Allergic Airway Research Articles

LIPOPOLYSACCHARIDE STIMULATION OF DENDRITIC CELLS INDUCES INTERLEUKIN-10 PRODUCING ALLERGEN-SPECIFIC T CELLS IN VITRO BUT FAILS TO PREVENT ALLERGIC AIRWAY DISEASE

Dendritic cells (DCs) play an important role in directing naive T cells towards a Th1/Th2 or regulatory T cells (Treg) cell phenotype. In this context, interleukin (IL)-10 has been shown to exhibit immune regulatory capacities. The aim of this study was to delineate the influence of high-IL-10–producing DCs on DC–T-cell interactions in inhibiting allergen-induced airway inflammation and hyperreactivity in a murine model of allergic airway disease. Bone marrow–derived dendritic cells (BMDCs) were generated from hemopoietic progenitors by culture with granulocte-macrophage colony-stimulating factor (GM-CSF), and stimulated with ovalbumin (OVA) ± lipopolysaccharide (LPS). The effects of ovalbumin-pulsed BMDCs on cytokine production by allergen-specific naive T cells were studied in vitro. The development of airway inflammation in Balb/c mice was determined after intranasal administration of BMDCs in vivo. LPS stimulation of BMDCs strongly enhanced IL-10 production. Coculture of LPS-modulated DCs exhibiting increased IL-10 production with allergen-specific naive T cells reduced the production of interferon (IFN)-γ and IL-5, but enhanced the production of IL-10. After blockade with anti-IL-10 plus anti-IL-10-receptor antibodies, the level of IFN-γ and IL-5 production by cocultured T cells was restored, underlining the regulatory function of IL-10. Intranasal administration of high-IL-10–producing LPS-stimulated, OVA-primed BMDCs prior to repetitive airway allergen challenges resulted in an even enhanced airway inflammation. These data demonstrate that increased IL-10 production by DCs may be a critical element for T-cell activation and differentiation in the context of allergen-induced immune responses in vitro. However, this DC modulation did not translate into suppression of allergic airway disease in vivo.

CD11b+ Myeloid Cells Are the Key Mediators of Th2 Cell Homing into the Airway in Allergic Inflammation

STAT6-mediated chemokine production in the lung is required for Th2 lymphocyte and eosinophil homing into the airways in allergic pulmonary inflammation, and thus is a potential therapeutic target in asthma. However, the critical cellular source of STAT6-mediated chemokine production has not been defined. In this study, we demonstrate that STAT6 in bone marrow-derived myeloid cells was sufficient for the production of CCL17, CCL22, CCL11, and CCL24 and for Th2 lymphocyte and eosinophil recruitment into the allergic airway. In contrast, STAT6 in airway-lining cells did not mediate chemokine production or support cellular recruitment. Selective depletion of CD11b(+) myeloid cells in the lung identified these cells as the critical cellular source for the chemokines CCL17 and CCL22. These data reveal that CD11b(+) myeloid cells in the lung help orchestrate the adaptive immune response in asthma, in part, through the production of STAT6-inducible chemokines and the recruitment of Th2 lymphocytes into the airway.

The Involvement of Histaminic and Muscarinic Receptors in the Bronchoconstriction Induced by Myorelaxant Administration in Sensitized Rabbits

Muscle relaxants cause bronchospasm via histamine release and/or by acting on the muscarinic receptors; we sought to characterize the respective importance of these pathways in the presence of bronchial hyperreactivity. Ovalbumin-sensitized rabbits were randomly assigned to several protocol groups: Group C comprised untreated animals; in the other three groups, either H1 and H2 histaminic receptor blockade was performed, leaving the M1, M2, and M3 muscarinic receptors functional (Group M123), or combining this treatment with M3 muscarinic receptor blockade (Group M12), or with vagotomy (Group M3). Respiratory system impedance was measured over a 90-s period, during which succinylcholine, mivacurium or atracurium was administered. To monitor the changes in lung mechanics, respiratory system impedance was averaged in a 2-s time window and fitted by a model featuring airway resistance and inertance and tissue damping and elastance. The peak increases in airway resistance in Group C were greatest with succinylcholine (79 +/- 17[SE]%) and mivacurium administration (75% +/- 12%), whereas they were lower after attracurium (40% +/- 11%). These changes were markedly attenuated by both histamine and muscarinic receptor blockade with the largest reduction in Group M3 for succinylcholine (14% +/- 5.2%), and in Group M123 for mivacurium (5.1% +/- 9.1%) and attracurium (7.8% +/- 4.0%). Although the bronchospasm developing in the allergic airways after muscle relaxants is mediated primarily by the histaminic pathway, the interactions of succinylcholine on the M1, M2, and M3 receptors, those of atracurium on the M1 and M2 receptors, and those of mivacurium on the M3 receptors may also play a role.

The Effects of Heat-Killed Wild-Type Lactobacillus casei Shirota on Allergic Immune Responses in an Allergy Mouse Model

Background: Probiotics are used as a management strategy for allergic diseases, but their effects on allergic responses in sensitized allergic individuals remain unclear. This study explored the immunomodulatory effects of probiotics on allergen-specific allergic reactions in an allergy mouse model. Methods: C57BL/6 mice were presensitized by epicutaneous patching with recombinant Der p 2, and were subsequently administered orally with either heat-killed wild-type Lactobacillus casei or NaHCO₃ buffer for 5 weeks (n = 6 per group). All mice then received 2 subcutaneous immunizations of Der p 2 to mimic allergen immunotherapy, followed by aerosol challenge with Der p 2 a week later. Results: The Der p 2-sensitized mice fed L. casei showed significantly lower Der p 2-specific IgE and IgG1 after subcutaneous immunizations and airway challenge with Der p 2 compared to the control, unfed group. Splenic T cells of mice fed L. casei showed suppression of Th-2 (IL-5, IL-13, IL-10 and IL-4) and proinflammatory (TNF-α, IFN-γ) cytokines. Following airway allergen challenge, the mice fed L. casei showed histological evidence of attenuation of lung inflammation, as well as reductions in the total cell count and Th2 and proinflammatory cytokines in bronchoalveolar lavage fluid, compared to controls. Taken together, these results suggest that the oral administration of heat-killed L. casei could effectively downregulate the pre-existing Th-2 allergic responses and pulmonary inflammatory responses upon subcutaneous and airway allergen challenge. Conclusions:L. casei has intrinsic adjuvant and immunomodulatory properties that could potentially be exploited for secondary prevention or treatment of allergic respiratory diseases.

Advances in upper airway diseases and allergen immunotherapy in 2007

The purpose of this review is to highlight important articles on upper airway diseases and immunotherapy that appeared in 2007. Advances in rhinitis include the realization that allergic rhinitis might be caused by local nasal IgE sensitization to aeroallergens in the absence of systemic evidence of IgE sensitization. After inhalation, allergens might reach systemic circulation. Epidemiologic studies continue to show that allergic rhinitis impairs school performance and is a risk factor for future asthma. New pathways are being identified in chronic sinusitis, as well as in different types of allergic ocular diseases. New treatments for patients with allergic rhinitis include use of beta-1,3-glucan, a mushroom product that can reduce allergic symptoms by inducing T(H)1 response, and olopatadine nasal spray. Studies on immunotherapy in 2007 suggest that sublingual immunotherapy induces similar immunologic alterations as those induced by subcutaneous immunotherapy, although to a lesser degree. Among allergists in the United States, there is a sizable variation in clinical practice, particularly related to concomitant administration of immunotherapy and beta-blockers, to administration of angiotensin-converting enzyme inhibitors, and to patients with HIV or autoimmune diseases. The combination of omalizumab with allergen subcutaneous immunotherapy can enhance clinical efficacy. Recombinant technology can modify allergen structure to prevent binding to IgE (allergenicity) while enhancing immunogenicity (stimulation of T cells), which might improve the safety and efficacy of immunotherapy.

Cis-9, trans-11-Conjugated Linoleic Acid Inhibits Allergic Sensitization and Airway Inflammation via a PPAR γ-Related Mechanism in Mice 3

Milk consumption from early childhood on has been found to be inversely correlated with allergic sensitization and the onset of bronchial asthma. We tested whether cis-9, trans-11-conjugated linoleic acid (c9, t11-CLA), naturally occurring in milk fat, may prevent allergic sensitization and inhibit airway inflammation in a murine asthma model. BALB/c mice were fed a diet enriched in 1 wt% of c9, t11-CLA or a control diet 7 d prior to and for 32 d during sensitization [d 1 and 14, 100 mg/L ovalbumin (OVA) in adjuvant vs. PBS] and airway challenges (d 28–30, 1% OVA in PBS vs. PBS). Subgroups of mice were coadministered 20 μmol/L of the selective PPAR γ antagonist GW9662 during each OVA challenge. C9, t11-CLA feeding resulted in significantly reduced IgE production and allergen-induced in vivo airway hyperresponsiveness. Further, less mucous plugging of segmental bronchi and significantly reduced interleukin-5 and eosinophils were determined in bronchoalveolar lavage fluids of c9, t11-CLA-fed mice. C9, t11-CLA feeding prevented the downregulation of PPAR γ mRNA in the lung tissues observed after allergen sensitization and airway challenges in control mice. The inhibitory effects of c9, t11-CLA on airway inflammation were partially prevented by coadministration of GW9962. Further, c9, t11-CLA feeding resulted in a significantly lower concentration of the eicosanoid precursor, arachidonic acid, in tissue lipids. These findings demonstrate that dietary c9, t11-CLA can reduce allergic airway inflammation, most likely via a PPAR γ-related mechanism and by reducing eicosanoid precursors. They give new insights into the fatty acid-mediated mechanism of immunomodulation and may represent a step toward an attractive novel strategy in the dietary prevention and treatment of allergic asthma.

Mice Lacking 12/15-Lipoxygenase Have Attenuated Airway Allergic Inflammation and Remodeling

Arachidonate 15-lipoxygenase (LO)-1 has been implicated in allergic inflammation and asthma. The overall effect of 15-LO in allergic inflammation in vivo is, however, unclear. This study investigates systemic allergen sensitization and local allergic airway inflammation and remodeling in mice lacking the murine 12/15-LO, the ortholog to human 15-LO-1. Upon systemic sensitization with intraperitoneal ovalbumin, 12/15-LO-/- mice produced elevated levels of allergen-specific immunoglobulin E compared with wild-type (Wt) controls. However, when challenged with repeated aerosolized allergen, sensitized 12/15-LO-/- mice had an impaired development of airway allergic inflammation compared with Wt controls, as indicated by reduced bronchoalveolar lavage fluid leukocytes (eosinophils, lymphocytes, macrophages) and Th2 cytokines (IL-4, IL-5, IL-13), as well as tissue eosinophils. Allergen-induced airway epithelial proliferation was also significantly attenuated in 12/15-LO-/- mice, whereas goblet cell hyperplasia was unaffected. However, 12/15-LO-/- mice had significantly reduced luminal mucus secretions compared with Wt controls. The repeated allergen challenges resulted in a dramatic increase of alpha-smooth muscle actin-positive alveolar cells in the peripheral airways, a phenomenon that was significantly less developed in 12/15-LO-/- mice. In conclusion, our data suggest that 12/15-LO-/- mice, although having a fully developed systemic sensitization, did not establish a fully developed allergic airway inflammation and associated manifestations of central and peripheral airway remodeling. These data suggest that 12/15-LO-derived metabolites play an important pathophysiologic role in allergen-induced inflammation and remodeling. Hence, pharmacologic targeting of the human 15-LO-1 may represent an attractive therapeutic strategy to control inflammation and remodeling in asthma.

Lipopolysaccharides Modulate Allergen-Specific Immune Regulation in a Murine Model of Mucosal Tolerance Induction

Background: Farming has been widely reported to be associated with decreased risk of developing atopic disorders, but underlying immunomodulatory mechanisms are still not fully defined. We delineated T-cell functions after induction of mucosal tolerance in the context of intranasally delivered organic dust compounds, lipopolysaccharides (LPS). Methods: BALB/c mice were pretreated intranasally with ovalbumin (OVA) with or without LPS (Escherichia coli) three times (days –21, –14, –7) prior to systemic OVA sensitization (days 1 and 14) and airway allergen challenges (days 28–30). CD4+ spleen T cells from pretreated and sensitized donors were characterized for cytokine function, and transferred into naive recipients prior to subsequent OVA sensitization and challenges. Results: Intranasal OVA pretreatment suppressed Th2-mediated immune and inflammatory responses and enhanced frequency of regulatory T cells in OVA-sensitized and -challenged mice. Addition of LPS to OVA, but not LPS alone, inhibited development of allergen-induced sensitization and eosinophilic airway infiltration, and markedly enhanced allergen-specific IgG1 serum levels and frequencies of IL-10- and IFN-γ-producing CD4+ T cells. Transfer of CD4+ spleen T cells from OVA-pretreated animals protected naive recipients against subsequent allergen sensitization and airway disease, whereas transfer from LPS/OVA-pretreated animals only protected against allergen sensitization. Conclusion: Microbial LPS modulated mucosal tolerance by inducing allergen-specific IgG1 production and distinct effector CD4+ T cells with a mixed regulatory/Th1 phenotype. Organic dust components such as LPS might therefore be important immune modulators in naturally occurring or preventive allergen-specific tolerance induction.

Surfactant protein D alters allergic lung responses in mice and human subjects

Surfactant protein (SP) D has been proposed to be protective in allergic airway responses. We aimed to determine the effect of SP-D deficiency on murine and human airway allergy. Immunologic responses of SP-D gene-deficient mice (Sftpd-/-) at baseline and after 4 intranasal Aspergillus fumigatus exposures were assessed. In addition, the significance of a single nucleotide polymorphism (Met(11)Thr) in the human SP-D gene (known to decrease SP-D function) was investigated. Macrophage and neutrophil bronchoalveolar lavage fluid levels and large airway mucus production were increased in naive Sftpd-/- mice in association with increased lung CCL17 levels and CD4+ T cell numbers. T(H)2-associated antibody levels (IgG1 and IgE) were significantly lower in 4- to 5-week-old Sftpd-/- mice (P < .05). Accordingly, naive Sftpd-/- splenocytes released significantly less IL-4 and IL-13 on anti-CD3/CD28 stimulation (P < .01). After intranasal allergen exposures, a modest decrease in bronchoalveolar lavage fluid eosinophilia and IL-13 levels was observed in Sftpd-/- mice compared with values seen in wild-type mice in association with decreased airway resistance (P < .01). A single nucleotide polymorphism in the SFTPD gene, affecting SP-D levels and pathogen binding, was associated with decreased atopy in black subjects and potentially lower asthma susceptibility in white subjects. Sftpd-/- mice have an impaired systemic T(H)2 response at baseline and reduced inflammation and airway responses after allergen exposure. Translational studies revealed that a polymorphism in the SFTPD gene was associated with lower atopy and possibly asthma susceptibility. Taken together, these results support the hypothesis that SP-D-dependent innate immunity influences atopy and asthma.

IL‐13Rα2 and IL‐10 coordinately suppress Th2‐dependent Inflammation and Immunopathology.

Immunopathology; such as airway hyper responsiveness (AHR) in asthmatics and fibrotic lesions following infection with Schistosoma sp. often result from excessive inflammation. However, the transition from inflammation to immunopathology is poorly understood. This study aimed to dissect critical mediators during Th2‐driven inflammation, following infection or airway allergen provocation, which mediate down‐stream pathology and to subsequently identify the regulatory mechanisms that control them. To separate inflammation from immunopathology, we used two in‐vivo models ‐ a model of asthma and Schistosomiasis, both of which present distinctive inflammation and downstream pathological changes. Following allergen challenge or infection, we observed an accumulation of IL‐10+ and Foxp3+ regulatory T cells (Treg) in the lungs or liver respectively. In the absence of IL‐10, Th2 inflammation was exacerbated, as well as the emergence of Th1 responses. Paradoxically, despite increased inflammation in IL‐10–/– mice pathology was curtailed. In both the lung and the liver, IL‐13R α 2, an endogenous neutralizer of IL‐13, was elevated. To test the role of IL‐13R α 2 in regulating Th2 pathology we generated mice deficient in both IL‐13R α 2 and IL‐10 (dKO). The absence of IL‐13R α 2, on an IL‐10–/– background, increased lung and liver pathology, compared to IL‐10–/– mice, indicating that IL‐13R α 2 is a key regulator of pathology, even during uncontrolled inflammation. This study presents a novel two‐pronged model of immunoregulation by IL‐10‐secreting Treg's and IL‐13R α 2, which could be exploited to control a variety of important Th2‐dominant diseases.

Reduced Lung Function in a Chronic Asthma Model Is Associated with Prolonged Inflammation, but Independent of Peribronchial Fibrosis

BackgroundIn asthma, mechanisms contributing to chronicity remain to be determined. Recent models of sensitisation with prolonged airway allergen challenges reproduce typical features of chronic asthma. However, the interplay between inflammation, structural changes and lung function is poorly understood. This study was performed to delineate functional, structural and immunological airway changes after cessation of long term challenges to elucidate factors contributing to the development of prolonged lung function changes.Methodology/Principal FindingsMice sensitised systemically were consecutively challenged intranasally with ovalbumin for two or eight weeks. After the end of challenges, lung function, airway inflammation, features of airway remodelling, local T-cell cytokines and systemic ovalbumin-specific antibodies were monitored. Long term challenges resulted in airway hyperresponsiveness lasting 2 weeks and reduced baseline lung function for 6 weeks after their cessation. In contrast, these changes resolved within one week after short term challenges. Prolonged transforming growth factor beta (TGF-β)1 production and marked peribronchial fibrosis were only induced by long term challenges. Importantly, fibrosis became apparent only after the onset of lung function changes and outlasted them. Further, long term challenges led to prolonged and intense airway inflammation with marked lymphocytosis, but moderate eosinophilia, sustained IL-5 production and ovalbumin-specific IgG2a antibodies, the latter suggesting a Th1 component to the immune response. In contrast, following short term challenges airway inflammation was dominated by eosinophils and associated with a strong, but transient IL-13 response.ConclusionsProlonged lung function changes after long term allergen challenges seem to develop and resolve independently of the persistent peribronchial fibrosis. They are more closely associated with intense airway inflammation, marked lymphocytosis, prolonged IL-5 and TGF-β1 production in the airways and a Th1 immune response.

OR.12. Perinatal Exposure to Environmental Estrogen, Bisphenol A (BPA), Promotes Allergic Sensitization and Airway Responsiveness in an Animal Model of Asthma

OR.12. Perinatal Exposure to Environmental Estrogen, Bisphenol A (BPA), Promotes Allergic Sensitization and Airway Responsiveness in an Animal Model of Asthma

Respiratory Virus-Induced Regulation of Asthma-Like Responses in Mice Depends upon CD8 T Cells and Interferon-γ Production

Respiratory virus infections can significantly influence the development of airway disease by both predisposing and exacerbating the developing lung immune environment. In contrast, the initiation of a more desirable anti-viral response may better prepare the local environment and protect it from developing an adverse long-term disease phenotype. BALB/c or C57BL/6 mice exposed to respiratory syncytial virus (RSV) infection at the same time as allergen sensitization were assessed for airway function, cytokine responses, and inflammatory parameters. Depending on the genetic strain of mouse used, BALB/c versus C57BL/6, RSV could differentially protect against the development of airway allergen responses. Although RSV was able to block allergen sensitization and induction of airway hyperresponsiveness and eosinophilic inflammation in C57BL/6 mice, the infection did not reduce the allergic responses in BALB/c mice. The alteration of airway responsiveness did not depend on the timing of RSV infection in C57BL/6 mice in conjunction to the allergen sensitization protocol. Neutralization experiments demonstrated that interferon-gamma contributed significantly to the RSV-induced airway attenuation of the allergic responses, whereas transfer of CD8 T cells from RSV-infected animals suggested that they were partially responsible for the altered environment. These data suggest that a respiratory viral infection impacts on the local lung environment and may reflect specific aspects of the hygiene hypothesis. However, the outcome of this interaction depends on the immunological response of the host.

Inhibition of Airway Allergic Disease by Co-Administration of Flagellin with Allergen

Bacterial flagellin, which activates Toll-like receptor 5 and cytosolic pattern recognition receptor Ipaf, has a strong immunomodulatory activity. In the present study, we examined whether intranasal co-administration of flagellin with allergen could modulate established airway hyperresponsiveness and Th2 response using an ovalbumin (OVA)-sensitized mouse model. Balb/c mice sensitized with OVA were treated with OVA-flagellin (FlaB) mixture three times at 1-week intervals. Seven days after the final OVA-FlaB administration, the mice were challenged with OVA inhalation, and airway responses and OVA-specific immune responses were evaluated. The OVA-FlaB treatment significantly suppressed OVA-induced airway hyperresponsiveness, airway eosinophilic inflammation, and OVA-specific Th2 cytokine productions in splenocytes. These results indicate that flagellin co-administered with allergen can modulate airway inflammatory response through inhibition of Th2 responses, and flagellin can be considered as a component for allergen-specific immunotherapy.

Regulation of allergen‐induced bone marrow eosinophilopoiesis: role of CD4+ and CD8+ T cells

The mechanisms of the distant stimulation of the bone marrow (BM) after airway allergen exposure remain largely obscure. T cells have been implicated in allergic airway inflammation but their role in allergen-induced BM eosinophilopoiesis is poorly understood. The aim of this study was to determine the role of CD4(+) and CD8(+) T cells in allergen-induced BM eosinophilopoiesis. Ovalbumin (OVA)-sensitized wild type (WT), CD4 knockout (CD4-/-) and CD8 knockout (CD8-/-) mice were exposed intranasally to OVA or saline. Bromo-deoxyuridine (BrdU) was used to label newly produced cells. Bone marrow, blood and bronchoalveolar lavage (BAL) were sampled 24 h after the final exposure. Immunostaining for newly produced eosinophils (i.e. BrdU(+)/MBP(+)) and BM eosinophil progenitor [CD34(+)/CD45(+)/interleukin-5 (IL-5)Ralpha(+)] cells was performed. The number of newly produced BM eosinophils (BrdU(+)/MBP(+) cells) was significantly reduced in allergen exposed CD4-/- or CD8-/- mice compared with allergen exposed WT mice, which was followed by a subsequent decrease in newly produced blood and airway eosinophils. Furthermore, BM eosinophil progenitors were significantly reduced in allergen exposed CD4-/- and CD8-/- mice compared with WT mice. Finally, serum IL-5 and Bronchoalveolar lavage fluid eotaxin-2 levels were abolished in allergen exposed CD4-/- mice to levels seen in saline exposed WT mice. These data suggests that both CD4(+) and CD8(+) T cells have a regulatory role in allergen-induced BM eosinophilopoiesis, whereas CD4(+) T cells are obligatory for allergen-induced airway eosinophilia. The subsequent traffic of eosinophils to the airways is likely to be at least partly regulated by a CD4(+) T-cell-dependent local airway eotaxin-2 production.

γ‐Tocopherol prevents airway eosinophilia and mucous cell hyperplasia in experimentally induced allergic rhinitis and asthma

Traditional therapies for asthma and allergic rhinitis (AR) such as corticosteroids and antihistamines are not without limitations and side effects. The use of complementary and alternative approaches to treat allergic airways disease, including the use of herbal and dietary supplements, is increasing but their efficacy and safety are relatively understudied. Previously, we have demonstrated that gamma-tocopherol (gammaT), the primary form of dietary vitamin E, is more effective than alpha-tocopherol, the primary form found in supplements and tissue, in reducing systemic inflammation induced by non-immunogenic stimuli. We used allergic Brown Norway rats to test the hypothesis that a dietary supplement with gammaT would protect from adverse nasal and pulmonary responses to airway allergen provocation. Ovalbumin (OVA)-sensitized Brown Norway rats were treated orally with gammaT before intranasal provocation with OVA. Twenty-four hours after two challenges, histopathological changes in the nose, sinus and pulmonary airways were compared with gene expression and cytokine production in bronchoalveolar lavage fluid and plasma. We found that acute dosing for 4 days with gammaT was sufficient to provide broad protection from inflammatory cell recruitment and epithelial cell alterations induced by allergen challenge. Eosinophil infiltration into airspaces and tissues of the lung, nose, sinus and nasolacrimal duct was blocked in allergic rats treated with gammaT. Pulmonary production of soluble mediators PGE(2), LTB(4) and cysteinyl leukotrienes, and nasal expression of IL-4, -5, -13 and IFN-gamma were also inhibited by gammaT. Mucous cell metaplasia, the increase in the number of goblet cells and amounts of intraepithelial mucus storage, was induced by allergen in both pulmonary and nasal airways and decreased by treatment with gammaT. Acute treatment with gammaT inhibits important inflammatory pathways that underlie the pathogenesis of both AR and asthma. Supplementation with gammaT may be a novel complementary therapy for allergic airways disease.

Function and Regulation of SPLUNC1 Protein in Mycoplasma Infection and Allergic Inflammation

Respiratory infections, including Mycoplasma pneumoniae (Mp), contribute to asthma pathobiology. To date, the mechanisms underlying the increased susceptibility of asthmatics to airway Mp infection remain unclear. Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) protein is a recently described large airway epithelial cell-derived molecule that was predicted to exert host defense activities. However, SPLUNC1 function and regulation in an infectious or allergic milieu are still unknown. We determined host defense and anti-inflammatory functions of SPLUNC1 protein in Mp infection and the regulation of SPLUNC1 by Mp and allergic inflammation (e.g., IL-13). SPLUNC1 function was examined in Mp or human airway epithelial cell cultures by using SPLUNC1 recombinant protein, overexpression and RNA interference. Human and mouse bronchial epithelial SPLUNC1 was examined using immunostaining, Western blotting, ELISA, laser capture microdissection, and real-time PCR. Mouse models of Mp infection and allergic inflammation and air-liquid interface cultures of normal human primary bronchial epithelial cells were used to study SPLUNC1 regulation by Mp and IL-13. We found that: 1) SPLUNC1 protein decreased Mp levels and inhibited epithelial IL-8 production induced by Mp-derived lipoproteins; 2) normal human and mouse large airway epithelial cells expressed high levels of SPLUNC1; and 3) although Mp infection increased SPLUNC1, IL-13 significantly decreased SPLUNC1 expression and Mp clearance. Our results suggest that SPLUNC1 serves as a novel host defense protein against Mp and that an allergic setting markedly reduces SPLUNC1 expression, which may in part contribute to the persistent nature of bacterial infections in allergic airways.

Immunostimulatory sequences in immunotherapy

To review the current literature regarding immunostimulatory sequences of DNA for immunotherapy with respect to signaling mechanisms, cytokine profiles, structural characteristics and the applicability and success of this strategy to treat allergic disease. The binding of synthetic DNA-based immunotherapy agents composed of unmethylated cytosine-guanine dinucleotides (CpG ODN) to toll-like receptors have been found to be species-specific. CpG ODNs are capable of inducing a shift in the cytokine profile and immune response that favors the Th1 pathway and suppresses the Th2 pathway. This makes using CpG ODNs a promising candidate for the treatment of allergic diseases, which are known to be mediated by Th2-based response. Current CpG ODN studies have demonstrated prevention and reversal of acute allergen inflammation, airway hyper-reactivity and remodeling. Early animal and human trials of CpG ODNs have shown them to be both well tolerated and effective. The use of immunostimulatory sequences in immunotherapy, although still in the early stages of development, has thus far been shown to be both well tolerated and effective, and offers the potential for a better tolerated, more rapid, more efficacious and longer-lasting therapy over current immunotherapy protocols.

T H2 and T H1 lung inflammation induced by airway allergen sensitization with low and high doses of double-stranded RNA

Although respiratory viral infections in early childhood can enhance the development of airway allergen sensitization, the exact mechanisms of the effects of viral infections on the adaptive immune response to inhaled allergens are controversial. We sought to evaluate the effects of double-stranded RNA (dsRNA) on airway sensitization to inhaled allergens. Novel mouse models were created through simultaneous airway sensitization to an allergen and low or high doses of dsRNA. The mouse models were applied to Toll-like receptor 3-, IL-13-, IL-4-, signal transducer and activator of transcription (STAT) 6-, IFN-gamma-, and T-box expressed in T cells (T-bet)-deficient mice to evaluate underlying pathophysiologic mechanisms in the development of allergic lung inflammation. We found that airway allergen sensitization with dsRNA induced lung inflammation that was not present in Toll-like receptor 3-deficient mice. Moreover, lung inflammation enhanced by low-dose dsRNA was impaired in IL-13-deficient mice, whereas lung inflammation by high-dose dsRNA was impaired in IFN-gamma-deficient mice. The models also demonstrated that low-dose dsRNA enhanced IL-4 expression during allergen sensitization and that inflammation enhanced by low-dose dsRNA was not present in IL-4- or STAT6-deficient mice. In contrast, the present study showed that high-dose dsRNA enhanced IFN-gamma expression during allergen sensitization and that the development of lung inflammation enhanced by high-dose dsRNA was impaired in T-bet-deficient mice. These findings suggest that airway allergen exposure during respiratory viral infections might induce asthma induced by both T(H)1 and T(H)2 immune responses to inhaled allergens. Targeting both T(H)1 and T(H)2 lung inflammation might be important in the treatment of virus-associated asthma.

Intranasal delivery of whole influenza vaccine prevents subsequent allergen‐induced sensitization and airway hyper‐reactivity in mice

Infection with influenza virus has been associated with seemingly opposing effects on the development of asthma. However, there are no data about the effects of mucosal vaccination with inactivated influenza on the inception of allergic asthma. To assess the immunological effects of inhaled inactivated influenza vaccine, using two different types of flu vaccines, on the inception of allergic sensitization and allergen-mediated airway disease in a mouse model. BALB/c mice were intranasally or intratracheally vaccinated with whole or split influenza virus vaccine (days -1 or -1, 27) before systemic sensitization with ovalbumin (OVA) (days 1, 14) and repeated airway allergen challenges (days 28-30). Allergen sensitization (IgE serum levels), airway inflammation (differential cells in bronchoalveolar lavage fluid) and airway hyper-reactivity (AHR) (in vivo lung function) were analysed. The intranasal instillation of whole influenza vaccine before allergen sensitization significantly reduced the serum levels of total and OVA-specific IgE as well as allergen-induced AHR. Prevention was due to an allergen-specific shift from a predominant T helper (Th)2- towards a Th1-immune response. Application of split influenza vaccine did not show the same preventive effect. Intranasal administration of inactivated whole influenza vaccine reduced subsequent allergen sensitization and prevented allergen-induced AHR. Our results show that the composition of the influenza vaccine has a major influence on subsequent development of allergen-induced sensitization and AHR, and suggest that mucosal inactivated whole influenza vaccination may represent a step towards the development of a preventive strategy for atopic asthma.