Covid-19 infection: towards protection for several years?

The adaptive antiviral response. The body has two lines of protection against viruses. The innate immune response provides an initial defense and the adaptive response allows for a more effective response to further exposure. The latter develops several times:

• Within two to three weeks of infection, the body makes antibodies against the virus to neutralize infected cells and the virus in the body.

• These antibodies, which patrol the blood and mucous membranes of patients, persist at an elevated level for a few weeks or months before gradually decreasing.

• A subset of specialized immune cells against the virus do not degenerate but remain viable in the long term, ready to restart the immune response in the event of a similar new exposure: memory cells.

This classic scheme had yet to be validated for Covid-19. While the presence of antibodies in the blood is easy to detect with routine tests, immune cells are much more difficult to detect. Hence the interest in the work of immunologist Shane Crotty (La Jolla) and his colleagues, which shows how the response to Sars-CoV-2 infection is progressing as well as in biology textbooks. And that this immunological memory persists for several months at a high level.

In case of reinfection. The immune cells that make up the immunological memory are of different types: B lymphocytes are intended to produce neutralizing antibodies in bulk, CD4 T lymphocytes to produce chemical messengers to encourage them, and CD8 T lymphocytes to attack directly. virus-infected cells.

In case of new exposure to Sars-CoV-2, this adaptive response takes a priori a few days to develop, while the memory cells multiply. This is probably too slow to prevent re-infection as the virus has time to replicate in the upper airways. On the other hand, it is very plausible that the spread of the virus to other organs is limited, resulting in a reduction in severity.