Pathophysiology and management of pulmonary infections in cystic fibrosis

Gene delivery to human sweat glands: a model for cystic fibrosis gene therapy

Gene therapy vectors are mostly studied in cultured cells, rodents, and sometimes in non-human primates, but it is useful to test them in human tissue prior to clinical trials. In this study, we investigated the possibility of using human sweat glands as a model for testing cystic fibrosis (CF) gene therapy vectors. Human sweat glands are relatively easy to obtain from skin biopsy, and can be tested for CFTR function. Using patients' sweat glands could provide a safe model to study the efficacy of CF gene therapy. As the first step to explore using sweat glands as a model for CF gene therapy, we examined various ex vivo gene delivery methods for a helper-dependent adenovirus (HD-Ad) vector. Gene delivery to sweat glands in skin organ culture was studied by topical application, intradermal injection or submerged culture. We found that transduction efficiency can be enhanced by pretreating isolated sweat glands with dispase, which suggests that the basement membrane is a critical barrier to gene delivery by adenoviral vectors. Using this approach, we showed that Cftr could be efficiently delivered to and expressed by the epithelial cells of sweat glands with our helper-dependent adenoviral vector containing cytokeratin 18 regulatory elements. Based on this study we propose that sweat glands might be used as an alternative model to study CF gene therapy in humans.

Impact ofBurkholderia dolosaon Lung Function and Survival in Cystic Fibrosis

RATIONALE

Chronic infection with Burkholderia cepacia complex bacteria in cystic fibrosis is associated with accelerated decline in pulmonary function and increased mortality. Clinical implications of the recently characterized genomovar VI, B. dolosa, are unknown.

OBJECTIVES

Characterization of impact of B. dolosa on pulmonary function and mortality in cystic fibrosis.

METHODS

We compared patients chronically infected with B. dolosa (n = 31) with unmatched patients with B. multivorans (n = 24) and with age- and sex-matched control subjects without Burkholderia species (n = 58). We analyzed rates of pulmonary function decline (% predicted FEV(1)) using a random effects model assuming segmented linear trends. All available FEV(1) measurements from 5 yr (median, 4.8) before until 2.5 yr (median, 1.5) after the first positive culture for Burkholderia (reference date) were analyzed. Survival was compared using the Kaplan-Meier method and proportional hazards model.

MEASUREMENTS AND MAIN RESULTS

Baseline FEV(1) and rate of decline were similar in the cohorts. Decline in FEV(1) after the reference date accelerated in patients with B. dolosa (-2.3 percentage points/yr pre vs. -7.1 post, p = 0.002), but was unchanged in the B. multivorans and control patients (-2.3 vs. -0.8 post, p = 0.38, and -2.1 pre vs. -0.5 post, p = 0.20, respectively). The probability of dying within 18 mo of the reference date was 13, 7, and 3% for B. dolosa, B. multivorans, and control patients, respectively (B. dolosa vs. control hazard ratio, 10.8; 95% confidence interval, 1.3-92.8; p = 0.03).

CONCLUSIONS

B. dolosa chronic infection in cystic fibrosis is associated with accelerated loss of lung function and decreased survival.

Airway inflammation and bronchial bacterial colonization in chronic obstructive pulmonary disease

RATIONALE

Inflammation is now recognized as an integral part of the pathogenesis of chronic obstructive pulmonary disease (COPD). In contrast to the sterile airways of normal lungs, bacterial pathogens are often isolated from the airways in stable COPD. This "colonization" of the tracheobronchial tree, currently believed to be innocuous, could serve as an inflammatory stimulus, independent of current tobacco smoke exposure.

OBJECTIVE

To test the hypothesis that bacterial colonization is associated with airway inflammation in stable COPD.

METHODS

Bronchoscopy with bronchoalveolar lavage (BAL) was performed in three groups of subjects: 26 ex-smokers with stable COPD (COPD), 20 ex-smokers without COPD (ex-smokers), and 15 healthy nonsmokers (nonsmokers). Quantitative bacterial cultures, cell counts, chemokine, cytokine, proteinase/antiproteinase, and endotoxin levels in the BAL fluid were compared.

RESULTS

Potentially pathogenic bacteria were recovered at > or = 100 cfu/ml in 34.6% of COPD, 0% of ex-smokers, and in 6.7% of nonsmokers (p = 0.003). All values are expressed as median (interquartile range). Subjects with colonized COPD had significantly greater relative (12.0 [28.4] vs. 3.0 [7.8]%, p = 0.03) and absolute (4.98 [5.26] x 10(4)/ml vs. 3.04 [2.82] x 10(4)/ml, p = 0.02) neutrophil counts, interleukin 8 (33.8 [189.8] vs. 16.9 [20.1] pg/ml, p = 0.005), active matrix metalloproteinase-9 (2.16 [4.30] vs. 0.84 [0.99] U/ml, p = 0.03), and endotoxin (36.0 [72.6] vs. 3.55 [7.17] mEU/ml, p = 0.004) levels in the BAL than the subjects with noncolonized COPD. These inflammatory constituents of BAL were also significantly elevated in subjects with colonized COPD when compared with ex-smokers and nonsmokers.

CONCLUSIONS

Bacterial colonization is associated with neutrophilic airway lumen inflammation in ex-smokers with COPD and could contribute to progression of airway disease in COPD.

Oxidative Changes of Bronchoalveolar Proteins in Cystic Fibrosis

Chronic bacterial infection and severe, polymorphonuclear neutrophil-dominated endobronchial inflammation are characteristic hallmarks of cystic fibrosis (CF) lung disease. The free radicals generated can be deleterious for structure and function of many proteins. The goal of this study was to investigate the degree of oxidation of pulmonary epithelial lining fluid proteins. BAL fluid (BALF) from 55 children with CF and from 11 patients in a control group were investigated by dot-blot assay for content and by two-dimensional electrophoresis and Western blotting for the pattern of distribution of oxidized proteins. The highest level of oxidative stress, as assessed by the level of protein carbonyls, was found in patients with FEV1 < 80% of predicted or with highly elevated neutrophil counts. Compared to control subjects without lung disease, CF patients with normal lung function and CF patients with a normal neutrophil count in their BALF had significantly higher protein carbonyl levels. The extent of protein oxidation was directly related to the neutrophil granulocyte count and inversely to lung function. Our data support the hypothesis that oxidative damage of pulmonary proteins during chronic and excessive neutrophilic endobronchial inflammation may contribute to the decline of lung function in CF patients.

Flagellin of Pseudomonas aeruginosa inhibits Na+ transport in airway epithelia

Pseudomonas aeruginosa causes severe life-threatening airway infections that are a frequent cause for hospitalization of cystic fibrosis (CF) patients. These Gram-negative pathogens possess flagella that contain the protein flagellin as a major structural component. Flagellin binds to the host cell glycolipid asialoGM1 (ASGM1), which appears enriched in luminal membranes of respiratory epithelial cells. We demonstrate that in mouse airways, luminal exposure to flagellin leads to inhibition of Na+ absorption by the epithelial Na+ channel ENaC, but does not directly induce a secretory response. Inhibition of ENaC was observed in tracheas of wild-type mice and was attenuated in mice homozygous for the frequent cystic fibrosis conductance regulator (CFTR) mutation G551D. Similar to flagellin, anti-ASGM1 antibody also inhibited ENaC. The inhibitory effects of flagellin on ENaC were attenuated by blockers of the purinergic signaling pathway, although an increase in the intracellular Ca2+ concentration by recombinant or purified flagellin or whole flagella was not observed. Because an inhibitor of the mitogen-activated protein kinase (MAPK) pathway also attenuated the effects of flagellin on Na+ absorption, we conclude that flagellin exclusively inhibits ENaC, probably due to release of ATP and activation of purinergic receptors of the P2Y subtype. Stimulation of these receptors activates the MAPK pathway, thereby leading to inhibition of ENaC. Thus, P. aeruginosa reduces Na+ absorption, which could enhance local mucociliary clearance, a mechanism that seem to be attenuated in CF.

Simultaneous coinfection by multiple strains during Burkholderia cepacia complex infection in cystic fibrosis

Much remains unknown about the natural history of respiratory tract infection by Burkholderia cepacia complex (Bcc) in persons with cystic fibrosis (CF). Specifically, it is not clear whether infected CF patients typically harbor a single Bcc strain or multiple strains that may be phenotypically indistinguishable. We genotyped 912 Bcc isolates recovered from CF sputum culture from in excess of 100 patients to demonstrate that chronic infection generally involves a single strain. Transient coinfection with more than 1 strain occurs infrequently and may be more common early in the course of Bcc infection.

Anti-inflammatory effect of augmented nitric oxide production in chronic lung infection

Chronic infection of the lungs with Pseudomonas aeruginosa complicates many long-term lung diseases including cystic fibrosis, bronchiectasis, chronic obstructive lung disease, and mechanical ventilation. In acute inflammatory lung diseases, increased nitric oxide synthase (NOS-2) expression leads to excess nitric oxide (NO) production, resulting in the production of reactive nitrogen intermediates, which contribute to tissue damage. In contrast, the contribution of NO to pulmonary damage in chronic Pseudomonas infection of the lung has not been directly examined and is unclear. Although NOS-2 expression is increased in this condition, NO production is not abnormally elevated. It was hypothesized that chronic infection of the airways does not cause increased NO production but, in contrast, leads to inappropriately low NO concentrations that are pro-inflammatory. A rodent model of chronic airway infection was used to examine the effects on lung damage of augmenting or inhibiting NO production after airway infection with P. aeruginosa was well established. Three days post-infection, L-arginine, which augments NO production, or L-NAME, an inhibitor of NO production, was administered in drinking water. Lung damage was assessed 12 days later. L-arginine treatment reduced tissue damage, inhibited neutrophil recruitment, and reduced the pro-inflammatory cytokine interleukin (IL)-1beta. Treatment with L-NAME caused loss of alveolar walls, greater vascular damage, and increased levels of the pro-inflammatory cytokine IL-6. Thus, in chronic airway infection, inhibition of NO production worsened lung damage, whereas augmenting NO ameliorated this damage. This is the first demonstration that augmenting endogenous NO production in chronic infective lung disease caused by P. aeruginosa is anti-inflammatory. Given that infection with this organism complicates many chronic lung diseases, most notoriously cystic fibrosis, these findings have important clinical implications.

Progression of lung disease on computed tomography and pulmonary function tests in children and adults with cystic fibrosis

BACKGROUND

A study was undertaken to compare the ability of computed tomographic (CT) scores and pulmonary function tests to detect changes in lung disease in children and adults with cystic fibrosis (CF).

METHODS

CT scans and pulmonary function tests were retrospectively studied in a cohort of patients with CF aged 5-52 years for whom two or three CT scans at 3 year intervals were available, together with pulmonary function test results. All CT scans were scored by two observers. Pulmonary function results were expressed as percentage predicted and Z scores.

RESULTS

Of 119 patients studied, two CT scans were available in 92 patients and three in 24. CT (composite and component) scores and lung function both deteriorated significantly (p<0.02). Peripheral bronchiectasis worsened by 1.7% per year in children (p<0.0001) and by 1.5% per year in adults (p<0.0001). Bronchiectasis worsened in 68 of 92 patients while forced expiratory volume in 1 second (FEV1) worsened in 54 of 92 patients; bronchiectasis also deteriorated in 27 patients with stable or improving FEV1. The CT score (and its components) and pulmonary function tests showed similar rates of deterioration in adults and children (p>0.09).

CONCLUSION

The peripheral bronchiectasis CT score deteriorates faster and more frequently than lung function parameters in children and adults with CF, which indicates that pulmonary function tests and CT scans measure different aspects of CF lung disease. Our data support previous findings that the peripheral bronchiectasis CT score has an added value to pulmonary function tests in monitoring CF lung disease.

Dose reduction for CT in children with cystic fibrosis: is it feasible to reduce the number of images per scan?

BACKGROUND

Reducing the dose for each CT scan is important for children with cystic fibrosis (CF).

OBJECTIVE

To determine whether the number of CT images and therefore the dose per CT scan could be reduced without any significant loss of information in children with CF.

MATERIALS AND METHODS

A cohort of children with CF was followed with biennial surveillance CT scans, obtained in inspiration after a voluntary breath-hold as 1-mm thick images at 10-mm intervals from lung apex to base. A random set of 20 baseline CT scans and 10 follow-up CT scans were blinded. Sets of every image (10-mm intervals), every second image (20-mm intervals), every third image (30-mm intervals) and a selection of three and five images were scored randomly using a published CT scoring system by one experienced observer.

RESULTS

The 20 subjects were 10 years of age with a range of 3.7-17.6 years at baseline. Fewer CT images resulted in a significantly lower (less abnormal) CT score and the number of patients positive for abnormalities decreased subsequently. At intervals greater than 20 mm no significant change in CT score over 2 years could be detected, while the CT scores at 10-mm (P=0.02) and 20-mm (P=0.02) intervals worsened significantly.

CONCLUSIONS

A reduction in the number of inspiratory CT images by increasing the interval between images to greater than 10 mm is not a valid option for radiation dose reduction in children with CF.

REGULATION OF NORMAL AND CYSTIC FIBROSIS AIRWAY SURFACE LIQUID VOLUME BY PHASIC SHEAR STRESS

The physical removal of viruses and bacteria on the mucociliary escalator is an important aspect of the mammalian lung's innate defense mechanism. The volume of airway surface liquid (ASL) present in the respiratory tract is a critical determinant of both mucus hydration and the rate of mucus clearance from the lung. ASL volume is maintained by the predominantly ciliated epithelium via coordinated regulation of (a) absorption, by the epithelial Na+ channel, and (b) secretion, by the Ca2+-activated Cl- channel (CaCC) and CFTR. This review provides an update on our current understanding of how shear stress regulates ASL volume height in normal and cystic fibrosis (CF) airway epithelia through extracellular ATP- and adenosine (ADO)-mediated pathways that modulate ion transport and ASL volume homeostasis. We also discuss (a) how derangement of the ADO-CFTR pathway renders CF airways vulnerable to viral infections that deplete ASL volume and produce mucus stasis, and (b) potential shear stress-dependent therapies for CF.

The role of airway epithelium and blood neutrophils in the inflammatory response in cystic fibrosis

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which accounts for the cAMP-modulated chloride conductance of airway epithelial cells. CFTR also regulates other membrane proteins like the negative regulation of the amiloride-sensitive epithelial sodium channel (ENaC). Mutations in the CFTR gene lead to hyperabsorption of sodium chloride and a reduction in the periciliary salt and water content which leads to impaired mucociliary clearance. It seems that a lack of functional CFTR leads to abnormal function of the NF-kappaB pathway in submucosal gland cells, causing an increased production of pro-inflammatory cytokines and the chemokine IL-8, and a pro-inflammatory environment. CFTR is also expressed in neutrophils and several neutrophil functions like cytokine production, migration, phagocytosis and apoptosis seem altered in CF. In this review we describe the role of airway epithelium and blood neutrophils in the viscious circle of inflammation and infection seen in CF.

Increased Arginase Activity in Cystic Fibrosis Airways

RATIONALE

Airway nitric oxide concentrations are reduced in cystic fibrosis (CF). Arginases compete for L-arginine, the substrate of nitric oxide synthesis.

OBJECTIVES

We hypothesized that increased arginase activity may be one factor contributing to nitric oxide deficiency in CF.

MEASUREMENTS

We therefore studied sputum arginase activity, exhaled nitric oxide, and pulmonary function in patients with cystic fibrosis.

RESULTS

Mean (+/- SEM) sputum arginase activity was significantly higher in patients admitted for pulmonary exacerbation compared with patients with stable disease (1.032 +/- 0.148 vs. 0.370 +/- 0.091 U/mg protein, p = 0.004). Fourteen days of intravenous antibiotic treatment resulted in significantly decreased sputum arginase activity in all patients (p = 0.0002). However, arginase activity was still significantly (p = 0.0001) higher in CF sputum after treatment for exacerbation compared with induced sputum from healthy control subjects (0.026 +/- 0.006 U/mg protein). Negative correlations were found for sputum arginase activity at admission with FEV1 (r = -0.41, p = 0.01), as well as changes in arginase activity with percent change in FEV1 during antibiotic therapy (r = -0.4, p < 0.01) in CF. Exhaled nitric oxide in CF was positively correlated to FEV1 (r = 0.34, p = 0.007), and in patients admitted for pulmonary exacerbation negatively correlated to sputum arginase activity (r = -0.45, p = 0.03).

CONCLUSIONS

These data suggest that increased sputum arginase activity contributes to nitric oxide deficiency in CF lung disease and may be relevant in the pathogenesis of CF airway disease.

A novel strategy for the isolation and identification of environmental Burkholderia cepacia complex bacteria

The purpose of this study was to develop a novel strategy for the isolation and identification of Burkholderia cepacia complex bacteria from the home environment of cystic fibrosis (CF) patients. Water and soil samples were enriched in a broth containing 0.1% l-arabinose, 0.1% l-threonine, and a mixture of selective agents including 1 microgml(-1) C-390, 600U ml(-1) polymyxin B sulfate, 10 microgml(-1) gentamycin, 2 microgml(-1) vancomycin and 10 microgml(-1) cycloheximide. On selective media (consisting of the same components as above plus 1.8% agar), several dilutions of the enrichment broth were inoculated and incubated for 5 days at 28 degrees C. Isolates with different randomly amplified polymorphic DNA patterns were inoculated in Stewart's medium. Putative B. cepacia complex bacteria were confirmed by means of recA PCR and further identified by HaeIII-recA restriction fragment length polymorphism analysis. Our results suggest that these organisms may be more widespread in the home environment than previously assumed and that plant associated soil and pond water may be reservoirs of B. cepacia complex infection in CF patients.

Biological effects of a dietary omega-3 polyunsaturated fatty acids supplementation in cystic fibrosis patients: a randomized, crossover placebo-controlled trial

BACKGROUND AND AIMS

Various anti-inflammatory therapies, including dietary omega-3 polyunsaturated fatty acids (PUFA) supplementation, have been investigated in cystic fibrosis (CF) patients. To further explore this nutritional approach, biological effects of an omega-3 PUFA oral liquid supplementation were measured in 17 CF patients in a double-blind, randomized, crossover without a washout period and placebo-controlled study.

METHODS

CF patients (age: 18+/-9 year; weight: 43+/-13 kg) received a liquid dietary supplementation either enriched or not in omega-3 PUFA (390-1170 mg/day according to patient weight) during two 6-month periods.

RESULTS

Increase in eicosapentaenoic acid was observed in neutrophil membrane following omega-3 PUFA dietary supplementation (from 0.7+/-0.6 to 1.6+/-0.6 micromol%, P<0.01). The leukotriene B(4) (LTB(4))/leukotriene B(5) (LTB(5)) ratio was decreased (from 72+/-27 to 24+/-7, P<0.001) in CF patients taking omega-3 PUFA supplements. In contrast, omega-3 PUFA supplementation affected neither internalization of IL-8 receptors following IL-8 exposure, nor IL-8-induced neutrophil chemotaxis.

CONCLUSION

Our results show that omega-3 PUFA are incorporated in neutrophil membranes. The subsequent decrease in LTB(4)/LTB(5) ratio suggests that, in such conditions, neutrophils may produce less pro-inflammatory mediators from the acid arachidonic pathway. These data indicate that omega-3 PUFA intake may have anti-inflammatory effect that still need to be assessed by long-term studies following large groups of patients.

Proteomic Analysis of Sputum from Adults and Children with Cystic Fibrosis and from Control Subjects

RATIONALE

Recurrent pulmonary exacerbations are associated with progressive lung disease in cystic fibrosis (CF). Current definitions of an exacerbation, although not precisely defined, include new/worsening symptoms, declining lung function, and/or changing radiologic appearance. Early diagnosis of exacerbations by rapid noninvasive means should expedite therapeutic intervention, thereby minimizing lung damage.

OBJECTIVES

To identify biomarkers of lung exacerbation for point-of-care monitoring of CF lung disease progression.

METHODS

Saline-induced sputum was collected from adults with CF with an exacerbation and requiring hospitalization (FEV(1) < 60%), a subset of these adults at hospital discharge, children with stable CF and preserved lung function (FEV(1) > 70%), and control subjects (FEV(1) > 80%). Sputum was arrayed by two-dimensional electrophoresis and differentially expressed proteins were identified by proteomic analysis.

MEASUREMENTS AND MAIN RESULTS

Sputum profiles from adults with CF with an exacerbation were characterized by extensive proteolytic degradation and influx of inflammation-related proteins, with some adults with CF approaching a "healthy" protein profile after hospitalization. Two children with CF showed profiles and biomarker expression resembling those of adults with an exacerbation. Levels of differentially expressed myeloperoxidase, cleaved alpha(1)-antitrypsin, IgG degradation, interleukin-8, and total protein concentration, together with their correlation to FEV(1), were statistically significant. Statistical correlation analyses indicated that changes in myeloperoxidase expression and IgG degradation were the strongest predictors of FEV(1).

CONCLUSIONS

We identified extensive protein degradation and differentially expressed proteins as biomarkers of inflammation relating to pulmonary exacerbations. Prediction of exacerbation onset and more precise evaluation of the extent of resolution with treatment could be achieved by including biomarkers in standard assessment.

Abnormalities in the pulmonary innate immune system in cystic fibrosis

Pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the basis for this susceptibility remains incompletely understood. One hypothesis is that CF airway surface liquid (ASL) is abnormal and interferes with neutrophil function. To study this possibility, we developed an in vitro system in which we collected ASL from primary cultures of normal and CF airway epithelial cells. Microbial killing was less efficient when bacteria were incubated with neutrophils in the presence of ASL from CF epithelia compared with normal ASL. Antimicrobial functions of human neutrophils were assessed in ASL from CF and normal epithelia using a combination of quantitative bacterial culture, flow cytometry, and microfluorescence imaging. The results of these assays of neutrophil function were indistinguishable in CF and normal ASL. In contrast, the direct bactericidal activity of ASL to Escherichia coli and to clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa was substantially less in CF than in normal ASL, even when highly diluted in media of identical ionic strength. Together, these observations indicate that the antimicrobial properties of ASL in CF are compromised in a manner independent of ionic strength of the ASL, and that this effect is not mediated through a direct effect of the ASL on phagocyte function.

Sequential analysis of surfactant, lung function and inflammation in cystic fibrosis patients

BACKGROUND

In a cross-sectional analysis of cystic fibrosis (CF) patients with mild lung disease, reduced surfactant activity was correlated to increased neutrophilic airway inflammation, but not to lung function. So far, longitudinal measurements of surfactant function in CF patients are lacking and it remains unclear how these alterations relate to the progression of airway inflammation as well as decline in pulmonary function over time.

METHODS

As part of the BEAT trial, a longitudinal study to assess the course of airway inflammation in CF, we studied lung function, surfactant function and endobronchial inflammation using bronchoalveolar lavage fluid from 20 CF patients with normal pulmonary function (median FEV1 94% of predicted) at three times over a three year period.

RESULTS

There was a progressive loss of surfactant function, assessed as minimal surface tension. The decline in surfactant function was negatively correlated to an increase in neutrophilic inflammation and a decrease in lung function, assessed by FEV1, MEF(75/25%VC), and MEF(25%VC). The concentrations of the surfactant specific proteins A, C and D did not change, whereas SP-B increased during this time period.

CONCLUSION

Our findings suggest a link between loss of surfactant function driven by progressive airway inflammation and loss of small airway function in CF patients with limited lung disease.

Microbiological rationale for the utilisation of prulifloxacin, a new fluoroquinolone, in the eradication of serious infections caused by Pseudomonas aeruginosa

Minimal inhibitory concentrations (MICs) of prulifloxacin were evaluated in comparison with ciprofloxacin, levofloxacin and moxifloxacin against a large collection (N = 300) of Pseudomonas aeruginosa strains characterised according to the CLSI/NCCLS microdilution method. Additional in vitro tests (time-kill curves and mutant prevention concentration (MPC) determinations) were carried out. Assuming a susceptibility breakpoint for prulifloxacin identical to that of ciprofloxacin, the new fluoroquinolone emerged as the most potent antibiotic (72% of susceptible strains versus 65%, 61% and 23% for ciprofloxacin, levofloxacin and moxifloxacin, respectively). Time-kill tests at 4x MIC confirmed the pronounced bactericidal potency of the drug against P. aeruginosa. Amongst the members of the fluoroquinolone class assessed, prulifloxacin produced the lowest MPC values (< or = 4 mg/L). Our in vitro results indicate that prulifloxacin represents the most powerful antipseudomonal drug available today.

Hyperpolarized HHe 3 MRI of the lung in cystic fibrosis: assessment at baseline and after bronchodilator and airway clearance treatment

RATIONALE AND OBJECTIVES

The purpose of this study is to determine hyperpolarized helium 3 (HHe) magnetic resonance (MR) findings of the lung in patients with cystic fibrosis (CF) compared with healthy subjects and determine whether HHe MR can detect changes after bronchodilator therapy or mechanical airway mucus clearance treatment.

MATERIALS AND METHODS

Thirty-one subjects, 16 healthy volunteers and 15 patients with CF, underwent HHe lung ventilation MR imaging and spirometry at baseline. Eight patients with CF then were treated with nebulized albuterol, after which a follow-up HHe MR scan was obtained. Subsequently, recombinant human deoxyribonuclease (DNase) treatment and chest physical therapy were performed in these eight subjects, followed by a third HHe MR scan. For each MR study, the number of ventilation defects was scored by a human reader.

RESULTS

Patients with CF had significantly more HHe MR ventilation defects per image than healthy subjects (mean, 8.2 defects in patients with CF vs 1.6 defects in healthy subjects; P < .05). Even the four subjects with CF with a normal forced expiratory volume in 1 second had significantly more ventilation defects than healthy subjects (mean, 6.5 defects in these patients with CF; P = .0002). After treatment with albuterol, there was a small, but statistically significant, decrease in number of ventilation defects (mean, 9.6-8.0 defects; P = .025). After DNase and chest physical therapy, there was a trend toward increasing ventilation defects (mean, 8.3 defects; P = .096), but with a residual net improvement relative to baseline.

CONCLUSION

In patients with CF, HHe MR ventilation defects correlate with spirometry, change with treatment, and are elevated in number in patients with CF with normal spirometry results. Thus, HHe MR appears to possess many of the characteristics required of a biomarker for pulmonary CF and may be useful in the evaluation of CF pulmonary disease severity or progression.

Impact of CFTR ΔF508 mutation on prostaglandin E2production and type IIA phospholipase A2expression by pulmonary epithelial cells

Cystic fibrosis (CF) is characterized by an exacerbated inflammatory pulmonary response with excessive production of inflammatory mediators. We investigated here the impact of cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction on prostaglandin E2(PGE2) production and type IIA secreted phospholipase A2(sPLA2-IIA) expression. We show that both resting and LPS-stimulated human respiratory epithelial cell line bearing ΔF508 mutation on CFTR (CF cells) released more PGE2than control cell line. This was accompanied by enhanced expression and activity of cyclooxygenase-2 in CF cells. PGE2release was attenuated after experimentally induced retrafficking of the ΔF508-CFTR at the plasma membrane. sPLA2-IIA expression occurred at higher levels in CF cells than in control cells and was enhanced by LPS and PGE2. Suppression of PGE2synthesis by aspirin led to an inhibition of LPS-induced sPLA2-IIA expression. Higher activation of NF-κB was observed in CF cells compared with control cells and was enhanced by LPS. However, addition of PGE2or aspirin had no effect on NF-κB activation. LPS-induced sPLA2-IIA expression was reduced by an NF-κB inhibitor. We suggest that the lack of the CFTR in the plasma membrane results in a PGE2overproduction and an enhanced sPLA2-IIA expression. This expression is upregulated by NF-κB and amplified by PGE2via a unidentified signaling pathway.

Estimation of cancer mortality associated with repetitive computed tomography scanning

RATIONALE

Low-dose radiation from computed tomography (CT) may increase the risk of certain cancers, especially in children.

OBJECTIVE

We sought to estimate the excess all-cause and cancer-specific mortality, which may be associated with repeated CT scanning of patients with cystic fibrosis (CF).

METHODS

The radiation dose was calculated for a published CF surveillance CT scanning protocol of biennial CT scans, and the risk per scan was estimated using atom-bomb survivor data. A computational model was developed to calculate the excess mortality in a CF cohort associated with radiation from the CT scan and to evaluate the effects of background survival, scanning interval, and level of CT radiation used. The model assumed that there would be no survival benefits associated with repeated surveillance CT scanning.

RESULTS

The average radiation dose for the published CT protocol was 1 mSv. Survival reduction associated with annual scans from age 2 yr until death was approximately 1 mo and 2 yr for CF cohorts, with a median survival of 26 and 50 yr, respectively. Corresponding cumulative cancer mortality was approximately 2 and 13% at age 40 and 65 yr, respectively. Biennial CT scanning reduced all-cause and cumulative cancer mortality by half.

CONCLUSION

Routine lifelong annual CT scans carry a low risk of radiation-induced mortality in CF. However, as the overall survival increases for patients with CF, the risk of radiation-induced mortality may modestly increase. These data indicate that radiation dose must be considered in routine CT imaging strategies for patients with CF, to ensure that benefits outweigh the risks.

Voriconazole therapy in children with cystic fibrosis

BACKGROUND

There is increasing evidence for the efficacy of the antifungal voriconazole, particularly in immunosuppression. We describe our experience of using voriconazole in children with CF.

METHODS

We performed a retrospective case note review of children with CF treated with voriconazole in a single centre over an 18 month period.

RESULTS

A total of 21 children aged 5 to 16 years (median 11.3) received voriconazole for between 1 and 50 (22) weeks. Voriconazole was used as monotherapy in 2 children with recurrent allergic bronchopulmonary aspergillosis (ABPA); significant and sustained improvements in clinical and serological parameters for up to 13 months were observed, without recourse to oral steroids. Voriconazole was used in combination with an immunomodulatory agent in a further 11 children with ABPA, with significant improvement in pulmonary function and serology. 8 children without ABPA but who had recurrent Aspergillus fumigatus isolates and increased symptoms also received voriconazole; this group did not improve with treatment. Adverse effects occurred in 7 children (33%: photosensitivity reaction 3, nausea 2, rise in hepatic enzymes 1, hair loss 1).

CONCLUSIONS

Voriconazole may be a useful adjunctive therapy for ABPA in CF. Voriconazole monotherapy appears to be an alternative treatment strategy when oral corticosteroids may not be suitable.

Pseudomonas aeruginosa inhibits endocytic recycling of CFTR in polarized human airway epithelial cells

The most common mutation in the CFTR gene in individuals with cystic fibrosis (CF), DeltaF508, leads to the absence of CFTR Cl(-) channels in the apical plasma membrane, which in turn results in impairment of mucociliary clearance, the first line of defense against inhaled bacteria. Pseudomonas aeruginosa is particularly successful at colonizing and chronically infecting the lungs and is responsible for the majority of morbidity and mortality in patients with CF. Rescue of DeltaF508-CFTR by reduced temperature or chemical means reveals that the protein is at least partially functional as a Cl(-) channel. Thus current research efforts have focused on identification of drugs that restore the presence of CFTR in the apical membrane to alleviate the symptoms of CF. Because little is known about the effects of P. aeruginosa on CFTR in the apical membrane, whether P. aeruginosa will affect the efficacy of new drugs designed to restore the plasma membrane expression of CFTR is unknown. Accordingly, the objective of the present study was to determine whether P. aeruginosa affects CFTR-mediated Cl(-) secretion in polarized human airway epithelial cells. We report herein that a cell-free filtrate of P. aeruginosa reduced CFTR-mediated transepithelial Cl(-) secretion by inhibiting the endocytic recycling of CFTR and thus the number of WT-CFTR and DeltaF508-CFTR Cl(-) channels in the apical membrane in polarized human airway epithelial cells. These data suggest that chronic infection with P. aeruginosa may interfere with therapeutic strategies aimed at increasing the apical membrane expression of DeltaF508-CFTR.

Antimicrobial therapy for pulmonary pathogenic colonisation and infection by Pseudomonas aeruginosa in cystic fibrosis patients

Pseudomonas aeruginosa colonisation has a negative effect on pulmonary function in cystic fibrosis patients. The organism can only be eradicated in the early stage of colonisation, while reduction of bacterial density is desirable during chronic colonisation or exacerbations. Monthly, or at least 3-monthly, microbiological culture is advisable for patients without previous evidence of P. aeruginosa colonisation. Cultures should be performed at least every 2-3 months in patients with well-established colonisation, and always during exacerbations or hospitalisations. Treatment of patients following the first isolation of P. aeruginosa, but with no clinical signs of colonisation, should be with oral ciprofloxacin (15-20 mg/kg twice-daily for 3-4 weeks) plus inhaled tobramycin or colistin (intravenous treatment with or without inhaled treatment can be used as an alternative), while patients with acute infection should be treated for 14-21 days with high doses of two intravenous antimicrobial agents, with or without an inhaled treatment during or at the end of the intravenous treatment. Maintenance treatment after development of chronic P. aeruginosa infection/colonisation (pathogenic colonisation) in stable patients (aged>6 years) should be with inhaled tobramycin (300 mg twice-daily) in 28-day cycles (on-off) or, as an alternative, colistin (1-3 million units twice-daily). Colistin is also a possible choice for patients aged<6 years. Treatment can be completed with oral ciprofloxacin (3-4 weeks every 3-4 months) for patients with mild pulmonary symptoms, or intravenously (every 3-4 months) for those with severe symptoms or isolates with ciprofloxacin resistance. Moderate and serious exacerbations can be treated with intravenous ceftazidime (50-70 mg/kg three-times-daily) or cefepime (50 mg/kg three-times-daily) plus tobramycin (5-10 mg/kg every 24 h) or amikacin (20-30 mg/kg every 24 h) for 2-3 weeks. Oral ciprofloxacin is recommended for patients with mild pulmonary disease. If multiresistant P. aeruginosa is isolated, antimicrobial agents that retain activity are recommended and epidemiological control measures should be established.

Étude multicentrique portant sur l'évaluation d'une méthode simplifiée d'analyse bactériologique dans la surveillance des infections bronchiques à Pseudomonas aeruginosa survenant au cours de la mucoviscidose

BACKGROUND

Sputum bacteriological analysis of cystic fibrosis (CF) patients colonised by Pseudomonas aeruginosa is difficult. The bronchial persistence of these bacteria involves phenotypical modifications and the many antibiotic treatments result in emergence of multiresistant strains. The aim of this study is to evaluate a new fast identification and sensitivity testing method of P. aeruginosa and other pathogenic bacteria in sputum of CF patients. It is based on applying a gradient of antibiotic (E-test strip) onto an agar plate inoculated with the sputum.

OBSERVATIONS

310 sputum, collected from adults and children colonised by P. aeruginosa, were analysed by this new method. This method allowed a direct reading of the minimal concentration of antibiotic that inhibited the totality of Gram-negative strains and the detection of resistant pathogenic bacteria inside the ellipse of inhibition. Results obtained by this new method were compared with the conventional method for identification and antimicrobial sensitivity.

CONCLUSION

This new method, studying with CF patient colonised by P. aeruginosa, appears interesting, with a sensibility equal or higher than 89% in detection of the bacteria and their sensitivity to antibiotics. Furthermore it allows a saving of time and simplified results.

[Cystic fibrosis in adults: inter- and intraobserver agreement for the Brasfield and Chrispin-Norman chest radiography scoring systems and correlation with clinical data and spirometry]

OBJECTIVE

Most chest radiography scoring systems for patients with cystic fibrosis have been developed for children but are also used for adults. Our aim was to evaluate the intra- and interobserver variability of 2 radiographic scoring systems in adults with cystic fibrosis and to assess the correlation of these systems with clinical and spirometric parameters.

PATIENTS AND METHODS

The chest x-rays of 24 adult patients with cystic fibrosis were compared using 2 scoring systems (Brasfield and Chrispin-Norman). The x-rays were scored by 2 radiologists and reevaluated 4 months later by 1 of the 2 observers. Intra- and interobserver agreement was assessed using the intraclass and Pearson's correlation coefficients. The radiographic scores were compared to lung function tests and other clinical data.

RESULTS

Both intra- and interobserver agreement were high (r > or = 0.9 and the intraclass correlation coefficient > or = 0.85 with both systems for both samples). Both scoring systems correlated with spirometry results: forced expiratory volume in the first second (FEV1) (r = 0.64 and r = 0.55), FEV1% (r = 0.75 and r = 0.72), and the percentage of forced vital capacity in relation to the predicted value (r = 0.63 and r = 0.056). We found no association between scoring system and sex, age, or body mass index.

CONCLUSIONS

Assessment of chest radiographs of adult patients with cystic fibrosis by the Brasfield and Chrispin-Norman scoring systems shows good intra- and interobserver agreement. Both systems correlate well with lung function variables, especially FEV1.

[Nontuberculous mycobacteria in patients with cystic fibrosis]

OBJECTIVE

Patients with cystic fibrosis are at great risk of infection by nontuberculous mycobacteria from the environment because of certain predisposing factors such as bronchiectasis, malnutrition, and diabetes. The aim of this study was to analyze the mycobacterial content of sputum smears and cultures from adult patients with cystic fibrosis attended at a specialized unit for adults from March 1997 through December 2001.

PATIENTS AND METHODS

Sputum samples were collected prospectively according to a protocol applied at each visit, and during most exacerbations staining and culture for mycobacteria were ordered in addition to the usual cultures for bacteria and fungi. A tuberculin test was performed at the end of the study.

RESULTS

Twenty-eight patients (16 men) with cystic fibrosis were enrolled. The mean (SD) age was 25.3 (6.7) years. A total of 251 samples were cultured (range in number of samples per patient, 1-31). The mean period of follow up was 40.3 (22.1) months. The sputum smear was positive in 29 cases (4 patients); the culture was positive in 7 patients. More than 3 samples were positive in only 4 patients. Mycobacterium abscessus was isolated in 3 cases, Mycobacterium avium complex in 2 and Mycobacterium simiae in 1 and other an unidentified rapid growth Mycobacterium species. The Mantoux test was positive in 5 patients. Two of the 4 patients in whose samples mycobacteria were isolated repeatedly required treatment.

CONCLUSIONS

The prevalence of nontuberculous mycobacterial infection is high in patients with cystic fibrosis. Staining and culture for mycobacteria should be carried out regularly and whenever exacerbation of pulmonary symptoms cannot be attributed to bacteria usually found in such patients. Patients with recurrent isolations of mycobacteria should be monitored closely.

Use of Pseudomonas biofilm susceptibilities to assign simulated antibiotic regimens for cystic fibrosis airway infection

OBJECTIVES

Increasing evidence indicates that Pseudomonas aeruginosa grows as a biofilm in the lungs of cystic fibrosis (CF) patients. In contrast, the bacterial inoculum used in conventional susceptibility testing is composed of planktonic cells. As a prelude to a clinical trial of biofilm susceptibility testing in CF, simulated antibiotic regimens based on either biofilm or conventional susceptibility testing of CF patient isolates were compared.

PATIENTS AND METHODS

Biofilm and conventional susceptibilities were determined for P. aeruginosa isolate sets from 40 CF patients. An algorithm was used to assign simulated regimens of two anti-pseudomonal antibiotics for each patient/susceptibility method dataset. For agents with equivalent activity, the algorithm included a drug selection hierarchy, the rationale for which was suppression of chronic infection. Substitution of an alternative hierarchy, based on treatment of acute exacerbation, was used to evaluate the robustness of the regimen assignments.

RESULTS

For both drug-ranking schemes, all 40 simulated regimens based on conventional susceptibilities included a beta-lactam antibiotic. In contrast, based on biofilm testing, only 43% of chronic regimens and 65% of acute regimens included a beta-lactam. Moreover, the conventional and biofilm regimens assigned to individual patients were discordant, with only 20% and 40% of chronic and acute regimens, respectively, consisting of drugs in the same two mechanistic classes by both methods.

CONCLUSIONS

Biofilm susceptibility testing of CF P. aeruginosa isolate sets leads to different antibiotic assignments than conventional testing, with no single two-drug regimen predicted to provide optimal anti-biofilm activity against the majority of isolate sets.

Cystic fibrosis, disease severity, and a macrophage migration inhibitory factor polymorphism

RATIONALE

Macrophage migration inhibitory factor (MIF) is a key proinflammatory mediator. It contributes toward an exaggerated gram-negative inflammatory response via its ability to induce Toll-like receptor-4 expression. Studies have shown that MIF knockout mice have less aggressive Pseudomonas infection (compared with wild-type).

OBJECTIVES

To assess whether a novel functional MIF polymorphism was associated with clinical prognosis in a patient cohort with chronic gram-negative infection, namely cystic fibrosis (CF).

METHODS

Collected genomic DNA was analyzed via polymerase chain reaction amplification for the polymorphic region for the CATT repeat polymorphism. Individuals may have a 5-, 6-, 7-, or 8-CATT tetranucleotide repeat unit on each allele. The 5-CATT repeat allele exhibits the lowest MIF promoter activity.

MEASUREMENTS AND MAIN RESULTS

Patients with stable CF (n = 167) and a matched control group (n = 166) were enrolled. In patients with CF, the MIF5(+) group had a decreased incidence of Pseudomonas aeruginosa colonization (odds ratio, 0.25; 95% confidence interval, 0.09-0.65; p = 0.004) and a significant reduction in the risk of pancreatic insufficiency (odds ratio, 0.27; 95% confidence interval, 0.07-1.0; p = 0.05). A trend toward milder disease activity in the MIF5(+) group was seen with all other parameters.

CONCLUSIONS

The results support the concept of a regulatory role for MIF in CF.

Ciprofloxacin induction of a susceptibility determinant in Pseudomonas aeruginosa

With few novel antimicrobials in development, resistance to the current selection of antibiotics increasingly encroaches on our ability to control microbial infections. One limitation in our understanding of the basis of the constraints on current therapies is our poor understanding of antibiotic interactions with bacteria on a global scale. Custom DNA microarrays were used to characterize the response of Pseudomonas aeruginosa to ciprofloxacin, a fluoroquinolone commonly used in therapy against chronic infections by this intrinsically resistant bacterium. Of the approximately 5,300 open reading frames (ORFs) on the array, 941 genes showed statistically significant (P </= 0.05) differential expression in response to 0.3x MIC of ciprofloxacin; 554 were promoted and 387 were repressed. Most striking among the responsive genes was the region between PA0613 and PA0648, which codes for the bacteriophage-like R2/F2 pyocins. In this region, virtually every ORF was increased by 0.3x MIC of ciprofloxacin and even more dramatically up-regulated (7- to 19-fold) following treatment with 1x MIC of ciprofloxacin. Pyocin gene expression was confirmed with lux reporter mutants and real-time PCR studies; pyocin-like particles were also present in transmission electron micrographs of supernatants from cells treated with 1x MIC of ciprofloxacin. Interestingly, mutants in this region exhibited >/=8-fold-increased resistance to ciprofloxacin and other fluoroquinolones, demonstrating that this region is a susceptibility determinant. Since this region is known to be variably present in the genomes of clinical isolates of P. aeruginosa (R. K. Ernst et al., Environ. Microbiol. 5:1341-1349, 2003, and M. C. Wolfgang et al., Proc. Natl. Acad. Sci. USA 100:8484-8489, 2003), these findings demonstrate that the R2/F2 pyocin region is a "loaded gun" that can mediate fluoroquinolone susceptibility in P. aeruginosa.

Effects of azithromycin on clinical isolates of Pseudomonas aeruginosa from cystic fibrosis patients

There is considerable interest in the use of azithromycin for the treatment of lung disease in patients with cystic fibrosis (CF). Although its mechanism of action as an inhibitor of bacterial protein synthesis has been well-established, it is less clear how azithromycin ameliorates the lung disease associated with Pseudomonas aeruginosa, which is considered to be resistant to the drug. We tested the effects of azithromycin on clinical isolates (CIs) from CF patients and compared them with laboratory reference strains to establish how this drug might interfere with the production of bacterial virulence factors that are relevant to the pathogenesis of airway disease in CF patients. Azithromycin inhibited P aeruginosa PAO1 protein synthesis by 80%, inhibiting bacterial growth and the expression of immunostimulatory exoproducts such as pyocyanin, as well as the gene products necessary for biofilm formation. In contrast, the effects of azithromycin on CIs of P aeruginosa were much more variable, due in large part to their slow growth and limited exoproduct expression. Culture supernatants for two of three clinical strains induced appreciable CXCL8 expression from cultured epithelial cells. Azithromycin treatment of the organisms inhibited 65 to 70% of this induction; azithromycin had no direct effect on the ability of either normal cells or CF epithelial cells to produce CXCL8. Azithromycin does decrease the P aeruginosa synthesis of immunostimulatory exoproducts and is likely to be most effective against planktonic, actively growing bacteria. This effect is less predictable against CIs than the prototypic strain PAO1.

Breakpoints for predicting Pseudomonas aeruginosa susceptibility to inhaled tobramycin in cystic fibrosis patients: use of high-range Etest strips

Inhaled administration of tobramycin assures high concentrations in cystic fibrotic lungs, improving the therapeutic ratio over that of parenteral tobramycin levels, particularly against Pseudomonas aeruginosa. Conventional Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards) breakpoints only consider parenteral levels and do not take into account these high antimicrobial concentrations. The Spanish Antibiogram Committee (The MENSURA Group) has tentatively defined specific breakpoint values for inhaled tobramycin when testing P. aeruginosa isolates from cystic fibrosis (CF) patients (susceptible, < or =64 microg/ml; resistant, > or =128 microg/ml). The antimicrobial susceptibilities of 206 prospectively collected CF P. aeruginosa isolates were determined by the reference agar dilution method. For tobramycin, the performance of high range tobramycin Etest strips (AB Biodisk, Solna, Sweden) and conventional tobramycin disks were assessed with the same collection. Applying MENSURA proposed breakpoints, 95.1% of the strains were categorized as susceptible to tobramycin, either using agar dilution or Etest high-range strips (99% categorical agreement between both methods). With CLSI breakpoints, susceptibility rates decreased to 79.1 and 81.1% for agar dilution and Etest strips, respectively (83.5% categorical agreement). Minor, major, and very major errors for Etest strips (CLSI criteria) were 13.6, 1.2, and 14.8%, respectively. Upon applying the new proposed criteria for inhaled tobramycin, only one major and one very major error were observed with Etest strips. Whenever inhaled tobramycin is considered for therapy, we suggest that P. aeruginosa strains from CF patients categorized as intermediate or resistant to tobramycin according to the CLSI criteria should be retested with high-range Etest strips and recategorized using MENSURA interpretive criteria. CLSI breakpoints should still be followed when intravenous tobramycin is used in CF patients, particularly during the course of exacerbations.

Similarity of gene expression patterns in human alveolar macrophages in response to Pseudomonas aeruginosa and Burkholderia cepacia

To determine if differences in the severity of pulmonary infection in cystic fibrosis seen with late isolates of Pseudomonas aeruginosa and Burkholderia cepacia are associated with differences in the initial response of alveolar macrophages (AM) to these pathogens, we assessed gene expression changes in human AM in response to infection with a laboratory strain, early and late clinical isolates of P. aeruginosa, and B. cepacia. Analysis of gene expression changes at the RNA level using oligonucleotide microarrays, following exposure to laboratory P. aeruginosa strain PAK, showed significant (P < 0.01) >2.5-fold upregulation of 42 genes and >2.5-fold downregulation of 45 genes. The majority of the changes in gene expression involved genes as part of inflammatory pathways and signaling systems. Interestingly, similar responses were observed following exposure of AM to early and late clinical isolates of P. aeruginosa, as well as with B. cepacia, suggesting that the more severe clinical outcome of infections with late clinical isolates of P. aeruginosa or with B. cepacia cannot be explained by differences in the early interactions of these organisms with the human AM, as reflected by the similarity of gene expression changes in response to exposure of AM to these pathogens.

An essential role for non-bone marrow-derived cells in control of Pseudomonas aeruginosa pneumonia

MyD88 is an adapter protein required for the induction of proinflammatory cytokines by most Toll-like receptors (TLR), and Pseudomonas aeruginosa expresses ligands for multiple TLRs. MyD88(-/-) (KO) mice are highly susceptible to aerosolized P. aeruginosa, failing to elicit an early inflammatory response and permitting a 3-log increase in bacterial CFU in the lungs by 24 h after infection. We hypothesized that alveolar macrophages are the first cells to recognize and kill aerosolized P. aeruginosa in an MyD88-dependent fashion due to their location within the airways. To determine which cells in the lungs mediate MyD88-dependent defenses against P. aeruginosa, we generated radiation bone marrow (BM) chimeras between MyD88KO and wild-type (WT) mice. MyD88KO mice transplanted with MyD88KO BM (MyD88KO-->MyD88KO mice) displayed uncontrolled bacterial replication, whereas all other chimeras controlled the infection by 24 h. However, at 4 h, both MyD88KO-->MyD88KO and WT-->MyD88KO mice permitted intrapulmonary bacterial replication, whereas MyD88KO-->WT and WT-->WT mice did not, indicating that the source of BM had little impact on the early control of infection. Similarly, the genotype of the recipient rather than that of the BM donor determined early neutrophil recruitment to the lungs. Whereas intrapulmonary TNF-alpha and IL-1beta production were associated with WT BM, levels of the CXC chemokines MIP-2 and KC as well as GM-CSF were associated with recipient genotype. We conclude that lung parenchymal and BM-derived cells collaborate in the MyD88-dependent response to P. aeruginosa infection in the lungs in mice.

Normal and cystic fibrosis airway surface liquid homeostasis. The effects of phasic shear stress and viral infections

Mammalian airways normally regulate the volume of a thin liquid layer, the periciliary liquid (PCL), to facilitate the mucus clearance component of lung defense. Studies under standard (static) culture conditions revealed that normal airway epithelia possess an adenosine-regulated pathway that blends Na+ absorption and Cl- secretion to optimize PCL volume. In cystic fibrosis (CF), the absence of CF transmembrane conductance regulator results in a failure of adenosine regulation of PCL volume, which is predicted to initiate mucus stasis and infection. However, under conditions that mimic the phasic motion of the lung in vivo, ATP release into PCL was increased, CF ion transport was rebalanced, and PCL volume was restored to levels adequate for lung defense. This ATP signaling system was vulnerable, however, to insults that trigger CF bacterial infections, such as viral (respiratory syncytial virus) infections, which up-regulated extracellular ATPase activity and abolished motion-dependent ATP regulation of CF PCL height. These studies demonstrate (i) how the normal coordination of opposing ion transport pathways to maintain PCL volume is disrupted in CF, (ii) the hitherto unknown role of phasic motion in regulating key aspects of normal and CF innate airways defense, and (iii) that maneuvers directed at increasing motion-induced nucleotide release may be therapeutic in CF patients.

Cystic fibrosis lung disease: genetic influences, microbial interactions, and radiological assessment

Cystic fibrosis (CF) is a multiorgan disease caused by mutation of the CF transmembrane conductance regulator (CFTR) gene. Obstructive lung disease is the predominant cause of morbidity and mortality; thus, most efforts to improve outcomes are directed toward slowing or halting lung-disease progression. Current therapies, such as mucolytics, airway clearance techniques, bronchodilators, and antibiotics, aim to suppress airway inflammation and the processes that stimulate it, namely, retention and infection of mucus plaques at the airway surface. New approaches to therapy that aim to ameliorate specific CFTR mutations or mutational classes by restoring normal expression or function are being investigated. Because of its sensitivity in detecting changes associated with early airway obstruction and regional lung disease, high-resolution CT (HRCT) complements pulmonary function testing in defining disease natural history and measuring response to both conventional and experimental therapies. In this review, perspectives on the genetics and microbiology of CF provide a context for understanding the increasing importance of HRCT and other imaging techniques in assessing CF therapies.

Hypermutation is a key factor in development of multiple-antimicrobial resistance in Pseudomonas aeruginosa strains causing chronic lung infections

Pseudomonas aeruginosa is the most relevant pathogen producing chronic lung infections in patients with chronic underlying diseases such as cystic fibrosis (CF), bronchiectasis, and chronic obstructive pulmonary disease (COPD). Hypermutable (or mutator) P. aeruginosa strains, characterized by increased (up to 1,000-fold) spontaneous mutation rates due to alterations of the DNA mismatch repair (MMR) system have been found at high frequencies in the lungs of CF patients, but their role in other chronic processes is still unknown. Sixty-two P. aeruginosa isolates from 30 patients with underlying non-CF chronic respiratory diseases (22 with bronchiectasis and 8 with COPD) and documented chronic infection were studied. Antibiotic susceptibility profiles and mutation frequencies were determined, and complementation assays using the cloned wild-type mutS gene and molecular epidemiology studies (pulsed-field electrophoresis, [PFGE]) were performed with these strains. Thirty-three (53%) of the isolates were hypermutable, and 17 (57%) of the 30 patients were colonized by hypermutable strains. Strains from 11 of the 17 patients were found to be defective in the MMR mutS gene by complementation assays. Interpatient transmission of strains was ruled out by PFGE. Multiple-antimicrobial resistance was documented in 42% of the hypermutable strains in contrast to 0% resistance in the nonhypermutable strains (P < 0.0001). Hypermutable P. aeruginosa strains are extremely prevalent in chronic infections in contrast to what has been described in acute processes, suggesting a role of hypermutation in bacterial adaptation for long-term persistence. Furthermore, hypermutation is found to be a key factor for the development of multiple-antimicrobial resistance, and therefore these findings are expected to have important consequences for the treatment of chronic infections.

Anti-inflammatory therapy in cystic fibrosis

Inflammation plays a major role in the pathophysiology of lung disease in CF. This response is probably triggered primarily as a reaction to the inability of the affected lung to resist the invasion of the most common bacterial pathogens seen in this disease, namely, Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa. Debate continues as to whether there may or may not be a pre-inflammation of the lungs as part of the basic functional defect of CFTR. The anti-inflammatory treatment modalities most tested to date are: oral corticosteroids, effective but associated with significant long-term side effects, inhaled corticosteroids, so far not proven to be effective probably because of difficulty with absorption through the viscid surface secretions of the lung and ibuprofen, potentially effective but inhibited by the need to monitor drug levels invasively and potential gastrointestinal side effects. The most promising newcomer is macrolide antibiotics such as azithromycin acting as a long-term anti-inflammatory agent with an excellent safety profile.

An Immunoproteomic Approach for Identification of Clinical Biomarkers for Monitoring Disease

Circulating antibodies can be used to probe protein arrays of body fluids, prepared by two-dimensional gel electrophoresis, for antigenic biomarker detection. However, detected proteins, particularly low abundance antigens, often remain unidentifiable due to proteome complexity and limiting sample amounts. Using a novel enrichment approach exploiting patient antibodies for isolation of antigenic biomarkers, we demonstrate how immunoproteomic strategies can accelerate biomarker discovery. Application of this approach as a means of identifying biomarkers was demonstrated for cystic fibrosis (CF) lung disease by isolation and identification of inflammatory-associated autoantigens, including myeloperoxidase and calgranulin B from sputum of subjects with CF. The approach was also exploited for isolation of proteins expressed by the Pseudomonas aeruginosa strain PA01. Capture of PA01 antigens using circulating antibodies from CF subjects implicated in vivo expression of Pseudomonas proteins. All CF subjects screened, but not controls, were immunoreactive against immunocaptured Pseudomonas proteins, representing stress (GroES and ferric iron-binding protein HitA), immunosuppressive (thioredoxin), and alginate synthetase pathway (nucleoside-diphosphate kinase) proteins, implicating their clinical relevance as biomarkers of infection.

Differential regulation of cystic fibrosis transmembrane conductance regulator by interferon gamma in mast cells and epithelial cells

Cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent chloride channel in epithelial cells; recently, we identified it in mast cells. Previous work that we confirmed showed that interferon gamma (IFNgamma) down-regulated CFTR expression in epithelial cells (T84), but by contrast, we found that IFNgamma up-regulated CFTR mRNA and protein expression in rat and human mast cells. IFNgamma up-regulation of CFTR in mast cells was inhibited by p38 and extracellular signal-regulated kinase (ERK) kinase inhibitors but not a Janus tyrosine kinase (JAK)2 inhibitor, whereas in T84 cells IFNgamma-mediated down-regulation of CFTR was JAK2-dependent and ERK- and p38-independent. Furthermore, IFNgamma down-regulation of CFTR in T84 epithelial cells was STAT1-dependent, but up-regulation of CFTR in mast cells was STAT1-independent. Thus, differential regulatory pathways of CFTR expression in mast cells and epithelial cells exist that depend upon either p38/ERK or JAK/STAT pathways, respectively. Surprisingly, IFNgamma treatment of mast cells inhibited Cl(-) efflux, in contrast to up-regulation of CFTR/mRNA and protein expression. However, down-regulation of Cl(-) flux correlated with IFNgamma-mediated inhibition of mediator secretion. This and other work suggests that the effect of IFNgamma on CFTR expression in mast cells is important for their function.

Prospective evaluation of emerging bacteria in cystic fibrosis

BACKGROUND

Bacteria contribute considerably to the progression of lung disease in cystic fibrosis. In this prospective, multi-centre study, we aimed to evaluate the occurrence of emerging bacteria and the physicians' assessments of the clinical importance of these findings.

METHODS

Twelve CF centres (total number of patients: 1419) reported the detection of any Stenotrophomonas maltophilia, Burkholderia cepacia complex, MRSA, Alcaligenes xylosoxidans, Klebsiella species and Mycobacteria during an observation period of 6 months.

RESULTS

213 specimens with emerging bacteria were reported from 145 different patients. The proportion of patients with emerging bacteria differed between centres (3-38%, mean: 12.6%) and increased with age. The predominant bacterium was S. maltophilia (n=106 positive specimens), followed by Klebsiellae (n=36), B. cepacia complex (n=31), A. xylosoxidans (n=16), Mycobacteria (n=11), MRSA (n=11), and others (n=2). In many instances the same microorganisms had already been reported earlier, indicating intermittent or chronic colonisation. The clinical status was reported to be stable in 70% of patients, and antibiotic treatment was anticipated for 46% of positive specimens. Comparison of clinical data to age matched controls did not reveal any significant differences with regard to pulmonary and nutritional status prior to detection of emerging bacteria.

CONCLUSION

These data suggest a high variability between centres regarding the prevalence of emerging bacteria. Most patients maintained a stable clinical condition during the 6-month study period despite being colonised with emerging bacteria.

Genotype-phenotype correlation for pulmonary function in cystic fibrosis

BACKGROUND

Since the CFTR gene was cloned, more than 1000 mutations have been identified. To date, a clear relationship has not been established between genotype and the progression of lung damage. A study was undertaken of the relationship between genotype, progression of lung disease, and survival in adult patients with cystic fibrosis (CF).

METHODS

A prospective cohort of adult patients with CF and two CFTR mutations followed up in an adult cystic fibrosis unit was analysed. Patients were classified according to functional effects of classes of CFTR mutations and were grouped based on the CFTR molecular position on the epithelial cell surface (I-II/I-II, I-II/III-V). Spirometric values, progression of lung disease, probability of survival, and clinical characteristics were analysed between groups.

RESULTS

Seventy four patients were included in the study. Patients with genotype I-II/I-II had significantly lower current spirometric values (p < 0.001), greater loss of pulmonary function (p < 0.04), a higher proportion of end-stage lung disease (p < 0.001), a higher risk of suffering from moderate to severe lung disease (odds ratio 7.12 (95% CI 1.3 to 40.5)) and a lower probability of survival than patients with genotype I-II/III, I-II/IV and I-II/V (p < 0.001).

CONCLUSIONS

The presence of class I or II mutations on both chromosomes is associated with worse respiratory disease and a lower probability of survival.

Microcolony formation: a novel biofilm model of Pseudomonas aeruginosa for the cystic fibrosis lung

Pseudomonas aeruginosa colonizing the lung of cystic fibrosis patients is responsible for a decline in health and poor prognosis for these patients. Once established, growth of P. aeruginosa in microcolonies makes it very difficult to eradicate the organisms by antimicrobial treatment. An artificial sputum medium was developed to mimic growth of P. aeruginosa in the cystic fibrosis lung habitat and it was found that the organisms grew in tight microcolonies attached to sputum components. Several genes, such as algD, oprF and lasR but not fliC, were required for tight microcolony formation. Among the sputum components, amino acids, lecithin, DNA, salt and low iron were required for tight microcolony formation. Amino acids were also shown to be responsible for various other cystic-fibrosis-specific phenotypes of P. aeruginosa, such as diversification of colony morphology, alterations in LPS structure and hyperexpression of OprF. Since the amino acid content of sputum is elevated in severe lung disease, it is suggested that the tight microcolony biofilm is maintained in these conditions and that they contribute to the vicious cycle of disease severity and failure to eradicate the organism. Thus, growth of P. aeruginosa in artificial sputum medium is an appropriate model of chronic lung colonization and may be useful for evaluating therapeutic procedures and studying antibiotic-resistance mechanisms.