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New Low-Cost ‘Made In Spain’ Test Arrives That Detects Immunity To Covid

With the third dose of the covid-19 vaccine already approved for people in a serious situation of immunosuppression, most of the Health Councils have already begun to administer the additional prick for those with a solid organ transplant (about 60,000), hematopoietic stem cell transplant recipients (about 20,000) and patients under treatment with anti-CD20 drugs (another 20,000). The objective of the third dose is to reinforce the protection of citizens whose weakened immune systems have not responded sufficiently to the first two punctures. But how is the immune response measured? There are several ways.

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Measuring the immune-cellular response of people after having passed the SARS-CoV-2 infection or after having been vaccinated, in order to estimate how protected they would be in the face of a possible future infection (or reinfection), is a complicated technique. Hence also the complexity of the decision on the real need for a third dose. However, now, a team of researchers from the Hospital Universitario de Canarias led by immunologist Yvelise Barrios has created a new low-cost and easy-to-use test that offers information on a person’s immune response to covid-19 .

It is one thing to test if we have antibodies or not (with serological tests) and another is to measure the neutralizing capacity of the antibodies. In addition, when the amount of antibodies generated after the vaccine or infection begins to decline, as it has been seen to happen after six to seven months, it is necessary to look for T cells, which are the ones that activate memory B cells , which are those that generate a more stable immune response in the body (they are those that activate the immune system producing antibodies after the ‘order’ of the T cells).

The team of Dr. Barrios, also a member of the Spanish Society of Immunology (SEI), has presented the results of a new test that it has developed together with the allergist Víctor Matheu and that detects specific T lymphocytes for the Spike (S) protein of the new coronavirus .

As explained by the Canarian researchers, these tests are easy to perform, low cost and their reliability is practically 100% , as shown by the results obtained after tests with immunocompetent health personnel from the Hospital Universitario de Canarias who had passed the infection and / or that he had been vaccinated with the two doses of Pfizer two weeks before. Now, six months after vaccination, they are re-evaluating the test with the first test group. This test has also been tested on personnel vaccinated with Moderna , Janssen , AstraZeneca and a person who received Sputnik .

According to the scientist Barrios, they have recently presented the results with two other groups and the team is waiting for them to be published in a scientific journal. It refers to the tests of this test in people with kidney transplants , who were tested five weeks after the full regimen – “in immunosuppressed people, more time must be allowed for the immune response to be more vigorous and the evaluation to be better” – , and in people with immunodeficiencies .

How does it work?
This test involves a “pinprick” in the arm through which “a part of the S protein of the coronavirus manufactured in the laboratory is inoculated and without any harmful effect (we are not putting live virus) into the body”, clarifies Barrios. Then our skin comes into play, which will show within one to three days a small and localized reaction in the form of inflammation, redness or a little swelling at the site of the puncture, a signal that will indicate that the T cells in the body they are still “trained” to act against the coronavirus.

This test, actually, is a “classic” similar to the one for allergies, but modified to recognize SARS-CoV-2. “It is a delayed hypersensitivity reaction like the one used for tuberculin”, explains the researcher.

As it can be used on a massive scale, this test would be “very useful” to decide whether to administer booster doses to patients more vulnerable to covid-19 , such as the elderly who live in residences. A request that several Communities have already made but that for the moment Health continues to postpone pending more scientific evidence .

The elderly residents in nursing homes were the first to start being vaccinated in Spain at the end of December 2020, followed by the health personnel who attended them and who were in the front row to fight against the pandemic. After more than nine months and reached September, it could be that many of these people currently present a low or non-existent level of antibodies but that they retain an effective cellular response . And this is what this test measures, received by the scientific community with “enthusiasm” and as “very good news”.

” It is more relevant that there are T cells than antibodies because antibodies are circulating proteins that diminish and disappear over time. On the other hand, specific T cells remain active much longer because that is where the immunological memory resides,” he explains. Neighborhoods.

Barrios points out that they are “collaborating with a Canadian company for its commercialization” , which he expects to reach the market in “a few months”. Based on the result of this test, a person would know if they need a booster dose of the covid-19 vaccine or not.

Utility
“What this test interprets is a cellular immune response, but we have not correlated our test with protection,” Barrios clarifies on the phone between meetings. “It is very important – defends the immunologist – because until now, all the studies that have been done to measure the effectiveness of vaccines or to measure long-term immunity after having passed the disease are based on antibodies and that is wrong and Furthermore, it means underestimating the immune response, which we know is based on T cells . “

In this sense, this new tool could be used on a massive scale because it is “easy to interpret and perform”. For example, researchers say, in nursing homes. “Now we are talking about third doses and we believe that in many cases an underestimation is being made of which people need these boosters because only antibodies are being measured. Cellular immunity is clearly underestimated”, objects Yvelise Barrios.

Who is it suitable for?
The developers believe that this test would be “very useful” for institutionalized older people and for those with reduced mobility and difficult transfer to a hospital for a blood draw. And not only for logistics but also because they are the population group that offers the most doubts about the protection of vaccines.

“Also for the little ones , who are also difficult to draw blood. And to see to what extent they develop natural immunity after having passed the disease, in many cases, asymptomatically, and see if they have been exposed to the virus,” he adds .

However, this test could be done by anyone who wants to know if they have an immune response against covid-19 and, at least, two weeks after having received the complete vaccination (as it is the framework studied).

The lack of this new skin test, developed with “a lot of effort and little or no funding ” is that its result is positive or negative, but it does not offer a scale of amounts of cellular immunity against covid-19.

It should be clarified that cellular immunity is the branch of the specific response to a pathogen that has to be activated initially. Once T cells are activated, B cells are activated and antibodies are produced. It is different from the nonspecific and innate response, which always responds the same to microorganisms.

What does the EMA say about the third dose?
The European Medicines Agency (EMA) recognized last Thursday that “the evidence is clearer on the need to consider additional doses” in immunosuppressed and elderly people , and stressed the need to accelerate and complete the vaccination of the general population against covid-19.

However, EMA head of vaccine strategy Marco Cavalieri reiterated that “it is not clear” when to start considering a booster dose in the general population, because current evidence indicates that “vaccines offer a degree high protection “against hospitalization, death and severe covid-19 with all variants.

“From a health point of view, the priority should be to ensure that the maximum number of people are fully vaccinated (…) The evidence is increasingly clear on the need to consider additional doses for people who may respond poorly to the vaccine, such as those with severely depressed immune systems or some elderly patients, “he stressed.

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