Patients with long COVID exhibited markers of myeloid inflammation

A study published in Nature Immunology profiled 368 plasma proteins in patients with long COVID, identifying multiple inflammatory plasma proteins associated with disease symptoms.

Study participants were hospitalized for acute COVID-19 — varying in severity based on the WHO progression scores — three or more months before their plasma samples were collected. Among the 657 participants, 426 experienced one or more long COVID symptoms.

After identifying the patients with long COVID, the investigators separated the participants into groups based on their long COVID symptoms, including the following:

• Cardiorespiratory symptoms
• Fatigue
• Affective symptoms, anxiety, or depression
• Gastrointestinal symptoms
• Cognitive impairment

The data revealed that women were 14% more likely to experience cardiorespiratory symptoms than men. Additionally, they were 22% and 13% more likely to experience fatigue and gastrointestinal symptoms, respectively. The risk of cognitive impairment was only slightly more likely among women, with a 3% greater risk.

“To study the association of peripheral inflammation with symptoms, we analyzed cross-sectional data collected approximately six months after hospitalizations. We measured 368 immune mediators from plasma collected contemporaneously with symptom data,” noted the researchers in the publication.

An analysis of the plasma proteins revealed that all long COVID symptoms were linked to myeloid inflammation mediators.

Beyond a general increase in inflammatory markers, the researchers also found markers specific to certain subtypes. For example, IL-1R2, MATN2, and COLEC12 are associated with cardiorespiratory symptoms, fatigue, and anxiety. Additionally, MATN2, CSF3, and C1QA were related to gastrointestinal symptoms.  C1QA was also associated with cognitive impairment.

“This work provides strong evidence that long COVID is caused by post-viral inflammation but shows layers of complexity. We hope that our work opens the way to the development of specific tests and treatments for the various types of long COVID and believe that a ‘one size fits all’ approach to treatment may not work,” noted Peter Openshaw from Imperial’s National Heart & Lung Institute and the lead investigator, in an interview with Imperial News. “COVID-19 will continue to have far reaching effects long after the initial infection has passed, impacting many lives. Understanding what’s happening in the body, and how the immune system responds, is key to helping those affected.”