Daijiworld Media Network - Bengaluru
Bengaluru, Aug 12: The immune systems of people suffering from long Covid may remain engaged in a prolonged battle with remnants of the coronavirus, triggering persistent inflammation while becoming less effective at eliminating its source, according to new research by scientists at the University of California, San Francisco (UCSF).
The findings, released as a preprint on Monday ahead of peer review, identified extensive immune abnormalities in intestinal tissue from people with long Covid. Researchers found signs that some of the body's first-line immune defences remained activated months or even years after the initial infection, while processes responsible for recognising and destroying virus-containing cells appeared weakened.
The researchers, led by Michael Peluso and Timothy Henrich, described the pattern as an “uncoordinated immune response”, in which inflammatory activity continues even as mechanisms needed to eliminate its source are impaired.
However, the study does not establish that persistent virus is responsible for the immune abnormalities or for long Covid itself. Researchers said the findings could nevertheless help guide the search for new treatments.
Antiviral medicines alone have not demonstrated clear benefits in trials involving broadly defined long Covid. The researchers suggested that future treatment approaches may need to address both potential lingering virus and the immune system's ability to eliminate cells harbouring it.
Understanding what drives long Covid remains one of the major unanswered questions following the pandemic. Millions of people worldwide have experienced persistent symptoms after Covid-19, including fatigue, memory and concentration problems and worsening symptoms following physical activity.
Long Covid is also part of a broader and poorly understood group of chronic illnesses that can develop following infections. Researchers say understanding its underlying biology could therefore have implications beyond Covid-19.
For the study, the UCSF team examined lower-intestine tissue samples from 44 people with long Covid and 13 people who had fully recovered from Covid-19. The biopsies were collected a median of nearly two years after the participants' first known SARS-CoV-2 infection.
Researchers used several techniques to search for evidence of the virus and examine the activity of thousands of genes and different types of immune cells in the tissue.
Evidence of persistent SARS-CoV-2 was detected in intestinal tissue from 12 of the 44 people with long Covid, or 27 per cent, compared with one of the 13 participants who had recovered. The difference was not statistically significant.
The researchers cautioned that detecting viral genetic material does not prove that intact or infectious virus remains in the body.
However, both single-stranded and double-stranded viral RNA were detected in cells lining the intestine. Since these cells normally renew themselves within days, the finding could indicate ongoing viral activity or repeated exposure of intestinal cells to virus originating elsewhere in the body, the researchers said.
The immune abnormalities were considerably more pronounced in intestinal tissue than in blood samples, suggesting that blood tests alone may fail to capture important biological changes occurring inside tissues.
The findings provide another possible avenue for understanding long Covid, although further research and peer-reviewed studies will be needed to determine whether persistent viral material plays a causal role in the condition.