When researchers examined proteins in the blood, they discovered a group of chemicals linked to inflammation that were only detectable in a small subgroup of patients with extended COVID and were not present in those who recovered from their condition. Today, the scientists wrote a paper for the journal Nature Communications outlining their findings.
About two-thirds of the 55 patients with extended COVID exhibited chronically elevated levels of certain inflamation- related markers. Additionally, the researchers examined blood samples from 25 COVID-positive individuals who recovered and from 25 healthy participants. People lacking lengthy COVID did not exhibit the same blood inflammatory symptoms.
The patient volunteers in the new analysis are part of a larger, ongoing study based at Fred Hutch, the Seattle COVID Cohort Study, which is led by Julie McElrath, M.D., Ph.D., Senior Vice President and Director of Fred Hutch’s Vaccine and Infectious Disease Division, and Julie Czartoski, ARNP, Research Clinician at the Hutch.
Scientists have seen previous links between inflammation and long COVID , but the new study is the first to trace the persistence of these inflammatory markers over time in the same patients.
There’s an obvious implication to these findings, said Troy Torgerson, M.D., Ph.D., Director of Experimental Immunology at the Allen Institute for Immunology, a division of the Allen Institute: 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.
“The big question was, can we define which long COVID patients have persistent inflammation versus those that don’t? That would be useful in terms of clinical trial planning and in terms of helping clinicians figure out targeted treatments for their patients,” said Torgerson, who led the Nature Communications publication along with McElrath, Aarthi Talla, Senior Bioinformatician at the Allen Institute for Immunology, Suhas Vasaikar, Ph.D., former Senior Bioinformatics Scientist (now a Principal Scientist at Seagen), and Tom Bumol, Ph.D., former Executive Vice President and Director.
But the team soon realized that even among those who didn’t get super sick, not everyone recovered. In their initial work in 2020 tracing the details of immune responses in 18 COVID patients, the scientists found a handful whose symptoms persisted, early examples of what would eventually be termed long-haul COVID, or just long COVID.
In those early days of the study, the scientists saw that certain immune responses — namely inflammation — were consistently high in these few patients with long COVID. In the patients that 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.
So the team 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.
“The ultimate goal is to treat patients,” Talla said. “Although we call everything long COVID, what’s come out of this work shows us that we might not be able to give everyone the same kinds of therapies and we shouldn’t put everyone into one group for treatment purposes.”