Respiratory viral infections are a distinct risk for bronchiolitis obliterans syndrome and death

The search for peripheral tolerance in lung transplantation

PURPOSE OF REVIEW

Median survival after lung transplantation is 5.7 years, which lags behind other solid organ transplants, such as heart, liver, and kidney. The major barrier to long-term survival in lung transplant recipients is chronic lung allograft dysfunction (CLAD). This review discusses the challenge of CLAD as a barrier to tolerance and identifies key areas in the field that require further development.

RECENT FINDINGS

CLAD is a heterogenous disease in its kinetics of onset and severity and remains a clinical diagnosis of exclusion, based on a decline in allograft function. While acute cellular rejection and antibody-mediated rejection are major risk-factors for CLAD, other barriers to long-term allograft acceptance are aspiration and primary graft dysfunction. However infections, particularly respiratory viral infections and Cytomegalovirus (CMV) remain the most significant risks for CLAD. Additionally, the lung transplant field is limited by a lack of molecular diagnostic assays for CLAD. Further, new targets are needed for precision immunosuppression, and more studies are needed to develop novel interventions to extend allograft acceptance.

SUMMARY

This review discusses new lines of study to address important unmet needs necessary to extend lung allograft acceptance. Other studies, such as tandem lung transplant and bone marrow transplant in select patients with primary immunodeficiency may provide additional lessons on how to potentially establish tolerance. However, tolerance in lung transplant is extremely rare, and further studies are needed to pursue this ultimate goal.

Seasonal Incidence of Medically Attended Respiratory Syncytial Virus Infection From 2015 to 2019 in a Cohort of Adults With High-risk Conditions

Background

Adults with high-risk conditions (underlying health conditions that increase risk of severe outcomes after respiratory infection) may have a substantial incidence of respiratory syncytial virus (RSV), but existing information on this topic is limited. We assessed the seasonal incidence of RSV in adults with high-risk conditions in a Wisconsin community.

Methods

We conducted a retrospective study using data and respiratory specimens from participants with medically attended acute respiratory illness (MAARI) in a test-negative study of influenza vaccine effectiveness. We included individuals ≥18 years old in 2015-16 through 2019-20 seasons, with ≥1 high-risk condition. Residual respiratory specimens were retested for RSV using a multiplex viral panel. We calculated seasonal incidence using Poisson regression and population weighting, with the sum of observed and extrapolated RSV cases in the study cohort divided by the number of adults with high-risk conditions in the underlying source population.

Results

Of 3601 respiratory samples tested, 97% were White and 66% were female. The mean (standard deviation) age of participants was 53 (19) years. We identified 303 RSV infections; 40% were RSV A. Estimated incidence of RSV-related MAARI was 94.1 (79.5-111.5) per 10 000 high-risk adults across all seasons and varied by season. Age-specific incidence per 10 000 was 69.3 (95% confidence interval [CI], 52.4-91.7) for those 18-49 years; 131.6 (95% CI, 92.3-187.6) for those 50-59 years; 109.9 (95% CI, 80.2-150.6) for those 60-74 years; and 150.5 (95% CI, 100.8-224.6) for those ≥75 years.

Conclusions

Overall, these findings suggest a substantial incidence of RSV-related MAARI in adults with high-risk conditions.

Chronic Lung Allograft Dysfunction: Clinical Manifestations and Immunologic Mechanisms

The term "chronic lung allograft dysfunction" has emerged to describe the clinical syndrome of progressive, largely irreversible dysfunction of pulmonary allografts. This umbrella term comprises 2 major clinical phenotypes: bronchiolitis obliterans syndrome and restrictive allograft syndrome. Here, we discuss the clinical manifestations, diagnostic challenges, and potential therapeutic avenues to address this major barrier to improved long-term outcomes. In addition, we review the immunologic mechanisms thought to propagate each phenotype of chronic lung allograft dysfunction, discuss the various models used to study this process, describe potential therapeutic targets, and identify key unknowns that must be evaluated by future research strategies.

Humoral immunity to lung antigens early post-transplant confers risk for chronic lung allograft dysfunction

BACKGROUND

Autoantibodies and de novo donor HLA-specific antibodies (dnDSA) may contribute to chronic lung allograft dysfunction (CLAD). However, the breadth of reactivities against self-antigens and their association with CLAD has been underexamined. In a single-centre study, we screened lung transplant (LTx) recipients for novel autoantibodies at transplant and 6 months post-LTx, assessed dnDSA exposure, and tested their relationship with CLAD-free survival.

METHODS

Serum samples were collected from 89 crossmatch-negative bilateral lung transplant recipients at the time of LTx and 6 months post-LTx, prior to a CLAD diagnosis, for autoantibody screening using a custom antigen microarray optimized for IgM and IgG detection.

RESULTS

Patients who developed CLAD by 5 years post-LTx demonstrated a decrease in average IgG reactivity, but no decrease in IgM reactivity when measured at 6 months post-LTx. IgG anti-tropoelastin, SP-D, and thyroglobulin autoantibodies were significantly elevated 6 months post-LTx in patients who developed CLAD by 5 years, compared to those who remained CLAD-free at 5 years. In contrast, patients who remained CLAD-free at 5 years had elevated levels of IgG anti-CENP-B at both timepoints and PM/SCL100 at 6 months post-LTx, suggesting these may confer protection. Exposure to autoantibodies against lung-enriched targets, as opposed to ubiquitous antigens, and dnDSA conferred increased CLAD risk.

CONCLUSIONS

We have identified novel autoantibodies associated with CLAD-free survival. Our results bolster the independent relationship between autoantibodies and CLAD. We also identified autoantibody signatures that are associated with a marked increase in CLAD risk. Exposure to lung-enriched targets and dnDSA may have a reciprocal amplifying effect that lies on a tissue-specific mechanistic pathway leading to CLAD.

Association between Respiratory Virus Infection and Development of De Novo Donor-Specific Antibody in Lung Transplant Recipients

Chronic lung allograft dysfunction (CLAD) is the most common cause of long-term lung allograft failure. Several factors, including respiratory virus infection (RVI), have been associated with CLAD development, but the underlying mechanisms of these associations are not well understood. We hypothesize that RVI in lung transplant recipients elicits the development of donor-specific antibodies (DSAs), thus providing a mechanistic link between RVI and CLAD development. To test this hypothesis, we retrospectively evaluated for the presence of HLA antibodies in a cohort of lung transplant recipients with symptomatic RVI within the first four months post-transplant using sera at two time points (at/directly after the transplant and following RVI) and time-matched controls without RVI (post-transplant). We found a trend toward the development of de novo DSAs in those with symptomatic RVI versus controls [6/21 (29%) vs. 1/21 (5%), respectively, p = 0.09]. No cases or controls had DSA at baseline. We also found increased rates of CLAD and death among those who developed class II DSA versus those who did not (CLAD: 5/7 (71.4%) vs. 19/34 (54.3%), death: 5/7 (71.4%) vs. 17/35 (48.6%)). Prospective studies evaluating the temporal development of DSA after RVI in lung transplant patients and the subsequent outcomes are warranted.

Respiratory Syncytial Virus Sequelae Among Adults in High-Income Countries: A Systematic Literature Review and Meta-analysis

INTRODUCTION

Respiratory syncytial virus (RSV) can cause severe respiratory infections in adults; however, information on associated sequelae is limited. This systematic literature review aimed to identify sequelae in adults within 1 year following RSV-related hospitalization or resolution of acute infection.

METHODS

Studies were identified from Embase, MEDLINE, LILACS, SciELO, and grey literature. Random-effects meta-analyses using restricted maximum likelihood were used to calculate the proportions and relative risks of sequelae in patients with RSV compared with controls (patients with RSV-negative influenza-like illness, influenza, and parainfluenza) per follow-up period, population, and treatment setting, where possible.

RESULTS

Twenty-one relevant studies covering the period from 1990 to 2019 were included. Among the general population, the most frequent clinical sequela was sustained function loss (33.5% [95% CI 27.6-39.9]). Decline in lung function and cardiovascular event or congestive heart failure were also identified. Utilization sequelae were readmission (highest at > 6 months after discharge) and placement in a skilled nursing facility. The only subpopulation with data regarding sequelae was transplant patients. Among lung transplant patients, the most frequently reported clinical sequelae were decline in lung function, followed by graft dysfunction and bronchiolitis obliterans syndrome. Pooled relative risks were calculated for the following sequela with controls (primarily influenza-positive patients): cardiovascular event (general population) and pulmonary impairment (hematogenic-transplant patients) both 1.4 (95% CI 1.0-2.0) and for readmission (general population) 1.2 (95% CI 1.1-1.3).

CONCLUSIONS

Although less data are available for RSV than for influenza or other lower respiratory tract infections, RSV infection among adults is associated with medically important sequelae, with a prevalence similar to other respiratory pathogens. RSV sequelae should be included in disease burden estimates.

Respiratory Syncytial Virus in Adult Patients at a Tertiary Care Hospital in Germany: Clinical Features and Molecular Epidemiology of the Fusion Protein in the Severe Respiratory Season of 2022/2023

Following an interseasonal rise in mainly pediatric respiratory syncytial virus (RSV) cases in Germany in 2021, an exceptionally high number of adult cases was observed in the subsequent respiratory season of 2022/2023. The aim of this study was to compare the clinical presentation of RSV infections in the pre- and post-SARS-CoV-2 pandemic periods. Additionally, the local epidemiology of the RSV fusion protein was analyzed at a molecular genetic and amino acid level. RSV detections in adults peaked in calendar week 1 of 2023, 8 weeks earlier than the earliest peak observed in the three pre-pandemic seasons. Although the median age of the adult patients was not different (66.5 vs. 65 years), subtle differences between both periods regarding comorbidities and the clinical presentation of RSV cases were noted. High rates of comorbidities prevailed; however, significantly lower numbers of patients with a history of lung transplantation (p = 0.009), chronic kidney disease (p = 0.013), and immunosuppression (p = 0.038) were observed in the 2022/2023 season. In contrast, significantly more lower respiratory tract infections (p < 0.001), in particular in the form of pneumonia (p = 0.015) and exacerbations of obstructive lung diseases (p = 0.008), were detected. An ICU admission was noted for 23.7% of all patients throughout the study period. Sequence analysis of the fusion protein gene revealed a close phylogenetic relatedness, regardless of the season of origin. However, especially for RSV-B, an accumulation of amino acid point substitutions was noted, including in antigenic site Ø. The SARS-CoV-2 pandemic had a tremendous impact on the seasonality of RSV, and the introduction of new vaccination and immunization strategies against RSV warrants further epidemiologic studies of this important pathogen.

Opportunistic Infections Post-Lung Transplantation: Viral, Fungal, and Mycobacterial

Opportunistic infections are a leading cause of lung transplant recipient morbidity and mortality. Risk factors for infection include continuous exposure of the lung allograft to the external environment, high levels of immunosuppression, impaired mucociliary clearance and decreased cough reflex, and impact of the native lung microbiome in single lung transplant recipients. Infection risk is mitigated through careful pretransplant screening of recipients and donors, implementation of antimicrobial prophylaxis strategies, and routine surveillance posttransplant. This review describes common viral, fungal, and mycobacterial infectious after lung transplant and provides recommendations on prevention and treatment.

Impact of Respiratory Viral Infections in Transplant Recipients

Respiratory viral infections (RVIs) are among the leading cause of morbidity and mortality in pediatric hematopoietic stem cell transplant (HCT) and solid organ transplant (SOT) recipients. Transplant recipients remain at high risk for super imposed bacterial and fungal pneumonia, chronic graft dysfunction, and graft failure as a result of RVIs. Recent multicenter retrospective studies and prospective studies utilizing contemporary molecular diagnostic techniques have better delineated the epidemiology and outcomes of RVIs in pediatric transplant recipients and have advanced the development of preventative vaccines and treatment interventions in this population. In this review, we will define the epidemiology and outcomes of RVIs in SOT and HSCT recipients, describe the available assays for diagnosing a suspected RVI, highlight evolving management and vaccination strategies, review the risk of donor derived RVI in SOT recipients, and discuss considerations for delaying transplantation in the presence of an RVI.

Center variability in the prognostic value of a cumulative acute cellular rejection "A-score" for long-term lung transplant outcomes

The acute rejection score (A-score) in lung transplant recipients, calculated as the average of acute cellular rejection A-grades across transbronchial biopsies, summarizes the cumulative burden of rejection over time. We assessed the association between A-score and transplant outcomes in 2 geographically distinct cohorts. The primary cohort included 772 double lung transplant recipients. The analysis was repeated in 300 patients from an independent comparison cohort. Time-dependent multivariable Cox models were constructed to evaluate the association between A-score and chronic lung allograft dysfunction or graft failure. Landmark analyses were performed with A-score calculated at 6 and 12 months posttransplant. In the primary cohort, no association was found between A-score and graft outcome. However, in the comparison cohort, time-dependent A-score was associated with chronic lung allograft dysfunction both as a time-dependent variable (hazard ratio, 1.51; P < .01) and when calculated at 6 months posttransplant (hazard ratio, 1.355; P = .031). The A-score can be a useful predictor of lung transplant outcomes in some settings but is not generalizable across all centers; its utility as a prognostication tool is therefore limited.

American Society of Transplantation and Cellular Therapy Series: #7 - Management of Respiratory Syncytial Virus Infections in Hematopoietic Cell Transplant Recipients

The Practice Guidelines Committee of the American Society of Transplantation and Cellular Therapy (ASTCT) partnered with its Transplant Infectious Disease Special Interest Group (TID-SIG) to update the 2009 compendium-style infectious disease guidelines for hematopoietic cell transplantation (HCT). A new approach was adopted to better serve clinical providers by publishing each standalone topic in the infectious disease series in a concise format of frequently asked questions (FAQ), tables, and figures. Experts in HCT and infectious diseases identified FAQs and then provided answers based on the strength of the recommendation and the level of supporting evidence. In the seventh guideline in the series, we focus on the respiratory syncytial virus (RSV) with FAQs addressing epidemiology, clinical diagnosis, prophylaxis, and treatment. Special consideration was given to RSV in pediatric, cord blood, haploidentical, and T cell-depleted HCT and chimeric antigen receptor T cell therapy recipients, as well as to identify future research directions.

BAL Fluid Eosinophilia Associates With Chronic Lung Allograft Dysfunction Risk: A Multicenter Study

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of death among lung transplant recipients. Eosinophils, effector cells of type 2 immunity, are implicated in the pathobiology of many lung diseases, and prior studies suggest their presence associates with acute rejection or CLAD after lung transplantation.

RESEARCH QUESTION

Does histologic allograft injury or respiratory microbiology correlate with the presence of eosinophils in BAL fluid (BALF)? Does early posttransplant BALF eosinophilia associate with future CLAD development, including after adjustment for other known risk factors?

STUDY DESIGN AND METHODS

We analyzed BALF cell count, microbiology, and biopsy data from a multicenter cohort of 531 lung recipients with 2,592 bronchoscopies over the first posttransplant year. Generalized estimating equation models were used to examine the correlation of allograft histology or BALF microbiology with the presence of BALF eosinophils. Multivariable Cox regression was used to determine the association between ≥ 1% BALF eosinophils in the first posttransplant year and definite CLAD. Expression of eosinophil-relevant genes was quantified in CLAD and transplant control tissues.

RESULTS

The odds of BALF eosinophils being present was significantly higher at the time of acute rejection and nonrejection lung injury histologies and during pulmonary fungal detection. Early posttransplant ≥ 1% BALF eosinophils significantly and independently increased the risk for definite CLAD development (adjusted hazard ratio, 2.04; P = .009). Tissue expression of eotaxins, IL-13-related genes, and the epithelial-derived cytokines IL-33 and thymic stromal lymphoprotein were significantly increased in CLAD.

INTERPRETATION

BALF eosinophilia was an independent predictor of future CLAD risk across a multicenter lung recipient cohort. Additionally, type 2 inflammatory signals were induced in established CLAD. These data underscore the need for mechanistic and clinical studies to clarify the role of type 2 pathway-specific interventions in CLAD prevention or treatment.

A randomized controlled trial of presatovir for respiratory syncytial virus after lung transplant

BACKGROUND

Respiratory syncytial virus (RSV) infection in lung transplant recipients is associated with high morbidity. This study evaluated the RSV fusion inhibitor presatovir in RSV-infected lung transplant recipients.

METHODS

In this international Phase 2b, randomized, double-blind, placebo-controlled trial (NCT02534350), adult lung transplant recipients with symptomatic confirmed RSV infection for ≤7 days received oral presatovir 200 mg on day 1 and 100 mg daily on days 2 to 14, or placebo (2:1), with follow-up through day 28. There were 2 coprimary endpoints: time-weighted average change in nasal RSV load from day 1 to 7, calculated from nasal swabs, in the full analysis set ([FAS]; all patients who received study drug and had quantifiable baseline nasal RSV load) and time-weighted average change in nasal RSV load from day 1 to 7 in the subset of patients with pretreatment symptom duration at the median or shorter of the FAS. Secondary endpoints were changes in respiratory infection symptoms assessed using the Influenza Patient-Reported Outcomes questionnaire and lung function measured by spirometry.

RESULTS

Sixty-one patients were randomized, 40 received presatovir, 20 placebo, and 54 were included in efficacy analyses. Presatovir did not significantly improve the primary endpoint in the FAS (treatment difference [95% CI], 0.10 [-0.43, 0.63] log10 copies/ml; p = 0.72) or the shorter symptom-duration subgroup (-0.12 [-0.94, 0.69] log10 copies/ml; p = 0.76). Secondary endpoints were not different between presatovir and placebo groups. Presatovir was generally well tolerated.

CONCLUSIONS

Presatovir treatment did not significantly improve change in nasal RSV load, symptoms, or lung function in lung transplant recipients.

JAK-STAT activation contributes to cytotoxic T cell-mediated basal cell death in human chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) is the leading cause of death in lung transplant recipients. CLAD is characterized clinically by a persistent decline in pulmonary function and histologically by the development of airway-centered fibrosis known as bronchiolitis obliterans. There are no approved therapies to treat CLAD, and the mechanisms underlying its development remain poorly understood. We performed single-cell RNA-Seq and spatial transcriptomic analysis of explanted tissues from human lung recipients with CLAD, and we performed independent validation studies to identify an important role of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling in airway epithelial cells that contributes to airway-specific alloimmune injury. Specifically, we established that activation of JAK-STAT signaling leads to upregulation of major histocompatibility complex 1 (MHC-I) in airway basal cells, an important airway epithelial progenitor population, which leads to cytotoxic T cell-mediated basal cell death. This study provides mechanistic insight into the cell-to-cell interactions driving airway-centric alloimmune injury in CLAD, suggesting a potentially novel therapeutic strategy for CLAD prevention or treatment.

Risk Factors for Bronchiolitis Obliterans Syndrome after Initial Detection of Pulmonary Impairment after Hematopoietic Cell Transplantation

Pulmonary chronic graft-versus-host-disease (cGVHD), or bronchiolitis obliterans syndrome (BOS), is a highly morbid complication of hematopoietic cell transplantation (HCT). The clinical significance of a single instance of pulmonary decline not meeting the criteria for BOS is unclear. We conducted a retrospective analysis in a cohort of patients who had an initial post-HCT decline in the absolute value of forced expiratory volume in 1 second (FEV1) of ≥10% or mid-expiratory flow rate of ≥25% but not meeting the criteria for BOS (pre-BOS). We examined the impact of clinical variables in patients with pre-BOS on the risk for subsequent BOS. Pre-BOS developed in 1325 of 3170 patients (42%), of whom 72 (5%) later developed BOS. Eighty-four patients developed BOS without detection of pre-BOS by routine screening. Among patients with pre-BOS, after adjusting for other significant variables, airflow obstruction (hazard ratio [HR], 2.0; 95% confidence interval [CI], 1.1 to 3.7; P = .02), percent-predicted FEV1 on decline (HR, .98; 95% CI, .97 to 1.0; P = .02), active cGVHD (HR, 7.7; 95% CI, 3.1 to 19.3; P < .001), peripheral blood stem cell source (HR, 3.8; 95% CI, 1.7 to 8.6; P = .001), and myeloablative conditioning (HR, 2.0; 95% CI, 1.1 to 3.5; P = .02) were associated with subsequent BOS. The absence of airflow obstruction and cGVHD had a negative predictive value of 100% at 6 months for subsequent BOS, but the positive predictive value of both factors was low (cGVHD, 3%; any obstruction, 4%; combined, 6%). Several clinical factors at the time of pre-BOS, particularly active cGVHD and airflow obstruction, increase the risk for subsequent BOS. These factors merit consideration to be included in screening practices to improve the detection of BOS, with the caveat that the predictive utility of these factors is limited by the overall low incidence of BOS among patients with pre-BOS.

Opportunistic Infections Post-Lung Transplantation: Viral, Fungal, and Mycobacterial

Opportunistic infections are a leading cause of lung transplant recipient morbidity and mortality. Risk factors for infection include continuous exposure of the lung allograft to the external environment, high levels of immunosuppression, impaired mucociliary clearance and decreased cough reflex, and impact of the native lung microbiome in single lung transplant recipients. Infection risk is mitigated through careful pretransplant screening of recipients and donors, implementation of antimicrobial prophylaxis strategies, and routine surveillance posttransplant. This review describes common viral, fungal, and mycobacterial infectious after lung transplant and provides recommendations on prevention and treatment.

Fifteen-Year Surveillance of LTR Receiving Pre-Emptive Therapy for CMV Infection: Prevention of CMV Disease and Incidence of CLAD

The efficacy of pre-emptive therapy in the prevention of cytomegalovirus (CMV) disease and the potential association of CMV infection with the occurrence of chronic lung allograft dysfunction (CLAD) was evaluated in 129 lung transplant recipients receiving pre-emptive therapy based on pp65-antigenemia or CMV-DNA in the blood and in the bronchoalveolar lavage. Seventy-one (55%) patients received pre-emptive ganciclovir/valganciclovir (GCV/VGCV) for CMV infection for a median of 28 (9-191) days. Possible CMV disease occurred in six (5%) patients and was healed after the GCV/VGCV therapy. The cumulative incidence of CLAD was 38% and 54% at 5 and 10 years. Acute rejection and CMV load in the blood (but not in the lung) were independent predictors of the occurrence of CLAD. Pre-emptive therapy is highly effective in preventing CMV disease in lung recipients and does not induce a superior incidence of CLAD compared to what reported for other cohorts of patients who received an extended antiviral prophylaxis.

Elevated cell-free DNA in respiratory viral infection and associated lung allograft dysfunction

Respiratory viral infection (RVI) in lung transplant recipients (LTRs) is a risk for chronic lung allograft dysfunction (CLAD). We hypothesize that donor-derived cell-free DNA (%ddcfDNA), at the time of RVI predicts CLAD progression. We followed 39 LTRs with RVI enrolled in the Genomic Research Alliance for Transplantation for 1 year. Plasma %ddcfDNA was measured by shotgun sequencing, with high %ddcfDNA as ≥1% within 7 days of RVI. We examined %ddcfDNA, spirometry, and a composite (progression/failure) of CLAD stage progression, re-transplant, and death from respiratory failure. Fifty-nine RVI episodes, 38 low and 21 high %ddcfDNA were analyzed. High %ddcfDNA subjects had a greater median %FEV₁ decline at RVI (-13.83 vs. -1.83, p = .007), day 90 (-7.97 vs. 0.91, p = .04), and 365 (-20.05 vs. 1.09, p = .047), compared to those with low %ddcfDNA and experienced greater progression/failure within 365 days (52.4% vs. 21.6%, p = .01). Elevated %ddcfDNA at RVI was associated with an increased risk of progression/failure adjusting for symptoms and days post-transplant (HR = 1.11, p = .04). No difference in %FEV₁ decline was seen at any time point when RVIs were grouped by histopathology result at RVI. %ddcfDNA delineates LTRs with RVI who will recover lung function and who will experience sustained decline, a utility not seen with histopathology.

Microbiosis in lung allotransplantation and xenotransplantation: State of the art and future perspective

The respiratory tract is known to harbor a microbial community including bacteria, viruses, and fungi. New techniques contribute enormously to the identification of unknown or culture-independent species and reveal the interaction of the community with the host immune system. The existing respiratory microbiome and substantial equilibrium of the transplanted microbiome from donor lung grafts provide an extreme bloom of dynamic changes in the microenvironment in lung transplantation (LT) recipients. Dysbiosis in grafts are not only related to the modified microbial components but also involve the kinetics of the host-graft "talk," which signifies the destination of graft allograft injury, acute rejection, infection, and chronic allograft dysfunction development in short- and long-term survival. Microbiome-derived factors may contribute to lung xenograft survival when using genetically multimodified pig-derived organs. Here, we review the most advanced knowledge of the dynamics and resilience of microbial communities in transplanted lungs with various pretransplant indications. Conceptual and analytical points of view have been illustrated along the time series, gaining insight into the microbiome and lung grafts. Future endeavors on precise tools, sophisticated models, and novel targeted regimens are needed to improve the long-term survival in these patients.

COVID-Related Chronic Allograft Dysfunction in Lung Transplant Recipients: Long-Term Follow-up Results from Infections Occurring in the Pre-vaccination Era

Introduction: We report on characteristics and lung function outcomes among lung transplant recipients (LTRs) after COVID-19 with infections occurring in the first year of the coronavirus pandemic prior to introduction of the vaccines. Methods: This was a retrospective study of 18 LTRs who tested positive for SARS-CoV-2 between 1 February 2020 and 1 March 2021. The mean age was 49.9 (22–68) years; 12 patients (67%) were male. Two patients died due to severe COVID-19. Results: During the study period, there were 18 lung transplant recipients with a community-acquired SARS-CoV-2 infection. In this cohort, seven had mild, nine had moderate, and two had severe COVID-19. All patients with mild and moderate COVID-19 survived, but the two patients with severe COVID-19 died in the intensive care unit while intubated and on mechanical ventilation. Most patients with moderate COVID-19 showed a permanent lung function decrease that did not improve after 12 months. Conclusion: A majority of LTRs in the current cohort did not experience an alteration in the trajectory of FEV1 evolution after developing SARS-CoV-2 infection. However, in the patients with moderate COVID-19, most patients had a decline in the FEV1 that was present after 1 month after recovery and did not improve or even deteriorated further after 12 months. In LTRs, COVID-19 can have long-lasting effects on pulmonary function. Treatment strategies that influence this trajectory are needed.

Lymphocytic Airway Inflammation in Lung Allografts

Lung transplant remains a key therapeutic option for patients with end stage lung disease but short- and long-term survival lag other solid organ transplants. Early ischemia-reperfusion injury in the form of primary graft dysfunction (PGD) and acute cellular rejection are risk factors for chronic lung allograft dysfunction (CLAD), a syndrome of airway and parenchymal fibrosis that is the major barrier to long term survival. An increasing body of research suggests lymphocytic airway inflammation plays a significant role in these important clinical syndromes. Cytotoxic T cells are observed in airway rejection, and transcriptional analysis of airways reveal common cytotoxic gene patterns across solid organ transplant rejection. Natural killer (NK) cells have also been implicated in the early allograft damage response to PGD, acute rejection, cytomegalovirus, and CLAD. This review will examine the roles of lymphocytic airway inflammation across the lifespan of the allograft, including: 1) The contribution of innate lymphocytes to PGD and the impact of PGD on the adaptive immune response. 2) Acute cellular rejection pathologies and the limitations in identifying airway inflammation by transbronchial biopsy. 3) Potentiators of airway inflammation and heterologous immunity, such as respiratory infections, aspiration, and the airway microbiome. 4) Airway contributions to CLAD pathogenesis, including epithelial to mesenchymal transition (EMT), club cell loss, and the evolution from constrictive bronchiolitis to parenchymal fibrosis. 5) Protective mechanisms of fibrosis involving regulatory T cells. In summary, this review will examine our current understanding of the complex interplay between the transplanted airway epithelium, lymphocytic airway infiltration, and rejection pathologies.

Respiratory Syncytial Virus, Human Metapneumovirus, and Parainfluenza Virus Infections in Lung Transplant Recipients: A Systematic Review of Outcomes and Treatment Strategies

Background

Respiratory syncytial virus (RSV), parainfluenza virus (PIV), and human metapneumovirus (hMPV) are increasingly associated with chronic lung allograft dysfunction (CLAD) in lung transplant recipients (LTR). This systematic review primarily aimed to assess outcomes of RSV/PIV/hMPV infections in LTR and secondarily to assess evidence regarding the efficacy of ribavirin.

Methods

Relevant databases were queried and study outcomes extracted using a standardized method and summarized.

Results

Nineteen retrospective and 12 prospective studies were included (total 1060 cases). Pooled 30-day mortality was low (0–3%), but CLAD progression 180–360 days postinfection was substantial (pooled incidences 19–24%) and probably associated with severe infection. Ribavirin trended toward effectiveness for CLAD prevention in exploratory meta-analysis (odds ratio [OR] 0.61, [0.27–1.18]), although results were highly variable between studies.

Conclusions

RSV/PIV/hMPV infection was followed by a high CLAD incidence. Treatment options, including ribavirin, are limited. There is an urgent need for high-quality studies to provide better treatment options for these infections.

Chronic Lung Allograft Dysfunction

Chronic lung allograft dysfunction (CLAD) is a syndrome of progressive lung function decline, subcategorized into obstructive, restrictive, and mixed phenotypes. The trajectory of CLAD is variable depending on the phenotype, with restrictive and mixed phenotypes having more rapid progression and lower survival. The mechanisms driving CLAD development remain unclear, though allograft injury during primary graft dysfunction, acute cellular rejection, antibody-mediated rejection, and infections trigger immune responses with long-lasting effects that can lead to CLAD months or years later. Currently, retransplantation is the only effective treatment.

Review of respiratory syncytial virus infection among older adults and transplant recipients

Respiratory syncytial virus (RSV) is a common cause of pulmonary infection among children and has been increasingly recognized as an important respiratory pathogen in older adults and immunocompromised hosts. Among older adults, RSV can lead to exacerbations of underlying lung and cardiac disease. It is also associated with significant morbidity and mortality in hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients and may be associated with acute rejection and chronic lung allograft dysfunction among lung transplant recipients (LTRs). Current treatment options for severe RSV disease are limited, and there is a paucity of guidance on RSV treatment among older adults. This narrative review provides a comprehensive overview of RSV disease in older adults, HSCT recipients, and SOT recipients. Nosocomial spread has been reported, thus highlighting the importance of infection prevention and control measures to prevent outbreaks. Antivirals, monoclonal antibodies for immunoprophylaxis, and vaccine development are underway; however, future research is still needed in these critical areas.

Airway disease in hematologic malignancies

INTRODUCTION

Hematologic malignancies are cancers of the blood, bone marrow and lymph nodes and represent a heterogenous group of diseases that affect people of all ages. Treatment generally involves chemotherapeutic or targeted agents that aim to kill malignant cells. In some cases, hematopoietic stem cell transplantation (HCT) is required to replenish the killed blood and stem cells. Both disease and therapies are associated with pulmonary complications. As survivors live longer with the disease and are treated with novel agents that may result in secondary immunodeficiency, airway diseases and respiratory infections will increasingly be encountered. To prevent airways diseases from adding to the morbidity of survivors or leading to long-term mortality, improved understanding of the pathogenesis and treatment of viral bronchiolitis, BOS, and bronchiectasis is necessary.

AREAS COVERED

This review focuses on viral bronchitis, BOS and bronchiectasis in people with hematological malignancy. Literature was reviewed from Pubmed for the areas covered.

EXPERT OPINION

Airway disease impacts significantly on hematologic malignancies. Viral bronchiolitis, BOS and bronchiectasis are common respiratory manifestations in hematological malignancy. Strategies to identify patients early in their disease course may improve the efficacy of treatment and halt progression of lung function decline and improve quality of life.

Viral infections in lung transplantation

Viral infections account for up to 30% of all infectious complications in lung transplant recipients, remaining a significant cause of morbidity and even mortality. Impact of viral infections is not only due to the direct effects of viral replication, but also to immunologically-mediated lung injury that may lead to acute rejection and chronic lung allograft dysfunction. This has particularly been seen in infections caused by herpesviruses and respiratory viruses. The implementation of universal preventive measures against cytomegalovirus (CMV) and influenza (by means of antiviral prophylaxis and vaccination, respectively) and administration of early antiviral treatment have reduced the burden of these diseases and potentially their role in affecting allograft outcomes. New antivirals against CMV for prophylaxis and for treatment of antiviral-resistant CMV infection are currently being evaluated in transplant recipients, and may continue to improve the management of CMV in lung transplant recipients. However, new therapeutic and preventive strategies are highly needed for other viruses such as respiratory syncytial virus (RSV) or parainfluenza virus (PIV), including new antivirals and vaccines. This is particularly important in the advent of the COVID-19 pandemic, for which several unanswered questions remain, in particular on the best antiviral and immunomodulatory regimen for decreasing mortality specifically in lung transplant recipients. In conclusion, the appropriate management of viral complications after transplantation remain an essential step to continue improving survival and quality of life of lung transplant recipients.

Correlation between BAL CXCR3 chemokines and lung allograft histopathologies: A multicenter study

The histopathologic diagnosis of acute allograft injury is prognostically important in lung transplantation with evidence demonstrating a strong and consistent association between acute rejection (AR), acute lung injury (ALI), and the subsequent development of chronic lung allograft dysfunction (CLAD). The pathogenesis of these allograft injuries, however, remains poorly understood. CXCL9 and CXCL10 are CXC chemokines induced by interferon-γ and act as potent chemoattractants of mononuclear cells. We hypothesized that these chemokines are involved in the mononuclear cell recruitment associated with AR and ALI. We further hypothesized that the increased activity of these chemokines could be quantified as increased levels in the bronchoalveolar lavage fluid. In this prospective multicenter study, we evaluate the incidence of histopathologic allograft injury development during the first-year post-transplant and measure bronchoalveolar CXCL9 and CXCL10 levels at the time of the biopsy. In multivariable models, CXCL9 levels were 1.7-fold and 2.1-fold higher during AR and ALI compared with "normal" biopsies without histopathology. Similarly, CXCL10 levels were 1.6-fold and 2.2-fold higher during these histopathologies, respectively. These findings support the association of CXCL9 and CXCL10 with episodes of AR and ALI and provide potential insight into the pathogenesis of these deleterious events.

The respiratory microbiome after lung transplantation: Reflection or driver of respiratory disease?

With the introduction of high-throughput sequencing methods, our understanding of the human lower respiratory tract's inhabitants has expanded significantly in recent years. What is now termed the "lung microbiome" has been described for healthy patients, as well as people with chronic lung diseases and lung transplants. The lung microbiome of lung transplant recipients (LTRs) has proven to be unique compared with nontransplant patients, with characteristic findings associated with disease states, such as pneumonia, acute rejection, and graft failure. In this review, we summarize the current understanding of the lung microbiome in LTRs, not only focusing on bacteria but also highlighting key findings of the viral and the fungal community. Based on our knowledge of the lung microbiome in LTRs, we propose multiple opportunities for clinical use of the microbiome to improve outcomes in this population.

Donor derived cell free DNA% is elevated with pathogens that are risk factors for acute and chronic lung allograft injury

BACKGROUND

Acute and chronic forms of lung allograft injury are associated with specific respiratory pathogens. Donor-derived cell free DNA (ddcfDNA) has been shown to be elevated with acute lung allograft injury and predictive of long-term outcomes. We examined the %ddcfDNA values at times of microbial isolation from bronchoalveolar lavage (BAL).

METHODS

Two hundred and six BAL samples from 51 Lung Transplant Recipients (LTRs) with concurrently available plasma %ddcfDNA were analyzed along with microbiology and histopathology. Microbial species were grouped into bacterial, fungal, and viral and "higher risk" and "lower risk" cohorts based on historical association with downstream allograft dysfunction. Analyses were performed to determine pathogen category association with %ddcfDNA, independent of inter-subject variability.

RESULTS

Presence of microbial isolates in BAL was not associated with elevated %ddcfDNA compared to samples without isolates. However, "higher risk" bacterial and viral microbes showed greater %ddcfDNA values than lower risk species (1.19% vs. 0.65%, p < 0.01), independent of inter-subject variability. Histopathologic abnormalities concurrent with pathogen isolation were associated with higher %ddcfDNA compared to isolation episodes with normal histopathology (medians 1.23% and 0.66%, p = 0.05). Assessments showed no evidence of correlation between histopathology or bronchoscopy indication and presence of higher risk vs. lower risk pathogens.

CONCLUSION

%ddcfDNA is higher among cases of microbial isolation with concurrent abnormal histopathology and with isolation of higher risk pathogens known to increase risk of allograft dysfunction. Future studies should assess if %ddcfDNA can be used to stratify pathogens for risk of CLAD and identify pathogen associated injury prior to histopathology.

Community-Acquired Respiratory Viruses Post-Lung Transplant

Survival in lung transplant recipients (LTRs) lags behind heart, liver, and kidney transplant, in part due to the direct and indirect effects of infection. LTRs have increased susceptibility to infection due to the combination of a graft continually exposed to the outside world, multiple mechanisms for impaired mucus clearance, and immunosuppression. Community-acquired respiratory viral infections (CARVs) are common in LTRs. Picornaviruses have roughly 40% cumulative incidence followed by respiratory syncytial virus and coronaviruses. Although single-center retrospective and prospective series implicate CARV in rejection and mortality, conclusive evidence for and well-defined mechanistic links to long-term outcome are lacking. Treatment of viral infections can be challenging except for influenza. Future studies are needed to develop better treatments and clarify the links between CARV and long-term outcomes.

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.

Influenza Virus Infection and Transplantation

Influenza infection poses significant risk for solid organ transplant recipients who often experience more severe infection with increased rates of complications, including those relating to the allograft. Although symptoms of influenza experienced by transplant recipients are similar to that of the general population, fever is not a ubiquitous symptom and lymphopenia is common. Annual inactivated influenza vaccine is recommended for all transplant recipients. Newer strategies such as using a higher dose vaccine or multiple doses in the same season appear to provide greater immunogenicity. Neuraminidase inhibitors are the mainstay of treatment and chemoprophylaxis although resistance may occur in the transplant setting. Influenza therapeutics are advancing, including the recent licensure of baloxavir; however, many remain to be evaluated in transplant recipients and are not yet in routine clinical use. Further population-based studies spanning multiple influenza seasons are needed to enhance our understanding of influenza epidemiology in solid organ transplant recipients. Specific assessment of newer influenza therapeutics in transplant recipients and refinement of prevention strategies are vital to reducing morbidity and mortality.

Editorial: COVID-19 immunology and organ transplantation

PURPOSE OF REVIEW

The aim of this study was to provide a critical appraisal of the literature on the effects of the COVID-19 pandemic on organ transplantation, with a specific focus on lung transplantation given the predominant pulmonary involvement of the virus.

RECENT FINDINGS

There was a significant decrease in lung transplant volumes during the first wave of the COVID-19 pandemic due to a combination of reduced availability of donors and an imbalance between waitlist additions and inactivations. SARS-CoV-2 infection was subsequently associated with an exuberant immune response that can lead to the development of postinfectious fibrotic lung disease. Few lung transplants have been performed in previously infected recipients and long-term outcomes remain unknown. Although the lung transplant volume rebounded during the second wave, it is unclear what the long-term effects of healthcare resource limitation and public health measures will have on transplant volumes in the future. Outcomes after SARS-CoV-2 infection in previous lung transplant recipients appear to be worse than the general public, and, although an immunosuppressed state likely contributes to these outcomes, whether immunosuppression should be altered in those exposed to or infected with SARS-CoV-2 remains unanswered in the absence of unequivocal data.

SUMMARY

The COVID-19 pandemic has presented a number of challenges for lung transplant programs across the globe. Multiple research questions remain to be answered in order to optimally manage lung transplant recipients in the context of this pandemic.

Drug Resistance Assessment Following Administration of Respiratory Syncytial Virus (RSV) Fusion Inhibitor Presatovir to Participants Experimentally Infected With RSV

BACKGROUND

Presatovir is an oral respiratory syncytial virus (RSV) fusion inhibitor targeting RSV F protein. In a double-blind, placebo-controlled study in healthy adults experimentally infected with RSV (Memphis-37b), presatovir significantly reduced viral load and clinical disease severity in a dose-dependent manner.

METHODS

Viral RNA from nasal wash samples was amplified and the F gene sequenced to monitor presatovir resistance. Effects of identified amino acid substitutions on in vitro susceptibility to presatovir, viral fitness, and clinical outcome were assessed.

RESULTS

Twenty-eight treatment-emergent F substitutions were identified. Of these, 26 were tested in vitro; 2 were not due to lack of recombinant virus recovery. Ten substitutions did not affect presatovir susceptibility, and 16 substitutions reduced RSV susceptibility to presatovir (2.9- to 410-fold). No substitutions altered RSV susceptibility to palivizumab or ribavirin. Frequency of phenotypically resistant substitutions was higher with regimens containing lower presatovir dose and shorter treatment duration. Participants with phenotypic presatovir resistance had significantly higher nasal viral load area under the curve relative to those without, but substitutions did not significantly affect peak viral load or clinical manifestations of RSV disease.

CONCLUSIONS

Emergence of presatovir-resistant RSV occurred during therapy but did not significantly affect clinical efficacy in participants with experimental RSV infection.

Chronic Lung Allograft Dysfunction: Review of CT and Pathologic Findings

Chronic lung allograft dysfunction (CLAD) is the most common cause of mortality in lung transplant recipients after the 1st year of transplantation. CLAD has traditionally been classified into two distinct obstructive and restrictive forms: bronchiolitis obliterans syndrome and restrictive allograft syndrome. However, CLAD may manifest with a spectrum of imaging and pathologic findings and a combination of obstructive and restrictive physiologic abnormalities. Although the initial CT manifestations of CLAD may be nonspecific, the progression of findings at follow-up should signal the possibility of CLAD and may be present on imaging studies prior to the development of functional abnormalities of the lung allograft. This review encompasses the evolution of CT findings in CLAD, with emphasis on the underlying pathogenesis and pathologic condition, to enhance understanding of imaging findings. The purpose of this article is to familiarize the radiologist with the initial and follow-up CT findings of the obstructive, restrictive, and mixed forms of CLAD, for which early diagnosis and treatment may result in improved survival. Supplemental material is available for this article. © RSNA, 2021.

Human Metapneumovirus and Parainfluenza Virus Infections in Lung Transplant Recipients: the Effects on Lung Allograft and Clinical Outcomes

BACKGROUND

Human metapneumovirus (HMPVi) and parainfluenza virus (PIV) infections are common community acquired infection in lung transplant recipients (LTRs), but data is extremely limited.

METHODS

A retrospective study including all LTRs at the Johns Hopkins Hospital during July 2010-June 2019 with positive HMPV and PIV polymerase chain reaction (PCR) respiratory specimens was performed.

RESULTS

Thirty-one HMPV- and 53 PIV-infected LTRs were identified. LTRs with HMPVi and PIVi had similar baseline characteristics, infection parameters, treatment allocation, and allograft function outcomes. Among entire cohort, 31.6% had CLAD stage progression within 1-year post infections (29.2% vs 35.5% for PIV vs HMPV, respectively, p= 0.56). In forced expiratory volume in 1 second percent (FEV1%) trajectory analysis showed steadily decline of FEV1 across time among CLAD stage progressor from both viruses. FEV1% decline ≥ 10% at 90 days had adjusted hazard ratio for CLAD stage progression of 18.4 [4.98, 67.76] and 4.6 [1.36, 15.34] for PIVi and HMPVi, respectively. PIVi caused higher DSA development (11.8% vs 3.2%, p=0.18) and 1-year mortality (9.4% vs 0%, p=0.11), compared to HMPVi, even though the results were not statistically significant. Ribavirin did not show protective effect and mycophenolate discontinuation during infection did not increase risk of CLAD stage progression.

CONCLUSION

One-third of HMPV- and PIV- infected LTRs developed CLAD stage progression within 1 year. The lack of early lung function recovery may predict long term CLAD progression.

Lung microbiota predict chronic rejection in healthy lung transplant recipients: a prospective cohort study

BACKGROUND

Alterations in the respiratory microbiome are common in chronic lung diseases, correlate with decreased lung function, and have been associated with disease progression. The clinical significance of changes in the respiratory microbiome after lung transplant, specifically those related to development of chronic lung allograft dysfunction (CLAD), are unknown. The aim of this study was to evaluate the effect of lung microbiome characteristics in healthy lung transplant recipients on subsequent CLAD-free survival.

METHODS

We prospectively studied a cohort of lung transplant recipients at the University of Michigan (Ann Arbor, MI, USA). We analysed characteristics of the respiratory microbiome in acellular bronchoalveolar lavage fluid (BALF) collected from asymptomatic patients during per-protocol surveillance bronchoscopy 1 year after lung transplantation. For our primary endpoint, we evaluated a composite of development of CLAD or death at 500 days after the 1-year surveillance bronchoscopy. Our primary microbiome predictor variables were bacterial DNA burden (total 16S rRNA gene copies per mL of BALF, quantified via droplet digital PCR) and bacterial community composition (determined by bacterial 16S rRNA gene sequencing). Patients' lung function was followed serially at least every 3 months by spirometry, and CLAD was diagnosed according to International Society of Heart and Lung Transplant 2019 guidelines.

FINDINGS

We analysed BALF from 134 patients, collected during 1-year post-transplant surveillance bronchoscopy between Oct 21, 2005, and Aug 25, 2017. Within 500 days of follow-up from the time of BALF sampling, 24 (18%) patients developed CLAD, five (4%) died before confirmed development of CLAD, and 105 (78%) patients remained CLAD-free with complete follow-up. Lung bacterial burden was predictive of CLAD development or death within 500 days of the surveillance bronchoscopy, after controlling for demographic and clinical factors, including immunosuppression and bacterial culture results, in a multivariable survival model. This relationship was evident when burden was analysed as a continuous variable (per log₁₀ increase in burden, HR 2·49 [95% CI 1·38-4·48], p=0·0024) or by tertiles (middle vs lowest bacterial burden tertile, HR 4·94 [1·25-19·42], p=0·022; and highest vs lowest, HR 10·56 [2·53-44·08], p=0·0012). In patients who developed CLAD or died, composition of the lung bacterial community significantly differed to that in patients who survived and remained CLAD-free (on permutational multivariate analysis of variance, p=0·047 at the taxonomic level of family), although differences in community composition were associated with bacterial burden. No individual bacterial taxa were definitively associated with CLAD development or death.

INTERPRETATION

Among asymptomatic lung transplant recipients at 1-year post-transplant, increased lung bacterial burden is predictive of chronic rejection and death. The lung microbiome represents an understudied and potentially modifiable risk factor for lung allograft dysfunction.

FUNDING

US National Institutes of Health, Cystic Fibrosis Foundation, Brian and Mary Campbell and Elizabeth Campbell Carr research gift fund.

Evaluation of 10 years of parainfluenza virus, human metapneumovirus, and respiratory syncytial virus infections in lung transplant recipients

Respiratory tract infection with pneumoviruses (PVs) and paramyxoviruses (PMVs) are increasingly associated with chronic lung allograft dysfunction (CLAD) in lung transplant recipients (LTRs). Ribavirin may be a treatment option but its effectiveness is unclear, especially with respect to infection severity. We retrospectively analyzed 10 years of PV/PMV infections in LTRs. The main end points were forced expiratory volume in 1 second (FEV₁ ) at 3 and 6 months postinfection, expressed as a percentage of pre-infection FEV₁ and incidence of new or progressed CLAD 6 months postinfection. A total of 139 infections were included: 88 severe infections (63%) (defined as >10% FEV₁ loss at infection) and 51 mild infections (37%) (≤10% FEV₁ loss). Overall postinfection CLAD incidence was 20%. Associations were estimated on postinfection FEV₁ for ribavirin vs no ribavirin (+13.2% [95% CI: 7.79; 18.67]) and severe vs mild infection (-11.1% [95% CI: -14.76; -7.37]). Factors associated with CLAD incidence at 6 months were ribavirin treatment (odds ratio (OR [95% CI]) 0.24 [0.10; 0.59]), severe infection (OR [95% CI] 4.63 [1.66; 12.88]), and mycophenolate mofetil use (OR [95% CI] 0.38 [0.14; 0.97]). These data provide valuable information about the outcomes of lung transplant recipients with these infections and suggests possible associations of ribavirin use and infection severity with long-term outcomes. Well-designed prospective trials are needed to confirm these findings.

Oral and Inhaled Ribavirin Treatment for Respiratory Syncytial Virus Infection in Lung Transplant Recipients

BACKGROUND

Respiratory syncytial virus (RSV) infection in lung transplant recipients (LTRs) causes mortality rates of 10%-20% despite antiviral therapy. Ribavirin (RBV) has been used to treat RSV-infected LTRs with limited data.

METHODS

A retrospective study including all LTRs at Duke Hospital during January 2013-May 2017 with positive RSV polymerase chain reaction respiratory specimens was performed.

RESULTS

Fifty-six of 70 patients in the oral RBV group and 29 of 32 in the inhaled RBV group had symptomatic RSV infection. One patient receiving oral RBV had to prematurely stop drug due to significant nausea and vomiting. While unadjusted all-cause 1-year mortality was significantly higher in the inhaled RBV group (24.1% versus 7.1% [oral RBV], P = 0.03), adjusted hazard ratio (HR) for death and oral RBV use (compared to inhaled RBV), accounting for oxygen requirement and need for mechanical ventilation, showed the HR for death and oral RBV use was 0.38 ([0.10, 1.46], P = 0.38). The HR for death in patients with supplemental oxygen >2 L/min at diagnosis was 6.18 ([1.33, 26.83], P = 0.02). Kaplan-Meier curves showed patients with forced expiratory volume in 1 second decline ≥5% and ≥10% at 90 days post-RSV infection had a higher 1-year mortality (P = 0.004 and P = 0.001, respectively).

CONCLUSIONS

Oral and inhaled RBV appear to be well tolerated in LTRs, and our data support the use of oral RBV as a safe alternative to inhaled ribavirin in LTRs. Oxygen requirement >2 L/min at diagnosis and forced expiratory volume in 1 second decline ≥5% postinfection may be markers for increased mortality.

Community-acquired Respiratory Viruses Are a Risk Factor for Chronic Lung Allograft Dysfunction

Background

The relationship between community-acquired respiratory viruses (CARVs) and chronic lung allograft dysfunction (CLAD) in lung transplant recipients is still controversial.

Methods

We performed a prospective cohort study (2009–2014) in all consecutive adult patients (≥18 years) undergoing lung transplantation in the Hospital Universitari Vall d’Hebron (Barcelona, Spain). We systematically collected nasopharyngeal swabs from asymptomatic patients during seasonal changes, from patients with upper respiratory tract infectious disease, lower respiratory tract infectious disease (LRTID), or acute rejection. Nasopharyngeal swabs were analyzed by multiplex polymerase chain reaction. Primary outcome was to evaluate the potential association of CARVs and development of CLAD. Time-dependent Cox regression models were performed to identify the independent risk factors for CLAD.

Results

Overall, 98 patients (67 bilateral lung transplant recipients; 63.3% male; mean age, 49.9 years) were included. Mean postoperative follow-up was 3.4 years (interquartile range [IQR], 2.5–4.0 years). Thirty-eight lung transplant recipients (38.8%) developed CLAD, in a median time of 20.4 months (IQR, 12–30.4 months). In time-controlled multivariate analysis, CARV-LRTID (hazard ratio [HR], 3.00 [95% confidence interval {CI}, 1.52–5.91]; P = .002), acute rejection (HR, 2.97 [95% CI, 1.51–5.83]; P = .002), and cytomegalovirus pneumonitis (HR, 3.76 [95% CI, 1.23–11.49]; P = .02) were independent risk factors associated with developing CLAD.

Conclusions

Lung transplant recipients with CARVs in the lower respiratory tract are at increased risk to develop CLAD.

Incidence, management and outcome of respiratory syncytial virus infection in adult lung transplant recipients: a 9-year retrospective multicentre study

OBJECTIVES

To analyse functional outcome parameters according to antimicrobial treatments after respiratory syncytial virus (RSV)-confirmed infection in adult lung transplant recipients.

METHODS

A 9-year retrospective multicentre cohort study (2011-19) included adult lung transplant recipients with RSV-confirmed infection. The first endpoint determined new allograft dysfunction (acute graft rejection and chronic lung allograft dysfunction (CLAD)) 3 months after infection. Then baseline and 3 months' postinfection forced expiratory volume in 1 second (FEV₁) values were compared according to antimicrobial treatment. Univariate logistic regression analysis was performed.

RESULTS

RSV infection was confirmed in 77 of 424 lung transplant recipients (estimated incidence of 0.025 per patient per year; 95% confidence interval 0.018-0.036). At 3 months, 22 recipients (28.8%) developed allograft dysfunction: ten (13%) possible CLAD, six (7.9%) acute rejection and six (7.9%) CLAD. Recipients with the lowest preinfection FEV₁ had a greater risk of developing pneumonia (median (interquartile range) 1.5 (1.1-1.9) vs. 2.2 (1.5-2.4) L/s, p 0.003) and a higher odds of receiving antibiotics (1.6 (1.3-2.3) vs. 2.3 (1.9-2.5) L/s, p 0.017; odds ratio 0.52, 95% confidence interval 0.27-0.99). Compared to tracheobronchitis/bronchiolitis, RSV-induced pneumonia led more frequently to hospitalization (91.7%, 22 vs. 58.0%, 29, p 0.003) and intensive care unit admission (33.3%, 8 vs. 0, p < 10^-3). For ribavirin-treated recipients (24.7%, 19) and azithromycin prophylaxis (50.6%, 39), 3-month FEV₁ values were not different from untreated recipients. The overall mortality was 2.5% at 1 month and 5.3% at 6 months, unrelated to RSV.

CONCLUSIONS

At 3 months after RSV-confirmed infection, 22 recipients (28.8%) had new allograft dysfunction. Ribavirin treatment and azithromycin prophylaxis did not prevent FEV₁ decline.

Assessment of Drug Resistance during Phase 2b Clinical Trials of Presatovir in Adults Naturally Infected with Respiratory Syncytial Virus

This study summarizes drug resistance analyses in 4 recent phase 2b trials of the respiratory syncytial virus (RSV) fusion inhibitor presatovir in naturally infected adults. Adult hematopoietic cell transplant (HCT) recipients, lung transplant recipients, or hospitalized patients with naturally acquired, laboratory-confirmed RSV infection were enrolled in 4 randomized, double-blind, placebo-controlled studies with study-specific presatovir dosing. Full-length RSV F sequences amplified from nasal swabs obtained at baseline and postbaseline were analyzed by population sequencing. Substitutions at RSV fusion inhibitor resistance-associated positions are reported. Genotypic analyses were performed on 233 presatovir-treated and 149 placebo-treated subjects. RSV F variant V127A was present in 8 subjects at baseline. Population sequencing detected treatment-emergent substitutions in 10/89 (11.2%) HCT recipients with upper and 6/29 (20.7%) with lower respiratory tract infection, 1/35 (2.9%) lung transplant recipients, and 1/80 (1.3%) hospitalized patients treated with presatovir; placebo-treated subjects had no emergent resistance-associated substitutions. Subjects with substitutions at resistance-associated positions had smaller decreases in viral load during treatment relative to those without, but they had similar clinical outcomes. Subject population type and dosing regimen may have influenced RSV resistance development during presatovir treatment. Subjects with genotypic resistance development had decreased virologic responses compared to those without genotypic resistance but had comparable clinical outcomes.

Sterile inflammation in thoracic transplantation

The life-saving benefits of organ transplantation can be thwarted by allograft dysfunction due to both infectious and sterile inflammation post-surgery. Sterile inflammation can occur after necrotic cell death due to the release of endogenous ligands [such as damage-associated molecular patterns (DAMPs) and alarmins], which perpetuate inflammation and ongoing cellular injury via various signaling cascades. Ischemia-reperfusion injury (IRI) is a significant contributor to sterile inflammation after organ transplantation and is associated with detrimental short- and long-term outcomes. While the vicious cycle of sterile inflammation and cellular injury is remarkably consistent amongst different organs and even species, we have begun understanding its mechanistic basis only over the last few decades. This understanding has resulted in the developments of novel, yet non-specific therapies for mitigating IRI-induced graft damage, albeit with moderate results. Thus, further understanding of the mechanisms underlying sterile inflammation after transplantation is critical for identifying personalized therapies to prevent or interrupt this vicious cycle and mitigating allograft dysfunction. In this review, we identify common and distinct pathways of post-transplant sterile inflammation across both heart and lung transplantation that can potentially be targeted.

Epidemiology and persistence of rhinovirus in pediatric lung transplantation

BACKGROUND

Infection with rhinovirus (HRV) occurs following pediatric lung transplantation. Prospective studies documenting frequencies, persistence, and progression of HRV in this at-risk population are lacking.

METHODS

In the Clinical Trials in Organ Transplant in Children prospective observational study, we followed 61 lung transplant recipients for 2 years. We quantified molecular subtypes of HRV in serially collected nasopharyngeal (NP) and bronchoalveolar lavage (BAL) samples and correlated them with clinical characteristics.

RESULTS

We identified 135 community-acquired respiratory infections (CARV) from 397 BAL and 480 NP samples. We detected 93 HRV events in 42 (68.8%) patients, 22 of which (23.4%) were symptomatic. HRV events were contiguous with different genotypes identified in 23 cases, but symptoms were not preferentially associated with any particular species. Nine (9.7%) HRV events persisted over multiple successive samples for a median of 36 days (range 18-408 days). Three persistent HRV were symptomatic. When we serially measured forced expiratory volume in one second (FEV1) in 23 subjects with events, we did not observe significant decreases in lung function over 12 months post-HRV.

CONCLUSION

In conjunction with our previous reports, our prospectively collected data indicate that molecularly heterogeneous HRV infections occur commonly following pediatric lung transplantation, but these infections do not negatively impact clinical outcomes.

Community-acquired respiratory viruses

PURPOSE OF REVIEW

Incidence of community-acquired respiratory viruses (CARVs) after lung transplantation (LTx) is 10-68 cases per 100 patient-years. Infected patients may develop graft failure and there seems to be an association between CARV infection and development of chronic lung allograft dysfunction (CLAD). This review summarizes the impact of CARV infection after LTx and potential treatment strategies.

RECENT FINDINGS

Detection rate of CARV depends on diagnostic methods. CARV infections after LTx are reported more frequently probably attributed to improved diagnostic methods, especially nucleic acid testing. Paramyxoviridae and picornaviridae are most frequent. For paramyxoviridae, the association with CLAD is reported in various single-center observational studies. Neuraminidase inhibitors are approved for influenza and can be safely used in flu-infected LTx patients. There is no approved treatment for paramyxoviruses, most centers use ribavirin in the infected LTx recipient.

SUMMARY

Antivirals against CARV in LTx recipients have not yet demonstrated reduced morbidity in randomized clinical trials. Agents against CARV under development are inhibiting viral attachment and use silencing mechanisms of viral replication. The cohort of lung transplant recipients is a focus of intense research because of the high morbidity of CARV infection and intense surveillance of LTx recipeints.

Infection prophylaxis and management of viral infection

Viral infections are associated with significant morbidity and mortality in lung transplant recipients. Importantly, several viral infections have been associated with the development of chronic lung allograft dysfunction (CLAD). Community-acquired respiratory viruses (CARV) such as influenza and respiratory syncytial virus (RSV), are frequently associated with acute and chronic rejection. Cytomegalovirus (CMV) remains a significant burden in regards to morbidity and mortality in lung transplant recipients. Epstein-Barr virus (EBV) is mostly involved with the development of post-transplant lymphoproliferative disorder (PTLD), a lymphoid proliferation that occurs in the setting of immunosuppression. On the other hand, the development of direct acting antivirals for hepatitis C virus (HCV) is changing the use of HCV-positive organs in transplantation. In this article we will focus on reviewing common viral infections that have a significant impact on lung transplant recipients looking at epidemiology, prevention and potential treatment.

Late viral or bacterial respiratory infections in lung transplanted patients: impact on respiratory function

Background

Respiratory infections are a major threat for lung recipients. We aimed to compare with a monocentric study the impact of late viral and bacterial respiratory infections on the graft function.

Methods

Patients, who survived 6 months or more following lung transplantation that took place between 2009 and 2014, were classified into three groups: a viral infection group (VIG) (without any respiratory bacteria), a bacterial infection group (BIG) (with or without any respiratory viruses), and a control group (CG) (no documented infection). Chronic lung allograft dysfunction (CLAD) and acute rejection were analysed 6 months after the inclusion in the study.

Results

Among 99 included lung recipients, 57 (58%) had at least one positive virological respiratory sample during the study period. Patients were classified as follows: 38 in the VIG, 25 in the BIG (among which 19 co-infections with a virus) and 36 in the CG. The BIG presented a higher initial deterioration in lung function (p = 0.05) than the VIG. But 6 months after the infection, only the VIG presented a median decrease of forced expiratory volume in 1 s; − 35 mL (IQR; − 340; + 80) in the VIG, + 140 mL (+ 60;+ 330) in the BIG and + 10 (− 84;+ 160) in the CG, p < 0.01. Acute rejection was more frequent in the VIG (n = 12 (32%)), than the BIG (n = 6 (24%)) and CG (n = 3 (8%)), p < 0.05, despite presenting no more CLAD (p = 0.21).

Conclusions

Despite a less severe initial presentation, single viral respiratory infections seem to lead to a greater deterioration in lung function, and to more acute rejection, than bacterial infections.