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They identify memory immune cells in blood and lungs essential to control the coronavirus

A study led by the group of Infectious Diseases of the Vall d’Hebron Research Institute (VHIR) has analyzed the differences in the cellular immune response during infection by SARS-CoV-2, depending on the severity of the patients.

Experts have found, for the first time for this virus, that the lungs of people who have had the disease remain memory T cells long-term resident that would allow to fight against a possible reinfection. The results have been published in the journal Nature Communications.

For the first time for this virus, it has been observed that long-term resident memory T cells remain in the lungs of people who have had the disease that would make it possible to fight against a possible reinfection

In the acute phase of infection, the researchers identified patterns in the response of the T lymphocytes in blood that are associated with the clinical evolution of the patients. Specifically, hospitalized patients had higher levels of the IFNg and IL-4 cytosineswhile those with milder symptoms had more IL-10.

“IL-10 is a cytokine that could play an important role in controlling inflammation. If it is accompanied by an antiviral response, IL-10 creates an environment that favors the resolution of the infection without promoting an exaggerated inflammation, which is associated with the severity of covid-19 ”, he reasons Meritxell Genescà, VHIR principal scientist and one of the authors of the work.

In addition, the most serious patients have fewer T lymphocytes, since many of these cells die from overstimulation caused by the great inflammation that is generated. This death occurs mainly in the cells that produce IL-10, which worsens the person’s situation.

The study was carried out with samples of 46 patients during the first wave of the pandemic: 14 people with symptoms that did not require hospitalization, 20 mild patients but required hospitalization, and 12 seriously hospitalized patients.

A barrier to prevent reinfections

The experts noted that lymphocytes activated to fight virus infection have markers that indicate they will travel from the blood to the lung. For this reason, the persistence of resident T cells in the lung that would serve as memory cells to fight against possible future reinfections was analyzed.

Memory T lymphocytes were found in the lung up to 10 months after infection, which would indicate that it would be a long-lasting memory

This type of lymphocyte was studied in seven convalescent patients of covid-19, who had had different clinical evolutions, taking advantage of the need to do biopsies for other causes in these people.

Memory T lymphocytes were found in the lung up to 10 months after infection, which would indicate that it would be a long-term memory.

Thus, in the event of a new SARS-CoV-2 infection, the response against the virus would be localized in the lung. “The respiratory tract is the entry route of the virus, therefore, these cells would give a much faster and more efficient response, essential to limit its spread and the disease,” adds Genescà.

Also present in mild cases

Resident memory T cells had previously been described for other viral and bacterial infections in different organs and tissues. In the lung, for example, there are some that target cold or flu viruses, but this is the first time they have been identified for SARS-CoV-2.

It is relevant that these cells have been found even in people who passed the infection very mildly, not only in the most severe cases.

Maria Jose Mailbox, head of the HIV Translational Research line at the VHIR, comments that “to know if a person has an immune memory or not when faced with an infection, analyzing antibodies or blood cells does not give us all the information, since it is also important the presence of memory resident T lymphocytes in the lung ”.

Although, in clinical practice, they could not be easily identified since it requires a biopsy that is invasive, it is relevant that these cells have been found even in people who passed the infection in a very mild way, not only in the most severe cases.

Knowledge for vaccine generation

Among the results, it also stands out that the type of immune response that develops in patients is related to the protein or proteins that the immune system recognizes from SARS-CoV-2 when it enters the body. This fact could be related to the development of vaccines for covid-19.

The authors emphasize that studying the types of immune response and which parts of the virus respond to the different memory profiles generated will help the development of more effective vaccines.

Currently, all available vaccines target protein S, the key for the virus to enter cells. In this sense, new vaccines could include other parts of the virus.

The authors emphasize that studying the types of immune response and which parts of the virus respond to the different memory profiles generated will help the development of more effective vaccines.

Currently, VHIR researchers are analyzing the differences between the immune response that occurs in naturally infected patients or in vaccinated people.

Reference:

Judith Grau-Exposito, Nerea Sánchez-Gaona, […], Meritxell Genescà. Peripheral and lung resident memory T cell responses against SARS-CoV-2. Nature Communications volume 12, Article number: 3010 (2021)

Fountain:

Vall d’Hebron Research Institute

Rights: Creative Commons.

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