occurring agonists of TLR9 in drug development due to their increased stability. Replacing the nonbridging oxygen with a sulfur atom in the phosphate linkage of ODNs has been accepted as having a minor impact on the chemical and physical properties of the agonists. Here, we report that the TLR9 binding site exhibits a strong bias in favor of a phosphodiester backbone over the phosphorothioate backbone of the CpG motif. Furthermore, we show that while single point mutations of W47, W96 and K690 within the TLR9 binding site retains full TLR9 activation by phosphodiester-based ODNs, activation by phosphorothioate-based ODNs is strongly impaired. The substitution of a phosphorothioate linkage for a phosphodiester linkage of just the CpG motif considerably improves the activation potency of a phosphorothioate-based oligonucleotide for human B-cells and plasmacytoid dendritic cells, as well as for mouse bone marrow-derived dendritic cells and macrophages. Our results highlight the functional significance of the phosphodiester linkage of a CpG dinucleotide for binding, which is important in designing improved immunostimulatory TLR9 agonists.

Intranasal immunization with a recombinant outer membrane protein H based Haemorrhagic septicemia vaccine in dairy calves

Haemorrhagic septicemia (HS) is a contagious disease in cattle with high morbidity and mortality rates. HS vaccine in Thailand is an oil-adjuvant formulation, and is difficult to administer. The present study aimed to formulate and evaluate the protection in dairy calves conferred by immunization with an in-house intranasal HS vaccine. The intranasal vaccine was formulated in a total volume of 500 µl containing either 50 or 100 µg of the recombinant outer membrane protein H (rOmpH) of Pasteurella multocida strain M-1404 (serovar B:2), and 10 µg of Cytosine-phosphate-guanosine oligodeoxynucleotides (CpG-ODN) as a mucosal adjuvant. Intranasal immunizations were conducted three times at three-week intervals. The antibodies post-immunization were detected by indirect ELISA and demonstrated efficient in vitro activity in suppressing a P. multocida strain from the complement-mediated killing assay. An intranasal vaccine induced both the serum IgG and secretory IgA levels that were significantly higher than the level conferred by the parenteral vaccine (P<0.05). Challenge exposure was conducted with a P. multocida strain M-1404 at day 72 of the experiments. The immunized calves had reduced clinical signs after challenge exposure that would normally result in disease proliferation. We conclude that intranasal vaccination of calves with rOmpH with CpG-ODN 2007 stimulated serum and secretory antibodies to rOmpH and whole cells of P. multocida strain M-1404 antigen. Moreover, it would result in protection in calves against artificial P. multocida infection.

Discrimination of human and nonhuman blood using Raman spectroscopy with self-reference algorithm

We report a self-reference algorithm to discriminate human and nonhuman blood by calculating the ratios of identification Raman peaks to reference Raman peaks and choosing appropriate threshold values. The influence of using different reference peaks and identification peaks was analyzed in detail. The Raman peak at 1003  cm-1 was proved to be a stable reference peak to avoid the influencing factors, such as the incident laser intensity and the amount of sample. The Raman peak at 1341  cm-1 was found to be an efficient identification peak, which indicates that the difference between human and nonhuman blood results from the C-H bend in tryptophan. The comparison between self-reference algorithm and partial least square method was made. It was found that the self-reference algorithm not only obtained the discrimination results with the same accuracy, but also provided information on the difference of chemical composition. In addition, the performance of self-reference algorithm whose true positive rate is 100% is significant for customs inspection to avoid genetic disclosure and forensic science.

Protective effects of CpG-ODN 2007 administration against Edwardsiella tarda infection in olive flounder (Paralichthys olivaceus)

In this study, we investigated the immunostimulatory and protective effects of CpG motif oligonucleotides (CpG-ODNs) against Edwardsiella tarda infection in olive flounder (Paralichthys olivaceus). Groups of fish injected with CpG-ODNs (1585, 1668, and 2007) or PBS (control) showed varying mortality rates in response to challenge with E. tarda. The survival rates of fish treated with CpG-ODN 1668 and 2007, which belonged to the same class type B, were 45% and 60%, respectively, with CpG-ODN 2007 showing the highest survival rate. Further analysis showed that the respiratory burst and bactericidal activities induced by CpG-ODN 2007 were higher than those in the control group (induced by non-CpG-ODNs) or in the group of fish induced by CpG-ODN 1585, which belonged to class type A. Additionally, the respiratory burst activity induced by CpG-ODN 2007 was higher than that induced by CpG-ODN 1668, despite similar bactericidal activity titers. In vivo experiments showed that CpG-ODN 2007 stimulation resulted in higher survival rates than CpG-ODN 1668 stimulation, possibly owing to differences in respiratory burst activity. In summary, we demonstrated that differences in CpG-motif or class type altered respiratory burst and bactericidal activities, resulting in differences in survival rates against E. tarda challenge in the olive flounder. Therefore, it is necessary to use CpG-ODNs optimized against E. tarda infection in olive flounder, because different CpG motifs belonging to the same class type have different effects.

Conservation and Divergence of Ligand Recognition and Signal Transduction Mechanisms in Toll-Like Receptors

Toll-like receptors (TLRs) play a central role in innate immunity as pathogen sensors. During the last decade, structural analyses of TLRs have revealed the mechanisms of ligand recognition and signal transduction. Each TLR recognizes its cognate ligand in a different manner, whereas signal transduction is achieved by a common mechanism. In this review, the mechanisms of ligand recognition and signal transduction by TLRs are summarized based on recent structural information.

Correlation between anthrax lethal toxin neutralizing antibody levels and survival in guinea pigs and nonhuman primates vaccinated with the AV7909 anthrax vaccine candidate

The anthrax vaccine candidate AV7909 is being developed as a next generation vaccine for a post-exposure prophylaxis (PEP) indication against anthrax. AV7909 consists of the Anthrax Vaccine Adsorbed (AVA, BioThrax®) bulk drug substance adjuvanted with the immunostimulatory oligodeoxynucleotide (ODN) compound, CPG 7909. The addition of CPG 7909 to AVA enhances both the magnitude and the kinetics of antibody responses in animals and human subjects, making AV7909 a suitable next-generation vaccine for use in a PEP setting. The studies described here provide initial information on AV7909-induced toxin-neutralizing antibody (TNA) levels associated with the protection of animals from lethal Bacillus anthracis challenge. Guinea pigs or nonhuman primates (NHPs) were immunized on Days 0 and 28 with various dilutions of AV7909, AVA or a saline or Alhydrogel+CPG 7909 control. Animals were challenged via the inhalational route with a lethal dose of aerosolized B. anthracis (Ames strain) spores and observed for clinical signs of disease and mortality. The relationship between pre-challenge serum TNA levels and survival following challenge was determined in order to calculate a threshold TNA level associated with protection. Immunisation with AV7909 induced a rapid, highly protective TNA response in guinea pigs and NHPs. Surprisingly, the TNA threshold associated with a 70% probability of survival for AV7909 immunized animals was substantially lower than the threshold which has been established for the licensed AVA vaccine. The results of this study suggest that the TNA threshold of protection against anthrax could be modified by the addition of an immune stimulant such as CPG 7909 and that the TNA levels associated with protection may be vaccine-specific.

Cross-protection conferred by immunization with an rOmpH-based intranasal fowl cholera vaccine

A previous study demonstrated that a recombinant outer membrane protein H (rOmpH)-based intranasal fowl cholera vaccine elicited efficient homologous protection against the Pasteurella multocida strain X-73 (A:1) in chickens. The present study aimed to determine the cross-protectivity against heterologous P. multocida strains. The rOmpH was purified via electroelution and formulated with two kinds of adjuvants. The vaccine formulations in a total volume of 100 µl were 100 µg rOmpH with 3 µg of Escherichia coli enterotoxin B or 10 µg of CpG ODN2007. Chickens were assigned to three experimental groups depending on bacterial strain challenge exposure as well as three control groups. The chickens were immunized intranasally three times at three-week intervals. Challenge exposures were conducted by inoculation with homologous strain X-73 or heterologous strains P-1059 (A:3) or P-1662 (A:4) at four weeks after the final immunization. The specific antibody against rOmpH was produced in vaccinated birds. Sera IgY and secretory IgA antibody titres were significantly increased (P < 0.05) post-immunization. The stimulation index values of the vaccinated groups were significantly different from stimulation index values of the non-vaccinated groups (P < 0.05). Chicken survival rates after exposure to avian P. multocida strains ranged from 70% to 100%. There was no significant difference in protection between two kinds of adjuvants in vaccine formulations. Statistical analysis indicated no significant differences in protection among avian P. multocida strains challenge exposure. We conclude that an in-house rOmpH-based intranasal fowl cholera vaccine produced efficient cross-protectivity against heterologous strains of P. multocida.

Selectivity of Human TLR9 for Double CpG Motifs and Implications for the Recognition of Genomic DNA

TLR9 acts as a first-line host defense against pathogens recognizing DNA comprising unmethylated CpG motifs present in bacteria and viruses. Species- and sequence-specific recognition differences were demonstrated for TLR9 receptors. Activation of human (h)TLR9 requires a pair of closely positioned CpG motifs within oligodeoxyribonucleotides (ODNs), whereas mouse TLR9 is effectively activated by an ODN with a single CpG motif. Molecular model-directed mutagenesis identified two regions, site A and site B, as important for receptor activation. Amino acid residues Gln³⁴⁶ and Arg³⁴⁸ within site A contribute to the sequence-specific recognition by hTLR9 in determining the bias for two appropriately spaced CpG motifs within immunostimulatory ODNs. Mutation of Gln⁵⁶² at site B, in combination with Gln³⁴⁶ and Arg³⁴⁸ mutations of mouse counterparts, increased activation of hTLR9 by mouse-specific ODN, mammalian genomic DNA, and bacterial DNA. We propose that the double CpG motif sequence-specificity of hTLR9 results in decreased activation by ODNs with a lower frequency of CpG motifs, such as from mammalian genomic DNA, which increases hTLR9 selectivity for pathogen versus host DNA.

Towards effective non-viral gene delivery vector

Despite very good safety records, clinical trials using plasmid DNA failed due to low transfection efficiency and brief transgene expression. Although this failure is both due to poor plasmid design and to inefficient delivery methods, here we will focus on the former. The DNA elements like CpG motifs, selection markers, origins of replication, cryptic eukaryotic signals or nuclease-susceptible regions and inverted repeats showed detrimental effects on plasmids' performance as biopharmaceuticals. On the other hand, careful selection of promoter, polyadenylation signal, codon optimization and/or insertion of introns or nuclear-targeting sequences for therapeutic protein expression can enhance the clinical efficacy. Minimal vectors, which are devoid of the bacterial backbone and consist exclusively of the eukaryotic expression cassette, demonstrate better performance in terms of expression levels, bioavailability, transfection rates and increased therapeutic effects. Although the results are promising, minimal vectors have not taken over the conventional plasmids in clinical trials due to challenging manufacturing issues.

Development of an autologous canine cancer vaccine system for resectable malignant tumors in dogs

While conventional therapies exist for canine cancer, immunotherapies need to be further explored and applied to the canine setting. We have developed an autologous cancer vaccine (K9-ACV), which is available for all dogs with resectable disease. K9-ACV was evaluated for safety and immunogenicity for a variety of cancer types in a cohort of companion dogs under veterinary care. The autologous vaccine was prepared by enzymatic digestion of solid tumor biopsies. The resultant single cell suspensions were then UV-irradiated resulting in immunogenic cell death of the tumor cells. Following sterility and endotoxin testing, the tumor cells were admixed with CpG ODN adjuvant and shipped to the participating veterinary clinics. The treating veterinarians then vaccinated each patient with three intradermal injections (10 million cells per dose) at 30-day intervals (one prime and two boost injections). In a cohort of 20 dogs completing the study, 17 dogs (85%) developed an augmented IgG response to autologous tumor antigens as demonstrated using western blot analysis of pre- and post-peripheral blood samples. We also report several dogs have lived beyond expected survival time based on previously published data. In summary, K9-ACV is an additional option to be considered for the treatment of dogs with resectable cancer.

A tale of two sites: how inflammation can reshape the microbiomes of the gut and lungs

Inflammation can directly and indirectly modulate the bacterial composition of the microbiome. Although studies of inflammation primarily focus on its function to negatively select against potential pathogens, some bacterial species have the ability to exploit inflammatory byproducts for their benefit. Inflammatory cells release reactive nitrogen species as antimicrobial effectors against infection, but some facultative anaerobes can also utilize the increase in extracellular nitrate in their environment for anaerobic respiration and growth. This phenomenon has been studied in the gastrointestinal tract, where blooms of facultative anaerobic Gammaproteobacteria, primarily Escherichia coli, often occur during colonic inflammation. In cystic fibrosis, Pseudomonas aeruginosa, another Gammaproteobacteria facultative anaerobe, can reduce nitrogen for anaerobic respiration and it blooms in the airways of the chronically inflamed cystic fibrosis lung. This review focuses on the evidence that inflammation can provide terminal electron acceptors for anaerobic respiration and can support blooms of facultative anaerobes, such as E. coli and P. aeruginosa in distinct, but similar, environments of the inflamed gastrointestinal and respiratory tracts.

Activation of toll-like receptor signaling pathways leading to nitric oxide-mediated antiviral responses

Toll-like receptors (TLRs), well-characterized pattern-recognizing receptors of the innate arm of the immune system, are vital in detecting pathogen-associated molecular patterns (PAMPs). The TLR-PAMP interaction initiates an intracellular signaling cascade, predominantly culminating in upregulation of antiviral components, including inducible nitric oxide synthase (iNOS). After activation, various TLR pathways can promote iNOS production via the myeloid differentiation primary response-88 (MyD-88) adapter protein. Subsequently, iNOS facilitates production of nitric oxide (NO), a highly reactive and potent antiviral molecule that can inhibit replication of RNA and DNA viruses. Furthermore, NO can diffuse freely across cell membranes and elicit antiviral mechanisms in various ways, including direct and indirect damage to viral genomes. This review emphasizes current knowledge of NO-mediated antiviral responses elicited after activation of TLR signaling pathways.

Organosilane and Polyethylene Glycol Functionalized Magnetic Mesoporous Silica Nanoparticles as Carriers for CpG Immunotherapy In Vitro and In Vivo

Cytosine-guanine (CpG) containing oligodeoxynucleotides (ODN) have significant clinical potential as immunotherapeutics. However, limitations exist due to their transient biological stability in vivo, lack of specificity for target cells, and poor cellular uptake. To address these issues, we prepared amine magnetic mesoporous silica nanoparticles (M-MSN-A) then further modified with polyethylene glycol (PEG) for use as CpG delivery vectors. The PEG modified M-MSN-A (M-MSN-P) had notable CpG ODN loading capacity, negligible cytotoxicity, and were easily internalized into cells where they released the loaded CpG into the cytoplasm. As a result, such complexes were effective in activating macrophages and inhibiting tumor cells when combined with chemotherapeutics in vitro. Furthermore, these complexes had excellent immuno-stimulating activity in vivo, compared to the free CpG therapeutics. We report here a highly effective MSNs-based delivery system with great potential as a therapeutic CpG formulation in cancer immunotherapy.

Species-Specific Minimal Sequence Motif for Oligodeoxyribonucleotides Activating Mouse TLR9

Synthetic oligodeoxyribonucleotides (ODNs) containing unmethylated CpG recapitulate the activation of TLR9 by microbial DNA. ODNs are potent stimulators of the immune response in cells expressing TLR9. Despite extensive use of mice as experimental animals in basic and applied immunological research, the key sequence determinants that govern the activation of mouse TLR9 by ODNs have not been well defined. We performed a systematic investigation of the sequence motif of B class phosphodiester ODNs to identify the sequence properties that govern mouse TLR9 activation. In contrast to ODNs activating human TLR9, where the minimal sequence motif for the receptor activation comprises a pair of closely positioned CpGs we found that the mouse TLR9 requires a single CpG positioned 4-6 nt from the 5'-end. Activation is augmented by a 5'TCC sequence one to three nucleotides from the CG. The distance of the CG dinucleotide of four to six nucleotides from the 5'-end and the ODN's length fine-tunes activation of mouse macrophages. Length of the ODN <23 and >29 nt decreases activation of dendritic cells. The ODNs with minimal sequence induce Th1-type cytokine synthesis in dendritic cells and confirm the expression of cell surface markers in B cells. Identification of the minimal sequence provides an insight into the sequence selectivity of mouse TLR9 and points to the differences in the receptor selectivity between species probably as a result of differences in the receptor binding sites.

Minimal sequence requirements for oligodeoxyribonucleotides activating human TLR9

Synthetic oligodeoxyribonucleotides (ODNs) containing CpG (unmethylated deoxycytidylyl-deoxyguanosine dinucleotide) motifs activate endosomal TLR9. The nucleotide sequence, length, and dimerization properties of ODNs modulate their activation of TLR9. We performed a systematic investigation of the sequence motifs of B-class and C-class phosphodiester ODNs to identify the sequence properties that govern TLR9 activation. ODNs shorter than 21 nt and with the adenosine adjacent to the cytidine-guanosine (CG) dinucleotide motif led to a significant loss of the propensity to activate TLR9. The distance between the stimulatory CpG motifs within the ODN fine-tunes the activation of B cells. The minimal ODNs that activate human TLR9 comprise 2 CG dinucleotides separated by 6-10 nt, where the first CpG motif is preceded by the 5'-thymidine and the elongated poly-thymidine tail at the 3' end of the ODN. The minimal sequence provides insight into the molecular mechanism of TLR9 ligand recognition. On the basis of sequence requirements, we conclude that two binding sites with different affinities for CG are formed in the human TLR9 dimer, with a very stringent binding site interacting with the 5' CpG motif.

Improving adjuvant systems for polyclonal egg yolk antibody (IgY) production in laying hens in terms of productivity and animal welfare

The antibody production in the egg yolks of immunized laying hens is seen as a way of improving animal welfare compared with conventional production by mammals. Immunoglobulin Y (IgY) technology, however, has still to address welfare issues linked to the widespread use of an adjuvant in vaccines. Currently, Freund's adjuvants, complete (FCA) or incomplete (FIA), remain the standard. This study sought to evaluate various approaches used to enhance egg yolk antibody production in terms of both productivity and avian welfare. The outer membrane protein (OMP) of Salmonella Typhimurium was used as the prototype antigen. At 20 weeks of age, 56 ISA Brown hens, with specific-Salmonella-free status, were divided into seven groups (n=8) and received an initial intramuscular immunization. Hens in the two negative control groups received phosphate buffered saline (PBS) or FIA alone. Hens in the other groups received 80μg of Salmonella OMP emulsified with one of the following adjuvants: 200μl of FIA alone (T1); 200μl of FIA supplemented with 8μg of C-phosphate-guanosine oligodeoxynucleotides (CpG-ODN) (T2); and 280μl of Montanide ISA 70 VG (T4). Birds in the T3 group received the antigen in emulsion with FIA and were given the tested immunostimulatory component (l-carnitine) via their feed (100mg/kg). A positive control group (PC) received FCA for the first and final immunizations and FIA for the other boosters. Immunization was repeated after 20, 46, 82 and 221 days. Eggs were collected regularly until 242 days after the first immunization and the anti-Salmonella Typhimurium activities in the yolk were determined by ELISA. After 242 days, the birds were euthanized and the injection sites were evaluated for gross and microscopic lesions. Among the tested immunostimulatory approaches, supplementation of FIA with CpG-ODN led to a significant and long-lasting enhancement of the specific antibody response. This treatment was even higher than the positive benchmark using FCA in the first immunization. The study results showed that a clinical examination of injection sites is insufficient for drawing conclusions about the local tolerance of vaccines. Tissue damage was noticeable in all treatment groups. The birds receiving the Montanide adjuvant, however, had fewer and less severe lesions. Given these limited side-effects, Montanide ISA 70 VG could provide the depot effect needed to ensure the immunomodulatory efficiency of CpG-ODN. The association of these two adjuvants could prove a promising alternative to Freund's adjuvants (FA).

Development of CpG-oligodeoxynucleotides for effective activation of rabbit TLR9 mediated immune responses

CpG-oligodeoxynucleotides (CpG-ODN) are potent immune stimuli being developed for use as adjuvants in different species. Toll-like receptor 9 (TLR9) is the cellular receptor for CpG-ODN in mammalian cells. The CpG-ODN with 18–24 deoxynucleotides that are in current use for human and mouse cells, however, have low activity with rabbit TLR9. Using a cell-based activation assay, we developed a type of CpG-ODN containing a GACGTT or AACGTT motif in 12 phosphorothioate-modified deoxynucleotides with potent stimulatory activity for rabbit TLR9. The developed CpG-ODN have higher activities than other developed CpG-ODN in eliciting antigen-nonspecific immune responses in rabbit splenocytes. When mixed with an NJ85 peptide derived from rabbit hemorrhagic disease virus, they had potent activities to boost an antigen-specific T cell activation and antibody production in rabbits. Compared to Freund’s adjuvant, the developed CpG-ODN are capable of boosting a potent and less toxic antibody response. The results of this study suggest that both the choice of CpG-motif and its length are important factors for CpG-ODN to effectively activate rabbit TLR9 mediated immune responses.

Cell-mediated immune responses induced by BHV-1: rational vaccine design

Bovine herpesvirus-1 (BHV-1) is one of the major respiratory pathogens in cattle worldwide. Although antibodies have been correlated with protection and recovery from BHV-1 infection, the cell-mediated immune response is also a critical defense mechanism because cell-to-cell spread occurs before hematogenous spread. Furthermore, induction of robust T-cell memory is critical for the long-term duration of immunity. Among current commercial vaccines, the attenuated conventional vaccines induce a balanced immune response and long-term memory but may result in viral shedding. By contrast, inactivated vaccines primarily elicit a humoral immune response and relative short-term memory. These vaccines do not allow differentiation of vaccinated from infected cattle. Recent efforts are focusing on the development of vaccines that induce a balanced immune response and long-term memory, as well as having differentiation markers. This includes well-defined genetically engineered gene-deleted, subunit and vectored vaccines.

Toll-like receptor 9 and 21 have different ligand recognition profiles and cooperatively mediate activity of CpG-oligodeoxynucleotides in zebrafish

CpG-oligodeoxynucleotides (CpG-ODNs) are potent immune stimuli currently under investigation as antimicrobial agents for different species. Toll-like receptor (TLR) 9 and TLR21 are the cellular receptors of CpG-ODN in mammals and chickens, respectively. The avian genomes lack TLR9, whereas mammalian genomes lack TLR21. Although fish contain both of these genes, the biological functions of fish TLR9 and TLR21 have not been investigated previously. In this study, we comparatively investigated zebrafish TLR9 (zebTLR9) and TLR21 (zebTLR21). The two TLRs have similar expression profiles in zebrafish. They are expressed during early development stages and are preferentially expressed in innate immune function-related organs in adult fish. Results from cell-based activation assays indicate that these two zebrafish TLRs are functional, responding to CpG-ODN but not to other TLR ligands. zebTLR9 broadly recognized CpG-ODN with different CpG motifs, but CpG-ODN with GACGTT or AACGTT had better activity to this TLR. In contrast, zebTLR21 responded preferentially to CpG-ODN with GTCGTT motifs. The distinctive ligand recognition profiles of these two TLRs were determined by their ectodomains. Activation of these two TLRs by CpG-ODN occurred inside the cells and was modulated by UNC93B1. The biological functions of these two TLRs were further investigated. The CpG-ODNs that activate both zebTLR9 and zebTLR21 were more potent than others that activate only zebTLR9 in the activation of cytokine productions and were more bactericidal in zebrafish. These results suggest that zebTLR9 and zebTLR21 cooperatively mediate the antimicrobial activities of CpG-ODN. Overall, this study provides a molecular basis for the activities of CpG-ODN in fish.

Immunostimulatory CpG motifs in the genomes of gut bacteria and their role in human health and disease

Toll-like receptor (TLR) signalling plays an important role in epithelial and immune cells of the intestine. TLR9 recognizes unmethylated CpG motifs in bacterial DNA, and TLR9 signalling maintains the gut epithelial homeostasis. Here, we carried out a bioinformatic analysis of the frequency of CpG motifs in the genomes of gut commensal bacteria across major bacterial phyla. The frequency of potentially immunostimulatory CpG motifs (all CpG hexamers) or purine-purine-CG-pyrimidine-pyrimidine hexamers was linearly dependent on the genomic G+C content. We found that species belonging to Proteobacteria, Bacteroidetes and Actinobacteria (including bifidobacteria) carried high counts of GTCGTT, the optimal motif stimulating human TLR9. We also found that Enterococcus faecalis, Lactobacillus casei, Lactobacillus plantarum and Lactobacillus rhamnosus, whose strains have been marketed as probiotics, had high counts of GTCGTT motifs. As gut bacterial species differ significantly in their genomic content of CpG motifs, the overall load of CpG motifs in the intestine depends on the species assembly of microbiota and their cell numbers. The optimal CpG motif content of microbiota may depend on the host's physiological status and, consequently, on an adequate level of TLR9 signalling. We speculate that microbiota with increased numbers of microbes with CpG motif-rich DNA could better support mucosal functions in healthy individuals and improve the T-helper 1 (Th1)/Th2 imbalance in allergic diseases. In autoimmune disorders, CpG motif-rich DNA could, however, further increase the Th1-type immune responsiveness. Estimation of the load of microbe-associated molecular patterns, including CpG motifs, in gut microbiota could shed new light on host-microbe interactions across a range of diseases.

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.

In vitro effects of CpG oligodeoxynucleotides delivered by gelatin nanoparticles on canine peripheral blood mononuclear cells of atopic and healthy dogs - a pilot study

BACKGROUND

Cytosine-phosphate-guanine (CpG) oligodeoxynucleotides offer a novel promising immunotherapeutic approach for atopic dermatitis (AD) both in humans and animals. Gelatin nanoparticles (GNP) enhance and prolong CpG-associated immunomodulatory effects and minimize adverse effects both in vitro and in vivo. Information about the effects of this combination in dogs is lacking.

HYPOTHESIS/OBJECTIVES

The aim of this study was to evaluate immunological effects of CpG coupled to GNP on canine peripheral blood mononuclear cells (PBMCs) in vitro.

ANIMALS

Eight dogs with AD, diagnosed by standard criteria and with a concurrent immediate hypersensitivity to house dust mites were included. Control samples were taken from eight healthy, age-matched control dogs without history or evidence of cutaneous or systemic illness.

METHODS

Peripheral blood mononuclear cells of healthy and allergic dogs were incubated with CpG-GNP and the uptake of CpG-GNP was demonstrated using confocal laser scanning microscopy. Cell culture supernatant concentrations of interferon gamma (IFN-γ), interleukin (IL)-4, IL-6 and IL-10 were measured by Canine Cytokine Milliplex.

RESULTS

No significant changes in IFN-γ and IL-4 were found when comparing PBMCs incubated with CpG and CpG-GNP with the negative controls in atopic and healthy dogs. Interleukin-6 was not detected in any of the groups. However, a statistically significant increase in IL-10 concentration was found after 24 h stimulation with CpG-GNP compared with CpG alone both in atopic and healthy dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

As IL-10 is considered an immunosuppressive cytokine playing a key role in peripheral tolerance; the reported CpG-GNP formulation could be a new approach in allergy treatment.

CpG adjuvant enhances the mucosal immunogenicity and efficacy of a Treponema pallidum DNA vaccine in rabbits

OBJECTIVES

The protective response against Treponema pallidum (Tp) infection of a DNA vaccine enhanced by an adjuvant CpG ODN was investigated.

RESULTS

The mucosal adjuvant CpG ODN enhanced the production of higher levels of anti-TpGpd antibodies induced by pcD/Gpd-IL-2 in rabbits. It also resulted in higher levels of secretion of IL-2 and IFN-γ, and facilitated T cell proliferation and differentiation (p<0.05). No significant difference about testing index above-mentioned was found in the intranasal immunization group of pcD/Gpd-IL-2 vaccine adjuvanted by CpG ODN when compared with the immunization by pcD/Gpd-IL-2 vaccine intramuscular injection alone (p>0.05). Furthermore, CpG ODN stimulated the production of mucosa-specific anti-sIgA antibodies and resulted in the lowest Tp-positive rate (6.7%) for Tp-infection of skin lesions and the lowest rates (8.3%) of ulceration lesions, thus achieving better protective effects.

METHODS

New Zealand rabbits were immunized with the eukaryotic vector encoding recombinant pcD/Gpd-IL-2 using intramuscular multi-injection or together with mucosal enhancement via a nasal route. The effect of the mucosal adjuvant CpG ODN was examined.

CONCLUSIONS

The CpG ODN adjuvant significantly enhances the humoral and cellular immune effects of the immunization by pcD/Gpd-IL-2 with mucosal enhancement via nasal route. It also stimulates strong mucosal immune effects, thus initiating more efficient immune-protective effects.

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.

Pathology and pathophysiology of inhalational anthrax in a guinea pig model

Nonhuman primates (NHPs) and rabbits are the animal models most commonly used to evaluate the efficacy of medical countermeasures against anthrax in support of licensure under the FDA's "Animal Rule." However, a need for an alternative animal model may arise in certain cases. The development of such an alternative model requires a thorough understanding of the course and manifestation of experimental anthrax disease induced under controlled conditions in the proposed animal species. The guinea pig, which has been used extensively for anthrax pathogenesis studies and anthrax vaccine potency testing, is a good candidate for such an alternative model. This study was aimed at determining the median lethal dose (LD50) of the Bacillus anthracis Ames strain in guinea pigs and investigating the natural history, pathophysiology, and pathology of inhalational anthrax in this animal model following nose-only aerosol exposure. The inhaled LD50 of aerosolized Ames strain spores in guinea pigs was determined to be 5.0 × 10(4) spores. Aerosol challenge of guinea pigs resulted in inhalational anthrax with death occurring between 46 and 71 h postchallenge. The first clinical signs appeared as early as 36 h postchallenge. Cardiovascular function declined starting at 20 h postexposure. Hematogenous dissemination of bacteria was observed microscopically in multiple organs and tissues as early as 24 h postchallenge. Other histopathologic findings typical of disseminated anthrax included suppurative (heterophilic) inflammation, edema, fibrin, necrosis, and/or hemorrhage in the spleen, lungs, and regional lymph nodes and lymphocyte depletion and/or lymphocytolysis in the spleen and lymph nodes. This study demonstrated that the course of inhalational anthrax disease and the resulting pathology in guinea pigs are similar to those seen in rabbits and NHPs, as well as in humans.

Intraocular vaccination with an inactivated highly pathogenic avian influenza virus induces protective antibody responses in chickens

Because it is expected to induce cross-reactive serum and mucosal antibody responses, mucosal vaccination against highly pathogenic avian influenza (HPAI) is potentially superior to conventional parenteral vaccination. Here, we tested whether intraocular vaccination with an inactivated AI virus induced protective antibody responses in chickens. Chickens were inoculated intraocularly twice with 10(4) hemagglutination units of an inactivated H5N1 HPAI virus. Four weeks after the second vaccination, the chickens were challenged with a lethal dose of the homologous H5N1 HPAI virus. Results showed that most of the vaccinated chickens mounted positive antibody responses. The median serum hemagglutination inhibition titer was 1:80. Addition of CpG oligodeoxynucleotide 2006 or cholera toxin to the vaccine did not enhance serum antibody titers. Cross-reactive anti-hemagglutinin IgG, but not IgA, was detected in oropharyngeal secretions. In accordance with these antibody results, most vaccinated chickens survived a lethal challenge with the H5N1 HPAI virus and did not shed the challenge virus in respiratory or digestive tract secretions. Our results show that intraocular vaccination with an inactivated AI virus induces not only systemic but also mucosal antibody responses and confers protection against HPAI in chickens.

Stimulation with a class A CpG oligonucleotide enhances resistance to infection with feline viruses from five different families

Domestic cats are commonly affected by viral pathogens that induce lengthy infections with fatal outcomes. Prevention of viral propagation is of primordial importance in shelters and catteries, where cats from different backgrounds have narrow contacts. Oligonucleotides (ODN) containing cytosine-phosphate-guanosine motifs of class A (CpG-A) are highly potent synthetic inducers of innate antiviral mechanisms. The aim of this study was to test their ability to modulate innate immune responses and prevent viral replication as stand-alone agents in the domestic cat. CpG-A stimulation of feline peripheral blood mononuclear cells (PBMCs) enhanced their proliferation, increased the presence of co-stimulatory molecules on their surface and influenced their gene expression profiles in an antiviral orientation. Incubation of the supernatants of CpG-A stimulated PBMCs with feline cell lines of epithelial and fibroblastic origin induced expression of the antiviral myxovirus resistance (Mx) gene in these target cells, which also showed enhanced resistance to feline viruses from five distinct families, namely Coronaviridae, Herpesviridae, Caliciviridae, Parvoviridae, and Retroviridae. Most importantly, subcutaneous administration of CpG-A in domestic cats systemically increased the expression of Mx, reaching maximal levels within 24 h. Plasma from treated cats could furthermore inhibit viral replication in vitro. Altogether, our data highlight the promising potential of CpG-A to induce a preventive antiviral state in the cat and to protect feline populations against a broad range of virus infections.

CpG-enriched plasmid enhances the efficacy of the traditional foot-and-mouth disease killed vaccine

A CpG-enriched recombinant plasmid (pUC18-CpG) as an adjuvant of FMD killed vaccine was tested for immunization and vaccination challenge in a porcine model. Our preliminary results had indicated that the recombinant plasmid could enhance the humoral immune response triggered by the traditional oil-adjuvant vaccine after the initial inoculation. A subsequent vaccination-challenge test showed an increased PD(50) value. Thus, coadministration of the recombinant plasmid with the oil-adjuvant vaccine helped illicit an immune response earlier than that elicited by giving the vaccine alone. Our results showed that pUC18-CpG can be a potent immunoadjuvant for the traditional FMD killed vaccine and can greatly enhance the traditional vaccine's efficacy when given in combination with it.