Plasma proteomic evidence for increased Alzheimer's disease-related brain pathology after SARS-CoV-2 infection (preprint)

Viral infections have been linked to an increased risk for dementia. We investigated whether SARS-CoV-2 infection increases preclinical brain pathology associated with Alzheimer's disease (AD) by comparing changes in plasma biomarkers in UK Biobank participants with and without prior SARS-CoV-2 infection. We discovered an association between SARS-CoV-2 infection and reduced plasma A{beta}42:A{beta}40 concentration ratio. In older participants, SARS-CoV-2 infection was associated with both lower plasma A{beta}42 and higher plasma pTau-181. These biomarker changes, which have been associated with beta-amyloid accumulation and prodromal AD, were associated with increased brain imaging signatures of AD, poorer cognitive scores, and worse assessments of overall health and appeared to be greater in participants who had been hospitalised with COVID-19. Protein biomarker risk scores for other diseases were also raised among individuals who had past SARS-CoV-2 infections. Our data provide support for the hypothesis that viral infections can accelerate prodromal AD pathology and highlight biomarker profiles indicative of an increased risk of dementia and systemic diseases after SARS-CoV-2 infection, particularly in older people.

Prevalence and predictors of long COVID among non-hospitalised adolescents and young adults: a prospective controlled cohort study (preprint)

The prevalence and predictors of long COVID in young people remain unresolved. We aimed to determine the point prevalence of long COVID in non-hospitalised adolescents and young adults six months after the acute infection, to determine the risk of developing long COVID adjusted for possible confounders, and to explore a broad range of potential risk factors (prespecified outcomes). We conducted a prospective controlled cohort study of 404 SARS-CoV-2-positive and 105 SARS-CoV-2-negative non-hospitalised individuals aged 12–25 years (ClinicalTrial ID: NCT04686734). Data acquisition was completed February 2022. Assessments included pulmonary, cardiac and cognitive functional testing, biomarker analyses, and completion of a questionnaire, and were performed at inclusion (early convalescent stage) and six months follow-up. The WHO case definition of long COVID was applied. The point prevalence of long COVID at six months was 49% and 47% in the SARS-CoV-2-positive and negative group, respectively. SARS-CoV-2-positivity did not predict development of long COVID (relative risk 1.06, 95% CI 0.83 to 1.37). The main predictor was symptom severity at inclusion, which correlated strongly to personality traits. Low physical activity and loneliness were also predictive, while biological markers were not. In conlusion, our study aims were met, and the findings suggest that persistent symptoms were not driven by the infection, but were associated with psychosocial factors.

Central nervous system biomarkers GFAp and NfL associate with post-acute cognitive impairment and fatigue following critical COVID-19 (preprint)

Background A high proportion of patients with coronavirus disease 2019 (COVID-19) experience post-acute COVID-19, including neuropsychiatric symptoms. Objective signs of central nervous system (CNS) damage can be investigated using CNS biomarkers such as glial fibrillary acidic protein (GFAp), neurofilament light chain (NfL) and total tau (t-tau). We have examined whether CNS biomarkers can predict fatigue and cognitive impairment 3–6 months after discharge from the intensive care unit (ICU) in critically ill COVID-19 patients.Methods Fifty-seven COVID-19 patients admitted to the ICU were included with analysis of CNS biomarkers in blood at the ICU and at follow up. Cognitive dysfunction and fatigue were assessed with the Montreal Cognitive Assessment (MoCA) and the Multidimensional Fatigue inventory (MFI-20).Results Elevated GFAp is associated to the development of mild cognitive dysfunction at follow-up (p = 0.01), especially in women (p = 0.005). Patients experiencing different dimensions of fatigue at follow-up had significantly lower GFAp, specifically in general fatigue (p = 0.009), physical fatigue (p = 0.004), mental fatigue (p = 0.001), and reduced motivation (p = 0.001). Women showed a more pronounced decrease in GFAp compared to men, except for mental fatigue where men showed a more pronounced GFAp decrease compared to women. NfL was lower in patients experiencing reduced motivation (p = 0.004).Conclusion Our findings suggest that GFAp and NfL are associated with neuropsychiatric outcome after critical COVID-19.Trial registration: The study was registered à priori (clinicaltrials.gov: NCT04316884 registered on 2020-03-13 and NCT04474249 registered on 2020-06-29).

Brain Injury in COVID-19 is Associated with Autoinflammation and Autoimmunity (preprint)

COVID-19 has been associated with many neurological complications including stroke, delirium and encephalitis. Furthermore, many individuals experience a protracted post-viral syndrome which is dominated by neuropsychiatric symptoms, and is seemingly unrelated to COVID-19 severity. The true frequency and underlying mechanisms of neurological injury are unknown, but exaggerated host inflammatory responses appear to be a key driver of severe COVID-19 more broadly. We sought to investigate the dynamics of, and relationship between, serum markers of brain injury (neurofilament light [NfL], Glial Fibrillary Acidic Protein [GFAP] and total Tau) and markers of dysregulated host response including measures of autoinflammation (proinflammatory cytokines) and autoimmunity. Brain injury biomarkers were measured using the Quanterix Simoa HDx platform, cytokine profiling by Luminex (R&D) and autoantibodies by a custom protein microarray. During hospitalisation, patients with COVID-19 demonstrated elevations of NfL and GFAP in a severity-dependant manner, and there was evidence of ongoing active brain injury at follow-up 4 months later. Raised NfL and GFAP were associated with both elevations of pro-inflammatory cytokines and the presence of autoantibodies; autoantibodies were commonly seen against lung surfactant proteins as well as brain proteins such as myelin associated glycoprotein, but reactivity was seen to a large number of different antigens. Furthermore, a distinct process characterised by elevation of serum total Tau was seen in patients at follow-up, which appeared to be independent of initial disease severity and was not associated with dysregulated immune responses in the same manner as NfL and GFAP.

Infection of brain pericytes underlying neuropathology of COVID-19 patients (preprint)

A wide range of neurological manifestations have been associated with the development of COVID-19 following SARS-CoV-2 infection. However, the etiology of the neurological symptomatology is still largely unexplored. Here, we used state-of-the-art multiplexed immunostaining of human brains ( n = 6 COVID-19, median age = 69,5 years; and n = 7 control, median age = 68 years), and demonstrated that expression of the SARS-CoV-2 receptor ACE2 is restricted to a subset of neurovascular pericytes. Strikingly, neurological symptoms were exclusive to, and ubiquitous in, patients that exhibited moderate to high ACE2 expression in peri-vascular cells. Viral particles were identified in the vascular wall and paralleled by peri-vascular inflammation, as signified by T cell and macrophage infiltration. Furthermore, fibrinogen leakage indicated compromised integrity of the blood-brain barrier. Notably, cerebrospinal fluid from an additional 16 individuals ( n = 8 COVID-19, median age = 67 years; and n = 8 control, median age = 69,5 years) exhibited significantly lower levels of the pericyte marker PDGFRβ in SARS-CoV-2-infected cases, indicative of disrupted pericyte homeostasis. We conclude that pericyte infection by SARS-CoV-2 underlies virus entry into the privileged central nervous system space, as well as neurological symptomatology due to peri-vascular inflammation and a locally compromised blood-brain barrier.

Critical Illness Polyneuropathy and Myopathy in COVID-19 Patients: A Prospective Observational Intensive Care Unit Cross-Sectional Cohort Study (preprint)

Background: Several reports on neurological complications associated with SARS-CoV-2 infection have been published. However, systematic description on intensive care unit acquired weakness (ICUAW) are still missing. Methods: The objective was to determine the incidence and characteristics of critical illness polyneuropathy (CIN) and myopathy (CIM) in patients with severe COVID-19. We also aimed to describe the electrophysiological features and their relation to plasma biomarkers for neuronal injury. This was a prospective observational intensive care unit cohort study. All adult patients admitted to the general intensive care unit (ICU) at Uppsala University Hospital, Uppsala, Sweden, between March 13 and June 8, 2020 were screened for inclusion. Patients with PCR confirmed COVID-19 were included. All patients were admitted to intensive care treatment due to severe COVID-19, including intravenous anaesthesia, opioid anaelgesia, neuromuscular blockade and mechanical ventilation. Associations of clinical, electrophysiological (sensory and motor conduction studies and electromyography) and biomarker data [neurofilament light chain (NfL), glial fibrillary acidic protein (GFAp) and tau] were studied between COVID-19 patients who developed CIN/CIM and those who did not. Results: 111 COVID-19 patients were included, 11 (11 males, mean age: 64 years) developed CIN/CIM whereas 100 (74 males, mean age: 61 years) did not (non-CIN/CIM). The CIN/CIM incidence was higher in COVID-19 patients compared to a general ICU-population treated during 2019 (9.9% vs 3.4%). In particular CIN was more frequent in the COVID-19 ICU cohort (50%) compared with the non-COVID-19 ICU cohort (0%, p=0.008). NfL and GFAp levels were higher in the CIN/CIM group both at the early (<9 days) and late time points (>11 days) compared with the non-CIN/CIM group (both p=0.001) and correlated with nerve amplitudes. Conclusions: CIN/CIM, in particular CIN, were more prevalent among COVID-19 patients than an ICU treated control cohort and should be considered in the differential diagnostic workup and the further rehabilitation of COVID-19 patients. COVID-19 patients who later developed ICUAW had significantly higher NfL and GFAp in the early phase of ICU care, which suggests their potential as predictive biomarkers. Trial registration: The study protocol was registered (ClinicalTrialsID:NCT04316884). Mechanisms for Organ Dysfunction in Covid-19 (UMODCOVID19) March 18, 2020.

Blood neurofilament light concentration at admittance: a potential prognostic marker in COVID-19 (preprint)

ObjectiveTo test the hypotheses that blood concentrations of neurofilament light chain protein (NfL) and glial fibrillary acidic protein (GFAp) can serve as biomarkers for disease severity in COVID-19 patients. MethodsForty-seven inpatients with confirmed COVID-19 had blood samples drawn on admission for assessing serum biomarkers of CNS injury by Single molecule array (Simoa). Concentrations of NfL and GFAp were analyzed in relation to symptoms, clinical signs, inflammatory biomarkers and clinical outcomes. We used multivariate linear models to test for differences in biomarker concentrations in the subgroups, accounting for confounding effects. ResultsIn total, 21 % (n = 10) of the patients were admitted to an intensive care unit, whereas the overall mortality rate was 13 % (n = 6). Non-survivors had higher serum concentrations of NfL than patients who were discharged alive both in adjusted analyses (p = 2.6 x 10-7) and unadjusted analyses (p = 0.001). Serum concentrations of GFAp were significantly higher in non-survivors than survivors in adjusted analyses (p = 0.02). The NfL concentrations in non-survivors increased over repeated measurements, whereas the concentrations in survivors were stable. Significantly higher concentrations of NfL were found in patients reporting fatigue, while reduced concentrations were found in patients experiencing cough, myalgia and joint pain. ConclusionIncreased concentrations of NfL and GFAp in COVID-19 patients on admission may indicate increased mortality risk. Measurement of blood biomarkers for nervous system injury can be useful to detect and monitor CNS injury in COVID-19.

Proteomic blood profiling in mild, severe and critical COVID-19 patients (preprint)

The recent SARS-CoV-2 pandemic manifests itself as a mild respiratory tract infection in the majority of individuals leading to COVID-19 disease. However, in some infected individuals, this can progress to severe pneumonia and acute respiratory distress syndrome (ARDS), leading to multi-organ failure and death. The purpose of this study is to explore the proteomic differences between mild, severe and critical COVID-19 positive patients. Blood protein profiling was performed on 59 COVID-19 mild (n=26), severe (n=9) or critical (n=24) cases and 28 controls using the OLINK inflammation, autoimmune, cardiovascular and neurology panels. Differential expression analysis was performed within and between disease groups to generate nine different analyses. From the 368 proteins measured per individual, more than 75% were observed to be significantly perturbed in COVID-19 cases. Six proteins (IL6, CKAP4, Gal-9, IL-1ra, LILRB4 and PD-L1) were identified to be associated with disease severity. The results have been made readily available through an interactive web-based application for instant data exploration and visualization, and can be accessed at https://phidatalab-shiny.rosalind.kcl.ac.uk/COVID19/. Our results demonstrate that dynamic changes in blood proteins that associate with disease severity can potentially be used as early biomarkers to monitor disease severity in COVID-19 and serve as potential therapeutic targets.

Steroid-responsive severe encephalopathy in SARS-CoV-2 infection (preprint)

SARS-CoV-2 infection has the potential for targeting central nervous system and several neurological symptoms have been described in patients with severe respiratory distress. Here we described the case of an otherwise healthy 60-year old subject with SARS-CoV-2 infection but only mild respiratory abnormalities who developed severe progressive encephalopathy associated with mild pleocytosis and hyperproteinorrachia. MRI was negative whereas EEG showed theta waves on the anterior brain regions. Serum and CSF analyses excluded other known infectious or autoimmune disorders. The patient dramatically improved after high-doses steroid treatment suggesting an inflammatory-mediated brain involvement related to SARS-CoV-2 infection