A study on the protective effects of CpG oligodeoxynucleotide-induced mucosal immunity against lung injury in a mouse acute respiratory distress syndrome model

This study aims to determine the feasibility of using oligodeoxynucleotides with unmethylated cytosine-guanine dinucleotide sequences (CpG ODN) as an immunity protection strategy for a mouse model of acute respiratory distress syndrome (ARDS). This is a prospective laboratory animal investigation. Twenty-week-old BALB/c mice in Animal research laboratory were randomized into groups. An ARDS model was induced in mice using lipopolysaccharides (LPSs). CpG ODN was intranasally and transrectally immunized before or after the 3rd and 7th days of establishing the ARDS model. Mice were euthanized on Day 7 after the second immunization. Then, retroorbital bleeding was carried out and the chest was rapidly opened to collect the trachea and tissues from both lungs for testing. CpG ODN significantly improved the pathologic impairment in mice lung, especially after the intranasal administration of 50 μg. This resulted in the least severe lung tissue injury. Furthermore, interleukin-6 (IL-6) and IL-8 concentrations were lower, which was second to mice treated with the rectal administration of 20 µg CpG ODN. In contrast, the nasal and rectal administration of CpG ODN in BALB/c mice before LPS immunization did not appear to exhibit any significant protective effects. The intranasal administration of CpG ODN may be a potential treatment approach to ARDS. More studies are needed to further determine the protective mechanism of CpG ODN.

Generation and characterization of a monoclonal antibody against MERS-CoV targeting the spike protein using a synthetic peptide epitope-CpG-DNA-liposome complex

Middle East respiratory syndrome coronavirus (MERS-CoV) uses the spike (S) glycoprotein to recognize and enter target cells. In this study, we selected two epitope peptide sequences within the receptor binding domain (RBD) of the MERS-CoV S protein. We used a complex consisting of the epitope peptide of the MERS-CoV S protein and CpG-DNA encapsulated in liposome complex to immunize mice, and produced the monoclonal antibodies 506-2G10G5 and 492-1G10E4E2. The western blotting data showed that both monoclonal antibodies detected the S protein and immunoprecipitated the native form of the S protein. Indirect immunofluorescence and confocal analysis suggested strong reactivity of the antibodies towards the S protein of MERS-CoV virus infected Vero cells. Furthermore, the 506-2G10G5 monoclonal antibody significantly reduced plaque formation in MERS-CoV infected Vero cells compared to normal mouse IgG and 492-1G10E4E2. Thus, we successfully produced a monoclonal antibody directed against the RBD domain of the S protein which could be used in the development of diagnostics and therapeutic applications in the future. [BMB Reports 2019; 52(6): 397-402].

Effects of skeletal unloading on the antibody repertoire of tetanus toxoid and/or CpG treated C57BL/6J mice

Spaceflight affects the immune system, but the effects on the antibody repertoire, responsible for humoral immunity, has not been well explored. In particular, the complex gene assembly and expression process; including mutations, might make this process vulnerable. Complementarity determining region 3 (CDR3), composed of parts of the V-(D-)J-gene segments, is very important for antigen binding and can be used as an important measure of variability. Skeletal unloading, and the physiological effects of it, parallel many impacts of space flight. Therefore, we explored the impact of skeletal unloading using the antiorthostatic suspension (AOS) model. Animals were experimentally challenged with tetanus toxoid (TT) and/or the adjuvant CpG. Blood was analyzed for anti-TT antibody and corticosterone concentrations. Whole spleen tissue was prepared for repertoire characterization. AOS animals showed higher levels of corticosterone levels, but AOS alone did not affect anti-TT serum antibody levels. Administration of CpG significantly increased the circulating anti-TT antibody concentrations. AOS did alter constant gene usage resulting in higher levels of IgM and lower levels of IgG. CpG also altered constant gene region usage increasing usage of IgA. Significant changes could be detected in multiple V-, D-, and J-gene segments in both the heavy and light chains in response to AOS, TT, and CpG treatments. Analysis of class-switched only transcripts revealed a different pattern of V-gene segment usage than detected in the whole repertoire and also showed significant alterations in gene segment usage after challenge. Alterations in V/J pairing were also detected in response to challenge. CDR3 amino acid sequence overlaps were similar among treatment groups, though the addition of CpG lowered overlap in the heavy chain. We isolated 3,045 whole repertoire and 98 potentially TT-specific CDR3 sequences for the heavy chain and 569 for the light chain. Our results demonstrate that AOS alters the repertoire response to challenge with TT and/or CpG.

Non-small-cell lung cancer-induced immunosuppression by increased human regulatory T cells via Foxp3 promoter demethylation

Patients with non-small-cell lung cancer (NSCLC) have immune defects that are poorly understood. Forkhead box protein P3 (Foxp3) is crucial for immunosuppression by CD4(+) regulatory T cells (Tregs). It is not well known how NSCLC induces Foxp3 expression and causes immunosuppression in tumor-bearing patients. Our study found a higher percentage of CD4(+) Tregs in the peripheral blood of NSCLC compared with healthy donors. NSCLC patients showed demethylation of eight CpG sites within the Foxp3 promoter with methylation ratios negatively correlated with CD4(+)CD25(+)Foxp3(+) T levels. Foxp3 expression in CD4(+) Tregs was directly regulated by Foxp3 promoter demethylation and was involved in immunosuppression by NSCLC. To verify the effect of tumor cells on the phenotype and function of CD4(+) Tregs, we established a coculture system using NSCLC cell line and healthy CD4(+) T cells and showed that SPC-A1 induced IL-10 and TGF-β1 secretion by affecting the function of CD4(+) Tregs. The activity of DNA methyltransferases from CD4(+) T was decreased during this process. Furthermore, eight CpG sites within the Foxp3 promoter also appeared to have undergone demethylation. Foxp3 is highly expressed in CD4(+) T cells, and this may be caused by gene promoter demethylation. These induced Tregs are highly immunosuppressive and dramatically inhibit the proliferative activity of naïve CD4(+) T cells. Our study provides one possible mechanism describing Foxp3 promoter demethylation changes by which NSCLC down-regulates immune responses and contributes to tumor progression. Foxp3 represents an important target for NSCLC anti-tumor immunotherapy.

Importance of Toll-like receptors for B lymphocyte survival in primary Sjögren's syndrome

The Sjögren's syndrome is a systemic autoimmune disease characterized by lymphocytic infiltration of the glands responsible for mouth and eyes dryness. A minority of infiltrating B cells is organized as germinal centers while the majority is aggregated into clusters of transitional and marginal zone B cells. The Toll-like receptor 9 (TLR9) recognizes microbial DNA but also, sometimes, the self DNA. It appears to be a key determinant of the survival and differentiation of B lymphocytes. After laser micro-dissection of B cells from salivary glands, analyses by quantitative RT-PCR showed that transitional B cells express high level of TLR9 mRNA unlike B cells from germinal centers. B lymphocytes from healthy donors were sorted by flow cytometry and stimulated in vitro with their TLR9. It induces survival, activation and proliferation associated with phenotypic changes. Transitional B cells exhibited characteristics of the marginal zone, whereas mature B cells expressed follicular germinal center specificities. Finally, IgM and IgG were secreted by both population, but with elevated production of autoantibodies by the transitional B cells. Increased expression of TLR9 by transitional B cells suggests that they may be highly sensitive to differentiate into autoantibody secreting cells through maturation into the marginal zone into the salivary glands. TLR9 might be a target for forthcoming biotherapies.

Design and development of nanosized DNA assemblies in polypod-like structures as efficient vehicles for immunostimulatory CpG motifs to immune cells

The immunostimulatory activity of phosphodiester DNA containing unmethylated cytosine-phosphate-guanine (CpG) dinucleotides, or CpG motifs, was significantly increased by the formation of Y-, X-, or dendrimer-like multibranched shape. These results suggest the possibility that the activity of CpG DNA is a function of the structural properties of branched DNA assemblies. To elucidate the relationship between them, we have designed and developed nanosized DNA assemblies in polypod-like structures (polypod-like structured DNA, or polypodna for short) using oligodeoxynucleotides (ODNs) containing CpG motifs and investigated their structural and immunological properties. Those assemblies consisting of three (tripodna) to eight (octapodna) ODNs were successfully obtained, but one consisting of 12 ODNs was not when 36-mer ODNs were annealed under physiological sodium chloride concentration. High-speed atomic force microscopy revealed that these assemblies were in polypod-like structures. The apparent size of the products was about 10 nm in diameter, and there was an increasing trend with an increase in ODN length or with the pod number. Circular dichroism spectral data showed that DNA in polypodna preparations were in the B-form. The melting temperature of polypodna decreased with increasing pod number. Each polypodna induced the secretion of tumor necrosis factor-α and interleukin-6 from macrophage-like RAW264.7 cells, with the greatest induction by those with hexa- and octapodna. Increasing the pod number increased the uptake by RAW264.7 cells but reduced the stability in serum. These results indicate that CpG DNA-containing polypodna preparations with six or more pods are a promising nanosized device with biodegradability and high immunostimulatory activity.

Phase I trial of Wilms' Tumor 1 (WT1) peptide vaccine with GM-CSF or CpG in patients with solid malignancy

BACKGROUND

The aim of this study was to investigate the safety and efficacy of combinatorial use of granulocyte-macrophage colony-stimulating factor (GM-CSF) and CpG oligodeoxynucleotides (CpG-ODN) as immunoenhancement adjuvants in Wilms' Tumor 1 (WT1) vaccine therapy for patients with solid malignancy.

PATIENTS AND METHODS

The patients were placed into treatment groups as follows: WT1 peptide alone, WT1 peptide with GM-CSF (100 μg) and WT1 peptide with CpG-ODN (100 μg). HLA-A *2402 or *0201/*0206-restricted, WT1 peptide emulsified with Montanide ISA51 was injected intradermally every week for eight weeks. Toxicities were evaluated according to the National Cancer Institute Common Terminology Criteria for Adverse Events ver. 3.0. Tumor size, which was measured by computed tomography, was determined every four weeks. The responses were analyzed according to Response Evaluation Criteria in Solid Tumors.

RESULTS

The protocol was well tolerated; only local erythema occurred at the WT1 vaccine injection site. The disease control rate of the groups treated with WT1 peptide alone (n=10), with combinatorial use of GM-CSF (n=8) and with combinatorial use of CpG-ODN (n=10), in the initial two months was 20%, 25% and 60%, respectively.

CONCLUSION

Addition of GM-CSF or CpG-ODN to the WT1 peptide vaccine for patients with solid malignancy was safe and improved the effectiveness of clinical response.

TREM-2, triggering receptor expressed on myeloid cell-2, negatively regulates TLR responses in dendritic cells

DCs play a key role in defense against infections and also in preventing inflammatory and autoimmune diseases. The response of DCs to pathogens is tightly regulated by many mechanisms to allow for appropriate, but not pathogenic, responses. We previously showed that DCs with deficiencies for two ITAM-bearing signaling adapters, DAP12 and FcRγ, produce more inflammatory cytokines upon treatment with Toll-like receptor (TLR) agonists than WT DCs. Here, we investigated whether the TREM-2 receptor pairs with DAP12 to inhibit TLR responses in DCs. TREM-2-deficient BMDCs showed increased inflammatory cytokine and type I IFN production in response to TLR ligation. Additionally, TREM-2-deficient BMDCs had increased TLR-induced maturation and were more efficient at inducing antigen-specific T-cell proliferation upon CpG DNA stimulation compared with WT BMDCs. Finally, we showed that a TREM-2 ligand is expressed on the surface of BMDCs, suggesting that the TREM-2 receptor transduces inhibitory signals due to recognition of an endogenous ligand.

Immunostimulation of bronchoalveolar lavage cells from recurrent airway obstruction-affected horses by different CpG-classes bound to gelatin nanoparticles

Recurrent airway obstruction (RAO) in horses has become a common problem in stabled horses in industrialized countries and deserves new therapeutic strategies. CpG-oligodeoxynucleotides (CpG-ODNs) were developed as effective immunostimulating agents to induce a Th2/Th1 shift. These agents showed a beneficial therapeutic effect in allergic diseases with predominant Th2 immunoresponse. CpG-ODN delivery by gelatin nanoparticles (GNPs) resulted in enhanced cellular uptake in murine and human in vitro studies and was a starting point for the present trial. The aim of this study was to identify an optimal stimulating CpG motif in horses with regard to species specificity on equine bronchoalveolar lavage (BAL) cells, in terms of a possible specific immunomodulation effect (Th2/Th1 shift) by used CpG-ODN. Accordingly, GNPs were evaluated as a delivery system to improve CpG-ODN immunostimulation in equine BAL cells. BAL fluid (BALF) was obtained from seven horses with moderate RAO and from four healthy horses and was subsequently incubated with five different CpG-ODN sequences (from A-, B- and C-class) and one ODN without any CpG motif. Release of three key cytokines (IL-4, IL-10 and IFN-γ) was quantified by ELISA to detect an allergy mediated Th2 immunoresponse (IL-4) as well as a proinflammatory Th1 response (IFN-γ). Due to its specific anti-inflammatory and anti-allergic effects, IL-10 was considered as a beneficial agent in pathophysiology of RAO. Results showed a significant upregulation of IL-10 and IFN-γ on the one hand and a downregulation of IL-4 on the other hand in RAO affected horses. Cell cultures from healthy horses had a significantly stronger response in cytokine release to all the applied stimuli in contrast to RAO derived cells. Comparing all five CpG sequences, A-class 2216 significantly showed the highest immunomodulatory effects on equine BALF cells and, hence, was chosen for follow-up preliminary clinical studies.

Different pathological roles of toll-like receptor 9 on mucosal B cells and dendritic cells in murine IgA nephropathy

Although pathogenesis of IgA nephropathy (IgAN) is still obscure, pathological contribution of mucosal immunity including production of nephritogenic IgA and IgA immune complex (IC) has been discussed. We have reported that mucosal toll-like receptor (TLR)-9 is involved in the pathogenesis of human and murine IgAN. However, cell-type expressing TLR9 in mucosa remains unclear. To address this, we nasally challenged cell-specific CpG DNA ((i): dendritic cell: (DC), (ii): B cell, (iii): both), known as ligand for TLR9, to IgAN prone mice and analyzed disease phenotype of each group. After 8 times of the weekly administration, every group showed deterioration of glomerular damage. However, CpG-A-group showed clear extension of mesangial proliferative lesions with increase of serum IgA-IgG2a IC and its glomerular depositions, while CpG-B-group showed extent of glomerular sclerotic lesions with increase of serum and glomerular IgA and M2 macrophage infiltration. Present results indicate that mucosal TLR9 on B cells and DC may differently contribute to the progression of this disease via induction of nephritogenic IgA or IgA-IgG IC, respectively. This picture is suggestive for the pathological difference between child and adult IgAN.

Antibody against extracellular vaccinia virus (EV) protects mice through complement and Fc receptors

Protein-based subunit smallpox vaccines have shown their potential as effective alternatives to live virus vaccines in animal model challenge studies. We vaccinated mice with combinations of three different vaccinia virus (VACV) proteins (A33, B5, L1) and examined how the combined antibody responses to these proteins cooperate to effectively neutralize the extracellular virus (EV) infectious form of VACV. Antibodies against these targets were generated in the presence or absence of CpG adjuvant so that Th1-biased antibody responses could be compared to Th2-biased responses to the proteins with aluminum hydroxide alone, specifically with interest in looking at the ability of anti-B5 and anti-A33 polyclonal antibodies (pAb) to utilize complement-mediated neutralization in vitro. We found that neutralization of EV by anti-A33 or anti-B5 pAb can be enhanced in the presence of complement if Th1-biased antibody (IgG2a) is generated. Mechanistic differences found for complement-mediated neutralization showed that anti-A33 antibodies likely result in virolysis, while anti-B5 antibodies with complement can neutralize by opsonization (coating). In vivo studies found that mice lacking the C3 protein of complement were less protected than wild-type mice after passive transfer of anti-B5 pAb or vaccination with B5. Passive transfer of anti-B5 pAb or monoclonal antibody into mice lacking Fc receptors (FcRs) found that FcRs were also important in mediating protection. These results demonstrate that both complement and FcRs are important effector mechanisms for antibody-mediated protection from VACV challenge in mice.

[Delayed appearance of hypertension in spontaneously hypertensive rat (SHR) injected with CpG-rich DNA early in ontogenesis]

In this study we have investigated properties of blood serum extracellular DNA (cell-free DNA) from patients with essential arterial hypertension (AH). Cell-free DNA concentration was not changed in the control AH group compared to norma (healthy donors) but fragments of CpG-rich cell-free DNA marker content were increased at transcribed area of ribosomal repeat (TArDNA, CpG-DNA). To evaluate effect of CpG-DNA on AH development in 2-day SHR line and in control normotensive line (WKY), 700 ng of human TArDNA single subcutaneous injection were inoculated to obtain anti-CpG-DNA polyclonal antibodies. These antibodies could change CpG-DNA contents in total cell-free DNA. Blood pressure (BP) in 9-week SHR line rats immunized with CpG-DNA was equal to BP of WKY rats. Then BP of immunized SHR steadily increased with age and reached high value 8 weeks later compared to control SHR rats. Cell-free DNA analysis in 17-week SHR line rats showed significantly reduced concentrations of cell-free DNA and also showed decrease in small DNA fragments content, but increased content of CpG-DNA (rat TArDNA). These changes were accompanied with 3.5-fold blood endonuclease activity increase and decrease of free (unbound to cell-free DNA) anti-CpG-DNA antibodies quantity. Total anti-CpG-DNA antibodies quantity in immunized rats wasn't changed compared to control animals. Thus, observed effect of increase in stable BP elevation age in immunized SHR line rats doesn't relate to increase of anti-CpG-DNA antibody production. Possible reason of this effect is further discussed.

IVIg attenuates TLR-9 activation in B cells from SLE patients

INTRODUCTION

Toll-like receptor-9 (TLR-9) plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). The aim of this study was to evaluate the influence of intravenous immunoglobulin (IVIg) on CpG oligodeoxynucleotides (ODN-CpG) activated B cells from SLE patients.

METHODS

Peripheral blood B cells were isolated from 16 SLE patients and 21 healthy age-matched controls. B cells were cultured with ODN-CpG 1μM alone or IVIg (10mg/ml) together with ODN-CpG. After 24-h incubation, B cells and supernatants were collected and analyzed for interleukin (IL)-10, IL-6 secretion, and TLR-9 expression.

RESULTS

IVIg decreased the secretion of IL-10 from ODN-CpG-activated B cells isolated from both SLE patients and healthy controls (194 ± 46.2 to 103.2 ± 27.13 pg/ml, p < 0.016, 153.2 ± 19 vs 84.6 ± 7.5, p < 0.0001, respectively). Similarly, IVIg decreased the secretion of IL-6 from ODN-CpG-activated B cell isolated from both SLE patients and healthy controls (431.2 ± 83 to 307.6 ± 94.3 pg/ml, p < 0.0008, 319.5 ± 31 vs 193.3 ± 22.8, p < 0.0001, respectively). The decrement of IL-10 and IL-6 secretion was associated with a significant decrease in TLR-9 expression in memory B cells from SLE patients and healthy controls (11.47 ± 1.2 vs 13.29 ± 1.2, p = 0.005, 11 ± 0.8 vs 12.8 ± 0.98, p = 0.0016, respectively).

CONCLUSIONS

IVIg attenuates the activation of TLR-9 in B cells from SLE patients, suggesting a novel additional mechanism of IVIg mode of action in these patients.

[New approaches for allergen-specific immunotherapy]

Rates of allergic diseases such as asthma and rhinitis are on the rise as important health problems in every country of the world. Allergen specific immunotherapy with natural allergenic extracts is a treatment directed to changing the natural course of these diseases, and is a treatment that has reported beneficial effects in a majority of allergic patients. However, this treatment is difficult because of the complex composition of the extracts. The composition is difficult to standardize and, consequently, the risk of anaphylactic shock is increased; furthermore, sensitization can occur to other antigens present in the extract. Therefore, new allergen specific immunotherapy approaches are needed. Chemically defined and standardized antigens are more easily managed and provide a safer and more efficient treatment. Vaccines for immunotherapy have already been designed, based on recombinant allergens, variants (or peptides derived from them), that can be administrated alone or in combination with adjutants. Some of these preparations are indicated for facilitating the uptake and antigenic presentation by dendritic cells, or by targeting the mast cells and basophiles. Studies in vitro, in animal models and clinical trials in allergic patients, indicate that these preparations may provide protection against the allergen exposure and improve the symptoms by inducing the production of blocking antibodies of the IgE mediated response, production of regulator T cells and cytokines of Th1 profile.

No evidence for an effect of DNA methylation on multiple sclerosis severity at HLA-DRB1*15 or HLA-DRB5

Multiple sclerosis (MS) is a complex neurological disease with huge variability in disease outcome. The majority of MS genetic susceptibility is determined by major histocompatibility complex (MHC) alleles, in particular haplotypes carrying HLA-DRB1*1501. HLA-DRB1*1501 also affects the clinical outcome of the disease and animal research has suggested that HLA-DRB5 interacts with HLA-DRB1*1501 to influence disease severity. We used an extremes-of-outcome design with 48 benign and 20 malignant MS patients to assess whether or not DNA methylation at HLA-DRB1*1501 and/or HLA-DRB5 also contributes to MS phenotypic heterogeneity. We found no significant effect of DNA methylation across HLA-DRB1*1501 and HLA-DRB5 on severity, although we cannot rule out time- or tissue-specific effects of DNA methylation.

B cell activation by outer membrane vesicles--a novel virulence mechanism

Secretion of outer membrane vesicles (OMV) is an intriguing phenomenon of Gram-negative bacteria and has been suggested to play a role as virulence factors. The respiratory pathogens Moraxella catarrhalis reside in tonsils adjacent to B cells, and we have previously shown that M. catarrhalis induce a T cell independent B cell response by the immunoglobulin (Ig) D-binding superantigen MID. Here we demonstrate that Moraxella are endocytosed and killed by human tonsillar B cells, whereas OMV have the potential to interact and activate B cells leading to bacterial rescue. The B cell response induced by OMV begins with IgD B cell receptor (BCR) clustering and Ca(2+) mobilization followed by BCR internalization. In addition to IgD BCR, TLR9 and TLR2 were found to colocalize in lipid raft motifs after exposure to OMV. Two components of the OMV, i.e., MID and unmethylated CpG-DNA motifs, were found to be critical for B cell activation. OMV containing MID bound to and activated tonsillar CD19(+) IgD(+) lymphocytes resulting in IL-6 and IgM production in addition to increased surface marker density (HLA-DR, CD45, CD64, and CD86), whereas MID-deficient OMV failed to induce B cell activation. DNA associated with OMV induced full B cell activation by signaling through TLR9. Importantly, this concept was verified in vivo, as OMV equipped with MID and DNA were found in a 9-year old patient suffering from Moraxella sinusitis. In conclusion, Moraxella avoid direct interaction with host B cells by redirecting the adaptive humoral immune response using its superantigen-bearing OMV as decoys.

Epigenetic mechanisms of regulation of Foxp3 expression

Regulatory T cells play important roles in the control of autoimmunity and maintenance of transplantation tolerance. Foxp3, a member of the forkhead/winged-helix family of transcription factors, acts as the master regulator for regulatory T-cell (Treg) development and function. Mutation of the Foxp3 gene causes the scurfy phenotype in mouse and IPEX syndrome (immune dysfunction, polyendocrinopathy, enteropathy, X-linked syndrome) in humans. Epigenetics is defined by regulation of gene expression without altering nucleotide sequence in the genome. Several epigenetic markers, such as histone acetylation and methylation, and cytosine residue methylation in CpG dinucleotides, have been reported at the Foxp3 locus. In particular, CpG dinucleotides at the Foxp3 locus are methylated in naive CD4+CD25- T cells, activated CD4+ T cells, and TGF-beta-induced adaptive Tregs, whereas they are completely demethylated in natural Tregs. The DNA methyltransferases DNMT1 and DNMT3b are associated with the Foxp3 locus in CD4+ T cells. Methylation of CpG residues represses Foxp3 expression, whereas complete demethylation is required for stable Foxp3 expression. In this review, we discuss how different cis-regulatory elements at the Foxp3 locus are subjected to epigenetic modification in different subsets of CD4+ T cells and regulate Foxp3 expression, and how these mechanisms can be exploited to generate efficiently large numbers of suppressive Tregs for therapeutic purposes.

Immune Mechanisms and Therapeutic Potential of CpG Oligodeoxynucleotides

Unmethylated CpG motifs in bacterial DNA and synthetic oligodeoxynucleotides activate immune cells that express Toll-like Receptor 9. Activation through this receptor triggers cellular signaling that leads to production of a proinflammatory and a Th1-type, antigen-specific immune response. The immunostimulatory effects of CpG oligodeoxynucleotides confer protection against infectious disease, allergy and cancer in animal models, and clinical trials have been initiated. However, CpG oligodeoxynucleotides may exacerbate disease in some situations. We will review current concepts in the mechanisms of activating Toll-like Receptor 9 with CpG oligodeoxynucleotides and highlight opportunities for using large animal models to better determine the mechanisms of action.

Vector transmission of leishmania abrogates vaccine-induced protective immunity

Numerous experimental vaccines have been developed to protect against the cutaneous and visceral forms of leishmaniasis caused by infection with the obligate intracellular protozoan Leishmania, but a human vaccine still does not exist. Remarkably, the efficacy of anti-Leishmania vaccines has never been fully evaluated under experimental conditions following natural vector transmission by infected sand fly bite. The only immunization strategy known to protect humans against natural exposure is “leishmanization,” in which viable L. major parasites are intentionally inoculated into a selected site in the skin. We employed mice with healed L. major infections to mimic leishmanization, and found tissue-seeking, cytokine-producing CD4+ T cells specific for Leishmania at the site of challenge by infected sand fly bite within 24 hours, and these mice were highly resistant to sand fly transmitted infection. In contrast, mice vaccinated with a killed vaccine comprised of autoclaved L. major antigen (ALM)+CpG oligodeoxynucleotides that protected against needle inoculation of parasites, showed delayed expression of protective immunity and failed to protect against infected sand fly challenge. Two-photon intra-vital microscopy and flow cytometric analysis revealed that sand fly, but not needle challenge, resulted in the maintenance of a localized neutrophilic response at the inoculation site, and removal of neutrophils following vector transmission led to increased parasite-specific immune responses and promoted the efficacy of the killed vaccine. These observations identify the critical immunological factors influencing vaccine efficacy following natural transmission of Leishmania.

The generation of vaccines that protect against intracellular pathogens such as malaria, human immunodeficiency virus and leishmaniasis have met with limited success. A perplexing aspect of this failure as it relates to leishmaniasis is the knowledge that individuals typically get the disease only once, and that individuals who are experimentally infected with cultured parasites are protected against sand fly transmitted infection, thereby providing a “gold standard” for vaccine design. Many engineered, non-living vaccines have been developed to mimic the immune response observed in protected individuals and some of these have been shown to provide excellent protection against needle inoculation of Leishmania parasites in mice. However, very similar vaccine formulations adapted for use in people have failed to protect against natural exposure to infected sand fly bites. In the present study, we attempt to reconcile these long-standing differences, and to provide the critical correlates of immunity that will predict vaccination success against natural exposure.

A single-dose combination therapy that both prevents and treats anthrax infection

Exposure to anthrax leaves susceptible hosts at prolonged risk of infection since spores can persist in vivo for months before germinating to cause life-threatening disease. Anthrax vaccine adsorbed (AVA, the licensed US vaccine) induces immunity too slowly to protect susceptible individuals post-exposure. Antibiotics prevent the proliferation of vegetative bacilli but do not block latent spores from germinating. Thus, anthrax-exposed individuals must remain on antibiotic therapy for months to eliminate the threat posed by delayed spore germination. Unfortunately, long-term antibiotic treatment is poorly tolerated and frequently discontinued. This work explores whether administering a single dose of a long-acting antibiotic (Dalbavancin) combined with a rapidly immunogenic vaccine/adjuvant combination can provide seamless protection from anthrax with minimal patient compliance. Results show that significant protection is achieved by delivering a single dose of this therapeutic combination any time before through 3 days after anthrax exposure.

CpG-ODN increases resistance of olive flounder (Paralichthys olivaceus) against Philasterides dicentrarchi (Ciliophora: Scuticociliatia) infection

Unmethylated cytosine-phosphate-guanine (CpG) dinucleotides flanked by specific bases in bacterial DNA induce a favorable immune response by acting as danger signals to the host. Synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODNs) also act like the unmethylated CpG oligonucleotides in bacterial DNA. In the present study, we investigated the effects of synthetic CpG-ODN on the protection of olive flounder (Paralichthys olivaceus) against infection by Philasterides dicentrarchi, a pathogen of scuticociliatosis, through two consecutive experiments (trial I and II). Fish were intraperitoneally (i.p.) injected with CpG-ODN 1668 or GpC-ODN 1720 at different doses (3 microg in trial I and 10 microg in trial II), and after one week the fish were i.p. challenged with P. dicentrarchi. In both trial I and II, fish injected with CpG-ODN 1668 showed significantly higher serum scuticocidal activity than fish injected with PBS alone, while the scuticocidal activity disappeared by heat-inactivation. This result suggests that CpG-ODN might activate an alternative pathway of complement of olive flounder, and complement-mediated killing might be an important innate immune factor in the resistance against P. dicentrarchi infection. Although the cumulative mortality was largely different between trials I and II, the relative survival rate of fish injected with a high dose of CpG-ODN 1668 was considerably higher than that of fish injected with a low dose of this ODN, while the relative survival rate was not different between fish injected with the high dose and low dose of GpC-ODN 1720. The results of the present study suggest that CpG-ODNs may be used as potential immunostimulants to lessen cultured fish loss caused by scuticociliates.

DNA motifs suppressing TLR9 responses

Immune cells respond to bacterial DNA containing unmethylated CpG motifs via Toll-like receptor 9 (TLR9). Given the apparent role of TLR9 in development of systemic lupus erythematosus (SLE), there is interest in the development of TLR9 inhibitors. TLR9-mediated responses are reported to be inhibited by a confusing variety of different DNA sequences and structures. To aid characterization, we have provisionally categorized TLR9-inhibitory oligodeoxynucleotides (ODN) into 4 classes, on the basis of sequence and probable mode of action. Class I are short G-rich ODN, which show sequence-specific inhibition of all TLR9 responses, and may be direct competitive inhibitors for DNA binding to TLR9. Class II are telomeric repeat motifs that inhibit STAT signaling, and thus are not specific to TLR9 responses. Because Class II ODN are generally made as 24-base phosphorothioate-modified ODN (PS-ODN), they also fall into Class IV, defined as long PS-ODN, which inhibit TLR9 responses in a sequence-nonspecific manner. Class III includes oligo (dG) that forms a 4-stranded structure and inhibits DNA uptake. The Class I G-rich motifs show the most promise as selective and potent TLR9 inhibitors for therapeutic applications.

Initiation of signal transduction of the respiratory burst of prawn haemocytes triggered by CpG oligodeoxynucleotides

Phagocytosis is important in the immune system of the prawn and is believed to be a defence parameter. Previous studies have demonstrated that CpG oligonucleotides enhance the activation of the prophenoloxidase activating system of the prawn through either the G-protein/protein kinase C (PKC) or the cAMP pathway. This study investigated the influence of CpG ODN on the respiratory burst used as the indicator of phagocytic activity and on the initiation of the signal pathway in haemocytes of Macrobrachium rosenbergii. When haemocytes were treated in vitro with 50 microg ml(-1) of ODN2006 for 15 min, the increase of nitroblue-tetrazolium (NBT) reduction suggested that the respiratory burst of haemocytes can be enhanced by ODN2006 stimulation. In an attempt to determine which signal transduction pathway is involved in the enhancement effect, haemocytes were separately treated with activators or inhibitors of specific signalling components. The results showed that the NBT reduction of haemocytes increased after treatment with sodium fluoride (a G-protein activator) and decreased after treatment with GDP-beta-S (a G-protein inhibitor). When ODN2006-stimulated haemocytes were treated with GDP-beta-S, the inductive effect was significantly reduced. In haemocytes treated with 8-bromo-cAMP (a PKA activator), the NBT reduction was not significantly different from the control. The addition of phosphodiesterase-inhibiting caffeine, which inhibits the degradation of cAMP, decreased the NBT reduction of ODN2006-stimulated haemocytes; however, the addition of phenol-12-myristate-13-acetate (PMA) significantly increased the NBT reduction. When PMA-stimulated haemocytes were treated with chelerythrine (a PKC inhibitor), the induced NBT reduction was significantly reduced. Furthermore, the study of ODN2006-stimulated haemocytes treated with chelerythrine showed that the enhancement effect of ODN2006 on the NBT reduction was significantly decreased. All results suggest that the enhancement of the respiratory burst of prawn haemocytes is induced by ODN2006 via a PKC-activating signalling pathway, but negatively regulated via the cAMP pathway.

Human blood dendritic cells from allergic subjects have impaired capacity to produce interferon-alpha via Toll-like receptor 9

BACKGROUND

High-affinity IgE receptor (Fc epsilon RI) expression on blood dendritic cells reportedly correlates with serum IgE levels. Our studies demonstrate that plasmacytoid dendritic cells (pDCs) secrete pro-inflammatory cytokines (IL-6, TNF-alpha) following Fc epsilon RI stimulation - a mode of activation that simultaneously reduces expression of Toll-like receptor 9 (TLR9). Whether or not TLR9 and/or Fc epsilon RI levels and their function on dendritic cells relate to allergic status is unknown.

OBJECTIVE

The aim of this study is to compare the innate (TLR9-mediated) immune response of human pDCs to TLR9 and Fc epsilon RI alpha receptor expression in allergic and non-allergic subjects.

METHODS

Basophil-depleted mononuclear cell fractions containing pDCs were prepared from peripheral blood of allergic and non-allergic subjects. Intracellular TLR9 and surface Fc epsilon RI alpha expression in blood dendritic cell antigen-2-positive cells were determined by flow cytometry. Activating anti-IgE antibody, anti-Fc epsilon RI alpha antibody, and TLR9 agonist were used to stimulate cell suspensions, with cytokine levels determined by ELISA.

RESULTS

No difference in the frequency of pDCs was detected among allergic (n=9) vs. non-allergic (n=11) subjects (P=0.261). While there was also no difference in the baseline expression of TLR9, pDCs from allergic subjects produced sixfold less IFN-alpha when stimulated with CpG (P=0.002). Conversely, there was higher Fc epsilon RI alpha expression (P=0.01) on the pDCs of allergic subjects.

CONCLUSIONS

Impaired TLR9-dependent immune responses in human pDCs are associated with allergic status and inversely correlated with Fc epsilon RI alpha expression. This impaired innate immune response among dendritic cells of allergic subjects may lead to more targeted therapeutic approaches and could provide a better understanding of the mechanisms underlying conventional and CpG-based immunotherapy.

IFN-gamma mediates the death of Th1 cells in a paracrine manner

Th1 cells have different capacities to develop into memory cells based on their production of IFN-gamma. In this study, the mechanism by which a homogenous population of IFN-gamma-producing CD4 T cells was eliminated in vivo was assessed. When such cells were transferred into naive mice and activated with Ag, a striking decrease in the frequency of cells in the spleen and lung was observed. However, administration of neutralizing anti-IFN-gamma Ab at the time of Ag challenge largely prevented the elimination of such cells. To determine whether IFN-gamma was mediating its effects directly and/or indirectly, the ability of IFN-gamma to effectively signal in such cells was assessed in vitro. Indeed, there was reduced phosphorylation of STAT1 in response to IFN-gamma as well as markedly reduced expression of the IFN-gammaR beta-chain. Furthermore, transfer of such cells into IFN-gammaR-deficient mice limited their death following activation with Ag. Together, these data suggest that IFN-gamma acts in a paracrine manner to mediate the death of activated IFN-gamma-producing Th1 cells. In contrast to Ag stimulation, administration of CpG alone resulted in the elimination of Th1 cells in IFN-gammaR-/- mice. These results show that in response to Ag stimulation, the death of IFN-gamma-producing effector Th1 cells is controlled in an IFN-gamma-dependent manner, whereas in response to innate activation, the death of IFN-gamma-producing Th1 cells can occur through an IFN-gamma-independent pathway. Collectively, these data show the multiple mechanisms by which Th1 effector cells are efficiently eliminated in vivo.

DNA methylation analysis using CpG microarrays is impaired in benzopyrene exposed cells

Epigenetic alterations have emerged as a key mechanism involved in tumorigenesis. These disruptions are partly due to environmental factors that change normal DNA methylation patterns necessary for transcriptional regulation and chromatin compaction. Microarray technologies are allowing environmentally susceptible epigenetic patterns to be mapped and the precise targets of environmentally induced alterations to be identified. Previously, we observed BaP-induced epigenetic events and cell cycle disruptions in breast cancer cell lines that included time- and concentration-dependent loss of proliferation as well as sequence-specific hypo- and hypermethylation events. In this present report, we further characterized epigenetic changes in BaP-exposed MCF-7 cells. We analyzed DNA methylation on a CpG island microarray platform with over 5400 unique genomic regions. Depleted and enriched microarray targets, representative of putative DNA methylation changes, were identified across the genome; however, subsequent sodium bisulfite analyses revealed no changes in DNA methylation at a number of these loci. Instead, we found that the identification of DNA methylation changes using this restriction enzyme-based microarray approach corresponded with the regions of DNA bound by the BaP derived DNA adducts. This DNA adduct formation occurs at both methylated and unmethylated CpG dinucleotides and affects PCR amplification during sample preparation. Our data suggest that caution should be exercised when interpreting data from comparative microarray experiments that rely on enzymatic reactions. These results are relevant to genome screening approaches involving environmental exposures in which DNA adduct formation at specific nucleotide sites may bias target acquisition and compromise the correct identification of epigenetically responsive genes.

Decreased suppression of immune stimulatory CpG motifs in plant DNA

Due to differential content of CpG motifs in genomic DNA of organisms like bacteria and mammals, CpG-containing DNA delivers a danger or immunostimulatory signal that is recognized by Toll-like receptor 9 in mammalian cells. Here we show that genomic DNA from several plants promote proliferation and CD69 expression as well as activate NFkappaB and JNK pathways in murine B lymphocytes. Plant DNA synergize with specific antigen in activating B cells in a dose-dependent manner. Using a computational method we compared the usage of CpG motif related sequences in DNA of plants, bacteria, mammals or other species. It was found that the CpG motif suppression is much less significant in plant DNA than in mammalian genomes. These computation results partially explain the immunostimulatory activity of plant DNA observed in biological experiments, and lead to the hypothesis that plants respond to plant pathogens by recognizing CpG motifs in the pathogens' genomic DNA. Collectively this work provides new evidence for further understanding the interactions between plants and the human immune system or homeostasis, and between plants and their pathogens. The hypothesis that CpG dependent immunomodulation is a feature of plant DNA that contributes to plant nutrition or food/pollen allergy is also discussed.

Effects of LT-K63 and CpG2006 on phenotype and function of murine neonatal lymphoid cells

The immature state of the immune system of neonates makes them vulnerable to infectious agents, including Streptococcus pneumoniae. The aim of our study was to analyse and compare the effects of Escherichia coli heat-labile enterototoxin (LT)-K63 and CpG2006 on cells and key molecules of the neonatal immune system, using a previously established immunization model with pneumococcal polysaccharide of serotype 1 conjugated to tetanus toxoid (TT) (Pnc1-TT). The cellular response was evaluated by measuring cytokine secretion and proliferation upon in vitro stimulation with TT, the protein moiety of Pnc1-TT, and antibody (Ab) to both the polysaccharide (PS) and protein parts of the vaccine were measured by enzyme-linked immunosorbent assay (ELISA). Antigen (Ag)-presenting and co-stimulatory capacity of neonatal B-cells was evaluated by staining for major histocompatibility complex (MHC)II, CD80, CD86 and CD40. The results showed that both LT-K63 and CpG2006 significantly enhanced the neonatal Ab response to Pnc1-TT. Spleen cells from mice receiving LT-K63 showed enhanced proliferation and interferon (IFN)-gamma, interleukin (IL)-4, IL-5 and IL-10 secretion upon TT stimulation, whereas cells from mice receiving CpG2006 could only enhance IL-10 secretion. LT-K63 and to a lesser extent CpG2006 enhanced the capacity of B-cells to up-regulate the expression of co-stimulatory and activation markers compared with those of mice receiving Pnc1-TT alone. Thus, we conclude that LT-K63 markedly improves T-cell activation whereas the direct adjuvant effect of CpG2006 on neonatal B-cells may partly compensate for lower T-cell help resulting in enhanced neonatal Ab responses to both the TT and PS parts of the vaccine by both adjuvants.

Differential effects of CpG DNA on IFN-beta induction and STAT1 activation in murine macrophages versus dendritic cells: alternatively activated STAT1 negatively regulates TLR signaling in macrophages

Classical STAT1 activation in response to TLR agonists occurs by phosphorylation of the Y701 and S727 residues through autocrine type I IFN signaling and p38 MAPK signaling, respectively. In this study, we report that the TLR9 agonist CpG DNA induced Ifn-beta mRNA, as well as downstream type I IFN-dependent genes, in a MyD88-dependent manner in mouse myeloid dendritic cells. This pathway was required for maximal TNF and IL-6 secretion, as well as expression of cell surface costimulatory molecules. By contrast, neither A- nor B-type CpG-containing oligonucleotides induced Ifn-beta in mouse bone marrow-derived macrophages (BMM) and a CpG-B oligonucleotide did not induce IFn-beta in the macrophage-like cell line, J774. In BMM, STAT1 was alternatively activated (phosphorylated on S727, but not Y701), and was retained in the cytoplasm in response to CpG DNA. CpG DNA responses were altered in BMM from STAT1(S727A) mice; Il-12p40 and Cox-2 mRNAs were more highly induced, whereas Tlr4 and Tlr9 mRNAs were more repressed. The data suggest a novel inhibitory function for cytoplasmic STAT1 in response to TLR agonists that activate p38 MAPK but do not elicit type I IFN production. Indeed, the TLR7 agonist, R837, failed to induce Ifn-beta mRNA and consequently triggered STAT1 phosphorylation on S727, but not Y701, in human monocyte-derived macrophages. The differential activation of Ifn-beta and STAT1 by CpG DNA in mouse macrophages vs dendritic cells provides a likely mechanism for their divergent roles in priming the adaptive immune response.

Synthetic CpG oligodeoxynucleotides augment BAFF- and APRIL-mediated immunoglobulin secretion

The B lymphocyte-activating factor belonging to TNF superfamily (BAFF) acts on B lymphocytes through BAFF receptor (BAFF-R), the transmembrane activator, calcium modulator, and cyclophilin ligand interactor (TACI), and the B cell maturation antigen (BCMA). Another cytokine, a proliferation-inducing ligand (APRIL), only binds to TACI and BCMA. In this study, we sought to determine the effect of Toll-like receptor agonists (TLR-A) on the expression of BAFF/APRIL receptors by murine splenic B lymphocytes. CpG oligodeoxynucleotides (ODN) and LPS strongly up-regulated TACI expression, while BAFF-R was only up-regulated by CpG ODN. CpG ODN pretreatment up-regulated TACI expression on follicular and marginal zone B lymphocytes and increased their responses to BAFF- and APRIL-mediated Ig secretion. TACI seemed to be playing a pivotal role in BAFF- or APRIL-induced Ig secretion because B lymphocytes from TACI-knockout mouse or the blocking of TACI with a neutralizing antibody resulted in total inhibition of IgA and IgG secretion in CpG ODN-pretreated and BAFF- or APRIL-stimulated B cells. Thus, CpG ODN-induced increase in TACI expression is likely to play an important role in Ig secretion following activation of B lymphocytes through TLR9.

Reciprocal effects of Th1 and Treg cell inducing pathogen-associated immunomodulatory molecules on anti-tumor immunity

We have addressed the hypothesis that pathogen-associated immunomodulatory molecules may influence anti-tumor immunity through their pro- and anti-inflammatory activities and abilities to induce effector and regulatory T (Treg) cells. We found that CpG oligonucleotides (CpG) and cholera toxin (CT), which promote Th1 or Th2/Treg cell biased responses, respectively, had differential effects on tumor growth. Therapeutic peritumoral administration of CpG significantly reduced subcutaneous tumor growth and prolonged survival, whereas CT enhanced tumor growth and reduced survival. Peritumoral administration of CpG enhanced the frequency of IFN-gamma-secreting and reduced IL-10-secreting CD4(+) and CD8(+) T cells, in the tumor and in the draining lymph nodes, whereas, CT significantly enhanced the frequency of CD4(+)CD25(+)Foxp3(+) Treg cells, but reduced IFN-gamma-secreting T cells infiltrating the tumor. In contrast to the beneficial effect of CpG in mice with subcutaneous tumors, CpG or CT had no protective effect against tumor growth in the lungs when given therapeutically by the nasal route. However, prophylactic intranasal administration of CpG significantly reduced the number of lung metastases and this was associated with an enhanced frequency of IFN-gamma-secreting CD8(+) T cells in the draining lymph node and enhanced tumor-specific CTL responses. Our findings demonstrate that pathogen-associated molecules can either inhibit or enhance anti-tumor immunity by selectively promoting the induction of effector or regulatory T cells, and that the environment of the growing tumor influences the protective effect.

CpG oligodeoxynucleotides induce cyclooxygenase-2 in human B lymphocytes: implications for adjuvant activity and antibody production

Synthetic CpG oligodeoxynucleotides (ODN), similar to DNA sequences found in certain microorganisms, have shown promise as adjuvants for humans by enhancing immune responses. Since antibodies are often indicators of successful vaccination, it is important to understand how CpG ODNs affect human B cells and influence antibody production. Treatment of human B cells with synthetic CpG ODN sequences increased both steady-state Cox-2 mRNA levels and protein expression. B cell receptor stimulation in concert with CpG ODN treatment induced Cox-2 expression and production of prostaglandin E(2), well above that seen with CpG ODN alone. Importantly, CpG-induced human B cell IgM and IgG production was attenuated by dual Cox-1/Cox-2 inhibitors and Cox-2-selective inhibitors. Our findings support a key role for CpG ODN-induced human B cell Cox-2 in the production of IgM and IgG antibodies, revealing that drugs that attenuate Cox-2 activity have the potential to reduce optimal antibody response to adjuvants/vaccination.

Therapeutic dendritic cell vaccination with Ag coupled to cholera toxin in combination with intratumoural CpG injection leads to complete tumour eradication in mice bearing HPV 16 expressing tumours

We have evaluated whether cholera toxin (CT) can enhance the efficiency of therapeutic dendritic cell (DC) vaccination in mice bearing a human papilloma virus (HPV) 16 antigen (Ag) expressing tumour. Mice were therefore injected with the TC-1 cancer cell line expressing E6 and E7, which are the major oncogenic proteins produced in HPV-induced cervical cancer, and they were then vaccinated with Ag pulsed DCs. While vaccination with E7 pulsed DCs had no impact on tumour growth, DCs pulsed with CT conjugated E7 (CT-E7) significantly reduced tumour size. However, this treatment was only able to eradicate the tumour in 11% of the affected animals. For complete tumour eradication, combinational therapy with CT-E7 pulsed DCs and local treatment of the tumour with CpG oligodeoxynucleotides (CpG) was required. Combinational therapy was associated with increased expression of MHC I and MHC II and increased levels of chemokine production in the tumour. These results suggest that combined treatment with CT-Ag pulsed DCs and local CpG administration offers an efficient strategy to eradicate an already existing HPV-E7 expressing tumour in mice.

Role of interferon-γ during CpG oligodeoxynucleotide-adjuvanted immunization with recombinant proteins

Synthetic oligonucleotides (ODNs) containing immunostimulatory CpG motifs (CpG) are a new class of adjuvants suitable for the development of recombinant vaccines. Here we describe that endogenous interferon (IFN) was critical for the adjuvant activity of CpG ODN as genetically deficient mice developed significantly lower IgG antibody titers following immunization with recombinant proteins. In contrast, the absence of endogenous IL-12/IL-23 or IL-4 had little impact on the magnitude of the antibody response but instead caused a dramatic change in the pattern of IgG isotypes. The dependence on IFN-gamma was specific for CpG ODN and it was not observed with other adjuvants tested. IFN-gamma was produced by NK, dendritic cells, CD4+ and CD8+ T cells stimulated in vitro with CpG ODN. Adoptive transfer experiments confirmed that CD4+ or CD8+ T cells were in fact relevant sources of IFN-gamma in vivo. Following CpG ODN injection, splenic dendritic cells from IFN-gamma deficient mice did not up-regulate CD86 or CD40 expression, suggesting a role for these molecules. The importance of CD28 (CD86 ligand) was confirmed using CD28 deficient mice which presented severely impaired immune responses following CpG ODN-assisted immunization.

Mucosal administration of CpG oligodeoxynucleotide elicits strong CC and CXC chemokine responses in the vagina and serves as a potent Th1-tilting adjuvant for recombinant gD2 protein vaccination against genital herpes

Although sexually transmitted pathogens are capable of inducing pathogen-specific immune responses, vaginal administration of nonreplicating antigens elicits only weak, nondisseminating immune responses. The present study was undertaken to examine the potential of CpG-containing oligodeoxynucleotide (CpG ODN) for induction of chemokine responses in the genital tract mucosa and also as a vaginal adjuvant in combination with glycoprotein D of herpes simplex virus type 2 (HSV-2) for induction of antigen-specific immune responses. We found that a single intravaginal administration of CpG ODN in mice stimulates a rapid and potent response of CC chemokines macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and RANTES as well as of CXC chemokines MIP-2 and IP-10 in the vagina and/or the genital lymph nodes. Importantly, intravaginal vaccination with recombinant gD2 in combination with CpG ODN gave rise to a strong antigen-specific Th1-like immune response in the genital lymph nodes as well as the spleens of the vaccinated mice. Further, such an immunization scheme conferred both systemic and mucosal immunoglobulin G antibody responses as well as protection against an otherwise lethal vaginal challenge with HSV-2. These results illustrate the potential of CpG ODN for induction of potent chemokine responses in the genital tract and also as a vaginal adjuvant for generation of Th1-type mucosal and systemic immune responses towards a nonreplicating antigen derived from a sexually transmitted pathogen. These data have implications for the development of a mucosal vaccine against genital herpes and possibly other sexually transmitted diseases.

Cross-talk between toll-like receptors 5 and 9 on activation of human immune responses

The recognition of pathogen-associated molecular patterns by TLRs triggers the activation of innate and adaptive immune responses. Flagellin, the agonist of TLR5, is expressed by prokaryotes and eukaryotes, and DNA sequences containing unmethylated CpG dinucleotides, agonists of TLR9, are present essentially in prokaryotes. To test the potential modulating effects of simultaneous activation of different TLRs on the immune response, we compared the outcomes in different immune cell compartments induced by triggering TLR5 and TLR9 individually and in combination. PBMCs, monocytes, and monocyte-derived DC (MoDC) secreted high levels of IL-10 in response to flagellin, whereas oligodeoxynucleotides (ODN) containing the CpG sequence (CpG-ODN), synthetic ligands of TLR9, did not induce IL-10 secretion in any of the three cell types but synergized with flagellin in this induction. In contrast, PBMC production of IFN-alpha induced by CpG-ODN was strongly inhibited by flagellin. Conversely, CpG-ODN did not enhance the up-regulation of activation markers in MoDC induced to mature in the presence of flagellin. Flagellin-matured, but not CpG-ODN-matured, MoDC stimulated the expansion of allogeneic CD4+CD25+ T cells, and the extent of expansion induced by MoDC, matured in the presence of flagellin and CpG-ODN, was similar to that induced by flagellin-matured MoDC. Moreover, flagellin and CpG-ODN differentially affected NK-mediated cytotoxicity, and flagellin completely abrogated the NK-mediated immune response induced by CpG-ODN stimulation. Together, these results suggest that flagellin inhibits the TLR9-induced cell activation and cytokine production, which favor Th1-type immune responses, possibly because the signals evoked by flagellin to indicate the presence of extracellular pathogens must favor a Th2-polarized response. Thus, TLR5 and TLR9, alerted by the presence of microorganisms, influence each other to mount the more efficient and appropriate immune response to contain the infection of a specific pathogen.

Ligand-induced conformational changes allosterically activate Toll-like receptor 9

Microbial and synthetic DNA rich in CpG dinucleotides stimulates Toll-like receptor 9 (TLR9), whereas DNA lacking CpG either is inert or can inhibit TLR9 activation. The molecular mechanisms by which TLR9 becomes activated or is inhibited are not well understood. Here we show that TLR9 bound to stimulatory and inhibitory DNA; however, only stimulatory DNA led to substantial conformational changes in the TLR9 ectodomain. In the steady state, 'inactive' TLR9 homodimers formed in an inactivated conformation. Binding of DNA containing CpG, but not of DNA lacking CpG, to TLR9 dimers resulted in allosteric changes in the TLR9 cytoplasmic signaling domains. In endosomes, conformational changes induced by DNA containing CpG resulted in close apposition of the cytoplasmic signaling domains, a change that is probably required for the recruitment of signaling adaptor molecules. Our results indicate that the formation of TLR9 dimers is not sufficient for its activation but instead that TLR9 activation is regulated by conformational changes induced by DNA containing CpG.

The role of CpG ODN in enhancement of immune response and protection in BALB/c mice immunized with recombinant major surface glycoprotein of Leishmania (rgp63) encapsulated in cationic liposome

CpG oligodeoxynucleotides (CpG ODN) are known to be a potent immunoadjuvant for a wide range of antigens. The aim of this study was to evaluate the role of CpG ODN co-encapsulated with rgp63 antigen in cationic liposomes (Lip-rgp63-CpG ODN) in immune response enhancement and protection in BALB/c mice against leishmaniasis. Lip-rgp63-CpG ODN prepared by using dehydration-rehydration vesicle (DRV) method significantly inhibited (P<0.001) Leishmania major infection in mice measured by footpad swelling compared to Lip-rgp63, rgp63 alone, rgp63 plus CpG ODN, PBS or control liposomes. The mice immunized with Lip-rgp63-CpG ODN also showed the lowest spleen parasite burden, highest IgG2a/IgG1 ratio and IFN-gamma production and the lowest IL-4 production compared to the other groups. The results indicate that co-encapsulation of CpG ODN in liposomes improves the immunogenicity of Leishmania antigen.

Expression and function of the IL-2 receptor in activated human plasmacytoid dendritic cells

Human and mouse plasmacytoid dendritic cells (PDC) express IL-2 mRNA specifically upon TLR stimulation, but not under CD40L stimulation. Even though the expression of the IL-2R by PDC has been described, the functional implications of this expression remain unknown. Here, we investigated the expression and function of the IL-2R in activated human PDC. The IL-2Ralpha chain, CD25, is expressed in both CpG- and CD40L-activated PDC. CD25 expression is a relatively rapid event, as the receptor was detected 6 h after the initial activation signal. Exogenous IL-2 added to CD40L-activated PDC increased the expression of CD25, enhanced the secretion of pro-inflammatory cytokines and promotes PDC survival. CpG-activated PDC cultured in the presence of IL-2R-blocking monoclonal antibodies showed a reduced expression of pro-inflammatory cytokines, especially TNF-alpha. This reduction was dose and time dependent, suggesting a regulatory role of IL-2 in TNF secretion that might occur at the post-transcriptional level. These results indicate that the expression of the IL-2R is relevant to human PDC activation, and that IL-2 may be an important auto- and/or paracrine factor modulating the activation and survival of PDC. Finally, CD25 expression may be considered as a useful early activation marker for human PDC.

Induction of a Th1 response from Th2-polarized T cells by activated dendritic cells: dependence on TCR:peptide-MHC interaction, ICAM-1, IL-12, and IFN-gamma

Dendritic cells (DC) are important regulators of T cell immunity. The degree of stimulation, the pattern of costimulatory molecules expressed, and the cytokines secreted by DC dictate the nature of the effector and memory cells generated, particularly with respect to their Th1 or Th2 phenotypes. In this study, we demonstrate that the addition of activated DC to spleen cultures containing established Th2-polarized CD4(+) T cells was sufficient to suppress Th2 and induce Th1 cytokines in a recall response, a phenomenon referred to as phenotype reversal. The ability of activated DC to induce phenotype reversal displayed exquisite Ag specificity. The DC activator B7-DC cross-linking Ab (XAb) was >10,000-fold more efficient at inducing phenotype reversal than the TLR agonists CpG-oligodeoxynucleotide and Gardiquimod. Characterization of the mechanisms governing phenotype reversal revealed the requirement for cognate interaction between the TCR:peptide-MHC complex, the expression of the costimulation/adhesion molecule ICAM-1, and secretion of IL-12 and IFN-gamma by the activated DC. The requirement for the costimulation/adhesion molecule SLAM (signaling lymphocytic activation molecule) was found to be quantitative. Thus, activation of DC, particularly by crosslinking B7-DC, can modulate well-established Th2 T cell responses in an Ag-specific manner. Because the regulation of mouse and human DC by B7-DC XAb overlaps in several significant ways, immune modulation with B7-DC XAb is a potential strategy for treating Th2-mediated diseases.

TLR ligands act directly upon T cells to restore proliferation in the absence of protein kinase C-theta signaling and promote autoimmune myocarditis

The serine/threonine kinase, protein kinase C-theta (PKC-theta), plays a central role in the activation and differentiation of Th2 cells while being redundant in CD4+ and CD8+ antiviral responses. Recent evidence indicates that PKC-theta may however be required for some T cell-driven autoimmune responses. We have investigated the role of PKC-theta in the induction of autoimmune myocarditis induced by either Coxsackie B3 virus infection or immunization with alpha-myosin/CFA (experimental autoimmune myocarditis (EAM)). PKC-theta-deficient mice did not develop EAM as shown by impaired inflammatory cell infiltration into the heart, reduced CD4+ T cell IL-17 production, and the absence of a myosin-specific Ab response. Comparatively, PKC-theta was not essential for both early and late-phase Coxsackie virus-induced myocarditis. We sought to find alternate pathways of immune stimulation that might reconcile the differential requirements for PKC-theta in these two disease models. We found systemic administration of the TLR ligand CpG restored EAM in PKC-theta-deficient mice. CpG could act directly upon TLR9-expressing T cells to restore proliferation and up-regulation of Bcl-x(L), but exogenous IL-6 and TGF-beta was required for Th17 cell differentiation. Taken together, these results indicate that TLR-mediated activation of T cells can directly overcome the requirement for PKC-theta signaling and, combined with the dendritic cell-derived cytokine milieu, can promote the development of autoimmunity.

Murine neonatal CD4+ cells are poised for rapid Th2 effector-like function

Murine neonates typically mount Th2-biased immune responses. This entails a cell-intrinsic component whose molecular basis is unknown. We found that neonatal CD4(+) T cells are uniquely poised for rapid Th2 function. Within 24 h of activation, neonatal CD4(+) cells made high levels of IL-4 and IL-13 mRNA and protein. The rapid high-level IL-4 production arose from a small subpopulation of cells, did not require cell cycle entry, and was unaffected by pharmacologic DNA demethylation. CpG methylation analyses in resting neonatal cells revealed pre-existing hypomethylation at a key Th2 cytokine regulatory region, termed conserved noncoding sequence 1 (CNS-1). Robust Th2 function and increased CNS-1 demethylation was a stable property that persisted in neonatal Th2 effectors. The transcription factor STAT6 was not required for CNS-1 demethylation and this state was already established in neonatal CD4 single-positive thymocytes. CNS-1 demethylation levels were much greater in IL-4-expressing CD4 single-positive thymocytes compared with unactivated cells. Together, these results indicate that neonatal CD4+ T cells possess distinct qualities that could predispose them toward rapid, effector-like Th2 function.

Novel transcriptional regulation of the schlafen-2 gene in macrophages in response to TLR-triggered stimulation

Schlafen-2 (slfn-2) is a member of slfn family, regulators of T cell development and its expression is altered during infection by microbial pathogens. However, the molecular mechanism involved in slfn expression is still to be determined. In this study, we isolated slfn-2 as a LPS-induced differentially expressed genes (DEGs) in RAW 264.7 cells and examined expression and regulation of slfn-2 in CpG-DNA-treated and LPS-treated macrophages. We defined a transcriptional start site in the slfn-2 gene. To examine the promoter organization of the slfn-2 gene, we cloned a approximately 1.8 kb region upstream of the transcription start site. Sequence analysis indicates consensus sites for AP-1 and NF-kappaB. Comprehensive mutant analyses, ELISA-based transcription factor activation assay, and ChIP assays reveal that functional interaction of AP-1 and NF-kappaB with the promoter element is necessary for the Toll-like receptor (TLR)-mediated slfn-2 gene expression by CpG-DNA and LPS treatment in macrophages. In summary, we identified a slfn-2 promoter for the first time and demonstrated that CpG-DNA and LPS triggers slfn-2 gene expression by activating NF-kappaB and AP-1 pathways in macrophages.

Intranasal CpG DNA therapy during allergen exposure in allergic rhinitis

OBJECTIVE

1) To estimate the effectiveness of intranasal administration of CpG DNA alone on allergic rhinitis compared with intradermal administration; and 2) to find out how CpG DNA therapy is useful in treatment of allergic rhinitis.

STUDY DESIGN

Mice were intraperitoneally sensitized and intranasally challenged with Japanese cedar. Therapy with CpG DNA alone was also performed during challenge, either intranasally or intradermally. Immunologic variables and nasal symptom were studied.

RESULTS

Intranasal administration of CpG DNA alone significantly reduced the levels of IgE, IL-5 productions from nasal lymphocytes and splenocytes, nasal eosinophilia, and nasal symptoms, although intradermal administration of CpG DNA alone showed no significant reduction.

CONCLUSION

This study demonstrated that CpG DNA has effects not only on splenocytes but also on nasal lymphocytes to attenuate allergic rhinitis, and that intranasal administration, but not intradermal administration, of CpG DNA alone during allergen exposure is useful for control of allergic rhinitis.

CpG oligodeoxynucleotide treatment enhances innate resistance and acquired immunity to African trypanosomes

Relative resistance to African trypanosomiasis is based on the development of a type I cytokine response, which is partially dependent on innate immune responses generated through MyD88 and Toll-like receptor 9 (TLR9). Therefore, we asked whether enhancement of the immune response by artificial stimulation with CpG oligodeoxynucleotide (ODN), a TLR9 agonist, would result in enhanced protection against trypanosomes. In susceptible BALB/c mice, relative resistance to infection was significantly enhanced by CpG ODN treatment and was associated with decreased parasite burden, increased cytokine production, and elevated parasite-specific B- and T-cell responses. In relatively resistant C57BL/6 mice, survival was not enhanced but early parasitemia levels were reduced 100-fold and the majority of the parasites were nondividing, short stumpy (SS) forms. CpG ODN treatment of lymphocyte-deficient C57BL/6-scid and BALB/cByJ-scid mice also enhanced survival and reduced parasitemia, indicating that innate resistance to trypanosome infection can be enhanced. In C57BL/6-scid and BALB/cByJ-scid mice, the parasites were also predominantly SS forms during the outgrowth of parasitemia. However, the effect of CpG ODN treatment on parasite morphology was not as marked in gamma interferon (IFN-gamma)-knockout mice, suggesting that downstream effects of IFN-gamma production may play a discrete role in parasite cell differentiation. Overall, these studies provide the first evidence that enhancement of resistance to African trypanosomes can be induced in susceptible animals in a TLR9-dependent manner and that CpG ODN treatment may influence the developmental life cycle of the parasites.

Intranasal immunization with chlamydial protease-like activity factor and CpG deoxynucleotides enhances protective immunity against genital Chlamydia muridarum infection

We have reported recently that intranasal (i.n.) vaccination with chlamydial protease-like activity factor (CPAF) and interleukin-12 (IL-12) enhances protective immunity against genital chlamydial challenge. In this study, we show that i.n. or intraperitoneal (i.p.) vaccination with CPAF plus CpG deoxynucleotides (CpG), an alternative T helper 1 (Th1) adjuvant, induced robust CPAF-specific IFN-gamma responses and elevated levels of serum antibody and vaginal IgA production. CPAF+CpG vaccinated animals displayed accelerated genital chlamydial clearance, and minimal hydrosalpinx and inflammatory cellular infiltration compared to mock-immunized (PBS) challenged animals. Together, CpG dexoynucleotides are an efficacious alternative Th1 adjuvant with CPAF to induce protective anti-chlamydial immunity.

Long-lasting protective immune response to the 19-kilodalton carboxy-terminal fragment of Plasmodium yoelii merozoite surface protein 1 in mice

Merozoite surface protein 1 (MSP1) is the major protein on the surface of the plasmodial merozoite, and its carboxy terminus, the 19-kDa fragment (MSP1(19)), is highly conserved and effective in induction of a protective immune response against malaria parasite infection in mice and monkeys. However, the duration of the immune response has not been elucidated. As such, we immunized BALB/c mice with a standard four-dose injection of recombinant Plasmodium yoelii MSP1(19) formulated with Montanide ISA51 and CpG oligodeoxynucleotide (ODN) and monitored the MSP1(19)-specific antibody levels for up to 12 months. The antibody titers persisted constantly over the period of time without significant waning, in contrast to the antibody levels induced by immunization with Freund's adjuvant, where the antibody levels gradually declined to significantly lower levels 12 months after immunization. Investigation of immunoglobulin G (IgG) subclass longevity revealed that only the IgG1 antibody level (Th2 type-driven response) decreased significantly by 6 months, while the IgG2a antibody level (Th1 type-driven response) did not change over the 12 months after immunization, but the boosting effect was seen in the IgG1 antibody responses but not in the IgG2a antibody responses. After challenge infection, all immunized mice survived with negligibly patent parasitemia. These findings suggest that protective immune responses to MSP1(19) following immunization using oil-based Montanide ISA51 and CpG ODN as an adjuvant are very long-lasting and encourage clinical trials for malaria vaccine development.