SARS-CoV-2 viral antigens may contribute to central nervous system immune responses without direct viral invasion of the CNS, new data suggest.

It is now known that patients with COVID-19 may develop neurologic symptoms but it is unclear why, as SARS-CoV-2 RNA is rarely detected in CSF, researchers say.

In a cross-sectional study of 44 patients with acute COVID-19 (23 with neurologic symptoms), researchers using a novel ‘ultrasensitive’ assay detected SARS-CoV-2 nucleocapsid antigen (N-Ag) in CSF in 89% of patients with available data, despite negative viral RNA test results in all patients.

“Our findings indicate that SARS-COV-2 viral antigens are associated with a CNS immune response without apparent viral invasion of the CNS,” the authors wrote.