How quickly a person’s immune system responds after coronavirus infection plays a crucial role in determining the severity of the disease, a study shows.
Researchers in Cambridge studied 207 people who tested positive for Covid-19 over a three-month period and found that those without symptoms or mild cases had a robust immune response shortly after becoming infected.
But people with severe cases who needed hospitalization had an impaired immune response, which led to a delayed and weakened attempt to fight the virus.
This insufficient response to infection is characterized by inflammation of several organs, which occurs immediately after a person catches the coronavirus.
Scientists say that abnormalities in immune cells may be behind the poor response to viral infection as well as the body’s inflammatory response and may contribute to severe disease and also to “long covid”.
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How quickly a person’s immune system responds after coronavirus infection plays a crucial role in determining the severity of the disease, study shows (dossier)
Dr. Paul Lyons, lead co-author of the study at the Cambridge Institute for Therapeutic Immunology and Infectious Diseases (CITIID), said: “Our evidence suggests that the journey to severe Covid-19 can be established immediately after infection or around in which they begin to show symptoms.
“This finding could have major implications for how the disease should be managed, as it suggests that we need to start treatment to stop the immune system from causing damage very early and perhaps even preventively in high-risk groups examined and diagnosed before it occurs. symptoms. ‘
There is no cure for Covid-19, but treatments have improved since it appeared in China in late 2019.
Researchers at the University of Cambridge recruited a number of people who tested positive for the virus to see how the immune system’s response affected a person’s prognosis.
These individuals ranged from asymptomatic medical workers to patients requiring ventilation.
In the study, which has not yet been evaluated by colleagues but is available for pre-printing on medRxiv, the team looked at blood samples taken regularly over three months.
They compared the samples with those taken from 45 healthy people.
The researchers found evidence of an early and robust adaptive immune response in those infected individuals whose disease was asymptomatic or mildly symptomatic.
An adaptive immune response is when the immune system identifies an infection and then produces T cells, B cells and virus-specific antibodies to fight back.
Researchers in Cambridge studied 207 people who tested positive for Covid-19 over a three-month period and found that those without symptoms or a mild case had a robust immune response immediately after infection (dossier).
These people produced immune components in greater numbers than patients with more severe Covid-19 and in the first week of infection.
After that, the numbers quickly returned to normal.
There was no evidence of systemic inflammation in these individuals that could lead to damage to several organs.
In patients who had to be hospitalized, the early adaptive immune response was delayed and profound abnormalities were present in a number of white blood cell subgroups.
The researchers say that this suggests that an abnormal inflammatory component of the immune response is present even at the time of diagnosis in people progressing to severe diseases.
Professor Derek Hill of UCL, who was not involved in the study, said: “This paper … finds that there are signatures in early blood tests that are associated with the subsequent course of the disease, from having only a mild illness up to severe symptoms.
Moreover, there is an indication of a signal in the blood tests about those who could get long COVID.
“These are interesting findings, but it is important to note that a much larger study would be needed to determine whether the ‘signatures’ of the blood tests identified by the authors are reliable predictors, of course, of disease and whether such information could be used. to help make treatment decisions. ‘
The team also found that key molecular signatures produced in response to inflammation were present in hospitalized patients.
They say these signatures could potentially be used to predict a patient’s disease severity, as well as to correlate them with their risk of death associated with Covid-19.
The study also provides clues to the biology behind long Covid cases – in which patients report symptoms of the disease, including fatigue, for several months after infection, even when they are no longer positive for the virus.
The team found that profound changes in many immune cell types often persist for weeks or even months after SARS-CoV-2 infection, and these problems resolved very differently depending on the type of immune cell.
While some recover as systemic inflammation resolves, others recover even in the face of persistent systemic inflammation.
However, some cell populations remain significantly abnormal or show only limited recovery, even after systemic inflammation has resolved and patients have been discharged from the hospital.
Dr. Laura Bergamaschi, the study’s lead author, said: “These immune cell populations still show abnormalities even when everything else seems to have resolved on its own, which could be important in long-term COVID.
“For some cell types, it is possible for them to regenerate slowly, but for others, including some T and B cell types, it seems that something continues to drive their activity.
The more we understand about this, the more likely we are to be able to better treat patients whose lives continue to be affected by the side effects of COVID-19.