One big mystery: Why do some people develop severe Covid-19 disease, resulting in death, while other similar people do not show any symptoms and may not realize they are infected at all?
Scientists have uncovered some health and age factors that make some people more at risk of developing a severe form of the disease, and it may cause their death, such as the elderly, overweight or obesity, and the presence of one or more chronic diseases, such as diabetes, cardiovascular disease, kidney or lung disease and cancer. . But the opposite may also be true, could some people actually have some form of protection?
A brief article published recently in Nature Reviews Immunology explained that a large proportion of the population has immune cells that are able to recognize parts of the SARS-Cove-2 virus, which may give them the ability and a lead in fighting infection. In other words, some people may enjoy a greater degree of self-protection.
“What we found is that people who have never been exposed to SARS 2 … about half of the people have some T-cell reaction,” said author Alessandro Sitt of the Center for Infectious Diseases and Vaccine Research.
The human immune system charged with maintaining human health in the face of bacterial, viral, fungal, parasitic and other invaders, has two main components: the innate immune system and the adaptive immune system.
The innate immune system is the first line of defense and parts of it include physical barriers such as the skin and mucous membranes that physically prevent the entry of invaders. It also includes some cells, proteins, and chemicals that release protections such as inducing inflammation and destroying invading cells.
When the innate immune system is immediate and indeterminate (it tries to prevent anything from entering the body), the adaptive immune system is directed against previously known invaders.
The adaptive immune system includes a type of white blood cell, called a “B-cell,” that roams the body in search of invasive and evil objects. All B cells have a unique antigen on their surface that can bind to a unique antigen (the technical name of a foreign invader) and prevent it from entering a host cell.
When he finds the evil cell, he binds to it and activates the “B-B” cell, which in turn copies itself and produces antibodies, which ultimately creates a huge army of cells to confront the “specific invader”.
In this way, the antibodies created by the immune systems of people who have had Covid-19 disease are formed.
Unfortunately, some recent studies have shown that antibodies to this coronavirus can wear off very quickly, especially in people who have been mildly infected with Covid-19.
The results of these studies raised the concern of many researchers because this matter makes the scientific community unsure of how long a person infected with this virus will remain protected from new infection, especially in the absence of a vaccine that stimulates the antibody response to help protect humans for a long time.
Despite this concern, it should be noted that antibodies are not the only weapon an adaptive immune system uses to ward off infection. The T cell, known technically as T cells, helps with the protection system. It is a problem of three types, which the body excretes after infection to aid in future infections from the same invaders.
A T cell helps the body remember that invader if it becomes infected again. The last one chases and destroys the infected damaged cells, and the third helps in other ways.
T cells like these, which interacted with the SARS-Cove-2 virus, were discovered by Seet and co-author Shane Croty by accident in blood samples collected several years ago.
The two experts were experimenting with blood samples from people who had been infected and recovered from Covid-19 disease. And they needed negative blood test results to compare samples.
The two experts selected blood samples from healthy people collected in San Diego between 2015 and 2018. “There was no possibility of these people being exposed to SARS-Cove 2. When we did the analyzes, it was found that the negative control was not completely negative, as about half of the people had a reaction,” said Set.
“Chen and I looked at the data and we were looking at it from the right, from the left, from the top and from the bottom, and it was really” real, “the expert added. This interaction was real. Tests showed that people who had never seen this virus before had some T-cell reaction against the virus. ”This paper was published at the end of June in the journal Cell.
They are not the only ones who have seen this, Sit and Crotty note, “These results have been confirmed recently in various continents, laboratories, and even by different techniques. The researchers believe that the T-cells’ identification of parts of the SARS-Cove 2 virus may partly come from previous exposure to one of the four known coronaviruses that cause the common cold in millions of people each year.
Despite this, many questions remain unanswered, including whether this recognition of parts of SARS-Cove 2 by T cells helps or harms.
“Are these T cells useful in protecting against Covid-19 disease? That is the big question,” says Crotty. “We don’t know if T cells are helpful or not, but we think it makes sense to speculate that they might be helpful.
For his part, Dr. Arturo Casadeval, Chair of the Department of Molecular Microbiology and Immunology at the Johns Hopkins School of Public Health, told CNN, “All these coronaviruses are linked together, given that we encounter them every year, it is not surprising that we have T-cells. T interact with it ”.
A few months ago, Casadevall raised the idea of why some people get sick and others don’t, and wrote in an opinion piece on Bloomberg: “One of the variables is what we call immune history. All the things that I’ve encountered in your life, all the vaccinations, the common cold, and all the digestive disorders, I’ve created basic knowledge that can help hurt. ”
Casadevall posits that some people without symptoms of Covid-19 may be able to clear the virus quickly thanks to a T-cell reaction.
Assuming that a large portion of the population has some type of T-cell interaction with the SARS-Cove 2 virus, what does this mean for efforts to find a vaccine? According to health experts, this has several implications.
There are implications about how long it will take for everyone to achieve what is known as “herd immunity” which means that a sufficient number of the population is immune to SARS-CoV-2, thanks to infection or vaccination, and the virus can no longer be transmitted easily.
John Iwandis, professor of medicine, epidemiology and population health at Stanford University, says: “In terms of herd immunity, if we really have a very large proportion of the population already immunized in one way or another through these cellular responses, we can include that in the statistics that we need to establish herd immunity. . In other words, if a high level of herd immunity is provided, this will change the speed of the virus spreading across different societies and populations, according to “Euronews”.