In a new study published in Cell on May 15, 2020, a research team from the La Jolla Institute of Allergy and Immunology in the United States found that infected people contain T cells against the novel coronavirus, which may help them recover. Moreover, the defense capabilities of these cells have also been detected in some individuals who have never been infected, most likely because they have been previously infected with other coronaviruses.

Columbia University virologist Angela Rasmussen said: "This is encouraging data. Although these studies do not clarify whether people who clear the novel coronavirus infection can resist the virus in the future, it confirms the strong response of T cells to the virus. The development of long-term protective immunity. These findings can also help researchers develop better vaccines. "

More than one hundred novel coronavirus vaccines currently under development mainly target another immune response, antibodies. These proteins are produced by B cells. Ideally, they will attach to the novel coronavirus and prevent it from entering the cell. In contrast, T cells prevent infection in two different ways. Helper T cells stimulate B cells and other immune cells to function, while killer T cells target and destroy infected cells. The severity of the disease depends on the intensity of the response of these T cells.

In this new study, a research team led by immunologists Shane Crotty and Alessandro Sette of the La Jolla Institute of Allergy and Immunology used bioinformatics tools to predict which viral protein fragments will cause the most powerful T cells reaction. They then exposed the immune cells of these 10 viral fragments to 10 patients who recovered from mild new pneumonia.

All patients carry helper T cells that recognize the new crown virus spike protein (S protein). The S protein is like a key, and the ACE2 receptor on the cell is like a lock. The key opens the lock, allowing the virus to invade the body's cells. They also carry helper T cells that react with other novel coronavirus proteins. The research team detected virus-specific T killer cells in 70% of the subjects.

Sette said: "The immune system sees this virus and responds effectively."

In addition, on April 22nd, the immunologist Andreas Thiel of Charlie University Hospital in Germany and his colleagues published a research paper on the preprint website medRxiv (without peer review), describing them in 18 patients with neopneumonia Of 15 patients identified helper T cells targeting S protein.

The research team wanted to know whether people who were not infected with the novel coronavirus would also produce cells that fight the virus. Thiel and colleagues analyzed the blood of 68 uninfected people and found that 34% had helper T cells that recognized the novel coronavirus.

The La Jolla team detected this cross-reaction in approximately half of the stored blood samples collected between 2015 and 2018, which was much earlier than the current pandemic. The researchers believe that these cells may be caused by one of the four coronaviruses that caused a cold in the past. Because the proteins in these viruses are similar to the novel coronavirus.

Steven Varga, a virus immunologist at the University of Iowa, said: "These studies tell us that one reason that a large proportion of people can deal with this virus is that the common cold virus we have been exposed to in the past may have some immunity."

However, neither of these studies confirmed that people with cross-reactions would not be protected from infection.

Prior to these studies, researchers did not know whether T cells played a role in eliminating the novel coronavirus, or even whether they would trigger dangerous immune system overreaction.

Rasmussen said: "These papers are really helpful because they begin to define the T cell component of the immune response." But she and other scientists warned that these results do not mean that people recovering from new coronary pneumonia can be spared infection.

Crotty pointed out that in order to stimulate the production of antibodies, the vaccine against neocoronavirus needs to stimulate helper T cells. He said: "It is encouraging to see that helper T cells respond well to neocoronavirus in cases of neocoronary pneumonia."

Rachel Graham, a molecular virologist at the University of North Carolina at Chapel Hill, said the findings have other important implications for vaccine design. Most vaccines under development are designed to induce an immune response against the S protein, but both studies have determined that T cells respond to several viral proteins. This suggests that a vaccine that allows the immune system to respond to these proteins may also be more effective. "

Graham said: "It is important not to focus on just one protein."

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