Allison Guy had a great start to 2021. Her health was the best it had ever been. She loved her job and the people she worked with as a communications manager for a non-profit conservation organization. She was able to get up early in the morning to work on creative projects. Things looked “very, very good,” she says, until she got Covid-19.
While the first infection wasn’t fun, what followed was worse. Four weeks later, when Guy had recovered enough to return to work full-time, she awoke one day with an overwhelming fatigue that would never go away. It was accompanied by a loss of mental acuity, part of a series of sometimes hard-to-pinpoint symptoms often referred to as Covid-19 “brain fog,” a generic term for sluggish or blurry thinking. “I spent most of 2021 making decisions like, is this the day I’m going to shower, or am I going upstairs to microwave a frozen dinner for myself?” Guy remembers. The high-level writing required for her work was out of the question. Living with those symptoms was, in her words, “hell on earth.”
Many of these hard-to-define Covid-19 symptoms can persist over time – weeks, months, years. Now, new research in the journal Cell sheds some light on the biological mechanisms of how Covid-19 affects the brain. Led by researchers Michelle Monje and Akiko Iwasaki, of Stanford and Yale Universities respectively, scientists determined that in mice with mild Covid-19 infections, the virus disrupted the normal activity of several brain cell populations and left signs of inflammation. They believe these findings could help explain some of the cognitive disruptions experienced by Covid-19 survivors and provide potential pathways for therapies.
For the past 20 years, Monje, a neuro-oncologist, has been trying to understand the neurobiology behind chemotherapy-induced cognitive symptoms — otherwise known as “chemo fog.” As Covid-19 emerged as a major immune-activating virus, she was concerned about the potential for similar disruption. “Very quickly, when reports of cognitive impairment came out, it was clear that it was a very similar syndrome,” she says. “The same symptoms of impaired attention, memory, information processing speed, dis-executive function — it’s really clinically exactly like the ‘chemo fog’ that people were experiencing and that we had studied.”
In September 2020, Monje contacted Iwasaki, an immunologist. Her group had already established a mouse model of Covid-19, thanks to their Biosafety Level 3 clearance to work with the virus. A mouse model was designed as a good substitute for a human, and this experiment was designed to mimic the experience of a person with a mild Covid-19 infection. Using a viral vector, Iwasaki’s group introduced the human ACE2 receptor into cells in the trachea and lungs of the mice. This receptor is the entry point for the Covid-causing virus, allowing it to bind to the cell. Then they injected a bit of virus into the mice’s noses to cause an infection, controlling the amount and release so that the virus was confined to the respiratory system. In the mice, this infection cleared up within a week and they did not lose weight.
Coupled with biosafety regulations and the challenges of cooperation between countries, the safety measures required by the pandemic created some interesting work constraints. Because most of the virus-related work had to be done in Iwasaki’s lab, Yale scientists took advantage of the overnight transmission to fly samples across the country to Monje’s Stanford lab, where they could be analyzed. Sometimes they had to film experiments with a GoPro camera to make sure everyone could see the same thing. “We made it work,” Monje says.
This post The secrets of Covid ‘Brain Fog’ are starting to disappear
was original published at “https://www.wired.com/story/the-secrets-of-covid-brain-fog-are-starting-to-lift/”