This test could determine which people might need the 3rd dose booster.
Scientists do not rule out that this minimum of six months of vaccine protection, given the previous results, could be much more. And it is that this latent cellular immune response has also been found up to 15 months later in patients who have had covid-19, as stated by one of the main signatories of the study, Victor Matheu, an allergist at the HUC. "We did studies on the only three patients who suffered from COVID-19 in the first wave and had not yet been vaccinated," explains Matheu, who points out that what they discovered left them astonished: "despite the fact that the antibody titer had dropped importantly, it still had a cellular response similar to that of the beginning. '
The immune response is of several types. On the one hand, it has the cells that act in direct contact with the pathogen (antibodies) and, on the other, with which they store the information of the pathogen in a kind of infinite library, to which they can go to find out at any time if must fight him. The latter are the T lymphocytes, also known as memory cells, which are in charge of recognizing the virus if the body encounters it again.
"We are preparing a Covid Immune Response Unit at the HUC"
The method with which they have managed to detect this cellular immunity is a true revolution for the field. The researchers, led by immunology expert Yvelise Barrios, also a member of the HUC, realized that, while there was a method to quantify antibodies (the so-called rapid test), there was a gap in knowledge regarding immunity. cell phone in covid. The researchers adapted the delayed-type hypersensitivity test - known as DTH - to COVID-19, to determine the booster immunity it generates in the body. This type of test has been widely used in the past and, for example, under the trade name Mantoux or tuberculin, it was used to detect whether a patient had tuberculosis.
A test like allergies
The current test is a skin test, similar to the one used to detect allergies but with a later response. "In allergy tests the determination is immediate because what we detect are mast cells, the cell of the immune system that regulates allergies," says Matheu. In this test aimed at covid, the cell in search and capture is the lymphocyte, specifically the T lymphocytes. In honor of its counterpart in tuberculosis, it has been called Covidin.
Until now, cellular immunity could only be known through a cumbersome and expensive test that required an in vitro culture. In addition to its cost, the main problem with this test is that it cannot be done to everyone. "During the confinement we had to sharpen our ingenuity, because we did not get reagents," says Matheu.
It was then that he and Barrios recalled a skin diagnostic method that was used years ago in Madrid to perform immunodeficiency tests on patients who had developed AIDS. To this day, and thanks to their insight, this group of health workers is doing a unique job in the world, as they are pioneers in using the skin test to verify the immune response in this disease. This finding has drawn the attention of a Canadian ByoVaxys laboratory that will use this knowledge to develop CoviDTH, the company's disposable point-of-care diagnostic tool that detects a T-cell response to SARS-CoV-2 in vaccinated or exposed patients. to SARS-CoV-2. "These human studies conducted by Dr. Barrios give us significant confidence in CoviDTH, especially as we are preparing for the planned Phase I / II combined study in the United States," said Kenneth Kovan, CEO and COO of BioVaxys, in a press release.
"Although the antibodies decrease over time, the cellular response is maintained"
In the hospital center, the technique has also been a catalyst with which the research group has managed to open a Covid Immune Response Unit thanks to the support of the HUC management. It will be handled by both Barrios and Matheu and will therefore have a multidisciplinary approach based on immunology and allergology. "At the moment we are preparing the circuit and recruiting patients," says Barrios, who insists that the unit will treat the most vulnerable patients. And it is that knowing how long the immunity of the vaccine or contagion will last not only serves to have certain certainties about our protection, but it can also help make better decisions regarding third doses. "This diagnostic method could be performed in a nursing home to find out who may need to inject a third booster dose," says the allergist, who insists that its use should begin to be democratized in order to make decisions based on science.