Our immune system against coronavirus

Audio 04:01

By: Nicolas Rocca Follow

How does our immune system fight infection? Can we be immune to the virus?

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As with any infection, the body recognizes the presence of an intruder, and it tries to respond by attacking the virus. "  Cells in our immune system recognize the infectious agent, alert other immune cells by emitting cytokines and by receiving cytokines they produce antibodies to neutralize the virus  ", explains Frédéric Altare, specialist in the immune system within from the University of Nantes.

These cytokines circulate in our system in order to respond as effectively as possible to the threat posed by the virus. But obviously what is described only corresponds to the best of cases, because this coronavirus can continue to harm even if the body attacks it. "  The special case of Covid-19 is that this immune response, which is normally limited in time, can get carried away in certain individuals and create an exacerbated version of the immune response and create a major immune disorder called a cytokine storm  ", continues Frédéric Altare.

In other words, the immune response turns against the patient and attacks the respiratory, cardiac or nervous system and is the main cause of death in patients with Covid-19.

• Is it possible to prepare your body for Covid-19 infection?

There are many tips that flourish on the internet to prepare, or strengthen your immune system, among other things being exposed to the sun to fill up on vitamin D. There is also stress and fatigue, particularly present in this period of confinement, which can play a role in the preparation of our immune defenses.

But it must be clear, these are marginal factors that absolutely do not prepare us to face the virus: only a vaccine will be really effective.

• Does a person who is infected with the virus become immune to a possible new infection?

The answer is not yet well established. To be immune to the virus, you have to develop what is called memory immunity, produce specific antibodies, which are called neutralizers, which are adapted to Covid-19. Once we have developed them, theoretically they protect us from reinfection. Experiments on monkeys show that 28 days after their infection they were indeed immune.

But Vincent Maréchal, professor of virology at the Sorbonne, warns: "  We know that in humans it is much more complicated than in monkeys ...  " He gives us an update on the work in progress: " There are a lot of 'studies that have taken place including that recently published by the Pasteur Institute. It will show that in hospital patients, those who have a fairly severe form of the disease will develop antibodies in 5 to 14 days, ”he explains.

Vincent Maréchal still raises a question. “  When we look at patients who have few clinical signs, 15 days after the symptoms we see antibodies appear in only 30% of them. But the question is in asymptomatic patients, it is not known whether patients without clinical signs develop quality antibodies.  "

To summarize, the more virulent the disease, the more severe the symptoms and the more protected we will be from the virus. The Institut Pasteur has recently developed a test which should allow us to measure the level of neutralizing antibodies and therefore to establish in a way the degree of patient immunity. However, if this immunity is measurable it is difficult to say how long it can last, because for that, by definition, time is needed.

Our selection on the coronavirus

• Listen to our daily chronicle  Coronavirus info

• The practical questions  :
→  What is known about the mode of contagion
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→  What outcomes for clinical trials?
→  A vaccine, the only solution to stem the pandemic?
→  How to make a mask and use it well

• Our series  : "  The response, country by country  "

• Each evening, find the State of the world and Africa facing the pandemic

• See also the files of RFI Savoirs on the Covid-19:
→  Birth of a pandemic
→  Everyday life put to the test
→  The history of epidemics
→  Science facing the Covid-19
→  The geopolitical consequences

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