Researchers have detected molecular traces of the coronavirus in blood samples from patients experiencing long Covid, marking what could become the first quantifiable indicator for the largely unexplained condition.
The latest findings demonstrate possible evidence that the virus might linger in bodily tissues well beyond the initial infection period, which could illuminate why symptoms persist for months or years afterwards.
Extreme fatigue is one of the symptoms of long Covid
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Additionally, certain indicators persist after the initial virus, such as loss of smell, insomnia, depression, headaches, rashes, and chest pain.
As a research subject, long Covid has long plagued scientists due to its large number of symptoms, which often overlap with other diagnoses.
However, the latest findings on the matter could offer a key to the next stage of study, if confirmed by other researchers.
Scientists have identified protein remnants from the Covid virus hidden inside tiny cellular packages in the blood of long Covid patients, offering the first potential measurable biomarker for the condition.
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The breakthrough was borne out of collaborative work between the Translational Genomics Research Institute at City of Hope and the Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center.
The investigation assessed blood samples from 14 individuals with long Covid across 12 weeks of aerobic exercise training, yielding 56 samples for analysis.
The team uncovered 65 separate protein fragments originating from the virus, dubbed SARS-CoV-2, within extracellular vesicles (tiny, naturally occurring packages that help cells share proteins, metabolites, and other materials).
These fragments were derived from the virus' Pp1ab protein, an enzyme essential for viral replication and particle production.
The team called on other researchers to conduct further investigation
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According to the study's lead author, Dr Asghar Abbasi, this particular protein exists only in cells burdened with SARS-CoV-2 and cannot be found in uninfected human cells.
"We thought that maybe if the virus is circulating or moving in the body, we should try to see if extracellular vesicles are carrying those viral fragments," Dr Abbasi explained.
Still, the mechanism through which the virus reaches tissues that lack obvious entry routes, such as the brain, continues to baffle researchers.
Nevertheless, molecular markers proved elusive and variable throughout the research, with co-senior author Dr Patrick Pirrotte adding: "While promising, the molecular signal of the viral peptides within the study samples was observed to be subtle and not consistently detected at every blood collection time point."
Critical uncertainties remain regarding whether these fragments signal active viral activity or merely cellular debris. Additionally, the absence of other substantial viral proteins typically associated with replication raises questions about the fragments' origins.
"We haven't run [our tests] on people without long Covid symptoms who are currently, or who were, infected with Covid," Dr Stringer acknowledged.