The Brain Reacting to COVID-19: Analysis of the Cerebrospinal Fluid and Serum Proteome,Transcriptome and Inflammatory Proteins

Abstract

Patients with COVID-19 can have a variety of neurological symptoms, but the pathomechanism of CNS involvement in COVD-19 remains unclear. While routine cerebrospinal fluid (CSF) analyses in patients with neurological manifestations of COVID-19 generally show no or only mild inflammation, more detailed data on inflammatory mediators in the CSF of patients with COVID-19 are scarce. Here, we used mass spectrometry to study the proteome, Enzym-linkend immunoassays, semiquantitative cytokine arrays, autoantibody screening, and RNA profiling to study the neuroinflammation. We study the inflammatory response in paired CSF and serum samples of patients with COVID-19 (n=38). Patients with herpes simplex virus encephalitis (HSVE, n=10) and patients with non-inflammatory, non-neurodegenerative neurological diseases (n=28) served as controls. Proteomics on single protein level and subsequent pathway analysis showed similar yet strongly attenuated inflammatory changes in the CSF of COVID-19 patients compared to HSVE patients. CSF/serum indices of interleukin-6, interleukin-16 and CXCL10 together point at an origin from these inflammatory proteins from outside the central nervous system. When stratifying COVID-19 patients into those with and without bacterial superinfection as indicated by elevated procalcitonin levels, inflammatory markers were significantly higher in those with concomitant bacterial superinfection. RNA sequencing in the CSF revealed 101 linear RNAs comprising messenger RNAs, micro RNAs and t-RNA fragments being significantly differentially expressed in COVID-19 than in HSVE or controls. Our findings may explain the absence of signs of intrathecal inflammation upon routine CSF testing despite the presence of SARS-CoV2 infection-associated neurological symptoms. The relevance of blood-derived mediators of inflammation in the CSF for neurological post-COVID-19 symptoms deserves further investigation.

The central nervous system’s proteogenomic and spatial imprint upon systemic viral infections with SARS-CoV-2

“…However, we did not see a marked increase in T cell numbers or additional microglial populations as previous studies ( Supplementary Figure 3 c ) 8,14,87,88 probably due to our control group with also multi-organ failure, superinfection and to some degree neurodegenerative diseases similar to the COVID-19 groups ( Supplementary Table 1 ). The described IFN response in our study is probably not SARS-CoV-2-specific and not only seen in severe COVID-19 as similar alterations of neurons and oligodendrocytes were previously described in CNS viral infections caused by the West Nile virus (WNV) 31 and - in the CSF - by Herpes virus (HSV; Figure 3 ) 10 . Interestingly, during COVID-19 we found a tendency to reduced glutamatergic neurons (not significant in our testing) but we found a net reduction of OPALIN+ oligodendrocytes, a finding previously reported in demyelinating lesions and ‘normal appearing white matter’ in multiple sclerosis (MS) 89 .…”

“…This part of the study was approved by the local ethics committees at Charité (EA1/76/20). And these samples are also included in a separate CSF study 10 .…”

“…This hypothesis is based on the detection of viral RNA, while active replication of SARS-CoV-2 or intact viral particles have not yet been shown in the CNS 8,9 . Nevertheless, existing histological and molecular data implicate immune activation and inflammation within the CNS as well as dysregulation of CNS-specific cells primarily caused by indirect systemic effects 8,10 . Previous autopsy studies of the CNS from patients with severe COVID-19 show infiltration of macrophages, CD8+ T lymphocytes especially in the perivascular regions, and pronounced microglial activation [11][12][13][14] , however, without signs of viral encephalitis with lytic, infected cells.…”

Serum Neurofilament Light Chain in COVID-19 and the Influence of Renal Function

“…In summary, our data suggests that it is not COVID-19 itself, but rather the severity of COVID-19 respiratory disease requiring ICU treatment and concomitant renal dysfunction that leads to elevated sNfL levels, and both, sNfL and creatinine, are associated with poor clinical prognosis. Other studies on the correlation of Neuro lament light Chain levels and COVID- 19 All data is available by request to the corresponding author.…”

“…However, all of these studies did not consider factors in uencing sNfL levels, such as renal dysfunction, hypoxia or body mass index (14). The exact pathomechanisms leading to COVID-19 causing neurological symptoms are still speculative, but the consequences of critical illness and hypoxia, hypercoagulopathy, para-and post-infectious in ammation as well as the possible direct viral nerve infection may play a role (2,(15)(16)(17)(18)(19). In a post-mortem study, myositis-like histopathology was found in COVID-19 patients, indirectly suggesting presumed retrograde neuroaxonal injury from muscle pathology, which is more prevalent in COVID-19 ICU patients than previously thought before (20).…”