Dendritic cells play a key role in the immune system, through their role in the initiation of the immune response. Targeting vaccines to these cells increases antibody and cellular responses, as demonstrated by the CEA-Jacob team in other infection models (such as HIV).

Using convalescent animal models having contracted SARS-CoV-2 six months earlier, the scientists studied the ability of a vaccine – consisting of a monoclonal antibody that targets a molecule expressed on the surface of dendritic cells (CD40) and fused to a SARS-CoV-2 peptide – to induce anti-Covid-19 recall responses.

Their work shows that this vaccine is well-tolerated and effective, inducing a strong increase in neutralizing antibodies. When re-exposed to the virus, both convalescent and vaccinated animals had either an undetectable viral load or were able to clear the virus in a shorter period of time (less than three days) than unvaccinated convalescent animals or control animals free of any previous infection. These animals were also protected from pulmonary complications.

Furthermore, the researchers have adapted this vaccine candidate to make it effective against the new variants identified in recent months (alpha and beta).

Their study shows that the administration of a single dose of the vaccine, without adjuvant, stimulates a second time the production of neutralizing antibodies that are able to control the virus during a reinfection. This vaccine candidate could therefore complement the arsenal of anti-COVID vaccines already available by being administered to convalescent or previously vaccinated individuals whose immune response has begun to decline. Clinical trials are planned for 2022 to evaluate convalescent patients or those vaccinated with a first-generation vaccine.