Scientists studying the long-term effects of COVID-19 may have finally found an explanation for the long-lasting effects like brain fog and exhaustion that we’ve come to call long COVID.
A new study published in the Journal of Medical Virology suggests the problem may lie in tiny blood clots called microclots and a sticky molecular web spun by immune cells known as neutrophil extracellular traps, or NETs.
Microclots are a smaller, sneakier version of a blood clot and apparently far more persistent in people with long COVID. First flagged by South African physiologist Resia Pretorius in 2021, microclots can clog capillaries just enough to slow blood flow and starve tissues of oxygen, exactly the kind of thing that could help fuel debilitating fatigue.
Separately, French geneticist Alain Thierry and colleagues reported in 2022 that long COVID patients show elevated NETs, the strings of DNA and enzymes white blood cells eject to grab pathogens. Normally, NETs get cleaned up quickly. In large quantities (or when present for long stretches of time), they can wreak havoc on a vascular system.
The new study, a team-up between Pretorius and Thierry, examined blood from 50 long COVID patients and 38 healthy volunteers using high-powered imaging. The results showed that long COVID blood teemed with nearly 20 times more microclots, and those clots were larger than anything seen in healthy samples. NET levels rose at a similar rate.
Researchers noticed that those NETs were woven through the microclots like rebar in concrete. This embedding happened in everyone’s blood, but it was dramatically amplified in the long COVID samples. The researchers think this NET-reinforced architecture might make the microclots unusually tough to break down, leaving them to clog up the bloodstream far longer than they should.
The difference was so stark that when researchers anonymized the samples, an AI program correctly identified long COVID patients 91 percent of the time just by looking at microclots and NET patterns. All this microbiological technobabble essentially means that there could one day be an objective test for long COVID, a condition that up to now has been notoriously difficult to diagnose.
All of this is still pretty early, and no one is ready to declare that the mystery of long COVID has finally been definitively solved. All this represents a solid first step. If scientists can figure out how these microscopic clot-NET mashups contribute to lingering COVID symptoms, they may finally have something tangible to target. That could eventually lead to a treatment for the millions who’ve felt like they’ve been permanently under the effects of a tranquilizer dart since they got COVID.
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