Advances in Lung Transplantation for Patients Who Have Cystic Fibrosis

Pulmonary infections in transplant recipients

PURPOSE OF REVIEW

Hematopoietic stem cell as well as solid-organ transplantation is being carried out with increasing frequency throughout the world. Lower respiratory tract infections (LRTIs) remain a common life-threatening complication faced by the transplant recipients. The purpose of this review is to provide up-to-date information on pulmonary infections among the transplant recipients, especially emphasizing the endemicity of microorganisms, epidemiology, work-up of infections, and principles of their management.

RECENT FINDINGS

A lower respiratory tract infection such as pneumonia is the most frequent of all the infections and is associated with high morbidity and mortality. Factors increasing the risk of pulmonary infections include surgical techniques, immune status, chemoradiotherapy, alloimmune mechanisms between the host and the graft, and the environment. A high degree of suspicion, computed tomography (CT) scan of the chest, and flexible bronchoscopy are required in most to establish the diagnosis.

SUMMARY

Proper management of LRTI in transplant recipients requires a high degree of suspicion, thorough knowledge of the epidemiology and endemicity of the suspected organisms, CT scan of the chest, and expertise at bronchoscopy. Utmost teamwork among transplant physicians, infectious disease specialist, and bronchoscopist is essential.

Cystic fibrosis

Cystic fibrosis is the most common lethal genetic disease in white populations. The outlook for patients with the disease has improved steadily over many years, largely as a result of earlier diagnosis, more aggressive therapy, and provision of care in specialised centres. Researchers now have a more complete understanding of the molecular-biological defect that underlies cystic fibrosis, which is leading to new approaches to treatment. One of these treatments, hypertonic saline, is already in use, whereas others are in advanced stages of development. We review clinical care for cystic fibrosis and discuss recent advances in the understanding of its pathogenesis, implementation of screening of neonates, and development of therapies aimed at treating the basic defect.

What's new in cystic fibrosis? From treating symptoms to correction of the basic defect

Chronic relentless lung infection and pancreatic insufficiency are the cardinal features of cystic fibrosis (CF), a life-shortening autosomal recessive disease. Mutations in the 'cystic fibrosis transmembrane conductance regulator' (CFTR) are currently classified into five groups according to their repercussion on CFTR protein synthesis and its chloride channel function. Stop codon mutations (class I) result in a truncated nonfunctional CFTR, class II mutations consist of aberrantly folded CFTR protein that is degraded by the cell quality control system, while class III mutations lead to defective regulation of the CFTR protein and, consequently, the absence of CFTR function. These three classes usually lead to a classic CF phenotype with pancreatic insufficiency. CFTR mutations that lead to defective chloride conductance are grouped together in class IV. Class V mutations interfere with normal transcription, thereby reducing the amount of otherwise normal CFTR. These latter two classes are mostly associated with a milder expression of the disease. In the absence of CFTR function, unrestrained Na+ absorption and the failure of active Cl- secretion lead to a decreased airway surface liquid (ASL) volume and subsequent failure of normal mucociliary clearance. This review highlights recent therapeutic strategies that either target the underlying defect or the early steps in CF pathophysiology. To date, gene therapy has failed to demonstrate a clinical benefit after repeated administration. Mutation-specific chloride channel correction pharmacotherapy is currently being developed, an example of which is PTC124, a new chemical compound that selectively induces read-through of premature stop codons. However, clinical efficacy for most of the compounds still has to be proven in large clinical trials. The positive effect of nebulised hypertonic saline on mucociliary clearance is based on the restoration of ASL height. Recent advances in the current treatment of lung infection and inflammation are highlighted in this review. Lung transplantation should be considered in terminally ill patients, but the timing of the transplantation is crucial: transplanting too early shortens survival, while transplanting too late results in patients dying on the waiting list.