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Using Covid-19 Cured Plasma: 5 minutes to understand serotherapy

2020-05-01T14:23:26.265Z


Trials carried out in particular in France aim to improve the healing of Covid-19 patients with the plasma of survivors. Explanations.


This is a new avenue, to promote the healing of patients with Covid-19. On Thursday, the French Medicines Agency announced that it had extended outside clinical trials and under strict conditions, the use of plasma from cured patients in order to treat patients who had been seriously affected by the coronavirus.

Serotherapy, this is the name of this treatment, has already been the subject of several clinical trials around the world, notably in China or the United States. The Parisian takes stock of these hopeful tests.

What is serotherapy?

It all depends on the potential immunity that the plasma of an already infected person can confer. Serotherapy consists of reusing plasma, that is to say the liquid part of the blood where antibodies are concentrated after an illness. When a person is infected, his white blood cells detect the foreign presence in the body, the antigen, and secrete a substance intended to fight it: it is the antibodies which provoke an immune response. When the disease disappears, the latter, also called immunoglobulins, remain in the plasma. They are the ones that interest scientists.

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This so-called “therapeutic” plasma, with already developed antibodies, is recovered from a person who has already been infected with the disease in question, in order to be transfused in a patient who is most often in a acute phase of this same disease. Which should help him in his healing. If this works, then we speak of passive immunity: the patient was able to recover thanks to outside help and not thanks to his own immune system, which could not, alone, create enough antibodies (we would then talked about active immunity).

This technique has already been used, on a small scale, for patients with SARS, another coronavirus that causes respiratory symptoms, as well as for Ebola virus and Nile virus. More generally, plasma donation is a practice often used, especially in patients who have a lack of immune defenses or suffer from autoimmune diseases.

How could it help Covid-19 sufferers?

According to the French Medicines Agency (ANSM), "some data show that the plasma of people who have been sick with Covid-19 contains antibodies active against the virus". She hopes that their reuse in people who are still sick and have acute respiratory distress syndrome (ARDS) "could help improve patient survival."

If this research is multiplying, it is because this technique has proven effective against other coronaviruses, the family of viruses from which SARS-CoV-2 is derived, which causes Covid-19. "The experience of previous epidemics with other coronaviruses, shows that these convalescent plasmas contain neutralizing antibodies against the virus concerned", indicates the ANSM, which cites a drop in mortality, observed during studies carried out on people infected with SARS-CoV in 2003, as well as influenza A, between 2009 and 2010. According to research published in 2005 and concerning 80 SARS patients in Hong Kong, who were injected with plasma, the death rate was 12.5% ​​compared to 17% for all Hong Kong patients.

Doctors thus intend to be able to reduce the damage of Covid-19 on the patient (damage to the kidneys, the heart and bacterial infections mainly) and therefore improve their survival rate.

What do we know about the effectiveness of this Covid-19 patient plasma?

It is too early to have convincing results from clinical trials launched only a month ago in France. The National Medicines Agency nevertheless ensures that "the therapeutic effect associated with the plasma of cured subjects of Covid-19 deserves to be explored", even if, she notes, at this stage, "the effectiveness of these plasmas n 'has not been demonstrated'. The ANSM adds that this is why their recourse "must be done as a priority in the context of clinical trials, whenever possible".

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The ineffectiveness of this treatment has also not been demonstrated at this stage, by clinical trials conducted abroad, particularly in China and the United States. "The information that arrives from these countries on the first trials conducted on several dozen patients, to date have not shown any deleterious effects in these patients", explains the ANSM. To date, according to the researchers, the only risks observed for this type of plasma transfusion of Covid-19 patients are the same as those linked to all transfusions (mainly allergies).

How is it going in France?

Since the beginning of April, a clinical trial called Coviplasm has been carried out by Professor Karine Lacombe, head of the infectious diseases department at Saint-Antoine hospital in Paris, and Professor Pierre Tiberghien, director in charge of medicine, research and innovation from the French Blood Establishment (EFS).

For the past month, plasma samples have been taken in three regions of France, from patients who have been cured of Covid-19 for at least 14 days. Initially, this plasma is recovered by the EFS during a blood donation. The plasma is then removed from the rest of the blood, using a centrifuge, which gives the donor red and white blood cells, as well as platelets.

Then comes the time for transfusion. As part of this clinical trial, involving 60 patients from Île-de-France, only half received this plasma. The goal is to compare the immune responses of each other. According to the EFS, patients are injected intravenously with one or two units of this therapeutic plasma, 200 to 240 ml each, eight days after the onset of clinical symptoms. Then, "in the absence of acute and unforeseen adverse events in the first three patients, two units will be transfused 24 hours after the first two, for a total of four units per patient", details the EFS. Or two transfusions in all, from two to four units of plasma.

From now on, this treatment will also be opened on an "exceptional basis", insists the ANSM, in convalescent people, outside of these clinical trials, in order to "increase the chances of survival" of these patients.

Who are the affected patients?

Patients, women and men, who can benefit from this treatment must have a serious form of Covid-19 infection, including acute respiratory distress syndrome (ARDS). They are selected by the caregivers of their care unit and their Covid-19 infection had to be proven by a test carried out by a laboratory. They should not have a history of allergy related to plasma transfusion.

Source: leparis

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