Earlier this year, leading researchers discussed what we know and don’t know about COVID-19 and the brain. Since then, new discoveries have emerged about SARS-CoV-2 and the nervous system. This includes results from autopsy studies that showed the presence of the virus throughout the body and brain.
How do respiratory pathogens like SARS-CoV-2 disrupt the nervous system? That was a question researchers posed in January and is still being asked almost a year later. increase.
At the time, Avindra Nath, M.D., Ph.D., of the National Institute of Neurological Disorders and Stroke, noted that the neurological complications of COVID are varied and can be long-lasting. “They are primarily immune-mediated, with brain endothelial cells being the primary target,” he said. MedPage Today.
Studies throughout the years have supported this view. In July, an autopsy study of nine COVID patients showed leakage of serum proteins into the brain parenchyma and vascular damage with widespread endothelial cell activation. No virus was detected in the brain.
But in December, autopsy reports from 44 people who died of COVID-19 in the first year of the pandemic found that the SARS-CoV-2 virus had spread throughout the body, including the brain, and persisted in tissues for months. showed.
Nevertheless, there was little evidence of inflammation or direct viral cytopathology beyond the airways, said Daniel Chertow, M.D., M.P.H., and coauthors of the NIH Clinical Center and National Institute of Allergy and Infectious Diseases. , Nature.
“A total of 44 necropsies were performed, 11 of which allowed for detailed evaluation of the brain,” Chertow said. MedPage Today“In most individuals we have had brains [samples], found evidence of viral RNA and protein in multiple regions sampled. ”
“And in one of those patients, using a modified Vero cell line that expresses the human ACE2 and TMPRSS2 receptors, we were able to actually culture the virus from the brain,” he continued. I was. “So we were able to show not only the presence of the viral components (RNA and protein), but also a live, replication-competent virus.”
Several factors set this autopsy study apart, Chertow noted. The postmortem interval was short, with a median of his 22 hours, he said.
“Additionally, at autopsy, the brain tissue was freshly dissected,” he added. “We collected tissue from 10 different regions of the brain and from each of those regions, we preserved the tissue in different ways appropriate for the kind of downstream analysis we were doing.”
Chertow warned that the findings may not be generalizable. “Not everyone in our cohort had received the vaccine because the study was done in the first year of the pandemic, before a vaccine was available,” he said. They were elderly and had significant comorbidities.” The cohort included predominantly severe and ultimately fatal COVID cases, with outcomes in young, healthy, or vaccinated individuals. may not apply to
Despite its limitations, this study showed that SARS-CoV-2 can spread to cells and tissues throughout the body and brain, but important questions remain open.
“This is a meticulously conducted and detailed study that shows that SARS-CoV-2 infection is indeed systemic and involves many organ systems, including the brain,” said St. Louis. Ziyad Al-Aly, M.D., of the University of Washington observed. I am involved in research.
“What the study does not show is a clear mechanistic explanation for the presence of inflammation, cellular pathology, or neurological complications of SARS-CoV-2 infection,” said Al-Aly. MedPage Today.
“More needs to be done to understand the mechanisms underlying the nerve damage seen so vividly in COVID-19 patients during both the acute and long-term stages of the disease,” he added. rice field.
Also contributing to our knowledge of COVID and the brain in 2022 was a case report of a 27-year-old epilepsy surgery patient recovering from COVID without respiratory distress.
Extracellular vesicles isolated from her brain biopsy tissue showed the presence of viral nucleocapsid proteins associated with endothelial cell activation, fibrinogen leakage, and immune cell infiltration. neurology.
“We never found a virus,” Nath said. MedPage Today“We found viral proteins, but not RNA.”
Few researchers have discovered the virus, Nath noted. And even if they do find it, “they’re not finding overwhelming amounts of the virus in the brain,” he noted. “They find it in very small amounts.”
“The question is how important it is,” he added. “Is that what drives the condition, or is it just sitting there? It’s not yet understood.”
autopsy studies in Nature was funded and supported by the NIH Clinical Center, the National Cancer Institute, the National Dental and Craniofacial Institute, and the National Institute of Allergy and Infectious Diseases. Chetow and co-authors report no competing interests.
case report in neurology It was supported by the National Institute of Neurological Disorders and Stroke. Nath and co-authors had no relevant disclosures.
Source reference: Stein SR, et al “SARS-CoV-2 infection and persistence in humans and brains at autopsy” Nature 2022; DOI: 10.1038/s41586-022-05542-y.
Source: DeMarino C, et al “Detection of SARS-CoV-2 nucleocapsid and microvascular disease in the Brain: A case report” Neurology 2022; DOI: 10.1212/WNL.0000000000201682.