Lung donation and SARS-CoV-2 transmission: Missed detection versus missed opportunity?

The value of point-of-care tests for the detection of SARS-CoV-2 RNA or antigen in bronchoalveolar lavage fluid

BACKGROUND

Transmission of SARS-CoV-2 from donor to recipient is a clinically relevant risk for developing severe COVID-19 after lung transplantation (LTx). This risk of iatrogenic transmission can be reduced by timely detection of viral RNA or antigen in samples of bronchoalveolar lavage (BAL) fluid obtained at the time of lung procurement. We aimed to retrospectively evaluate the detection of SARS-CoV-2 RNA or antigen in BAL fluid samples using three point-of-care tests (POCTs).

METHODS

BAL fluid samples came from patients hospitalized in an intensive care unit during the COVID-19 pandemic. These pandemic samples were scored as positive or negative for SARS-CoV-2 by a RT-qPCR comparator assay for orf1ab. Three commercially available POCTs were then evaluated: cobas SARS-CoV-2 & Influenza A/B assay with the cobas Liat RT-qPCR system (Roche Diagnostics), ID NOW COVID-19 and COVID-19 2.0 (Abbott), and SARS-CoV-2 Rapid Antigen Test (RAT) (Roche Diagnostics). Samples from the pre-pandemic era served as negative controls.

RESULTS

We analyzed a total of 98 BAL fluid samples, each from a different patient: 58 positive pandemic samples (orf1ab Ct<38), 20 putatively negative pandemic samples (orf1ab Ct≥38), and 20 pre-pandemic samples. Univariate logistic regression shows that the probability of detection was highest for cobas Liat, followed by ID NOW, and then RAT. Of clinical relevance, cobas Liat detected SARS-CoV-2 RNA in 30 of the 31 positive pandemic samples that were collected within 10 days after RT-qPCR diagnosis of SARS-CoV-2 infection. None of the 20 pre-pandemic samples had a false-positive result for any POCT.

CONCLUSIONS

POCTs enable the detection of SARS-CoV-2 RNA or antigen in BAL fluid samples and may provide additional information to decide if donor lungs are suitable for transplantation. Detection of respiratory pathogens with POCTs at the time of donor lung procurement is a potential strategy to increase safety in LTx by preventing iatrogenic transmission and severe postoperative infections.

Visualising SARS-CoV-2 infection of the lung in deceased COVID-19 patients

BACKGROUND

SARS-CoV-2 is a single-stranded positive-sense RNA virus. Several negative-sense SARS-CoV-2 RNA species, both full-length genomic and subgenomic, are produced transiently during viral replication. Methodologies for rigorously characterising cell tropism and visualising ongoing viral replication at single-cell resolution in histological sections are needed to assess the virological and pathological phenotypes of future SARS-CoV-2 variants. We aimed to provide a robust methodology for examining the human lung, the major target organ of this RNA virus.

METHODS

A prospective cohort study took place at the University Hospitals Leuven in Leuven, Belgium. Lung samples were procured postmortem from 22 patients who died from or with COVID-19. Tissue sections were fluorescently stained with the ultrasensitive single-molecule RNA in situ hybridisation platform of RNAscope combined with immunohistochemistry followed by confocal imaging.

FINDINGS

We visualised perinuclear RNAscope signal for negative-sense SARS-CoV-2 RNA species in ciliated cells of the bronchiolar epithelium of a patient who died with COVID-19 in the hyperacute phase of the infection, and in ciliated cells of a primary culture of human airway epithelium that had been infected experimentally with SARS-CoV-2. In patients who died between 5 and 13 days after diagnosis of the infection, we detected RNAscope signal for positive-sense but not for negative-sense SARS-CoV-2 RNA species in pneumocytes, macrophages, and among debris in the alveoli. SARS-CoV-2 RNA levels decreased after a disease course of 2-3 weeks, concomitant with a histopathological change from exudative to fibroproliferative diffuse alveolar damage. Taken together, our confocal images illustrate the complexities stemming from traditional approaches in the literature to characterise cell tropism and visualise ongoing viral replication solely by the surrogate parameters of nucleocapsid-immunoreactive signal or in situ hybridisation for positive-sense SARS-CoV-2 RNA species.

INTERPRETATION

Confocal imaging of human lung sections stained fluorescently with commercially available RNAscope probes for negative-sense SARS-CoV-2 RNA species enables the visualisation of viral replication at single-cell resolution during the acute phase of the infection in COVID-19. This methodology will be valuable for research on future SARS-CoV-2 variants and other respiratory viruses.

FUNDING

Max Planck Society, Coronafonds UZ/KU Leuven, European Society for Organ Transplantation.

Exploring predisposing factors and pathogenesis contributing to injuries of donor lungs

INTRODUCTION

Lung transplantation (LTx) remains the only therapeutic strategy for patients with incurable lung diseases. However, its use has been severely limited by the narrow donor pool and potential concerns of inferior quality of donor lungs, which are more susceptible to external influence than other transplant organs. Multiple insults, including various causes of death and a series of perimortem events, may act together on donor lungs and eventually culminate in primary graft dysfunction (PGD) after transplantation as well as other poor short-term outcomes.

AREAS COVERED

This review focuses on the predisposing factors contributing to injuries to the donor lungs, specifically focusing on the pathogenesis of these injuries and their impact on post-transplant outcomes. Additionally, various maneuvers to mitigate donor lung injuries have been proposed.

EXPERT OPINION

The selection criteria for eligible donors vary and may be poor discriminators of lung injury. Not all transplanted lungs are in ideal condition. With the rapidly increasing waiting list for LTx, the trend of using marginal donors has become more apparent, underscoring the need to gain a deeper understanding of donor lung injuries and discover more donor resources.