Long Covid Linked to Overactive Immune System
/By Pat Anson, PNN Editor
People who develop long-haul COVID – even when the initial infection was mild or moderate – have a sustained inflammatory response that appears to be the result of an overactive immune system, according to Australian researchers.
Long covid is a poorly understood disorder characterized by body pain, fatigue, cognitive impairment and difficulty sleeping. About a third of people infected with coronavirus develop symptoms that can last for many months.
“This study provides the strongest evidence to date for a clear biological basis for the clinically apparent syndrome of long COVID,” Professor Anthony Kelleher, Director of the Kirby Institute at UNSW Sydney, said in a press release.
Kelleher and his colleagues analyzed blood samples from 62 patients enrolled in the ADAPT study at St. Vincent’s Hospital, who were diagnosed with COVID-19 between April and July 2020 – before any vaccines were available. The blood samples were collected at three, four and eight months following initial infection, and compared to control groups.
Their study, recently published in the journal Nature Immunology, identified biomarkers of a sustained inflammatory response in long covid patients – suggesting their immune systems were activated by the virus, but then failed to turn off.
“What we’re seeing with long COVID is that even when the virus has completely left the body, the immune system remains switched on. If you measure the same thing after a standard cough or cold, which we did in this study through one of our control groups, this signal is not there. It’s unique to sufferers of long COVID,” said Professor Gail Matthews, who co-leads ADAPT and is Program Head of Vaccine and Therapeutic Research at the Kirby Institute.
“Simply put, when we look carefully at the immune system in people who have had COVID-19 infection, and particularly at those with long COVID, it looks different to what we would expect in healthy individuals. This tells us that there might be something quite unique in the pathophysiology of this disease.”
The study findings are welcome news to covid long-hauler Rick Walters, who contracted COVID in August 2020 and is part of the ADAPT study. Walters continues to have symptoms 17 months later.
“I’m glad that the study has confirmed that long COVID is a valid result of COVID-19 infection and just not something in my head. At first, I thought I would get better, but it became apparent that the damage to my lung was permanent, and I became quite anxious,” he said. “I have had some difficulties adjusting to my current health. COVID should not be taken lightly. I am gradually learning to live with the results.”
“One of the most surprising aspects of our analysis is that people don’t need to have had severe COVID to experience these ongoing immunological changes,” says Dr. Chansavath Phetsouphanh, a senior research associate at the Kirby Institute. “We found that there is a significant and sustained inflammation that indicates prolonged activation of the immune system response detectable for at least eight months following initial infection.”
Researchers hope that a better understanding of how the immune system reacts to the virus will lead to better treatment and management of long covid. There is no data yet to reflect whether variants like Omicron also cause long covid.
Previous studies of long covid have found similarities with autoimmune conditions such as lupus and myalgic encephalomyelitis, also known as chronic fatigue syndrome (ME/CFS).
Being fully vaccinated against COVID-19 cuts the risk of developing long covid in half, according to a 2021 study. Researchers at King’s College London looked at data from a mobile app used by millions of people in the UK and found that those who received two doses of the Moderna, Pfizer or AstraZeneca vaccines had significantly lower risk of a “breakthrough” infection that turns into long covid.
