Infectious Complications in Lung Transplant Recipients

Unveiling the potential of lung transplantation for situs inversus

INTRODUCTION

Situs inversus is a rare congenital condition where the organs in the chest and abdomen are reversed, thus complicating surgeries such as lung transplantation. Kartagener syndrome (KS), associated with situs inversus, includes chronic sinusitis and bronchiectasis, which can progress to end-stage lung disease requiring transplantation. This review discusses the unique surgical considerations, technical challenges, and outcomes of lung transplantation in patients with situs inversus, particularly KS.

AREAS COVERED

The review highlights anatomical and physiological challenges in lung transplantation due to reversed organ positioning, requiring customized surgical approaches and intraoperative modifications. Preoperative imaging, anesthesia adjustments, and tailored surgical techniques are crucial for successful transplantation. Postoperative care focuses on managing complications such as primary graft dysfunction, infections, and anastomotic issues. Literature on survival rates, chronic lung allograft dysfunction, and quality of life is analyzed, indicating outcomes comparable to other lung transplant recipients.

EXPERT OPINION

Despite significant challenges, lung transplantation in patients with situs inversus and KS is feasible with outcomes similar to traditional cases. Advances in imaging, surgical planning, and minimally invasive techniques offer promise for improved outcomes. Ongoing research, collaboration, and ethical considerations are essential to optimizing care and expand treatment possibilities for this high-risk patient population.

Severe SARS-CoV-2 infection is associated with increased risk of De novo HLA antibody production in lung transplant recipients: Single-center study

THE PURPOSE

The COVID-19 pandemic has led to significant morbidity and mortality in lung transplant recipients (LTR). Respiratory viral infections may be associated with de-novo HLA donor-specific antibody (DSA) production and impact lung transplant outcomes. Since one of the immunomodulation strategies post-SARS-CoV-2 infection in LTR include decreasing or holding anti-metabolites, concerns have been raised for higher incidence of de-novo DSA production in LTR.

METHODS

We performed a retrospective chart review of 63 consecutive LTR diagnosed with COVID-19 to investigate this concern. COVID-19 disease severity was divided into 3 groups: mild, moderate, and severe. Mild disease was defined as patients with COVID-19 diagnosis who were stable enough to be treated as out-patients. Moderate disease was defined as patients who required admission to the hospital and were on less than 10 l of oxygen at rest. Severe disease was identified as patients who required hospitalization and were on more than 10 l of oxygen with or without mechanical ventilation or extra corporal membrane oxygenation (ECMO). Groups were compared using the Kruskal-Wallis test. A total of 11, 43, and 9 LTR were diagnosed with mild, moderate, and severe COVID-19 respectively.

RESULTS

We observed no significant differences in the CPRA pre-COVID-19 compared to 1 and 6 months post-COVID-19 diagnosis in 6/11 (54.5 %), 18/43 (41.8 %), and 6/9 (66.9 %) LTR with mild (p = 0.66), moderate (p = 0.74), and severe (p = 0.22) COVID-19 respectively. HLA class I and II DSA were detected pre-COVID-19 diagnosis and persisted with no significant differences in the median MFI levels at 1 and 6 months post-COVID-19 diagnosis in 2/11 (p = 0.93), 7/43 (p = 0.71), and 0/9 LTR with mild, moderate, and severe COVID-19 respectively. De-novo HLA DSA were detected within 6 months post-COVID-19 diagnosis in 0/11 (0 %), 1/43 (2.3 %), and 3/9 (33.3 %%) LTR with mild, moderate, and severe COVID-19 respectively (p = 0.001).

CONCLUSION

Severe COVID-19 may be associated with increased risk of de novo HLA DSA production resulting in allograft dysfunction.

Pneumonia in Transplant Recipients: A Comprehensive Review of Diagnosis and Management

Transplant recipients have an increased risk of complications, including graft dysfunction and infections, which can be life-threatening if not recognized early. Pneumonia ranks as one of the most frequent complications in both solid organ and hematopoietic stem cell transplants. Clinical symptoms manifest late during infections in immunocompromised patients. An aggressive approach centered on early confirmatory diagnosis and a low threshold for empiric therapy is often the most effective strategy. The isolation of a pathogen in an upper airway sample does not necessarily mean the same organism is responsible for pneumonia. Viruses such as CMV (cytomegalovirus virus) may function as co-pathogens for opportunistic infections in transplant recipients in addition to causing their own primary infectious syndrome. Furthermore, some viruses exhibit immunomodulatory effects that can affect the graft function. Given the exhaustive list of causative pathogens responsible for pneumonia, the best approach to the diagnosis is to have a conceptual framework that includes a detailed history, such as the type of transplant, degree of immunosuppression, antimicrobial prophylaxis, risk factors, time of presentation since transplantation and the radiographic pattern on the CT chest (computer tomography of the chest). Management depends predominantly on the degree of antimicrobial resistance, drug-to-drug interaction, and adjustments to the immunosuppression.

Immunopathology of lung transplantation: from infection to rejection and vice versa

Lung transplantation offers a lifesaving option for patients with end-stage lung disease, but it is marred by a high risk of post-transplant infections, particularly involving multidrug-resistant bacteria, Cytomegalovirus, and fungal pathogens. This elevated infection rate, the highest among solid organ transplants, poses a significant challenge for clinicians, particularly within the first year post-transplantation, where infections are the leading cause of mortality. The direct exposure of lung allografts to the external environment exacerbates this vulnerability leading to constant immune stimulation and consequently to an elevated risk of triggering alloimmune responses to the lung allograft. The necessity of prolonged immunosuppression to prevent allograft rejection further complicates patient management by increasing susceptibility to infections and neoplasms, and complicating the differentiation between rejection and infection, which require diametrically opposed management strategies. This review explores the intricate balance between preventing allograft rejection and managing the heightened infection risk in lung transplant recipients.

Changes in post-transplant serum testosterone levels in men undergoing lung transplantation: a pilot study using the TriNetX Research Network

Hypogonadism is understudied in men requiring solid organ transplants, particularly among lung transplant recipients. Improvement in serum testosterone levels has been reported in kidney and liver transplantation. Using the TriNetX Research Network, we performed a retrospective cohort study to evaluate the incidence of peri-transplant hypogonadism and the natural course of serum testosterone following successful lung transplantation. Men aged ≥ 18 with a lung transplant and total testosterone drawn within one year pre- and post-transplant were included. Men with receipt of testosterone therapy were excluded. A low testosterone (<300 ng/dL) and normal testosterone (≥300 ng/dL) cohort was created before employing descriptive and analytic statistics to investigate the incidence of peri-transplant hypogonadism and the change in serum testosterone levels following lung transplantation. In our entire cohort, lung transplantation was not associated with a significant increase in post-transplant serum testosterone (329.86 ± 162.56 ng/dL pre-transplant and 355.13 ± 216.11 ng/dL post-transplant, p = 0.483). The number of men with low testosterone decreased by 9.8% following lung transplantation but was not significant, p = 0.404. In this pilot study, no significant change in the number of hypogonadal men nor serum testosterone levels was observed among men undergoing lung transplantation.

Pulmonary transplant complications: a radiologic review

Lung transplantation has become the definitive treatment for end stage respiratory disease. Numbers and survival rates have increased over the past decade, with transplant recipients living longer and with greater comorbidities, resulting in greater complexity of care. Common and uncommon complications that occur in the immediate, early, intermediate, and late periods can have significant impact on the course of the transplant. Fortunately, advancements in surgery, medical care, and imaging as well as other diagnostics work to prevent, identify, and manage complications that would otherwise have a negative impact on survivability. This review will focus on contextualizing complications both categorically and chronologically, with highlights of specific imaging and clinical features in order to inform both radiologists and clinicians involved in post-transplant care.

Alterations of lung microbiota in lung transplant recipients with pneumocystis jirovecii pneumonia

BACKGROUND

Increasing evidence revealed that lung microbiota dysbiosis was associated with pulmonary infection in lung transplant recipients (LTRs). Pneumocystis jirovecii (P. jirovecii) is an opportunistic fungal pathogen that frequently causes lethal pneumonia in LTRs. However, the lung microbiota in LTRs with P. jirovecii pneumonia (PJP) remains unknow.

METHODS

In this prospective observational study, we performed metagenomic next-generation sequencing (mNGS) on 72 bronchoalveolar lavage fluid (BALF) samples from 61 LTRs (20 with PJP, 22 with PJC, 19 time-matched stable LTRs, and 11 from LTRs after PJP recovery). We compared the lung microbiota composition of LTRs with and without P. jirovecii, and analyzed the related clinical variables.

RESULTS

BALFs collected at the episode of PJP showed a more discrete distribution with a lower species diversity, and microbiota composition differed significantly compared to P. jirovecii colonization (PJC) and control group. Human gammaherpesvirus 4, Phreatobacter oligotrophus, and Pseudomonas balearica were the differential microbiota species between the PJP and the other two groups. The network analysis revealed that most species had a positive correlation, while P. jirovecii was correlated negatively with 10 species including Acinetobacter venetianus, Pseudomonas guariconensis, Paracandidimonas soli, Acinetobacter colistiniresistens, and Castellaniella defragrans, which were enriched in the control group. The microbiota composition and diversity of BALF after PJP recovery were also different from the PJP and control groups, while the main components of the PJP recovery similar to control group. Clinical variables including age, creatinine, total protein, albumin, IgG, neutrophil, lymphocyte, CD3+CD45+, CD3+CD4+ and CD3+CD8+ T cells were deeply implicated in the alterations of lung microbiota in LTRs.

CONCLUSIONS

This study suggests that LTRs with PJP had altered lung microbiota compared to PJC, control, and after recovery groups. Furthermore, lung microbiota is related to age, renal function, nutritional and immune status in LTRs.

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

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

The effect of infectious diseases on lung transplantation in Japan

Lung transplantation in Japan is an increasingly accessible treatment option for end-stage lung disease; however, the lack of donor organs is a persisting challenge. Five- and 10-year survival rates of lung transplant recipients in Japan are comparable, if not superior, to international standards. The outcomes of lung transplantation in Japan are likely affected by multiple factors. Infectious disease complications are a significant burden to transplant recipients and account for approximately 30% of recipient mortality in Japan, presenting a major challenge in peri-transplant management. Herein, we explore the current status of infectious disease epidemiology, available evidence surrounding infectious diseases in lung transplantation, and potentially influential factors pertinent to lung transplantation outcomes in Japan. Although infection remains the major cause of morbidity and mortality associated with lung transplantation in Japan, there is limited data and evidence. Despite some uncertainties, publicly available data suggests a low rate of antimicrobial resistance in Gram-negative bacteria and a distinct set of endemic pathogens that recipients may encounter. As a countermeasure against the burden of infectious diseases, 8 out of 10 transplant centers in Japan have a dedicated infectious diseases department. Despite these efforts, specific surveillance, prevention, and management are indispensable to improving post-transplantation infectious disease management. We accordingly lay out potential areas for improving infectious disease-related outcomes among lung transplant recipients in Japan.

Novel dimensionality reduction method, Taelcore, enhances lung transplantation risk prediction

In this work, we present a new approach to predict the risk of acute cellular rejection (ACR) after lung transplantation by using machine learning algorithms, such as Multilayer Perceptron (MLP) or Autoencoder (AE), and combining them with topological data analysis (TDA) tools. Our proposed method, named topological autoencoder with best linear combination for optimal reduction of embeddings (Taelcore), effectively reduces the dimensionality of high-dimensional datasets and yields better results compared to other models. We validate the effectiveness of Taelcore in reducing the prediction error rate on four datasets. Furthermore, we demonstrate that Taelcore's topological improvements have a positive effect on the majority of the machine learning algorithms used. By providing a new way to diagnose patients and detect complications early, this work contributes to improved clinical outcomes in lung transplantation.

Inhibition of Prostaglandin-Degrading Enzyme 15-PGDH Mitigates Acute Murine Lung Allograft Rejection

PURPOSE

Acute rejection is a frequent complication among lung transplant recipients and poses substantial therapeutic challenges. 15-hydroxyprostaglandin dehydrogenase (15-PGDH), an enzyme responsible for the inactivation of prostaglandin E2 (PGE2), has recently been implicated in inflammatory lung diseases. However, the role of 15-PGDH in lung transplantation rejection remains elusive. The present study was undertaken to examine the expression of 15-PGDH in rejected lung allografts and whether inhibition of 15-PGDH ameliorates acute lung allograft rejection.

METHODS

Orthotopic mouse lung transplantations were performed between donor and recipient mice of the same strain or allogeneic mismatched pairs. The expression of 15-PGDH in mouse lung grafts was measured. The efficacy of a selective 15-PGDH inhibitor (SW033291) in ameliorating acute rejection was assessed through histopathological examination, micro-CT imaging, and pulmonary function tests. Additionally, the mechanism underlying the effects of SW033291 treatment was explored using CD8+ T cells isolated from mouse lung allografts.

RESULTS

Increased 15-PGDH expression was observed in rejected allografts and allogeneic CD8+ T cells. Treatment with SW033291 led to an accumulation of PGE2, modulation of CD8+ T-cell responses and mitochondrial activity, and improved allograft function and survival.

CONCLUSION

Our study provides new insights into the role of 15-PGDH in acute lung rejection and highlights the therapeutic potential of inhibiting 15-PGDH for enhancing graft survival. The accumulation of PGE2 and modulation of CD8+ T-cell responses represent potential mechanisms underlying the benefits of 15-PGDH inhibition in this model. Our findings provide impetus for further exploring 15-PGDH as a target for improving lung transplantation outcomes.

Pediatric Lung Transplant Outcomes Based on Immunosuppressive Regimen at Discharge: Retrospective Cohort Study Using Real-World Evidence From the US Scientific Registry of Transplant Recipients

BACKGROUND

This retrospective analysis of the US Scientific Registry of Transplant Recipients was undertaken to obtain real-world evidence concerning the efficacy and safety of tacrolimus-based immunosuppression in pediatric lung transplant recipients to support a supplemental New Drug Application.

METHODS

Overall, 725 pediatric recipients of a primary deceased-donor lung transplant between January 1, 1999, and December 31, 2017, were followed for up to 3 years post-transplant based on an immunosuppressive regimen at hospital discharge: immediate-release tacrolimus (TAC)+mycophenolate mofetil (MMF), TAC+azathioprine (AZA), cyclosporine (CsA)+MMF, or CsA+AZA. The primary outcome was the composite endpoint of graft failure or death (all-cause) at 1 year post-transplant, calculated by Kaplan-Meier analysis.

RESULTS

The use of TAC+MMF increased over time. During 2010 to 2017, 91.7% of pediatric lung transplant recipients were receiving TAC+MMF at the time of discharge. The proportion of recipients continuing their discharge regimen at 1 year post-transplant was 83.7% with TAC+MMF and 40.4% to 59.7% with the other regimens. Cumulative incidence of the composite endpoint of graft failure or death at 1 year post-transplant was 7.7% with TAC+MMF, 13.9% with TAC+AZA, 8.9% with CsA+MMF, and 9.1% with CsA+AZA. There was no significant difference in the risk of graft failure or death at 1 year post-transplant between groups from 1999 to 2005 (the only era when adequate numbers on each regimen allowed statistical comparison). No increase in hospitalization for infection or malignancy was seen with TAC+MMF.

CONCLUSION

The real-world evidence from the US database of transplant recipients supported the Food and Drug Administration's approval of tacrolimus-based maintenance immunosuppression in pediatric lung transplant recipients.

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

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

Population pharmacokinetic analysis, renal safety, and dosing optimization of polymyxin B in lung transplant recipients with pneumonia: A prospective study

Objectives: This study aims to characterize the population pharmacokinetics of polymyxin B in lung transplant recipients and optimize its dosage regimens.

Patients and methods: This prospective study involved carbapenem-resistant organisms-infected patients treated with polymyxin B. The population pharmacokinetic model was developed using the NONMEM program. The clinical outcomes including clinical treatment efficacy, microbiological efficacy, nephrotoxicity, and hyperpigmentation were assessed. Monte Carlo simulation was performed to calculate the probability of target attainment in patients with normal or decreased renal function.

Results: A total of 34 hospitalized adult patients were included. 29 (85.29%) patients were considered of clinical cure or improvement; 14 (41.18%) patients had successful bacteria elimination at the end of the treatment. Meanwhile, 5 (14.71%) patients developed polymyxin B-induced nephrotoxicity; 19 (55.88%) patients developed skin hyperpigmentation. A total of 164 concentrations with a range of 0.56–11.66 mg/L were obtained for pharmacokinetic modeling. The pharmacokinetic characteristic of polymyxin B was well described by a 1-compartment model with linear elimination, and only creatinine clearance was identified as a covariate on the clearance of polymyxin B. Monte Carlo simulations indicated an adjusted dosage regimen might be needed in patients with renal insufficiency and the currently recommended dose regimens by the label sheet of polymyxin B may likely generate a subtherapeutic exposure for MIC = 2 mg/L.

Conclusion: Renal function has a significant effect on the clearance of polymyxin B in lung transplant recipients, and an adjustment of dosage was needed in patients with renal impairments.

Lung Transplant Outcomes in Adults in the United States: Retrospective Cohort Study Using Real-world Evidence from the SRTR

BACKGROUND

The Scientific Registry of Transplant Recipients was retrospectively analyzed to provide real-world evidence of the efficacy and safety of tacrolimus-based immunosuppressive regimens in adult lung transplant recipients in the United States.

METHODS

Adult recipients (N = 25 355; ≥18 y) of a primary deceased-donor lung transplant between January 1, 1999, and December 31, 2017, were followed for 3 y posttransplant based on immunosuppressive regimen at discharge: immediate-release tacrolimus (TAC) + mycophenolate mofetil (MMF), TAC + azathioprine (AZA), cyclosporine (CsA) + MMF, or CsA + AZA. The primary outcome was the composite endpoint of graft failure or death (all-cause) at 1 y posttransplant (calculated via a modified Kaplan-Meier method).

RESULTS

Discharge immunosuppressive regimens in lung transplant recipients changed over time, with a substantial increase in the use of TAC + MMF. TAC + MMF was the most common immunosuppressive regimen (received by 61.0% of individuals at discharge). The cumulative incidence of graft failure or death at 1 y posttransplant in adult lung transplant patients receiving TAC + MMF was 8.6% (95% confidence interval 8.1-9.1). Risk of graft failure or death was significantly higher in adults receiving CsA + MMF or CsA + AZA compared with TAC + MMF, with no significant difference seen between TAC + MMF and TAC + AZA. TAC + MMF had the highest continued use at 1 y posttransplant (72.0% versus 35.4%-51.5% for the other regimens). There was no increase in the rate of infection or malignancy in the TAC + MMF group.

CONCLUSIONS

Real-world evidence from the most comprehensive database of transplant recipients in the United States supports the use of TAC in combination with MMF or AZA as maintenance immunosuppression in adult lung transplant recipients.

Ganciclovir Pharmacokinetics and Individualized Dosing Based on Covariate in Lung Transplant Recipients

The aim of this prospective study was to evaluate the pharmacokinetics of ganciclovir in lung transplant recipients, to explore its covariates, and to propose an individualized dosing regimen. Ganciclovir was administered according to the protocol in a standardized intravenous dose of 5 mg/kg twice daily. Serum ganciclovir concentrations were monitored as a trough and at 3 and 5 h after dosing. Individual ganciclovir pharmacokinetic parameters were calculated in a two-compartmental pharmacokinetic model, while regression models were used to explore the covariates. Optimal loading and maintenance doses were calculated for each patient. In lung transplant recipients (n = 40), the median (IQR) ganciclovir total volume of distribution and clearance values were 0.65 (0.52–0.73) L/kg and 0.088 (0.059–0.118) L/h/kg, respectively. We observed medium-to-high inter-individual but negligible intra-individual variability in ganciclovir pharmacokinetics. The volume of distribution of ganciclovir was best predicted by height, while clearance was predicted by glomerular filtration rate. Bodyweight-normalized clearance was significantly higher in patients with cystic fibrosis, while distribution half-life was reduced in this subgroup. On the basis of the observed relationships, practical nomograms for individualized ganciclovir dosing were proposed. The dosing of ganciclovir in patients with cystic fibrosis requires special caution, as their daily maintenance dose should be increased by approximately 50%.

High-throughput next-generation sequencing for identifying pathogens during early-stage post-lung transplantation

BACKGROUND

High-throughput next-generation sequencing (HT-NGS) has the potential to detect a large variety of pathogens; however, the application of HT-NGS in lung transplant (LTx) recipients remains limited. We aimed to evaluate the value of HT-NGS for pathogen detection and diagnosis of pulmonary infection during early-stage post-lung transplantation.

METHODS

In this retrospective study, we enrolled 51 LTx recipients who underwent lung transplantation between January 2020 and December 2020. Bronchoalveolar lavage fluid (BALF) samples were collected for the detection of pathogens using both HT-NGS and conventional microbiological testing. The detection of pathogens and diagnostic performance of HT-NGS were compared with that of conventional methods.

RESULTS

HT-NGS provided a higher positive rate of pathogen detection than conventional microbiological testing (88.24% vs. 76.47%). The most common bacteria detected via HT-NGS during early-stage post-lung transplantation were Enterococcus, Staphylococcus, Pseudomonas and Klebsiella, while all fungi were Candida and all viruses were Herpesvirus. Uncommon pathogens, including Strongyloides, Legionella, and Mycobacterium abscesses were identified by HT-NGS. The sensitivity of HT-NGS for diagnosing pulmonary infection was significantly higher than that of conventional microbiological testing (97.14% vs. 68.57%; P < 0.001). For three LTx recipients, treatment regimens were adjusted according to the results of HT-NGS, leading to a complete recovery.

CONCLUSION

HT-NGS is a highly sensitive technique for pathogen detection, which may provide diagnostic advantages, especially in LTx recipients, contributing to the optimization of treatment regimens against pulmonary infection during early-stage post-lung transplantation.