In addition to antibodies, T cells are very important for the defense against Sars-CoV-2 viruses. In contrast to antibodies that attach to the spike protein, T cells recognize the virus as a whole and fight it as a pillar of the immune system. However, while antibodies decrease over time, T cells are retained – they are also called memory cells because they store an immune reaction that has been learned and can be used again if necessary.
British researchers from Imperial College London have now been able to show that T cells, which were created by an infection with cold viruses, can also protect against Covid-19. The study examined the concentrations of cross-reactive T cells – i.e. T cells that were originally created against other viruses, but are also effective against Sars-CoV-2. To do this, 52 household contacts analyzed positive Covid 19 cases shortly after contact to determine whether they developed an infection.
It showed that the 26 people who did not develop an infection had significantly higher levels of these T cells from previous colds than people who became infected. “We have found that a high proportion of pre-existing T cells, which the body generates when infected with other human coronaviruses such as the common cold, can protect against Covid-19 infection,” said study author Rhia Kundu.
These findings could be relevant for the development of new vaccines. Current Covid vaccines target the spike protein, which, however, mutates regularly – as the new Omikron variant shows, this can reduce the effectiveness of vaccines. “In contrast, the internal proteins that are attacked by the protective T cells we have identified mutate much less,” said Professor Ajit Lalvani, co-author of the study.
The proteins are retained despite mutations. According to the researchers, vaccines designed for this could therefore elicit largely protective T-cell responses to protect against current and future virus variants.