SARS-CoV-2 infection directly alters brain’s essential vasculature, autopsies reveal
An infection with SARS-CoV-2, which causes COVID-19, is known to have some effects on the human brain leading to short and long-term neurological symptoms. New research by scientists at the Center of Immunity and Infection at Lille (CIIL), France, is the first to highlight molecular markers of inflammation of an essential component of the blood-brain barrier (BBB), through post-mortem analyses – in short, the novel coronavirus was shown to directly damage cells in the brain.
The research at CIIL homed in on a particular type of brain cell known as cerebral vascular endothelial cells. Part of the BBB, these cells form a protective wall that helps keep foreign or toxic molecules out of the brain.
Neuroscientist Jan Wenzel and colleagues found increased numbers of dead cells in the brain tissue from deceased COVID-19 patients compared to healthier controls. The scientists write to explain that infection with SaRS-CoV-2 caused the death of endothelial cells in the brain, resulting in the appearance of “ghost vessels” in the brain (empty tubes with no endothelial cells); as a result, the endothelial cells were unable to perform their function in the BBB.
The scientists also demonstrated exactly how the SARS-CoV-2 virus could kill these endothelial cells through cell and animal experiments: it is hypothesised that the consequence of this damage is decreased blood flow to brain regions, leading to cognitive problems or heightened risk of neurodegenerative disease.
“… we think that the direct infection of brain endothelial cells by SARS-CoV-2 leads to the expression of its main protease which cleaves an essential protein necessary for the survival of brain endothelial cells,” Wenzel said. “Our finding might explain at least partially neurological symptoms that not only appear during the acute but also long-term phase of COVID-19 including the increased risk for getting stroke or epileptic seizures and long COVID.”
Several researchers have recently warned of increased rates of neurological diseases such as Parkinson’s in the future due to the long-term effects of COVID-19. Australian researcher Zoe Hyde said the new findings affirm the potential of COVID-19 to cause damage to the brain, and that this could lead to greater rates of [vascular] dementia later.
Other researchers are more cautious about inferring long-term neurological problems from this study. Geriatrician Kate Gregorevic argued that the new findings offer no insight into whether a mild case of COVID-19 affects a person’s future dementia risk.
“The study referenced describes a series of brain autopsies done on people who died of COVID, often of hypoxia, for most after weeks on a ventilator – it cannot be extrapolated to people with mild COVID,” Gregorevic pointed out.
However, the research optimistically indicates the damage to the endothelial cells could be reversible.
Wenzel has speculated that vaccination could reduce the damage the virus causes to the BBB, “As far as we know vaccination protects against the vascular damage since the immune system acts against the virus in our blood, from where endothelial cells are infected.”
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