The immune-inflammatory response to COVID-19 may not be the underlying cause of prolonged COVID-19

A study led by the University of Bristol found that the long coronavirus, which affects about two million people in the UK, is not caused by an immune-inflammatory response to COVID-19. New data show that immune activation can persist for months after COVID-19.

In this new study, published in e-life today [4 July]researchers wanted to examine whether sustained immune activation and an ongoing inflammatory response might be the underlying cause of long-lasting Covid.

To investigate this, the Bristol team tested immune responses from blood samples from 63 hospitalized patients with mild, moderate, or severe COVID-19 before the start of the pandemic and the availability of a vaccine. were collected and analyzed. The team then tested the patients’ immune responses at three, eight, and 12 months after admission. Of these patients, 79% (82%, 75%, and 86% in mild, moderate, and severe patients, respectively) reported at least one ongoing symptom, the most common being shortness of breath and excessive breathlessness. I was tired.

Long Covid occurs in 1 in 10 cases of COVID-19, and its cause is still unknown. Several theories have been put forward, either that an inflammatory immune response to the virus still in our bodies triggers an overactive immune system, or that the human cytomegalovirus (CMV) ) and Epstein-Barr virus (EBV) are reactivated. ). ”

Laura Livino, PhD, Senior Lecturer, Bristol School of Cellular and Molecular Medicine, lead author of the study

The research team found that the immune response in severely symptomatic patients showed severe dysfunction at 3 months of age. T cells These profiles indicate that inflammation can persist for months even after recovery from the virus. Encouragingly, these patients’ inflammation, even in severe cases, resolved in time. At 12 months, both the immune profile and inflammation levels of critically ill patients were similar to those of mild and moderate patients.

Severe COVID-19 patients were found to have more long-lasting COVID-19 symptoms than mild and moderate patients. However, further analysis by the research team showed that, after adjusting for age, sex, and disease severity, there was no direct correlation between long-term COVID-19 symptoms and immune-inflammatory responses for the markers measured in any patient. was found to be unrelated.

Importantly, although there was no rapid increase in SARS-CoV-2-targeting immune cells at 3 months, persistent and dormant cytomegalovirus (CMV)-targeting T cells , is a common virus that is usually harmless but can remain in the body for life. Those infected with it showed an increase in low levels. This suggests that the prolonged T-cell activation observed after 3 months in critically ill patients may not be caused by SARS-CoV-2, but by ‘bystander-driven’, i.e. cytokines. indicates that there is

Dr. Libino added, “Our results suggest that prolonged immune activation and prolonged COVID-19 may be independently correlated with severe COVID-19. Where possible, large-scale studies involving a larger number of patients, including both vaccinated and unvaccinated COVID-19 patients, have been suggested. We need to do more research,” he added. , and measure a wider range of markers and cytokines.

“Understanding whether inflammation and immune activation are associated with prolonged COVID-19, targeting these factors could be a useful treatment for this debilitating condition. You will be able to understand whether

This research was supported by the Elizabeth Blackwell Institute (EBI) with funding from Bristol University alumni and friends, the Southmead Hospital Charity.