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Purpose: Few studies have compared patient characteristics, clinical management, and outcome of patients with COVID-19 between the different epidemic waves. In this study, we describe patient characteristics, treatment, and outcome of patients admitted for COVID-19 in the Antwerp University Hospital over the first three epidemic waves of 2020-2021., Methods: Retrospective observational study of COVID-19 patients in a Belgian tertiary referral hospital. All adult patients with COVID-19, hospitalized between February 29, 2020, and June 30, 2021, were included. Standardized routine medical data was collected from patient records. Risk factors were assessed with multivariable logistic regression., Results: We included 722 patients, during the first (n = 179), second (n = 347) and third (n = 194) wave. We observed the lowest disease severity at admission during the first wave, and more elderly and comorbid patients during the second wave. Throughout the subsequent waves we observed an increasing use of corticosteroids and high-flow oxygen therapy. In spite of increasing number of complications throughout the subsequent waves, mortality decreased each wave (16.6%,15.6% 11.9% in 1st, 2nd and 3rd wave respectively). C-reactive protein above 150 mg/L was predictive for the need for intensive care unit admission (odds ratio (OR) 3.77, 95% confidence interval (CI) 2.32-6.15). A Charlson comorbidity index ≥ 5 (OR 5.68, 95% CI 2.54-12.70) and interhospital transfers (OR 3.78, 95% CI 2.05-6.98) were associated with a higher mortality., Conclusions: We observed a reduction in mortality each wave, despite increasing comorbidity. Evolutions in patient management such as high-flow oxygen therapy on regular wards and corticosteroid use may explain this favorable evolution., (© 2024. The Author(s).)

T-cell-based diagnostic tools identify pathogen exposure but lack differentiation between recent and historical exposures in acute infectious diseases. Here, T-cell receptor (TCR) RNA sequencing was performed on HLA-DR+/CD38+CD8+ T-cell subsets of hospitalized coronavirus disease 2019 (COVID-19) patients (n = 30) and healthy controls (n = 30; 10 of whom had previously been exposed to severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]). CDR3α and CDR3β TCR regions were clustered separately before epitope specificity annotation using a database of SARS-CoV-2-associated CDR3α and CDR3β sequences corresponding to >1000 SARS-CoV-2 epitopes. The depth of the SARS-CoV-2-associated CDR3α/β sequences differentiated COVID-19 patients from the healthy controls with a receiver operating characteristic area under the curve of 0.84 ± 0.10. Hence, annotating TCR sequences of activated CD8+ T cells can be used to diagnose an acute viral infection and discriminate it from historical exposure. In essence, this work presents a new paradigm for applying the T-cell repertoire to accomplish TCR-based diagnostics., Competing Interests: Potential conflicts of interest . B. O., K. L., and P. M. are cofounders, board directors, and shareholders of ImmuneWatch. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Despite the general agreement on the significance of T cells during SARS-CoV-2 infection, the clinical impact of specific and cross-reactive T-cell responses remains uncertain. Understanding this aspect could provide insights for adjusting vaccines and maintaining robust long-term protection against continuously emerging variants. To characterize CD8+ T-cell response to SARS-CoV-2 epitopes unique to the virus (SC2-unique) or shared with other coronaviruses (CoV-common), we trained a large number of T-cell receptor (TCR) - epitope recognition models for MHC-I-presented SARS-CoV-2 epitopes from publicly available data. These models were then applied to longitudinal CD8+ TCR repertoires from critical and non-critical COVID-19 patients. In spite of comparable initial CoV-common TCR repertoire depth and CD8+ T-cell depletion, the temporal dynamics of SC2-unique TCRs differed depending on the disease severity. Specifically, while non-critical patients demonstrated a large and diverse SC2-unique TCR repertoire by the second week of the disease, critical patients did not. Furthermore, only non-critical patients exhibited redundancy in the CD8+ T-cell response to both groups of epitopes, SC2-unique and CoV-common. These findings indicate a valuable contribution of the SC2-unique CD8+ TCR repertoires. Therefore, a combination of specific and cross-reactive CD8+ T-cell responses may offer a stronger clinical advantage. Besides tracking the specific and cross-reactive SARS-CoV-2 CD8+ T cells in any TCR repertoire, our analytical framework can be expanded to more epitopes and assist in the assessment and monitoring of CD8+ T-cell response to other infections., Competing Interests: BO, KL, and PM are co-founders, board directors and shareholders of ImmuneWatch™. None of the work presented here was influenced in any way by this. ImmuneWatch™ had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Postovskaya, Vujkovic, de Block, van Petersen, van Frankenhuijsen, Brosius, Bottieau, Van Dijck, Theunissen, van Ierssel, Vlieghe, Bartholomeus, Mullan, Adriaensen, Vanham, Ogunjimi, Laukens, Vercauteren and Meysman.)

Background: COVID-19 patients experience several features of dysregulated immune system observed in sepsis. We previously showed a dysregulation of several proline-selective peptidases such as dipeptidyl peptidase 4 (DPP4), fibroblast activation protein alpha (FAP), prolyl oligopeptidase (PREP) and prolylcarboxypeptidase (PRCP) in sepsis. In this study, we investigated whether these peptidases are similarly dysregulated in hospitalized COVID-19 patients., Methods: Fifty-six hospitalized COVID-19 patients and 32 healthy controls were included. Enzymatic activities of DPP4, FAP, PREP and PRCP were measured in samples collected shortly after hospital admission and in longitudinal follow-up samples., Results: Compared to healthy controls, both DPP4 and FAP activities were significantly lower in COVID-19 patients at hospital admission and FAP activity further decreased significantly in the first week of hospitalization. While PRCP activity remained unchanged, PREP activity was significantly increased in COVID-19 patients at hospitalization and further increased during hospital stay and stayed elevated until the day of discharge., Conclusion: The changes in activities of proline-selective peptidases in plasma are very similar in COVID-19 and septic shock patients. The pronounced decrease in FAP activity deserves further investigation, both from a pathophysiological viewpoint and as its utility as a part of a biomarker panel., (Copyright © 2022 Elsevier B.V. All rights reserved.)