Plasmacytoid dendritic cells regulate megakaryocyte and platelet homeostasis (preprint)

Platelet homeostasis is essential for vascular integrity and immune defense. While the process of platelet formation by fragmenting megakaryocytes (thrombopoiesis) has been extensively studied, the cellular and molecular mechanisms required to constantly replenish the pool of megakaryocytes by their progenitor cells (megakaryopoiesis) remains unclear. Here we use intravital 2 photon microscopy to track individual megakaryopoiesis over days. We identify plasmacytoid dendritic cells (pDCs) as crucial bone marrow niche cells that regulate megakaryopoiesis. pDCs monitor the bone marrow for platelet-producing megakaryocytes and deliver IFN-a to the megakaryocytic niche to trigger local on-demand proliferation of megakaryocyte progenitors. This fine-tuned coordination between thrombopoiesis and megakaryopoiesis is crucial for megakaryocyte and platelet homeostasis in steady state and stress. However, uncontrolled pDC function within the megakaryocytic niche is detrimental. Accordingly, we show that pDCs activated by SARS-CoV2 drive inappropriate megakaryopoiesis associated with thrombotic complications. Together, we uncover a hitherto unknown megakaryocytic bone marrow niche maintained by the constitutive delivery of pDC-derived IFN-a.

Aspergillus Tracheobronchitis in COVID-19 ARDS Patients – A Cohort Study (preprint)

Background: Coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome patients are at risk for fungal infections, especially aspergillosis and mucormycosis. COVID-19-associated pulmonary aspergillosis (CAPA) is differentiated in a pulmonary form and Aspergillus tracheobronchitis (ATB). During the first wave of the pandemic, bronchoscopy for diagnosing Aspergillus superinfections was rarely performed in COVID-19 patients, so that detailed on data on ATB in CAPA patients is scarce. We analyzed prevalence and mortality of tracheobronchitis in patients with CAPA.Methods: We conducted a retrospective, single-centre study at the 14-bed intensive care unit (ICU) of the Department I of Internal Medicine of the University Hospital of Cologne, Germany from March 2020 to February 2021. CAPA patients were identified by twice weekly analysis of tracheal aspirates for Aspergillus growth, Aspergillus DNA (PCR) and galactomannan combined with serum galactomannan testing. In case of positive results, bronchoscopy with the examination of trachea and lower airways and bronchoalveolar lavage followed.Findings: A total of 69 COVID-19 patients were admitted to the ICU, with 17 patients developing probable CAPA. All CAPA patients received bronchoscopy resulting in a clinical diagnosis of tracheobronchitis in 8 patients with signs of tracheal lesions, pseudomembranes or vulnerable bloody trachea. Seven bronchoalveolar lavages revealed culture and eight PCR positivity for Aspergillus fumigatus. In 7 of 8 tracheobronchitis patients, bronchoalveolar lavage samples tested positive for galactomannan antigen optical density index of >0.5. The overall mortality of CAPA patients was 52.9% and the overall mortality of ATB patients was 75%.Interpretation: Our data indicate a substantial prevalence of tracheobronchitis in this single-center cohort of CAPA patients. To facilitate early diagnosis bronchoscopic tracheal examination is crucial as computed tomography lacks diagnostic accuracy to enable timely initiation of therapy.Funding Information: This work was in part supported by the German Registry of COVID-19 Autopsies (www.DeRegCOVID.ukaachen.de), funded by the Federal Ministry of Health (ZMVI1-2520COR201), and the project DEFEAT PANDEMICs, funded by the Federal Ministry of Education and Research (01KX2021).Declaration of Interests: PK reports grants or contracts from German Federal Ministry of Research and Education and the State of North Rhine-Westphalia; Consulting fees Ambu GmbH, Gilead Sciences, Noxxon N.V. and Pfizer Pharma; Honoraria for lectures from Akademie für Infektionsmedizin e.V., Ambu GmbH, Astellas Pharma, BioRad Laboratories Inc., European Confederation of Medical Mycology, Gilead Sciences, GPR Academy Ruesselsheim, medupdate GmbH, MedMedia, MSD Sharp & Dohme GmbH, Pfizer Pharma GmbH, Scilink Comunicación Científica SC and University Hospital and LMU Munich; Participation on an Advisory Board from Ambu GmbH, Gilead Sciences, Pfizer Pharma; A pending patent currently reviewed at the German Patent and Trade Mark Office; Other non-financial interests from Elsevier, Wiley and Taylor & Francis online outside the submitted work. SvS none. JGB reports scientific grants and travel expenses from Kite/Gilead outside the submitted work. FF has a clinician scientist position supported by the deans office, medical faculty, University of Cologne. JSG none. FP none. BB reports honoraria, travel expenses and advisory role from/for Astellas, Celgene, Johnson & Johnson, Kite/Gilead, MSD, Novartis, Pfizer, Takeda and financing of scientific research by Astellas, Celgene, Kite/Gilead, MSD and Takeda outside the submitted work. DAE received honoraria from Sanofi and TAKEDA outside the submitted work. ASV reports travel grants from Gilead Sciences outside the submitted work. OK reports payment or honoraria for lectures, presentations or speakers bureaus by Gilead and Pfizer and receipt of equipment, materials, drugs, medical writing, gifts or other services by Pfizer, MSD, Basilea, Gilead, Virotech and Wako Fujifilm outside the submitted work. PB none. MK reports payment or honoraria for lectures, presentations or speakers bureaus by Gilead, MSD and Pfizer outside the submitted work. OAC reports grants or contracts from Amplyx, Basilea, BMBF, Cidara, DZIF, EU-DG RTD (101037867), F2G, Gilead, Matinas, MedPace, MSD, Mundipharma, Octapharma, Pfizer, Scynexis; Consulting fees from Amplyx, Biocon, Biosys, Cidara, Da Volterra, Gilead, Matinas, MedPace, Menarini, Molecular Partners, MSG-ERC, Noxxon, Octapharma, PSI, Scynexis, Seres; Honoraria for lectures from Abbott, Al 344 Jazeera Pharmaceuticals, Astellas, Grupo Biotoscana/United Medical/Knight, Hikma, MedScape, MedUpdate, Merck/MSD, Mylan, Pfizer; Payment for expert testimony from Cidara; Participation on a Data Safety Monitoring Board or Advisory Board from Actelion, Allecra, Cidara, Entasis, IQVIA, Jannsen, MedPace, Paratek, PSI, Shionogi; A pending patent currently reviewed at the German Patent and Trade Mark Office; Other interests from DGHO, DGI, ECMM, ISHAM, MSG-ERC, Wiley outside the submitted work.Ethics Approval Statement: Patients with CAPA were included in the FungiScope® global registry for emerging invasive fungal infections (https://www.clinicaltrials.gov; National Clinical Trials identifier NCT01731353), which was approved by the local ethics committee of the University of Cologne, Cologne, Germany (identifier 05-102).

Contamination of personal protective equipment during COVID-19 autopsies (preprint)

Confronted with an emerging infectious disease, the medical community faced relevant concerns regarding the performance of autopsies of COVID-19 deceased at the beginning of the pandemic. This attitude has changed, and autopsies are now recognized as indispensable tools for elucidating COVID-19; despite this, the true risk of infection for autopsy staff is still debated. To elucidate the rate of SARS-CoV-2 contamination in personal protective equipment (PPE), swabs were taken at nine locations of the PPE of one physician and an assistant each from 11 full autopsies performed at four different centers. Further samples were obtained for three minimally invasive autopsies (MIA) conducted at a fifth center. Lung/bronchus swabs of the deceased served as positive controls. SARS-CoV-2 RNA was detected by RT-qPCR. In 9/11 full autopsies PPE samples were tested RNA positive with PCR, in total 21% of all PPE samples taken. The main contaminated parts of the PPE were the gloves (64% positive), the aprons (50% positive), and the upper sides of shoes (36% positive) while for example the fronts of safety goggles were only positive in 4.5% of the samples and all face masks were negative. In MIA, viral RNA was observed in one sample from a glove, but not in other swabs. Infectious virus isolation in cell culture was performed in RNA positive swabs from full autopsies. Of all RNA positive PPE samples, 21% of the glove samples were positive for infectious virus taken in 3/11 full autopsies. In conclusion, in >80% of autopsies, PPE was contaminated with viral RNA. In >25% of autopsies, PPE was found to be even contaminated with infectious virus, signifying a potential risk of infection among autopsy staff. Adequate PPE and hygiene measures, including appropriate waste deposition, are therefore mandatory to enable safe work environment.

Multisystemic cellular tropism of SARS-CoV-2 in autopsies of COVID-19 patients (preprint)

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.

Native Endogenous Fluorescence Imaging Detects Vascular Occlusions in Patients with COVID-19 (preprint)

Background: A number of histopathological reports showed the presence of widespread thrombosis and associated morphology in pulmonary vessels of patients with COVID-19. Later, we identified vascular occlusions with neutrophils and neutrophil extracellular traps (NETs), as major components, in autopsy tissue from patients with COVID-19.Methods: We, here investigated 109 lung specimens from 17 patients with COVID-19 and compared them with 11 lung specimens from two patients who succumbed to pulmonary embolism and acute cardiac. Healthy lung specimens from four patients served as controls. We studied these autopsy lung specimens using immunohistochemistry and native endogenous fluorescence.Findings: We present a label-free imaging technique using native endogenous fluorescence that enables the visualization of occluded vessels. We demonstrate that native endogenous fluorescence identified occluded vessels in tissue specimens from patients with COVID-19.Interpretation: Label-free detection of occluded vessels enabled the detection of affected occluded vessels in lung specimens of patients with COVID-19 where the occluding components showed varying contents of neutrophil-derived materials.Funding Statement: Deutsche Forschungsgemeinschaft (DFG), EU, Volkswagen-StiftungDeclaration of Interests: All authors have no conflicts of interests to declare.Ethics Approval Statement: An institutional approval from each local Ethical Committee was obtained (permit #193_13B; permit # 174_20B; EK 092/20; EK 119/20; EK 460/20).