Gene Therapy: A Possible Alternative to CFTR Modulators?

Cystic fibrosis (CF) is a rare genetic disease that affects several organs, but lung disease is the major cause of morbidity and mortality. The gene responsible for CF, the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) gene, has been discovered in 1989. Since then, gene therapy i.e., defective gene replacement by a functional one, remained the ultimate goal but unfortunately, it has not yet been achieved. However, patients care and symptomatic treatments considerably increased CF patients' life expectancy ranging from 5 years old in the 1960s to 40 today. In the last decade, research works on CFTR protein structure and activity led to the development of new drugs which, by readdressing CFTR to the plasma membrane (correctors) or by enhancing its transport activity (potentiators), allow, alone or in combination, an improvement of CF patients' lung function and quality of life. While expected, it is not yet known whether taking these drugs from an early age and for years will improve the quality of life of CF patients in the long term and further increase their life expectancy. Besides, these molecules are not available (specific variants of CFTR) or accessible (national health policies) for all patients and there is still no curative treatment. Another alternative that could benefit from new technologies, such as gene therapy, is therefore still attractive, although it is not yet offered to patients. Faced with the development of new CFTR correctors and potentiators, the question arises as to whether there is still a place for gene therapy and this is discussed in this perspective.

Variant classifications, databases and genotype-phenotype correlations.

Because CFTR gene studies now represent one of the most frequent genetic analyses routinely performed worldwide, the number of rare CFTR variants identified in various clinical situations, regularly increases. To provide appropriate diagnosis and prognosis to CF patients as well as appropriate genetic counseling to families, the clinical impact and the phenotypic spectrum of variants identified by diagnostic techniques need to be characterized. Three complementary locus specific databases, called CFTR1, CFTR2 and CFTR-France were developed to address these issues. Besides, the growing knowledge of the CF pathophysiology and the technical evolution in molecular biology allowed to identify candidate modifier genes, regulatory loci, epigenetic profiles and trans-regulators that could help to refine genotype-phenotype correlations at the individual level. These different factors may contribute to the large phenotypic variability between patients with CF, even when they carry identical CFTR variants, regarding lung function, meconium ileus susceptibility or the risk for developing CFTR-related diabetes and liver disease. Finally, the availability of new therapies that target the CFTR protein for numbers of CF patients led to the identification of 'good' and 'poor' responders, thus raising questions of pharmacogenetics factors that may influence treatment efficiency as a novel feature of the complexity of CF patients' management. © 2020 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

[SLC6A14, a modifier gene in cystic fibrosis]. / SLC6A14, un gène modificateur dans la mucoviscidose.

Although cystic fibrosis is a monogenic disease, a considerable clinical phenotypic variability is observed in patients with the same CFTR mutations. Thanks to the development of new and powerful tools for carrying out genetic studies, several genes called "modifier genes" have been identified as being associated with the severity of the lung function disorder in cystic fibrosis patients. Among these genes, SLC6A14 may modulate the anti-infective response and epithelial integrity of the airways, thus providing a potential therapeutic target to improve the patient's lung function.

[New therapies for cystic fibrosis targeting the CFTR gene or the CFTR protein]. / Nouvelles thérapeutiques de la mucoviscidose ciblant le gène ou la protéine CFTR.

BACKGROUND: The treatment of cystic fibrosis has been symptom-based for a number of years. New therapies that aim to improve CFTR protein function are now emerging. CURRENT SCIENTIFIC KNOWLEDGE: The results of gene therapy has been modest but a recent clinical trial shows a positive effect on FEV1. Recent research has focused primarily on CFTR protein function. Significant respiratory improvement (an average 10% FEV1 increase and a decrease in the frequency of exacerbations) has been achieved with ivacaftor, a CFTR potentiator, in patients with gating mutations, resulting in its marketing authorization (in 2012 for the G551D mutation and in 2015 for rarer mutations). In phe508del homozygous patients, the combination of ivacaftor with a CFTR corrector (lumacaftor) has also led to respiratory improvement, albeit less impressive. The effectiveness of ataluren in patients with nonsense mutations is being evaluated. OUTLOOK: New CFTR correctors and potentiators are being developed. CFTR protein therapy could change the course of the disease but cost/effectiveness issues should not be overlooked. CONCLUSION: Ivacaftor can be prescribed in CF patients with a class 3 mutation from the age of 6 years. The Orkambi® will soon be available for homozygous phe508del patients from the age of 12 years.

[New therapeutic developments in cystic fibrosis]. / Nouvelles thérapeutiques ciblant le canal chlorure dans la mucoviscidose.

Since the discovery of chloride secretion by the Cystic Fibrosis Transport regulator CFTR in 1983, and CFTR gene in 1989, knowledge about CFTR synthesis, maturation, intracellular transfer and function has dramatically expanded. These discoveries have led to the distribution of CF mutations into 6 classes with different pathophysiological mechanisms. In this article we will explore the state of art on CFTR synthesis and its chloride secretion function. We will then explore the consequences of the 6 classes of mutations on CFTR protein function and we will describe the new therapeutic developments aiming at correcting these defects.

Vaccine coverage in CF children: A French multicenter study.

BACKGROUNDS: Recent reports have pointed the low vaccine coverage in patients with chronic diseases. Data are lacking in patients with cystic fibrosis (CF). Gaining more information on coverage both for mandatory vaccines and those more specifically recommended would help to optimize care of these patients. METHODS: Data were extracted from the "MucoFlu" study, which was a prospective study performed in 2009 in the 5 cystic fibrosis centers of the Paris metropolitan area. Data on mandatory and recommended vaccines in CF were collected in the health booklet and compared to the coverage of the general population. RESULTS: A total of 134 CF children were included. Vaccination coverage for mandatory vaccines was insufficient (DTPCaHi, conjugate pneumococcal, BCG, MMR and hepatitis B) at 1year of age with no catching-up with age in contrast to the general population. Approximately 66% of the children had immunization for seasonal influenza and 91% for 2009 pandemic flu. Coverage for vaccines specifically recommended in CF was low for hepatitis A, non conjugate pneumococcal and varicella. CONCLUSION: This study shows a defect in vaccine coverage for both routine immunization and vaccines more specifically recommended in CF.

[Challenges of personalized medicine for cystic fibrosis]. / Les enjeux de la médecine personnalisée appliquée à la mucoviscidose.

Personalized medicine, or P4 medicine for "Personalized", "Predictive", "Preventive" and "Participatory", is currently booming for cystic fibrosis, with the development of therapies targeting specific CFTR mutations. The various challenges of personalized medicine applied to cystic fibrosis issues are discussed in this paper.

Factors associated with humoral immune response to pandemic A/H1N1(v) 2009 influenza vaccine in cystic fibrosis.

Influenza vaccination is recommended in cystic fibrosis patients. The objective of this study was to assess the immunogenicity of vaccination against 2009 pandemic A/H1N1 influenza and to study the factors associated with the immune response in patients with cystic fibrosis. 122 patients with cystic fibrosis were enrolled in a prospective study and received 1 dose of 2009/H1N1v adjuvanted vaccine, or for children <2 years and lung-transplanted patients, two doses of non-adjuvanted 2009/H1N1v vaccine administered 21 days apart. Hemagglutination inhibition antibodies were assessed before and 21 days after vaccination and at least 6 months after vaccination. After vaccination, 85% of the patients had an influenza antibody titer ≥1:40 and 69% seroconverted. 13% of the transplanted patients seroconverted compared with 72% of the non-transplanted patients. In this latter group, non-adjuvanted vaccine and low body mass index were independently associated with lower response to vaccination. 86% of the non-transplanted patients with normal BMI and receiving adjuvanted vaccine seroconverted. Persistence of seroprotection 10 months after vaccination was found in 50% of the patients. In patients with cystic fibrosis, malnutrition and receipt of non-adjuvanted vaccine were associated with lower immune response to pandemic influenza vaccination. Our data also suggest a potential defect in the immune response to influenza vaccination of patients with cystic fibrosis and raise the question of whether a different immunization strategy is needed.

[Why use long-term macrolide therapy in pediatric pulmonology?]. / Pourquoi utiliser les macrolides au long cours en pneumologie pédiatrique ?

Macrolides are well-known antibiotics exerting antimicrobial as well as anti-inflammatory and immunomodulatory effects. Since the observation of a dramatic improvement in lung disease and survival in patients with diffuse panbronchiolitis, macrolides have been used over the long term in several chronic respiratory diseases. This review describes the results of trials that have evaluated long-term macrolides in the treatment of cystic fibrosis, non-cystic fibrosis bronchiectasis, and asthma, particularly focusing on the impact on children. It also provides new insights on the potential effects of macrolides on diffuse parenchymal lung diseases.

Azithromycin analogue CSY0073 attenuates lung inflammation induced by LPS challenge.

BACKGROUND AND PURPOSE: Azithromycin is a macrolide antibiotic with anti-inflammatory and immunomodulating effects. Long-term azithromycin therapy in patients with chronic lung diseases such as cystic fibrosis has been associated with increased antimicrobial resistance, emergence of hypermutable strains, ototoxicity and cardiac toxicity. The aim of this study was to assess the anti-inflammatory effects of the non-antibiotic azithromycin derivative CSY0073. EXPERIMENTAL APPROACH: We compared the effects of CSY0073 with those of azithromycin in experiments on bacterial cultures, Pseudomonas aeruginosa biofilm, lung cells and mice challenged intranasally with P. aeruginosa LPS. KEY RESULTS: In contrast to azithromycin, CSY0073 did not inhibit the growth of P. aeruginosa, Staphylococcus aureus or Haemophilus influenzae and had no effect on an established P. aeruginosa biofilm. Bronchoalveolar lavage (BAL) fluids and lung homogenates collected after the LPS challenge in mice showed that CSY0073 and azithromycin (200 mg·kg(-1), i.p.) decreased neutrophil counts at 24 h and TNF-α, CXCL1 and CXCL2 levels in the BAL fluid after 3 h and IL-6, CXCL2 and IL-1ß levels in the lung after 3 h compared with the vehicle. However, only azithromycin reduced IL-1ß levels in the lung 24 h post LPS challenge. CSY0073 and azithromycin similarly diminished the production of pro-inflammatory cytokines by macrophages, but not lung epithelial cells, exposed to P. aeruginosa LPS. CONCLUSIONS AND IMPLICATIONS: Unlike azithromycin, CSY0073 had no antibacterial effects but it did have a similar anti-inflammatory profile to that of azithromycin. Hence, CSY0073 may have potential as a long-term treatment for patients with chronic lung diseases.

[National consensus regarding the prescription of inhaled corticosteroids in cystic fibrosis]. / Consensus national sur les modalités de prescription des corticoïdes inhalés dans la mucoviscidose.

UNLABELLED: The conditions for the prescription of inhaled steroids (ISs) in cystic fibrosis (CF) are not well established. AIM: To propose a formalized consensus agreement regarding the prescription of ISs in this disease. MATERIAL AND METHODS: Application of the Delphi method in five thematic fields: indications, non-indications, dosage, precautions for use, and treatment follow-up. RESULTS: Thirty of forty-nine (61 %) reference CF centers in France participated in the process, which comprised three rounds. Experts strongly agreed that ISs are indicated in the presence of pulmonary manifestations with wheezing, personal history of atopy, and/or bronchial hyper-responsiveness. In contrast, ISs are not indicated as first-line therapy for allergic bronchopulmonary aspergillosis. Strong agreement was reached regarding the daily dose of ISs, which should be similar to what is given in asthma and adapted to control symptoms so as to prescribe the smallest possible dose. Increasing the frequency of bacterial and fungal sputum analyses and eye (cataract) assessments was not deemed necessary. However, in case of prolonged (>6months) use of high-dose ISs, monitoring bone mineral density and the hypothalamic-pituitary-adrenal axis, in particular if itraconazole is concomitantly prescribed, was recommended. CONCLUSION: This consensus statement defines a perimeter for the prescription of ISs in CF, with the aim of limiting their prescription (until new data are available).

Massive splenomegaly and pancytopenia reuealing sarcoidosis in a child.

Clinical presentation of sarcoidosis in children is very variable and dependant upon age. Herein, we report the first association of massive splenomegaly and pancytopenia as the revealing mode of sarcoidosis in an 8-year-old girl who, despite bone marrow involvement, had a remarkable good outcome following steroid therapy.

[Genetics and modifier genes, atypical and rare forms]. / Génétique et gènes modificateurs, formes atypiques et rares.

Cystic fibrosis (CF) is defined as the most common life shortening genetic disorder in the Caucasian populations. The cloning of the gene responsible for the disease - the CFTR (Cystic Fibrosis Transmembrane conductance Regulator) gene - twenty years ago has greatly improved our knowledge of the pathophysiology of CF. That disease is characterized by a highly phenotypic variability and the CFTR mutations cannot explain all the variability observed in the disease severity. The possible influence of the environment and modifier genes has therefore been evocated. Several genetic variants coding for genes involved in the physiopathology of the disease have been studied, like genes involve in the immunity and the inflammatory response. Some of these genes have indeed been shown to influence the disease severity. A new approach has also been developed, analyzing the whole genome. This review summarizes the genetic basis of CF in its classical and atypical forms, as well as the work performed in the field of modifier genes.

The role of LTA4H and ALOX5AP genes in the risk for asthma in Latinos.

BACKGROUND: Leukotrienes play an important role in allergic and inflammatory diseases, but reports on the involvement of arachidonate 5-lipoxygenase-activating protein (ALOX5AP) and leukotriene A(4) hydrolase (LTA4H) in asthma have been inconclusive. OBJECTIVE: To determine whether polymorphisms in ALOX5AP and LTA4H genes are risk factors for asthma in two different Latino groups: Mexicans and Puerto Ricans. METHODS: The LTA4H gene was sequenced in individuals from both groups to identify novel polymorphisms. Single-nucleotide polymorphisms (SNPs) in the ALOX5AP and LTA4H genes were analysed for associations with asthma and asthma-related phenotypes in 687 parent-child trios of Mexican and Puerto Rican origin. RESULTS: In LTA4H, five previously unknown polymorphisms were identified. Two SNPs within LTA4H (rs17525488 and rs2540493) were protective for asthma in Latinos (P=0.007 and 0.05, respectively). Among the Mexican patients, LTA4H polymorphisms were associated with baseline lung function and IgE levels. For ALOX5AP, the minor allele at SNP rs10507391 was associated with protection from asthma (odds ratio=0.78, P=0.02) and baseline lung function (P=0.018) in Puerto Ricans. A gene-gene interaction was identified between LTA4H (rs17525488) and ALOX5AP (rs10507391), (P=0.003, in the combined sample). CONCLUSION: Our results support the role of LTA4H and ALOX5AP variants as risk factors for asthma in Latino populations.

The very low penetrance of cystic fibrosis for the R117H mutation: a reappraisal for genetic counselling and newborn screening.

BACKGROUND: Cystic fibrosis (CF) is caused by compound heterozygosity or homozygosity of CF transmembrane conductance regulator gene (CFTR) mutations. Phenotypic variability associated with certain mutations makes genetic counselling difficult, notably for R117H, whose disease phenotype varies from asymptomatic to classical CF. The high frequency of R117H observed in CF newborn screening has also introduced diagnostic dilemmas. The aim of this study was to evaluate the disease penetrance for R117H in order to improve clinical practice. METHODS: The phenotypes in all individuals identified in France as compound heterozygous for R117H and F508del, the most frequent CF mutation, were described. The allelic prevalences of R117H (p(R117H)), on either intron 8 T5 or T7 background, and F508del (p(F508del)) were determined in the French population, to permit an evaluation of the penetrance of CF for the [R117H]+[F508del] genotype. RESULTS: Clinical details were documented for 184 [R117H]+[F508del] individuals, including 72 newborns. The disease phenotype was predominantly mild; one child had classical CF, and three adults' severe pulmonary symptoms. In 5245 healthy adults, p(F508del) was 1.06%, p(R117H;T7) 0.27% and p(R117H;T5)<0.01%. The theoretical number of [R117H;T7]+[F508del] individuals in the French population was estimated at 3650, whereas only 112 were known with CF related symptoms (3.1%). The penetrance of classical CF for [R117H;T7]+[F508del] was estimated at 0.03% and that of severe CF in adulthood at 0.06%. CONCLUSIONS: These results suggest that R117H should be withdrawn from CF mutation panels used for screening programmes. The real impact of so-called disease mutations should be assessed before including them in newborn or preconceptional carrier screening programmes.

[Pneumocystis jiroveci pneumonia during prolonged corticosteroid therapy in an immunocompetent infant]. / Pneumonie àPneumocystis jiroveci au cours d'une corticothérapie prolongée chez un nourrisson immunocompétent.

INTRODUCTION: Pneumocystis jiroveci (PJ) infection is rare in infants and is suggestive of primary or secondary immunodeficiency. We report on a case of severe PJ pneumonia in an immunocompetent infant after prolonged corticosteroid treatment. CASE REPORT: A 5 1/2 month-old girl presented with hypoxemic respiratory distress. Her medical record was remarkable only for a bulky parotid haemangioma, which was treated with prolonged oral corticosteroid therapy. The chest X-ray showed a mixed alveolar-interstitial pattern, and bronchoalveolar lavage revealed the presence of PJ. A favourable outcome was obtained after three weeks of intravenous trimethoprim-sulfamethoxazole treatment. CONCLUSION: PJ infection should be suspected in infants presenting with progressive respiratory distress associated with a mixed alveolar-interstitial pattern. Its potential seriousness justifies prophylactic therapy during prolonged immunosuppressive treatment (chemotherapy, corticosteroid treatment).