Survival in sensitized lung transplant recipients with perioperative desensitization

Bronchoalveolar lavage cytokine-based risk stratification of clinically-stable lung transplant recipients with undefined rejection: Further insights from a follow-up investigation

BACKGROUND

Surveillance bronchoscopies with bronchoalveolar lavage (BAL) and transbronchial biopsies (TBB) are primarily used to detect acute cellular rejection (ACR) or infection in lung transplant (LTx) recipients. We previously identified a BAL protein signature associated with chronic lung allograft dysfunction (CLAD) or death/retransplant in patients with stable minimal (grade A1) ACR. This present study aimed to determine whether similar BAL biomarkers predict outcomes in stable patients when ACR grade is undetermined.

METHODS

The cohort included all adult, first bilateral LTx performed 2010-2017. Clinical status was categorized as unstable or stable based on the presence or absence of a ≥ 10% drop in FEV1. Clinically-stable patients with grade AX TBB (inadequate biopsies) during the first year post-transplant, not preceded by ACR (grade A≥1 or B≥1), were included. IL6, S100A8, IL10, TNF-receptor-1, IL1α, pentraxin3, and CXCL10 were measured in the BAL using a multiplex bead assay. Associations with subsequent CLAD or death/retransplant were assessed using multivariable Cox proportional hazards models, adjusted for relevant clinical covariates.

RESULTS

Among 107 patients with stable AX biopsies at a median of 188 days post-transplant, the median times from biopsy to CLAD and death/retransplant were 972 and 1410 days, respectively. CXCL10 was significantly associated with CLAD, while IL6, S100A8, pentraxin3, TNF-receptor-1, and IL10 were associated with death/retransplant (p < 0.05 for all).

CONCLUSION

A focused BAL protein signature in stable patients with ungradable TBB early post-transplant may predict worse outcomes. Such select BAL biomarkers may identify patients who require more aggressive management strategies or closer monitoring.

Perioperative C1-esterase inhibitor therapy to allow transplantation in a highly sensitized lung transplant candidate: Three case reports

Lung transplant candidates who are highly sensitized against human leucocyte antigen have a lower likelihood of graft allocation and a higher risk of dying while on the waiting list. C1-esterase inhibitor, an inhibitor of the classical and lectin pathways of complement activation, has been used successfully to prevent and treat acute antibody-mediated rejection in kidney and heart transplantation. Here, we report 3 cases of C1-esterase inhibitors used perioperatively in highly sensitized lung transplant candidates, with successful bilateral lung transplants despite severe primary graft dysfunction and/or hyperacute antibody-mediated rejection.

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.

Hospital-Acquired and Ventilator-Associated Pneumonia Early After Lung Transplantation: A Prospective Study on Incidence, Pathogen Origin, and Outcome

BACKGROUND

Hospital-acquired (HAP) and ventilator-associated pneumonia (VAP) are important complications early (<30 days) after lung transplantation (LT). However, current incidence, associated factors, and outcomes are not well reported.

METHODS

LT recipients transplanted at our institution (July 2019-January 2020 and October 2021-November 2022) were prospectively included. We assessed incidence and presentation of pneumonia and evaluated the impact of associated factors using regression models. We also evaluated molecular relatedness of respiratory pathogens collected peri-transplant and at pneumonia occurrence using pulsed-field gel electrophoresis (PFGE).

RESULTS

In the first 30 days post-LT, 25/270 (9.3%) recipients were diagnosed with pneumonia (68% [17/25] VAP; 32% [8/25] HAP). Median time to pneumonia was 11 days (IQR, 7-13); 49% (132/270) of donor and 16% (44/270) of recipient respiratory peri-transplant cultures were positive. However, pathogens associated with pneumonia were not genetically related to either donor or recipient cultures at transplant, as determined by PFGE. Diagnosed pulmonary hypertension (HR, 4.42; 95% CI, 1.62-12.08) and immunosuppression use (HR, 2.87; 95% CI, 1.30-6.56) were pre-transplant factors associated with pneumonia. Pneumonia occurrence was associated with longer hospital stay (HR, 5.44; 95% CI, 2.22-13.37) and VAP with longer ICU stay (HR, 4.31; 95% CI, 1.73-10.75) within the first 30 days post-transplantation; 30- and 90-day mortality were similar.

CONCLUSIONS

Prospectively assessed early pneumonia incidence occurred in ∼10% of LT. Populations at increased risk for pneumonia occurrence include LT with pre-transplant pulmonary hypertension and pre-transplant immunosuppression. Pneumonia was associated with increased healthcare use, highlighting the need for further improvements by preferentially targeting higher-risk patients.

Pushing the Survival Bar Higher: Two Decades of Innovation in Lung Transplantation

Survival after lung transplantation has significantly improved during the last two decades. The refinement of the already existing extracorporeal life support (ECLS) systems, such as extracorporeal membrane oxygenation (ECMO), and the introduction of new techniques for donor lung optimization, such as ex vivo lung perfusion (EVLP), have allowed the extension of transplant indication to patients with end-stage lung failure after acute respiratory distress syndrome (ARDS) and the expansion of the donor organ pool, due to the better evaluation and optimization of extended-criteria donor (ECD) lungs and of donors after circulatory death (DCD). The close monitoring of anti-HLA donor-specific antibodies (DSAs) has allowed the early recognition of pulmonary antibody-mediated rejection (AMR), which requires a completely different treatment and has a worse prognosis than acute cellular rejection (ACR). As such, the standardization of patient selection and post-transplant management has significantly contributed to this positive trend, especially at high-volume centers. This review focuses on lung transplantation after ARDS, on the role of EVLP in lung donor expansion, on ECMO as a principal cardiopulmonary support system in lung transplantation, and on the diagnosis and therapy of pulmonary AMR.

Antibody-Mediated Rejection in Lung Transplantation: Diagnosis and Therapeutic Armamentarium in a 21st Century Perspective

Humoral immunity is a major waypoint towards chronic allograft dysfunction in lung transplantation (LT) recipients. Though allo-immunization and antibody-mediated rejection (AMR) are well-known entities, some diagnostic gaps need to be addressed. Morphological analysis could be enhanced by digital pathology and artificial intelligence-based companion tools. Graft transcriptomics can help to identify graft failure phenotypes or endotypes. Donor-derived cell free DNA is being evaluated for graft-loss risk stratification and tailored surveillance. Preventative therapies should be tailored according to risk. The donor pool can be enlarged for candidates with HLA sensitization, with strategies combining plasma exchange, intravenous immunoglobulin and immune cell depletion, or with emerging or innovative therapies such as imlifidase or immunoadsorption. In cases of insufficient pre-transplant desensitization, the effects of antibodies on the allograft can be prevented by targeting the complement cascade, although evidence for this strategy in LT is limited. In LT recipients with a humoral response, strategies are combined, including depletion of immune cells (plasmapheresis or immunoadsorption), inhibition of immune pathways, or modulation of the inflammatory cascade, which can be achieved with photopheresis. Altogether, these innovative techniques offer promising perspectives for LT recipients and shape the 21st century's armamentarium against AMR.

Intravenous Immunoglobulins Alone for the Desensitization of Lung Transplant Recipients with Preformed Donor Specific Antibodies and Negative Flow Cytometry Crossmatch

BACKGROUND

The lack of evidence regarding optimal desensitization strategies for lung transplant candidates with preformed donor specific anti-human leukocyte antigen antibodies (DSAs) has led to varying approaches among centers towards this patient group. Our institution's desensitization protocol for recipients with preformed DSAs and negative flow cytometry crossmatch (FCXM) consists of intravenous immunoglobulin (IVIG) as the sole therapy. The study aimed to determine outcomes using this approach.

METHODS

This retrospective study included adults who underwent lung-only transplantation for the first time between January 2015 and March 2022 at a single center. We excluded patients with positive or missing FCXM results. Transplant recipients with any DSA ≥ 1000 MFI on latest testing within three months of transplant were considered DSA-positive, while recipients with DSAs <1000 MFI and those without DSAs were assigned to the low-level/negative group. Graft survival (time to death/retransplantation) and chronic lung allograft dysfunction (CLAD)-free times were compared between groups using Cox proportional hazards models.

RESULTS

Thirty-six out of 167 eligible patients (22%) were DSA-positive. At least 50% of preformed DSAs had documented clearance (decrease to <1000 MFI) within the first 6 months of transplant. Multivariable Cox regression analyses did not detect a significantly increased risk of graft failure (aHR 1.04 95%CI 0.55-1.97) or chronic lung allograft dysfunction (aHR 0.71 95%CI 0.34-1.52) in DSA-positive patients compared to patients with low-level/negative DSAs. Incidences of antibody-mediated rejection (p = 1.00) and serious thromboembolic events (p = 0.63) did not differ between study groups.

CONCLUSION

We describe a single-center experience of administering IVIG alone to lung transplant recipients with preformed DSAs and negative FCXM. Further studies are required to confirm the efficacy of this strategy against other protocols.

Association between cytomegalovirus viremia and long-term outcomes in lung transplant recipients

Although cytomegalovirus (CMV) viremia/DNAemia has been associated with reduced survival after lung transplantation, its association with chronic lung allograft dysfunction (CLAD) and its phenotypes is unclear. We hypothesized that, in a modern era of CMV prophylaxis, CMV DNAemia would still remain associated with death, but also represent a risk factor for CLAD and specifically restrictive allograft syndrome (RAS)/mixed phenotype. This was a single-center retrospective cohort study of all consecutive adult, first, bilateral-/single-lung transplants done between 2010-2016, consisting of 668 patients. Risks for death/retransplantation, CLAD, or RAS/mixed, were assessed by adjusted cause-specific Cox proportional-hazards models. CMV viral load (VL) was primarily modeled as a categorical variable: undetectable, detectable to 999, 1000 to 9999, and ≥10 000 IU/mL. In multivariable models, CMV VL was significantly associated with death/retransplantation (≥10 000 IU/mL: HR = 2.65 [1.78-3.94]; P < .01), but was not associated with CLAD, whereas CMV serostatus mismatch was (D+R-: HR = 2.04 [1.30-3.21]; P < .01). CMV VL was not associated with RAS/mixed in univariable analysis. Secondary analyses with a 7-level categorical or 4-level ordinal CMV VL confirmed similar results. In conclusion, CMV DNAemia is a significant risk factor for death/retransplantation, but not for CLAD or RAS/mixed. CMV serostatus mismatch may have an impact on CLAD through a pathway independent of DNAemia.

Design of the STRIVE-IPF trial- study of therapeutic plasma exchange, rituximab, and intravenous immunoglobulin for acute exacerbations of idiopathic pulmonary fibrosis

BACKGROUND

Acute exacerbations of idiopathic pulmonary fibrosis (AE-IPF) affect a significant proportion of patients with IPF. There are limited data to inform therapeutic strategies for AE-IPF, despite its high mortality. We discuss the rationale and design of STRIVE-IPF, a randomized, multi-center, open-label Phase IIb clinical trial to determine the efficacy of combined therapeutic plasma exchange (TPE), rituximab, and intravenous immunoglobulin (IVIG), in comparison to treatment as usual (TAU), among patients with acute IPF exacerbations.

METHODS

The STRIVE-IPF trial will randomize 51 patients among five sites in the United States. The inclusion criteria have been designed to select a study population with AE-IPF, as defined by American Thoracic Society criteria, while excluding patients with an alternative cause for a respiratory decompensation. The primary endpoint of this trial is six-month survival. Secondary endpoints include supplement oxygen requirement and six-minute walk distance which will be assessed immediately prior to treatment and after completion of therapy on day 19, as well as at periodic subsequent visits.

DISCUSSION

The experimental AE-IPF therapy proposed in this clinical trial was adapted from treatment regimens used in other antibody-mediated diseases. The regimen is initiated with TPE, which is expected to rapidly reduce circulating autoantibodies, followed by rituximab to reduce B-cells and finally IVIG, which likely has multiple effects, including affecting feedback inhibition of residual B-cells by Fc receptor occupancy. We have reported potential benefits of this experimental therapy for AE-IPF in previous anecdotal reports. This clinical trial has the potential to profoundly affect current paradigms and treatment approaches to patients with AE-IPF.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03286556.

Impact of intraoperative therapeutic plasma exchange on bleeding in lung transplantation

BACKGROUND

Our program uses a desensitization protocol that includes intraoperative therapeutic plasma exchange (iTPE) for crossmatch-positive lung transplants, which improves access to lung transplant for sensitized candidates while mitigating immunologic risk. Although we have reported excellent outcomes for sensitized patients with the use of this protocol, concern for perioperative bleeding appears to have hindered broader adoption of it at other programs. We conducted a retrospective cohort study to quantify the impact of iTPE on perioperative bleeding in lung transplantation.

METHODS

All first-time lung transplant recipients from 2014 to 2019 who received iTPE were compared to those who did not. Multivariable logistic regression was used to determine the association between iTPE and large-volume perioperative transfusion requirements (≥5 packed red blood cell units within 24 hours of transplant start), adjusted for disease type, transplant type, and extracorporeal membrane oxygenation or cardiopulmonary bypass use. The incidence of hemothorax (requiring reoperation within 7 days of lung transplant) and 30-day posttransplant mortality were compared between the 2 groups using chi-square test.

RESULTS

One hundred forty-two patients (16%) received iTPE, and 755 patients (84%) did not. The mean number of perioperative pRBC transfusions was 4.2 among patients who received iTPE and 2.9 among patients who did not. iTPE was associated with increased odds of requiring large-volume perioperative transfusion (odds ratio 1.9; 95% confidence interval: 1.2-2.9, p-value = 0.007) but was not associated with an increased incidence of hemothorax (5% in both groups, p = 0.99) or 30-day posttransplant mortality (3.5% among patients who received iTPE vs 2.1% among patients who did not, p = 0.31).

CONCLUSIONS

This study demonstrates that the use of iTPE in lung transplantation may increase perioperative bleeding but not to a degree that impacts important posttransplant outcomes.

Design of the STRIVE-IPF Trial- Study of Therapeutic Plasma Exchange, Rituximab, and Intravenous Immunoglobulin for Acute Exacerbations of Idiopathic Pulmonary Fibrosis

Background

Acute exacerbations of idiopathic pulmonary fibrosis (AE-IPF) affect a significant proportion of patients with IPF. There are limited data to inform therapeutic strategies for AEIPF, despite its high mortality. We discuss the rationale and design of STRIVE-IPF, a randomized, multi-center, open-label Phase IIb clinical trial to determine the efficacy of combined therapeutic plasma exchange (TPE), rituximab, and intravenous immunoglobulin (IVIG), in comparison to treatment as usual (TAU), among patients with acute IPF exacerbations.

Methods

The STRIVE-IPF trial will randomize 51 patients among five sites in the United States. The inclusion criteria have been designed to select a study population with AE-IPF, as defined by American Thoracic Society criteria, while excluding patients with an alternative cause for a respiratory decompensation. The primary endpoint of this trial is six-month survival. Secondary endpoints include supplement oxygen requirement and six-minute walk distance which will be assessed immediately prior to treatment and after completion of therapy on day 19, as well as at periodic subsequent visits.

Discussion

The experimental AE-IPF therapy proposed in this clinical trial was adapted from treatment regimens used in other antibody-mediated diseases. The regimen is initiated with TPE, which is expected to rapidly reduce circulating autoantibodies, followed by rituximab to reduce B-cells and finally IVIG, which likely has multiple effects, including affecting feedback inhibition of residual B-cells by Fc receptor occupancy. We have reported potential benefits of this experimental therapy for AE-IPF in previous anecdotal reports. This clinical trial has the potential to profoundly affect current paradigms and treatment approaches to patients with AE-IPF.Trial Registration ClinicalTrials.gov identifier: NCT03286556.

Donor and recipient risk factors for the development of primary graft dysfunction following lung transplantation

Primary Graft Dysfunction (PGD) is a major cause of both short-term and long-term morbidity and mortality following lung transplantation. Various donor, recipient, and technical risk factors have been previously identified as being associated with the development of PGD. Here, we present a comprehensive review of the current literature as it pertains to PGD following lung transplantation, as well as discussing current strategies to mitigate PGD and future directions. We will pay special attention to recent advances in lung transplantation such as ex-vivo lung perfusion, thoracoabdominal normothermic regional perfusion, and up-to-date literature published in the interim since the 2016 ISHLT consensus statement on PGD and the COVID-19 pandemic.

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.

Drug levels after sirolimus initiation and short-term outcomes in ambulatory heart transplantation recipients

INTRODUCTION

We evaluated the effect of relative changes in combined tacrolimus and sirolimus (drug) levels, following sirolimus initiation, on outcomes in ambulatory heart transplantation (HTx) recipients.

METHODS

We performed a retrospective analysis of HTx recipients who received tacrolimus, followed by sirolimus initiation, any time after HTx. We calculated the relative change in combined drug levels 1-month post-sirolimus initiation, relative to tacrolimus levels pre-initiation, and categorized patients into decreased (≥15% decrease), stable (<15% decrease to <15% increase), or increased (≥15% increase) groups. We compared, across the three groups, changes in post-initiation estimated glomerular filtration rate (eGFR) and left ventricular ejection fraction (LVEF) using one-way ANOVA and Šidák's post-hoc analysis, as well as the individual and composite outcomes of new donor specific antibodies (DSA), acute cellular rejection (ACR), and all-cause mortality using Fisher's exact test.

RESULTS

Amongst 99 HTx recipients included, the median age was 53 years, time to sirolimus initiation was 1.5 years post-HTx, and pre-sirolimus eGFR was 52 mL/min/1.73 m2 . Nine patients had decreased, 15 stable, and 75 increased, relative combined drug levels. Relative change in eGFR was significantly higher in patients with decreased levels compared to patients with increased levels at 6 months post-initiation (P < .05), but this was not sustained at 12 months. There were no differences in LVEF change or in individual and composite risks for developing DSA, ACR, and all-cause mortality at 12 months across the groups.

CONCLUSION

Post-sirolimus initiation, a relative decrease in combined drug levels, compared to increased levels, was associated with temporarily improved renal function.

BSHI and BTS UK guideline on the detection of alloantibodies in solid organ (and islet) transplantation

Solid organ transplantation represents the best (and in many cases only) treatment option for patients with end-stage organ failure. The effectiveness and functioning life of these transplants has improved each decade due to surgical and clinical advances, and accurate histocompatibility assessment. Patient exposure to alloantigen from another individual is a common occurrence and takes place through pregnancies, blood transfusions or previous transplantation. Such exposure to alloantigen's can lead to the formation of circulating alloreactive antibodies which can be deleterious to solid organ transplant outcome. The purpose of these guidelines is to update to the previous BSHI/BTS guidelines 2016 on the relevance, assessment, and management of alloantibodies within solid organ transplantation.

Outcomes after flow cytometry crossmatch-positive lung transplants managed with perioperative desensitization

Our program previously reported successful outcomes following virtual crossmatch (VXM)-positive lung transplants managed with perioperative desensitization, but our ability to stratify their immunologic risk was limited without flow cytometry crossmatch (FCXM) data before 2014. The aim of this study was to determine allograft and chronic lung allograft dysfunction (CLAD)-free survival following VXM-positive/FCXM-positive lung transplants, which are performed at a minority of programs due to the high immunologic risk and lack of data on outcomes. All first-time lung transplant recipients between January 2014 and December 2019 were divided into 3 cohorts: VXM-negative (n = 764), VXM-positive/FCXM-negative (n = 64), and VXM-positive/FCXM-positive (n = 74). Allograft and CLAD-free survival were compared using Kaplan-Meier and multivariable Cox proportional hazards models. Five-year allograft survival was 53% in the VXM-negative cohort, 64% in the VXM-positive/FCXM-negative cohort, and 57% in the VXM-positive/FCXM-positive cohort (P = .7171). Five-year CLAD-free survival was 53% in the VXM-negative cohort, 60% in the VXM-positive/FCXM-negative cohort, and 63% in the VXM-positive/FCXM-positive cohort (P = .8509). This study confirms that allograft and CLAD-free survival of patients who undergo VXM-positive/FCXM-positive lung transplants with the use of our protocol does not differ from those of other lung transplant recipients. Our protocol for VXM-positive lung transplants improves access to transplant for sensitized candidates and mitigates even high immunologic risk.

Lung transplantation despite preformed donor-specific antihuman leukocyte antigen antibodies: a 9-year single-center experience

Pretransplant allosensitization to human leukocyte antigens (HLA) increases the recipient's waiting list time and mortality in lung transplantation. Rather than waiting for crossmatch-negative donors, since 2013, recipients with preformed donor-specific antiHLA antibodies (pfDSA) have been managed with repeated IgA- and IgM-enriched intravenous immunoglobulin (IgGAM) infusions, usually in combination with plasmapheresis before IgGAM and a single dose of antiCD20 antibody. This retrospective study presents our 9-year experience with patients transplanted with pfDSA. Records of patients transplanted between February 2013 and May 2022 were reviewed. Outcomes were compared between patients with pfDSA and those without any de novo donor-specific antiHLA antibodies. The median follow-up time was 50 months. Of the 1,043 patients who had undergone lung transplantation, 758 (72.7%) did not develop any early donor-specific antiHLA antibodies, and 62 (5.9%) patients exhibited pfDSA. Among the 52 (84%) patients who completed treatment, pfDSA was cleared in 38 (73%). In pfDSA vs control patients and at 8-year follow-up, respectively, graft survival (%) was 75 vs 65 (P = .493) and freedom from chronic lung allograft dysfunction (%) was 63 vs 65 (P = .525). In lung transplantation, crossing the preformed HLA-antibody barrier is safe using a treatment protocol based on IgGAM. Patients with pfDSA have a good 8-year graft survival rate and freedom from chronic lung allograft dysfunction, similar to control patients.

Preemptive immune globulin therapy in sensitized lung transplant recipients

BACKGROUND

Sensitized lung transplant recipients are at increased risk of developing donor-specific antibodies, which have been associated with acute and chronic rejection. Perioperative intravenous immune globulin has been used in sensitized individuals to down-regulate antibody production.

METHODS

We compared patients with a pre-transplant calculated panel reactive antibody ≥25% who did not receive preemptive immune globulin therapy to a historical control that received preemptive immune globulin therapy. Our cohort included 59 patients, 17 patients did not receive immune globulin therapy and 42 patients received therapy.

RESULTS

Donor specific antibody development was numerically higher in the non-immune globulin group compared to the immune globulin group (58.8% vs 33.3%, respectively, odds ratio 2.80, 95% confidence interval [0.77, 10.79], p = 0.13). Median time to antibody development was 9 days (Q1, Q3: 7, 19) and 28 days (Q1, Q3: 7, 58) in the non-immune globulin and immune globulin groups, respectively. There was no significant difference between groups in the incidence of primary graft dysfunction at 72 h post-transplant or acute cellular rejection, antibody-mediated rejection, and chronic lung allograft dysfunction at 12 months.

CONCLUSION

These findings are hypothesis generating and emphasize the need for larger, randomized studies to determine association of immune globulin therapy with clinical outcomes.

Management of donor-specific antibodies in lung transplantation

The formation of antibodies against donor human leukocyte antigens poses a challenging problem both for donor selection as well as postoperative graft function in lung transplantation. These donor-specific antibodies limit the pool of potential donor organs and are associated with episodes of antibody-mediated rejection, chronic lung allograft dysfunction, and increased mortality. Optimal management strategies for clearance of DSAs are poorly defined and vary greatly by institution; most of the data supporting any particular strategy is limited to small-scale retrospective cohort studies. A typical approach to antibody depletion may involve the use of high-dose steroids, plasma exchange, intravenous immunoglobulin, and possibly other immunomodulators or small-molecule therapies. This review seeks to define the current understanding of the significance of DSAs in lung transplantation and outline the literature supporting strategies for their management.

Preemptive treatment of de novo donor-specific antibodies in lung transplant patients reduces subsequent risk of chronic lung allograft dysfunction or death

The development of donor-specific antibodies after lung transplantation is associated with downstream acute cellular rejection, antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), or death. It is unknown whether preemptive (early) treatment of de novo donor-specific antibodies (dnDSAs), in the absence of clinical signs and symptoms of allograft dysfunction, reduces the risk of subsequent CLAD or death. We performed a multicenter, retrospective cohort study to determine if early treatment of dnDSAs in lung transplant patients reduces the risk of the composite endpoint of CLAD or death. In the cohort of 445 patients, 145 patients developed dnDSAs posttransplant. Thirty patients received early targeted treatment for dnDSAs in the absence of clinical signs and symptoms of AMR. Early treatment of dnDSAs was associated with a decreased risk of CLAD or death (hazard ratio, 0.36; 95% confidence interval, 0.17-0.76; P < .01). Deferring treatment until the development of clinical AMR was associated with an increased risk of CLAD or death (hazard ratio, 3.00; 95% confidence interval, 1.46-6.18; P < .01). This study suggests that early, preemptive treatment of donor-specific antibodies in lung transplant patients may reduce the subsequent risk of CLAD or death.

Donor and recipient human leukocyte antigen-G polymorphisms modulate the risk of adverse immunologic events following lung transplantation

The long-term benefits of lung transplantation (LTx) are limited by pathogenic alloimmune responses that drive injury, inflammation, and chronic dysfunction. Human leukocyte antigen-G (HLA-G) plays a key role in the modulation of these pathways. This study assesses the impact of the HLA-G genotype on immunologic risk and survival following LTx. This retrospective cohort study included 289 bilateral LTx. Recipient and donor HLA-G genotypes were analyzed to identify associations with de novo donor-specific antibodies, acute rejection, chronic lung allograft dysfunction, and allograft survival. We further assessed these associations, both individually and in paired analysis, based on a grouped haplotype classification of HLA-G expression. Donor HLA-G single nucleotide polymorphisms were associated with allograft injury, the onset of chronic lung allograft dysfunction following injury, and allograft survival. Recipient HLA-G single nucleotide polymorphisms were associated with allograft injury, cellular rejection, and donor-specific antibody formation. "Low HLA-G expression" donor haplotypes were associated with impaired allograft survival, as were "low HLA-G expression" donor-recipient haplotype pairs. This study provides compelling evidence for the role of HLA-G in modulating immunologic risk after LTx. Our results highlight the importance of both donor and recipient HLA-G genotypes on the overall risk profile and underscore the lasting influence of donor genotype on lung transplant outcomes.

Antibody-Mediated Rejection: Diagnosis and Treatment

Antibody-mediated rejection (AMR) is a form of lung allograft rejection that is emerging as an important risk factor for chronic lung allograft dysfunction and decreased long-term survival. In this review, we provide a brief overview of our current understanding of its pathophysiology with an emphasis on donor-specific antibodies before moving on to focus on the current diagnostic criteria and treatment strategies. Our goal is to discuss the limitations of our current knowledge and explore how novel diagnostic and therapeutic options aim to improve outcomes through earlier definitive diagnosis and preemptive targeted treatment.

The Highly Sensitized Recipient: Pretransplant and Posttransplant Considerations

Highly sensitized patients, who are often black and Hispanic women, are less likely to be listed for lung transplant and are at higher risk for prolonged waitlist time and waitlist death. In this review, the authors discuss strategies for improving access to transplant in this population, including risk stratification of crossing pretransplant donor-specific antibodies, based on antibody characteristics. The authors also review institutional protocols, such as perioperative desensitization, for tailoring transplant immunosuppression in the highly sensitized population. The authors conclude with suggestions for future research, including development of novel donor-specific antibody-directed therapeutics.

Statin Use May Be Associated With a Lower Risk of Invasive Aspergillosis in Lung Transplant Recipients

BACKGROUND

Statins are competitive inhibitors of 3-hydroxy-3methylglutaryl coenzyme A reductase (HMG-CoA reductase) that catalyses HMG-CoA conversion to mevalonate, a process involved in synthesizing cholesterol in humans and ergosterol in fungi. The effect of statin use on the risk of development of invasive aspergillosis (IA) in lung transplant recipients (LTRs) is not well documented.

METHODS

This retrospective study included LTRs from 2010 to 2017 who were followed for one-year post-transplant. Proven or probable IA was diagnosed as per ISHLT criteria. We performed a multivariable Cox proportional hazards model of the association between IA and statin use (minimum of 2 weeks duration prior to IA), adjusting for other known IA risk factors.

RESULTS

We identified 785 LTRs, 44% female, mean age 53 years old, the most common underlying disease being pulmonary fibrosis (23.8%). In total, 451 LTRs (57%) received statins post-transplant, atorvastatin was the most commonly used statin (68%). The mean duration of statins post-transplant was 347 days (interquartile range [IQR]: 305 to 346). And 55 (7%) LTRs developed IA in the first-year post-transplant. Out of these 55 LTRs, 9 (16.3%) had received statin before developing IA. In multivariable analysis, statin use was independently associated with a lower risk of IA (P = .002, SHR 0.30, 95% confidence interval [CI] 95% .14-.64). Statin use was also associated with a lower incidence of post-transplant Aspergillus colonization, 114 (34%) in the no statin group vs 123 (27%) in the statin group (P = .038).

CONCLUSIONS

The use of statin for a minimum of two weeks during the first-year post-transplant was associated with a 70% risk reduction of IA in LTRs.

First use of imlifidase desensitization in a highly sensitized lung transplant candidate: a case report

Lung transplant candidates who are highly sensitized against human leucocyte antigen present an ongoing challenge with regards to finding immunologically acceptable donors. Desensitization strategies aimed at reducing preformed donor-specific antibodies have a number of limitations. Imlifidase, an IgG-degrading enzyme derived from Streptococcus pyogenes, is a novel agent that has been used to convert positive crossmatches to negative in kidney transplant candidates, allowing transplantation to occur. We present the first case of imlifidase use for antibody depletion in a highly sensitized lung transplant candidate who went on to undergo a successful bilateral lung transplant.

Lung Allograft Microbiome Association with Gastroesophageal Reflux, Inflammation, and Allograft Dysfunction

Rationale: It remains unclear how gastroesophageal reflux disease (GERD) affects allograft microbial community composition in lung transplant recipients and its impact on lung allograft inflammation and function. Objectives: Our objective was to compare the allograft microbiota in lung transplant recipients with or without clinically diagnosed GERD in the first year after transplant and assess associations between GERD, allograft microbiota, inflammation, and acute and chronic lung allograft dysfunction (ALAD and CLAD). Methods: A total of 268 BAL samples were collected from 75 lung transplant recipients at a single transplant center every 3 months after transplant for 1 year. Ten transplant recipients from a separate transplant center provided samples before and after antireflux Nissen fundoplication surgery. Microbial community composition and density were measured using 16S ribosomal RNA gene sequencing and quantitative polymerase chain reaction, respectively, and inflammatory markers and bile acids were quantified. Measurements and Main Results: We observed a range of allograft community composition with three discernible types (labeled community state types [CSTs] 1-3). Transplant recipients with GERD were more likely to have CST1, characterized by high bacterial density and relative abundance of the oropharyngeal colonizing genera Prevotella and Veillonella. GERD was associated with more frequent transitions to CST1. CST1 was associated with lower inflammatory cytokine concentrations than pathogen-dominated CST3 across the range of microbial densities observed. Cox proportional hazard models revealed associations between CST3 and the development of ALAD/CLAD. Nissen fundoplication decreased bacterial load and proinflammatory cytokines. Conclusions: GERD was associated with a high bacterial density, Prevotella- and Veillonella-dominated CST1. CST3, but not CST1 or GERD, was associated with inflammation and early development of ALAD and CLAD. Nissen fundoplication was associated with a reduction in microbial density in BAL fluid samples, especially the CST1-specific genus, Prevotella.

Safety of Crossing Donor-specific Antibodies in Lung Transplantation

BACKGROUND

Donor-specific antibodies (DSAs) have been associated with antibody-mediated rejection, chronic lung allograft dysfunction (CLAD), and increased mortality in lung transplant recipients. Our center performs transplants in the presence of DSA, and we sought to evaluate the safety of this practice with respect to graft loss, CLAD onset, and primary graft dysfunction (PGD).

METHODS

We reviewed recipients transplanted from 2010 to 2017, classifying them as DSA positive (DSA+) or negative. We used Kaplan-Meier estimation to test the association between DSA status and time to death or retransplant and time to CLAD onset. We further tested associations with severe PGD and rejection in the first year using logistic regression and Fisher exact testing.

RESULTS

Three hundred thirteen patients met inclusion criteria, 30 (10%) of whom were DSA+. DSA+ patients were more likely to be female, bridged to transplant, and receive induction therapy. There was no association between DSA status and time to death or retransplant (log rank P = 0.581) nor death-censored time to CLAD onset (log rank P = 0.278), but DSA+ patients were at increased risk of severe PGD (odds ratio 2.88; 95% confidence interval, 1.10-7.29; P = 0.031) and more frequent antibody-mediated rejection in the first posttransplant year.

CONCLUSIONS

Crossing DSA at time of lung transplant was not associated with an increased risk of death or CLAD in our cohort, but patients developed severe PGD and antibody-mediated rejection more frequently. However, these risks are likely manageable when balanced against the benefits of expanded access for sensitized candidates.

Fungal infection and colonization in lung transplant recipients with chronic lung allograft dysfunction

BACKGROUND

The incidence and impact of de novo fungal airway colonization and infection in lung transplant recipients (LTRs) with known chronic lung allograft dysfunction (CLAD) has not been established. We aimed to determine the 1-year cumulative incidence and risk factors of de novo fungal colonization or infection in LTRs with CLAD and assess the impact of colonization or infection on post-CLAD survival.

METHODS

Prospectively collected Toronto Lung Transplant Program database and chart review were used for double-LTRs who were diagnosed with CLAD from January 1, 2016 to January 1, 2020 and who were free of airway fungi within 1 year prior to CLAD onset. International Society for Heart and Lung Transplantation definitions were used to define clinical syndromes. Cox-Proportional Hazards Models were used for risk-factor analysis. Survival analysis could not be completed secondary to low number of fungal events; therefore, descriptive statistics were employed for survival outcomes.

RESULTS

We found 186 LTRs diagnosed with CLAD meeting our inclusion criteria. The 1-year cumulative incidence for any fungal event was 11.8% (7.0% for infection and 4.8% for colonization). Aspergillus fumigatus was a causative pathogen in eight of 13 (61.5%) patients with infection and six of nine (66.7%) patients with colonization. No patients with fungal colonization post-CLAD developed fungal infection. Peri-CLAD diagnosis (3 months prior or 1 month after) methylprednisolone bolus (hazards ratio: 8.84, p = .001) increased the risk of fungal events. Most patients diagnosed with fungal infections (53.8%) died within 1-year of CLAD onset.

CONCLUSION

De novo IFIs and fungal colonization following CLAD onset were not common. Fungal colonization did not lead to fungal infection. Methylprednisolone bolus was a significant risk factors for post-CLAD fungal events.

Current perspective of immunomodulators for lung transplant

Lung transplantation is an effective treatment option for selected patients suffering from end-stage lung disease. More intensive immunosuppression is enforced after lung transplants owing to a greater risk of rejection than after any other solid organ transplants. The commencing of lung transplantation in the modern era was in 1983 when the Toronto Lung Transplant Group executed the first successful lung transplant. A total of 43,785 lung transplants and 1365 heart-lung transplants have been performed from 1 Jan 1988 until 31 Jan 2021. The aim of this review article is to discuss the existing immunosuppressive strategies and emerging agents to prevent acute and chronic rejection in lung transplantation.

Lung Retransplantation

Lung retransplantation remains the standard treatment of irreversible lung allograft failure. The most common indications for lung retransplantation are acute graft failure, chronic lung allograft dysfunction, and postoperative airway complications. Careful patient selection with regards to indications, anatomy, extrapulmonary organ dysfunction (specifically renal dysfunction), and immunologic consideration are of utmost importance. The conduct of the lung retransplantation operation is arduous with special considerations given to operative approach, type of surgery (single vs bilateral), use of extracorporeal circulatory support, and hematological management. Outcomes have improved significantly for most patients, nearing short and midterm outcomes of primary lung recipients in select cases.

Anesthetic considerations in lung transplantation: past, present and future

Lung transplantation is a very complex surgical procedure with many implications for the anesthetic care of these patients. Comprehensive preoperative evaluation is an important component of the transplant evaluation as it informs many of the decisions made perioperatively to manage these complex patients effectively and appropriately. These decisions may involve pre-emptive actions like pre-habilitation and nutrition optimization of these patients before they arrive for their transplant procedure. Appropriate airway and ventilation management of these patients needs to be performed in a manner that provides an optimal operating conditions and protection from ventilatory injury of these fragile post-transplant lungs. Pain management can be challenging and should be managed in a multi-modal fashion with or without the use of an epidural catheter while recognizing the risk of neuraxial technique in patients who will possibly be systemically anticoagulated. Complex monitoring is required for these patients involving both invasive and non-invasive including the use of transesophageal echocardiography (TEE) and continuous cardiac output monitoring. Management of the patient's hemodynamics can be challenging and involves managing the systemic and pulmonary vascular systems. Some patients may require extra-corporeal lung support as a planned part of the procedure or as a rescue technique and centers need to be proficient in instituting and managing this sophisticated method of hemodynamic support.

Approaching the sensitized lung patient: risk assessment for donor acceptance

The presence of HLA antibodies is widely recognized as a barrier to solid organ transplantation, and for lung transplant candidates, it has a significant negative impact on both waiting time and waiting list mortality. Although HLA antibodies have been associated with a broad spectrum of allograft damage, precise characterization of these antibodies in allosensitized candidates may enhance their accessibility to transplant. The introduction of Luminex-based single antigen bead (SAB) assays has significantly improved antibody detection sensitivity and specificity, but SAB alone is not sufficient for risk-stratification. Functional characterization of donor-specific antibodies (DSA) is paramount to increase donor accessibility for allosensitized lung candidates. We describe here our approach to evaluate sensitized lung transplant candidates. By employing state-of-the-art technologies to assess histocompatibility and determine physiological properties of circulating HLA antibodies, we can provide our Clinical Team a better risk assessment for lung transplant candidates and facilitate a "road map" to transplant. The cases presented in this paper illustrate the "individualized steps" taken to determine calculated panel reactive antibodies (cPRA), titer and complement-fixing properties of each HLA antibody present in circulation. When a donor is considered, we can better predict the risk associated with potentially crossing HLA antibodies, thereby allowing the Clinical Team to approach allosensitized lung patients with an individualized medicine approach. To facilitate safe access of sensitized lung transplant candidates to potential donors, a synergy between the histocompatibility laboratory and the Clinical Team is essential. Ultimately, donor acceptance is a decision based on several parameters, leading to a risk-stratification unique for each patient.

Postoperative Management of Lung Transplant Recipients in the Intensive Care Unit

The number of lung transplantations is progressively increasing worldwide, providing new challenges to interprofessional teams and the intensive care units. The outcome of lung transplantation recipients is critically affected by a complex interplay of particular pathophysiologic conditions and risk factors, knowledge of which is fundamental to appropriately manage these patients during the early postoperative course. As high-grade evidence-based guidelines are not available, the authors aimed to provide an updated review of the postoperative management of lung transplantation recipients in the intensive care unit, which addresses six main areas: (1) management of mechanical ventilation, (2) fluid and hemodynamic management, (3) immunosuppressive therapies, (4) prevention and management of neurologic complications, (5) antimicrobial therapy, and (6) management of nutritional support and abdominal complications. The integrated care provided by a dedicated multidisciplinary team is key to optimize the complex postoperative management of lung transplantation recipients in the intensive care unit.

Consensus document for the selection of lung transplant candidates: An update from the International Society for Heart and Lung Transplantation

Tens of thousands of patients with advanced lung diseases may be eligible to be considered as potential candidates for lung transplant around the world each year. The timing of referral, evaluation, determination of candidacy, and listing of candidates continues to pose challenges and even ethical dilemmas. To address these challenges, the International Society for Heart and Lung Transplantation appointed an international group of members to review the literature, to consider recent advances in the management of advanced lung diseases, and to update prior consensus documents on the selection of lung transplant candidates. The purpose of this updated consensus document is to assist providers throughout the world who are caring for patients with pulmonary disease to identify potential candidates for lung transplant, to optimize the timing of the referral of these patients to lung transplant centers, and to provide transplant centers with a framework for evaluating and selecting candidates. In addition to addressing general considerations and providing disease specific recommendations for referral and listing, this updated consensus document includes an ethical framework, a recognition of the variability in acceptance of risk between transplant centers, and establishes a system to account for how a combination of risk factors may be taken into consideration in candidate selection for lung transplantation.

Long-term outcomes of sensitized lung transplant recipients after peri-operative desensitization

The Toronto Lung Transplant Program has been using a peri-operative desensitization regimen of plasma exchange, intravenous immune globulin, and antithymocyte globulin in order to accept donor-specific antibody (DSA)-positive lung transplants safely since 2008. There are no long-term data on the impact of this practice on allograft survival or the development of chronic lung allograft dysfunction (CLAD). We extended our prior study to include long-term follow-up of 340 patients who received lung transplants between January 1, 2008 and December 31, 2011. We compared allograft survival and CLAD-free survival among patients in three cohorts: DSA-positive, panel reactive antibody (PRA)-positive/DSA-negative, and unsensitized at the time of transplant. The median follow-up time in this extension study was 6.7 years. Among DSA-positive, PRA-positive/DSA-negative, and unsensitized patients, the median allograft survival was 8.4, 7.9, and 5.8 years, respectively (p = .5908), and the median CLAD-free survival was 6.8, 7.3, and 5.7 years, respectively (p = .5448). This follow-up study confirms that long-term allograft survival and CLAD-free survival of patients who undergo DSA-positive lung transplants with the use of our protocol do not differ from other lung transplant recipients. Use of protocols such as ours, therefore, may improve access to transplant for sensitized candidates.

Lung Transplantation Outcomes after Crossing Low-Level Donor Specific Antibodies Without Planned Augmented Immunosuppression

It is unknown whether some donor specific antibodies (DSA) can be crossed at the time of lung transplant without desensitization or augmented induction immunosuppression. This study assessed whether crossing low-level pre-transplant DSA (defined as mean fluorescence intensity (MFI) 1000-6000) without augmented immunosuppression is associated with worse retransplant-free or chronic lung allograft dysfunction (CLAD)-free survival. Of the 458 included recipients, low-level pre-transplant DSA was crossed in 39 (8.6%) patients. The median follow-up time was 2.2 years. There were 15 (38.5%) patients with Class I DSA and 24 (61.5%) with Class II DSA. There was no difference in adjusted overall retransplant-free survival between recipients where pre-transplant DSA was and was not crossed (HR: 0.98 (95% CI = 0.49-1.99), p = 0.96). There was also no difference in CLAD-free survival (HR: 0.71 (95% CI = 0.38-1.33), p = 0.28). There was no difference in Grade 3 PGD at 72 hours (OR: 1.13 (95% CI = 0.52-2.48), p = 0.75) or definite or probable AMR (HR: 2.22 (95% CI = 0.64-7.61), p = 0.21). Lung transplantation in the presence of low-level DSA without planned augmented immunosuppression is not associated with worse overall or CLAD-free survival among recipients with intermediate-term follow-up. This article is protected by copyright. All rights reserved.

Treatment outcomes of nontuberculous mycobacterial pulmonary disease in lung transplant recipients

BACKGROUND

Lung transplant (LTX) recipients are at risk miscellaneous infections, among whom the clinical significance of nontuberculous mycobacteria (NTM) is increasingly recognized. Despite anti-mycobacterial therapy becoming standardized worldwide, there is a lack of data on treatment outcomes in LTX recipients who develop NTM-pulmonary disease (PD). We aimed to review the treatment outcomes of NTM-PD among LTX recipients in our center.

METHODS

Patients who underwent LTX from January 2013 to December 2014 were consecutively enrolled in the retrospective cohort, with follow-up of data retrieved to December 2017. Clinical and radiological improvement and culture conversion after anti-mycobacterial therapy were reviewed in those who developed post-transplant NTM-PD.

RESULTS

Sixteen of 230 LTX recipients developed post-transplant NTM-PD. Ten of 16 patients with post-transplant NTM-PD were treated with macrolide-containing anti-mycobacterial therapy, leading to clinical improvement in 5/10 (50%), radiological improvement in 5/10 (50%) and culture conversion in 6/10 (60%) patients.

CONCLUSION

Anti-mycobacterial therapy may relieve pulmonary symptoms and reduce microbial load among individuals with post-transplant NTM-PD.

Diffusing Capacity for Carbon Monoxide (DLCO): Association with long-term outcomes after Lung Transplantation in a 20-year longitudinal study

RATIONALE

The diffusing capacity for carbon monoxide corrected for haemoglobin (DLCO_cor), measures gas movement across the alveolar-capillary interface. We hypothesised that DLCO_cor is a sensitive measure of injurious allograft processes disrupting this interface.

OBJECTIVES

To determine the prognostic significance of the DLCO_cor trajectory on chronic lung allograft dysfunction (CLAD) and survival.

METHODS

A retrospective analysis was conducted of all bilateral lung transplant recipients at a single centre, between Jan-1998 and Jan-2018, with ≥1 DLCO_cor measurements. Low baseline DLCO_cor was defined as the failure to achieve a DLCO_cor >75% predicted. Drops in DLCO_cor were defined as >15% below recent baseline.

RESULTS

1259/1492 lung transplant recipients were included. The median time to peak DLCO_cor was 354 (range 181-737) days and the mean %-predicted DLCO_cor was 80.2% (sd 21.2). Multivariable analysis demonstrated that low baseline DLCO_cor was significantly associated with death (HR 1.68, 95% CI 1.27-2.20, p<0.001). Low baseline DLCO_cor was not independently associated with CLAD after adjustment for low baseline FEV₁ or FVC. Any DLCO_cor declines ≥15% were significantly associated with death, independent of concurrent spirometric decline. Lower %-predicted DLCO_cor values at CLAD onset were associated with shorter post-CLAD survival (HR 0.75 per 10%-unit change, p<0.01).

CONCLUSION

Low baseline DLCO_cor and post-transplant declines in DLCO_cor were significantly associated with survival, independent of spirometric measurements. We propose that DLCO_cor testing may allow identification of a sub-phenotype of baseline and chronic allograft dysfunction not captured by spirometry. There may be benefit in routine monitoring of DLCO_cor after lung transplantation to identify patients at risk of poor outcomes.

Emerging New Approaches in Desensitization: Targeted Therapies for HLA Sensitization

There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or de novo donor-specific HLA antibodies (DSA). The risk of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively, de novo DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response.

Bronchoalveolar lavage cytokine-based risk stratification of minimal acute rejection in clinically stable lung transplant recipients

BACKGROUND

Acute cellular rejection (ACR) remains the most significant risk factor for chronic lung allograft dysfunction (CLAD). While clinically significant or higher-grade (≥A2) ACR is generally treated with augmented immunosuppression (IS), the management of clinically stable grade A1 ACR remains controversial. At our center, patients with clinically stable grade A1 ACR are routinely not treated with augmented IS. While the overall outcomes in this group of patients at our center are equivalent to patients with stable A0 pathology, CLAD and death rates remain overall high. We hypothesized that a distinct cytokine signature at the time of early minimal rejection state would be associated with worse outcomes. Specifically, we aimed to determine whether bronchoalveolar lavage (BAL) biomarkers at the time of first clinically stable grade A1 ACR (CSA1R) are predictive of subsequent CLAD or death.

METHODS

Among all adult, bilateral, first lung transplants, performed 2010-2016, transbronchial biopsies obtained within the first-year post-transplant were categorized as clinically stable or unstable based on the presence or absence of ≥10% concurrent drop in forced expiratory volume in 1 second (FEV₁). We assessed BAL samples obtained at the time of CSA1R episodes, which were not preceded by another ACR (i.e., first episodes). Twenty-one proteins previously associated with ACR or CLAD were measured in the BAL using a multiplex bead assay. Association between protein levels and subsequent CLAD or death was assessed using Cox Proportional Hazards models, adjusted for relevant peri-transplant clinical covariates.

RESULTS

We identified 75 patients with first CSA1R occurring at a median time of 98 days (range 48.5-197) post-transplant. Median time from transplant to CLAD or death was 1247 (756.5-1921.5) and 1641 days (1024.5-2326.5), respectively. In multivariable models, levels of MCP1/CCL2, S100A8, IL10, TNF-receptor 1, and pentraxin 3 (PTX3) were associated with both CLAD development and death (p < 0.05 for all). PTX3 remained significantly associated with both CLAD and death after adjusting for multiple comparisons.

CONCLUSION

Our data indicate that a focused BAL protein signature, with PTX3 having the strongest association, may be useful in determining a subset of CSA1R patients at increased risk and may benefit from a more aggressive management strategy.

B cells in transplant tolerance and rejection: friends or foes?

Our understanding of the role of B cells in organ transplantation remains incomplete and continues to grow. The majority of research has focused on the detrimental role of antibodies that drive the development of pathogenesis of the transplanted organ. However, it has been shown that not all donor-specific antibodies are harmful and in some circumstances can even promote tolerance through the mechanism of accommodation. Furthermore, B cells can have effects on transplanted organs through their interaction with T cells, namely antigen presentation, cytokine production, and costimulation. More recently, the role and importance of Bregs was introduced to the field of transplantation. Due to this functional and ontogenetic heterogeneity, targeting B cells in transplantation may bring undesired immunologic side effects including increased rejection. Therefore, the selective control of B cells that contribute to the humoral response against donor antigens will continue to be an important and challenging area of research and potentially lead to improved long-term transplant outcomes.

Lung Transplantation and the Era of the Sensitized Patient

Long term outcomes in lung transplant are limited by the development of chronic lung allograft dysfunction (CLAD). Within the past several decades, antibody-mediated rejection (AMR) has been recognized as a risk factor for CLAD. The presence of HLA antibodies in lung transplant candidates, "sensitized patients" may predispose patients to AMR, CLAD, and higher mortality after transplant. This review will discuss issues surrounding the sensitized patient, including mechanisms of sensitization, implications within lung transplant, and management strategies.

Antibody-Mediated Rejection and Lung Transplantation

Antibody-mediated rejection (AMR) is now a widely recognized form of lung allograft rejection, with mounting evidence for AMR as an important risk factor for the development of chronic lung allograft dysfunction and markedly decreased long-term survival. Despite the recent development of the consensus diagnostic criteria, it remains a challenging diagnosis of exclusion. Furthermore, even after diagnosis, treatment directed at pulmonary AMR has been nearly exclusively derived from practices with other solid-organ transplants and other areas of medicine, such that there is a significant lack of data regarding the efficacy for these in pulmonary AMR. Lastly, outcomes after AMR remain quite poor despite aggressive treatment. In this review, we revisit the history of AMR in lung transplantation, describe our current understanding of its pathophysiology, discuss the use and limitations of the consensus diagnostic criteria, review current treatment strategies, and summarize long-term outcomes. We conclude with a synopsis of our most pressing gaps in knowledge, introduce recommendations for future directions, and highlight promising areas of active research.