Changes in asthma-like responses after extended removal from exposure to trimellitic anhydride in the Brown Norway rat model

Background Organic acid anhydride-induced occupational asthma is considered to be IgE-mediated. Airway and skin exposure are the two main routes of sensitization in the work place. Recently we developed an allergic asthmatic Brown Norway rat model sensitized by dermal exposure to trimellitic anhydride (TMA) using an occlusion patch application.
Objectives The objectives of this study were (1) to develop a model of non-occluded dermal exposure leading to allergic sensitization and (2) to examine the effect of extended removal from exposure on persistence of both specific IgE and TMA aerosol-induced airway responses in this model.
Methods TMA powder (4 or 40 mg) was applied, unoccluded, to the skin of rats for 4 h, once/week for 4 weeks. Rats were given a 10-min aerosol challenge to 40 mg/m³ TMA 2 weeks after the last dermal exposure (day 35). Another group was challenged on day 35 and again 18–24 months later. Respiratory enhanced pause (Penh), pulmonary histopathology and inflammation and specific IgE titres were measured.
Results Rats produced dose-dependent specific IgE titres after exposure and developed early-phase (EAR) and late-phase airway responses (LAR) after airway challenge to TMA aerosol as well as airway eosinophilic inflammation. Specific airway responses were still manifested after a second TMA airway challenge given 18–24 months following the initial airway challenge. While persistent, airway inflammation, specific IgE and EAR were significantly attenuated following the second TMA challenge. LAR remained robust at 18–24 months and was not significantly different from the response on day 35.
Conclusions These results demonstrate the persistence of chemical sensitization and further suggest that IgE is not essential for LAR.     

Dose-response and time course of specific IgE and IgG after single and repeated topical skin exposure to dry trimellitic anhydride powder in a Brown Norway rat model

BACKGROUND: Trimellitic anhydride (TMA)-induced occupational asthma is thought to be associated with its ability to acylate proteins and to induce production of TMA-specific immunoglobulin (Ig)E. Though the respiratory tract is considered to be a major exposure route leading to airway sensitization, the potential role of dermal exposure producing asthmatic sensitization is not known. The present study examines the ability of dry TMA powder to sensitize Brown Norway rats when applied, topically, to the skin. METHODS: A patch of hair was carefully clipped with scissors on the rat's back. Dry TMA powder (0.3, 1.25, 5 and 20 mg) was administered on days 0, 7, 14 and 21, and the area occluded with surgical tape overnight after each application. Residual powder recovered from the occluded skin was analyzed by proton nuclear magnetic resonance and was still predominantly TMA. Circulating anti-TMA IgE and IgG were measured by ELISA. RESULTS: TMA elicited dose-dependent production of specific IgE and IgG. Specific antibodies were detectable 2 weeks after the first TMA exposure and peaked between 3 and 4 weeks. CONCLUSION: The data suggest that topical skin exposure to dry TMA powder can induce allergic/immunological sensitization as demonstrated by the production of specific antibodies.     

Assessment of airway sensitization potential of inhaled trimellitic anhydride by monitoring the elicitation phase in a mouse model

While several skin sensitization tests have been developed and are available as regulatory toxicity tests at present, no such tests for the airway have been established. We have been developing an animal model by introducing an elicitation phase into the mouse IgE test (MIGET) for assessment of agricultural chemicals with airway sensitization potential. In the current study, trimellitic anhydride (TMA), a representative low molecular weight (LMW) airway sensitizer, was examined for its sensitization potential in our mouse model. Mice were epicutaneously sensitized to TMA on Days 0 and 7, followed by an inhalation challenge with TMA dust at high or low concentration on Day 14. Groups of different sensitization route including inhalation were established for comparison of effectiveness of immunization. Non-sensitized animals challenged with TMA dust served as controls. An ovalbumin-sensitized and -challenged animals constituted a reference group (OVA). Enhanced pause (Penh) was measured as an indicator of airflow disturbance by using a restrained flow whole body plethysmograph. The high TMA concentration group exhibited an augmented Penh, elevated IgE values, and pronounced influx of eosinophils into their BAL fluid and minor infiltration of inflammatory cells including eosinophils into the lung. The low TMA concentration group also exhibited elevated IgE values and a less frequent occurrence of minor lung inflammation, but these were not accompanied by any positive responses in Penh and BAL fluid. Almost all mice in the other immunization route groups exhibited negative responses for any parameter examined. The OVA group showed no changes in breathing pattern during the inhalation challenge despite presenting a high total serum IgE value. These results suggest that this mouse model may be useful for assessment of airway sensitization potential of agrochemicals, but by way of epicutaneous sensitization.     

Early increase in urinary leukotriene E4 (LTE4) is dependent on allergen dose inhaled during bronchial challenge in asthmatic subjects

BACKGROUND: Urinary leukotriene E4 (LTE4) excretion is a good marker of the rate of total body production of sulfidopeptide leukotrienes released during allergen challenge. METHODS: Twenty-three subjects with allergic asthma were challenged with inhaled allergen, and the urinary excretion of LTE4 was determined by immunoenzymatic assay (associated with HPLC separation) at various intervals after challenge. RESULTS: Allergen challenge caused an early airway response (EAR) with a drop in FEV1 of 40.3+/-9.9%. This was associated with an increase in urine LTE4 excretion for 0-3 h after allergen inhalation (296+/-225.25 pg/mg creatinine) in comparison with baseline values obtained during the night before challenge (101.02+/-61.97 pg/mg creatinine). Urinary LTE4 excretion was significantly higher in subjects who inhaled a higher dose of allergen during challenge (LTE4 during EAR: 211+/-192 pg/mg creatinine in subjects with inhaled total dose of allergen <0.1 biologic units; 408+/-223 pg/mg creatinine in subjects with inhaled total dose >0.1 biologic units). All subjects showed a late airway response (LAR) to allergen of different severity, from mild (FEV1 fall: 15-20%) to severe (>30%); no correlation was found between the increase in urine LTE4 excreted during LAR (3-7 h after challenge) and the severity of LAR, but only subjects with severe LAR showed a significant increase in LTE4 during LAR in comparison with baseline value. CONCLUSIONS: A release of sulfidopeptide leukotrienes, as evaluated by urinary LTE4 excretion, can be documented during EAR and LAR to allergen in relation to the dose of inhaled allergen, and it can represent a useful index of the events underlying the airway inflammatory responses during allergen challenge.     

Effect of anti-nerve growth factor on early and late airway responses in allergic rats

BACKGROUND: The increased production of nerve growth factor (NGF) has been associated with allergen-induced airway hyperresponsiveness and enhanced airway inflammation in experimental models of asthma. The aim of this study was to investigate whether a local application of anti-NGF to the lungs may affect the allergen-specific early (EAR) and late (LAR) airway responses to ovalbumin (Ova) of Ova-sensitized brown Norway rats. METHODS: Rats were sensitized systemically with Ova and were boosted twice intratracheally with Ova aerosol using a microsprayer. Two hours before every boost, the animals were pretreated either with aerosolized anti-NGF or with a control antibody. On day 21, all animals were challenged with inhalational Ova aerosol and pulmonary resistance was recorded in anesthetized, orotracheally intubated animals during the early and late asthmatic responses. In addition, differential cell counts from bronchoalveolar lavage and serum immunoglobulin E (IgE) levels were determined 48 h post-Ova challenge. RESULTS: Pretreatment with anti-NGF significantly attenuated the EAR but had no significant effect on the LAR. Serum IgE levels and inflammatory cell influx into the lungs were not affected by anti-NGF pretreatment. CONCLUSION: The data from this study suggest that NGF is directly involved in the development of the EAR without affecting the inflammatory airway response or LAR.     

The effects of CD8+gammadelta T cells on late allergic airway responses and airway inflammation in rats

BACKGROUND: Gamma-delta (gammadelta) T cells regulate immune responses to foreign protein at mucosal surfaces. Whether they can modify allergen-induced early (EAR) and late airway responses (LAR) is unknown. OBJECTIVE: We have tested the hypothesis that the CD8+ subtype of gammadelta T cells decreases allergen-induced LAR and airway eosinophilia in the rat. METHODS: Brown Norway rats were administered, intraperitoneally, 3.5 x 10(4) lymph node CD8+gammadelta T cells from naive or sensitized rats. The recipients were sensitized to ovalbumin (OVA) in Al(OH)(3) 3 days after cell transfer and challenged with aerosolized OVA 14 days later. Serum IgE was measured before allergen challenge. After challenge, lung resistance was monitored for 8 hours and then bronchoalveolar lavage (BAL) was analyzed for eosinophil major basic protein (MBP), IL-4, IL-5, IL-13, and IFN-gamma messenger RNA-expressing cells. RESULTS: gammadelta T cells from naive donors significantly decreased LAR in OVA-challenged sensitized rats, whereas MBP(+) eosinophils were decreased by both gammadelta T cells from naive and sensitized donors. EAR and serum IgE levels were unchanged. The expression of IL-4, IL-5, and IL-13 by BAL cells of gammadelta T cell recipients was attenuated compared with OVA-challenged controls. This was accompanied by an increase in the expression of IFN-gamma. CONCLUSIONS: Our results are consistent with a suppressive role of CD8+gammadelta T cells on allergic airway responses. However, only gammadelta T cells from naive donors inhibit LAR.     

Blood markers of early and late airway responses to allergen in asthmatic subjects. Relationship with functional findings

We evaluated the relationship between blood markers of mast-cell (plasma histamine and serum level of heat-stable neutrophil chemotactic activity [NCA]) and eosinophil (serum eosinophil cationic protein [ECP]) activation during early airway response (EAR) and late airway response (LAR) to allergen inhalation in 24 asthmatic subjects. After EAR, 14 subjects showed significant LAR (FEV₁ fall: 25%), while 10 subjects showed equivocal LAR (FEV₁ fall: 15–20%). A significant increase from baseline value was observed in plasma histamine and in serum NCA during both EAR and LAR, while serum ECP significantly increased only during LAR. The sensitivity of different markers to detect significant FEV₁ fall during EAR and LAR was low, except for NCA. Changes in blood mediators were similar in both groups with significant and equivocal LAR. There was a significant relationship between the increase in NCA during EAR and the severity of LAR. Stepwise regression between changes in different blood markers showed a significant relationship between histamine increase during EAR and ECP increase during LAR. Thus, serum NCA is a more sensitive marker of EAR and LAR than plasma histamine and serum ECP, and its increase during EAR seems predictive of the severity of the subsequent LAR.     

Immunology and immunopathology of trimellitic anhydride pulmonary reactions

Inhaled trimellitic anhydride (TMA) reacts with airway proteins to produce trimellityl (TM) proteins. The TM-proteins result in both systemic and local immune responses, of which various proteins present in the airway can be used for markers. Thus TM-human serum albumin (HSA), TM-IgG, and TM-IgA can be used as hapten-protein complexes for immunologic studies in sera of humans exposed to TMA by inhalation. Various immunologic assays have been established to measure antibodies against TM-proteins and have various purposes. With TM-HSA as a model antigen, total serum antibody may be measured by the ammonium sulfate technique of coprecipitation of TM-¹²⁵I HSA. By solid-phase radioimmunoassays, IgE, IgG, IgA, and IgM antibodies can be measured. Lymphocyte reactivity can be measured by ³H thymidine uptake of TM-protein-stimulated lymphocytes. Biologic effects of IgE antibody can be measured by allergy skin tests and leukocyte histamine release with TM-proteins such as TM-HSA. The reaction of TMA with proteins results in alteration of those proteins that include changes in charge and physical conformation, the latter resulting in an apparent change in molecular size. These changes may relate to the observations that human antibody is not merely directed against the hapten in the hapten-human protein complex but also against new antigenic determinants formed by the TM-protein complex. Correlations have been made with certain human immunologic responses and lung disease after TMA inhalation, as follows: IgE antibody against TM-proteins correlates with TMA-induced rhinitis, conjunctivitis, and asthma; high levels of total antibody, IgG, and IgA antibody appear to correlate with the late respiratory systemic syndrome, probably a variant of hypersensitivity pneumonitis; workers exposed to TMA fumes (rather than TMA powder) have the highest levels of antibody, and this may correlate with occurrence of the hemorrhagic pneumonitis seen in this group of workers; patients with no symptoms or mild irritative symptoms have the lowest or no antibody levels. The immunopathogenetic relationships may be better understood with the further development of animal models of TMA lung disease now available.     

Early- and late-phase bronchoconstriction, airway hyper-reactivity and cell influx into the lungs, after 5'-adenosine monophosphate inhalation: comparison with ovalbumin

Background Antigen inhalation in atopic asthmatic patients results in an early asthmatic response (EAR), accompanied by a late asthmatic response (LAR) in 60% of patients. Inhaled 5′‐adenosine monophosphate (5′‐AMP) causes immediate bronchoconstriction in asthmatics but not in normal subjects. Objectives The aims of this study were to investigate whether 5′‐AMP can produce a LAR, airway hyper‐reactivity (AHR) and cell influx to the lungs, in a sensitized guinea‐pig model of asthma, and to compare with the profile of activity after ovalbumin (OVA) inhalation. Methods Airway responses to inhaled OVA (10 μg/mL) and 5′‐AMP (3 and 300 mm ) of actively sensitized, conscious guinea‐pigs were determined by whole body plethysmography as the change in specific airway conductance (sG_aw). Inhaled histamine (1 mm ) was used to investigate AHR, and cell influx was determined by bronchoalveolar lavage (BAL). Results Exposure to OVA revealed an EAR, and LAR at 6 h post‐challenge. AHR to histamine occurred 24 h after challenge together with a significant increase in total and differential (eosinophils and macrophages) cell counts. Low dose 5′‐AMP (3 mm ) produced an EAR, LAR at 6 h after challenge, and AHR to histamine 12 h post‐challenge. No AHR occurred 24 h after inhalation. Total and macrophage cell counts were increased significantly 6, 12 and 24 h after exposure. Bronchodilatation followed high dose 5′‐AMP (300 mm ), followed by a LAR at 6 h. AHR to histamine occurred 12 h after challenge, but not at 24 h. A significant increase in total and differential (eosinophils and macrophages) cell counts occurred 6, 12 and 24 h post‐exposure. No changes were observed in non‐sensitized guinea‐pigs. Conclusion OVA challenge revealed an EAR, LAR, cell influx and AHR in a guinea‐pig model of asthma. This study demonstrated for the first time that a LAR and AHR to histamine can be revealed following 5′‐AMP inhalation, in sensitized but not unsensitized guinea‐pigs. Cell influx at 6, 12 and 24 h post‐challenge suggests that it may be associated with the LAR and AHR.     

Prediction of late asthmatic responses to inhaled allergen

Relationships between cutaneous and bronchial responses to allergen were examined in nineteen atopic asthmatics. Allergen inhalation tests elicited an isolated early asthmatic response (EAR) in ten subjects and a dual asthmatic response (DAR) in nine subjects. Ragweed IgE RAST, performed with the sera of those patients tested with ragweed antigen, yielded higher values in all but one patient who experienced DAR than any of the patients with EAR. In one patient with annual symptoms in the ragweed season, positive skin tests with ragweed antigen and DAR to inhaled ragweed extracts, the IgE RAST was entirely negative and the serum IgE concentration was low. Dilutions of the allergen used in each individual for inhalation were also used in skin-prick tests. Early cutaneous allergic response (ECAR) mean wheal diameters were obtained at 10 min and late cutaneous allergic response (LCAR) mean diameters at 6-8 hr. Early asthmatic response (EAR) subjects differed modestly from DAR subjects in the relationships between ECAR and LCAR; in the EAR group, a significantly larger wheal diameter (P < 0.01) was required before an LCAR ensued, however there was some overlap. Once LCAR developed, there was no difference between EAR and DAR groups in the magnitude of the LCAR. There was a trend (not significant) towards a requirement for a higher antigen concentration in the EAR group to elicit an LCAR. In conclusion, correlates of an isolated EAR from inhaled antigen include: (i) a low positive IgE RAST result with the antigen, (ii) ECAR 6 mm or greater with the antigen which does not proceed to a LCAR, and (iii) a high concentration of antigen is needed in skin tests to elicit an LCAR. Correlates of a DAR include:(i) a high IgE RAST result with the antigen, (ii) an ECAR wheal diameter less than 5 mm with the antigen proceeds to a LCAR, and (iii) a low antigen concentration in skin tests elicits an LCAR. The observed correspondence between the tendency to late skin and late airway responses is evidence of a common immunologic basis.     

Inhibition of mast cell tryptase by inhaled APC 366 attenuates allergen-induced late-phase airway obstruction in asthma

BACKGROUND: APC 366, a selective inhibitor of mast cell tryptase, has been shown to inhibit antigen-induced early asthmatic response (EAR), late asthmatic response (LAR), and bronchial hyperresponsiveness (BHR) in a sheep model of allergic asthma. OBJECTIVE: The purpose of this study was to investigate the effects of APC 366 on antigen-induced EAR, LAR, and BHR in mild atopic asthmatics not on any anti-inflammatory therapy. METHODS: Sixteen mild atopic asthmatics, each with a demonstrable antigen-induced EAR, LAR, and BHR to histamine, were recruited into this randomized, double-blinded, crossover study. APC 366 (5 mg)/placebo was administered by aerosol inhalation 3 times per day on treatment days 1 through 4. Allergen challenge was carried out on day 4. Histamine challenge was performed the following morning, 1 hour after final dosing. RESULTS: Subjects were shown to have a significantly smaller overall mean area under the curve for the LAR (P =.012) and mean maximum fall in FEV(1) for the LAR (P =.007) after pretreatment with APC 366 in comparison with placebo. No significant effects on BHR were demonstrable. Although the EAR was reduced by 18% after treatment with APC 366 in comparison with placebo, this was not statistically significant. CONCLUSION: Short-term repeated administration of APC 366 significantly reduced the magnitude of antigen-induced LAR in atopic asthmatics, which supports the role of mast cell tryptase in the pathophysiology of the LAR.     

Effect of a single dose of the selectin inhibitor TBC1269 on early and late asthmatic responses

BACKGROUND : Selectins participate in the initial phase of leucocyte migration from circulation to inflamed tissues and may play a role in inflammatory cellular influx into airways in asthma. In the sheep asthma model, TBC1269, a pan-selectin antagonist, reduced late allergen response by 74%. OBJECTIVE : To determine whether a single dose of TBC1269 inhibits early (EAR) and late (LAR) asthmatic responses, and whether it inhibits sputum leucocyte influx after inhalation allergen challenge in atopic asthmatic subjects treated with bronchodilators only. METHODS : Twenty-one asthmatic subjects (mean+/-SD, age=32.5+/-6.7 years, 8 males, FEV1 percent predicted=84+/-15%) with known late asthmatic response based on a screening inhalation allergen challenge were randomly assigned to receive intravenous treatment with either placebo (n=11) or TBC1269 (n=10, 30 mg/kg) infused over 15 min immediately prior to a second (post-treatment) allergen challenge at least 4 weeks after the screening challenge. After each challenge, EAR and LAR were monitored for 7 h. In addition, sputum was induced 1 day before and 1 day after each allergen challenge. RESULTS : TBC1269 did not attenuate the EAR compared with placebo (largest fall in FEV1 within 1 h of 34.1+/-13.9% vs. 31.8+/-12.2% for TBC1269 and placebo groups respectively, P=0.61) or the LAR (largest fall in FEV1 between 3 and 7 h of 39.3+/-15.3% vs. 32.6+/-13.8%, P=0.24). TBC1269 had only minor effects on allergen-induced sputum eosinophilia. CONCLUSION : We conclude that TBC1269 administered before allergen challenge as a single intravenous dose does not attenuate early or late asthmatic responses to allergen in asthmatic subjects.     

The effect of IVX-0142, a heparin-derived hypersulfated disaccharide, on the allergic airway responses in asthma

Background:  IVX-0142 is a heparin-derived hypersulfated disaccharide devoid of anticoagulant activity while possessing anti-allergic and anti-inflammatory activity in preclinical studies. In a proof-of-concept study, the allergen inhalation challenge model was used to investigate the effect of IVX-0142 in mild atopic asthma.
Methods:  Nineteen subjects, not on controller medications, were randomized to an evaluator-blind, placebo-controlled, cross-over study. The effect of a single nebulized dose of IVX-0142 (80 mg) or placebo administered 30 min prior to allergen inhalation was evaluated on the allergic airway responses, airway responsiveness, and airway inflammation.
Results:  When compared with placebo, 14 and 13 subjects experienced a relatively smaller maximum fall in forced expiratory volume in 1 s (maxFEV₁%) for the early airway response (EAR) and late airway response (LAR) with IVX-0142, respectively ( P  < 0.01). The degree of attenuation in the EAR [maxFEV₁% (mean ± SE) 26.5 ± 2.8% vs placebo 31.0 ± 2.8%, P  = 0.059] and LAR (15.6 ± 2.9% vs placebo 19.0 ± 2.9%, P  = 0.24) with IVX-0142, however, was small and did not reach statistical significance compared with placebo. Similarly, a trend in the attenuation of allergen-induced increase in the absolute sputum cell counts was also observed. No difference in the allergen-induced increase in airway hyper-responsiveness and exhaled nitric oxide was noticed.
Conclusions:  The majority of mild atopic asthmatics demonstrated a reduction in the EAR and LAR to IVX-0142. However, the treatment effect observed with a single prechallenge dose of IVX-0142 was small and heterogeneous. The potential anti-allergic and anti-inflammatory effects using multiple higher doses need to be evaluated.     

Inhalation exposure of mice to trimellitic anhydride induces both IgG and IgE anti-hapten antibody

The development of antibody responses resulting from inhalation exposure to chemical allergens has been studied in mice. Inhalation exposure of BALB/c mice to atmospheres containing approximately 5 mg/m3 of the respiratory allergen trimellitic anhydride (TMA) resulted in the appearance of both serum IgG and IgE anti-hapten antibody. IgE anti-TMA was first detectable 2-3 weeks following the initiation of exposure and was still present at 6 weeks. Under the same conditions of exposure, 2,4-dinitrochlorobenzene (DNCB), a contact allergen which apparently lacks the capacity for respiratory sensitization, failed to elicit detectable amounts of anti-dinitrophenol (DNP) antibody. Exposure to increased concentrations of atmospheric DNCB (15 mg/m3) did, however, result in an IgG anti-DNP response but not in IgE antibody. These data demonstrate firstly, that atmospheres containing low molecular weight respiratory allergens can initiate specific IgE responses in mice, and secondly, that inhaled chemicals may differ in their ability to induce IgE antibody.     

Changes in serum haptoglobin level after allergen challenge test in asthmatic children

Bronchial asthma is characterized by airway inflammation, which underlies the phenomenon of bronchial hyperresponsiveness. Previous studies have shown that this correlates with the serum concentration of haptoglobin. The occurrence of the late asthmatic response (LAR) after an allergen challenge test is associated with airway inflammation. The objectives of this study were to examine serum levels of haptoglobin during the 24 h after allergen challenge and to compare changes between the subjects with and without LAR. We studied two groups of children with perennial asthma who developed the early asthmatic response (EAR) only (group 1: n = 14), and EAR but also LAR (group II: n = 14) after an allergen (Dermatophagoides pteronyssinus) challenge test. Serum concentrations of haptoglobin were measured at baseline, at EAR, and at 2 h (recovery), 8 h (LAR), and 24 h after the challenge. Baseline levels were similar in the two groups (group I: 128±57 mg/dl: group II: 129±50 mg/dl). In group I, there was no significant change in the level at any time point; in contrast, the subjects in group II showed a relative fall (92±40 mg/dl) at 8 h, and an increase (161±79 mg/dl) at 24 h after the challenge. Our results indicate that the serum concentration of haptoglobin decreases at the time of LAR and is subsequently replenished during the ensuing time. Although further studies are needed, we think that haptoglobin may be inflused into the airways during the inflammatory process associated with LAR, and that this may be followed by "overshooting" production.     

Inhibition of mite-induced immunoglobulin E synthesis, airway inflammation, and hyperreactivity by herbal medicine STA-1

The availability of STA-1 in suppressing allergen-induced immunoglobulin E (IgE) synthesis, airway inflammation and hyperreactivity in a murine model was investigated. The mice were intraperitoneally sensitized with Dermatophagoides pteronyssinus group 5 allergen (Der p 5) and orally treated with 300 mg/kg of STA-1 every other day for 14 days. The Der p 5-specific immunologic responses including changes of specific immunoglobulin G and E, cells in the broncholarvage fluid, and airway hyperreactivity were measured when mice received inhalation challenge with Der p 5 after sensitization for 21 days. By comparing with sham-treated groups, the synthesis of Der p 5-specific IgE was downregulated while the influx of eosinophils and neutrophils in the airway were remarkably reduced. In addition, Der p 5-induced airway hyperreactivity also was significantly eliminated by STA-1 treatment. These results showed that STA-1 could effectively suppress the Der p 5-induced allergic reactions, and the availability of STA-1 for the treatment of allergic asthma was demonstrated in this study.     

The effect of a single inhaled dose of a VLA-4 antagonist on allergen-induced airway responses and airway inflammation in patients with asthma

Adhesion molecule very late antigen-4 (VLA-4) is implicated in the recruitment and activation of inflammatory cells in asthma, including eosinophils, T cells and mast cells. VLA-4 antagonists have been proposed as a new anti-inflammatory treatment modality for asthma. Therefore, we investigated whether a single inhaled dose of VLA-4 antagonist GW559090X could protect against allergen-induced changes in airway responses and airway inflammation in patients with asthma. We performed a randomized, double-blind, three-way crossover study with single inhaled doses of 3 mg of GW559090X, 500 microg of fluticasone propionate (FP) or placebo in 15 patients with mild intermittent asthma, controlled with short-acting beta(2)-agonists only. All patients developed a late asthmatic response (LAR) after allergen inhalation during screening. Study medication was administered 30 min prior to allergen challenge. Pre-dose and 24 h post-dose PC20 methacholine and levels of exhaled nitric oxide (eNO) were determined. At the given dose, VLA-4 antagonist GW559090X did not attenuate the early asthmatic response (EAR) when compared with placebo: mean AUC0-2 h(+/-SEM) (%fall h): 27.2+/-3.7 and 21.9+/-3.0 respectively (P=0.33); nor the LAR: mean AUC3-8 h(+/-SEM) (%fall h): 98.8+/-12.9 and 94.8+/-6.8 respectively (P=0.84). However, pretreatment with FP did attenuate both EAR and LAR when compared with placebo: mean AUC0-2 h11.6+/-3.3 (P=0.024) and mean AUC3-8 h 6.3+/-7.6 (P<0.001). None of these treatments had an effect on allergen-induced changes in airway hyper-responsiveness or eNO levels. These findings suggest that VLA-4 may not play a major role in allergen-induced airway responses and inflammation in asthma.     

Blockade of CTLA-4 promotes airway inflammation in naive mice exposed to aerosolized allergen but fails to prevent inhalation tolerance

In subjects not developing allergy, inhalation of nonpathogenic protein antigens causes no harm and is associated with tolerance induction. Repeated exposure to aerosolized ovalbumin (OVA) likewise does not evoke airway inflammation and induces inhalation tolerance in experimental animals. The present study explored the role of the inhibitory T-cell receptor CTLA-4, in preventing inflammation and in establishing inhalation tolerance in response to a protein antigen. Naive BALB/c mice were injected intraperitoneally with anti-CTLA-4 monoclonal antibody or control immunoglobulin G (IgG) and exposed daily to aerosolized saline or OVA over 10 or 20 consecutive days. OVA-specific IgE levels and the inflammatory response in airway tissues were assessed 2 days after last exposure. The OVA-specific IgE response was also evaluated in mice subjected to a subsequent immunogenic OVA challenge 18 days after last aerosol exposure. Additional mice were made tolerant by 10 days of OVA aerosol exposure and were then subjected to an immunogenic OVA challenge combined with CTLA-4 blockade or control IgG treatment. Repeated inhalation of aerosolized OVA alone did not cause a pulmonary inflammatory response. In contrast, 10 days of OVA exposure combined with blockade of CTLA-4 led to development of eosinophilic lung infiltrates, BAL fluid eosinophilia, goblet cell hyperplasia and increased OVA-specific IgE. By 20 days of OVA exposure and blockade of CTLA-4, the inflammatory response remained. Mice exposed to aerosolized OVA for 10 days exhibited greatly reduced OVA-specific IgE responses to subsequent immunogenic OVA challenge. Blockade of CTLA-4 during the period of OVA aerosol exposure did not prevent this suppression of the OVA-specific IgE response. Neither did blockade of CTLA-4 during immunogenic OVA challenge alter the allergen-specific IgE response. Our results indicate that in vivo blockade of CTLA-4 modulates the initial immune response to a protein antigen allowing the development of allergen-induced airway inflammation in naive mice. However, this initial exaggerated immune response is followed by the induction of inhalation tolerance, demonstrating that CTLA-4 signalling is not decisive in this process. Our findings also show that once inhalation tolerance is established it may not be disrupted by blockade of CTLA-4.     

A comparison of the effects of oral cetirizine and inhaled beclomethasone on early and late asthmatic responses to allergen and the associated increase in airways hyperresponsiveness

Background Cetirizine is a non-sedating H₁ antihistamine which is effective in the treatment of allergic rhinitis and urticaria. It inhibits eosinophil and basophil chemotaxis in late cutaneous allergic reactions in skin windows. Its effect on early (EAR) and late asthmatic reactions (LAR) is less certain. Methods We examined the effect on EAR and LAR of 3 days treatment with oral cetirizine (15mg twice daily) compared with a single dose of inhaled beclomethasone 10min prior to allergen challenge in a placebo-controlled (oral and inhaled) doubleblind cross-over design with three treatment arms separated by 14 days. Results Cetirizine did not significantly inhibit either the EAR or LAR documented by maximum percentage fall in FEV₁ (0-3 and 6-9h) or as area under the curve (AUC between 0 and 3 and 6–9 h), Beclomethasone inhibited the LAR compared with placebo (P = 0.02) when expressed as AUC (6–9h). This did not quite reach statistical significance (P = 0.06) when expressed as maximal percentage late fall in FEV₁ between 6 and 9h. A greater than twofold increase in airways responsiveness to methacholine was observed 3h after challenge which was significantly reduced by beclomethasone compared with placebo (P < 0.02) and cetirizine (P < 0.05). The data suggest that oral cetirizine does not significantly inhibit either the EAR or LAR. Beclomethasone inhibited both the early increase in airways responsiveness and the subsequent LAR. Our study also confirms the view that early increases in airway responsiveness precede the late response and suggests that these associated events are not dissociable by the pharmacological treatments employed in this study.     

Inhalation exposure to respiratory sensitising chemicals down-regulates guinea pig IgE and pulmonary responses

Inhalation exposure of the guinea pig to the respiratory sensitising chemicals trimellitic anhydride (TMA) or diphenylmethane di-isocyanate down-regulated the IgE antibody response to subsequent systemic challenge with alum-precipitated hapten-protein conjugate. The suppression was isotype and hapten specific, challenge with unrelated hapten-protein conjugate resulting in high-titre IgE and IgGl antibody responses. Preliminary results indicate that the down-regulation of the IgE response to TMA markedly reduced the capacity of the animals to undergo a bronchoconstriction response following challenge with an aerosol of TMA, suggesting that the initial route of exposure may have profound effects upon the development of occupational respiratory allergy.