Positive immediate skin tests in cystic fibrosis: a possible role for Pseudomonas infection

Bacterial Quorum Sensing Molecules Promote Allergic Airway Inflammation by Activating the Retinoic Acid Response

IgE and IgG1 production in the type 2 immune response is the characteristic feature of an allergic reaction. However, whether bacterial molecules modulate IgE and IgG1 production remains obscure. Here, we demonstrate that the bacterial quorum sensing molecules acyl homoserine lactones (AHLs) induce IgE and IgG1 production by activating the RARE (retinoic acid response element) response in dendritic cells (DCs) in vivo. DC-specific knockout of the retinoic acid transcriptional factor Rara diminished the AHL-stimulated type 2 immune response in vitro. AHLs altered DC phenotype, upregulated OX40L and IFN-I signature, and promoted T helper 2 cell differentiation in vitro. Finally, AHLs activated the RARE response by inhibiting AKT phosphorylation in vitro, as the AKT agonists IGF-1 and PDGF abolished the effect of AHLs on the RARE response. This study demonstrates a mechanism by which AHLs drive allergic airway inflammation through activating retinoic acid signaling in DCs.

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Acyl homoserine lactones (AHLs) exacerbate allergic airway inflammation

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AHLs induce IgE and IgG1 production

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AHLs activate the RARE response in dendritic cells

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AHLs inhibit AKT phosphorylation

Prevalence of Aspergillus sensitization and allergic bronchopulmonary aspergillosis in cystic fibrosis: systematic review and meta-analysis

BACKGROUND

The prevalence of Aspergillus sensitization (AS) and allergic bronchopulmonary aspergillosis (ABPA) in cystic fibrosis (CF) has been varyingly reported. The aim of this systematic review was to estimate the overall prevalence of AS/ABPA in CF.

METHODS

We searched the PubMed and EmBase databases for studies reporting the prevalence of AS/ABPA in CF. We calculated the proportion with 95% confidence interval (CI) to assess the prevalence of AS and ABPA in the individual studies and then pooled the results using a random effects model. Statistical heterogeneity was assessed using the I2 test while publication bias was assessed using both graphical and statistical methods.

RESULTS

Our search yielded 64 eligible studies. The pooled prevalence of AS was 39.1% (95% CI: 33.3-45.1) and was higher with skin test compared to specific IgE (43.8% vs. 32.8%, P = 0.002); however, the prevalence did not vary with the type of skin test used (intradermal or percutaneous). The prevalence of ABPA was 8.9% (95% CI: 7.4-10.7) and was higher in adults as compared to children (10.1% vs. 8.9%, P < 0.0001). There was a wide variation in the criteria used for diagnosing ABPA. Almost 50% (12/23) of the publications after 2004 used criteria other than the CF foundation criteria for diagnosing ABPA. There was significant statistical heterogeneity and evidence of publication bias.

CONCLUSIONS

There is a high prevalence of AS and ABPA in patients with CF. Despite six decades of research, there is still a need to adopt uniform methodology and criteria for the diagnosis of AS/ABPA.

The prevalence of cutaneous hypersensitivity and its relationship to Pseudomonas colonization and outcome in cystic fibrosis

Forty-seven patients with cystic fibrosis (CF) studied in 1977 have been followed up and reviewed, with respect to the development of immediate cutaneous hypersensitivity to Aspergillus fumigatus and other allergens, and the date of Pseudomonas aeruginosa colonization. The prevalence of cutaneous hypersensitivity to inhaled allergens in CF increases with longer allergen exposure, to the extent that the CF patients develop a prevalence of atopy greater than normal controls. Allergen-sensitive patients were found to develop Pseudomonas colonization later, but to have a shorter survival subsequently; there was no relationship between skin tests and overall survival.

The relationship between atopy and cystic fibrosis

The incidence and clinical significance of allergy in cystic fibrosis have been discussed. There is little evidence that the high prevalence of positive allergy skin tests in CF is a clinical manifestation of a hypersensitivity lung disease complicating the primary pulmonary disorder, except in the special case of allergic bronchopulmonary aspergillosis. The lung disease of CF appears to be caused by excessive bronchial secretions and recurrent infection that are the result of abnormal ion transport across the apical membrane of the respiratory epithelial cell. There are two important questions concerning the allergic reactions: Are they clinically significant, and, why do they occur? The former question is partly resolved by the data presented, although well-controlled studies of intervention would help to resolve it further. The cause of these reactions, which occur particularly in relationship to the mold Aspergillus fumigatus, is unknown but the author is inclined to the view that they are the result of recurrent infection that induces heightened immunologic reactivity to inhaled allergens. The significance of AF may be simply that this mold has a "predilection for diseased airways" or may be more complex; for example, owing to abnormal ion composition in respiratory secretions, abnormal lectin expression by CF respiratory epithelial cells, or selective filtration by the airways based on particle size.

Atopy, immunological changes, and respiratory function in bronchiectasis

Cystic fibrosis has been reported to be associated with an increased prevalence of atopy and reversible airways obstruction. To determine whether such features can also result from other chronic suppurative lung infections, we studied 23 patients with proved bronchiectasis, and 23 age and sex matched normal controls. A personal or family history of atopy was reported with equal frequency in the two groups. Although the groups displayed a similar prevalence of positive immediate hypersensitivity skinprick test responses, the positive patients reacted to more antigens (p less than 0.05) and had larger weal diameters (p less than 0.01) than the positive controls. Other indices, such as blood eosinophil counts and serum IgE, did not differ significantly. Serum concentrations of immunoglobulins G, A, and M and of the four IgG subclasses tended to be higher in patients than controls, but only in the case of IgA (p less than 0.01) was this difference significant. No case of IgG subclass deficiency was noted. The patients displayed significant airflow obstruction, the mean basal one second forced expiratory volume (FEV1), forced vital capacity (FVC), and peak expiratory flow rate (PEFR) being 67%, 77%, and 67% of their predicted values. There was evidence of a significant reversible obstructive component in that FEV1 or PEFR or both increased by 15% or more in nine of the 23 patients after inhalation of fenoterol, the mean increases in FEV1, FVC, and PEFR for the whole group being 9.5%, 11%, and 16.9%. These results indicate that while bronchiectasis provokes a hyperimmune response it differs from cystic fibrosis in that there is no significant increase in the prevalence of atopy. The finding of reversible airways obstruction, however, suggests that bronchodilators may be useful adjuncts to treatment.