“Since there are people who recover from coronavirus, we can safely say that they have developed the antibodies necessary for this cure. So could we not, from a blood test, identify these antibodies in order to make them either a vaccine or at least a medicine against this virus? ”Asks Martin Paradis, of Saint-Martin-de- Beauce.
The ‘re Antibodies are proteins that the immune system produces so they “cling” to a pathogen (virus, bacteria, toxin) and off. So technically, we cannot make a vaccine from antibodies: vaccines are rather weak or dead microbes, or often “pieces” of microbes that we present to the immune system so that it learns to produce its own antibodies.
Now what would happen if someone injected antibodies from cured COVID19? If it is a healthy person being inoculated, not much will happen – the antibodies will give them temporary immunity that will quickly subside as they are eliminated by the body. But if it’s a coronavirus patient, then … well it can work, it can be an effective treatment. In fact, just last Thursday, the Chinese daily newspaper Global Times announcedthat a plane had taken off from Shanghai to Rome with medical personnel on board and “31 tonnes of medical equipment, including plasma from patients recovered from the coronavirus, in order to help Italy fight the pandemic of COVID19 “. Plasma is the liquid part of the blood, which remains when all cells (red blood cells and immune cells) and platelets have been removed from the blood. Antibodies are part of the plasma and will fight disease if injected into someone.
It is not yet fully established, it should be noted, that this will give good results against the coronavirus. Greg Poland, an American infectious disease specialist, recently noted in an interview with the medical magazine StatNews that “we have only a few encouraging, but anecdotal reports from China. Nothing has yet been published [in the scientific literature]. But it’s definitely worth a try. ”
It must be said that the technique is far from new. In fact, the very first Nobel Prize for medicine was awarded in 1901 to the German researcher Emil von Behring for having developed “serotherapy”, that is, treatment with plasma (or “serum”) of cured patients. As early as 1890, he demonstrated that laboratory animals could be saved from diphtheria and tetanus by inoculating them with the plasma of other animals that had survived these diseases. And the first application to humans occurred the following year, when he successfully treated a child with diphtheria.
At the beginning of XX th century, serum therapy had already become a relatively common treatment. But large-scale serum production was always a problem. The laboratory rats were too small to produce enough to treat a single human patient, so horses were used instead. But even at this account, it was impossible to get really large quantities.
Subsequently, with the massive arrival of antibiotics from the 1940s, serotherapy was more or less neglected in medicine. Antibiotics worked just as well (and even better in some cases) and they were more available, more convenient and less expensive.
It was not until the 1970s that an industrial process was finally discovered to make so-called “monoclonal” antibodies – that is, all identical, unlike the various antibodies in plasma. But, again, it was often very expensive and the quantities produced were not that great.
In addition, it was usually mice that were infected and then isolated and reproduced their antibodies. However, the antibodies of mice differ from ours, so that the human immune system recognizes them as foreign bodies and attacks them. Because of this, mouse antibodies have a “half-life” of 2 to 3 days in the human body – which means that their number decreases by half every 2-3 days, and this significantly reduces their effect. therapeutic. Fortunately, we ended up finding ways to “humanize” them – enough to extend their half-life to 20-23 days.
If antibody therapy ends up being a tool to fight COVID-19, it is probably more on the side of the industrial production of monoclonal antibodies than plasma injections that help will come. Besides, in addition to the “vaccine candidate” that Medicago announced last week and which has attracted a lot of media attention, the biopharmaceutical company has also indicated that it has developed antibodies against COVID-19. .
Medicago uses plants that it manages to “manipulate” in order to make them produce large quantities of “complex proteins”, such as antibodies and viral proteins that serve as vaccines, explains Nathalie Charland, director of scientific and medical affairs at the company. The leaves are then harvested and the antibodies are isolated and purified.
If all goes well in future clinical trials (which is never won in advance, it should be noted), these antibodies could possibly serve as a treatment or, at the very least, a little “boost” for some patients.
“This is what had been done [with convalescent plasma] for Ebola: the idea is that even if we are not able to have antibodies that are 100% effective or in sufficient quantity to eliminate completely the virus in a patient, if we can at least reduce the viral load [note: the “dose” of virus circulating in the body], it’s better than nothing, it can improve the chances of recovery ”, says M me Charland.
A story to follow, therefore …