One contagion is enough, and the virus that causes the Covid infection remains in our blood for more than a year. In our fabrics also for two. Thus, while we feel healed because we no longer feel symptoms, while we move, work, eat and sleep, the SARS-CoV-2 virus stays inside us, settles in and remains, most of the time generating effects on our organism that we will see only in the future.
The discovery comes from a US study, signed by researchers from University of California San Francisco, the results of which were presented at the Conference on Retroviruses and Opportunistic Infections (Croi), held from March 3 to 6 in Denver. But that is not all. From another research, this time Italian, comes a second discovery, namely the fact that, thanks to its memory, our immune system is able to recognize the new variants of the SarsCoV2 virus. The study, published in the journal Nature Immunology was conducted on experimental models from the Irccs San Raffaele hospital from Milan. In particular, it is the T lymphocytes that activate against the new variants, and they manage to do so thanks to the memory induced by previous vaccinations or past infections. According to the authors of the research, new frontiers are thus opening up in the fight against the virus.
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The US study
The investigation that led to the result of the first study, i.e. that the virus generating the Covid infection remains within us for an entire year, was conducted through meticulous work carried out on blood and tissue samples. A work that started from an observation: at the beginning of the pandemic it was thought that Covid was a transitory disease, but a growing number of patients, even those who were previously healthy, continued to have symptoms such as mental confusion, problems digestive and vascular problems, for months or even years.
To assess the situation, the researchers examined blood samples from 171 patients infected with the SARS-CoV-2 virus. And using an ultrasensitive test for the Spike protein, which helps the pathogen enter human cells, they found it was still present up to 14 months later in some people. Furthermore, it was found that, among those who were hospitalized with Covid, the probability of detecting antigens was about double.
Tissue samples under analysis
The second step was to turn to the Long Covid Tissue Bank, which contains samples donated by patients with and without Long Covid. This is because the virus is believed to persist in tissue reservoirs. The results of the tests were confirmatory: portions of viral RNA were detected up to two years after infection, although there was no evidence that people had become reinfected. The virus was found in connective tissue where immune cells are located, suggesting that viral fragments may cause the immune system to attack.
An important step, but not the last. The researchers highlight that “further studies are needed to determine whether the persistence of these fragments determines Long Covid and associated risks such as heart attack and stroke”. Furthermore, based on the results obtained, the research team is involved in numerous clinical trials that are testing whether monoclonal antibodies or antiviral drugs can remove the virus and improve the health of people with Long Covid.
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Italian research
At the same time, another team of scientists, to be precise from the San Raffaele Hospital in Milan, has arrived at a second result which, according to the researchers, opens new frontiers in the fight against the virus. The research, conducted on experimental models, has ascertained that, thanks to its memory, the immune system is able to recognize the new SARS-CoV2 variants. In particular, it is the T lymphocytes that activate against them, and they manage to do so thanks to the memory induced by previous vaccinations or past infections.
Covid, immune memory a shield against new variants
Currently one of the open problems is the appearance of new Covid variants capable of escaping the immune system. On this front, the new research represents a turning point: “It revealed that T lymphocytes, thanks to their historical memory, are able to provide protection against the SarsCoV2 virus even when antibodies are not present – explains the research coordinator Matteo Iannacone, director of the division of Immunology, transplants and infectious diseases at San Raffaele and professor of General Pathology at the Vita-Salute San Raffaele University -. This form of defense, independent of antibodies, highlights the crucial significance of the T cell-mediated cellular response in the fight against the virus.”
The mouse study
They took part in the study Luca Guidotti e Marco Bianchiboth from San Raffaele, as well as Raffaele De Francesco, of the National Institute of Molecular Genetics and of the University of Milan. The research was conducted on mice, some of which lacked antibodies but had efficient T lymphocytes and others in which the cellular receptor to which the SarsCov2 virus binds was reproduced.
“We observed how a certain subgroup of T lymphocytes, called CD8+, are crucial in combating serious infections, while the so-called CD4+ T lymphocytes play a complementary role in milder infections”, highlights the first author of the study, Valeria Fumagalli.
The results thus indicate that, contrary to what was believed, the antibody-mediated response is not the body’s main line of defense. “The results of our study – concludes Iannacone – modify the traditional understanding of immunity and demonstrate the importance of including the immune response mediated by T lymphocytes in the monitoring of responses to vaccinations and in the development strategies of new vaccines”.
“But getting vaccinated remains a priority”
However, all this, the researchers point out, does not cloud the principle according to which “the vaccine against Covid infection is a priority”. “The indication for vaccination remains the fundamental piece to protect the population from serious disease, and our research demonstrates the effectiveness of this approach also for protection against reinfections caused by viral variants – concludes Iannacone -. Our work paves the way to new vaccination and therapeutic strategies for effective and long-lasting protection against the virus and its emerging variants”.
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Pregliasco: “Important pieces to contain the virus”
He is convinced that the two studies insert two important pieces into the knowledge and management of the SARS-CoV-2 virus Fabrizio Pregliasco, medical director of the Galeazzi Hospital in Milan. “The first research, the American one, gives us further innovation in understanding the mechanism of damage implemented by the virus, which is not only that of the lung, which is evident, acute and at risk of death – says Pregliasco -. In essence we need it to better understand Long covid, which from a symptomatic point of view is not clear. Already the loss of taste and smell, from the beginning, gave the idea of something more complex. Now we have confirmation of this. And it should be remembered that others viruses hide for a long time in our organism without giving any sign of their presence, except to be seen in a bombastic form. This happens for hepatitis C, which after 15 years manifests itself in the form of hepatocellular carcinoma”.
“The second study gives us an edge by confirming the existence of a cross-reactivity of our immune system: in practice it acts and recognizes multiple pieces of the virus – concludes Pregliasco -. On the contrary, vaccination with mRNA is more selective. we see the same thing for the flu: the first infection acts as the first imprinting, which somehow maintains cross-reactivity. However, the importance of getting vaccinated remains, an indispensable condition to protect ourselves from the more serious effects of the infection”.
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– 2024-03-17 15:58:23
