The body’s own immune defense cells, known as T cells, can recognize astonishingly large parts of the new SARS-CoV-2 virus. This was the finding of an international team of scientists led by the Tyrolean researcher Daniela Weiskopf from the La Jolla Institute for Immunology (LJI) in California out. This also opens up additional options for vaccine development, according to the researchers in the journal “Science Immunology”.
The team dealt with blood samples from sick people in San Diego and later in Rotterdam. The main focus was on T cells, a group of white blood cells that are tasked with identifying new threats and driving the acquired immune response.
Virus is broken down into components
Using the “megapool” method, in which the virus is broken down into its individual protein components in a special reagent, they went on to analyze the immune response of patients with severe and milder Covid-19 courses. Both T-helper and T-killer cells usually recognize “only very small virus parts – that is, pieces of eight or nine amino acids,” explained Weiskopf. In contrast to the B lymphocytes, however, they do not produce specific antibodies, which then attack the virus, but must recognize their target structures directly on the surface of the intruders.
It is almost impossible to test the response of the immune cells to each of these pieces of virus – in the case of SARS-CoV-2 that would be thousands – in succession is almost impossible. With the “Megapool” method it is possible to collect and use small amounts of blood to determine which parts of a virus are recognized by the immune system. This is also important because intensive care patients who are already severely battered do not necessarily want to weaken their blood with a relatively large amount.
T helper cells react to the virus
In the case of SARS-CoV-2, the scientists obtained astonishingly uniform results: For example, they found T-helper cells that reacted to the novel coronavirus in all ten closely examined patients, eight out of ten also had T-killer cells that were found to be against the pathogen Position. Their amount also increased over time. “There has been speculation that the virus may be hiding from the immune system, but we have shown that it is well recognized,” said Weiskopf.
Born in Innsbruck, who studied in her hometown at Leopold Franzens and the Medical University and specialized in the field of immunology, she moved to Southern California as a postdoc at the La Jolla Institute for Immunology (LJI). There, Weiskopf started working on the dengue virus in 2009. “I’ve always been fascinated by how the immune system recognizes viruses,” said Weiskopf.
In the past few years, the scientist has expanded her pathogen portfolio to include other mosquito-borne viruses such as zika, yellow fever and chikungunya. With the advent of SARS-CoV-2, she began to deal intensively with the new virus, and above all with the response of the body’s own defense system to it.
“Good news for vaccine developers”
The characteristic spike protein, which acts as a target for almost all vaccines under development, was also recognized by this part of the immune system in all examined infected persons. “This is good news for vaccine developers,” said the immunologist. In fact, the study showed that “23 out of 25 proteins from the virus are recognized by T cells – that’s good.” For future generations of vaccines, this would bring more options because other proteins could also be used as target structures.
When the scientists also confronted older blood samples from 2015 to 2018 with the new virus, they also noticed that almost half of the T cells showed a reaction to virus parts. “The hypothesis is that these are cross-immunities that are caused by normal circulating cold viruses,” said Weiskopf, who continues to work on this question.
The very similar findings in the USA and the Netherlands indicate that the immune system can recognize SARS-CoV-2 relatively well in many regions. It is still a matter of finding out whether this is actually the case: “It is important to us that we share the reagents freely. I have now distributed them to 60 different laboratories around the world,” says the researcher.
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