After a year of pandemic and millions of infected people, the cases of those who seem unassailable by the Sars on 2. Valeria Fabbretti me Alessandro Antonini, a couple originally from Terni but stationed in Milan, are an example. He got sick a year ago, but thinks it is pneumonia, she is by his side to take care of him, but without catching it. Confirmation comes months later with a serological test. Antonini is positive, Fabbretti is not. It is too early to know how we can explain the ability of some people to resist contagion. But the scientists who are studying these cases already have an idea.
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THE FACTORS AT PLAY
“When there is a pandemic, the factors at play are the pathogen, the host and the environment, which is the context in which the infection develops,” said Giuseppe Novelli, geneticist at the Tor Vergata polyclinic in Rome and president of the Foundation. Giovanni Lorenzini. di Milano – We focus on the second, which is fundamental. The first months of the infection we realized that there are asymptomatic, mild to moderate, severe cases. But if the virus is the same, then it is clear that the difference is made by the host. This always happens, with all infections. Here, the Tor Vergata team of scientists, along with a group of more than 250 laboratories around the world coordinated by Rockefeller University in New York, are trying to unravel the problem. “We study people’s DNA, we make statistical correlations based on age and sex. First we focus on the seriously ill – Novelli says – and we discover that there are between 10 and 12 percent of cases that have a particular genetic characteristic, that is, they cannot produce interferon, which is the first defense molecule. Based on this experience, we wonder if there are genetic differences in what we call “resistant”, that is, people who, when living with a truly positive subject, not only do not get sick, but are not even infected ».
GENETICS
There are several risk factors to weigh for infection. “We have found at least fifty genes that today give more or less a susceptibility to getting sick – explains Novelli – But that is not enough, because this may be scientifically valid, but it must be clinically useful. Essentially, we need to understand whether these genes carry weight. There are some that regulate interferon and play a greater role, others such as blood groups that are much less weight, even less than age and obesity. We must study them all. To be part of the group of subjects that will be examined in the Tor Vergata University study, it is necessary to demonstrate that you have specific requirements. People who want to participate will be called and subjected to an initial telephone selection. “We have a protocol approved by our ethics committee – explains Novelli – Many write to us to participate. But we must be sure that they have the requirements, for example that they have done all the tests for Covid ”. But it is not easy to understand if you really are immune to the virus based solely on the result of a test. As Roberto Luzzati, professor of infectious diseases at the University of Trieste, points out, “immunity is not only provided by antibodies. There is also the so-called cellular immunity ”. To find out, you need to investigate the lymphocytes.
THE IMMUNE SYSTEM
“We have the so-called cell-mediated immunity in which – Luzzati points out – the cellular immune system comes into play, which is the one that maintains memory over time, much longer than antibodies that can also disappear. In fact, we still know relatively little about the duration of immunity that results from antibodies. According to the latest studies, the antibodies should be present at least 6-8 months after infection, or maybe longer. The test carried out could also mislead the supposed resistance to the virus. “We remind you that some tampons have a sensitivity of around 70 percent, so we lose 30 percent – Luzzati recalls – It should be added that around 50 percent of the subjects are asymptomatic and represent the Achilles heel of this pandemic”.
