French laboratory develops first test to measure immunity to coronavirus

Unlike other serological tests, that of the Pasteur-TheraVectys vaccinology laboratory provides information on the effectiveness of the antibodies produced by a person who contracted SARS-CoV-2.

“A precious tool to support deconfinement”. It is in these terms that the virologist Pierre Charneau, director of the Pasteur-TheraVectys vaccinology laboratory, describes the serology test developed by the latter, in an interview published this Monday. He would thus be the first to be able to specify the degree of immunity of patients cured of SARS-CoV-2, but also of all people (caregivers, relatives of an infected patient, cashiers …) who may have been contact with the coronavirus.

After having been tested for the first time in the context of the Institut Pasteur study on the Jean-Monnet high school, it has now been used since April 20 by epidemiology research. Unlike existing serological tests, which only detect the presence of antibodies developed by a person after an infection with the Covid-19, that developed by the laboratory of the virologist Pierre Charneau “provides information on the effectiveness of the antibodies”.

“The presence of antibodies does not allow us to say whether or not we are protected against a new infection by the Covid-19. […] We have developed a ‘sero-neutralization’ test which detects antibodies but above all which measures their ability to inhibit the entry of the virus into a cell. This test therefore provides information on the effectiveness of antibodies, “he explains daily.

The test classifies the degrees of immunity into three categories: strong neutralizing, weak and non-neutralizing.

A reliable serological test?

This is a “fundamental step” for Doctor Alain Ducardonnet, health consultant, asked about this new test this Monday morning on our antenna. Because until then, many scientists and the World Health Organization (WHO) wondered about the known effectiveness of the antibodies produced by a person who contracted the coronavirus.

However, a question arises concerning the reliability of the serological test. It could, in fact, give false positives, namely “a person detected positive for neutralizing antibodies but who would not in reality be protected” and who would therefore spread the coronavirus, explains Pierre Charneau.

“Today, we have performed thousands of tests and, for the moment, we have never had a false positive. With so little hindsight, it is very difficult to guarantee 100% reliability. What we are today ‘hui certain is that the error rate is very low “, assures the director of the Pasteur-TheraVectys vaccinology laboratory.

“Several hundreds of thousands” of test results

Pierre Charneau says on a daily basis that “making this test at very high speed is not a major problem”.

“We have in stock all the reagents necessary to produce several hundred thousand. And a single machine from the Institut Pasteur is enough to analyze 50,000 to 100,000 samples per week. The principle is therefore to multiply the centers in the territory in such a way to obtain a very high throughput of analyzes “, he continues.

However, this does not necessarily mean that it will be immediately available to individuals, because the laboratory is not yet empowered “to deliver a personalized diagnosis”.

“The regulatory validation procedures for tests with personalized human diagnosis are longer. The French National Authority for Health has drawn up specifications to which we are subject. It requires, for example, a reliability of at least 98%. This low water level. But it has to be demonstrated experimentally, and it takes several weeks. We are not there yet, “explains the virologist.

Once the green light has been given by the High Authority for Health, it will then be possible to be tested by going to take a blood test in a city analysis laboratory, then to wait two days to have the results.

David T

David T is a french Medical student, during its free time, he is writing for The Medical Progress and helping us to understand better the Coronavirus.

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