Patients suffering from long Covid have distinct and measurable immunological changes in their blood, according to research which could point to a better understanding of the condition and possible cures.
By analysing the blood of 650 patients who had been in hospital with Covid, researchers found that those with ongoing symptoms had specific patterns of inflammation.
The research, published in the journal Nature Immunology, adds to similar findings in other patient groups and is among the most comprehensive investigations of the biology of long Covid, which is estimated to affect about two million Britons.
Professor Peter Openshaw, a lung immunologist at Imperial College London, said that his team’s “deep phenotyping” should be a comfort for those whose lives are still affected.
“A lot of people wonder if the seriousness of their condition is being doubted and questioned,” he said. “This adds to the evidence that there is a real biological basis, and that it’s based in the inflammatory response to the virus or the after-effects, which for various reasons has persisted in different individuals.”
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While it was possible the inflammatory markers were a consequence of long Covid rather than a cause, Openshaw said that it was logical to assume they could be behind symptoms including breathlessness and “brain fog”. “It makes biological sense that these types of inflammation would be associated with these different types of symptom,” he said.
This means that existing treatments to modulate the immune system might have an effect with long Covid. Openshaw and his colleagues called for big trials to investigate.
It is hard to say how the study would translate to the general population because it was carried out only on people who went to hospital with Covid. However, the researchers said it was likely they had found markers that would also be common to people who contract long Covid after milder infections.
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The findings also show the complexity of the condition, with the markers spanning the breadth of the immune system and different symptoms associated with different patterns.
Openshaw said that this was probably inevitable, suggesting that long Covid is many things. “It genuinely represents clinical reality, which is that not everyone arrives at the same endpoint by the same pathway. Things are complicated,” he said. Openshaw and his colleagues said there could be many triggers for the condition including new Covid infection, reactivation of other latent viruses and autoimmunity.
However, Chris Brightling, professor in respiratory medicine at the University of Leicester and an author of the study, said that the complexity was now more obviously tractable. He said: “We’re getting to a point where the number of distinct pathways are not that many. We’re talking about tens of pathways.
“What we’re actually finding is there’s a number of common mechanisms that have been identified in a number of studies … This adds weight to the evidence already out there.”
Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh, who was not involved in the research, said the work was an argument for getting on with drug trials. “These data should usher in a series of clinical trials for treatment of long-Covid,” she said. “As we already have several licensed drugs that target some of these pathways, the trials could start quite quickly.”
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The work, she said, may also be relevant for other less well understood post-viral syndromes, which are believed to be behind some cases of Myalgic encephalomyelitis, or chronic fatigue syndrome.
Brightling said there was hope amid the despair about the millions still suffering from the pandemic. He said: “This was a condition we were only able to properly identify as the pandemic began … In the relatively short space of time since we have a much better understanding of what the drivers are, what the potential targets are, and are just beginning to move into treatment trials.
“There’s room for hope. But clearly if you’re someone struggling with long Covid symptoms you want that to be as fast as possible. We are really trying very hard to do that.”
