Effect of mRNA vaccination on pulmonary sequelae after mild COVID-19 (preprint)

Background: Previous studies indicate a protective role for SARS-CoV-2 vaccination against development of pulmonary post-acute sequelae of COVID (PASC). We compared clinical, imaging, histopathology and ultrastructural features of pulmonary PASC with and without prior vaccination in a consecutive cohort of 54 unvaccinated, 17 partially vaccinated and 28 fully vaccinated patients who presented with dyspnea on exertion after mild COVID-19 (without hospitalization). Methods: Patients underwent full clinical evaluation including autoantibody (ANA/ENA) serology, high-resolution computed tomography (HRCT), bronchioloalveolar lavage fluid (BAL) analysis and transbronchial biopsy followed by histopathological and ultrastructural analysis and SARS-CoV-2 immunohistochemistry. Results: While vaccinated patients were younger (p=0.0056), included more active smokers (p=0.0135) and a longer interval since infection (35 vs. 17 weeks, p=0.0002), dyspnea on exertion and impaired lung function were not different between vaccinated and unvaccinated patients. Ground glass opacities in HRCT and centrilobular fibrosis were more frequent in unvaccinated patients (p=0.0154 and p=0.0353), but presence of autoantibodies, BAL lymphocytosis and bronchiolitis were common findings in all groups. While vaccination against SARS-CoV-2 is associated with a longer time span between infection and consultation along with a reduced frequency of ground glass opacities and centrilobular fibrosis, impaired lung function, bronchiolitis and presence of autoantibodies are comparable between vaccinated and unvaccinated patients. Residual virus was not detected in lung tissue in all but 1 patient. Conclusion: While differences between the investigated groups with regard to age, smoking status and SARS-CoV-2 variants have to be taken into account, a proposed protective role of SARS-CoV-2 vaccination against pulmonary PASC is so far not fully explained by clinical and histopathology findings.

Clinical, imaging, serological, and histopathological features of pulmonary post-acute sequelae after mild COVID-19 (PASC) (preprint)

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.

A scoping review of regulatory T cell dynamics in convalescent COVID-19 patients - Implications for Long COVID? (preprint)

Background: Recovery from coronavirus disease 2019 (COVID-19) can be impaired by the persistence of symptoms or new-onset health complications, commonly referred to as Long COVID. In a subset of patients, Long COVID is associated with immune system perturbations of unknown etiology, which could be related to compromised immunoregulatory mechanisms. Objective: The aim of this scoping review was to investigate if regulatory T cell (Treg) dysregulation is observable beyond the acute illness and if it might be involved in Long COVID immunopathology. Design: A systematic search of studies investigating Tregs during COVID-19 convalescence was conducted on MEDLINE (via Pubmed) and Web of Science. Results: The literature search yielded 17 relevant studies, of which three included a distinct cohort of patients with Long COVID. The reviewed studies suggest that the Treg population of COVID-19 patients can reconstitute quantitatively and functionally during recovery. However, the comparison between recovered and seronegative controls revealed that an infection-induced dysregulation of the Treg compartment can be sustained for at least several months. The small number of studies investigating Tregs in Long COVID allowed no firm conclusions to be drawn about their involvement in the syndrome's etiology. Yet, even almost one year post-infection Long COVID patients exhibit significantly altered proportions of Tregs within the CD4+ T cell population. Conclusions: Persistent alterations in cell frequency in Long COVID patients indicate that Treg dysregulation might be linked to immune system-associated sequelae. Future studies should aim to address the association of Treg adaptations with different symptom clusters and blood parameters beyond the sole quantification of cell frequencies while adhering to consensualized phenotyping strategies.

Antemortem vs. postmortem histopathological and ultrastructural findings in paired transbronchial biopsies and lung autopsy samples from three patients with confirmed SARS-CoV-2 infection (preprint)

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.