Harvard experts explained how vaccines generate multiple mechanisms to protect against COVID-19

Antibodies are released that bind to coronaviruses and mark them. In this way, the virus cannot penetrate its target cells and they are destroyed by a macrophage (Juan Gaertner)

The coronavirus pandemic is still going on. During the last week reported by the World Health Organization, An increase in the number of new weekly cases of COVID-19 was recorded in Africa (31%) and in the Americas (13%), and the number of new weekly deaths increased in South-East Asia (69%) for a delay in reporting deaths from India. While the circulation of the coronavirus continues, there is doubt about how long vaccines will be able to protect the population against the risk of new variants or sub-variants of greater concern appearing.

A study published in the open access journal PLOS Biologynow showed that vaccines induce multiple mechanisms of the immune system to protect against severe COVID-19.

The study was carried out by Galit Alter, from the Harvard University in the United States and his colleagues. They found that while vaccine-induced neutralizing antibody responses protect against infection, control of viral replication is mediated by responses involving T cells and Fc receptor-binding antibodies.

While vaccine-induced neutralizing antibody responses (i.e., antibodies that bind directly to the virus and “neutralize” infection) provide the main protection against infection and severe disease, other less well-known immune responses also contribute to protection.

More than 11.5 million doses of vaccines against COVID-19 have been applied in the world (REUTERS / Hannah Beier)
More than 11.5 million doses of vaccines against COVID-19 have been applied in the world (REUTERS / Hannah Beier)

To better understand the protective role of each immune mechanism, The researchers immunized five groups of five rhesus macaques with different doses of the vaccine or with a mock control. They then induced all macaques with a SARS-CoV-2 coronavirus infection and analyzed viral replication in the upper and lower airways 1, 2, 4, 7, and 10 days after viral challenge.

researchers found that the immune mechanisms responsible for controlling viral replication after infection were dose-dependent, indicating an important role in protection against severe disease and death.

These additional immune responses that control viral replication are mediated by the so-called Fc receptor, which is a cell-surface molecule that recognizes the invariant part of antibodies and can trigger the destruction of infected cells, and by cell responses T. These T cells complement the other antibody responses that directly neutralize the virus.

As the authors wrote, “The continued emergence of several variants of SARS-CoV-2 with increased infectivity and immune evasion capabilities has further complicated the global vaccination effort. These data provide critical insight in the context of the current pandemic, in which emerging variants of concern have the ability to break through vaccine-mediated protection, but vaccine-induced immunity still elicits a response against multiple variants. and provides some level of protection against serious illness and death.”

Scientists in the US discovered that the immune mechanisms responsible for controlling viral replication after infection were dose-dependent (REUTERS/Jose Luis Gonzalez/File)
Scientists in the US discovered that the immune mechanisms responsible for controlling viral replication after infection were dose-dependent (REUTERS/Jose Luis Gonzalez/File)

Study co-author Daniel Zhu said: “Following our comprehensive profiling of the effects of neutralizing antibodies, T-cell immunity, and the mechanisms of action of alternative non-neutralizing antibodies, we found correlations of immunity in the context of both complete protection as well as viral load mitigation at breakout infection. We also observed differences in the robustness of key features of the immune response across vaccine doses, which could help guide future vaccine design and boosting.”

consulted by Infobaethe doctor Elena Obietahead of the communicable and emerging diseases service of the Municipality of San Isidro and member of the Argentine Society of Infectology (SADI), commented: “The study carried out in the United States provides more details about the protection mechanisms induced by vaccines, which have saved the lives of millions of people since they were applied in December 2020.”

In addition, Obieta added that “today it is known that it is not necessary for people to take a test to measure how much immunity they have against the coronavirus. The important thing today is to apply both the primary vaccination scheme and the booster doses. Vaccines are known to generate neutralizing antibodies as well as cellular immunity. Cellular immunity is even more important to have protection against the risk of developing a serious condition.”

In Argentina, in November of last year, researchers from the Institute of Biology and Experimental Medicine of the Conicet, led by doctor Gabriel Rabinovichhad carried out a study on the cellular response after the application of the inoculants that are applied in the country when the Ómicron variant was not yet circulating.

It was shown that the immune response at the cellular level with the vaccines applied in Argentina is robust, whether the schemes were with the same vaccine or with different vaccines. No statistically significant differences were detected between those who received a homologous vaccination (two doses of Sputnik V) and those who received a heterologous type (a first dose of Sputnik V, combined with another of the other vaccines available in the country).

In Argentina, the COVID-T Platform was developed to study cellular immunity after vaccination and infection
In Argentina, the COVID-T Platform was developed to study cellular immunity after vaccination and infection

The research was possible after the generation of the COVID-T Platform, unique in Latin America, designed and developed by Argentine scientists, with the aim of monitoring the antigen-specific T lymphocyte response in patients recovered from COVID-19 and in vaccinated people. The project arose within the framework of the Coronavirus Unit, CONICET and the National Agency for the Promotion of Research, Technological Development and Innovation (R+D+i Agency).

“The reaction of T lymphocytes is very robust, both for the CD4 and CD8 cell subpopulations, at 14 days after vaccination. The immunogenic capacity of the vaccine is comparable in homologous and heterologous strategies”, described the researcher Rabinovich. CD4 T lymphocytes (cells) They help coordinate the immune response by stimulating other cells of the immune system, such as macrophages, B cells, and CD8 T cells to fight SARS-CoV-2 infection in the body.

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