Vaccine against COVID-19: an avenue for longer-lasting protection

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T lymphocytes play an important role in the development of immune memory. Their
T lymphocytes play an important role in the development of immune memory. Their DNA is damaged by a cascade of reactions triggered by an SARS-CoV-2 protein. This damage may explain why the body is unable to mount a lasting immune response. - NIH/NIAID
A molecule already used for different purposes in humans could improve post-vaccination immune memory

The RNA vaccine against COVID-19 has many qualities, but it has one shortcoming that has escaped no one’s notice: the protection it confers is short-lived, hence the need for frequent booster doses. A study recently published in the Journal of Allergy and Clinical Immunology by a research team from France and Laval University suggests that this weakness of the vaccine may be due to a cascade of reactions that affect cells of the immune system, the T lymphocytes. "We believe that by blocking this cascade of reactions, we could improve immune memory and significantly extend the duration of protection conferred by this vaccine", says Jérôme Estaquier, the study’s leader, a professor at Université Laval’s Faculty of Medicine and researcher at the Centre de recherche du CHU de Québec - Université Laval.

Remember that the COVID-19 vaccine contains RNA that controls the production of a virus protein, the spicule protein (S), by human cells. "The body then mounts an immune response to prevent the development of the disease when confronted with the virus", explains Professor Estaquier.

In a previous study, his team demonstrated that, in people suffering from severe COVID-19, a cascade of reactions triggered by protein S led to a weakening of the immune response linked to the death of T lymphocytes. "As the vaccine induces the production of protein S by the body, we wanted to know whether the same cascade of reactions was present, at least temporarily, in people who are vaccinated", explains the researcher.

The Franco-Quebec team followed 30 people who had just received a COVID-19 vaccine for 28 days to measure various parameters of their immune response. The data show that, as expected, protein S production increases in the days following vaccination. It peaked on day 14 and almost completely disappeared after 28 days.

"The increase in protein S triggers the same cascade of reactions observed in people with COVID-19," summarizes Professor Estaquier. One of the steps in this cascade is the production of reactive oxygen derivatives that damage the DNA of T lymphocytes. We believe this damage could explain why the body is unable to build up a lasting immune memory, and why boosters are needed to maintain protection against the virus."

"A good part of the population doesn’t want to be vaccinated every six months against COVID-19. If we want to maintain high vaccination rates, we have to listen to the needs of the population and find ways to correct this problem."

-- Jérôme Estaquier Estaquier’s team now intends to test this hypothesis using an inhibitor of reactive oxygen derivatives, N’acetylcysteine, as an adjunct to vaccination. "This amino acid has already been used for various purposes in humans. We’re going to administer it orally to people who have just received the vaccine. This will enable us to assess its efficacy in protecting T lymphocytes and thus improve the duration of protection conferred by vaccination."

The COVID-19 vaccine is a very good vaccine, insists Professor Estaquier, but the short duration of protection it confers is a major drawback. "A large proportion of the population does not want to be vaccinated every six months against COVID-19. If we want to maintain high vaccination rates, we have to listen to the needs of the population and find ways to correct this problem."