Development Of Allergen-induced Airway Hyperresponsiveness Research Articles

Diacylglycerol Kinase Inhibition Reduces Airway Contraction by Negative Feedback Regulation of Gq-Signaling.

Exaggerated airway smooth muscle (ASM) contraction regulated by the Gq family of G protein-coupled receptors causes airway hyperresponsiveness in asthma. Activation of Gq-coupled G protein-coupled receptors leads to phospholipase C (PLC)-mediated generation of inositol triphosphate (IP3) and diacylglycerol (DAG). DAG signaling is terminated by the action of DAG kinase (DGK) that converts DAG into phosphatidic acid (PA). Our previous study demonstrated that DGKζ and α isoform knockout mice are protected from the development of allergen-induced airway hyperresponsiveness. Here we aimed to determine the mechanism by which DGK regulates ASM contraction. Activity of DGK isoforms was inhibited in human ASM cells by siRNA-mediated knockdown of DGKα and ζ, whereas pharmacological inhibition was achieved by pan DGK inhibitor I (R59022). Effects of DGK inhibition on contractile agonist-induced activation of PLC and myosin light chain (MLC) kinase, elevation of IP3, and calcium levels were assessed. Furthermore, we used precision-cut human lung slices and assessed the role of DGK in agonist-induced bronchoconstriction. DGK inhibitor I attenuated histamine- and methacholine-induced bronchoconstriction. DGKα and ζ knockdown or pretreatment with DGK inhibitor I resulted in attenuated agonist-induced phosphorylation of MLC and MLC phosphatase in ASM cells. Furthermore, DGK inhibition decreased Gq agonist-induced calcium elevation and generation of IP3 and increased histamine-induced production of PA. Finally, DGK inhibition or treatment with DAG analog resulted in attenuation of activation of PLC in human ASM cells. Our findings suggest that DGK inhibition perturbed the DAG:PA ratio, resulting in inhibition of Gq-PLC activation in a negative feedback manner, resulting in protection against ASM contraction.

Requirement for neuropeptide Y in the development of allergen-induced airway hyperresponsiveness and inflammation

Requirement for neuropeptide Y in the development of allergen-induced airway hyperresponsiveness and inflammation

Inducible and naturally occurring regulatory T cells enhance lung allergic responses through divergent transcriptional pathways

Regulatory Tcells attenuate development of asthma in wild-type (WT) mice, with both naturally occurring regulatory T (nTreg) cells and inducible regulatory T (iTreg) cells exhibiting suppressive activity. When transferred into CD8-deficient (CD8-/-) recipients, both cell types enhanced development of allergen-induced airway hyperresponsiveness. We sought to determine whether the pathways leading to enhancement of lung allergic responses by transferred nTreg and iTreg cells differed. nTreg cells (CD4+CD25+) were isolated from WT mice and iTreg cells were generated from WT CD4+CD25- Tcells after activation in the presence of TGF-β and transferred into sensitized CD8-/- recipients before challenge. Development of airway hyperresponsiveness, cytokine levels, and airway inflammation were monitored. Transfer of nTreg cells enhanced lung allergic responses, as did transfer of iTreg cells. Although anti-IL-13 reduced nTreg cell-mediated enhancement, it was ineffective in iTreg cell-mediated enhancement; conversely, anti-IL-17, but not anti-IL-13, attenuated the enhancement by iTreg cells. Recovered iTreg cells from the lungs of CD8-/- recipients were capable of IL-17 production and expressed high levels of signature genes of the TH17 pathway, RORγt and Il17, whereas reduced expression of the Treg cell key transcription factor forkhead box p3 (Foxp3) was observed. Invitro exogenous IL-6-induced IL-17 production in iTreg cells, and invivo conversion of transferred iTreg cells was dependent on recipient IL-6. iTreg cells, similar to nTreg cells, exhibit functional plasticity and can be converted from suppressor cellsto pathogenic effector cells, enhancing lung allergic responses, but these effects were mediated through different pathways.

Blockade of JAK1/3 signaling with a selective inhibitor, R256, attenuates Th2 differentiation and development of allergen-induced airway hyperresponsiveness (AHR) and airway inflammation (P6047)

Abstract JAK are major downstream regulators of signaling through cytokine receptors, activating STAT. Effective targeting of the Th2-associated JAK-STAT pathway would represent a new therapeutic approach for the treatment of asthma. Here, we studied the effects of a novel selective JAK1/3 inhibitor, R256, on Th1, Th2, and Th17 differentiation in vitro and on the development of ovalubmin-induced AHR and airway inflammation in vivo in mice. R256 prevented only Th2 differentiation in vitro and was associated with the downregulation of STAT5 and STAT6 phosphorylation. In contrast, Th2 cells were unaffected by the inhibitor when added after polarization was complete. In vivo, R256 administered during the allergen sensitization phase prevented the development of AHR, airway eosinophilia, mucus hypersecretion, and Th2 cytokine production without altering Th1 and Th17 cytokine production, indicating that selective blockade of Th2 differentiation was critical. Inhibitor administration after allergen sensitization but during the challenge phase also suppressed AHR, airway eosinophilia, and mucus hypersecretion but no effect on Th2 cytokine levels in BAL could be detected, suggesting effects on downstream cytokine receptor signaling pathways. Thus, R256-mediated inhibition of JAK1/3 activation was effective when administered both prior to and after Th2 polarization to attenuate allergen-induced Th2 dominant airway inflammation and AHR.

The Critical Role of Complement Alternative Pathway Regulator Factor H in Allergen-Induced Airway Hyperresponsiveness and Inflammation

Activation of the alternative pathway of complement plays a critical role in the development of allergen-induced airway hyperresponsiveness (AHR) and inflammation in mice. Endogenous factor H, a potent inhibitor of the alternative pathway, is increased in the airways of sensitized and challenged mice, but its role in regulating inflammation or AHR has been unknown. We found that blocking the tissue-binding function of factor H with a competitive antagonist increased complement activation and tissue inflammation after allergen challenge of sensitized mice. Conversely, administration of a fusion protein that contains the iC3b/C3d binding region of complement receptor 2 linked to the inhibitory region of factor H, a molecule directly targeting complement-activating surfaces, protected mice in both primary and secondary challenge models of AHR and lung inflammation. Thus, although endogenous factor H does play a role in limiting the development of AHR, strategies to deliver the complement-regulatory region of factor H specifically to the site of inflammation provide greater protection than that afforded by endogenous regulators. Such an agent may be an effective therapy for the treatment of asthma.

Low-Dose Lipopolysaccharide Affects Lung Allergic Responses by Regulating Jagged1 Expression on Antigen-Pulsed Dendritic Cells

Background: Notch signaling pathways govern immune function and the regulation of Th1 and Th2 differentiation. We previously demonstrated essential interactions between Notch on CD4+ T cells and Jagged1 on antigen-presenting cells in Th2 differentiation for the full development of allergen-induced airway hyperresponsiveness (AHR) and allergic airway inflammation. Methods: Bone marrow-derived dendritic cells (BMDCs) were differentiated and incubated with different preparations of ovalbumin (OVA), including lipopolysaccharide (LPS)-depleted and LPS-spiked preparations. In some experiments recipient mice also received soluble Jagged1-Fc in addition to allergen-pulsed BMDCs. Ten days following transfer of BMDCs, mice were exposed to three airway challenges with OVA, and airway responsiveness to inhaled methacholine, airway inflammation and cytokine production were monitored 48 h later. Notch ligand expression was assessed by real-time PCR. Results: Induction of Jagged1 expression on antigen-pulsed BMDCs was dependent on low-dose endotoxin. In vivo, transfer of endotoxin-free, antigen-pulsed BMDCs failed to induce AHR or airway eosinophilia on allergen challenge. However, administration of exogenous Jagged1-Fc together with endotoxin-free, allergen-pulsed BMDCs fully restored the responses to allergen challenge. Conclusions: These data demonstrate that LPS regulates the expression of Jagged1 on BMDCs, which is essential for the full development of lung allergic responses.

Requirement for Chemokine Receptor 5 in the Development of Allergen-Induced Airway Hyperresponsiveness and Inflammation

Chemokine receptor (CCR) 5 is expressed on dendritic cells, macrophages, CD8 cells, memory CD4 T cells, and stromal cells, and is frequently used as a marker of T helper type 1 cells. Interventions that abrogate CCR5 or interfere with its ligand binding have been shown to alter T helper type 2-induced inflammatory responses. The role of CCR5 on allergic airway responses is not defined. CCR5-deficient (CCR5(-/-)) and wild-type (CCR5(+/+)) mice were sensitized and challenged with ovalbumin (OVA) and allergic airway responses were monitored 48 hours after the last OVA challenge. Cytokine levels in lung cell culture supernatants were also assessed. CCR5(-/-) mice showed significantly lower airway hyperresponsiveness (AHR) and lower numbers of total cells, eosinophils, and lymphocytes in bronchoalveolar lavage (BAL) fluid compared with CCR5(+/+) mice after sensitization and challenge. The levels of IL-4 and IL-13 in BAL fluid of CCR5(-/-) mice were lower than in CCR5(+/+) mice. Decreased numbers of lung T cells were also detected in CCR5(-/-) mice after sensitization and challenge. Transfer of OVA-sensitized T cells from CCR5(+/+), but not transfer of CCR5(-/-) cells, into CCR5(-/-) mice restored AHR and numbers of eosinophils in BAL fluid after OVA challenge. Accordingly, the numbers of airway-infiltrating donor T cells were significantly higher in the recipients of CCR5(+/+) T cells. Taken together, these data suggest that CCR5 plays a pivotal role in allergen-induced AHR and airway inflammation, and that CCR5 expression on T cells is essential to the accumulation of these cells in the airways.

Phosphodiesterase 4B is essential for TH2-cell function and development of airway hyperresponsiveness in allergic asthma

Cyclic AMP (cAMP) signaling modulates functions of inflammatory cells involved in the pathogenesis of asthma, and type 4 cAMP-specific phosphodiesterases (PDE4s) are essential components of this pathway. Induction of the PDE4 isoform PDE4B is necessary for Toll-like receptor signaling in monocytes and macrophages and is associated with T cell receptor/CD3 in T cells; however, its exact physiological function in the development of allergic asthma remains undefined. We investigated the role of PDE4B in the development of allergen-induced airway hyperresponsiveness (AHR) and T(H)2-driven inflammatory responses. Wild-type and PDE4B(-/-) mice were sensitized and challenged with ovalbumin and AHR measured in response to inhaled methacholine. Airway inflammation was characterized by analyzing leukocyte infiltration and cytokine accumulation in the airways. Ovalbumin-stimulated cell proliferation and T(H)2 cytokine production were determined in cultured bronchial lymph node cells. Mice deficient in PDE4B do not develop AHR. This protective effect was associated with a significant decrease in eosinophils recruitment to the lungs and decreased T(H)2 cytokine levels in the bronchoalveolar lavage fluid. Defects in T-cell replication, T(H)2 cytokine production, and dendritic cell migration were evident in cells from the airway-draining lymph nodes. Conversely, accumulation of the T(H)1 cytokine IFN-γ was not affected in PDE4B(-/-) mice. Ablation of the orthologous PDE4 gene PDE4A has no impact on airway inflammation. By relieving a cAMP-negative constraint, PDE4B plays an essential role in T(H)2-cell activation and dendritic cell recruitment during airway inflammation. These findings provide proof of concept that PDE4 inhibitors with PDE4B selectivity may have efficacy in asthma treatment.

Plasticity of Invariant NKT Cell Regulation of Allergic Airway Disease Is Dependent on IFN-γ Production

Invariant NKT cells (iNKT cells) play a pivotal role in the development of allergen-induced airway hyperresponsiveness (AHR) and inflammation. However, it is unclear what role they play in the initiation (sensitization) phase as opposed to the effector (challenge) phase. The role of iNKT cells during sensitization was examined by determining the response of mice to intratracheal transfer of OVA-pulsed or OVA-alpha-galactosylceramide (OVA/alphaGalCer)-pulsed bone marrow-derived dendritic cells (BMDCs) prior to allergen challenge. Wild-type (WT) recipients of OVA-BMDCs developed AHR, increased airway eosinophilia, and increased levels of Th2 cytokines in bronchoalveolar lavage fluid, whereas recipients of OVA/alphaGalCer BMDCs failed to do so. In contrast, transfer of these same OVA/alphaGalCer BMDCs into IFN-gamma-deficient (IFN-gamma(-/-)) mice enhanced the development of these lung allergic responses, which was reversed by exogenous IFN-gamma treatment following OVA-BMDC transfer. Further, Jalpha18-deficient recipients, which lack iNKT cells, developed the full spectrum of lung allergic responses following reconstitution with highly purified WT liver or spleen iNKT cells and transfer of OVA-BMDCs, whereas reconstituted recipients of OVA/alphaGalCer BMDCs failed to do so. Transfer of iNKT cells from IFN-gamma(-/-) mice restored the development of these responses in Jalpha18-deficient recipients following OVA-BMDC transfer; the responses were enhanced following OVA/alphaGalCer BMDC transfer. iNKT cells from these IFN-gamma(-/-) mice produced higher levels of IL-13 in vitro compared with WT iNKT cells. These data identify IFN-gamma as playing a critical role in dictating the consequences of iNKT cell activation in the initiation phase of the development of AHR and airway inflammation.

Natural killer T cells are dispensable in the development of allergen-induced airway hyperresponsiveness, inflammation and remodelling in a mouse model of chronic asthma

Natural killer T (NK T) cells have been shown to play an essential role in the development of allergen-induced airway hyperresponsiveness (AHR) and/or airway inflammation in mouse models of acute asthma. Recently, NK T cells have been reported to be required for the development of AHR in a virus induced chronic asthma model. We investigated whether NK T cells were required for the development of allergen-induced AHR, airway inflammation and airway remodelling in a mouse model of chronic asthma. CD1d-/- mice that lack NK T cells were used for the experiments. In the chronic model, AHR, eosinophilic inflammation, remodelling characteristics including mucus metaplasia, subepithelial fibrosis and increased mass of the airway smooth muscle, T helper type 2 (Th2) immune response and immunoglobulin (Ig)E production were equally increased in both CD1d-/- mice and wild-type mice. However, in the acute model, AHR, eosinophilic inflammation, Th2 immune response and IgE production were significantly decreased in the CD1d-/- mice compared to wild-type. CD1d-dependent NK T cells may not be required for the development of allergen-induced AHR, eosinophilic airway inflammation and airway remodelling in chronic asthma model, although they play a role in the development of AHR and eosinophilic inflammation in acute asthma model.

Allergen Uptake, Activation, and IL-23 Production by Pulmonary Myeloid DCs Drives Airway Hyperresponsiveness in Asthma-Susceptible Mice

Maladaptive, Th2-polarized inflammatory responses are integral to the pathogenesis of allergic asthma. As regulators of T cell activation, dendritic cells (DCs) are important mediators of allergic asthma, yet the precise signals which render endogenous DCs “pro-asthmatic”, and the extent to which these signals are regulated by the pulmonary environment and host genetics, remains unclear. Comparative phenotypic and functional analysis of pulmonary DC populations in mice susceptible (A/J), or resistant (C3H) to experimental asthma, revealed that susceptibility to airway hyperresponsiveness is associated with preferential myeloid DC (mDC) allergen uptake, and production of Th17-skewing cytokines (IL-6, IL-23), whereas resistance is associated with increased allergen uptake by plasmacytoid DCs. Surprisingly, adoptive transfer of syngeneic HDM-pulsed bone marrow derived mDCs (BMDCs) to the lungs of C3H mice markedly enhanced lung IL-17A production, and rendered them susceptible to allergen-driven airway hyperresponsiveness. Characterization of these BMDCs revealed levels of antigen uptake, and Th17 promoting cytokine production similar to that observed in pulmonary mDCs from susceptible A/J mice. Collectively these data demonstrate that the lung environment present in asthma-resistant mice promotes robust pDC allergen uptake, activation, and limits Th17-skewing cytokine production responsible for driving pathologic T cell responses central to the development of allergen-induced airway hyperresponsiveness.

Spatial and Phenotypic Characterization of Vascular Remodeling in a Mouse Model of Asthma

Asthma is a chronic inflammatory disease characterized by airway wall remodeling in which vascular remodeling is thought to be a main contributor. Vascular endothelial growth factor (VEGF) is known as a major regulator of angiogenesis and enhancer of vascular permeability. Here, we define the spatial nature of vascular remodeling and the role of VEGF and its receptors (Flt-1 and Flk-1) in the allergic response in mice (A/J) susceptible to the development of allergen-induced airway hyperresponsiveness using morphometric and quantitative approaches. Increased vascularity, vasodilatation, and endothelial cell proliferation were found in the tracheal and bronchial walls in the early and late phases of asthma. Vascular changes were observed not only in small vessels but also in larger vessels. In contrast to normal control, lung tissue from the asthma model showed dual expression for CD31 and von Willebrand factor in the endothelial cells and α-smooth muscle actin and desmin in the mural cells of the vessels, suggesting a phenotypic and functional transformation. The mRNA levels of VEGF isoforms, VEGF₁₆₄ and VEGF₁₈₈, were significantly increased in the tracheal and lung tissue, respectively. In addition, the mRNA level of VEGF receptor Flk-1 was significantly increased in the trachea. These results establish the existence of vascular remodeling in the airways in a mouse model of allergic asthma and support a key role for the expression of unique VEGF isoform genes as mediators of structural changes.

Critical Role of the Fc Receptor γ-Chain on APCs in the Development of Allergen-Induced Airway Hyperresponsiveness and Inflammation

The FcR common gamma-chain (FcRgamma) is an essential component of the receptors FcepsilonRI, FcgammaRI, and FcgammaRIII, which are expressed on many inflammatory cell types. The role of these receptors in the initiation or maintenance of allergic inflammation has not been well defined. FcRgamma-deficient (FcRgamma(-/-)) and control (wild-type (WT)) mice were sensitized and subsequently challenged with OVA. Following sensitization and challenge to OVA, FcRgamma-deficient (FcRgamma(-/-)) mice developed comparable levels of IgE and IgG1 as WT mice. However, numbers of eosinophils, levels of IL-5, IL-13, and eotaxin in bronchoalveolar lavage fluid, and mononuclear cell (MNC) proliferative responses to OVA were significantly reduced, as was airway hyperresponsiveness (AHR) to inhaled methacholine. Reconstitution of FcRgamma(-/-) mice with whole spleen MNC from WT mice before sensitization restored development of AHR and the numbers of eosinophils in bronchoalveolar lavage fluid; reconstitution after sensitization but before OVA challenge only partially restored these responses. These responses were also restored when FcRgamma(-/-) mice received T cell-depleted MNC, T and B cell-depleted MNC, or bone marrow-derived dendritic cells before sensitization from FcR(+/+) or FcgammaRIII-deficient but not FcRgamma(-/-) mice. The expression levels of FcgammaRIV on bone marrow-derived dendritic cells from FcR(+/+) mice were found to be low. These results demonstrate that expression of FcRgamma, most likely FcgammaRI, on APCs is important during the sensitization phase for the development of allergic airway inflammation and AHR.

CD4+CD25+ T cells protect against experimentally induced asthma and alter pulmonary dendritic cell phenotype and function

The role of natural CD4+CD25+ regulatory T (T reg) cells in the control of allergic asthma remains poorly understood. We explore the impact of T reg cell depletion on the allergic response in mice susceptible (A/J) or comparatively resistant (C3H) to the development of allergen-induced airway hyperresponsiveness (AHR). In C3H mice, anti-CD25–mediated T reg cell depletion before house dust mite treatment increased several features of the allergic diathesis (AHR, eosinophilia, and IgE), which was concomitant with elevated T helper type 2 (Th2) cytokine production. In similarly T reg cell–depleted A/J mice, we observed a moderate increase in airway eosinophilia but no effects on AHR, IgE levels, or Th2 cytokine synthesis. As our experiments suggested that T reg cell depletion in C3H mice before sensitization was sufficient to enhance the allergic phenotype, we characterized dendritic cells (DCs) in T reg cell–depleted C3H mice. T reg cell–depleted mice had increased numbers of pulmonary myeloid DCs with elevated expression of major histocompatibility complex class II, CD80, and CD86. Moreover, DCs from T reg cell–depleted mice demonstrated an increased capacity to stimulate T cell proliferation and Th2 cytokine production, which was concomitant with reduced IL-12 expression. These data suggest that resistance to allergen-driven AHR is mediated in part by CD4+CD25+ T reg cell suppression of DC activation and that the absence of this regulatory pathway contributes to susceptibility.

Inhibition of Spleen Tyrosine Kinase Prevents Mast Cell Activation and Airway Hyperresponsiveness

Spleen tyrosine kinase (Syk) is important for Fc and B-cell receptor-mediated signaling. To determine the activity of a specific Syk inhibitor (R406) on mast cell activation in vitro and on the development of allergen-induced airway hyperresponsiveness (AHR) and inflammation in vivo. AHR and inflammation were induced after 10 d of allergen (ovalbumin [OVA]) exposure exclusively via the airways and in the absence of adjuvant. This approach was previously established to be IgE, FcepsilonRI, and mast cell dependent. Alternatively, mice were passively sensitized with OVA-specific IgE, followed by limited airway challenge. In vitro, the inhibitor was added to cultures of IgE-sensitized bone marrow-derived mast cells (BMMCs) before cross-linking with allergen. The inhibitor prevented OVA-induced degranulation of passively IgE-sensitized murine BMMCs and inhibited the production of interleukin (IL)-13, tumor necrosis factor alpha, IL-2, and IL-6 in these sensitized BMMCs. When administered in vivo, R406 inhibited AHR, which developed in BALB/c mice exposed to aerosolized 1% OVA for 10 consecutive d (20 min/d), as well as pulmonary eosinophilia and goblet cell metaplasia. A similar inhibition of AHR was demonstrated in mice passively sensitized with OVA-specific IgE and exposed to limited airway challenge. This study delineates a functional role for Syk in the development of mast cell- and IgE-mediated AHR and airway inflammation, and these results indicate that inhibition of Syk may be a target in the treatment of allergic asthma.

The therapeutic potential of drugs targeting the arginase pathway in asthma

Arginine metabolism by arginases may be of importance in health and disease, either by competing with nitric oxide synthases for the common substrate or by the production of L-ornithine. L-Ornithine serves as a precursor for L-proline and polyamines, which may be involved in tissue remodelling by promoting collagen synthesis and cell proliferation. Arginase activity potentiates airway reactivity by reducing the production of bronchodilatory nitric oxide. Increased arginase activity has been implicated in the development of allergen-induced airway hyper-responsiveness in experimental asthma. In addition, reduced L-arginine availability to inducible nitric oxide synthase by arginase may lead to an increased production of peroxynitrite, contributing to increased airway smooth muscle contractility, airway inflammation and cell damage in this disease. Recent studies demonstrate that the upregulation of arginase by T helper type 2 cytokines in lung tissue as well as in cultured airway fibroblasts indicates a possible role of the enzyme in airway re-modelling. These findings, in conjunction with human studies showing a role for arginase in acute asthma, open a new horizon for the therapeutic potential of drugs targeting the arginase pathway in asthma.

Interleukin-17 and airway remodelling

Interleukin (IL)-17A is emerging as important in reinforcing innate immunity by orchestrating sustained neutrophilic mobilisation. Even though there are indications of association with specific airway diseases, there is still no final proof that IL-17A plays a truly causative pathogenic role. There is evidence in mice that endogenous IL-17A contributes to the development of allergen-induced airway hyperresponsiveness and there is also evidence that IL-17A stimulates the release of several cytokines with known capacity for airway remodelling, from cells normally residing in the airways. New studies are required to determine whether these effects on local cells actually contribute to airway remodelling in vivo. If this is the case, then IL-17A may constitute a useful target for pharmacotherapeutic intervention in allergic airway disease.

Functional Molecules in Allergic Bronchial Asthma

AbstractFor Abstract see ChemInform Abstract in Full Text.

Functional molecules in allergic bronchial asthma

Bronchial asthma is considered to be a chronic airway inflammatory disease, characterized by airway obstruction, airway eosinophilic inflammation, and airway hyperresponsiveness (AHR) to a variety of stimuli. AHR is thought to be an important symptom, because the severity of the disease is generally correlated with the degree of AHR. Recent clinical studies have demonstrated the involvement of airway inflammation in the development of allergen-induced AHR, although, the mechanism of allergen-induced AHR has not been fully elucidated and remains controversial. In vivo animal models might provide important information on this point. We have established a mouse model of allergic asthma, which is characterized by airway eosinophilia, IgE production, T helper type 2 (Th2) cytokine production in the airway, and AHR, and investigated the role of inflammatory cells and functional molecules. Results from gene-knockout and mutant mice demonstrated the involvement of T cells, mast cells, prostanoids, and Th2 cytokines including interleukin (IL)-4 and IL-5 in the development of allergen-induced airway inflammation and AHR. In contrast, treatment with anti-IL-4 monoclonal antibody (mAb) or anti-IL-5 mAb during allergen inhalation did not inhibit allergen-induced AHR, although the combination of these mAbs clearly inhibited the enhanced responsiveness. These data indicate that it is a better strategy for control of the disease to inhibit or suppress multifunctional molecules like corticosteroids rather than to inhibit a single factor, because bronchial asthma is a multifactorial disease.

Vaccination with allergen-IL-18 fusion DNA protects against, and reverses established, airway hyperreactivity in a murine asthma model.

Vaccination with naked DNA encoding a specific allergen has been shown previously to prevent, but not reverse, the development of allergen-induced airway hyperresponsiveness (AHR). To enhance the effectiveness of DNA vaccine therapies and make possible the treatment of established AHR, we developed a DNA vaccination plasmid containing OVA cDNA fused to IL-18 cDNA. Vaccination of naive mice either with this fusion DNA construct or with an OVA cDNA-containing plasmid protected the mice from the subsequent induction of AHR. Protection from AHR correlated with increased IFN-gamma production and reduced OVA-specific IgE production. The protection appeared to be mediated by IFN-gamma and CD8(+) cells because treatment of mice with neutralizing anti-IFN-gamma mAb or with depleting anti-CD8 mAb abolished the protective effect. Moreover, vaccination of mice with preexisting AHR with the OVA-IL-18 fusion DNA, but not with the OVA cDNA plasmid, reversed established AHR, reduced allergen-specific IL-4, and increased allergen-specific IFN-gamma production. Thus, combining IL-18 cDNA with OVA cDNA resulted in a vaccine construct that protected against the development of AHR, and that was unique among cDNA constructs in its capacity to reverse established AHR.