Aggregation‐Seeding Forms of α‐Synuclein Are Not Detected in Acute Coronavirus Disease 2019 Cerebrospinal Fluid

Author Roles

M.J.R. contributed to the conception and design, analyzed data, and drafted and revised the manuscript. K.M. and R.L. contributed to the conception and design and interpretation of data and critically revised the manuscript. J.L. contributed to the conception and design, performance of assay, and interpretation of data and critically revised the manuscript. M.P., C.S., T.W., and J.A.F. contributed to sample collection and interpretation of data and critically revised the manuscript. U.J.K. contributed to the conception and design and interpretation of data and critically revised the manuscript.

Coronavirus disease 2019 (COVID‐19) has raised concerns that viral infection by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) may trigger pathological transformations of neuronal proteins to cause a latent form of parkinsonism akin to encephalitis lethargica.1, 2 Virally mediated injury and inflammation could facilitate misfolding and aggregation of α‐synuclein (αSyn) through several plausible mechanisms. The virus may directly interact with αSyn, because SARS‐CoV‐2 proteins promote aggregation of αSyn into protease‐resistant forms and potential precursors to Lewy body pathology.3, 4 Acute infection could also alter proteostasis by interfering with protein degradation pathways, leading to toxic accumulation of αSyn. ⁵ Finally, viral infection can stimulate increased intracellular αSyn expression, which may predispose to aggregation and inclusion formation. ⁶

We asked whether acute COVID‐19 is associated with amyloidogenic, aggregation‐prone forms of αSyn in the cerebrospinal fluid (CSF), signature of pathogenic changes, and future risk for frank synucleinopathy. We performed a cross‐sectional study of CSF of hospitalized patients (n = 12) obtained up to 34 days after positive SARS‐CoV‐2 PCR. Specific variant information was not available, but the timing of infection spanned periods with dominant alpha, omicron original, and BA3 or BA4 omicron variants. We screened for aggregation‐prone αSyn forms by αSyn seed amplification assays (αSyn‐SAA, also known as RT‐QuIC or PMCA) performed by Amprion (San Diego, CA, USA) using methods previously described (see Supporting Information for complete methods and references). Aggregating forms of αSyn were not detected in any patients with acute COVID‐19 (0/12). We also tested COVID‐19‐negative neurological controls (n = 20) with a wide range of neurological pathologies, including autoimmune encephalitis or status epilepticus (n = 11), as proxies for central nervous system inflammation. Only 3/20 (15%) COVID‐19‐negative patients were αSyn‐SAA positive (see Supporting Information for patient characteristics).

We provide preliminary evidence that acute COVID‐19 is not associated with the presence of aggregates of misfolded αSyn in CSF, as detectable by αSyn‐SAA, which is diagnostic of Lewy body diseases and also frequently present in prodromal synucleinopathies. This provides some reassurance that acute COVID‐19 may not acutely trigger the αSyn aggregation that leads to the deposition or propagation of Lewy body disease, despite significant systemic inflammation and various neurological complications. We could not identify any predisposing or prodromal features among the αSyn‐SAA‐positive, COVID‐19‐negative controls, and this positive rate is comparable with false‐positive rates of other studies using healthy subjects or subjects with other neurodegenerative disorders. ⁷

However, there are important limitations to this work that should motivate careful follow‐up studies. We tested only a small number of patients from a single medical center, limited by availability of CSF obtained during COVID‐19 hospitalizations. We did not have information about the olfactory status in these patients. Evidence suggests that SARS‐CoV‐2 only rarely invades the central nervous system, but virally triggered αSyn pathology could also occur at peripheral sites, such as the enteric nervous system or olfactory mucosa. Although the negative αSyn‐SAA result in these acute and subacute periods is reassuring, this does not preclude that pathological αSyn may form only after some latency, as a consequence of postacute or chronic changes in immune modulation, proteostasis, endothelium or blood–brain barrier integrity, or oxidative stress.

Supporting information

Appendix S1. Supporting Information

Data Availability Statement

The data are presented in supplementary file and further details are available by the authors upon request.