Allergen-induced bronchial inflammation is associated with decreased levels of surfactant proteins A and D in a murine model of asthma

Background Increasing evidence suggests that pulmonary surfactant protein A (SP‐A) and D (SP‐D) participate in the lung defence against pathogens. However, the role of surfactant proteins in the pathogenesis of allergen‐induced airway inflammation has not been elucidated. In this study we examined the levels and distributions of SP‐A and SP‐D in a dust mite (Dermatophagoides pteronyssinus, Der p) allergen‐induced murine model of asthma. Methods The concentration of SP‐A and SP‐D in the bronchoalveolar lavage fluid (BALF) and the distribution of surfactant proteins in the lung were assayed by ELISA and immunohistochemistry methods, respectively. The effect of surfactant proteins on allergen‐induced pulmonary lymphocyte proliferation was also studied. Results We demonstrated that there were marked reductions of SP‐A and SP‐D levels in the BALF of Der p‐sensitized BALB/c mice at 48–72 h after allergen challenge (AC). Both purified SP‐A and SP‐D were able to suppress, in a dose dependent manner, Der p‐stimulated intrapulmonary lymphocyte proliferation of naïve mice with saline or allergen challenge, or of Der p‐sensitized mice with saline challenge. On the contrary, this suppressive effect was mild (< 9%) on lymphocytes from sensitized mice after AC. Conclusion These results indicated the involvement of pulmonary surfactant proteins in the allergic bronchial inflammation of sensitized mice.     

Maternal tolerance achieved during pregnancy is transferred to the offspring via breast milk and persistently protects the offspring from allergic asthma

Background Maternal, more than paternal, asthma is a risk factor for the development of asthma in children. Recently, epidemiologic studies have shown that environmental exposures during pregnancy might influence the development of childhood asthma and allergies. Objective The aim of the present study was to investigate whether the induction of tolerance against a specific antigen during pregnancy prevents in the offspring the development of allergic asthma in response to this antigen. Methods Balb/c mice were orally tolerized with ovalbumin (OVA) during pregnancy. The offspring of tolerized and naïve mothers were immunized with OVA at 6 weeks and 4 months of age and analysed in our murine asthma model. Results While the offspring of naïve mice developed increased AHR, eosinophilic airway inflammation, T‐helper type 2 cytokine production and high serum IgE levels in response to OVA sensitization, the offspring of tolerized mice were almost completely protected from asthma, even when immunized as late as 4 months after birth. Breastfeeding was crucial for protection because tolerance was only observed when the offspring were nursed by their own mothers and not when nursed by naïve wet‐nurses. Allergen‐specific IgG₁ antibodies were exclusively increased in the breast milk of tolerant mothers and serum of protected pups, indirectly supporting its important role in tolerance transfer from the mother to the offspring. Sensitization of the F1 generation from OVA‐tolerized mothers with a heterologous allergen enhanced the immune response to this antigen. Conclusion Our results demonstrate that mucosal allergen contact during pregnancy modifies the asthma and allergy risk of the offspring mediated via breast milk. This observation may suggest that the time window for primary prevention strategies starts even before early childhood during pregnancy.     

Mucosal and systemic inflammatory changes in allergic rhinitis and asthma: a comparison between upper and lower airways

BACKGROUND: Local airway inflammation and airway remodelling are considered important in the clinical expression of allergic asthma. OBJECTIVE: The aim of this study was to compare airway inflammation and remodelling in nasal and bronchial mucosa of subjects with allergic rhinitis with or without asthma. METHODS: Four experimental groups were formed: allergic asthma and rhinitis (n = 19); allergic rhinitis, no asthma (n = 18); atopic subjects, no asthma, no rhinitis (n = 8) and non-allergic healthy control subjects (n = 16). Blood samples, nasal and bronchial biopsy specimens were collected during stable disease. Immunohistochemistry was performed for eosinophils (MBP), mast cells (CD117) and vascular endothelium (CD31). Epithelial loss, reticular basement membrane (RBM) thickness and subepithelial vascularity was assessed with a computer-assisted image analysis system. RESULTS: In nasal and bronchial mucosa, numbers of eosinophils were significantly higher in rhinitis patients with and without asthma than in asymptomatic atopics (P < 0.05) and controls (P < or = 0.01). In bronchial mucosa, the RBM was significantly thickened in rhinitis patients with and without asthma compared to asymptomatic atopics (P < 0.05) and controls (P < 0.01), while in nasal mucosa no differences were seen. Patients with asthma and rhinitis had increased numbers of blood eosinophils (P = 0.05) and skin test reactivity (P = 0.01) compared to patients with rhinitis only. No significant differences could be found between the investigated groups with respect to serum IL-5 and eotaxin levels, the number of mucosal mast cells and the degree of epithelial loss and subepithelial vascularity. Epithelial desquamation was significantly increased in the bronchial mucosa compared to nasal mucosa, not only in asthmatics (P < 0.001), but also in atopics without asthma and rhinitis (P = 0.02). CONCLUSIONS: This study shows that allergic inflammation, increased basement membrane thickness and epithelial desquamation are present in the lower airways of atopic subjects, even before the onset of clinical symptoms. Despite the presence of inflammatory cells, no structural changes could be assessed in nasal mucosa of allergic patients.     

Airway inflammation and eotaxin in exhaled breath condensate of patients with severe persistent allergic asthma during omalizumab therapy

PurposeThe central role of IgE in allergic inflammation in asthma has provided a rationale for the development of omalizumab, the humanized monoclonal anti-IgE antibody. The aim of the study was to determine the effect of omalizumab treatment on changes in airway inflammatory process and eotaxin in exhaled breath condensate in patients with persistent severe allergic asthma.Material and MethodsThe study was performed on a group of 19 patients with severe persistent allergic asthma treated with conventional therapy (according to GINA 2006) and with or without omalizumab (9 vs 10 patients). Eotaxin in exhaled breath condensate, exhaled nitric oxide, blood eosinophil count and serum ECP were measured before and after 16 weeks of therapy.ResultsIn the group treated with omalizumab, a statistically significant decrease in the concentrations of eotaxin in EBC, FENO, serum ECP, and blood eosinophil count after 16 weeks of treatment was observed. Statistically significant correlations were revealed between the decrease in eotaxin and the decrease in FENO, serum ECP and blood eosinophil count after omalizumab therapy.ConclusionsDownregulation of eotaxin expression in the airways through limitation of eosinophilic inflammation could be essential in the beneficial effect of anti-IgE therapy with omalizumab in asthma patients.     

Maternal vitamin D intake during pregnancy is inversely associated with asthma and allergic rhinitis in 5-year-old children

Background Vitamin D is known to have a number of immunological effects and it may play a role in preventing allergic diseases.
Objectives To study the effect of maternal intake of vitamin D during pregnancy on the emergence of asthma, allergic rhinitis (AR), and atopic eczema by the age of 5 years in children with HLA-DQB1-conferred susceptibility for type 1 diabetes.
Methods Children (1669) participating in the population-based birth cohort study were followed for asthma, AR, and atopic eczema assessed by validated questionnaire at 5 years. Maternal diet was assessed by a food-frequency questionnaire.
Results The mean maternal intake of vitamin D was 5.1 (SD 2.6) μg from food and 1.4 (2.6) μg from supplements. Only 32% of the women were taking vitamin D supplements. When adjusted for potential confounders, maternal intake of vitamin D from food was negatively related to risk of asthma [hazard ratio (HR) 0.80; 95% confidence interval (CI) 0.64–0.99] and AR [HR 0.85; 95% CI 0.75–0.97]. Vitamin D supplements alone were not associated with any outcome. Adjustment for maternal intake of other dietary factors did not change the results.
Conclusion Maternal vitamin D intake from foods during pregnancy may be negatively associated with risk of asthma and AR in childhood.     

The airway inflammatory response in allergic asthma and its relationship to clinical disease

Endobronchial biopsy and lavage studies have revealed the presence of mast cell, eosinophil, T-lymphocyte and epithelial cell activation in asthma, along with the structural changes of tissue eosinophil infiltration, loss of superficial columnar ciliated epithelial cells and enhanced collagen deposition in the laminar reticularis. As these cellular and structural changes underlie the clinical features of asthma, i.e., symptom expression, variable airflow obstruction and bronchial hyperresponsiveness, an understanding of their induction and regulation is essential to the understanding of the asthmatic process. The acute airway response to allergen has been studied by the technique of local endobronchial allergen challenge with direct airway sampling in asthma. These studies identify allergen-mast cell interaction as the initial airway event, with mediator release inducing bronchoconstriction and enhancing vascular permeability. As preformed cytokines are present in mast cells, cytokine release from this cell population is likely to initiate the process of endothelial cell activation, with upregulation of cell adhesion molecules, and tissue cell recruitment. Subsequent cytokine elaboration from airway macrophages and T-lymphocytes will perpetuate this response while in chronic clinical disease T-lymphocytes, mast cells, matrix tissue, epithelial cells and eosinophils themselves are all likely to contribute to the cytokine pool within the airways and thus to the regulation of inflammatory cell migration and activation.     

Variation in the TEK gene is not associated with asthma but with allergic conjunctivitis

The Tie2 receptor is an important player in angiogenesis. The Tie2 mRNA and protein are abundantly expressed in the lungs and the associated pathway also has an important role in the development and function of the eye. Tie2 is encoded by the TEK gene in humans. Recently, variations in the TEK gene have been found associated with asthma. The objective of the present study was to investigate whether variations in the TEK gene influenced the susceptibility to pediatric asthma and/or associated phenotypes like GINA status, viral‐ or exercise‐induced asthma, allergic asthma, indoor, outdoor, inhalative allergies, IgE and eosonophil levels, allergic rhinitis and allergic conjunctivitis. Three single nucleotide polymorphisms (SNPs, rs3780315, rs581724 and rs7876024) in the TEK gene were genotyped in 1189 unrelated individuals, out of which 435 were asthmatic children and 754 healthy controls. Different types of asthma, allergies and co‐morbidities were defined in 320 patients. Among the fully phenotyped 320 asthmatic patients 178 (55.6%) also had allergic rhinitis and 100 (31.3%) had conjunctivitis. Among the rhinitis patients 98 (55.1%) also had conjunctivitis. Two patients had conjunctivitis without rhinitis. The genotyped SNPs showed no association with asthma. However, SNP rs581724 was significantly associated with allergic conjunctivitis in a recessive way (p=0.007; OR=2.3 (1.3‐4.4)) within the asthmatic population. The risk remained significant when the whole population (asthmatics and healthy controls) was included in the calculation (p = 0.003; OR = 2.1 (1.3‐3.6)). The minor allele of the rs581724 SNP which is associated with the increased risk to conjunctivitis is also associated with reduced Tie2 expression. There was a significant association between SNP rs581724 and the occurrence of allergic conjunctivitis in asthmatic children. If additional studies can confirm the role of the Tie2 pathway in allergic conjunctivitis, it can be a potential novel therapeutic target in the disease.     

Add-on omalizumab improves day-to-day symptoms in inadequately controlled severe persistent allergic asthma

Background:  Omalizumab is efficacious in the treatment of moderate-to-severe and severe persistent allergic (immunoglobulin E-mediated) asthma, reducing exacerbations, emergency visits and improving quality of life (QoL). However, as exacerbations are relatively infrequent, assessment of efficacy on day-to-day symptoms is warranted.
Aims:  To investigate the effect of add-on omalizumab on day-to-day symptoms, and how they correlate with QoL in severe persistent asthma.
Methods:  The correlation between asthma symptom scores and QoL [Asthma Quality of Life Questionnaire (AQLQ)] was assessed. Symptom-free days (total symptom score = 0) and symptom-controlled days (definition 1: total symptom score ≤1; and definition 2: morning peak expiratory flow ≥90% of baseline, daytime asthma score ≤1 and night-time asthma score = 0) were compared between the omalizumab-treated group, omalizumab responders and placebo.
Results:  Four hundred and nineteen patients (omalizumab, n  = 209; placebo, n  = 210) were included in the efficacy analyses, and 61% (118/195) of patients with response data were classified as responders. Total symptom score strongly correlated with AQLQ overall and symptom scores and individual domains. AQLQ overall score correlated well with symptom scores. Responders had significantly more symptom-free days than the omalizumab-treated and placebo groups (45.8%, 37.2% and 22.6% respectively), and more symptom-controlled days (definition 1: 56.1%, 47.9% and 35.3%, respectively, and definition 2: 50.8%, 43.9% and 28.0%, respectively).
Conclusions:  In patients with inadequately controlled severe persistent asthma, day-to-day symptoms correlate well with QoL. Add-on omalizumab significantly improves day-to-day symptoms compared with placebo. Further improvement in responders confirms the physician's assessment as a response measure.     

Prolonged allergen challenge in mice leads to persistent airway remodelling

BACKGROUND: Inflammatory infiltrates, airway hyper-responsiveness, goblet cell hyperplasia and subepithelial thickening are characteristic of chronic asthma. Current animal models of allergen-induced airway inflammation generally concentrate on the acute inflammation following allergen exposure and fail to mimic all of these features. OBJECTIVE: The aim of this study was to use a murine model of prolonged allergen-induced airway inflammation in order to characterize the cells and molecules involved in the ensuing airway remodelling. Moreover, we investigated whether remodelling persists in the absence of continued allergen challenge. METHODS: Acute pulmonary eosinophilia and airways hyper-reactivity were induced after six serial allergen challenges in sensitized mice (acute phase). Mice were subsequently challenged three times a week with ovalbumin (OVA) (chronic phase) up to day 55. To investigate the persistence of pathology, one group of mice were left for another 4 weeks without further allergen challenge (day 80). RESULTS: The extended OVA challenge protocol caused significant airway remodelling, which was absent in the acute phase. Specifically, remodelling was characterized by deposition of collagen as well as airway smooth muscle and goblet cell hyperplasia. Importantly, these airway changes, together with tissue eosinophilia were sustained in the absence of further allergen challenge. Examination of cytokines revealed a dramatic up-regulation of IL-4 and tumour growth factor-beta1 during the chronic phase. Interestingly, while IL-4 levels were significantly increased during the chronic phase, levels of IL-13 fell. Levels of the Th1-associated cytokine IFN-gamma also increased during the chronic phase. CONCLUSION: In conclusion, we have demonstrated that prolonged allergen challenge results in persistent airway wall remodelling.     

Nasal involvement in allergic asthma

Even since the late 19th century, a relationship has been suspected between upper airway disease and the subsequent development or aggravation of asthma symptoms. To date, it has been generally accepted that pathologic conditions of the upper airways, e.g. allergic rhinitis, chronic sinusitis and nasal polyposis, may influence the lower airways. However, the mechanisms underlying this relationship were, for a long time, poorly understood. Recently, evidence has been accumulating which indicates a systemic connection as one of the responsible mechanisms in nasobronchial crosstalk. In this review, the pathophysiologic and immunologic aspects of the interaction between upper and lower airways will be discussed.     

Effect of omalizumab treatment on peripheral eosinophil and T-lymphocyte function in patients with allergic asthma

BACKGROUND: Omalizumab is a recombinant monoclonal anti-IgE antibody with proven efficacy in allergic diseases and further anti-inflammatory potency in the treatment of asthma. OBJECTIVES: To explore the anti-inflammatory mechanism of omalizumab, we investigated the induction of immunologic changes leading to eosinophil apoptosis and examined T-lymphocyte cytokine profiles in patients with allergic asthma. METHODS: Nineteen patients with allergic asthma were enrolled and received omalizumab at a dose of at least 0.016 mg/kg/IgE (IU/mL) every 4 weeks. Peripheral eosinophils and T-lymphocyte cytokine profiles were evaluated by fluorescence-activated cell sorting before treatment (baseline), at 12 weeks of treatment, and 12 weeks after discontinuation of treatment with omalizumab or placebo. RESULTS: Markers of eosinophil apoptosis (Annexin V) were significantly increased in omalizumab recipients compared with placebo, whereas no changes in markers of necrosis (7-amino-actinomycin) or eosinophil activation CD69 or Fas receptor (CD95) were detected. GM-CSF+ lymphocytes were reduced in omalizumab recipients compared with placebo. Fewer IL-2+ and IL-13+ lymphocytes were evident in omalizumab recipients than in the placebo group. There were no significant differences in IL-5, IFN-gamma, or TNF-alpha between the omalizumab and placebo groups. CONCLUSION: These findings provide further evidence that omalizumab has additional anti-inflammatory activity demonstrated by induction of eosinophil apoptosis and downregulation of the inflammatory cytokines IL-2 and IL-13. Further studies are needed to determine the underlying mechanisms. CLINICAL IMPLICATIONS: These findings support the critical role of IgE in the regulation of inflammation in allergic asthma: influencing the inflammation is the key to control the more severe type of asthma.     

Exhaled nitric oxide identifies the persistent eosinophilic phenotype in severe refractory asthma

BACKGROUND: The fractional concentration of exhaled nitric oxide (FENO) is increased in asthma, correlates with eosinophilic inflammation, and decreases after steroid therapy. OBJECTIVE: We sought to examine whether persistent eosinophilia would be accompanied by an increased FENO level despite steroid therapy in patients with severe refractory asthma (SRA) as manifestations of steroid resistance. METHODS: Subjects with SRA, subjects with mild-moderate asthma, and healthy control subjects had FENO measured, followed by endobronchial biopsy and bronchoalveolar lavage. Tissue and bronchoalveolar lavage inflammatory cells were assessed for all subjects, and eosinophil status (EOS+/EOS-) was determined for subjects with SRA. RESULTS: Twenty-four subjects with SRA, 15 subjects with moderate-mild asthma, and 17 healthy control subjects were studied. Subjects with EOS+ SRA had significantly higher median FENO levels compared with levels in subjects with EOS- SRA (P = .0084) and all other groups. In subjects with SRA, FENO levels correlated with tissue eosinophils (r(s) = 0.54, P = .007), lymphocytes (r(s) = 0.40, P = .003), and mast cells (r(s) = 0.44, P = .05). FENO levels of greater than 72.9 ppb were associated with a sensitivity of 0.56 and a specificity of 1.0 for EOS+ status in subjects with SRA. CONCLUSION: FENO measurement identified the subgroup of subjects with SRA with persistent eosinophilia despite steroid therapy. Further studies are needed on the use of FENO to monitor response to therapy over time in subjects with SRA.     

Desloratadine reduces systemic allergic inflammation following nasal provocation in allergic rhinitis and asthma patients

BACKGROUND: Preclinical studies have demonstrated that some second-generation antihistamines have anti-inflammatory effects. It is not known whether these effects are also demonstrable in vivo. In this study we investigated the effect of treatment with desloratadine (DL) on systemic inflammation and on nasal and bronchial mucosal inflammation after nasal allergen provocation (NP) in subjects with grass-pollen-allergic rhinitis and asthma. METHODS: Twenty-six subjects with grass-pollen-allergic rhinitis and asthma were randomly allocated to 8 days of treatment with DL (n = 13) or placebo (n = 13) outside the grass pollen season. On day 7 they underwent nasal provocation with grass pollen allergen. Nasal and bronchial biopsies were taken for immunohistochemical evaluation, and blood samples were analysed. Rhinitis and asthma symptoms, peak nasal inspiratory flow and peak expiratory flow, were also measured at specified times. RESULTS: The number of circulating eosinophils decreased during DL treatment, and there was a reduced increase in circulating eosinophils after NP in these subjects. There was also a significant reduction in early bronchial clinical response. There was no significant lessening in the severity of the nasal symptoms. Nasal and bronchial mucosal inflammation parameters did not alter under DL treatment. CONCLUSION: These data suggest that treatment with DL reduces systemic eosinophilia and prevents the increase in circulating eosinophils after NP. DL also significantly reduces the early bronchial clinical response to NP. However, airway mucosal inflammation is not altered by 1 week of treatment.