March 8, 2024 – Scientists on the University of California, San Francisco have found that remnants of the COVID-19 virus can remain within the blood and tissues for greater than a 12 months after an individual was first infected.
In their research on long COVID, scientists found COVID antigens within the blood as much as 14 months after infection and in tissue samples greater than 2 years after infection.
“These two studies provide some of the strongest evidence yet that COVID antigens can persist in some people even though we assume they have normal immune responses,” said Michael Peluso, MD, an infectious disease researcher on the UCSF School of Medicine Medicine, who led each studies, said in a Opinion.
Scientists don't know what causes long COVID, wherein disease symptoms persist for months or years after recovery. The commonest symptoms are extreme fatigue, shortness of breath, lack of smell and muscle pain.
The UCSF research team examined blood samples from 171 infected people and located that the COVID “spike” protein was present in some people for as much as 14 months after infection. The antigens were found more often in individuals who were hospitalized with COVID or who reported being very sick but weren't hospitalized.
Next, the researchers examined UCSF's Long COVID tissue bank, which comprises samples donated by patients with and without Long COVID.
They found bits of viral RNA within the tissue for as much as two years after people were infected, but there was no evidence of reinfection. These virus fragments were present in the connective tissue where immune cells are positioned, suggesting that the fragments caused an immune system attack, based on the researchers.
The UCSF team is conducting clinical trials to see if monoclonal antibodies or antiviral drugs can clear the virus.
The results were presented this week in Denver Conference on Retroviruses and Opportunistic Infections.