Multiple effects of immunostimulatory DNA on T cells and the role of type I interferons

Interferome signature dynamics during the anti-dengue immune response: a systems biology characterization

Dengue virus (DENV) infection manifests as a febrile illness with three distinct phases: early acute, late acute, and convalescent. Dengue can result in clinical manifestations with different degrees of severity, dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Interferons (IFNs) are antiviral cytokines central to the anti-DENV immune response. Notably, the distinct global signature of type I, II, and III interferon-regulated genes (the interferome) remains uncharacterized in dengue patients to date. Therefore, we performed an in-depth cross-study for the integrative analysis of transcriptome data related to DENV infection. Our systems biology analysis shows that the anti-dengue immune response is characterized by the modulation of numerous interferon-regulated genes (IRGs) enriching, for instance, cytokine-mediated signaling (e.g., type I and II IFNs) and chemotaxis, which is then followed by a transcriptional wave of genes associated with cell cycle, also regulated by the IFN cascade. The adjunct analysis of disease stratification potential, followed by a transcriptional meta-analysis of the interferome, indicated genes such as IFI27, ISG15, and CYBRD1 as potential suitable biomarkers of disease severity. Thus, this study characterizes the landscape of the interferome signature in DENV infection, indicating that interferome dynamics are a crucial and central part of the anti-dengue immune response.

CpG Oligonucleotides as Vaccine Adjuvants

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides specifically designed to stimulate Toll-like receptor 9. TLR9 is expressed on human plasmacytoid dendritic cells and B cells and triggers an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. This chapter reviews recent progress in understanding the mechanism of action of CpG ODN and provides an overview of human clinical trial results using CpG ODN to improve vaccines for the prevention/treatment of cancer, allergy, and infectious disease.

Toll-like Receptors from the Perspective of Cancer Treatment

Toll-like receptors (TLRs) represent a family of pattern recognition receptors that recognize certain pathogen-associated molecular patterns and damage-associated molecular patterns. TLRs are highly interesting to researchers including immunologists because of the involvement in various diseases including cancers, allergies, autoimmunity, infections, and inflammation. After ligand engagement, TLRs trigger multiple signaling pathways involving nuclear factor-κB (NF-κB), interferon-regulatory factors (IRFs), and mitogen-activated protein kinases (MAPKs) for the production of various cytokines that play an important role in diseases like cancer. TLR activation in immune as well as cancer cells may prevent the formation and growth of a tumor. Nonetheless, under certain conditions, either hyperactivation or hypoactivation of TLRs supports the survival and metastasis of a tumor. Therefore, the design of TLR-targeting agonists as well as antagonists is a promising immunotherapeutic approach to cancer. In this review, we mainly describe TLRs, their involvement in cancer, and their promising properties for anticancer drug discovery.

Antibody Opsonization of a TLR9 Agonist-Containing Virus-like Particle Enhances In Situ Immunization

The immunologic and therapeutic effects of intratumoral (IT) delivery of a novel virus-like particle as a lymphoma immunotherapy were evaluated in preclinical studies with human cells and a murine model. CMP-001 is a virus-like particle composed of the Qβ bacteriophage capsid protein encapsulating an immunostimulatory CpG-A oligodeoxynucleotide TLR9 agonist. In vitro, CMP-001 induced cytokine production, including IFN-α from plasmacytoid dendritic cells, but only in the presence of anti-Qβ Ab. In vivo, IT CMP-001 treatment of murine A20 lymphoma enhanced survival and reduced growth of both injected and contralateral noninjected tumors in a manner dependent on both the ability of mice to generate anti-Qβ Ab and the presence of T cells. The combination of IT CMP-001 with systemic anti-PD-1 enhanced antitumor responses in both injected and noninjected tumors. IT CMP-001 alone or combined with anti-PD-1 augmented T cell infiltration in tumor-draining lymph nodes. We conclude IT CMP-001 induces a robust antitumor T cell response in an anti-Qβ Ab-dependent manner and results in systemic antitumor T cell effects that are enhanced by anti-PD-1 in a mouse model of B cell lymphoma. Early-phase clinical evaluation of CMP-001 and anti-PD-1 combination therapy in lymphoma will begin shortly, based in part on these results.

Chloroquine Treatment Suppresses Mucosal Inflammation in a Mouse Model of Eosinophilic Chronic Rhinosinusitis

PURPOSE

The Toll-like receptor 9 (TLR9) signaling pathway is involved in the pathogenesis of chronic rhinosinusitis (CRS) with nasal polyposis. The aim of this study was to assess the therapeutic potential of the TLR9 pathway inhibitor chloroquine in CRS mice.

METHODS

The expression of type I interferons (IFNs) in human CRS tissues was evaluated using quantitative polymerase chain reaction (qPCR), western blotting, and immunofluorescence. Mice were divided into 4 treatment groups: the control, nasal polyp (NP), chloroquine treatment (NP + Chlq), and dexamethasone treatment (NP + Dexa) groups. The effects of chloroquine on polyp formation and mucosal inflammation were examined by hematoxylin and eosin staining. The expression levels of type I IFN, B-cell activating factor (BAFF), TLR9, high mobility group box 1 (HMGB1), and proinflammatory cytokine expression levels were assessed using qPCR, western blot, or enzyme-linked immunosorbent assay.

RESULTS

IFN-α and IFN-β mRNA levels were significantly higher in patients with eosinophilic NPs (EPs) than in healthy individuals or non-EP patients. The polyp score, epithelial thickness, mucosal thickness, and the number of eosinophils in nasal mucosa were significantly higher in the NP group compared with the control, NP + Chlq, and NP + Dexa groups. NP + Chlq or NP + Dexa significantly suppressed the induction of type I IFN and BAFF expression in the NP group; these treatments also significantly suppressed the induction of TLR9, HMGB1, interferon regulatory factors, interleukin (IL)-6, IL-1β, tumor necrosis factor-α, and Th cytokine expression in the NP group. The secreted levels of anti-dsDNA Immunoglobulin G (IgG) were significantly higher in the NP group than in the control, NP + Chlq, and NP + Dexa groups. There were significant positive correlations between BAFF and mRNA levels of IFN-α/β/the protein levels of anti-dsDNA IgG.

CONCLUSIONS

Chloroquine may be used for the treatment of patients with eosinophilic CRS.

In ovo administration of Toll-like receptor ligands encapsulated in PLGA nanoparticles impede tumor development in chickens infected with Marek's disease virus

One of the economically important diseases in the poultry industry is Marek's disease (MD) which is caused by Marek's disease virus (MDV). The use of current vaccines provides protection against clinical signs of MD in chickens. However, these vaccines do not prevent the transmission of MDV to susceptible hosts, hence they may promote the development of new virulent strains of MDV. This issue persuaded us to explore alternative approaches to control MD in chickens. Induction of innate responses at the early stage of life in the chicken may help to prevent or reduce MDV infection. Further, prophylactic use of Toll-like receptor ligands (TLR-Ls) has been shown to generate host immunity against infectious diseases. In this regard, encapsulation of TLR-Ls in Poly(d, l-lactic-co-glycolic acid) (PLGA) may further enhance host responses by controlled release of TLR-Ls for an extended period. Hence, in the current study, protective effects of encapsulated TLR4 and TLR21 ligands, LPS and CpG, respectively, were investigated against MD. Results indicated that administration of encapsulated CpG and LPS first at embryonic day (ED) 18, followed by post-hatch at 14 days-post infection (dpi) intramuscularly, diminished tumor incidence by 60% and 42.8%, respectively at 21dpi compared to the MDV only group. In addition, analysis of cytokine gene profiles of interferon (IFN)-α, IFN-β, IFN-γ, inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-18 and IL-10 in spleen and bursa of Fabricius at different time points suggests that TLR-Ls possibly triggered host responses through the expression of IL-1β and IL-18 to reduce tumor formation. However, further studies are needed to explore the role of these pro-inflammatory cytokines and other influencing elements like lymphocytes in the hindrance of tumor development by TLR-Ls treatment in chickens.

Antigen-dependent and -independent mechanisms of T and B cell hyperactivation during chronic HIV-1 infection

Continuous loss of CD4(+) T lymphocytes and systemic immune activation are hallmarks of untreated chronic HIV-1 infection. Chronic immune activation during HIV-1 infection is characterized by increased expression of activation markers on T cells, elevated levels of proinflammatory cytokines, and B cell hyperactivation together with hypergammaglobulinemia. Importantly, hyperactivation of T cells is one of the best predictive markers for progression toward AIDS, and it is closely linked to CD4(+) T cell depletion and sustained viral replication. Aberrant activation of T cells is observed mainly for memory CD4(+) and CD8(+) T cells and is documented, in addition to increased expression of surface activation markers, by increased cell cycling and apoptosis. Notably, the majority of these activated T cells are neither HIV specific nor HIV infected, and the antigen specificities of hyperactivated T cells are largely unknown, as are the exact mechanisms driving their activation. B cells are also severely affected by HIV-1 infection, which is manifested by major changes in B cell subpopulations, B cell hyperactivation, and hypergammaglobulinemia. Similar to those of T cells, the mechanisms underlying this aberrant B cell activation remain largely unknown. In this review, we summarized current knowledge about proposed antigen-dependent and -independent mechanisms leading to lymphocyte hyperactivation in the context of HIV-1 infection.

Cancer testis antigen vaccination affords long-term protection in a murine model of ovarian cancer

Sperm protein (Sp17) is an attractive target for ovarian cancer (OC) vaccines because of its over-expression in primary as well as in metastatic lesions, at all stages of the disease. Our studies suggest that a Sp17-based vaccine can induce an enduring defense against OC development in C57BL/6 mice with ID8 cells, following prophylactic and therapeutic treatments. This is the first time that a mouse counterpart of a cancer testis antigen (Sp17) was shown to be expressed in an OC mouse model, and that vaccination against this antigen significantly controlled tumor growth. Our study shows that the CpG-adjuvated Sp17 vaccine overcomes the issue of immunologic tolerance, the major barrier to the development of effective immunotherapy for OC. Furthermore, this study provides a better understanding of OC biology by showing that Th-17 cells activation and contemporary immunosuppressive T-reg cells inhibition is required for vaccine efficacy. Taken together, these results indicate that prophylactic and therapeutic vaccinations can induce long-standing protection against OC and delay tumor growth, suggesting that this strategy may provide additional treatments of human OC and the prevention of disease onset in women with a family history of OC.

Interferon type I responses in primary and secondary infections

The mammalian host responds to a microbial infection with a rapid innate immune reaction that is dominated by type I interferon (IFN-I) release. Most cells of vertebrates can respond to microbial attack with IFN-I production, but the cell type responsible for most of the systemic IFN-I release is thought to be plasmacytoid dendritic cells (pDCs). Besides its anti-microbial and especially anti-viral properties IFN-I also exerts a regulatory role on many facets of the sequential adaptive immune response. One of these is being the recently described partial, systemic activation of the vast majority of B and T lymphocytes in mice, irrespective of antigen reactivity. The biological significance of this partial activation of lymphocytes is at present speculative. Secondary infections occurring within a short time span of a primary infection fail to elicit a similar lymphocyte activation response due to a refractory period in systemic IFN-I production. This period of exhaustion in IFN-I responses is associated with an increased susceptibility of the host to secondary infections. The latter correlates with well-established clinical observations of heightened susceptibility of patients to secondary microbial infections after viral episodes.

The role of type I interferons in TLR responses

Recent advances in unravelling the complexities of the signalling pathways that constitute innate immunity have highlighted type I interferon as a key component in the response to infection. Here we focus on the emerging field of pattern-recognition receptor signalling, specifically Toll-like receptors and retinoic acid inducible gene-like helicases, from the perspective of this 50-year-old cytokine. The type I interferon gene family encompasses more than 20 subtypes, whose nature and properties have been extensively studied during its relatively long history. In this review we update and integrate available data on the mechanics of activation of the interferon genes and the role of this cytokine family in the innate immune response.

An indispensable role of type-1 IFNs for inducing CTL-mediated complete eradication of established tumor tissue by CpG-liposome co-encapsulated with model tumor antigen

We have evaluated the capacity of a novel, nanoparticle-based tumor vaccine to eradicate established tumors in mice. C57BL/6 mice were intradermally (i.d.) inoculated with ovalbumin (OVA)-expressing EG-7 tumor cells. When the tumor size reached 7-8 mm, the tumor-bearing mice were i.d. injected near the tumor-draining lymph node (DLN) with liposomes encapsulated with unmethylated cytosine-phosphorothioate-guanine containing oligodeoxynucleotides (CpG-ODN) (CpG-liposomes) co-encapsulated with OVA. This vaccination protocol markedly prevented the growth of the established tumor mass and approximately 50% of tumor-bearing mice became completely cured. Tumor eradication correlated with the generation of OVA/H-2K(b)-tetramer(+) CTLs in the tumor DLN and at the tumor site with specific cytotoxicity toward EG-7 cells. Interestingly, tetramer(+) CTLs failed to be induced in lymph node-deficient Aly/Aly mice. Thus, tetramer(+) CTLs appeared to be generated in the tumor DLN and subsequently migrated into the tumor site. In vivo antibody blocking experiments revealed that CD8(+) T cells, but not CD4(+) T, NK or NKT cells, were the major effector cells mediating tumor eradication. CTL induction was also inhibited when vaccinated tumor-bearing mice were treated with both anti-IFN-alpha and anti-IFN-beta mAbs but not with anti-IFN-alpha or anti-IFN-beta mAb alone. Neither IFN-gamma(-/-) nor IL-12(-/-) mice showed impaired induction of tetramer(+) CTLs. Thus, these findings revealed that CpG-ODN-induced IFN-alpha/beta, but not IL-12 or IFN-gamma, is critical for the generation of tumor-specific CTLs in response to vaccination. These results highlight the potential utility of CpG-liposomes co-encapsulated with protein tumor antigens as therapeutic vaccines in cancer patients.

Helicobacter pylori (H. pylori) molecular signature in conjunctival mucosa-associated lymphoid tissue (MALT) lymphoma

Conjunctival mucosa-associated lymphoid tissue (MALT) lymphoma is an extranodal marginal zone B-cell lymphoma that is characterized by an exaggerated clonal expansion of B cells, which implicate a pathological proliferative response to antigen(s) including bacteria. Helicobacter pylori (H. pylori) infection is recognized as one of the causative agents of gastric MALT lymphoma; however, it has not been reported in extra gastric MALT lymphoma. We studied 5 patients (4 adults and 1 child) with salmon-colored conjunctival lesions. One patient also had a history of abnormal bone marrow biopsy a year earlier with lymphoid aggregates involving 5% of the overall bone marrow. The conjunctival lesions of the 5 patients were biopsied. Histopathological diagnoses were consistent with conjunctival MALT lymphoma. Lymphoma and normal conjunctival cells were microdissected using laser capture microscopy or manual techniques. DNA was extracted and subjected to PCR amplification using H. pylori gene-specific primers from the urease B and vac/m2 gene. Cells from chronic conjunctivitis (normal lymphocytes), conjunctival human T-cell lymphotropic virus type-1/adult T-cell leukemia/lymphoma (HTLV-1/ATL), and orbital B-cell lymphoma were also microdissected, processed and analyzed. PCR amplification and Southern blot hybridization demonstrated H. pylori DNA in the conjunctival MALT lymphoma cells of 4/5 cases. The negative case was the one with a history of abnormal bone marrow. In contrast, H. pylori gene was not detected in normal conjunctival cells from the cases of MALT lymphoma or the lymphocytes, ATL and orbital B-lymphoma cells from the controls. These data suggest that H. pylori may play a role in conjunctival MALT lymphoma.

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.

Activation of cytotoxic lymphocytes by interferon-alpha: role of oxygen radical-producing mononuclear phagocytes

A significant part of the therapeutic benefit of interferon-alpha (IFN-alpha) therapy in malignant diseases and in chronic viral infections is assumed to result from activation of lymphocytes with natural killer (NK) and T cell phenotype. In tumor tissue and in chronically infected tissue, the function and viability of these lymphocytes are frequently impaired. Mononuclear phagocyte (MP)-derived reactive oxygen species (ROS) have been proposed to contribute to the lymphocyte suppression in these tissues. Here, we report that three types of human cytotoxic lymphocytes of relevance to immunoactivation by IFN-alpha, CD3epsilon+/8+/56- T cells, CD3epsilon-/56+ NK cells, and CD3epsilon+/56+ NK/T cells became anergic to IFN-alpha induction of the cell-surface activation marker CD69 after exposure to autologous MPs in vitro. In addition to their incapacity to express CD69, cytotoxic lymphocytes acquired features characteristic of apoptosis after incubation with MPs. The lymphocyte apoptosis and nonresponsiveness to IFN-alpha were prevented by two inhibitors of reduced nicotinamide adenine dinucleotide phosphate oxidase-dependent formation of ROS in MPs, histamine dihydrochloride and diphenylene ionodonium, as well as by catalase, a scavenger of ROS. We conclude that MP-derived ROS may negatively affect IFN-alpha-induced immunostimulation and propose that ROS inhibitors or scavengers may be useful to improve lymphocyte activation during treatment with IFN-alpha.

Modulation of Toll-like Receptor 9 Responses through Synthetic Immunostimulatory Motifs of DNA

Bacterial, plasmid, and synthetic DNA containing unmethylated CpG dinucleotides in specific sequence contexts activate the vertebrate innate immune system. A pattern recognition receptor (PRR), toll-like receptor 9 (TLR9), recognizes CpG DNA and activates signaling cascade leading to the secretion of a number of cytokines and chemokines. Our extensive structure-immunostimulatory activity relationship studies showed that a number of synthetic pyrimidine (Y) and purine (R) nucleotides are accepted by the receptor as substitutes for natural deoxycytidine and deoxyguanosine in a CpG dinucleotide. These studies permitted development of synthetic immunostimulatory motifs YpG, CpR, and YpR and established the nucleotide motif recognition pattern of the receptor. A number of site-specific chemical modifications in the flanking sequences to the CpG dinucleotide permitted modulation of immunostimulatory affects in a predictable manner. Our studies also showed that TLR9 recognizes and reads the CpG DNA sequence from the 5'-end. Design of oligonucleotides with two 5'-ends, immunomers, resulted in potent immunomodulatory agents with distinct cytokine profiles. Immunomers containing synthetic immunostimulatory motifs produced different cytokine induction profiles compared with natural CpG motifs. Importantly, some of these synthetic motifs showed optimal activity in both mouse and human systems without requiring to change sequences, suggesting overriding the species-dependent specificity of the receptor by the use of synthetic motifs. In this article, we review current understanding of structural recognition and functional modulation of TLR9 receptor by second-generation immunomodulatory oligonucleotides and their potential application as wide spectrum therapeutic agents.

Intratumor CpG-oligodeoxynucleotide injection induces protective antitumor T cell immunity

Tumor cells are typically poorly immunogenic. The same mechanisms that evolved to avoid the induction of immune responses against self tissues, and, hence, autoimmune disease, also have to be overcome for immune therapy of cancer. Toll-like receptor-activating microbial products such as CpG motif containing DNA are among the primary stimuli that the immune system uses to distinguish between infectious nonself (that is to be attacked) and noninfectious self (that must not be attacked). We tested in a murine RMA lymphoma/C57BL/6 model whether providing the infectious nonself context in a tumor-by injecting CpG-oligodeoxynucleotides directly into the tumor-would elicit a protective antitumor response. Complete remission of established solid tumors was achieved in immune competent mice, but not in T cell/B cell-deficient RAG-1 knockout mice. Intratumor injection of CpG-oligodeoxynucleotides was shown to induce a tumor-specific CD4(+) and CD8(+) T cell response of the type 1 effector class, and T cells adoptively transferred the protection to RAG-1 knockout mice. The data show that intratumor injection of CpG-oligodeoxynucleotides is a promising strategy for rendering tumors immunogenic.

CpG-A and CpG-B oligonucleotides differentially enhance human peptide-specific primary and memory CD8+ T-cell responses in vitro

Two distinct types of CpG oligodeoxynucleotide (ODN) have been identified that differ in their capacity to stimulate antigen-presenting cells: CpG-A induces high amounts of interferon-alpha (IFN-alpha) and IFN-beta in plasmacytoid dendritic cells (PDCs), whereas CpG-B induces PDC maturation and is a potent activator of B cells but stimulates only small amounts of IFN-alpha and IFN-beta. Here we examined the ability of these CpG ODNs to enhance peptide-specific CD8+ T-cell responses in human peripheral blood mononuclear cells (PBMCs). The frequency of influenza matrix-specific "memory" CD8+ T cells was increased by both types of CpG ODN, whereas the frequency of Melan-A specific "naive" CD8+ T cells increased on stimulation with CpG-B but not with CpG-A. The presence of PDCs in PBMCs was required for this CpG ODN-mediated effect. The expanded cells were cytotoxic and produced IFN- on peptide restimulation. Soluble factors induced by CpG-A but not CpG-B increased the granzyme-B content and cytotoxicity of established CD8+ T-cell clones, each of which was IFN-alpha/-beta dependent. In conclusion, CpG-B seems to be superior for priming CD8+ T-cell responses, and CpG-A selectively enhances memory CD8+ T-cell responses and induces cytotoxicity. These results demonstrate distinct functional properties of CpG-A and CpG-B with regard to CD8 T cells.

Innate immune responses induced by CpG oligodeoxyribonucleotide stimulation of ovine blood mononuclear cells

Examples exist in the literature that demonstrate that treatment with immunostimulatory cytosine-phosphate-guanosine (CpG)-DNA can protect mice against infection by intracellular pathogens. There are, however, few studies reporting that CpG-DNA offers similar disease protection in other species. In this study, we assessed the potential of a class A and class B CpG oligodeoxynucleotide (ODN) to induce innate immune responses in sheep, an outbred species. Using peripheral blood mononuclear cells, we have for the first time demonstrated CpG-ODN-induced innate immune responses, including natural-killer-like activity [non-major histocompatibility complex (MHC)-restricted cytotoxicity], interferon-alpha secretion and 2'-5'A oligoadenylate synthetase activity, that could contribute to immune protection in sheep. The type and magnitude of these responses were dependent on ODN class and non-MHC-restricted killing was not associated with interferon-gamma production. The latter observation is in contrast with observations reported for mice and humans. These observations support the conclusion that differences in CpG-ODN-induced responses exist among species and that specific ODN sequences can significantly influence innate immune responses.

Lymphocyte activation in the lungs of SP-D null mice

Surfactant protein D (SP-D) appears to play an important role in regulating local pulmonary inflammatory responses to pathogens. There is also in vitro evidence that SP-D may suppress local T cell responses. However, the role of SP-D in regulating T cell responses directly in the lung has not been previously evaluated in vivo. SP-D(-)(/-) mice demonstrate peribronchial and perivascular accumulations of lymphocytes. Therefore, we investigated the functional status and abundance of intrapulmonary lymphocytes in SP-D(-)(/-) mice. By morphometric analysis, SP-D(-)(/-) mice demonstrated increased numbers of airway- and vessel-associated lymphocytes without increases in interstitial lymphocytes. There was increased proliferative activity of lymphocytes isolated by enzymatic disassociation of minced lung. Flow cytometry was used to determine the number and functional activation status of intrapulmonary CD4(+) and CD8(+) T cells, as well as B cells and NK cells. Cytokine expression patterns in lung tissues were evaluated using RNase protection assays, reverse transcriptase/polymerase chain reaction, and enzyme-linked immunosorbent assay. There was marked T cell activation in the lungs of SP-D(-)(/-) mice, as reflected by an increased percentage of both CD4(+) and CD8(+) T cells expressing CD69 and CD25. BAL CD4 lymphocytes were increased and the fraction expressing CD69 was also increased. Although there were increases in BAL CD8 lymphocytes, apparent increases in CD69-positive CD8 lymphocytes did not reach statistical significance. In contrast, splenic T cells were not activated in SPD(-)(/-) mice. Of the proinflammatory cytokines evaluated, only interleukin (IL)-12 and IL-6 expression were consistently upregulated in the lungs of SPD(-)(/-) mice. Increased IL-2 expression was apparent but did not reach statistical significance. We conclude that the lack of local pulmonary production of SP-D leads to a state of persistent T cell activation, possibly in response to exogenous antigens. This study therefore provides further evidence of the important local immunoregulatory role of SP-D in vivo.

Medicinal chemistry and therapeutic potential of CpG DNA

The observation that oligodeoxynucleotides containing CpG dinucleotides (CpG DNA) exhibit several immunological effects has led to their use as therapeutic agents and adjuvants for various diseases. Several CpG DNA drug candidates are currently being evaluated, either as monotherapies or as adjuvants (with vaccines, antibodies, antigens and allergens), in preclinical and clinical trials against cancers, viral and bacterial infections, allergies and asthma. Knowledge gained from studies of the medicinal chemistry of CpG DNA has provided a basis for designing a second generation of CpG DNA agents with desirable cytokine-inducing and potent immunomodulatory activity. This article reviews recent progress in understanding the effects of CpG DNA, the medicinal chemistry of CpG DNA, and its possible therapeutic applications.

Amb a 1-linked CpG oligodeoxynucleotides reverse established airway hyperresponsiveness in a murine model of asthma

BACKGROUND

Recently, it has been demonstrated that immunostimulatory DNA sequences (ISS) containing CpG motifs prevent the development of allergic airway responses in murine models of disease. However, few studies have addressed the issue of whether these agents will reverse established Tm(H)2-driven allergic airway responses.

OBJECTIVE

The aim of this study was to determine whether intradermal delivery of an immunogenic protein of ragweed pollen linked to an immunostimulatory DNA sequence could reverse an established allergic response in the mouse lung.

METHODS

Mice sensitized and challenged with ragweed pollen extract were treated intradermally twice at 1-week intervals with an ISS chemically linked to Amb a 1 (Amb a 1-ISS). One week after the Amb a 1-ISS treatment, mice were rechallenged intratracheally with ragweed extract, and airway responses were assessed.

RESULTS

Amb a 1-ISS treatment of ragweed-sensitized and ragweed-challenged mice significantly reversed allergen-induced airway hyperresponsiveness and suppressed the total number of eosinophils in bronchoalveolar lavage fluid. The inhibitory effect of Amb a 1-ISS was associated with a marked increase in IFN-gamma levels by Amb a 1-stimulated splenocytes and a shift in the antibody profile from a T(H)2-directed IgG1 response to a T(H)1-directed IgG2a response. Interestingly, the inhibitory effect of Amb a 1-ISS on allergen-driven airway hyperresponsiveness was independent of suppression of T(H)2 cytokine production.

CONCLUSION

These results demonstrate that intradermal delivery of allergen-specific DNA conjugates can reverse established allergic responses in the murine lung, supporting their potential use in the treatment of human asthma.