High Levels of NfL, GFAP, TAU, and UCH-L1 as Potential Predictor Biomarkers of Severity and Lethality in Acute COVID-19

Few studies showed that neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), total tubulin-associated unit (TAU), and ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) may be related to neurological manifestations and severity during and after SARS-CoV-2 infection. The objective of this work was to investigate the relationship among nervous system biomarkers (NfL, TAU, GFAP, and UCH-L1), biochemical parameters, and viral loads with heterogeneous outcomes in a cohort of severe COVID-19 patients admitted in Intensive Care Unit (ICU) of a university hospital. For that, 108 subjects were recruited within the first 5 days at ICU. In parallel, 16 mild COVID-19 patients were enrolled. Severe COVID-19 group was divided between "deceased" and "survivor." All subjects were positive for SARS-CoV-2 detection. NfL, total TAU, GFAP, and UCH-L1 quantification in plasma was performed using SIMOA SR-X platform. Of 108 severe patients, 36 (33.33%) presented neurological manifestation and 41 (37.96%) died. All four biomarkers - GFAP, NfL, TAU, and UCH-L1 - were significantly higher among deceased patients in comparison to survivors (p < 0.05). Analyzing biochemical biomarkers, higher Peak Serum Ferritin, D-Dimer Peak, Gamma-glutamyltransferase, and C-Reactive Protein levels were related to death (p < 0.0001). In multivariate analysis, GFAP, NfL, TAU, UCH-L1, and Peak Serum Ferritin levels were correlated to death. Regarding SARS-CoV-2 viral load, no statistical difference was observed for any group. Thus, Ferritin, NFL, GFAP, TAU, and UCH-L1 are early biomarkers of severity and lethality of SARS-COV-2 infection and may be important tools for therapeutic decision-making in the acute phase of disease.

Long COVID: plasma levels of neurofilament light chain in mild COVID-19 patients with neurocognitive symptoms

It is well known the potential of severe acute respiratory coronavirus type 2 (SARS-CoV-2) infection to induce post-acute sequelae, a condition called Long COVID. This syndrome includes several symptoms, but the central nervous system (CNS) main one is neurocognitive dysfunction. Recently it has been demonstrated the relevance of plasma levels of neurofilament light chain (pNfL), as a biomarker of early involvement of the CNS in COVID-19. The aim of this study was to investigate the relationship between pNfL in patients with post-acute neurocognitive symptoms and the potential of NfL as a prognostic biomarker in these cases. A group of 63 long COVID patients ranging from 18 to 59 years-old were evaluated, submitted to a neurocognitive battery assessment, and subdivided in different groups, according to results. Plasma samples were collected during the long COVID assessment and used for measurement of pNfL with the Single molecule array (SIMOA) assays. Levels of pNfL were significantly higher in long COVID patients with neurocognitive symptoms when compared to HC (p = 0.0031). Long COVID patients with cognitive impairment and fatigue symptoms presented higher pNfL levels when compared to long COVID patients without these symptoms, individually and combined (p = 0.0263, p = 0.0480, and 0.0142, respectively). Correlation analysis showed that levels of cognitive lost and exacerbation of fatigue in the neurocognitive evaluation had a significative correlation with higher pNfL levels (p = 0.0219 and 0.0255, respectively). Previous reports suggested that pNfL levels are related with higher risk of severity and predict lethality of COVID-19. Our findings demonstrate that SARS-CoV-2 infection seems to have a long-term impact on the brain, even in patients who presented mild acute disease. NfL measurements might be useful to identify CNS involvement in long COVID associated with neurocognitive symptoms and to identify who will need continuous monitoring and treatment support.

Molecular Mimicry between SARS-CoV-2 Proteins and Human Self-Antigens Related with Autoimmune Central Nervous System (CNS) Disorders

SARS-CoV-2 can trigger autoimmune central nervous system (CNS) diseases in genetically susceptible individuals, a mechanism poorly understood. Molecular mimicry (MM) has been identified in other viral diseases as potential triggers of autoimmune CNS events. This study investigated if MM is the process through which SARS-CoV-2 induces the breakdown of immune tolerance. The frequency of autoimmune CNS disorders was evaluated in a prospective cohort with patients admitted to the COVID-19 Intense Care Unity (ICU) in Rio de Janeiro. Then, an in silico analysis was performed to identify the conserved regions that share a high identity between SARS-CoV-2 antigens and human proteins. The sequences with significant identity and antigenic properties were then assessed for their binding capacity to HLA subtypes. Of the 112 patients included, 3 were classified as having an autoimmune disorder. A total of eleven combinations had significant linear and three-dimensional overlap. NMDAR1, MOG, and MPO were the self-antigens with more significant combinations, followed by GAD65. All sequences presented at least one epitope with strong or intermediate binding capacity to the HLA subtypes selected. This study underscores the possibility that CNS autoimmune attacks observed in COVID-19 patients, including those in our population, could be driven by MM in genetically predisposed individuals.

Clinical Profile and Risk Factors for Severe COVID-19 in Hospitalized Patients from Rio de Janeiro, Brazil: Comparison between the First and Second Pandemic Waves

Since COVID-19 was declared a pandemic, Brazil has become one of the countries most affected by this disease. A year into the pandemic, a second wave of COVID-19 emerged, with a rapid spread of a new SARS-CoV-2 lineage of concern. Several vaccines have been granted emergency-use authorization, leading to a decrease in mortality and severe cases in many countries. However, the emergence of SARS-CoV-2 variants raises the alert for potential new waves of transmission and an increase in pathogenicity. We compared the demographic and clinical data of critically ill patients infected with COVID-19 hospitalized in Rio de Janeiro during the first and second waves between July 2020 and October 2021. In total, 106 participants were included in this study; among them, 88% had at least one comorbidity, and 37% developed severe disease. Disease severity was associated with older age, pre-existing neurological comorbidities, higher viral load, and dyspnea. Laboratory biomarkers related to white blood cells, coagulation, cellular injury, inflammation, renal, and liver injuries were significantly associated with severe COVID-19. During the second wave of the pandemic, the necessity of invasive respiratory support was higher, and more individuals with COVID-19 developed acute hepatitis, suggesting that the progression of the second wave resulted in an increase in severe cases. These results can contribute to understanding the behavior of the COVID-19 pandemic in Brazil and may be helpful in predicting disease severity, which is a pivotal for guiding clinical care, improving patient outcomes, and defining public policies.

A comparison between bromodeoxyuridine and 3H thymidine labeling in human breast tumors

The fraction of tumor cells in the DNA synthesis (S) phase of the cell cycle is a strong prognostic indicator in human breast cancer. Most studies measuring S-phase in primary tumors have used either in vitro labeling with 3H thymidine or DNA flow cytometry. The former involves a cumbersome and time-consuming radioactive assay, while the latter is heavily dependent on the quality of the preparation and the effectiveness of the algorithms used. In this study, in vivo or in vitro labeling with bromodeoxyuridine (BrdUrd) was compared with in vitro labeling using 3H thymidine in a series of 33 human breast tumors. Thymidine labeling showed strong correlation with both in vitro (r = 0.96) and in vivo (r = 0.83) BrdUrd incorporation. The reliability between observers was higher for BrdUrd counting (r = 0.94) than for thymidine counting (r = 0.87). The mean labeling index of 15 tumors labeled in vivo with BrdUrd was 5.9% compared to 4.7% for 18 tumors labeled in vitro (p = 0.34). There was poor correlation between flow cytometric and microscopic analysis of BrdUrd incorporation (r = 0.37). We conclude that microscopic analysis of in vivo or in vitro BrdUrd incorporation is a rapid and reliable method to estimate breast tumor proliferation.

Proliferation of normal breast epithelial cells as shown by in vivo labeling with bromodeoxyuridine

The proliferative activity of normal acinar and ductal breast epithelial cells was studied by in vivo labeling with 5-bromodeoxyuridine (BrdUrd) in 26 cases with concurrent breast carcinoma. The BrdUrd-labeled cells were recognized in histologic sections of paraffin-embedded tissue, using an anti-BrdUrd antibody and an immunoperoxidase reaction. The percentage of BrdUrd-labeled cells showed great variability for both acinar (0% to 2.66%; mean, 0.70%; standard deviation [SD], 0.80%) and ductal cells (0% to 1.99%; mean, 0.51%; SD, 0.57%). The fraction of proliferating epithelial cells declined with the age of the patients and was significantly higher in premenopausal women (1.16% +/- 0.85% for acinar and 0.94% +/- 0.60% for ductal cells) as compared with the postmenopausal women (0.27% +/- 0.46% for acinar and 0.17% +/- 0.22% for ductal cells), P less than 0.01 for acinar and P less than 0.001 for ductal cells, respectively. In some patients, great variability in distribution of proliferating acinar and ductal cells among different lobules and ducts was observed. No difference was found in the number of proliferating acinar and ductal cells situated near or far from their corresponding tumors. No correlation was seen between cell proliferation of normal acinar or ductal cells and cell proliferation of the respective tumors.

Characterization by image cytometry of duct epithelial proliferative disease of the breast

To develop a morphometric model of premalignant breast epithelium, we evaluated 120 lesions classified as nonproliferative disease (n = 20), hyperplasia (n = 20), moderate hyperplasia (n = 20), atypical hyperplasia (n = 20), carcinoma in situ (n = 20), and carcinoma (n = 20) in tissue from surgical biopsy or mastectomy. Atypical hyperplasia, a component of duct epithelial proliferative disease, has frequently been described in breasts with carcinoma. Atypical hyperplasia is generally viewed as premalignant or as a marker of increased risk for breast cancer. Measurements of nuclei in breast lesions were obtained with the Leitz TAS Plus on 4-microns sections stained for DNA with the Azure A Feulgen reaction. Nuclei of duct epithelial lesions had morphometric features that displayed changes from nonproliferative disease to carcinoma. The morphometric data from each lesion were compared among the six disease groups. Means of nuclear area, perimeter, maximum and minimum diameter, and large dark and large light intranuclear areas increased with higher degrees of proliferative abnormality. When the six groups of lesions were compared using the means of the first four nuclear features, atypical hyperplasia was significantly different (P less than 0.05) from carcinoma and non-proliferative lesions, but not from hyperplasia, moderate hyperplasia, or carcinoma in situ. These findings suggest that objective morphometric descriptors for characterizing significant proliferative lesions can be established using image cytometry. The progressive increases also suggest that proliferative breast disease is a continuum that includes premalignant lesions.