The speed with which a person’s immune system responds after coronavirus infection plays a crucial role in determining the severity of the disease, a study shows.
The Cambridge researchers studied 207 people who tested positive for Covid-19 over a three-month period and found that those without symptoms or mild cases mounted a robust immune response shortly after being 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 undercooked response to infection is characterized by inflammation of several organs, which occurs immediately after a person contracts the coronavirus.
Scientists say that abnormalities in the cells of the immune system may be behind the slow response to viral infection, as well as the body’s inflammatory response, and can contribute to serious illnesses and also “long covid”.
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The speed with which a person’s immune system responds after coronavirus infection plays a crucial role in determining the severity of the disease, a study shows (file)
Dr Paul Lyons, senior co-author of the study at the Cambridge Institute of Therapeutic Immunology and Infectious Diseases (CITIID), said: ‘Our evidence suggests that the journey to severe Covid-19 can be established immediately after infection, or the at the latest when they start showing symptoms.
‘This finding may have important implications for how the disease needs to be managed, as it suggests that we need to start treatment to stop the immune system causing damage very early, and perhaps even preventively in high-risk groups screened and diagnosed before symptoms develop. . ‘
There is no cure for Covid-19, but treatments have improved since its appearance in China in late 2019.
Cambridge University researchers 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 health professionals to patients requiring ventilation.
In the study, which has not yet been peer-reviewed, but is available as a pre-print on medRxiv, the team analyzed blood samples collected regularly over three months.
They compared the samples with those taken from 45 healthy people.
The researchers found evidence of a robust and early adaptive immune response in infected individuals whose disease was asymptomatic or mildly symptomatic.
An adaptive immune response occurs when the immune system identifies an infection and then produces T cells, B cells and antibodies specific to the virus to fight it.
Cambridge researchers studied 207 people tested positive for Covid-19 over a three-month period and found that those with no symptoms or a mild case generated a robust immune response shortly after being infected (file)
These people produced the 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 in these individuals of systemic inflammation that could damage several organs.
In patients who needed to be admitted to the hospital, the initial adaptive immune response was delayed and profound abnormalities in several subsets of leukocytes were present.
The researchers say this suggests that an abnormal inflammatory component of the immune response is present even at the time of diagnosis in individuals who progress to severe illness.
Professor Derek Hill of UCL, who was not involved in the study, said: ‘This article … finds that there are signatures on the first blood tests that are associated with the subsequent course of the disease, from having only mild illness to severe illness symptoms.
‘In addition, there is a suggestion of a sign in blood tests on those who can 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 that the authors identified are reliable predictors of the course of the diseases, and whether such information could be used to help make treatment decisions. ‘
The team also found that the main molecular signatures produced in response to inflammation were present in patients admitted to the hospital.
They say these signatures could be used to predict the severity of a patient’s illness, as well as correlate with their risk of death associated with Covid-19.
The study also provides clues about the biology underlying the cases of long Covid – where patients report having experienced symptoms of the disease, including fatigue, for several months after infection, even when the virus test is no longer positive.
The team found that profound changes in many types of immune cells often persisted for weeks or even months after SARS-CoV-2 infection, and these problems resolved in very different ways, 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 markedly abnormal or show only limited recovery, even after the systemic inflammation has resolved and patients have been discharged from the hospital.
Dr. Laura Bergamaschi, the study’s first author, said: “It is these populations of immune cells that still have abnormalities, even when everything else seems to have resolved, that may be important in the long COVID.
“For some types of cells, they may just take time to regenerate, but for others, including some types of T and B cells, it seems that something continues to boost their activity.
“The more we understand about this, the more likely we will be able to better treat patients whose lives continue to be damaged by the side effects of COVID-19.”