A study suggests why some develop new medical conditions after COVID-19, while not investigating the link between persistent viral RNA and vaccination status.
A new study suggests why some people who get COVID-19 never return to normal and instead experience new medical conditions like cardiovascular disease, clotting dysfunction, activation of latent viruses, diabetes mellitus, or what’s known as “long COVID” after SARS-CoV-2 infection.
In a recent preprint study published on medRxiv, researchers conducted the first positron emission tomography (PET) imaging study of T cell activation in individuals who previously recovered from COVID-19 and found that SARS-CoV-2 infection may result in persistent T cell activation in a variety of body tissues for years following initial symptoms.
Even in clinically mild cases of COVID-19, this phenomenon could explain the systemic changes observed in the immune system and in those with long COVID symptoms.
However, most of the participants were vaccinated and the study didn’t investigate the link between the existence of viral RNA and vaccination.
SARS-CoV-2 RNA Found in Study Participants
To carry out the study, researchers conducted whole-body PET scans of 24 participants who were previously infected with SARS-CoV-2 and recovered from acute infection at time points ranging from 27 to 910 days following COVID-19 symptom onset.
A PET scan is an imaging test that uses a radioactive drug called a tracer to assess the metabolic or biochemical function of tissues and organs and can reveal both normal and abnormal metabolic activity. The tracer is usually injected into the hand or vein in the arm and collects in areas of the body with higher levels of metabolic or biochemical activity, which can reveal the location of the disease.
Using a novel radiopharmaceutical agent that detects specific molecules associated with a type of white blood cell called T lymphocytes, researchers found uptake of the tracer was significantly higher in post-acute COVID-19 participants compared to pre-pandemic controls in the brain stem, spinal cord, bone marrow, nasopharyngeal and hilar lymphoid tissue, cardiopulmonary tissues, and gut wall. Among males and females, male participants tended to have higher uptake in the pharyngeal tonsils, rectal wall, and hilar lymphoid tissue compared to female participants.
Researchers specifically identified cellular SARS-CoV-2 RNA in the gut tissue of all participants with long COVID symptoms who underwent biopsy—in the absence of reinfection—ranging from 158 to 676 days following initial COVID-19 illness, suggesting that tissue viral persistence could be associated with long-term immunological concerns. Although the uptake of the tracer in some tissues appeared to decline with time, the levels still remained elevated compared to the control group of healthy pre-pandemic volunteers.
“These data significantly extend prior observations of a durable and dysfunctional cellular immune response to SARS-CoV-2 and suggest that SARS-CoV-2 infection could result in a new immunologic steady state in the years following COVID-19,” the researchers wrote….