The long-term impact of the SARS-CoV-2 virus on the immune system is widespread, according to researchers at the University of California, San Francisco, CellSight Technologies, and Kaiser Permanente South San Francisco Medical Center.
When 24 patients who had recovered from COVID-19 were given full-body PET scans, their insides lit up like a Christmas tree.
A radioactive drug called a "tracer" detected abnormal T-cell activity in the brainstem, spinal cord, bone marrow, nose, throat, some lymph nodes, heart, and tissue in the lungs and intestinal wall, compared with whole-body scans from earlier in the pandemic, Science Alert reports.
This widespread effect was evident in 18 participants with long-term symptoms of COVID-19 and six participants who fully recovered from the acute phase of COVID-19.
T-cell immune activation in some tissues, such as the spinal cord and intestinal wall, was higher in patients who reported long-term COVID symptoms compared to those who fully recovered. Participants with persistent respiratory problems also showed increased uptake of the PET tracer in the lungs and pulmonary artery walls.
However, even those who fully recovered from COVID-19 still showed persistent changes in T-cell activity in a number of organs compared to pre-pandemic controls, in some cases two and a half years after first contracting the virus.
"In some individuals, this activity may persist for years after the initial onset of COVID-19 and be associated with systemic changes in immune activation, as well as the presence of prolonged COVID symptoms," the UCSF researchers conclude.
"Together, these observations suggest that even clinically mild infection may have long-term consequences on tissue-based immune homeostasis and potentially result in an active viral reservoir in deeper tissues."
The findings are only correlative, but provide compelling evidence that long-term COVID is associated with the persistence of the SARS-CoV-2 virus in the body and abnormal immune activity.
It is worth noting that all but one study participant had received at least one COVID-19 vaccine before the PET scan.
Symptoms and consequences
Long-term Covid is currently defined by a series of unexplained symptoms that appear after infection with SARS-CoV-2, lasting for months or even years, without any other known cause.
Diagnosis is extremely difficult because there can be more than 200 symptoms, which often overlap with other illnesses, such as "brain fog," weakness after exertion, fatigue, memory loss, or diarrhea.
Research shows that patients may have long-term problems with their heart, brain, lungs, skin, kidneys, liver, spleen, intestines, thyroid, and ovaries.
One explanation for this widespread effect involves immune system activity. Scientists have found that biomarkers of inflammation and immune activation are often present in the blood of patients after the acute phase of a viral infection.
COVID autopsies also show evidence of SARS-CoV-2 throughout the body, including the colon, chest, muscles, nerves, reproductive tract, and eye. In some cases, remnants of the virus appeared in the brains of deceased patients 230 days after symptoms first appeared.
It can "wake up" other viruses
Some studies even suggest that infection with SARS-CoV-2 may "awaken" other dormant viruses in the body, such as the Epstein-Barr virus, which is associated with chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME).
CFS/ME has many of the same symptoms as long-term COVID, and some scientists suspect they may be the same. Brain scans have found that long-term brain changes in Covid parallel the effects of CFS/ME, and recently a landmark study confirmed that CFS/ME is “unequivocally biological” with multiple organ systems affected.
Today, it is increasingly accepted that long-term COVID has a neurological basis, and the recent discovery of T-cell abnormalities in the spinal cord and brainstem suggests that these hyperactive immune cells are “trafficked” into central nervous system tissues.
"Overall, these observations challenge the paradigm that COVID-19 is an acute, transient infection, based on recent observations in blood," the UCSF team concluded.
The findings need to be confirmed among larger groups, now that this new technique for mapping the long-term immune effects of COVID in the body is showing so much promise.
The study was published in Science Translational Medicine.
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