Plasma Biomarkers of Neuropathogenesis in Hospitalized Patients With COVID-19 and Those With Postacute Sequelae of SARS-CoV-2 Infection

Abstract

Background and objectives: Although patients hospitalized with COVID-19 frequently present with encephalopathy, those with mild initial COVID-19 disease who never required hospitalization also often develop neurologic symptoms as part of postacute sequelae of severe acute respiratory coronavirus type 2 (SARS-CoV-2) infection (neuro-PASC). The pathogenic mechanisms of COVID-19 encephalopathy and neuro-PASC are unknown. We sought to establish biochemical evidence of CNS injury in those patients and their association with neuropsychiatric manifestations and SARS-CoV-2 antigenemia.

Methods: We recruited hospitalized, posthospitalized, and nonhospitalized patients with confirmed diagnosis of COVID-19 with neurologic symptoms in addition to healthy control (HC) subjects. Plasma neurofilament light chain (pNfL), plasma glial fibrillary acidic protein (pGFAP), and plasma SARS-CoV-2 Nucleocapsid antigen (pN Ag) were measured by HD-X Simoa analyzer (Quanterix) and compared with neuropsychiatric symptoms, patient-reported quality-of-life measures, and standardized cognitive assessments. Neuroglial scores (pGFAP/pNfL) were calculated to estimate the relative contribution of astroglial and neuronal involvement.

Results: We enrolled a total of 64 study participants, including 9 hospitalized patients with COVID-19 encephalopathy (CE), 9 posthospitalization neuro-PASC (PNP) patients, 38 nonhospitalized neuro-PASC (NNP) patients, and 8 HC subjects. Patients with CE were older, had higher pNfL and pGFAP concentrations, and more frequent pN Ag detection than all neuro-PASC groups. PNP and NNP patients exhibited similar PASC symptoms, decreased quality-of-life measures, and cognitive dysfunction, and 1 of the 38 (2.6%) NNP patients had pN Ag detectable 3 weeks postsymptoms onset. Patients with neuro-PASC presenting with anxiety/depression had higher neuroglial scores, which were correlated with increased anxiety on quality-of-life measures.

Discussion: pNfL, pGFAP, and pN Ag measurements indicate neuronal dysfunction and systemic involvement in hospitalized COVID-19 patients with encephalopathy. Detection of SARS-CoV-2 N Ag in blood 3 weeks after symptoms onset in a nonhospitalized patient suggests that prolonged antigenic stimulation, or possibly latent infection, may occur. Anxiety was associated with evidence of astroglial activation in patients with neuro-PASC. These data shed new light on SARS-Cov-2 neuropathogenesis and demonstrate the value of plasma biomarkers across the COVID-19 disease spectrum.

Figure 1. Plasma Biomarkers of CNS Injury in Patients With COVID-19

Plasma neurofilament (pNfL) and plasma glial fibrillary acidic protein (pGFAP) concentration stratified by age in (A) patients hospitalized with Covid-19 encephalopathy (CE: younger than 50 years, n = 1, older than 50 years, n = 8) and (B and C) patients who experienced Covid-19 pneumonia and are now posthospitalization with neuro-PASC (PNP: younger than 50 years, n = 4, older than 50 years, n = 5), nonhospitalized neuro-PASC patients (NNP group: younger than 50 years, n = 20, older than 50 years, n = 18), and healthy control subjects (HC: younger than 50 years, n = 7, older than 50 years, n = 1). Both pNFL and pGFAP levels are significantly higher in CE older than 50 years than those in all other groups including those older than 50 years (Kruskal-Wallis test; pNfL: H = 16.23, p = 0.0003; pGFAP: H = 7.34, p = 0.02). pGFAP/pNfL ratio (D) represents neuroglial score, where higher scores indicate predominance of astrocytic activation and lower scores predominant neuroaxonal damage.

Figure 2. SARS-CoV-2 Nucleocapsid Protein (N Ag) in Plasma Samples of Patients With COVID-19

N Ag was detectable in 6 of the 64 (9.4%) plasma samples tested (CE = 5 of the 9 [55.6%], posthospitalization neuro-PASC patients = 0/9, nonhospitalized neuro-PASC patient = 1 of the 38 [2.6%], healthy controls = 0 of the 8).

Figure 3. Neuro-PASC Negatively Affects Quality Of Life and Cognition

Normalized and demographic-matched T score values for Patient-Reported Outcomes Measurement Information System (PROMIS-57; A) quality of life and NIH Toolbox (B) cognitive assessment for posthospitalized neuro-PASC patients (PNP) and nonhopitalized neuro-PASC patients (NNP). United States normative population T score mean/median of 50 (δ = 10) is indicated by a broken black line. Scores lower than 50 for cognition, processing speed, attention, executive function, and working memory indicate poor outcomes. Scores higher than 50 for fatigue, anxiety, depression, and sleep disturbance indicate poor outcomes. One-sample 2-tailed t test p values between patient group and normative population and between-group 2-tailed t test are provided in the table. *p ≤ 0.05.

Figure 4. Higher Neuroglial Score Correlates With Anxiety in Neuro-PASC Patients

Neuro-PASC patients (posthospitalization neuro-PASC patients and nonhospitalized neuro-PASC patients combined) presenting with anxiety and/or depression (A) in the Neuro–Covid-19 clinic showed higher neuroglial scores when compared with neuro-PASC patients who exhibited neither anxiety nor depression in both younger than 50-year age-group and older than50-year age-group (younger than 50 years: yes, n = 17; no, n = 7, p = 0.01, Hedges' g effect size = 1.37; older than 50 years: yes, n = 15; no n = 8, p = 0.02, Hedges' g effect size = 1.17; two-tailed T tests). Quantitative PROMIS-57 T scores for anxiety (B) but not depression (C) showed linear correlation with increasing glial activation predominance at the time of sample (anxiety T score: n = 11, R2 = 0.41, p = 0.03; depression T score: n = 11, R2 = 0.09, p = 0.36; two-tailed Pearson correlation). *p ≤ 0.05.