ABSTRACT
Background: A significant proportion of patients experience prolonged pulmonary, cardiocirculatory or neuropsychiatric symptoms after Coronavirus disease 2019 (COVID-19), termed post-acute sequelae of COVID (PASC). Lung manifestations of PASC include cough, dyspnea on exertion and persistent radiologic abnormalities and have been linked to viral persistence, ongoing inflammation and immune dysregulation. So far, there is limited data on lung histopathology and tissue-based immune cell subtyping in PASC. Methods: 51 unvaccinated patients (median age, 40 years; 43% female) with a median of 17 weeks (range, 2-55 weeks) after mild SARS-CoV-2 infection (without hospitalization) underwent full clinical evaluation including high-resolution computed tomography (HR-CT) and transbronchial biopsy. We used RT-PCR/FISH and immunohistochemistry (nucleocapsid/spike/CD3/CD4/CD8) for residual SARS-CoV-2 detection and T lymphocyte subtyping, respectively. We assessed interstitial fibrosis and macrophage profiles by transmission electron microscopy (TEM) and immunofluorescence multiplex staining, while cytokine profiling in broncho-alveolar lavage (BAL) fluid was performed by legendplex immunoassay. Results: Dyspnea on exertion was the leading symptom of pulmonary PASC in our cohort. In 16% and 42.9% of patients, FEV1 and MEF50 were [≤]80% and 35.3% showed low attenuation volume (LAV) in >5% of lung area, in line with airflow obstruction. There was a significant correlation between oxygen pulse and time since COVID (p=0.009). Histopathologically, PASC manifested as organizing pneumonia (OP), fibrinous alveolitis and increased CD4+ T cell infiltrate predominantly around airways (bronchiolitis), while the residual virus components were detectable in only a single PASC patient (2%). T cell infiltrates around small airways were inversely correlated with time since COVID, however, this trend failed to reach statistical significance. We identified discrete interstitial fibrosis and a pro-fibrotic macrophage subtype (CD68/CD163/S100A9) as well as significantly elevated interleukin 1{beta} in BAL fluid from PASC patients (p=0.01), but H-scores for fibrotic macrophage population did not correlate with severity of clinical symptoms or T cell infiltration. Interpretation: We show decreased FEV1/MEF50 and increased LAV in line with obstructive lung disease due to CD4+ T cell-predominant bronchiolitis as well as evidence of pro-fibrotic signaling in a subset of unvaccinated PASC patients. Since our results point towards self-limiting inflammation of small airways without detectable viral reservoirs, it remains unclear whether pulmonary symptoms in PASC are SARS-CoV-2-specific or represent a general response to viral infection. Still, evidence of pro-fibrotic signaling should warrant clincal follow-up and further research into possible long-time fibrotic remodeling in PASC patients.
Subject(s)
Fibrosis , Bronchiolitis , Adenocarcinoma, Bronchiolo-Alveolar , Lung Diseases, Obstructive , Dyspnea , Pneumonia , Mental Disorders , Virus Diseases , COVID-19 , Inflammation , Pulmonary FibrosisABSTRACT
Background Multiorgan tropism of SARS-CoV-2 has previously been shown for several major organs. Methods We have comprehensively analyzed 25 different formalin-fixed paraffin-embedded (FFPE) tissues/organs from autopsies of fatal COVID-19 cases (n=8), using detailed histopathological assessment, detection of SARS-CoV-2 RNA using polymerase chain reaction and RNA in situ hybridization, viral protein using immunohistochemistry, and virus particles using transmission electron microscopy. Finally, we confirmed these findings in an independent external autopsy cohort (n=9). Findings SARS-CoV-2 RNA was mainly localized in epithelial cells, endothelial and mesenchymal cells across all organs. Next to lung, trachea, kidney, heart, or liver, viral RNA was also found in tonsils, salivary glands, oropharynx, thyroid, adrenal gland, testicles, prostate, ovaries, small bowel, lymph nodes, skin and skeletal muscle. Viral RNA was predominantly found in cells expressing ACE2, TMPRSS2, or both. The SARS-CoV-2 replicating RNA was also detected in these organs. Immunohistochemistry and electron microscopy were not suitable for reliable and specific SARS-CoV-2 detection in autopsies. The findings were validated using in situ hybridization on external COVID-19 autopsy samples. Finally, apart from the lung, correlation of virus detection and histopathological assessment did not reveal any specific alterations that could be attributed to SARS-CoV-2. Interpretation SARS-CoV-2 could be observed in virtually all organs, colocalizing with ACE2 and TMPRSS2 mainly in epithelial but also in mesenchymal and endothelial cells, and viral replication was found across all organ systems. Apart from the respiratory tract, no specific (histo-)morphologic alterations could be assigned to the SARS-CoV-2 infection. Research in context Evidence before this study SARS-CoV-2 has been shown to infect the respiratory tract and affect several other major organs. However, on a cellular level, the localization of SARS-CoV-2 and its targets ACE2 and TMPRSS2 have not been described comprehensively. Added value of this study We have analyzed tissue SARS-CoV-2 RNA using RT-PCR and visualized its localization together with ACE2 and TMPRSS2 using in situ hybridization (ISH) in 25 different autopsy tissues. SARS-CoV-2 sense and antisense RNA were detected in 16 tissues/organs, mainly in epithelial cells and, to a lesser extent, in endothelial or stromal cells. Detection of viral protein using immunohistochemistry or viral particles using transmission electron microscopy did not yield specific results. Interestingly, apart from the respiratory tract and specifically the lungs, we have not found a specific pathology that would be associated with extrapulmonary viral spread. Implications of all the available evidence We provide a recommendation on using these methods in autopsy diagnostics for SARS-CoV-2. Our data extend the current hypothesis of severe COVID-19 being multisystemic diseases. Our data also provide clear evidence of infection and replication of SARS-CoV-2 in the endothelial cell across all organs, extending the hypothesis on the (micro)vascular involvement in COVID-19.
Subject(s)
COVID-19 , DiseaseABSTRACT
Virus detection methods are important to cope with the SARS-CoV-2 pandemics. Apart from the lung, SARS-CoV-2 was detected in multiple organs in severe cases. Less is known on organ tropism in patients developing mild or no symptoms, and some of such patients might be missed in symptom-indicated swab testing. Here we tested and validated several approaches and selected the most reliable RT-PCR protocol for the detection of SARS-CoV-2 RNA in patients' routine diagnostic formalin-fixed and paraffin-embedded (FFPE) specimens available in pathology, to assess a) organ tropism in samples from COVID-19-positive patients, b) unrecognized cases in selected tissues from negative or not-tested patients during a pandemic peak, and c) retrospectively, pre-pandemic lung samples. We identified SARS-CoV-2 RNA in four samples from confirmed COVID-19 patients, in two gastric biopsies, one colon resection, and one pleural effusion specimen, while all other specimens, particularly from patients with mild COVID-19 disease course, were negative. In the pandemic peak cohort, we identified one previously unrecognized COVID-19 case in tonsillectomy samples. All pre-pandemic lung samples were negative. In conclusion, SARS-CoV-2 RNA detection in FFPE pathology specimens can potentially improve surveillance of COVID-19, allow retrospective studies, and advance our understanding of SARS-CoV-2 organ tropism and effects.
Subject(s)
COVID-19 , Severe Acute Respiratory Syndrome , Pleural EffusionABSTRACT
BackgroundAcute respiratory distress syndrome (ARDS) is the major cause of death in coronavirus disease 2019 (COVID-19). Multiple autopsy-based reports of COVID-19 lung pathology describe diffuse alveolar damage (DAD), organizing pneumonia (OP) and fibrotic change, but data on early pathological changes as well as during progression of the disease are rare. Research questionComparison of histopathological and ultrastructural findings in paired transbronchial biopsies (TBBs) and autopsy material from three patients with confirmed SARS-CoV-2-infection. MethodsWe prospectively enrolled 3 patients with confirmed SARS-CoV-2 infection. Full clinical evaluation was performed including high-resolution computed tomography (HR-CT). We took TBBs at different time points during the disease and autopsy tissue samples after the patients death. ResultsSARS-CoV-2 was detected by RT-PCR and/or FISH in all TBBs. Lung histology revealed pneumocyte hyperplasia and capillary congestion in one patient who died short after hospital admission with detectable virus in 1/2 autopsy samples from the lung. SARS-CoV-2 was detected in 2/2 autopsy samples from a patient with a fulminant course of the disease and very short latency between biopsy and autopsy, both showing widespread DAD. In a third patient with a prolonged course, i.e. five weeks of ICU treatment with ECMO, autopsy samples showed extensive interstitial fibrosis without detectable virus by RT-PCR and/or FISH. InterpretationWe report the course of COVID-19 in paired TBB and autopsy samples from three patients at an early stage, in rapidly progressive and in a prolonged disease course. Our findings illustrate vascular, organizing and fibrotic patterns of COVID-19-induced lung injury and suggest an early spread of SARS-CoV-2 from the upper airways to the lung periphery with diminishing viral load during disease.