Lack of association of Aspergillus colonization with the development of bronchiolitis obliterans syndrome in lung transplant recipients: An international cohort study

Fungal Tracheobronchitis in Lung Transplant Recipients: Incidence and Utility of Diagnostic Markers

Fungal tracheobronchitis caused by Aspergillus and Candida spp. is a recognized complication after lung transplantation, but knowledge of the incidence of Candida tracheobronchitis is lacking. The diagnosis relies on fungal cultures in bronchoalveolar lavage fluid (BALF), but cultures have low specificity. We aimed to evaluate the one-year incidence of fungal tracheobronchitis after lung transplantation and to assess the utility of diagnostic markers in serum and BALF to discriminate fungal tracheobronchitis from colonization. Ninety-seven consecutively included adult lung-transplant recipients were prospectively followed. BALF and serum samples were collected at 1, 3 and 12 months after transplantation and analyzed for betaglucan (serum and BALF), neutrophils (BALF) and galactomannan (BALF). Fungal tracheobronchitis was defined according to consensus criteria, modified to include Candida as a mycologic criterion. The cumulative one-year incidence of Candida and Aspergillus tracheobronchitis was 23% and 16%, respectively. Neutrophils of >75% of total leukocytes in BALF had 92% specificity for Candida tracheobronchitis. The area under the ROC curves for betaglucan and galactomannan in BALF to discriminate Aspergillus tracheobronchitis from colonization or no fungal infection were high (0.86 (p < 0.0001) and 0.93 (p < 0.0001), respectively). To conclude, the one-year incidence of fungal tracheobronchitis after lung transplantation was high and dominated by Candida spp. Diagnostic markers in BALF could be useful to discriminate fungal colonization from tracheobronchitis.

Fungal infections in lung transplantation

Lung transplant is a potential life-saving procedure for chronic lung diseases. Lung transplant recipients (LTRs) are at the greatest risk for invasive fungal infections (IFIs) among solid organ transplant (SOT) recipients because the allograft is directly exposed to fungi in the environment, airway and lung host defenses are impaired, and immunosuppressive regimens are particularly intense. IFIs occur within a year of transplant in 3-19% of LTRs, and they are associated with high mortality, prolonged hospital stays, and excess healthcare costs. The most common causes of post-LT IFIs are Aspergillus and Candida spp.; less common pathogens are Mucorales, other non-Aspergillus moulds, Cryptococcus neoformans, Pneumocystis jirovecii, and endemic mycoses. The majority of IFIs occur in the first year following transplant, although later onset is observed with prolonged antifungal prophylaxis. The most common manifestations of invasive mould infections (IMIs) include tracheobronchial (particularly at anastomotic sites), pulmonary and disseminated infections. The mortality rate of tracheobronchitis is typically low, but local complications such as bronchomalacia, stenosis and dehiscence may occur. Mortality rates associated with lung and disseminated infections can exceed 40% and 80%, respectively. IMI risk factors include mould colonization, single lung transplant and augmented immunosuppression. Candidiasis is less common than mould infections, and manifests as bloodstream or other non-pulmonary invasive candidiasis; tracheobronchial infections are encountered uncommonly. Risk factors for and outcomes of candidiasis are similar to those of non lung transplant recipients. There is evidence that IFIs and fungal colonization are risk factors for allograft failure due to chronic rejection. Mould-active azoles are frontline agents for treatment of IMIs, with local debridement as needed for tracheobronchial disease. Echinocandins and azoles are treatments for invasive candidiasis, in keeping with guidelines in other patient populations. Antifungal prophylaxis is commonly administered, but benefits and optimal regimens are not defined. Universal mould-active azole prophylaxis is used most often. Other approaches include targeted prophylaxis of high-risk LTRs or pre-emptive therapy based on culture or galactomannan (GM) (or other biomarker) results. Prophylaxis trials are needed, but difficult to perform due to heterogeneity in local epidemiology of IFIs and standard LT practices. The key to devising rational strategies for preventing IFIs is to understand local epidemiology in context of institutional clinical practices.

The lung microbiome in lung transplantation

Culture-independent study of the lower respiratory tract after lung transplantation has enabled an understanding of the microbiome - that is, the collection of bacteria, fungi, and viruses, and their respective gene complement - in this niche. The lung has unique features as a microbial environment, with balanced entry from the upper respiratory tract, clearance, and local replication. There are many pressures impacting the microbiome after transplantation, including donor allograft factors, recipient host factors such as underlying disease and ongoing exposure to the microbe-rich upper respiratory tract, and transplantation-related immunosuppression, antimicrobials, and postsurgical changes. To date, we understand that the lung microbiome after transplant is dysbiotic; that is, it has higher biomass and altered composition compared to a healthy lung. Emerging data suggest that specific microbiome features may be linked to host responses, both immune and non-immune, and clinical outcomes such as chronic lung allograft dysfunction (CLAD), but many questions remain. The goal of this review is to put into context our burgeoning understanding of the lung microbiome in the postlung transplant patient, the interactions between microbiome and host, the role the microbiome may play in post-transplant complications, and critical outstanding research questions.

Chronic Lung Allograft Dysfunction: Evolving Concepts and Therapies

The primary factor that limits long-term survival after lung transplantation is chronic lung allograft dysfunction (CLAD). CLAD also impairs quality of life and increases the costs of medical care. Our understanding of CLAD continues to evolve. Consensus definitions of CLAD and the major CLAD phenotypes were recently updated and clarified, but it remains to be seen whether the current definitions will lead to advances in management or impact care. Understanding the potential differences in pathogenesis for each CLAD phenotype may lead to novel therapeutic strategies, including precision medicine. Recognition of CLAD risk factors may lead to earlier interventions to mitigate risk, or to avoid risk factors all together, to prevent the development of CLAD. Unfortunately, currently available therapies for CLAD are usually not effective. However, novel therapeutics aimed at both prevention and treatment are currently under investigation. We provide an overview of the updates to CLAD-related terminology, clinical phenotypes and their diagnosis, natural history, pathogenesis, and potential strategies to treat and prevent CLAD.

Risk of Lung Allograft Dysfunction Associated With Aspergillus Infection

We sought to determine whether invasive aspergillosis (IA) during the first year after lung transplantation increased the risk of chronic lung allograft dysfunction (CLAD).

Methods

We retrospectively reviewed the records of 191 patients who underwent lung transplantation at our institution between January 2013 and December 2017. Screening for Aspergillus was with bronchial aspirates, bronchoalveolar lavage if indicated or during surveillance bronchoscopy, radiography, and computed tomography. We used Fine and Gray multivariable regression to identify potential risk factors for CLAD.

Results

During the first posttransplant year, 72 patients had at least 1 deep-airway sample positive for Aspergillus; 63 were classified as having IA and were included in the study. Median number of endoscopies per patient during the first year was 9 (range, 1-44). Median time from transplantation to first Aspergillus-positive sample was 121 d. Bronchial aspirate samples and bronchoalveolar lavage fluid were positive in 71 and 44 patients, respectively. Aspergillus fumigatus (n = 36, 50%) predominated; bacterial samples were also positive in 22 (31%) patients. IA within 4 mo after transplantation was independently associated with CLAD development (subdistribution hazard ratio, 3.75; 95% confidence interval [CI], 1.61-8.73; P < 0.01) by regression analysis. Survival at 3 and 5 y conditional on 1-y CLAD-free survival was 37% (95% CI, 24%-58%), and 24% (95% CI, 11%-52%) in the IA <4 mo group compared to 65% (95% CI, 57%-73%) and 54% (95% CI, 43%-66%) in the non-IA group and to 69% (95% CI, 58%-83%) and 54% (95% CI, 35%-82%) in the IA ≥4 mo group, respectively (P < 0.01, logrank test).

Conclusions

Our evaluation of de novo IA showed that this infection was most strongly associated with CLAD when found within 4 mo after transplantation.

Update on Respiratory Fungal Infections in Cystic Fibrosis Lung Disease and after Lung Transplantation

Cystic fibrosis is the most common autosomal-recessive metabolic disease in the Western world. Impaired trans-membrane chloride transport via the cystic fibrosis transmembrane conductance regulator (CFTR) protein causes thickened body fluids. In the respiratory system, this leads to chronic suppurative cough and recurrent pulmonary infective exacerbations, resulting in progressive lung damage and respiratory failure. Whilst the impact of bacterial infections on CF lung disease has long been recognized, our understanding of pulmonary mycosis is less clear. The range and detection rates of fungal taxa isolated from CF airway samples are expanding, however, in the absence of consensus criteria and univocal treatment protocols for most respiratory fungal conditions, interpretation of laboratory reports and the decision to treat remain challenging. In this review, we give an overview on fungal airway infections in CF and CF-lung transplant recipients and focus on the most common fungal taxa detected in CF, Aspergillus fumigatus, Candida spp., Scedosporium apiospermum complex, Lomentospora species, and Exophiala dermatitidis, their clinical presentations, common treatments and prophylactic strategies, and clinical challenges from a physician’s point of view.

Developments in lung transplantation over the past decade

With an improved median survival of 6.2 years, lung transplantation has become an increasingly acceptable treatment option for end-stage lung disease. Besides survival benefit, improvement of quality of life is achieved in the vast majority of patients. Many developments have taken place in the field of lung transplantation over the past decade. Broadened indication criteria and bridging techniques for patients awaiting lung transplantation have led to increased waiting lists and changes in allocation schemes worldwide. Moreover, the use of previously unacceptable donor lungs for lung transplantation has increased, with donations from donors after cardiac death, donors with increasing age and donors with positive smoking status extending the donor pool substantially. Use of ex vivo lung perfusion further increased the number of lungs suitable for lung transplantation. Nonetheless, the use of these previously unacceptable lungs did not have detrimental effects on survival and long-term graft outcomes, and has decreased waiting list mortality. To further improve long-term outcomes, strategies have been proposed to modify chronic lung allograft dysfunction progression and minimise toxic immunosuppressive effects. This review summarises the developments in clinical lung transplantation over the past decade.

Pulmonary Complications After Allogeneic Hematopoietic Stem Cell Transplantation for Multiple Myeloma: A Case Report

We present a case of a young patient with life-threatening pulmonary complications after allogeneic hematopoietic stem cell transplantation (HSCT). The 25-year-old woman, after HSCT for multiple myeloma, developed severe chronic graft-vs-host disease (GvHD), including bronchiolitis obliterans syndrome. During the treatment of chronic GvHD, 18 months after HSCT, she experienced sudden massive pulmonary hemorrhage with cardiac arrest. The computed tomography imaging revealed lesions suggestive of fungal etiology, with cavity adjacent to the pulmonary vessels. Disqualified from invasive treatment due to poor pulmonary performance, she was treated conservatively with broad-spectrum antibiotics and antifungals. The microbiological workup consistently revealed only Pseudomonas aeruginosa colonization. Her condition steadily improved on treatment. Over 18 months after the incident, she did not experience recurrent bleeding nor serious infection, her primary disease remains in remission, and GvHD symptoms are controlled. Allogeneic HSCT offers possibility of sustained immune-mediated disease control and sometimes even cure, but despite reduced transplant related mortality, GvHD and infections may be detrimental for transplant recipients. Our report illustrates atypical manifestation of pulmonary lesions and highlights the importance of infection control during GvHD treatment.

The role of innate immunity in the long-term outcome of lung transplantation

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD. Here, we examine long-standing assumptions and new concepts linking innate immune activation to late lung allograft fibrosis.