CpG oligonucleotides can prophylactically immunize against Th2-mediated schistosome egg-induced pathology by an IL-12-independent mechanism

Type 2 cytokines: mechanisms and therapeutic strategies

Type 2 immune responses are defined by the cytokines interleukin-4 (IL-4), IL-5, IL-9 and IL-13, which can either be host protective or have pathogenic activity. Type 2 immunity promotes antihelminth immunity, suppresses type 1-driven autoimmune disease, neutralizes toxins, maintains metabolic homeostasis, and regulates wound repair and tissue regeneration pathways following infection or injury. Nevertheless, when type 2 responses are dysregulated, they can become important drivers of disease. Type 2 immunity induces a complex inflammatory response characterized by eosinophils, mast cells, basophils, type 2 innate lymphoid cells, IL-4-and/or IL-13-conditioned macrophages and T helper 2 (TH2) cells, which are crucial to the pathogenesis of many allergic and fibrotic disorders. As chronic type 2 immune responses promote disease, the mechanisms that regulate their maintenance are thought to function as crucial disease modifiers. This Review discusses the many endogenous negative regulatory mechanisms that antagonize type 2 immunity and highlights how therapies that target some of these pathways are being developed to treat type 2-mediated disease.

Type 2 cytokines: mechanisms and therapeutic strategies

Type 2 immune responses are defined by the cytokines interleukin-4 (IL-4), IL-5, IL-9 and IL-13, which can either be host protective or have pathogenic activity. Type 2 immunity promotes antihelminth immunity, suppresses type 1-driven autoimmune disease, neutralizes toxins, maintains metabolic homeostasis, and regulates wound repair and tissue regeneration pathways following infection or injury. Nevertheless, when type 2 responses are dysregulated, they can become important drivers of disease. Type 2 immunity induces a complex inflammatory response characterized by eosinophils, mast cells, basophils, type 2 innate lymphoid cells, IL-4-and/or IL-13-conditioned macrophages and T helper 2 (TH2) cells, which are crucial to the pathogenesis of many allergic and fibrotic disorders. As chronic type 2 immune responses promote disease, the mechanisms that regulate their maintenance are thought to function as crucial disease modifiers. This Review discusses the many endogenous negative regulatory mechanisms that antagonize type 2 immunity and highlights how therapies that target some of these pathways are being developed to treat type 2-mediated disease.

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.

Coordination between TLR9 signaling in macrophages and CD3 signaling in T cells induces robust expression of IL-30

IL-30, the p28 subunit of IL-27, interacts with EBV-induced gene 3 to form IL-27, which modulates both proinflammatory and anti-inflammatory responses during autoimmune or infectious disease. It also acts as a natural antagonist of gp130, thereby attenuating the signals of other gp130-associated cytokines. IL-30 regulation via LPS has been reported by others, but the intercellular communication that induces IL-30 expression is unknown. In this study, we show that treatment with anti-CD3/CD28 Abs plus CpG oligodeoxynucleotides induces robust expression of IL-30, whereas either treatment alone induces only low expression of IL-30. This observation in vitro mirrors the murine model in which administration of CpG under inflammatory conditions in vivo induces IL-30 expression. This robust induction of IL-30 occurs through the coordination of helper CD4(+) T cells and innate immune cells (e.g., macrophages) and, to a lesser degree, B cells via the CD40/CD154 signaling pathway. These findings reveal a previously unrecognized mechanism that integrates signaling pathways from T cells and macrophages at the cellular level to induce IL-30 expression.

Combined Tbet and IL12 gene therapy elicits and recruits superior antitumor immunity in vivo

We have recently shown that intratumor (i.t.) injection of syngenic dendritic cells (DC) engineered to express the transcription factor Tbet (TBX21) promotes protective type-1 T cell-mediated immunity via a mechanism that is largely interleukin (IL)-12p70-independent. Since IL-12 is a classical promoter of type-1 immunity, the current study was undertaken to determine whether gene therapy using combined Tbet and IL-12 complementary DNA (cDNA) would yield improved antitumor efficacy based on the complementary/synergistic action of these biologic modifiers. Mice bearing established subcutaneous (s.c.) tumors injected with DC concomitantly expressing ectopic Tbet and IL12 (i.e., DC.Tbet/IL12) displayed superior (i) rates of tumor rejection and extended overall survival, (ii) cross-priming of Tc1 reactive against antigens expressed within the tumor microenvironment, and (iii) infiltration of CD8(+) T cells into treated tumors in association with elevated locoregional production of CXCR3 ligand chemokines. In established bilateral tumor models, i.t. delivery of DC.Tbet/IL12 into a single lesion led to slowed growth or regression at both tumor sites. Furthermore, DC.Tbet/IL12 pulsed with tumor antigen-derived peptides and injected as a therapy distal to the tumor site prevented tumor growth and activated robust antigen-specific Tc1 responses. These data support the translation use of combined Tbet and IL-12p70 gene therapy in the cancer setting.

Impaired lung dendritic cell migration and T cell stimulation induced by immunostimulatory oligonucleotides contribute to reduced allergic airway inflammation

CpG-containing oligonucleotides (CpG) have been shown to reduce key features of allergic airway inflammation in mouse models. Given the inhibitory effects of CpG treatment on Ag presentation of subsequently encountered Ags via MHC class I and II molecules by dendritic cells (DC), we hypothesized that intranasal CpG treatment would lead to reduced Ag-specific T cell stimulation in the lung-draining lymph nodes, thereby reducing the inflammatory response in sensitized mice. Intranasal CpG administration led to phenotypic maturation of lung and mediastinal lymph node DC as determined by expression of MHC class II, CD80, and CD86. This was accompanied by a significant reduction in the proliferation of adoptively transferred Ag-specific CD4(+) and CD8(+) T cells in mediastinal lymph nodes, when CpG was given before inhalative OVA challenges. DC obtained from mediastinal lymph nodes of CpG-treated mice before OVA inhalation led to reduced T cell stimulation via MHC class I and II molecules. In addition, CpG diminished airway eosinophilia and pulmonary infiltration after sensitization or following adoptive transfer of Ag-specific Th2 cells. These results were explained by reduced CCL21 expression and inhibition of lung DC migration following CpG administration, which could be restored by transfer of bone marrow-derived DC, because CpG had no major impact on the constitutive MHC class II Ag presentation of protein-derived Ag by lung tissue-derived DC. We conclude that CpG treatment can effectively impair the DC-mediated Ag transport from the lungs to the lymph nodes, resulting in reduced T cell activation and blunted airway inflammation.

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.

The protective efficacy against Schistosoma japonicum infection by immunization with DNA vaccine and levamisole as adjuvant in mice

Levamisole (LMS) as an adjuvant enhances cell-mediated immunity in DNA vaccination; we investigated the efficacy and liver immunopathology alleviation of a DNA vaccine, VR1012-SjGST-32, in a LMS formulation in the murine challenge model. Compared to controls, the VR1012-SjGST-32 plus LMS can reduce worm and egg burdens, as well as, immunopathological complications associated chronic inflammation significantly in liver, which were apparently associated with Th1-type response. Together, these results suggest that the LMS as a potential Schistosome DNA vaccine adjuvant can enhance both worm killing and disease prevention, which is possibly mediated through the induction of a strong Th1-dominant environment in immunized mice.

The immunodominant T helper 2 (Th2) response elicited in BALB/c mice by the Leishmania LiP2a and LiP2b acidic ribosomal proteins cannot be reverted by strong Th1 inducers

The search for disease-associated T helper 2 (Th2) Leishmania antigens and the induction of a Th1 immune response to them using defined vaccination protocols is a potential strategy to induce protection against Leishmania infection. Leishmania infantum LiP2a and LiP2b acidic ribosomal protein (P proteins) have been described as prominent antigens during human and canine visceral leishmaniasis. In this study we demonstrate that BALB/c mice infected with Leishmania major develop a Th2-like humoral response against Leishmania LiP2a and LiP2b proteins and that the same response is induced in BALB/c mice when the parasite P proteins are immunized as recombinant molecules without adjuvant. The genetic immunization of BALB/c mice with eukaryotic expression plasmids coding for these proteins was unable to redirect the Th2-like response induced by these antigens, and only the co-administration of the recombinant P proteins with CpG oligodeoxynucleotides (CpG ODN) promoted a mixed Th1/Th2 immune response. According to the preponderance of a Th2 or mixed Th1/Th2 responses elicited by the different regimens of immunization tested, no evidence of protection was observed in mice after challenge with L. major. Although alterations of the clinical outcome were not detected in mice presensitized with the P proteins, the enhanced IgG1 and interleukin (IL)-4 response against total Leishmania antigens in these mice may indicate an exacerbation of the disease.

Common human Toll-like receptor 9 polymorphisms and haplotypes: association with atopy and functional relevance

BACKGROUND

Toll-like receptor 9 (TLR9) is a pattern-recognition receptor that detects unmethylated CpG motifs prevalent in bacterial and viral DNA. TLR9 stimulation is a key event after bacterial infection, triggering innate immunity and T-helper type 1 skewed adaptive immunity. Synthetic CpG-oligodeoxynucleotides (CpG-ODNs) represent a promising and novel class of immune adjuvants for allergy treatment, vaccination, and cancer therapy. However, common functional TLR9 gene variants could interfere with the clinical utilization of CpG-ODN in immunotherapy. Recently, a possible association of TLR9 polymorphism C-1237T with asthma has been reported.

OBJECTIVE

The aim of the present study was to investigate whether TLR9 polymorphisms or haplotypes have functional relevance and are associated with atopy.

METHODS

We genotyped five common TLR9 single-nucleotide polymorphisms (SNPs) in promoter, exon, and intron regions of the gene in 527 healthy blood donors, and estimated four common haplotypes. The total IgE and specific IgE levels against the most common aeroallergens were measured (n=303). IFN-alpha production by plasmacytoid dendritic cells (pDCs) was analysed after stimulation with TLR9 ligand CpG-ODN (n=220).

RESULTS

No significant influence of common TLR9 polymorphisms and haplotypes on the total and specific IgE levels was found. Functional analysis of CpG-ODN-induced IFN-alpha did not indicate a significant role for common TLR9 gene polymorphisms in TLR9 function.

CONCLUSION

We conclude that common genetic differences in the TLR9 gene exert no major influence on allergy susceptibility, and are unlikely to have on impact on clinical application of CpG-ODNs.

Development of a novel Ag-specific immunotherapy using CpG oligodeoxynucleotides in a new, unique mouse cutaneous eosinophilic inflammation model

The number of patients with severe atopic dermatitis (AD) has been on the rise recently. We are therefore urgently in need of a treatment that can suppress Th2 cell-mediated responses in an Ag-specific fashion. Oligodeoxynucleotides (ODN)containing CpG motifs (CpG ODN) have been highlighted as immunomodulators that reduce Th2-mediated responses. To determine the effect of CpG ODN on Th2-mediated skin inflammation, we first developed a reproducible murine model of protein Ag-induced eosinophilic inflammation that is accompanied by epidermal acanthosis and increased serum IgE levels as seen in AD. In this model we found that treatment with CpG ODN during epicutaneous sensitization in previously i.p.-primed mice prevented the development of Th2-mediated responses. Furthermore, to evaluate the therapeutic effect of CpG ODN on established eosinophilic inflammation, mice were treated with a course of the immunotherapy at a skin site remote from the area of Ag application prior to the second 1-wk epicutaneous exposure to Ag. Therapeutic treatment with CpG ODN plus Ag, but not that with CpG ODN alone, could reverse the established eosinophilic inflammation. The presented results provide strong evidence for the feasibility of a novel Ag-specific immunomodulator to treat cutaneous eosinophilic inflammation such as that characteristically found in patients with severe AD.

Immunostimulatory oligonucleotides block allergic airway inflammation by inhibiting Th2 cell activation and IgE-mediated cytokine induction

A single treatment with a CpG-containing immunostimulatory DNA sequence (ISS) given before allergen challenge can inhibit T helper type 2 cell (Th2)–mediated airway responses in animal models of allergic asthma; however, the mechanism of this inhibition remains largely undefined. Here, we demonstrate that airway delivery of ISS before allergen challenge in Th2-primed mice acts in two distinct ways to prevent the allergic responses to this challenge. The first is to prevent induction of cytokines from allergen-specific Th2 cells, as demonstrated by the nearly complete inhibition of Th2 cytokine production, Th2-dependent functional responses, and gene induction patterns. ISS inhibits the Th2 response by rendering lung antigen-presenting cells (APCs) unable to effectively present antigen to Th2 cells, but not to Th1 cells. This loss of APC function correlates with a reduced expression of costimulatory molecules, including programmed cell death ligand (PD-L)1, PD-L2, CD40, CD80, CD86, and inducible T cell costimulator, and of major histocompatibility complex class II on CD11c⁺APCs from the airways of ISS-treated mice. The second important action of ISS is inhibition of immunoglobulin E–dependent release of Th2 cytokines, especially interleukin 4, from basophils and/or mast cells in the airways of Th2-primed mice. Thus, inhibition by ISS of allergic responses can be explained by two novel mechanisms that culminate in the inhibition of the principal sources of type 2 cytokines in the airways.

Tissue migration by parasitic helminths – an immunoevasive strategy?

Migration through host tissues has major costs for parasitic helminths in terms of energy expenditure, risks of attrition and the need to adapt to varying physicochemical environments. Nevertheless, such migratory phases seem to confer a specific survival advantage. One reason for this might be the avoidance of specific host immune-defence mechanisms designed to protect against threats at mucosal surfaces.

Local therapy with CpG motifs in a murine model of allergic airway inflammation in IFN-beta knock-out mice

Background

CpG oligodeoxynucleotides (CpG-ODN) are capable of inducing high amounts of type I IFNs with many immunomodulatory properties. Furthermore, type-I IFNs have been proposed to play a key role in mediating effects of CpG-ODN. The precise role of IFN-β in the immunomodulatory effects of CpG-ODN is not known.

Objective

Here, we aimed to elucidate the role of IFN-β in the anti-allergic effect of CpG motifs.

Methods

We assessed the immune response in OVA-primed/OVA-challenged IFN-β knockout (-/-) mice compared to wild type (WT) control, after intranasal and systemic treatment with synthetic CpG motifs.

Results

Vaccination with CpG-ODN reduced the number of cells in airways of OVA-sensitized WT but not IFN-β-/- mice. Although airway eosinophilia was reduced in both treated groups, they were significantly higher in IFN-β^-/- mice. Other inflammatory cells, such as lymphocytes and macrophages were enhanced in airways by CpG treatment in IFN-β-/- mice. The ratio of IFN-γ/IL-4 cytokines in airways was significantly skewed to a Th1 response in WT compared to IFN-β^-/- group. In contrast, IL-4 and IgE were reduced with no differences between groups. Ag-specific T-cell proliferation, Th1-cytokines such as IFN-γ, IL-2 and also IL-12 were significantly lower in IFN-β-/- mice. Surprisingly, we discovered that intranasal treatment of mice with CpG-ODN results in mild synovitis particularly in IFN-β-/- mice.

Conclusion

Our results indicate that induction of Th1 response by therapy with CpG-ODN is only slightly and partially dependent on IFN-β, while IFN-β is not an absolute requirement for suppression of airway eosinophilia and IgE. Furthermore, our finding of mild synovitis is a warning for possible negative effects of CpG-ODN vaccination.

Stimulation via Toll-like receptor 9 reduces Cryptococcus neoformans-induced pulmonary inflammation in an IL-12-dependent manner

Cytosine-phosphate-guanosine-containing oligodeoxynucleotides (CpG ODN) are important vaccine adjuvants that promote Th1-type immune responses. Cryptococcus neoformans is a serious human pathogen that replicates in the lung but may disseminate systemically leading to meningitis, particularly in immunocompromised individuals. Immunization of susceptible C57BL/6 mice with CpG ODN deviates the immune response from a Th2- toward a Th1-type response following infection with C. neoformans. CpG also induces IL-12, TNF, MCP-1 and macrophage nitric oxide production. CD4(+) and CD8(+) T cells producing IFN-gamma increase in frequency, while those producing IL-5 decrease. More importantly, pulmonary eosinophilia is significantly reduced, an effect that depends on IL-12 and CD8(+) T cells but not NK cells. CpG treatment also reduces the burden of C. neoformans in the lung, an effect that is IL-12-, NK cell- and T cell-independent and probably reflects a direct effect of CpG on pathogen opsonization or an enhancement of macrophage antimicrobial activity. An equivalent beneficial effect is also observed when CpG ODN treatment is delivered during established cryptococcal disease. This is the first study documenting that promotion of lung TLR9 signaling using synthetic agonists enhances host defense. Activation of innate immunity has clear therapeutic potential and may even be beneficial in patients with acquired immune deficiency.

Modulation of ovalbumin-induced Th2 responses by second-generation immunomodulatory oligonucleotides in mice

Oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG DNAs) prevent development of T-helper type 2 (Th2) immune responses and reverse established allergic responses in mouse models. We recently reported that second-generation immunomodulatory oligonucleotides (IMOs) containing novel structures (immunomers) and a synthetic immunostimulatory CpR (R=2'-deoxy-7-deazguanosine) motif induce the production of distinct cytokine secretion profiles in vitro and in vivo. In the present study, we evaluated IMOs containing CpG and CpR motifs to modulate allergen-induced Th2 immune responses in prevention and treatment models. Mice sensitized and challenged with ovalbumin (OVA) were treated with a CpG DNA or an IMO by administration either at the time of OVA sensitization (co-administration; prevention) or after establishment of an allergic response (treatment). Spleens, blood, and lungs were collected and analyzed for immune responses. Spleen-cell cultures harvested from OVA-sensitized mice showed a significant decrease in Th2 cytokine levels with a concomitant increase in Th1 cytokine levels only when CpG DNA or IMOs were co-administered with OVA. The co-administration of CpG DNA or IMOs during OVA sensitization significantly reduced serum OVA-specific and total IgE levels in mice. The mice who received CpG DNA or IMOs co-administered with OVA showed a small reduction in serum OVA-specific and total IgG1 levels and a significant increase in serum OVA-specific and total IgG2a levels. Similar results were found in mice with established allergic responses who received IMO treatment. IMO treatment also resulted in strong inhibition of inflammatory cell infiltration and goblet cell hyperplasia in the lungs compared with untreated mice lungs. These data demonstrate that IMOs prevent antigen-induced Th2 immune responses when co-administered to mice during OVA sensitization and that IMOs reverse established allergic responses induced by OVA.

The anti-allergic effects of lactic acid bacteria are strain dependent and mediated by effects on both Th1/Th2 cytokine expression and balance

BACKGROUND

There is growing interest in the immune-stimulating effect and in particular, the anti-allergic effect, of lactic acid bacteria (LAB). However, no comprehensive studies have been done that compare the immune-stimulating potential of LAB strains.

METHODS

The in vitro immune-stimulating effects on Th1/Th2 balance of more than 100 LAB strains were compared in splenocytes from ovalbumin-sensitized Th2-polarized mice. The in vivo anti-allergic ability of strain KW3110 was studied in the Th2-polarized model by detecting serum IgE concentration, Th1/Th2 cytokine secretion from splenocytes, and the expression of co-stimulatory molecules on macrophages.

RESULTS

In vitro studies from Th2-polarized splenocytes, using IL-12 as a Th1 parameter and IL-4 secretion as a Th2 parameter revealed a wide variety of IL-12-inducing and IL-4-repressing activities, depending on the strain of LAB, not depending on the species. However, evaluation of individual strains in vivo revealed that after exposure to Lactobacillus paracasei KW3110 strain, the serum IgE elevation elicited by repeated OVA injection of mice was strongly inhibited. Cytokine secretion from splenocytes 20 weeks after KW3110 administration showed increased IL-12 and decreased IL-4 expression. Both CD40 and B7-1 expression on macrophages was upregulated by administration of KW3110.

CONCLUSIONS

Improving the consequences of the Th1/Th2 imbalance by administration of LAB was dependent upon the LAB strain rather than the LAB species. Oral KW3110 administration in the mouse allergy model directed the Th1/Th2 balance toward Th1 through the maturation of APCs and inhibition of serum IgE elevation.

Immunopathogenesis of schistosomiasis

In schistosomiasis mansoni, the chronic egg-induced granulomatous response in the liver and intestines may eventually cause extensive tissue scarring and development of portal hypertension. Indeed, much of the morbidity and mortality associated with this disease is directly attributable to the deposition of connective tissue elements in affected tissues. Elucidating the mechanisms that regulate the severity of schistosomiasis has been a major research objective over the past several years. Research conducted with DNA microarrays as well as investigations with a variety of gene knock-out mice have been particularly helpful in achieving this goal. A notable accomplishment in the past few years was the identification of interleukin-13 (IL-13) and the IL-13 receptor complex as central regulators of disease progression in schistosomiasis. Liver fibrogenesis is severely decreased in infected IL-13-deficient mice as well as in wildtype animals treated with IL-13 antagonists. In contrast, IL-13 effector function increases dramatically in IL-13 receptor alpha2 (IL-13Ralpha2)-deficient mice. These mice develop severe hepatic fibrosis, fail to downregulate granuloma formation in the chronic phase of S. mansoni infection, and succumb to the disease at an accelerated rate; thus, identifying the 'decoy' IL-13 receptor as a critical life sustaining 'off' switch for tissue damaging egg-induced inflammation.

Immunization of rats against Fasciola hepatica using crude antigens conjugated with Freund's adjuvant or oligodeoxynucleotides

Chronic Fasciola hepatica infection is correlated with the development of a T helper (Th2)-predominant immune response. To determine whether immunostimulatory CpG-containing oligodeoxynucleotides (CpG-ODN) or Freund's complete adjuvant (FCA), known to promote a Th1 (T helper 1) immune responses, could provide protection from F. hepatica infection, total homogenate (TH) of F. hepatica mixed with CpG-ODN or FCA were injected subcutaneously (s.c.) into Wistar rats. A F. hepatica-specific Th1-predominant immune response was induced with CpG-ODN or FCA in lymph nodes of immunized animals. Lymph node cells from TH-CpG-ODN or TH-FCA immunized rats showed increased antigen-specific proliferation with high levels of INFgamma, compared to lymphocytes from rats injected with TH alone. In contrast, these two groups of immunized animals did not modify IL-4 release by draining lymph node cells, when they were subsequently stimulated with TH in vitro. However, a significant reduction in the burden of flukes (76.7%) was only observed in rats immunized with TH-FCA. Conversely, immunization of rats with TH-CpG-ODN did not promote protection against the parasite. Therefore, even though CpG-ODNs and FCA induced Th1 type responses, only FCA provided a significant protection to rats infected with F. hepatica.

Expression of IL-18 and its receptor in human leukemia cells

The importance of IL-18, although clearly established in solid tumors, has not been fully elucidated in human hematopoietic neoplasms. Here we examined the mRNA and protein for IL-18 in eight human hematopoietic cell lines representing different lineages and neoplasms including leukemia, lymphoma and others. Our results revealed that IL-18 mRNA was expressed in these cells and that the corresponding protein was found in the cytoplasm. Seven of eight cell lines were also found to express two subunits of the IL-18 receptor (IL-18R) at varied levels. Furthermore, 29 out of 51 leukemia patients tested were observed to express IL-18R with 18/29 (62%) co-expression of both receptor and ligand. By blocking the IL-18 loop using specific antisense oligodeoxynucleotide (ASON) for IL-18 mRNA or anti-human IL-18R monoclonal antibody (McAbR), we were not able to demonstrate a marked inhibition on the most leukemic cell lines growth. Moreover, the potential proliferation in vitro of primary AML cells co-expressing IL-18 and its receptor was not significantly enhanced by recombinant human IL-18, suggesting that IL-18 is not apparently implicated in the proliferation of the leukemia cells via an autocrine loop. Additionally, we also found the effective modulating effect of M-CSF, IFN-alpha and TNF-alpha on IL-18R expression, implying an important in vivo effect of cytokines on IL-18-induced reaction. Moreover, the modulation of IL-18R expression was possibly irrelevant to IFN-gamma secretion induced by these cytokines.

CpG DNA in the prevention and treatment of infections

Microbial infection is sensed by Toll-like receptors (TLRs) on innate immune cells. Among the ten so far defined TLRs, TLR9 and its ligand are peculiar. TLR9 recognises bacterial DNA characterised by the abundance of unmethylated CpG dinucleotides, which distinguish bacterial DNA (CpG DNA) from mammalian DNA. Moreover, TLR9 shows a restricted cellular and subcellular pattern of expression. In contrast to other TLR agonists, CpG DNA is superior in activation of dendritic dells and induction of costimulatory cytokines such as interleukin (IL)-12 and IL-18. This qualifies CpG DNA as a Th1-promoting adjuvant. During infection, recognition of CpG DNA of intracellular pathogens skews and fine-tunes the ongoing immune response and induces long-lasting Th1 milieus. Thus, CpG DNA might play an important role in driving the immune system to a Th1 profile, preventing undesired Th2 milieus that might favour induction of allergic responses. Since CpG DNA can be synthesised with high purity and sequence fidelity, synthetic CpG DNA will become an important agent for Th1 instruction and be an effective adjuvant during vaccination.

Progress towards a vaccine for schistosomiasis

Schistosomiasis continues to be a significant health problem, especially in Africa. While the recent World Health Assembly resolution to apply mass drug treatment of school age children in endemic areas is a very promising development, a preferable long-term solution would be provided by a protective vaccine. Encouragingly, one vaccine, Bilhvax, is in phase II trials. However, there is a danger that momentum towards the goal of developing a vaccine against schistosomiasis is dissipating. This article reviews the current situation in this important area of schistosomiasis research.

CpG DNA as a vaccine adjuvant

Synthetic oligodeoxynucleotides containing unmethylated CpG motifs act as immune adjuvants, accelerating and boosting antigen-specific antibody responses by up to 500-fold. CpG motifs promote the production of T-helper 1 and pro-inflammatory cytokines and induce the maturation/activation of professional antigen-presenting cells (including macrophages and dendritic cells). These effects are optimized by maintaining close physical contact between the CpG DNA and the immunogen. Coadministering CpG DNA with a variety of vaccines has improved protective immunity in animal challenge models. Ongoing clinical studies indicate that CpG oligodeoxynucleotides are safe and well-tolerated when administered as adjuvants to humans and in some cases increase vaccine-induced immune responses.

Bacterial CpG-DNA licenses TLR9

The family of Toll-like receptors (TLRs) plays an important role in the innate immune response to pathogens. TLRs sense pathogen associated molecular patterns (PAMP) and lead to the stimulation of immune cells. In man, so far ten members (TLR1-10) have been reported. This review focuses on TLR9 which is an essential component for the recognition of bacterial CpG-DNA. Expression of TLR9 and structural consideration as well as direct ligand interaction of TLR9 and CpG-DNA are discussed.

Immunomodulatory effects of CpG oligodeoxynucleotides on established th2 responses

CpG oligodeoxynucleotides (CpG ODNs) are known to induce type 1 T-helper-cell (Th1) responses. We have previously demonstrated that CpG ODNs administered during sensitization prevent Th2-mediated eosinophilic airway inflammation in vivo. We also reported that key Th1 cytokines, gamma interferon (IFN-gamma) and interleukin 12 (IL-12), are not necessary for this protection. Recent in vivo data suggest that CpG ODNs might also reverse established pulmonary eosinophilia. In order to clarify how CpG ODNs can inhibit established Th2 responses, we evaluated the cytokine production from splenocytes from antigen- and alum-immunized mice. Restimulation with antigen induced IL-5, which was clearly inhibited by coculture with CpG ODNs in a concentration-dependent manner. CpG ODNs also induced IFN-gamma, but in a concentration-independent manner. The inhibition of IL-5 production was not mediated through natural killer cells or via CD8(+) T lymphocytes. Although IFN-gamma plays an important role in inhibition of antigen-induced IL-5 production by CpG ODNs, IFN-gamma was not the sole factor in IL-5 inhibition. CpG ODNs also induced IL-10, and this induction correlated well with IL-5 inhibition. Elimination of IL-10 reduced the anti-IL-5 effect of CpG ODNs, although incompletely. This may be because IFN-gamma, induced by CpG ODNs, is also inhibited by IL-10, serving as a homeostatic mechanism for the Th1-Th2 balance. Overproduction of IFN-gamma was downregulated by CpG ODN-induced IL-10 via modulation of IL-12 production. These data suggest that CpG ODNs may inhibit established Th2 immune responses through IFN-gamma and IL-10 production, the latter serving to regulate excessive Th1 bias. These properties of CpG ODNs might be a useful feature in the development of immunotherapy adjuvants against allergic diseases such as asthma.

Immunopharmacology of CpG DNA

Recognition of danger of infection by innate immune cells is a prerequisite to combat infections and to activate T and B cells. Pathogen-associated molecular patterns (PAMP) play a fundamental role in this process. PAMPs are sensed by at least ten different Toll-like receptors (TLR). Within the realm of PAMPs, CpG DNA that is recognized by TLR-9 has an outstanding propensity to induce a milieu that favors activation of T lymphocytes and biases Th1-dominated immune responses. Therefore CpG DNA has become a promising immuno-therapeutical candidate to assist and to direct immune responses such as in vaccination or modulation of allergic responses. As opposed to other PAMPs, CpG DNA can be synthesized with defined purity and base composition. Moreover, chemical substitutions can confer new qualities to synthetic CpG DNA.

The immunobiology of schistosomiasis

Schistosomes are parasitic worms that are a prime example of a complex multicellular pathogen that flourishes in the human host despite the development of a pronounced immune response. Understanding how the immune system deals with such pathogens is a daunting challenge. The past decade has seen the use of a wide range of new approaches to determine the nature and function of the immune response to schistosomes. Here, we attempt to summarize advances in our understanding of the immunology of schistosomiasis, with the bulk of the review reflecting the experimental focus on Schistosoma mansoni infection in mice.

Generation of Th1 immune responses to inactivated, gp120-depleted HIV-1 in mice with a dominant Th2 biased immune profile via immunostimulatory [correction of imunostimulatory] oligonucleotides--relevance to AIDS vaccines in developing countries

Vaccination against HIV-1 of hosts with a dominant Th2 immune profile may fail to induce essential protective Th1 immune responses. By using Schistosoma-infected mice, with a pre-existent Th2 immune background, we demonstrate that oligodeoxynucleotides (ODN) containing unmethylated cytosine-phosphate-guanosine (CpG) immunostimulatory sequences co-administered with inactivated, gp120-depleted HIV-1 viral particles (HIV-1 immunogen) lead to potent Th1 anti-HIV-1 immune responses overcoming the Th2 bias. In contrast, Schistosoma-infected mice immunized with HIV-1 immunogen in incomplete Freund's adjuvant only, induced Th2 anti-HIV-1 immune responses. These findings strongly support the advisability of using CpG ODN as a Th1 inducing adjuvant when immunizing human populations with a strong pre-existent Th2 immune profile.

CpG motifs in bacterial DNA and their immune effects

Unmethylated CpG motifs are prevalent in bacterial but not vertebrate genomic DNAs. Oligodeoxynucleotides (ODN) containing CpG motifs activate host defense mechanisms leading to innate and acquired immune responses. The recognition of CpG motifs requires Toll-like receptor (TLR) 9, which triggers alterations in cellular redox balance and the induction of cell signaling pathways including the mitogen activated protein kinases (MAPKs) and NF kappa B. Cells that express TLR-9, which include plasmacytoid dendritic cells (PDCs) and B cells, produce Th1-like proinflammatory cytokines, interferons, and chemokines. Certain CpG motifs (CpG-A) are especially potent at activating NK cells and inducing IFN-alpha production by PDCs, while other motifs (CpG-B) are especially potent B cell activators. CpG-induced activation of innate immunity protects against lethal challenge with a wide variety of pathogens, and has therapeutic activity in murine models of cancer and allergy. CpG ODN also enhance the development of acquired immune responses for prophylactic and therapeutic vaccination.

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.

Phosphodiester CpG oligonucleotides as adjuvants: polyguanosine runs enhance cellular uptake and improve immunostimulative activity of phosphodiester CpG oligonucleotides in vitro and in vivo

Bacterial DNA and oligonucleotides (ODN) containing CpG-motifs strongly activate cells of the immune system. Accordingly CpG-DNA is a powerful adjuvant in vaccination protocols for B-cell as well as for cytotoxic T-cell responses. A decisive propensity of CpG-DNA is its capacity to induce preferentially T helper type 1 (Th1)-dominated immune responses. To exert its function CpG-DNA has to be taken up by responsive cells, e.g. antigen-presenting cells (APC). The rate of uptake is influenced by the DNA's backbone modification and critically determines activity of CpG-DNA. CpG ODN with a phosphothioate backbone (PTO) are currently used for most in vivo and in vitro studies, since PTO modification protects ODN from the attack of nucleases. However, after administration of PTO-modified CpG-ODN long-lasting effects including lymphadenopathy as well as sustained local interferon-gamma (IFN-gamma) and interleukin-12 (IL-12) production have been reported. To circumvent these restrictions we investigated the effects of DNA sequence as well as DNA backbone modification on cellular uptake and resulting immunostimulation. We show here that uptake of phosphodiester (PO)-CpG-ODN can be strongly enhanced by poly guanosine runs added at the 3' end of the ODN. In addition these ODN showed an improved immunostimulatory activity in vivo and in vitro. This included protection of mice against lethal Th2-dependent leishmaniasis as well as priming of antigen specific Th1 responses. More importantly, guanosine-rich PO-CpG-ODN neither induced lymphadenopathy nor prolonged cytokine production after local administration. Since these improved PO ODN are efficient in vitro and in vivo and lack long lasting undesired effects they could be used preferably as adjuvants in vaccination protocols.

CpG containing oligodeoxynucleotides are potent adjuvants for parenteral vaccination with the fusion (F) protein of respiratory syncytial virus (RSV)

The feasibility of using oligodeoxynucleotides (ODN) containing unmethylated CpG motifs as parenteral adjuvants for subunit vaccines against RSV was tested in BALB/c mice. Compared with immunization with natural F protein adsorbed to aluminum hydroxide (F/AlOH) adjuvant alone, coadministration of F/AlOH with CpG ODN resulted in statistically significant increases in serum neutralization titers, an enhanced generation of splenic antigen-dependent killer cell precursors, and accelerated clearance of infectious virus from lungs 4 days after challenge. The statistically significant increases in serum IFNgamma and anti-F protein IgG2a titers, and significantly diminished pulmonary IL-5 and eosinophilia after challenge indicated that CpG ODN enhanced the ability of F/AlOH to elicit type 1 immune responses. F protein-specific serum IgE titers were also reduced. Further analysis of pulmonary inflammatory cells demonstrated an expansion of CD8(+) T cells, relative to the CD4(+) T cell compartment. The potency of CpG ODN was not adversely affected in gene knockout mice devoid of the p35 chain of the IL-12 heterodimer. Taken together, the results suggest a novel formulation for naïve recipients of F protein-based subunit vaccines that does not result in a type 2 phenotype.

Induction of experimental autoimmune thyroiditis in IL-12-/- mice

Granulomatous experimental autoimmune thyroiditis (G-EAT) is induced by transfer of mouse thyroglobulin (MTg)-sensitized spleen cells activated in vitro with MTg and anti-IL-2R or MTg and IL-12. Previous work suggested that IL-12 was required in vitro for development of G-EAT. To determine whether IL-12 was also required during the induction and/or effector phases, DBA/1 mice with a disrupted IL-12-P40 gene (IL-12(-/-)) were used for EAT induction. Cells from MTg-sensitized IL12(-/-) donors activated in vitro by MTg or MTg and anti-IL2R induced severe EAT in recipient mice. Compared with effector cells from IL-12(+/+) donors, effector cells from IL-12(-/-) donors induced thyroid lesions dominated by lymphocytes with minimal granulomatous changes. Thyroids of recipients of IL-12(-/-) cells expressed less IFN-gamma mRNA and more TGF-beta, IL-4, and IL-10 compared with recipients of IL-12(+/+) cells. When IL-12 was added during in vitro activation, cells from both IL-12(-/-) and IL-12(+/+) donors induced severe G-EAT, and expression of all cytokines except IL-12 was comparable in thyroids of both IL-12(+/+) and IL-12(-/-) recipients. Transfer of cells from IL-12(+/+) or IL-12(-/-) donors into IL-12(+/+) or IL-12(-/-) recipients indicated that IL-12 expressed in thyroids was derived from recipients. Thus, endogenous IL-12 is not absolutely essential for the sensitization and activation of EAT effector cells to induce severe EAT, although it is required in vitro to promote activation of cells to induce severe granulomatous histopathology.

Identification of a novel T-cell epitope in soluble egg antigen of Schistosoma japonicum

Identification of T-cell epitopes harbored in soluble egg antigen (SEA) of Schistosoma japonicum and study of the immunological properties are essential for understanding the immunopathology and the control of schistosomiasis. As a follow-up to our previous work, the 66- to 80-kDa fragment from SEA was partially digested with protease, fractionated by reverse-phase high-pressure liquid chromatography, and found to be carrying a peptide which stimulated proliferation and gamma interferon (IFN-gamma) production of Th1 clones specific to SEA. Sequence analysis showed that the peptide was composed of 12 amino acids lined up as DLAVELAYLGNL. A synthetic homologue induced proliferation and IFN-gamma and interleukin-2 (IL-2) production, but not IL-4 or IL-6 production, by the Th1 clones as well as by the spleen cells from SEA-immunized mice, thus indicating that the peptide carries a Th1 epitope of SEA.

Induction of antigen-specific Th1-biased immune responses by plasmid DNA in schistosoma-infected mice with a preexistent dominant Th2 immune profile

A requisite for vaccines to confer protection against intracellular infections such as Human Immunodeficiency Virus or Mycobacterium tuberculosis is their capacity to induce Th1 immune responses. However, they may fail to do so in Africa and South East Asia, where most individuals have a dominant preexistent Th2 immune profile, due to persistent helminthic parasitic infections, which may undermine any Th1 response. It is well established that DNA vaccines induce strong Th1 biased immune responses against an encoded antigen, depending on the route and mode of immunization. Here, we demonstrate that intradermal immunization with plasmid DNA encoding beta-gal (pCMV-LacZ) of Schistosoma-infected mice, with preexistent dominant Th2 immune background, induce a strong Th1 anti-beta-gal response, as opposed to immunized with beta-gal only. Importantly, the established protective Th2 immune response to schistosomes was not disrupted. These findings strongly support the possibility of using plasmid DNA as a Th1 inducing adjuvant when immunizing populations with a strong preexistent Th2 immune profile.

CpG oligodeoxynucleotides can reverse Th2-associated allergic airway responses and alter the B7.1/B7.2 expression in a murine model of asthma

CpG oligodeoxynucleotides (CpG-ODN) administered during Ag sensitization or before Ag challenge can inhibit allergic pulmonary inflammation and airway hyperreactivity in murine models of asthma. In this study, we investigated whether CpG-ODN can reverse an ongoing allergic pulmonary reaction in a mouse model of asthma. AKR mice were sensitized with conalbumin followed by two intratracheal challenges at weekly intervals. CpG-ODN was administered 24 h after the first Ag challenge. CpG-ODN administration reduced Ag-specific IgE levels, bronchoalveolar lavage fluid eosinophils, mucus production, and airway hyperreactivity. We found that postchallenge CpG-ODN treatment significantly increased IFN-gamma concentrations and decreased IL-13, IL-4, and IL-5 concentrations in bronchoalveolar lavage fluids and spleen cell culture supernatants. Postchallenge CpG-ODN treatment also increased B7.1 mRNA expression and decreased B7.2 mRNA expression in lung tissues. These results suggest that CpG-ODN may have potential for treatment of allergic asthma by suppressing Th2 responses during IgE-dependent allergic airway reactions. The down-regulation of Th2 responses by CPG-ODN may be associated with regulation of the costimulatory factors B7.1 and B7.2.

New age adjuvants and delivery systems for subunit vaccines

The dramatic advancements in the field of vaccinology has led to the formulation of chemically well defined vaccines composed of synthetic peptides and recombinant proteins derived from the immunologically dominant regions of the pathogens. Though these subunit vaccines are safer compared to the traditional vaccines they are known to be poorly immunogenic. This necessitates the use of adjuvants to enhance the immunogenicity of these vaccine formulations. The most common adjuvant for human use is alum. Research in the past has focused on the development of systemic immunity using conventional immunization protocols. In the present are, the emphasis is on the development and formulation of alternative adjuvants and delivery systems in generating systemic as well as mucosal immunity. This review mainly focuses on a variety of adjuvants (particulate as well as non-particulate) used with protective antigens of HIV, malaria, plague, leprosy using modified delivery vehicles. The experience of our laboratory and other researchers in this field clearly proves that these new age adjuvants and delivery systems undoubtedly generate enhanced immune response-both humoral and cell mediated. The choice of antigens, the nature of adjuvant used and the mode of delivery employed have a profound effect on the type of immune response generated. Besides the quantity, the quality of the antibodies generated also play a vital role in protection against these diseases. Some of the adjuvants and delivery systems used promoted high titre and affinity antibodies, which were shown to be cytophilic in nature, an important criteria in providing protection to the host. Thus the studies on these adjuvants/delivery systems with respect to various infectious diseases indicate their active role in efficient modulation of immune response along with safety and permissibility.

Cytokines in airway inflammation

With over 50 potential asthma mediators, cytokines are the latest group of substances which have been investigated for their potential role in this disease. The use of murine models of allergic inflammation has facilitated the investigation of the role of individual cytokines in this response. The use of targeted gene disruption, overexpression of genes and monoclonal antibodies directed against cytokines have allowed a detailed examination of the role cytokines play in IgE production, eosinophil recruitment and bronchial hyperresponsiveness, which are the characteristic features of the asthma phenotype. Despite the introduction of this new methodology, conflicting reports relating to the role of cytokines in allergic inflammation, highlight the complexity of allergic inflammation and challenge the notion that a single cytokine can explain the asthma phenotype.