New research has shown that antibodies produced by our bodies to protect against Covid-19 are triggering increased function of platelets, which may be causing fatal blood clots in patients with severe disease.

The researchers took antibodies from people with severe Covid-19 infections produced to fight the virus’s spike protein and cloned them in a lab to study.

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They found that the small sugars on the surface of these antibodies were different to antibodies from healthy individuals, and when those cloned antibodies were introduced in a lab to blood cells taken from healthy donors, there was an observed increase in platelet activity.

Clinical trials are underway

The team also discovered it was possible to reduce or stop platelets from responding in this way by treating blood with active ingredients from different medication which is known to either inhibit platelet function or immune responses.

The findings suggest that it may therefore be possible for drugs that are currently used to treat immune system problems to reduce or stop the cells from producing an exaggerated platelet response.

The MATIS trial (led by Imperial College London and Imperial College Healthcare NHS Trust) is currently testing these drugs in clinical trials to see whether they will reduce serious clotting for hospitalised Covid-19 patients.

"Our studies...explain how and why dangerous blood clots may occur in severely ill Covid-19 patients"

Professor Jon Gibbins, Director of the Institute for Cardiovascular and Metabolic Research at the University of Reading said: "Until now, we have only had assumptions about why platelets involved in clotting were being activated during Covid-19 infection.

"One way to think of what happens is that the immune response that is designed to protect you from the infection in some cases, particularly in severely ill patients, actually causes more damage. In this case, the antibodies that are produced to stop Covid-19 from spreading trigger infected cells to induce platelet activity which causes clotting even though there is no wound that needs healing.

"We are particularly excited because our studies of platelets in the laboratory establishes important mechanisms that explain how and why dangerous blood clots may occur in severely ill Covid-19 patients, and importantly, also provides clues as to how this may be prevented."