Overactive inflammatory response could be at the root of long Covid: Study

New Delhi: An overactive inflammatory response could be at the root of many long Covid cases, according to new research.

A set of molecules associated with inflammation was found in the blood proteins of only a subset of patients with long COVID and not those recovered from the disease, said scientists from the Allen Institute and Fred Hutchinson Cancer Center, Washington, US, in the research.

Out of 55 patients with long COVID, about two-thirds were found to have persistently high levels of certain signals of inflammation.

Further, looking at blood samples from 25 people who had had COVID but recovered, and from 25 volunteers who had never had COVID to their knowledge, the scientists found that those without long COVID did not show the same signs of inflammation in their blood.

The researchers have published their findings in the journal Nature Communications.

"There's an obvious implication to these findings. Certain kinds of anti-inflammatory drugs might alleviate symptoms for some long COVID patients.

"But physicians need a way of telling which long COVID patients might benefit from which treatment - a form of precision medicine for a disease that so far remains maddeningly mysterious," said Troy Torgerson, Director of Experimental Immunology at the Allen Institute.

"The big question was, can we define which long COVID patients have persistent inflammation versus those that don't?" said Torgerson.

Specifically, the blood markers uncovered in this subset of patients with "inflammatory long COVID", pointed to a flavour of inflammation similar to that seen in autoimmune diseases like rheumatoid arthritis, the scientists said.

While this kind of inflammation can be treated with an existing class of drugs called JAK inhibitors in the case of rheumatoid arthritis, these drugs have not yet been tested for long COVID.

The scientists said they also hope to narrow down their molecular signature of "inflammatory long COVID" to a few markers that could be used in the clinic to sort this subset of long COVID patients out from the rest.

The patient volunteers are part of a larger, ongoing study based at Fred Hutch, the Seattle COVID Cohort Study, launched in the spring of 2020 and originally designed to follow immune responses over time in patients with mild or moderate COVID.

Tracing immune responses in 18 COVID patients at that time, the scientists found a handful whose symptoms persisted, early examples of what would eventually be termed long COVID.

The scientists saw that certain immune responses, namely inflammation, were consistently high in these few patients with long COVID.

In those who got sick and then recovered fully, inflammation levels went up as their bodies fought off the illness, and then went back down as they got better. In those with long COVID, the levels never went back down.

The team, thus, decided to expand their study to look at more patients with long COVID, focusing on a panel of 1500 proteins circulating in the blood.

These assays revealed different molecular "buckets" of long COVID, namely inflammatory and non-inflammatory long COVID.

Understanding the molecular roots of the disease, or subsets of the disease, will help guide clinical trial design and ultimately treatment decisions, the scientists said.