Do new coronavirus variants resist human body defenses? Indeed, the mutated forms of the virus may be partially resistant to antibody defense. That in turn would call into question some current vaccination approaches. But there is good news: Concern about this has led to a new boom in research, because in addition to antibodies there are other forms of the body’s own virus defense. In particular, scientists hope that T cells – a group of immune cells that can target and destroy virus-infected cells – could offer some immunity to Covid-19, even if antibodies were to become less effective in fighting the disease.
Teams are currently analyzing the available data and looking for evidence that T cells could help maintain lasting immunity. “We know that antibodies are likely to be less effective, but the T cells may save us,” says Daina Graybosch, a biotechnology analyst at SVB Leerink investment bank in New York City. “It makes biological sense. We don’t have the data, but we can hope. ”
In addition to antibodies, the immune system also produces a battalion of T cells that can fight viruses. Some of them, “killer” T cells or CD8+Called T cells, they look for cells that are infected with the virus and destroy them. Others, the helper T cells or CD4+T cells, are important for various immune functions, including stimulating the production of antibodies and killer T cells.
Mild courses thanks to T cells
T cells do not prevent infection because they only become active after a virus has entered the body. But they’re important in fighting an ongoing infection. In the case of Covid-19, killer T cells could make the difference between a mild and a severe infection, says Annika Karlsson, immunologist at the Karolinska Institute in Stockholm. “If they are able to kill the virus-infected cells before they spread from the upper respiratory tract, that affects the disease,” says Karlsson.
The y could also limit transmission by reducing the viral load in an infected person.
T cells could also be more resistant to threats from new variants than antibodies. As studies by immunologist Alessandro Sette of the La Jolla Institute for Immunology in California and his colleagues have shown, people infected with Sars-CoV-2 typically generate T cells that target at least 15 to 20 different fragments of coronavirus proteins aim. However, which protein snippets to target can vary widely from person to person. As a result, a large variety of T cells are formed in the population. “This makes it very difficult for the virus – unlike the antibodies – to mutate and thus not be recognized by cells,” says Sette.
Laboratory tests have shown that the variant 501Y.V2 – also known as B.1.351 – identified in South Africa is partially resistant to antibodies that were formed against earlier coronavirus variants. Researchers then wondered whether T cells could be less susceptible to its mutations.