Long-term COVID-19 leads to abnormal immune-cell activity, study suggests

Neutrophil depolarization
Alioui Mohamed Elamine/iStock

People who have long Covid symptoms — those that persist after the initial SARS-CoV-2 infection — may show signs of abnormal immune-cell activation in multiple organs and tissues, as well as residual SARS-CoV-2 RNA in the gut more than 2 years after infection, a study suggests. A small study This week science translation medicine,

Researchers at the University of California, San Francisco, analyzed data from 24 people who underwent whole-body positron emission tomography (PET) imaging at time points ranging from 27 to 910 days (about two and a half years) after their initial COVID-19 illness. Eighteen patients had long COVID.

The team used a tracer during PET imaging that selectively tags activated T cells and found that some tissues from people with long Covid were rich in activated T cells, compared with people who had never been infected and did not have long Covid (controls before the pandemic).

Moreover, this T-cell activation was related to long-lasting Covid symptoms. For example, people who complained of persistent lung problems had stronger signs of T-cell immune activation in their lungs.

Viral RNA in intestinal tissue

In addition, since the intestine was one of the sites of activated T-cell enrichment, the scientists analysed colorectal biopsies from five patients with long Covid. SARS-CoV-2 RNA was detected in all five of these samples.

The authors wrote, “In this first human T cell activation PET imaging study of individuals following SARS-CoV-2 infection, we found evidence of persistent T cell activation in various tissues. In some individuals, this activity may persist for years after initial COVID-19 onset and may be associated with systemic changes in immune activation as well as the presence of virions.” [long COVID] symptoms.”

The authors concluded that, “Overall, these observations challenge the notion that COVID-19 is a transient acute infection, based on recent observations in blood.”

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