Mark A. Chilvers

Efficacy and Safety of Ivacaftor in Patients Aged 6 to 11 Years with Cystic Fibrosis with a G551D Mutation

RATIONALE Ivacaftor (VX-770), a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator, has been shown to improve lung function, pulmonary exacerbation rate, respiratory symptoms, and weight gain compared with placebo in patients with cystic fibrosis aged 12 years or older with a G551D-CFTR mutation. OBJECTIVES This randomized, double-blind, placebo-controlled trial evaluated ivacaftor in patients with cystic fibrosis aged 6-11 years with a G551D-CFTR mutation on at least one allele. METHODS Patients were randomly assigned to receive ivacaftor administered orally at 150 mg (n = 26) or placebo (n = 26) every 12 hours for 48 weeks in addition to existing prescribed cystic fibrosis therapies. MEASUREMENTS AND MAIN RESULTS Despite near-normal mean baseline values in FEV1, patients receiving ivacaftor had a significant increase in percent predicted FEV1 from baseline through Week 24 versus placebo group (treatment effect, 12.5 percentage points; P < 0.001). Effects on pulmonary function were evident by 2 weeks, and a significant treatment effect was maintained through Week 48. Patients treated with ivacaftor gained, on average, 2.8 kg more than those receiving placebo at Week 48 (P < 0.001). The change from baseline through Week 48 in the concentration of sweat chloride, a measure of CFTR activity, with ivacaftor was -53.5 mmol/L (P < 0.001) versus placebo. The incidence of adverse events was similar in the two groups. CONCLUSIONS In patients who are younger and healthier than those in previously studied populations, ivacaftor demonstrated a significant improvement in pulmonary function, weight, and CFTR activity compared with placebo. Clinical trial registered with www.clinicaltrials.gov (NCT00909727).

Inconclusive Diagnosis of Cystic Fibrosis After Newborn Screening

OBJECTIVES: To prospectively study infants with an inconclusive diagnosis of cystic fibrosis (CF) identified by newborn screening (NBS; “CF screen positive, inconclusive diagnosis” [CFSPID]) for disease manifestations. METHODS: Infants with CFSPID and CF based on NBS from 8 CF centers were prospectively evaluated and monitored. Genotype, phenotype, repeat sweat test, serum trypsinogen, and microbiology data were compared between subjects with CF and CFSPID and between subjects with CFSPID who did (CFSPID→CF) and did not (CFSPID→CFSPID) fulfill the criteria for CF during the first 3 years of life. RESULTS: Eighty-two subjects with CFSPID and 80 subjects with CF were enrolled. The ratio of CFSPID to CF ranged from 1:1.4 to 1:2.9 in different centers. CFTR mutation rates did not differ between groups; 96% of subjects with CFSPID and 93% of subjects with CF had 2 mutations. Subjects with CFSPID had significantly lower NBS immunoreactive trypsinogen (median [interquartile range]:77 [61–106] vs 144 [105–199] μg/L; P < .0001) than did subjects with CF. Pseudomonas aeruginosa and Stenotrophomonas maltophilia were isolated in 12% and 5%, respectively, of subjects with CFSPID. CF was diagnosed in 9 of 82 (11%) subjects with CFSPID (genotype and abnormal sweat chloride = 3; genotype alone = 4; abnormal sweat chloride only = 2). Sweat chloride was abnormal in CFSPID→CF patients at a mean (SD) age of 21.3 (13.8) months. CFSPID→CF patients had significantly higher serial sweat chloride (P < .0001) and serum trypsinogen (P = .009) levels than did CFSPID→CFSPID patients. CONCLUSIONS: A proportion of infants with CFSPID will be diagnosed with CF within the first 3 years. These findings underscore the need for clinical monitoring, repeat sweat testing at age 2 to 3 years, and extensive genotyping.

TLR5 as an Anti-Inflammatory Target and Modifier Gene in Cystic Fibrosis

New treatments are needed to improve the health of people with cystic fibrosis (CF). Reducing lung-damaging inflammation is likely to be beneficial, but specific anti-inflammatory targets have not been identified. By combining cellular immunology with a population-based genetic modifier study, we examined TLR5 as an anti-inflammatory target and modifier gene in CF. Using two pairs of human CF and control airway epithelial cells, we demonstrated that the TLR5–flagellin interaction is a major mediator of inflammation following exposure to Pseudomonas aeruginosa. To validate TLR5 as an anti-inflammatory target, we analyzed the disease modifying effects of the TLR5 c.1174C>T single nucleotide polymorphism (rs5744168) in a large cohort of CF patients (n = 2219). rs5744168 encodes a premature stop codon and the T allele is associated with a 45.5–76.3% reduction in flagellin responsiveness (p < 0.0001). To test the hypothesis that reduced TLR5 responsiveness would be associated with improved health in CF patients, we examined the relationship between rs5744168 and two clinical phenotypes: lung function and body weight. Adults with CF carrying the TLR5 premature stop codon (CT or TT genotype) had a higher body mass index than did CF patients homozygous for the fully functional allele (CC genotype) (p = 0.044); however, similar improvements in lung function associated with the T allele were not statistically significant. Although follow-up studies are needed to confirm the impact of TLR5 on nutritional status, this translational research provides evidence that genetic variation in TLR5 resulting in reduced flagellin responsiveness is associated with improved health indicators in adults with CF.

Inflammasome-Mediated IL-1β Production in Humans with Cystic Fibrosis

Background Inflammation and infection are major determinants of disease severity and consequently, the quality of life and outcome for patients with cystic fibrosis (CF). Interleukin-1 beta (IL-1β) is a key inflammatory mediator. Secretion of biologically active IL-1β involves inflammasome-mediated processing. Little is known about the contribution of IL-1β and the inflammasomes in CF inflammatory disease. This study examines inflammasome-mediated IL-1β production in CF bronchial epithelial cell lines and human patients with CF. Results Bronchial epithelial cell lines were found to produce negligible amounts of basal or stimulated IL-1β compared to hematopoeitic cells and they did not significantly upregulate caspase-1 activity upon inflammasome stimulation. In contrast, peripheral blood mononuclear cells (PBMCs) from both CF and healthy control subjects produced large amounts of IL-1β and strongly upregulated caspase-1 activity upon inflammasome stimulation. PBMCs from CF patients and controls displayed similar levels of caspase-1 activation and IL-1β production when stimulated with inflammasome activators. This IL-1β production was dependent on NF-κB activity and could be enhanced by priming with LPS. Finally, chemical inhibition of CFTR activity in control PBMCs and THP-1 cells did not significantly alter IL-1β or IL-8 production in response to P. aeruginosa. Conclusion Hematopoeitic cells appear to be the predominant source of inflammasome-induced pro-inflammatory IL-1β in CF. PBMCs derived from CF subjects display preserved inflammasome activation and IL-1β secretion in response to the major CF pathogen Pseudomonas aeruginosa. However, our data do not support the hypothesis that increased IL-1β production in CF subjects is due to an intrinsic increase in NF-κB activity through loss of CFTR function.

Atypical Activation of the Unfolded Protein Response in Cystic Fibrosis Airway Cells Contributes to p38 MAPK-Mediated Innate Immune Responses

Inflammatory lung disease is the major cause of morbidity and mortality in cystic fibrosis (CF); understanding what produces dysregulated innate immune responses in CF cells will be pivotal in guiding the development of novel anti-inflammatory therapies. To elucidate the molecular mechanisms that mediate exaggerated inflammation in CF following TLR signaling, we profiled global gene expression in immortalized human CF and non-CF airway cells at baseline and after microbial stimulation. Using complementary analysis methods, we observed a signature of increased stress levels in CF cells, specifically characterized by endoplasmic reticulum (ER) stress, the unfolded protein response (UPR), and MAPK signaling. Analysis of ER stress responses revealed an atypical induction of the UPR, characterized by the lack of induction of the PERK–eIF2α pathway in three complementary model systems: immortalized CF airway cells, fresh CF blood cells, and CF lung tissue. This atypical pattern of UPR activation was associated with the hyperinflammatory phenotype in CF cells, as deliberate induction of the PERK–eIF2α pathway with salubrinal attenuated the inflammatory response to both flagellin and Pseudomonas aeruginosa. IL-6 production triggered by ER stress and microbial stimulation were both dependent on p38 MAPK activity, suggesting a molecular link between both signaling events. These data indicate that atypical UPR activation fails to resolve the ER stress in CF and sensitizes the innate immune system to respond more vigorously to microbial challenge. Strategies to restore ER homeostasis and normalize the UPR activation profile may represent a novel therapeutic approach to minimize lung-damaging inflammation in CF.

Burkholderia Species Infections in Patients with Cystic Fibrosis in British Columbia, Canada. 30 Years’ Experience

RATIONALE We have been collecting Burkholderia species bacteria from patients with cystic fibrosis (CF) for the last 30 years. During this time, our understanding of their multispecies taxonomy and infection control has evolved substantially. OBJECTIVES To evaluate the long-term (30 year) epidemiology and clinical outcome of Burkholderia infection in CF, and fully define the risks associated with infection by each species. METHODS Isolates from Burkholderia-positive patients (n=107) were speciated and typed annually for each infected patient. Microbiological and clinical data were evaluated by thorough review of patient charts, and statistical analyses performed to define significant epidemiological factors. MEASUREMENTS AND MAIN RESULTS Before 1995, the majority of new Burkholderia infections were caused by epidemic clones of Burkholderia cenocepacia. After implementation of new infection control measures in 1995, Burkholderia multivorans became the most prevalent species. Survival analysis showed that patients with CF infected with B. cenocepacia had a significantly worse outcome than those with B. multivorans, and a novel finding was that, after Burkholderia infection, the prognosis for females was significantly worse than for males. CONCLUSIONS B. multivorans and B. cenocepacia have been the predominant Burkholderia species infecting people with CF in Vancouver. The implementation of infection control measures were successful in preventing new acquisition of epidemic strains of B. cenocepacia, leaving nonclonal B. multivorans as the most prevalent species. Historically, survival after infection with B. cenocepacia has been significantly worse than B. multivorans infection, and, of new significance, we show that females tend toward worse clinical outcomes.

Long-term comparative trial of two different physiotherapy techniques; postural drainage with percussion and autogenic drainage, in the treatment of cystic fibrosis

In N. America, over the past decade, various airway clearance techniques (ACT) have been introduced for the treatment of cystic fibrosis (CF). We hypothesized that autogenic drainage (AD), an ACT developed in Belgium would be as effective as postural drainage with percussion (PD) in treating patients with CF.

Analysis of ependymal ciliary beat pattern and beat frequency using high speed imaging: comparison with the photomultiplier and photodiode methods

BackgroundThe aim of this study was to compare beat frequency measurements of ependymal cilia made by digital high speed imaging to those obtained using the photomultiplier and modified photodiode techniques. Using high speed video analysis the relationship of the power and recover strokes was also determined.MethodsCiliated strips of ependyma attached to slices from the brain of Wistar rats were incubated at 30°C and observed using a ×50 water immersion lens. Ciliary beat frequency was measured using each of the three techniques: the high speed video, photodiode and photomultiplier. Readings were repeated after 30 minutes incubation at 37°C. Ependymal cilia were observed in slow motion and the precise movement of cilia during the recovery stroke relative to the path travelled during the power stroke was measured.ResultsThe mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 30°C were 27.7 (26.6 to 28.8), 25.5 (24.4 to 26.6) and 20.8 (20.4 to 21.3) Hz, respectively. The mean (95% confidence intervals) beat frequencies determined by the high speed video, photomultiplier and photodiode at 37°C were 36.4 (34 to 39.5), 38.4 (36.8 to 39.9) and 18.8 (16.9 to 20.5) Hz. The inter and intra observer reliability for measurement of ciliary beat frequency was 3.8% and 1%, respectively. Ependymal cilia were observed to move in a planar fashion during the power and recovery strokes with a maximum deviation to the right of the midline of 12.1(11.8 to 13.0)° during the power stroke and 12.6(11.6 to 13.6)° to the left of the midline during the recovery stroke.ConclusionThe photodiode technique greatly underestimates ciliary beat frequency and should not be used to measure ependymal ciliary beat frequency at the temperatures studied. Ciliary beat frequency from the high speed video and photomultiplier techniques cannot be used interchangeably. Ependymal cilia had minimal deviation to the right side during their power stroke and to the left during the recovery stroke.

Randomized controlled trial of biofilm antimicrobial susceptibility testing in cystic fibrosis patients

This study aimed to determine whether antimicrobial susceptibility testing of Pseudomonas aeruginosa grown as a biofilm, rather than planktonically, improves efficacy of antibiotic treatment for pulmonary exacerbations. This was a multicenter randomized, double-blind controlled trial of 14 days of intravenous antibiotic treatment for pulmonary exacerbations chosen based on conventional vs. biofilm antimicrobial susceptibility results in CF patients with chronic P. aeruginosa infection. There were 74 exacerbations in 39 patients. A total of 46% (12/26) exacerbations in the conventional group compared to 40% (19/48) exacerbations in the biofilm group achieved a ≥3 log drop in P. aeruginosa sputum density (difference -0.03, 95% CI -0.5 to 0.4, p=0.9). Lung function improvements were similar in both groups. Biofilm antimicrobial susceptibility testing did not lead to improved microbiological or clinical outcomes compared to conventional methods in the treatment of pulmonary exacerbations in CF patients with chronic P. aeruginosa.

Evaluation of a Multidimensional Cystic Fibrosis Transition Program: A Quality Improvement Initiative

The adequate preparation of cystic fibrosis (CF) youth for the transfer from pediatric to adult-based health care services is essential to meet the needs of this changing population. This paper describes the evolution of a transition clinic for patients with CF into a multidimensional quality improvement transition initiative. Three transition interventions (a patient transition clinical pathway; collaboration with the adult clinic; and a tool to measure transfer readiness) were sequentially implemented and evaluated. Each was found to be a valuable addition to a comprehensive transition protocol and today are endorsed as part of transition best practices.