Good news
The study of the immune response to coronavirus has brought good news to the developers of the vaccine
Sofia Jabotinskaya, Naked Science
Scientists around the world are trying to develop a vaccine against coronavirus and predict how the pandemic will develop until a reliable preventive remedy for Covid-19 appears. But so far, no one has given answers to two important questions on which the creation of a vaccine and the situation with infected people depend: is the immune system capable of providing a significant and lasting response to SARS-CoV-2? Can exposure to other coronaviruses provide any immunity to SARS-CoV-2?
A study published in Cell (Grifoni et al., Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexpected individuals) gives a positive answer to the first of these questions. It details aspects of the immune response in 20 adults who have recently recovered from coronavirus pneumonia. The results of the study show that the body's immune system is able to recognize SARS-CoV-2 in several different ways. This dispels fears that the virus is able to evade the immune response and make the development of a vaccine useless.
"What we see is a stable T–cell response to spike proteins [viral particles] and other proteins," says one of the authors of the study, biologist Alessandro Sette. "People were very concerned that Covid–19 allegedly does not cause immunity, and reports of re-infection have increased these fears, but now the knowledge that the average person develops a solid immune response should largely calm the anxiety," adds Sette's colleague, Professor Shane Crotty.
In their earlier studies, Crotty and Sette, using bioinformatics methods, predicted which fragments of SARS-CoV-2 virus particles have sufficient immunogenicity to activate T-lymphocytes. In the new work, scientists tested how well T cells isolated from Covid-19 patients recognize predicted protein fragments or peptides. "We specifically decided to study people with a normal course of the disease and who do not need hospitalization in order to provide a reliable assessment of what a normal immune response looks like, since the virus can cause some very unusual things in individuals," adds Alessandro Sette.
All subjects showed a pronounced CD4-T-cell immune response – that is, activation of the so-called T-helper cells in response to the antigen. T-helper cells are cells that recognize an antigen and activate other types of cells of the immune system: in particular, B–lymphocytes that produce antiviral antibodies. Also, all patients were found to have virus-specific CD-8 T lymphocytes, or T-killers, which destroy the cells of the body damaged by viruses.
The researchers also studied the reaction of T cells in blood samples that were collected between 2015 and 2018, long before the start of the Covid-19 pandemic. Lymphocytes from many samples had a noticeable reactivity against SARS-CoV-2, although they had never been exposed to this pathogen.
Scientists attribute this fact to the fact that people from whom blood was taken had previously encountered less dangerous types of coronaviruses. However, it is not yet clear exactly what level of immune protection is provided by the observed cross-reactivity of T-lymphocytes. "Given the severity of the ongoing Covid-19 pandemic, any degree of cross-reactive immunity can have a significant impact on the overall course of the pandemic and is a key detail that epidemiologists should take into account when making forecasts," the authors conclude.
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