With the Covid-19 vaccination campaign in full swing around the world, French researchers are developing an innovative vaccine that looks promising for boosting immunity in recovering or already vaccinated people whose immune response is starting to wane. But it could also be useful for vaccinating children. Clinical trials in humans will start in 2022.
Further research is currently underway in laboratories to improve the available vaccines and to develop new, effective and innovative ones to fight the pandemic and its variants to protect as many people as possible.
Researchers from Inserm and the Vaccine Research Institute (VRI) of the University of Paris-Est Créteil, CEA-Jacobi, and the University of Paris-Saclay have developed a vaccine targeting the main cells of the immune system, the dendritic cells. The vaccine has been shown to be effective in preclinical models, in which a protective immune response against the virus was achieved. The results were published on 1 September in the journal Nature Communications.
Almost 2 years after the start of the Covid-19 pandemic, several vaccines have already been approved around the world thanks to unprecedented research efforts. These first-generation vaccines offer much hope and are a key pillar in the fight against the virus. However, questions remain about the duration of the immune response or the need for repeated vaccination. To bring the pandemic back under control, billions of people would need to be vaccinated. Preparing the doses needed to protect the entire global population is a major challenge. For these reasons, research is continuing to develop new vaccine candidates to meet all these challenges.
Researchers are working on a vaccine consisting of a monoclonal antibody directed against immune cells circulating in the body, called dendritic cells. These cells play a key role in boosting the immune system by their ability to mount a strong and sustained antibody and cellular response, as the team has shown in other infection models. The monoclonal antibody is coupled to the SARS-CoV-2 protein, which stimulates dendritic cells. In fact, this dendritic cell-targeted vaccine technology is currently in Phase I clinical trial to evaluate the safety and immunogenicity of a preventive HIV vaccine.
The vaccine provides better protection against reinfection than natural immunity
In a study published in Nature Communication, researchers first examined the ability of their vaccine candidate to elicit a “booster” anti-Covid-19 response in models using recovering animals that had been infected with SARS-CoV-2 six months earlier. They showed that the vaccine is well tolerated and effective and that it strongly increases the level of neutralizing antibodies. When re-exposed to the virus, the recovering vaccinated animals did not acquire a detectable viral load or the virus disappeared in a shorter time (less than three days) compared to unvaccinated recovering animals or previously uninfected control animals. Thus, a single dose of this vaccine provides better protection against reinfection than natural immunity. In addition, vaccinated animals were protected against pulmonary complications after infection.
Researchers have already adapted the vaccine candidate to be effective against the new variants discovered in recent months. In the laboratory, antibodies produced by the vaccine are able to neutralize the alpha variant (B.1.1.7) very effectively and also the beta variant (B.1.351) to a considerable extent. The vaccine, developed on the basis of the first circulating strain in the early 2020s, will therefore be able to generate an antibody response that will also neutralize the new variants.
In summary, this study shows that a single administration of the candidate vaccine without adjuvant is able to re-stimulate the production of neutralizing antibodies that can fight the virus when it re-infects. This provides better protection against reinfection than natural immunity. This vaccine could therefore be added to the arsenal of vaccines against SARS-CoV-2 already available. The results presented in this study suggest that it could be particularly useful for people in recovery or previously vaccinated whose immune response is compromised to boost their immunity. This vaccine could also be useful for vaccinating vulnerable individuals or children. Clinical trials are planned for 2022 in people who are recovering or have already been vaccinated with a first-generation vaccine. They will also be carried out in people who have never been in contact with the vaccines or the virus.
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