In a new study, researchers found n experimental messenger RNA (mRNA)-based vaccine against COVID-19 elicits protective immune responses in mice and non-human primates.
Two injections of the vaccine were sufficient to induce robust immunity, completely preventing COVID-19 infection in mice.
The research was conducted by a team at the Beijing Institute of Microbiology and Epidemiology.
The mRNA-based vaccines are attractive options for protecting against SARS-CoV-2 because they can be rapidly designed and manufactured at a large scale within weeks.
Moreover, preclinical studies have demonstrated that mRNA-based vaccines induce potent and broadly protective immune responses against various pathogens with an acceptable safety profile.
In the study, the team developed a vaccine consisting of mRNA that encodes the receptor-binding domain (RBD) of the spike (S) protein, which is located on the surface of SARS-CoV-2.
The vaccine, named ARCoV, is encapsulated in lipid nanoparticles, which improves delivery into tissues.
The researchers injected ARCoV into the muscle tissue of 16 mice and provided a booster shot two weeks later.
The vaccine elicited the production of high levels of neutralizing antibodies, which protect host cells by preventing the virus from interacting with them.
These antibodies were cross-reactive, offering broad protection against three different strains of SARS-CoV-2.
The team found mice that received two doses of ARCoV and were exposed to SARS-CoV-2 35 days later showed no signs of viral RNA in the lungs and no lung damage or inflammation.
Results from 20 monkeys showed that two ARCoV doses induced a virus-specific T cell response and the production of neutralizing antibodies at levels that far exceed those seen in most recovered COVID-19 patients.
Moreover, none of the vaccinated animals experienced adverse effects.
The researchers also stored the vaccine at various temperatures for one, four, or seven days, injected it into mice, and visualized its tissue distribution.
The results showed that the vaccine was effectively delivered to tissues, achieving the same high level of expression after being stored at room temperature for one week, without any signs of decreased activity.
The team says the robust protection observed in the present studies and the clear immune correlates of protection pave the path forward for future COVID-19 vaccine development in humans.
The researchers are currently evaluating the long-term stability of ARCoV.
One author of the study is Cheng-Feng Qin of the Beijing Institute of Microbiology and Epidemiology.
The study is published in Cell.
Copyright © 2020 Knowridge Science Report. All rights reserved.
