The key to a universal vaccine is the mosaic nanoparticles with many different viral fragments clustered near their surface. You are more likely to find B cells in the immune system, which generate specific antibodies, at least and bind to some of these conserved parts of the virus, which remain unchanged in the new variants. Thus, B cells would make the antibodies effective even against variants not seen before.
To make the mosaic nanoparticles, Cohen, Björkman and their collaborators selected proteins from the surfaces of 12 coronaviruses that have been identified by other research groups and detailed in the scientific literature. These included the viruses that caused the first SARS outbreak and the virus that caused COVID-19, as well as non-human viruses found in bats in China, Bulgaria and Kenya. For good measure, they also dumped the coronavirus found in the scaly anteater known as pangolins. All strains have already been genetically sequenced by other groups and share 68 to 95% of the same genomic material. Thus, Cohen and Björkman can be relatively certain that some other virus may share some parts of each distinct spike protein they choose to place on the outside of their nanoparticle.
Then they made three vaccines. One, for comparison purposes, contained all 60 slots occupied by particles taken from a single strain of SARS-CoV-2, the virus that causes covid-19. The other two are mosaics, each one displaying a mixture of protein fragments taken from eight of 12 strains of coronaviruses from bats, humans and pangolins. The remaining four strains of the vaccine were excluded so the researchers could test whether it would protect them anyway.
In mouse studies, all three vaccines correlated well with the COVID-19 virus. But when Cohen sat down to consider his results, he was shocked at how robustly the nano-mosaic particles performed when exposed to different strains of coronavirus not represented at the altitudes they were exposed to.
The vaccine was spurring the production of armies of antibodies to attack the parts of the proteins that changed less between the different strains of the coronavirus — the conserved fragments, in other words.
In recent months, Bjorkman, Cohen and their collaborators have been testing the vaccine on monkeys as well as rodents. So far, it seems to be working. Some experiments proceeded slowly because they had to be conducted by outside collaborators in special, high-security biosafety laboratories designed to ensure that the highly contagious viruses did not escape. But when the results finally appeared in Science, the paper received widespread attention.
Other promising efforts are running in parallel. at the University of Washington Institute of Protein Design, biochemist Neil King He custom engineered hundreds of new types of nanoparticles, “sculpting them atom by atom,” he says, in such a way that the atoms self-assemble, attracted to the correct positions by other pieces designed to carry complementary geometric and chemical charges. In 2019, NIH collaborator King’s Barney Graham was the first to successfully demonstrate that mosaic nanoparticles can be effective against different influenza strains. King, Graham and their collaborators have formed a company to modify and develop the technology, and they have the nanoparticle influenza vaccine in phase I clinical trials. They are now deploying the new technology against a variety of different viruses, including SARS-CoV-2.
Despite recent promising developments, Bjorkman warns that her vaccine likely won’t protect us from all coronaviruses. There are four families of coronaviruses, each slightly different from the other, and some target completely different receptors in human cells. Thus, there are fewer locations conserved across coronavirus families. The vaccine from her lab is focused on a universal vaccine for SARPs, the subfamily that contains SARS coronaviruses and SARS-CoV-2.