MICB Genomic Variant Is Associated with NKG2D-mediated Acute Lung Injury and Death.

Rationale: Acute lung injury (ALI) carries a high risk of mortality but has no established pharmacologic therapy. We previously found that experimental ALI occurs through natural killer (NK) cell NKG2D receptor activation and that the cognate human ligand, MICB, was associated with ALI after transplantation. Objectives: To investigate the association of a common missense variant, MICBG406A, with ALI. Methods: We assessed MICBG406A genotypes within two multicenter observational study cohorts at risk for ALI: primary graft dysfunction (N = 619) and acute respiratory distress syndrome (N = 1,376). Variant protein functional effects were determined in cultured and ex vivo human samples. Measurements and Main Results: Recipients of MICBG406A-homozygous allografts had an 11.1% absolute risk reduction (95% confidence interval [CI], 3.2-19.4%) for severe primary graft dysfunction after lung transplantation and reduced risk for allograft failure (hazard ratio, 0.36; 95% CI, 0.13-0.98). In participants with sepsis, we observed 39% reduced odds of moderately or severely impaired oxygenation among MICBG406A-homozygous individuals (95% CI, 0.43-0.86). BAL NK cells were less frequent and less mature in participants with MICBG406A. Expression of missense variant protein MICBD136N in cultured cells resulted in reduced surface MICB and reduced NKG2D ligation relative to wild-type MICB. Coculture of variant MICBD136N cells with NK cells resulted in less NKG2D activation and less susceptibility to NK cell killing relative to the wild-type cells. Conclusions: These data support a role for MICB signaling through the NKG2D receptor in mediating ALI, suggesting a novel therapeutic approach.

The Impact of Donor Smoking on Primary Graft Dysfunction and Mortality after Lung Transplantation.

Rationale: Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Prior studies implicated proxy-defined donor smoking as a risk factor for PGD and mortality. Objectives: We aimed to more accurately assess the impact of donor smoke exposure on PGD and mortality using quantitative smoke exposure biomarkers. Methods: We performed a multicenter prospective cohort study of lung transplant recipients enrolled in the Lung Transplant Outcomes Group cohort between 2012 and 2018. PGD was defined as grade 3 at 48 or 72 hours after lung reperfusion. Donor smoking was defined using accepted thresholds of urinary biomarkers of nicotine exposure (cotinine) and tobacco-specific nitrosamine (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanol [NNAL]) in addition to clinical history. The donor smoking-PGD association was assessed using logistic regression, and survival analysis was performed using inverse probability of exposure weighting according to smoking category. Measurements and Main Results: Active donor smoking prevalence varied by definition, with 34-43% based on urinary cotinine, 28% by urinary NNAL, and 37% by clinical documentation. The standardized risk of PGD associated with active donor smoking was higher across all definitions, with an absolute risk increase of 11.5% (95% confidence interval [CI], 3.8% to 19.2%) by urinary cotinine, 5.7% (95% CI, -3.4% to 14.9%) by urinary NNAL, and 6.5% (95% CI, -2.8% to 15.8%) defined clinically. Donor smoking was not associated with differential post-lung transplant survival using any definition. Conclusions: Donor smoking associates with a modest increase in PGD risk but not with increased recipient mortality. Use of lungs from smokers is likely safe and may increase lung donor availability. Clinical trial registered with www.clinicaltrials.gov (NCT00552357).

CD94+ natural killer cells potentiate pulmonary ischaemia-reperfusion injury.

BACKGROUND: Pulmonary ischaemia-reperfusion injury (IRI) is a major contributor to poor lung transplant outcomes. We recently demonstrated a central role of airway-centred natural killer (NK) cells in mediating IRI; however, there are no existing effective therapies for directly targeting NK cells in humans. METHODS: We hypothesised that a depleting anti-CD94 monoclonal antibody (mAb) would provide therapeutic benefit in mouse and human models of IRI based on high levels of KLRD1 (CD94) transcripts in bronchoalveolar lavage samples from lung transplant patients. RESULTS: We found that CD94 is highly expressed on mouse and human NK cells, with increased expression during IRI. Anti-mouse and anti-human mAbs against CD94 showed effective NK cell depletion in mouse and human models and blunted lung damage and airway epithelial killing, respectively. In two different allogeneic orthotopic lung transplant mouse models, anti-CD94 treatment during induction reduced early lung injury and chronic inflammation relative to control therapies. Anti-CD94 did not increase donor antigen-presenting cells that could alter long-term graft acceptance. CONCLUSIONS: Lung transplant induction regimens incorporating anti-CD94 treatment may safely improve early clinical outcomes.

Evaluation of Crushed Posaconazole Delayed Release Tablets in Lung Transplant Recipients.

BACKGROUND: Invasive fungal infections can cause serious complications after lung transplant; therefore, prophylaxis with posaconazole is common. The posaconazole delayed-release (DR) tablet is preferred. Although the package insert states DR tablets cannot be crushed, recent data suggest it is reasonable. We hypothesized that crushed posaconazole DR tablets could reach therapeutic levels in lung transplant recipients. METHODS: A retrospective study of lung transplant recipients between January 2018 and July 2023, who received crushed posaconazole DR for at least 5 days was completed. Posaconazole troughs were evaluated, and differences were compared between subjects who were therapeutic to those who were subtherapeutic. A cost analysis was also performed. RESULTS: Thirty subjects received crushed posaconazole DR and 50% were therapeutic. The median trough was 1 mg/L for those who were therapeutic and 0.4 mg/L for those who were not (p < 0.001). The median cumulative dose was 2000 mg, and there were no significant differences in the incidence of diarrhea or tube feeds. More subjects in the therapeutic group were loaded (33% vs. 13%), although this was not statistically significant (p = 0.39). No subjects had breakthrough aspergillus one month after starting crushed therapy. CONCLUSION: Crushed posaconazole DR tablets are a viable and cost savings option, but loading doses and higher maintenance doses may be required to reach therapeutic levels. Those who received loading doses (intravenously or crushed) followed by a daily crushed dose of 400 mg were more likely to be therapeutic. Limitations of our study include that it is single-center, small in sample size, and retrospective.

The Lung Allocation Score Remains Inequitable for Patients with Pulmonary Arterial Hypertension, Even after the 2015 Revision.

Rationale: The lung allocation score (LAS) was revised in 2015 to improve waiting list mortality and rate of transplant for patients with pulmonary arterial hypertension (PAH). Objectives: We sought to determine if the 2015 revision achieved its intended goals. Methods: Using the Standard Transplant Analysis and Research file, we assessed the impact of the 2015 LAS revision by comparing the pre- and postrevision eras. Registrants were divided into the LAS diagnostic categories: group A-chronic obstructive pulmonary disease; group B-pulmonary arterial hypertension; group C-cystic fibrosis; and group D-interstitial lung disease. Competing risk regressions were used to assess the two mutually exclusive competing risks of waiting list death and transplant. Cumulative incidence plots were created to visually inspect risks. Measurements and Main Results: The LAS at organ matching increased by 14.2 points for registrants with PAH after the 2015 LAS revision, the greatest increase among diagnostic categories (other LAS categories: Δ, -0.9 to +2.8 points). Before the revision, registrants with PAH had the highest risk of death and lowest likelihood of transplant. After the 2015 revision, registrants with PAH still had the highest risk of death, now similar to those with interstitial lung disease, and the lowest rate of transplant, now similar to those with chronic obstructive pulmonary disease. Conclusions: Although the 2015 LAS revision improved access to transplant and reduced the risk of waitlist death for patients with PAH, it did not go far enough. Significant differences in waitlist mortality and likelihood of transplant persist.

CD16+ natural killer cells in bronchoalveolar lavage are associated with antibody-mediated rejection and chronic lung allograft dysfunction.

Acute and chronic rejections limit the long-term survival after lung transplant. Pulmonary antibody-mediated rejection (AMR) is an incompletely understood driver of long-term outcomes characterized by donor-specific antibodies (DSAs), innate immune infiltration, and evidence of complement activation. Natural killer (NK) cells may recognize DSAs via the CD16 receptor, but this complement-independent mechanism of injury has not been explored in pulmonary AMR. CD16+ NK cells were quantified in 508 prospectively collected bronchoalveolar lavage fluid samples from 195 lung transplant recipients. Associations between CD16+ NK cells and human leukocyte antigen mismatches, DSAs, and AMR grade were assessed by linear models adjusted for participant characteristics and repeat measures. Cox proportional hazards models were used to assess CD16+ NK cell association with chronic lung allograft dysfunction and survival. Bronchoalveolar lavage fluid CD16+ NK cell frequency was associated with increasing human leukocyte antigens mismatches and increased AMR grade. Although NK frequencies were similar between DSA+ and DSA- recipients, CD16+ NK cell frequencies were greater in recipients with AMR and those with concomitant allograft dysfunction. CD16+ NK cells were associated with long-term graft dysfunction after AMR and decreased chronic lung allograft dysfunction-free survival. These data support the role of CD16+ NK cells in pulmonary AMR.

Frailty and genetic risk predict fracture after lung transplantation.

Fractures negatively impact quality of life and survival. We hypothesized that recipient frailty score and genetic profile measured before transplant would predict risk of fracture after lung transplant. We conducted a retrospective cohort study of bone mineral density (BMD) and fracture among lung transplant recipients at a single center. The association between predictors and outcomes were assessed by multivariable time-dependent Cox models or regression analysis. Among the 284 participants, osteoporosis and fracture were highly prevalent. Approximately 59% of participants had posttransplant osteopenia, and 35% of participants developed at least 1 fracture. Low BMD was associated with a polygenic osteoporosis risk score, and the interaction between genetic score and BMD predicted fracture. Pretransplant frailty was associated with risk for spine and hip fracture, which were not associated with chronic lung allograft dysfunction or death. Chest fractures were the most frequent type of fracture and conferred a 2.2-fold increased risk of chronic lung allograft dysfunction or death (time-dependent P < .001). Pneumonia, pleural effusions, and acute rejection frequently occurred surrounding chest fracture. Pretransplant frailty and recipient genotype may aid clinical risk stratification for fracture after transplant. Fracture carries significant morbidity, underscoring the importance of surveillance and osteoporosis prevention.

Subphenotypes of frailty in lung transplant candidates.

Heterogeneous frailty pathobiology might explain the inconsistent associations observed between frailty and lung transplant outcomes. A Subphenotype analysis could refine frailty measurement. In a 3-center pilot cohort study, we measured frailty by the Short Physical Performance Battery, body composition, and serum biomarkers reflecting causes of frailty. We applied latent class modeling for these baseline data. Next, we tested class construct validity with disability, waitlist delisting/death, and early postoperative complications. Among 422 lung transplant candidates, 2 class model fit the best (P = .01). Compared with Subphenotype 1 (n = 333), Subphenotype 2 (n = 89) was characterized by systemic and innate inflammation (higher IL-6, CRP, PTX3, TNF-R1, and IL-1RA); mitochondrial stress (higher GDF-15 and FGF-21); sarcopenia; malnutrition; and lower hemoglobin and walk distance. Subphenotype 2 had a worse disability and higher risk of waitlist delisting or death (hazards ratio: 4.0; 95% confidence interval: 1.8-9.1). Of the total cohort, 257 underwent transplant (Subphenotype 1: 196; Subphenotype 2: 61). Subphenotype 2 had a higher need for take back to the operating room (48% vs 28%; P = .005) and longer posttransplant hospital length of stay (21 days [interquartile range: 14-33] vs 18 days [14-28]; P = .04). Subphenotype 2 trended toward fewer ventilator-free days, needing more postoperative extracorporeal membrane oxygenation and dialysis, and higher need for discharge to rehabilitation facilities (P ≤ .20). In this early phase study, we identified biological frailty Subphenotypes in lung transplant candidates. A hyperinflammatory, sarcopenic Subphenotype seems to be associated with worse clinical outcomes.

European Respiratory Society statement on frailty in adults with chronic lung disease.

Frailty is a complex, multidimensional syndrome characterised by a loss of physiological reserves that increases a person's susceptibility to adverse health outcomes. Most knowledge regarding frailty originates from geriatric medicine; however, awareness of its importance as a treatable trait for people with chronic respiratory disease (including asthma, COPD and interstitial lung disease) is emerging. A clearer understanding of frailty and its impact in chronic respiratory disease is a prerequisite to optimise clinical management in the future. This unmet need underpins the rationale for undertaking the present work. This European Respiratory Society statement synthesises current evidence and clinical insights from international experts and people affected by chronic respiratory conditions regarding frailty in adults with chronic respiratory disease. The scope includes coverage of frailty within international respiratory guidelines, prevalence and risk factors, review of clinical management options (including comprehensive geriatric care, rehabilitation, nutrition, pharmacological and psychological therapies) and identification of evidence gaps to inform future priority areas of research. Frailty is underrepresented in international respiratory guidelines, despite being common and related to increased hospitalisation and mortality. Validated screening instruments can detect frailty to prompt comprehensive assessment and personalised clinical management. Clinical trials targeting people with chronic respiratory disease and frailty are needed.

Biofire pneumonia panel in lung donors: faster detection but limited pathogens.

BACKGROUND: Culture of bronchoalveolar lavage (BAL) specimens takes time to report. We tested whether a molecular diagnostic test could accelerate donor lung assessment and treatment. METHODS: We compared BioFire Film Array Pneumonia Panel (BFPP) with standard of care (SOC) tests on lung allograft samples at three time points: (1) donor BAL at organ recovery, (2) donor bronchial tissue and airway swab at implantation, and (3) first recipient BAL following lung implantation. Primary outcomes were the difference in time to result (Wilcoxon signed-ranked tests) and the agreement in results between BFPP and SOC assays (Gwet's agreement coefficient). RESULTS: We enrolled 50 subjects. In donor lung BAL specimens, BFPP detected 52 infections (14 out of 26 pathogens in the panel). Viral and bacterial BFPP results were reported 2.4 h (interquartile range, IQR 2.0-6.4) following BAL versus 4.6 h (IQR 1.9-6.0, p = 0.625) for OPO BAL viral SOC results and 66 h (IQR 47-87, p < .0001) for OPO BAL bacterial SOC results. Although there was high overall agreement of results between BAL-BFPP versus OPO BAL-SOC tests (Gwet's AC p < .001 for all), the level of agreement differed among 26 pathogens designed in BFPP and differed by types of specimens. BFPP could not detect many infections identified by SOC assays. CONCLUSIONS: BFPP decreased time to detection of lung pathogens among donated lungs, but it cannot replace SOC tests due to the limited number of pathogens in the panel.

Inflammation on bronchoalveolar lavage cytology is associated with decreased chronic lung allograft dysfunction-free survival.

BACKGROUND: Lung transplant recipients undergo bronchoalveolar lavage (BAL) to detect antecedents of chronic lung allograft dysfunction (CLAD), but routine assessment of BAL cytology is controversial. We hypothesized that inflammation on BAL cytology would predict CLAD-free survival. METHODS: In a single-center retrospective cohort, associations between cytology results and clinical characteristics were compared using generalized-estimating equation-adjusted regression. The association between BAL inflammation and CLAD or death risk was assessed using time-dependent Cox models. RESULTS: In 3365 cytology reports from 451 subjects, inflammation was the most common finding (6.2%, 210 cases), followed by fungal forms (5.3%, 178 cases, including 24 cases of suspected Aspergillus). Inflammation on BAL cytology was more common in procedures for symptoms (8.5%) versus surveillance (3.2%, p < .001). Inflammation on cytology was associated with automated neutrophil and lymphocyte counts, acute cellular rejection, infection, and portended a 2.2-fold hazard ratio (CI 1.2-4.0, p = .007) for CLAD or death. However, inflammation by cytology did not inform CLAD-free survival risk beyond automated BAL cell counts (p = .57). CONCLUSIONS: Inflammation on BAL cytology is clinically significant, suggesting acute rejection or infection and increased risk of CLAD or death. However, other indicators of allograft inflammation can substitute for much of the information provided by BAL cytology.

Lung transplantation from swimming pool drowning victims: A case series.

The use of donor lungs from victims of drowning remains a rare occurrence, given concerns over lung parenchymal injury and microbial contamination secondary to aspiration. Given this infrequency, there is a relative paucity of literature surrounding the use of organs from drowned donors, with the few that exist on this subject focusing primarily on cases of drowning in naturally occurring bodies of water (i.e., drowning at sea). Little is known regarding the outcomes of utilizing donor lungs from victims of drowning in artificial bodies of water (i.e., swimming pools). Here, we describe three cases of bilateral lung transplantation from donors who drowned in swimming pools, with good short- and long-term outcomes. These cases lend further evidence to the feasibility of using such organs that have traditionally been viewed with much trepidation. With continually growing demand for donor organs, the use of drowned donor lungs may serve as a means to expand the donor pool and lessen the burden of waitlist mortality.

Frailty and aging-associated syndromes in lung transplant candidates and recipients.

Many lung transplant candidates and recipients are older and frailer compared to previous eras. Older patients are at increased risk for pre- and posttransplant mortality, but this risk is not explained by numerical age alone. This manuscript represents the product of the American Society of Transplantation (AST) conference on frailty. Experts in the field reviewed the latest published research on assessment of elderly and frail lung transplant candidates. Physical frailty, often defined as slowness, weakness, low physical activity, shrinking, and exhaustion, and frailty evaluation is an important tool for evaluation of age-associated dysfunction. Another approach is assessment by cumulative deficits, and both types of frailty are common in lung transplant candidates. Frailty is associated with death or delisting before transplant, and may be associated with posttransplant mortality. Sarcopenia, cognitive dysfunction, depression, and nutrition are other important components for patient evaluation. Aging-associated inflammation, telomere dysfunction, and adaptive immune system senescence may also contribute to frailty. Developing tools for frailty assessment and interventions holds promise for improving patient outcomes before and after lung transplantation.

Chronic lung allograft dysfunction small airways reveal a lymphocytic inflammation gene signature.

Chronic lung allograft dysfunction (CLAD) is the major barrier to long-term survival following lung transplantation, and new mechanistic biomarkers are needed. Lymphocytic bronchitis (LB) precedes CLAD and has a defined molecular signature. We hypothesized that this LB molecular signature would be associated with CLAD in small airway brushings independent of infection. We quantified RNA expression from small airway brushings and transbronchial biopsies, using RNAseq and digital RNA counting, respectively, for 22 CLAD cases and 27 matched controls. LB metagene scores were compared across CLAD strata by Wilcoxon rank sum test. We performed unbiased host transcriptome pathway and microbial metagenome analysis in airway brushes and compared machine-learning classifiers between the two tissue types. This LB metagene score was increased in CLAD airway brushes (p = .002) and improved prediction of graft failure (p = .02). Gene expression classifiers based on airway brushes outperformed those using transbronchial biopsies. While infection was associated with decreased microbial alpha-diversity (p ≤ .04), neither infection nor alpha-diversity was associated with LB gene expression. In summary, CLAD was associated with small airway gene expression changes not apparent in transbronchial biopsies in this cohort. Molecular analysis of airway brushings for diagnosing CLAD merits further examination in multicenter cohorts.

Primary graft dysfunction attenuates improvements in health-related quality of life after lung transplantation, but not disability or depression.

Disability, depressive symptoms, and impaired health-related quality of life (HRQL) are common among patients with life-threatening respiratory compromise. We sought to determine if primary graft dysfunction (PGD), a syndrome of acute lung injury, attenuates improvements in patient-reported outcomes after transplantation. In a single-center prospective cohort, we assessed disability, depressive symptoms, and HRQL before and at 3- to 6-month intervals after lung transplantation. We estimated the magnitude of change in disability, depressive symptoms, and HRQL with hierarchical segmented linear mixed-effects models. Among 251 lung transplant recipients, 50 developed PGD Grade 3. Regardless of PGD severity, participants had improvements in disability and depressive symptoms, as well as generic-physical, generic-mental, respiratory-specific, and health-utility HRQL, exceeding 1- to 4-fold the minimally clinically important difference across all instruments. Participants with PGD Grade 3 had a lower magnitude of improvement in generic-physical HRQL and health-utility than in all other participants. Among participants with PGD Grade 3, prolonged mechanical ventilation was associated with greater attenuation of improvements. PGD remains a threat to the 2 primary aims of lung transplantation, extending survival and improving HRQL. Attenuation of improvement persists long after hospital discharge. Future studies should assess if interventions can mitigate the impact of PGD on patient-reported outcomes.

Type-1 immunity and endogenous immune regulators predominate in the airway transcriptome during chronic lung allograft dysfunction.

Chronic lung allograft dysfunction (CLAD) remains the major complication limiting long-term survival among lung transplant recipients (LTRs). Limited understanding of CLAD immunopathogenesis and a paucity of biomarkers remain substantial barriers for earlier detection and therapeutic interventions for CLAD. We hypothesized the airway transcriptome would reflect key immunologic changes in disease. We compared airway brush-derived transcriptomic signatures in CLAD (n = 24) versus non-CLAD (n = 21) LTRs. A targeted assessment of the proteome using concomitant bronchoalveolar lavage (BAL) fluid for 24 cytokines/chemokines and alloimmune T cell responses was performed to validate the airway transcriptome. We observed an airway transcriptomic signature of differential genes expressed (DGEs) in CLAD marked by Type-1 immunity and striking upregulation of two endogenous immune regulators: indoleamine 2, 3 dioxygenase 1 (IDO-1) and tumor necrosis factor receptor superfamily 6B (TNFRSF6B). Advanced CLAD staging was associated with a more intense airway transcriptome signature. In a validation cohort using the identified signature, we found an area under the curve (AUC) of 0.77 for CLAD LTRs. Targeted proteomic analyses revealed a predominant Type-1 profile with detection of IFN-γ, TNF-α, and IL-1ß as dominant CLAD cytokines, correlating with the airway transcriptome. The airway transcriptome provides novel insights into CLAD immunopathogenesis and biomarkers that may impact diagnosis of CLAD.

Thermocapillary dewetting-based dynamic spatial light modulator.

Dynamic spatial light modulators (SLMs) are capable of precisely modulating a beam of light by tuning the phase or intensity of an array of pixels in parallel. They can be utilized in applications ranging from image projection to beam front aberration and microscopic particle manipulation with optical tweezers. However, conventional dynamic SLMs are typically incompatible with high-power sources, as they contain easily damaged optically absorbing components. To address this, we present an SLM that utilizes a viscous film with a local thickness controlled via thermocapillary dewetting. The film is reflowable and can cycle through different patterns, representing, to the best of our knowledge, the first steps towards a dynamic optical device based on the thermocapillary dewetting mechanism.

Mobile health technology to improve emergent frailty after lung transplantation.

We evaluated the feasibility, safety, and efficacy of a mHealth-supported physical rehabilitation intervention to treat frailty in a pilot study of 18 lung transplant recipients. Frail recipients were defined by a short physical performance battery (SPPB score ≤7). The primary intervention modality was Aidcube, a customizable rehabilitation mHealth platform. Our primary aims included tolerability, feasibility, and acceptability of use of the platform, and secondary outcomes were changes in SPPB and in scores of physical activity, and disability measured using the Duke Activity Status Index (DASI) and Lung Transplant-Value Life Activities (LT-VLA). Notably, no adverse events were reported. Subjects reported the app was easy to use, usability improved over time, and the app enhanced motivation to engage in rehabilitation. Comments highlighted the complexities of immediate post-transplant rehabilitation, including functional decline, pain, tremor, and fatigue. At the end of the intervention, SPPB scores improved a median of 5 points from a baseline of 4. Physical activity and patient-reported disability also improved. The DASI improved from 4.5 to 19.8 and LT-VLA score improved from 2 to 0.59 at closeout. Overall, utilization of a mHealth rehabilitation platform was safe and well received. Remote rehabilitation was associated with improvements in frailty, physical activity and disability. Future studies should evaluate mHealth treatment modalities in larger-scale randomized trials of lung transplant recipients.

Rapid molecular detection of airway pathogens in lung transplant recipients.

BACKGROUND: Airway infections are difficult to distinguish from acute rejection in lung transplant recipients. Traditional culture techniques take time that may delay treatment. We hypothesized that a rapid multiplex molecular assay could improve time to diagnosis and appropriate clinical decision making. METHODS: In a prospective observational study of recipients undergoing bronchoscopy, we assessed the BioFire® FilmArray® Pneumonia Panel (BFPP) in parallel to standard of care (SOC) diagnostics. Research clinicians performed shadow (research only) clinical decision making in real time. Time to report and interpretation were reported as median and interquartile ranges and compared by Wilcoxon signed-ranked test. Agreement was defined based on detection of any species targeted in the molecular assay. RESULTS: For the 150 enrolled subjects, BFPP results were available 3.8 hours (IQR 2.8-5.1) following bronchoscopy, compared to 13 hours for viral SOC (IQR 10-34, P < .001) results and 48 hours for bacterial SOC (IQR 46-70, P < .001) results. Positive BFPP results were interpreted in 9 hours (IQR 5-20) following bronchoscopy, compared to 74 hours for SOC (IQR 37-110, P < .001). Assays agreed for 138 (92%) of the 150 subjects. Of 22 BFPP diagnoses, five (23%) resulted in a shadow antibiotic recommendation. Notable BFPP deficiencies included fungal species and H parainfluenzae, accounting for 15 (27%) and 13 (23%) of the 56 actionable SOC results, respectively. CONCLUSIONS: This molecular diagnostic including bacterial targets has the potential to shorten time to diagnosis and augment current clinical decision making but cannot replace SOC culture methods.

Mitochondrial DNA Stimulates TLR9-Dependent Neutrophil Extracellular Trap Formation in Primary Graft Dysfunction.

The immune system is designed to robustly respond to pathogenic stimuli but to be tolerant to endogenous ligands to not trigger autoimmunity. Here, we studied an endogenous damage-associated molecular pattern, mitochondrial DNA (mtDNA), during primary graft dysfunction (PGD) after lung transplantation. We hypothesized that cell-free mtDNA released during lung ischemia-reperfusion triggers neutrophil extracellular trap (NET) formation via TLR9 signaling. We found that mtDNA increases in the BAL fluid of experimental PGD (prolonged cold ischemia followed by orthotopic lung transplantation) and not in control transplants with minimal warm ischemia. The adoptive transfer of mtDNA into the minimal warm ischemia graft immediately before lung anastomosis induces NET formation and lung injury. TLR9 deficiency in neutrophils prevents mtDNA-induced NETs, and TLR9 deficiency in either the lung donor or recipient decreases NET formation and lung injury in the PGD model. Compared with human lung transplant recipients without PGD, severe PGD was associated with high levels of BAL mtDNA and NETs, with evidence of relative deficiency in DNaseI. We conclude that mtDNA released during lung ischemia-reperfusion triggers TLR9-dependent NET formation and drives lung injury. In PGD, DNaseI therapy has a potential dual benefit of neutralizing a major NET trigger (mtDNA) in addition to dismantling pathogenic NETs.