Transforming growth factor-beta secreted from CD4(+) T cells ameliorates antigen-induced eosinophilic inflammation. A novel high-dose tolerance in the trachea

Protective efficacy and safety of radiation-attenuated and chemo-attenuated Plasmodium Falciparum sporozoite vaccines against controlled and natural malaria infection: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

Despite the significant burden of Plasmodium falciparum (Pf) malaria and the licensure of two vaccines for use in infants and young children that are partially effective in preventing clinical malaria caused by Pf, a highly effective vaccine against Pf infection is still lacking. Live attenuated vaccines using Pf sporozoites as the immunogen (PfSPZ Vaccines) hold promise for addressing this gap. Here we review the safety and efficacy of two of the most promising PfSPZ approaches: PfSPZ Vaccine (radiation attenuated PfSPZ) and PfSPZ-CVac (chemo-attenuated PfSPZ).

METHODS

We conducted a systematic review and meta-analysis by searching PubMed, EMBASE, SCOPUS, CENTRAL, and WOS until 22nd December 2021. We included randomized controlled trials (RCTs) of these two vaccine approaches that measured protection against parasitaemia following controlled human malaria infection (CHMI) in malaria-naive and malaria-exposed adults or following exposure to naturally transmitted Pf malaria in African adults and children (primary outcome) and that also measured the incidence of solicited and unsolicited adverse events as indicators of safety and tolerability after vaccination (secondary outcome). We included randomized controlled trials (RCTs) that measured the detected parasitaemia after vaccination (primary outcome) and the incidence of various solicited and unsolicited adverse events (secondary outcome). The quality of the included RCTs using the Cochrane ROB 1 tool and the quality of evidence using the GRADE system were evaluated. We pooled dichotomous data using the risk ratio (RR) for development of parasitemia in vaccinees relative to controls as a measure of vaccine efficacy (VE), including the corresponding confidence interval (CI). This study was registered with PROSPERO (CRD42022308057).

RESULTS

We included 19 RCTs. Pooled RR favoured PfSPZ Vaccine (RR: 0.65 with 95% CI [0.53, 0.79], P = 0.0001) and PfSPZ-table (RR: 0.42 with 95% CI [0.27, 0.67], P = 0.0002) for preventing parasitaemia, relative to normal saline placebo. Pooled RR showed no difference between PfSPZ Vaccine and the control in the occurrence of any solicited adverse event (RR: 1.00 with 95% CI [0.82, 1.23], P = 0.98), any local solicited adverse events (RR: 0.73 with 95% CI [0.49, 1.08], P = 0.11), any systemic solicited adverse events (RR: 0.94 with 95% CI [0.75, 1.17], P = 0.58), and any unsolicited adverse event (RR: 0.93 with 95% CI [0.78, 1.10], P = 0.37).

CONCLUSION

PfSPZ and PfSPZ-CVacs showed comparable efficacy. Therefore, they can introduce a promising strategy for malaria prophylaxis, but more large-scale field trials are required to sustain efficacy and yield clinically applicable findings.

Increase of Dose Associated With Decrease in Protection Against Controlled Human Malaria Infection by PfSPZ Vaccine in Tanzanian Adults

BACKGROUND

A vaccine would be an ideal tool for reducing malaria's impact. PfSPZ Vaccine (radiation attenuated, aseptic, purified, cryopreserved Plasmodium falciparum [Pf] sporozoites [SPZ]) has been well tolerated and safe in >1526 malaria-naive and experienced 6-month to 65-year-olds in the United States, Europe, and Africa. When vaccine efficacy (VE) of 5 doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine was assessed in adults against controlled human malaria infection (CHMI) in the United States and Tanzania and intense field transmission of heterogeneous Pf in Mali, Tanzanians had the lowest VE (20%).

METHODS

To increase VE in Tanzania, we increased PfSPZ/dose (9 × 105 or 1.8 × 106) and decreased numbers of doses to 3 at 8-week intervals in a double blind, placebo-controlled trial.

RESULTS

All 22 CHMIs in controls resulted in parasitemia by quantitative polymerase chain reaction. For the 9 × 105 PfSPZ group, VE was 100% (5/5) at 3 or 11 weeks (P < .000l, Barnard test, 2-tailed). For 1.8 × 106 PfSPZ, VE was 33% (2/6) at 7.5 weeks (P = .028). VE of dosage groups (100% vs 33%) was significantly different (P = .022). Volunteers underwent repeat CHMI at 37-40 weeks after last dose. 6/6 and 5/6 volunteers developed parasitemia, but time to first parasitemia was significantly longer than controls in the 9 × 105 PfSPZ group (10.89 vs 7.80 days) (P = .039), indicating a significant reduction in parasites in the liver. Antibody and T-cell responses were higher in the 1.8 × 106 PfSPZ group.

CONCLUSIONS

In Tanzania, increasing the dose from 2.7 × 105 to 9 × 105 PfSPZ increased VE from 20% to 100%, but increasing to 1.8 × 106 PfSPZ significantly reduced VE.

CLINICAL TRIALS REGISTRATION

NCT02613520.

Radiation-induced immune responses: mechanisms and therapeutic perspectives

Recent advancement in the radiotherapy technology has allowed conformal delivery of high doses of ionizing radiation precisely to the tumors while sparing large volume of the normal tissues, which have led to better clinical responses. Despite this technological advancement many advanced tumors often recur and they do so within the previously irradiated regions. How could tumors recur after receiving such high ablative doses of radiation? In this review, we outlined how radiation can elicit anti-tumor responses by introducing some of the cytokines that can be induced by ionizing radiation. We then discuss how tumor hypoxia, a major limiting factor responsible for failure of radiotherapy, may also negatively impact the anti-tumor responses. In addition, we highlight how there may be other populations of immune cells including regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs) that can be recruited to tumors interfering with the anti-tumor immunity. Finally, the impact of irradiation on tumor hypoxia and the immune responses according to different radiotherapy regimen is also delineated. It is indeed an exciting time to see that radiotherapy is being combined with immunotherapy in the clinic and we hope that this review can add an excitement to the field.

Strategies of mucosal immunotherapy for allergic diseases

Incidences of allergic disease have recently increased worldwide. Allergen-specific immunotherapy (SIT) has long been a controversial treatment for allergic diseases. Although beneficial effects on clinically relevant outcomes have been demonstrated in clinical trials by subcutaneous immunotherapy (SCIT), there remains a risk of severe and sometimes fatal anaphylaxis. Mucosal immunotherapy is one advantageous choice because of its non-injection routes of administration and lower side-effect profile. This study reviews recent progress in mucosal immunotherapy for allergic diseases. Administration routes, antigen quality and quantity, and adjuvants used are major considerations in this field. Also, direct uses of unique probiotics, or specific cytokines, have been discussed. Furthermore, some researchers have reported new therapeutic ideas that combine two or more strategies. The most important strategy for development of mucosal therapies for allergic diseases is the improvement of antigen formulation, which includes continuous searching for efficient adjuvants, collecting more information about dominant T-cell epitopes of allergens, and having the proper combination of each. In clinics, when compared to other mucosal routes, sublingual immunotherapy (SLIT) is a preferred choice for therapeutic administration, although local and systemic side effects have been reported. Additionally, not every allergen has the same beneficial effect. Further studies are needed to determine the benefits of mucosal immunotherapy for different allergic diseases after comparison of the different administration routes in children and adults. Data collected from large, well-designed, double-blind, placebo-controlled, and randomized trials, with post-treatment follow-up, can provide robust substantiation of current evidence.

In vivo disruption of TGF-beta signaling by Smad7 in airway epithelium alleviates allergic asthma but aggravates lung carcinogenesis in mouse

Background

TGF-β has been postulated to play an important role in the maintenance of epithelial homeostasis and the development of epithelium-derived cancers. However, most of previous studies are mainly focused on the function of TGF-β in immune cells to the development of allergic asthma and how TGF-β signaling in airway epithelium itself in allergic inflammation is largely unknown. Furthermore, the in vivo TGF-β function specifically in the airway epithelium during lung cancer development has been largely elusive.

Methodology/Principal Findings

To evaluate the in vivo contribution of TGF-β signaling in lung epithelium to the development of allergic disease and lung cancer, we generated a transgenic mouse model with Smad7, an intracellular inhibitor of TGF-β signaling, constitutively expressed in mouse airway Clara cells using a mouse CC10 promoter. The mice were subjected to the development of OVA-induced allergic asthma and urethane-induced lung cancer. The Smad7 transgenic animals significantly protected from OVA-induced asthma, with reduced airway inflammation, airway mucus production, extracellular matrix deposition, and production of OVA-specific IgE. Further analysis of cytokine profiles in lung homogenates revealed that the Th2 cytokines including IL-4, IL-5 and IL-13, as well as other cytokines including IL-17, IL-1, IL-6, IP10, G-CSF, and GM-CSF were significantly reduced in the transgenic mice upon OVA induction. In contrast, the Smad7 transgenic animals had an increased incidence of lung carcinogenesis when subjected to urethane treatment.

Conclusion/Significance

These studies, therefore, demonstrate for the first time the in vivo function of TGF-β signaling specifically in airway epithelium during the development of allergic asthma and lung cancer.

The role of dendritic cells and regulatory T cells in the regulation of allergic asthma

Airways hyperresponsiveness (AHR) is one of the major clinical features of allergic airways disease including allergic asthma, however the immunological mechanisms leading to the induction and regulation of this disorder are not fully understood. In this review we will summarise the evidence of a number of studies, principally in murine models of AHR, suggesting a central role for respiratory tract dendritic cells (RTDC) in the induction of AHR through the generation of lung-homing, allergen-specific effector T cells. We will also summarise the evidence supporting a role for regulatory T cells in the attenuation of AHR and will propose that, as a counterpoint to their capacity to induce AHR, RTDC may also play a role in the attenuation of AHR through the generation of regulatory T cells (T(reg)). A better understanding of the relationship between the physiological and immunological responses to allergen-induced AHR attenuation, and particularly the role of RTDC and T(reg) in this process, will be essential for the development of new treatments and therapies.

Scientific rationale for the Finnish Allergy Programme 2008-2018: emphasis on prevention and endorsing tolerance

In similarity to many other western countries, the burden of allergic diseases in Finland is high. Studies worldwide have shown that an environment rich in microbes in early life reduces the subsequent risk of developing allergic diseases. Along with urbanization, such exposure has dramatically reduced, both in terms of diversity and quantity. Continuous stimulation of the immune system by environmental saprophytes via the skin, respiratory tract and gut appears to be necessary for activation of the regulatory network including regulatory T-cells and dendritic cells. Substantial evidence now shows that the balance between allergy and tolerance is dependent on regulatory T-cells. Tolerance induced by allergen-specific regulatory T-cells appears to be the normal immunological response to allergens in non atopic healthy individuals. Healthy subjects have an intact functional allergen-specific regulatory T-cell response, which in allergic subjects is impaired. Evidence on this exists with respect to atopic dermatitis, contact dermatitis, allergic rhinitis and asthma. Restoration of impaired allergen-specific regulatory T-cell response and tolerance induction has furthermore been demonstrated during allergen-specific subcutaneous and sublingual immunotherapy and is crucial for good therapeutic outcome. However, tolerance can also be strengthened unspecifically by simple means, e.g. by consuming farm milk and spending time in nature. Results so far obtained from animal models indicate that it is possible to restore tolerance by administering the allergen in certain circumstances both locally and systemically. It has become increasingly clear that continuous exposure to microbial antigens as well as allergens in foodstuffs and the environment is decisive, and excessive antigen avoidance can be harmful and weaken or even prevent the development of regulatory mechanisms. Success in the Finnish Asthma Programme was an encouraging example of how it is possible to reduce both the costs and morbidity of asthma. The time, in the wake of the Asthma Programme, is now opportune for a national allergy programme, particularly as in the past few years, fundamentally more essential data on tolerance and its mechanisms have been published. In this review, the scientific rationale for the Finnish Allergy Programme 2008-2018 is outlined. The focus is on tolerance and how to endorse tolerance at the population level.

Attenuation of allergen-induced airway hyperresponsiveness is mediated by airway regulatory T cells

Understanding the mechanisms involved in respiratory tolerance to inhaled allergens could potentially result in improved therapies for asthma and allergic diseases. Airway hyperresponsiveness (AHR) is a major feature of allergic asthma, thus the aim of the current study was to investigate mechanisms underlying suppression of allergen-induced AHR during chronic allergen exposure. Adult BALB/c mice were systemically sensitized with ovalbumin (OVA) in adjuvant and then challenged with a single 3 or 6 wk of OVA aerosols. Airway and parenchymal responses to inhaled methacholine (MCh), inflammatory cell counts, cytokines, OVA-specific IgE and IgG(1), parenchymal histology, and numbers of airway CD4(+)69(+) activated and CD4(+)25(+)FoxP3(+) regulatory T (Treg) cells were assessed 24 h after the final aerosol. Single OVA challenge resulted in AHR, eosinophilia, increased serum OVA-specific IgE, and T helper 2 (Th2) cytokines in bronchoalveolar lavage (BAL) but no difference in numbers of Treg compared with control mice. Three weeks of OVA challenges resulted in suppression of AHR and greater numbers of airway Treg cells and increased transforming growth factor-beta(1) (TGFbeta(1)) compared with control mice despite the presence of increased eosinophilia, OVA-specific IgE and IgG(1), and airway remodeling. Six weeks of OVA challenges restored AHR, whereas airway Treg numbers, TGFbeta(1), BAL eosinophilia, and Th2 cytokines returned to control levels. Partial in vivo depletion or adoptive transfer of Treg cells restored or inhibited AHR, respectively, but did not affect TGFbeta(1) or Th2 cytokine production. In conclusion, AHR suppression is mediated by airway Treg cells and potentially via a paracrine induction of TGFbeta(1) in the airways.

CD30 supports lung inflammation

The physiological functions of CD30 have not been fully elucidated. Here we show that in CD30-deficient mice (CD30(-/-)), lung inflammation is significantly diminished in the ovalbumin (OVA) model of airway hyperreactivity. In CD30(-/-) mice, the recruitment of eosinophils into the airways after OVA-aerosol challenge of OVA-primed mice was significantly diminished when compared with wild-type (w.t.) mice. IL-13 levels were also significantly reduced in CD30(-/-) mice while levels of IFN-gamma, IL-4, IL-5 and IgE in bronchoalveolar lavage fluid, lung tissue and serum were comparable to w.t. mice. Peribronchial lymph node cells from CD30(-/-) mice, re-stimulated in vitro with OVA, secreted significantly lower levels of IL-13 than those from w.t. mice, but showed normal proliferative response and other cytokine production. Exogenous IL-13 reconstituted airway recruitment of leukocytes in OVA-challenged CD3O(-/-) mice. Adoptive transfer to naive w.t. mice of in vitro OVA-re-stimulated spleen cells from CD30(-/-) mice failed to induce eosinophilic pulmonary inflammation in contrast to transfer of primed cells from w.t. mice. These results indicate that CD30 is a regulator of T(h)2 responses in the effector-memory phase and a regulator of IL-13 production in memory cells in the lung.

Controversy surrounding the increased expression of TGF beta 1 in asthma

Asthma is a waxing and waning disease that leads to structural changes in the airways, such as subepithelial fibrosis, increased mass of airway smooth muscle and epithelial metaplasia. Such a remodeling of the airways futher amplifies asthma symptoms, but its etiology is unknown. Transforming growth factor β1 is a pleiotropic cytokine involved in many fibrotic, oncologic and immunologic diseases and is believed to play an essential role in airway remodeling that occurs in asthmatic patients. Since it is secreted in an inactive form, the overall activity of this cytokine is not exclusively determined by its level of expression, but also by extensive and complex post-translational mechanisms, which are all importanin modulating the magnitude of the TGFβ1 response. Even if TGFβ1 upregulation in asthma is considered as a dogma by certain investigators in the field, the overall picture of the published litterature is not that clear and the cellular origin of this cytokine in the airways of asthmatics is still a contemporaneous debate. On the other hand, it is becoming clear that TGFβ1 signaling is increased in the lungs of asthmatics, which testifies the increased activity of this cytokine in asthma pathogenesis. The current work is an impartial and exhaustive compilation of the reported papers regarding the expression of TGFβ1 in human asthmatics. For the sake of comparison, several studies performed in animal models of the disease are also included. Inconsistencies observed in human studies are discussed and conclusions as well as trends from the current state of the litterature on the matter are proposed. Finally, the different points of regulation that can affect the amplitude of the TGFβ1 response are briefly revised and the possibility that TGFβ1 is disregulated at another level in asthma, rather than simply in its expression, is highlighted.

The role of TGF-β in mice infected with Heligmosomoides polygyrus

Hyporesponsiveness induced by Heligmosomoides polygyrus was quantified and the relationship between TGF-beta and inflammation was identified in BALB/c mice. The immune response and pathological changes modified by neutralization of TGF-beta were characterized in vivo. Nine and twelve days following infection, BALB/c mice were injected intraperitoneally with anti-TGF-beta (1,2,3) antibodies, isotype control antibodies or isosmotic solution. We assessed both Th1 and Th2 related cytokines production ex vivo and in vitro, IgA, the number of CD4+ cells, and eosinophils in the lamina propria and the villus : crypt ratio in the small intestine 6 weeks after infection. The pattern of cytokine production differed in the intestine, peritoneal fluid and serum. In mice infected with H. polygyrus the concentrations of IL-5, IL-12, TNF-alpha and IL-10 were raised in the intestine, but in serum the level of cytokines was diminished below the value observed in uninfected mice. The neutralization of TGF-beta converted the pattern of immune response induced by H. polygyrus. The elevation of cytokines in serum coincided with the reduction of cytokine concentration in the intestine or peritoneum. Neutralization of TGF-beta restored infiltration of eosinophils into the lamina propria of the intestine despite the low level of IL-5. We conclude that H. polygyrus infection suppresses the immune response through pathways involving TGF-beta production or activity and that the Th2 related immune response was not affected by neutralization.

Mechanisms of immune suppression by interleukin-10 and transforming growth factor-beta: the role of T regulatory cells

Specific immune suppression and induction of tolerance are essential processes in the regulation and circumvention of immune defence. The balance between allergen-specific type 1 regulatory (Tr1) cells and T helper (Th) 2 cells appears to be decisive in the development of allergy. Tr1 cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals. In contrast, there is a high frequency of allergen-specific interleukin-4 (IL-4)-secreting T cells in allergic individuals. Allergen-specific immunotherapy can induce specific Tr1 cells that abolish allergen-induced proliferation of Th1 and Th2 cells, as well as their cytokine production. Tr1 cells utilize multiple suppressor mechanisms, such as IL-10 and transforming growth factor-beta (TGF-beta) as secreted cytokines and various surface molecules, such as cytotoxic T-lymphocyte antigen 4 and programmed death-1. IL-10 only inhibits T cells stimulated by low numbers of triggered T-cell receptors, which depend on CD28 costimulation. IL-10 inhibits CD28 tyrosine phosphorylation, preventing the binding of phosphatidylinositol 3-kinase p85 and consequently inhibiting the CD28 signalling pathway. In addition, IL-10 and TGF-beta secreted by Tr1 cells skew the antibody production from immunoglobulin E (IgE) towards the non-inflammatory isotypes IgG4 and IgA, respectively. Induction of antigen-specific Tr1 cells can thus re-direct an inappropriate immune response against allergens or auto-antigens using a broad range of suppressor mechanisms.

Advances in allergen-specific immunotherapy

Atopic disease affects approximately 30% of the population in western society. Allergen-specific immunotherapy (SIT) is the only treatment with a long-term effect available at the present time, and has been used successfully in the treatment of a number of allergies for almost 100 years. Despite this success, there is great demand for safer, faster and more effective approaches. At present, many studies are being conducted aiming to comply with this demand. The approaches used include conventional immunotherapy, using allergen extracts, as well as novel methods such as peptide immunotherapy, allergen DNA vaccines and non-injection routes of SIT. The clinical success of various treatments, new technical developments and a better understanding of the immunological mechanisms behind immunotherapy hold great potential for the broad application of allergen-SIT in the foreseeable future.

Inhalation Tolerance Is Induced Selectively in Thoracic Lymph Nodes but Executed Pervasively at Distant Mucosal and Nonmucosal Tissues

Under immunogenic conditions, both the site of initial Ag exposure and consequent T cell priming in specific draining lymph nodes (LNs) imprint the ensuing immune response with lasting tissue-selective tropism. With respect to immune tolerance, whether the site of tolerance induction leads to compartmentalized or, alternatively, pervasive tolerance has not been formally investigated. Using a murine model of inhalation tolerance, we investigated whether the induction of respiratory mucosal tolerance precludes the development of de novo Th2 sensitization upon subsequent exposure to the same Ag at distant mucosal (gut) and nonmucosal (cutaneous) sites. By tracking the proliferation of CFSE-labeled OVA-TCR transgenic CD4(+) T cells upon OVA inhalation in vivo, we defined the site of tolerance induction to be restricted to the thoracic LNs. Expectedly, inhalation tolerance prevented de novo Th2 sensitization upon subsequent exposure to the same Ag at the same site. Importantly, although gut- and skin-draining LNs were not used during tolerance induction, de novo Ag-specific proliferation and Th2 differentiation in these LNs, as well as memory/effector Th2 responses in the gut (allergic diarrhea) and skin (late-phase cutaneous responses) were inhibited upon immunogenic challenge to the same Ag. Interestingly, this pervasive tolerogenic phenotype was not associated with the presence of suppressive activity throughout the lymphatics; indeed, potent suppressive activity was detected solely in the spleen. These data indicate that while inhalation tolerance is selectively induced in local thoracic LNs, its tolerogenic activity resides systemically and leads to pervasive immune tolerance in distant mucosal and nonmucosal sites.

T regulatory cells and allergy

Anergy, tolerance and active suppression may not be independent events, but rather involve similar mechanisms and cell types in immune regulation. Induction of allergen-specific T(Reg) cells seems essential for maintaining a healthy immune response towards allergens. By utilizing multiple secreted cytokines and surface molecules, antigen-specific T(Reg) cells may re-direct an inappropriate immune response against allergens or auto-antigens.

Marked alveolar apoptosis/proliferation imbalance in end-stage emphysema

BACKGROUND

Apoptosis has recently been proposed to contribute to the pathogenesis of emphysema.

METHODS

In order to establish if cell fate plays a role even in end-stage disease we studied 16 lungs (9 smoking-associated and 7 alpha1antitrypsin (AAT)-deficiency emphysema) from patients who had undergone lung transplantations. Six unused donor lungs served as controls. Apoptosis was evaluated by TUNEL analysis, single-stranded DNA laddering, electron microscopy and cell proliferation by an immunohistochemical method (MIB1). The role of the transforming growth factor (TGF)-beta1 pathway was also investigated and correlated with epithelial cell turnover and with the severity of inflammatory cell infiltrate.

RESULTS

The apoptotic index (AI) was significantly higher in emphysematous lungs compared to the control group (p < or = 0.01), particularly if only lungs with AAT-deficiency emphysema were considered (p < or = 0.01 vs p = 0.09). The proliferation index was similar in patients and controls (1.9 +/- 2.2 vs 1.7 +/- 1.1). An increased number of T lymphocytes was observed in AAT-deficiency lungs than smoking-related cases (p < or = 0.05). TGF-beta1 expression in the alveolar wall was higher in patients with smoking-associated emphysema than in cases with AAT-deficiency emphysema (p < or = 0.05). A positive correlation between TGF-betaRII and AI was observed only in the control group (p < or = 0.005, r2 = 0.8). A negative correlation was found between the TGF-beta pathway (particularly TGF-betaRII) and T lymphocytes infiltrate in smoking-related cases (p < or = 0.05, r2 = 0.99)

CONCLUSION

Our findings suggest that apoptosis of alveolar epithelial cells plays an important role even in end-stage emphysema particularly in AAT-deficiency disease. The TGFbeta-1 pathway does not seem to directly influence epithelial turnover in end-stage disease. Inflammatory cytokine different from TGF-beta1 may differently orchestrate cell fate in AAT and smoking-related emphysema types.

Genes of tolerance

Activation-induced cell death, anergy and/or immune response modulation by T-regulatory cells (T(Reg)) are essential mechanisms of peripheral T-cell tolerance. There is growing evidence that anergy, tolerance and active suppression are not entirely distinct, but rather, represent linked mechanisms possibly involving the same cells and multiple suppressor mechanisms. Skewing of allergen-specific effector T cells to T(Reg) cells appears as a crucial event in the control of healthy immune response to allergens and successful allergen-specific immunotherapy. The T(Reg) cell response is characterized by abolished allergen-induced specific T-cell proliferation and suppressed T helper 1 (Th1)- and Th2-type cytokine secretion. In addition, mediators of allergic inflammation that trigger cAMP-associated G-protein coupled receptors, such as histamine receptor 2 may contribute to peripheral tolerance mechanisms. The increased levels of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) that are produced by T(Reg) cells potently suppress immunoglobulin E (IgE) production, while simultaneously increasing production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation such as mast cells, basophils and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms. It is associated with regulation of antibody isotypes and effector cells to the direction of a healthy immune response and opens a window for novel therapies of allergic diseases.

Asthma: mechanisms of disease persistence and progression

When asthma is diagnosed, eosinophilic inflammation and airway remodeling are established in the bronchial airways and can no longer be separated as cause and effect because both processes contribute to persistence and progression of disease, despite anti-inflammatory therapy. Th2 cells are continually active in the airways, even when disease is quiescent. IL-13 is the key effector cytokine in asthma and stimulates airway fibrosis through the action of matrix metalloproteinases on TGF-beta and promotes epithelial damage, mucus production, and eosinophilia. The production of IL-13 and other Th2 cytokines by non-T cells augments the inflammatory response. Inflammation is amplified by local responses of the epithelium, smooth muscle, and fibroblasts through the production of chemokines, cytokines, and proteases. Injured cells produce adenosine that enhances IL-13 production. We review human and animal data detailing the cellular and molecular interactions in established allergic asthma that promote persistent disease, amplify inflammation, and, in turn, cause disease progression.

Smads as intracellular mediators of airway inflammation

Transforming growth factor-beta (TGF-beta) plays an important role in the pathogenesis of allergic asthma and other airway diseases. Signals from the activated TGF-beta receptor complex are transduced to the nucleus of airway cells by Smad proteins, which represent a family of transcription factors that have recently been implicated to play a major role as intracellular mediators of inflammation. The Smad family consists of the receptor-regulated Smads, a common pathway Smad, and inhibitory Smads. Receptor-regulated Smads (R-Smads) are phosphorylated by the TGF-beta type Ireceptor. They include Smad2 and Smad3, which are recognized by TGF-beta and activin receptors, and Smads 1, 5, 8, and 9, which are recognized by bone morphogenetic protein (BMP) receptors. Smad4 is a common pathway Smad, which is also defined as cooperating Smad (co-Smad) and is not phosphorylated by the TGF-beta type I receptor. Inhibitory Smads(anti-Smads) include Smad6 and Smad7, which down-regulate TGF-beta signaling. To date, the Smads are the only TGF-beta receptor substrates with a demonstrated ability to propagate signals and with regard to the growing number of investigations of Smad-mediated effects in the airways, Smads may prove to be an important target for future development of new therapeutic strategies for asthma and chronic obstructive pulmonary disease.

Immunomodulatory cytokines in asthmatic inflammation

The development of asthmatic inflammation involves a complex array of cytokines that promote the recruitment and activation of a number of different immune cells. While factors involved in initiating and establishing inflammation are well characterized, the process by which this pro-inflammatory cascade is regulated is less well understood. The identification and characterization of immunomodulatory cytokines in asthma has been a difficult proposition. Many of the putative regulatory factors have pleiotropic bioactivities and have been characterized as pro-inflammatory in association with certain pathologic conditions. This chapter addresses the potential role of several endogenous factors which appear to attenuate asthmatic inflammation. Understanding the integration of these factors into the regulation of the inflammatory process will likely result in novel therapeutic approaches.

Characterization of a neuraminidase-deficient influenza a virus as a potential gene delivery vector and a live vaccine

We recently identified a packaging signal in the neuraminidase (NA) viral RNA (vRNA) segment of an influenza A virus, allowing us to produce a mutant virus [GFP(NA)-Flu] that lacks most of the NA open reading frame but contains instead the gene encoding green fluorescent protein (GFP). To exploit the expanding knowledge of vRNA packaging signals to establish influenza virus vectors for the expression of foreign genes, we studied the replicative properties of this virus in cell culture and mice. Compared to wild-type virus, GFP(NA)-Flu was highly attenuated in normal cultured cells but was able to grow to a titer of >10(6) PFU/ml in a mutant cell line expressing reduced levels of sialic acid on the cell surface. GFP expression from this virus was stable even after five passages in the latter cells. In intranasally infected mice, GFP was detected in the epithelial cells of nasal mucosa, bronchioles, and alveoli for up to 4 days postinfection. We attribute the attenuated growth of GFP(NA)-Flu to virion aggregation at the surface of bronchiolar epithelia. In studies to test the potential of this mutant as a live attenuated influenza vaccine, all mice vaccinated with >/==" BORDER="0">10(5) PFU of GFP(NA)-Flu survived when challenged with lethal doses of the parent virus. These results suggest that influenza virus could be a useful vector for expressing foreign genes and that a sialidase-deficient virus may offer an alternative to the live influenza vaccines recently approved for human use.

Chronic inhaled ovalbumin exposure induces antigen-dependent but not antigen-specific inhalational tolerance in a murine model of allergic airway disease

Sensitized mice acutely challenged with inhaled ovalbumin (OVA) develop allergic airway inflammation, characterized by OVA-specific IgE production, airway eosinophilia, increased pulmonary B and T lymphocytes, and airway hyperreactivity. In this study, a chronic exposure model was developed and two distinct patterns of response were observed. Discontinuous inhalational exposure to OVA (6 weeks) produced airway inflammation and hyperreactivity that were similar to acute (10 days) responses. Continuous inhalational exposure to OVA (6 or 11 weeks) resulted in attenuation of airway eosinophilia and hyperresponsiveness without reduction of OVA-specific IgE and IgG(1) levels. The inhibition of airway inflammation was dependent on continuous exposure to antigen, because continuously exposed mice with attenuated inflammatory responses redeveloped allergic airway disease if the OVA aerosols were interrupted and then restarted (11-week-discontinuous). Inhalational tolerance induced by continuous OVA exposure demonstrated bystander suppression of cockroach allergen-mediated airway eosinophilia. These findings may be attributed to changes in production of the anti-inflammatory cytokine interleukin-10 during continuous OVA aerosol exposure. The symptomatic and asymptomatic allergic responses in human asthmatics could be explained by similar variable or discontinuous exposures to aeroantigens.

Airway inflammation in childhood asthma

Airway pathology has been extensively investigated in adulthood asthma, whereas only few studies examined bronchial biopsies in childhood asthma. To evaluate the airway pathology in children with asthma, we analyzed bronchial biopsies obtained from 23 children undergoing bronchoscopy for clinical indications other than asthma. Nine had mild/moderate asthma. Six had atopy without asthma, and eight had no atopy or asthma. We measured basement membrane thickness and quantified the number of eosinophils, mast cells, neutrophils, macrophages, T lymphocytes, and positive cells for transforming growth factor-beta1 (TGF-beta1) and its receptors I and II (TGFbeta-RI and TGFbeta-RII) in subepithelium. Children with asthma had an increase in basement membrane thickness and in the number of eosinophils compared with control subjects, but not compared with children with atopy. They also had a decreased expression of TGFbeta-RII compared with both those with atopy and control subjects. In children with asthma, the number of eosinophils correlated negatively with TGFbeta-RII and positively with symptom duration. In conclusion, airway eosinophilia and basement membrane thickening, which are the pathologic features that are characteristic of adulthood asthma, are already present in children with mild asthma, and even in children with atopy without asthma. Moreover, in children with asthma but not in children with atopy without asthma, there is a downregulation of TGFbeta-RII.

Impact of intranasal budesonide on immune inflammatory responses and epithelial remodeling in chronic upper airway inflammation

BACKGROUND

Histologic and immunohistologic features of nasal polyps (NP) are similar to those observed in asthma, thus suggesting a similar immunopathology.

OBJECTIVE

The primary objective of this study was to further understand the anti-inflammatory and immunoregulatory effects of locally delivered corticosteroids. To this end, the effect of intranasal budesonide on the expression of specific cytokines, lymphocyte subsets, and epithelial remodeling in this model of airway tissue inflammation were studied.

METHODS

We used immunohistochemical techniques to examine nasal mucosae (NM) from healthy individuals and nasal polyp (NP) tissues from patients with nasal polyposis obtained before and after intranasal budesonide treatment.

RESULTS

First, the density of CD8(+) cells was markedly increased in NP tissues after intranasal budesonide treatment from 16.1 +/- 8.4 (M +/- SEM) per mm(2) to 39.9 +/- 24.1. Second, the density of cells immunoreactive for IL-4, IL-5, IFN-gamma, IL-12, and TGF-beta in NP was significantly greater than in control NM tissues. The density of IL-4(+) and IL-5(+) cells in NP tissues significantly decreased after budesonide treatment from 40 +/- 12 to 17.8 +/- 8 and from 19.3 +/- 11 to 10.4 +/- 7, respectively. In contrast, the density of IFN-gamma(+) and IL-12(+) cells remained unchanged. In addition, we found that the density of TGF-beta(+) cells significantly increased after intranasal budesonide from 18 +/- 5 to 41 +/- 9. Third, damage to the entire length of the NP epithelium was quantified using a grading system. The epithelium of untreated NP was substantially damaged; remarkable epithelial restitution with no apparent changes in stromal collagen deposition was observed after intranasal budesonide treatment.

CONCLUSIONS

These findings demonstrate that intranasal budesonide induced an increase in CD8 population and a selective regulatory effect on tissue cytokine expression. Furthermore, intranasal budesonide promoted epithelial remodeling. We hypothesize that these immunoregulatory and remodeling effects elicited by steroids might be, at least in part, mediated by the induction of TGF-beta.

Mast cells play a partial role in allergen-induced subepithelial fibrosis in a murine model of allergic asthma

BACKGROUND

Role of mast cells in the development of allergen-induced airway remodelling has not been fully investigated in vivo.

OBJECTIVE

To clarify the possible role of mast cells in the development of allergen-induced airway remodelling, we compared their responses of genetically mast cell-deficient mice, WBB6F1-W/Wv (c-kit mutant) and Sl/Sld (c-kit ligand mutant) mice with those of congenic normal mice in a murine model of allergic asthma.

METHODS

Mice were sensitized to ovalbumin (OA) with alum, and exposed daily for 3 weeks to aerosolized OA. Twenty-four hours after the last inhalation, bronchial responsiveness to acetylcholine (Ach) was measured, and bronchoalveolar lavage (BAL), and biochemical and histological examinations were performed.

RESULTS

In both sensitized mast cell-deficient mice, the degree of bronchial hyper-responsiveness to Ach, the number of inflammatory cells and the level of transforming growth factor-beta1 in BAL fluid, IgE response and goblet cell hyperplasia in the epithelium after repeated allergen provocation were not significantly different from those of congenic mice. In contrast, subepithelial fibrosis, evaluated in the fibrotic area around the airways, observed in congenic mice after repeated allergen challenge was partially attenuated in both mast cell-deficient mice. In addition, the amount of hydroxyproline in the lung of mast cell-deficient mice was significantly lower than that of congenic mice. Furthermore, the decreased fibrotic area and amount of hydroxyproline in W/Wv mice was completely recovered by reconstitution of tissue mast cells with bone marrow-derived mast cells of congenic mice.

CONCLUSION

These findings suggest that mast cells play a partial role in the development of allergen-induced subepithelial fibrosis, although airway inflammation, epithelial remodelling and BHR caused by repeated allergen challenge are independent of mast cells, at least in this model.

Suppression of allergen reactive Th2 mediated responses and pulmonary eosinophilia by intranasal administration of an immunodominant peptide is linked to IL-10 production

The potential to induce systemic tolerance following exposure of the airway mucosa to soluble antigen, may be applied therapeutically for the treatment of allergic disease. Since the use of allergen can trigger IgE mediated inflammation, we investigated whether mucosal delivery of a peptide, containing an immunodominant epitope of the Der p1 allergen of house dust mite, can lead to CD4(+) Th2 cell tolerance and thus protect against airway inflammatory responses to inhalant allergen. The administration of microencapsulated peptide to the nasal mucosa of mice, protected against airway inflammation, with significant reductions in eosinophil infiltration into the airways following allergen challenge. Der p1 specific antibody levels in sera were not modulated. Allergen reactive CD4(+) T cells expressed a tolerized phenotype, with reduction in levels of the cytokines, IL-5, IL-13 and IFN-gamma although IL-10 levels were increased. The mucosal administration of a peptide containing an immunodominant region of an allergen can protect against the induction of systemic and local inflammatory responses to allergen challenge.

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.

Novel vaccines protecting against the development of allergic disorders: a double-edged sword?

The severity and incidence of allergic disorders is steadily increasing despite the widespread use of steroids and other drugs. Recent results obtained in animals suggest that it may be possible to develop novel anti-allergy vaccines for human use, thereby stopping this alarming worldwide increase in allergic diseases. The most promising approaches are the induction of allergen-specific T helper 1 or allergen-specific T regulatory responses. However, both approaches potentially harbour negative side effects that need to be ruled out before vaccinating young children -- the best candidates for the primary prevention of allergic disorders.

Mucosal tolerance as therapy of type I allergy: intranasal application of recombinant Bet v 1, the major birch pollen allergen, leads to the suppression of allergic immune responses and airway inflammation in sensitized mice

BACKGROUND

Several studies have demonstrated that mucosal administration of soluble antigens can prevent the onset or reduce the severity of certain autoimmune diseases or allergies. Few studies exist showing the efficacy of mucosal tolerance for therapy of such diseases.

OBJECTIVE

The aim of the present study was to modulate an allergic immune response by intranasal antigen administration in an already sensitized organism.

METHODS

A murine model of allergic asthma to birch pollen (BP) and its major allergen Bet v 1 was utilized. Sensitized mice were intranasally treated with recombinant (r)Bet v 1 in different concentrations and at different intervals. On the day the mice were killed, blood and bronchoalveolar lavage fluids were taken and immediate type I skin tests were performed. T cell proliferation and cytokine production (interleukin (IL)-5, interferon (IFN)-gamma) were measured in spleen and lung cell cultures.

RESULTS

Mucosal treatment with rBet v 1 (3 x 50 microg in 4 day intervals) led to a reduction of type I skin reactions, suppressed immunoglobulin (Ig)G1/IgE antibody levels and markedly decreased IL-5 and IFN-gamma production in vitro in spleen and lung cell cultures. Moreover, lung inflammation (i.e. eosinophilia and IL-5 levels in bronchoalveolar lavage fluids) was significantly suppressed by the treatment.

CONCLUSION

Our results demonstrate that intranasal treatment with rBet v 1 reduced systemic allergic immune responses as well as airway inflammation in BP-sensitized mice. We therefore suggest that mucosal tolerance induction with recombinant allergens could be a promising concept for the therapy of allergic diseases.

The influence of diesel exhaust particles on mononuclear phagocytic cell-derived cytokines: IL-10, TGF-beta and IL-1 beta

Diesel exhaust particles (DEP) are known to modulate the production of cytokines associated with acute and chronic respiratory symptoms and allergic respiratory disease. Tolerance is an important mechanism through which the immune system can maintain nonresponsiveness to common environmental antigens. We examined the effect of DEP on IL-10 and TGF-beta, cytokines produced by macrophages and repressor (Tr-like) lymphocytes which influence tolerance. Human PBMCs (n = 22) were incubated with 1-100 ng/ml of DEP, and suboptimally primed with LPS. IL-10 gene expression was assessed by the S1 nuclease protection assay, and production of IL-10, TGF-beta, TNF-alpha, IL-1 beta and IL-4 stimulated CD23 was evaluated by ELISA after 24 and 48 h. The effect of the order of exposure to DEP and LPS was evaluated on IL-10 protein and mRNA in cells (1) preincubated with LPS followed by DEP, or (2) exposed first to DEP followed by LPS. IL-10 was further evaluated using benzo[a]pyrene and [alpha]naphthoflavone as a surrogate for the polyaromatic hydrocarbons (PAHs) adsorbed to DEP. Control cells were incubated with carbon black, without PAHs. In PBMCs exposed to DEP with LPS, or preincubated with LPS before DEP, IL-10 production and mRNA fall significantly. TGF-beta is similarly suppressed, IL-1 beta secretion is significantly stimulated, and IL-4 stimulated CD23 release rises in the atopic subjects. In contrast, when DEP is added prior to LPS, IL-10 production rises, and IL-1 beta falls to zero. These effects on IL-10 are reproduced with benzo[a]pyrene and reversed by the coaddition of [alpha]naphthoflavone, its known antagonist. The carbon black fraction has no effect on IL-10 production. The effect of DEP on IL-10 can be inhibitory or stimulatory, depending on the order of exposure to DEP and LPS. Pro-inflammatory cytokines and factors rise when IL-10 is inhibited, and are suppressed when IL-10 is stimulated. These results are duplicated with benzo[a]pyrene, suggesting that the PAH portion of the DEP is the active agent.

Atopic disorders: a vaccine around the corner?

The incidence and severity of atopic disorders, in particular asthma, is steadily increasing at an alarming rate. Furthermore, no primary prevention measure exists to date. However, recent results obtained from numerous animal studies suggest that primary prevention in humans might be possible in the near future. The most promising approaches include the induction of systemic or local allergen-dependent or -independent T helper 1 (Th1) immune responses, through the use of killed bacteria (or components derived from them), CpG oligodeoxynucleotides or plasmid DNA, and the induction of allergen-specific T-cell tolerance. Here, we review the data showing that animals can be protected from developing allergic Th2 responses by vaccination. Possible future use in humans and potential side-effects of the described vaccination strategies are discussed also.

TGF-beta-producing CD4+ mediastinal lymph node cells obtained from mice tracheally tolerized to ovalbumin (OVA) suppress both Th1- and Th2-induced cutaneous inflammatory responses to OVA by different mechanisms

Advances in the treatment of allergic disorders require elucidation of the autoregulatory immune systems induced in averting detrimental inflammatory responses against invading foreign Ags. We previously reported that excessive Ags intruding through the airway mucosa induce a subset of regulatory CD4+ T cells secreting TGF-beta in the regional mediastinal lymph nodes (MLNs), which inhibits Th2 cells and subsequent eosinophilic inflammation in the trachea. In the present experiments we examined whether and in what mechanisms TGF-beta-secreting CD4+ T cells in the MLNs regulate Th cell-mediated skin inflammation using a previously established murine model. Th1 or Th2 cells injected s.c. into ear lobes of naive mice induced swelling, whereas the concomitant local injection of MLN cells suppressed the inflammation. The suppressor activities of MLN cells were markedly neutralized by anti-TGF-beta mAb and were mimicked by rTGF-beta. The MLN cell- and rTGF-beta-induced inhibition was reversed by anti-IL-10 mAb significantly in Th1-induced inflammation and only partially in Th2-induced inflammation. rIL-10 reduced Th-induced ear swelling, although higher doses of rIL-10 were required in Th2-induced one. Thus, allergen-specific TGF-beta-producing CD4+ T cells induced in the respiratory tract controlled cutaneous inflammatory responses by Th1 or Th2 cells either directly by TGF-beta or indirectly through IL-10 induction. From a clinical standpoint, these observations might explain the mechanism of spontaneous regression in some patients with atopic dermatitis, which exhibits both Th1- and Th2-mediated skin inflammation in response to airborne protein Ags.

Heterogeneity of pulmonary fibrosis: interstitial pneumonias and sarcoidosis

This review focuses on two representatives of pulmonary fibrosis. One is usual interstitial pneumonia lesion, typically seen in patients with idiopathic pulmonary fibrosis. The other is parenchymal fibrosis along the bronchovascular bundles, observed in patients with sarcoidosis. Both are intractable fibrosis amenable only to lung transplantation. The authors trace the historical classification of idiopathic interstitial pneumonia, discuss interstitial pneumonia associated with collagen vascular diseases and occupational exposure, and review the most important issues to clarify both types of pulmonary fibrosis.

Novel roles of CpG oligodeoxynucleotides as a leader for the sampling and presentation of CpG-tagged antigen by dendritic cells

Oligodeoxynucleotides containing CpG motifs have been highlighted as potent Th1 activators. We previously reported that Ag and CpG, when conjugated together, synergistically promoted the Ag-specific Th1 development and inhibited the Th2-mediated airway eosinophilia. In this study, we examined the mechanisms underlying the synergism of the covalent conjugation. The CpG-OVA conjugate enhanced the Th1 activation and development. These characteristic features of the conjugate could not be ascribed to the polymerization of OVA, but mirrored the augmented binding of the CpG-tagged Ag to dendritic cells (DCs) in a CpG-guided manner, because phycobiliprotein, R-PE, conjugated to CpG stained a higher proportion of DCs with higher intensity than the mixture. R-PE fluorescence was emitted from cytoplasmic portions of the DCs, which simultaneously expressed costimulatory molecules and IL-12. The CpG-conjugated R-PE trafficking described above actually served as a potent Ag. These results indicate that CpG conjugated to Ag exhibit novel joint properties as promoters of Ag uptake and DC activators, thereby potentiating the ability of DCs to generate Th1 cells. The DNA-mediated promotion of Ag uptake would be advantageous for evoking host immune responses against invading microorganisms.

Is TGF-beta1 the key to suppression of human asthma?

Transforming growth factor beta1 (TGF-beta1) is produced by many types of cells that are activated in the asthmatic response. Recent studies have highlighted this cytokine as an important negative regulator in an experimental model of asthma. Although the role of TGF-beta1 in human asthma remains obscure, data derived from animal models have encouraged the further investigation of such suppression mechanisms in order to develop novel therapies for asthma.

Regulation of murine airway eosinophilia and Th2 cells by antigen-conjugated CpG oligodeoxynucleotides as a novel antigen-specific immunomodulator

The characteristic features of bronchial asthma reflect the orchestrated activity of Th2 cells. Oligodeoxynucleotides containing CpG motifs (CpG) have recently been highlighted as an immunomodulator that biases toward a Th1-dominant phenotype. We have previously reported that intratracheal coadministration of CpG and allergen inhibited airway eosinophilia and hyperresponsiveness in a synergistic manner. To substantiate the synergism between CpG and Ag, we introduced a covalently linked conjugate between CpG and Ag and examined the efficacy on airway eosinophilia and Th2 cytokine production. We found that the conjugated form of CpG plus Ag was 100-fold more efficient in regulating airway eosinophilia than the unconjugated mixture. The inhibitory effects lasted for at least 2 mo. The inhibition of airway eosinophilia by the conjugate was Ag specific and associated with an improvement of the airway hyperresponsiveness and the unresponsiveness of the Ag-specific Th2 cells in the regional lymph nodes. The CpG-Ag conjugate was 100-fold more effective than the unconjugated mixture for inducing in vitro Th1 differentiation in an IL-12-dependent manner. Our data show that CpG conjugated to Ag can work as a novel Ag-specific immunomodulator and imply that inhalation of allergen-CpG conjugate could be a desensitization therapy for patients with bronchial asthma.

Regulation of T-helper type 2 cell and airway eosinophilia by transmucosal coadministration of antigen and oligodeoxynucleotides containing CpG motifs

The characteristic features of bronchial asthma, including airway eosinophilia and elevated immunoglobulin (Ig)E levels, are known to be orchestrated by T-helper (Th) 2 cells. Oligodeoxynucleotides containing CpG motifs (CpG) have recently been highlighted as an immunomodulator that biases toward a Th1-dominant phenotype. However, CpG may incur nonspecific Th1 activation and toxic effects. In this study we report a novel inhibition of Th2 cells by transmucosal inoculation of antigen and CpG. Intratracheal instillation of CpG inhibited airway eosinophilia and Th2 cytokine production in antigen-sensitized mice. The inhibition was observed when CpG was given at the same time or in advance of antigen challenge. Notably, concomitant administration of CpG and antigen (as opposed to either one alone) was essential for the inhibitory effects. The antigen dose could be minimized to avoid a harmful boost of eosinophilia. CpG had few effects on systemic anti-ovalbumin IgE responses. These results demonstrate that a synergism between transmucosally administered allergen and CpG inhibits Th2 cells in parallel with an improvement in airway eosinophilia and hyperresponsiveness without impeding systemic immune responses. Our data imply that inhalation of a minimal amount of allergen plus CpG could be a novel desensitization therapy for patients with bronchial asthma.