Nanoparticle vaccine could protect against a variety of coronaviruses

The SARS-CoV-2 virus belongs to the coronavirus family. There are many types of coronavirus which circulate in animal populations and have the potential to “jump” into the human population like SARS-CoV-2. Researchers in the CalTech laboratory of Professor Pamela Björkman are working on developing vaccines for a range of coronaviruses, with their sights set on preventing future pandemics.

The team has customised a protein-based nanoparticle with pieces of different coronaviruses attached to it.

The vaccine platform – a mosaic nanoparticle – was initially developed by University of Oxford researchers. The nanoparticle is shaped like a cage and made up of 60 identical protein subunits, each with a small protein tag. The CalTech researchers took fragments of the spike proteins of different coronaviruses (receptor binding domains) and engineered each to have a protein tag that would bind to those on the cage. When these viral pieces were mixed together with the nanoparticle, each virus tag attached to a tag on the cage, resulting in a nanoparticle covered with spikes representing different coronavirus strains.

When injected into mice, this induced a diverse antibody response, with antibodies which react to a range of coronaviruses including some not present on the surface of the nanoparticle.

This suggests that presenting the immune system with multiple coronaviruses, the immune system could learn to recognise common features of coronaviruses. This may react to a newly emerging coronavirus which would otherwise risk causing another pandemic.

Next, the team will examine whether this nanoparticle vaccine prevents viral infection and symptoms in animal models.

“If we can show that the immune response induced by our nanoparticle technology indeed protects against illness resulting from infection, then we hope that we could move this technology forward into human clinical trials, though there are a lot of steps that need to happen between now and then,” said graduate student Alex Cohen, who led the project. “We don’t envision that this methodology would replace any existing vaccines, but it’s good to have many tools on hand when facing future emerging viral threats.”

Björkman added: “Unfortunately SARS-CoV-2 is unlikely to be the last coronavirus to cause a pandemic. Alex’s results show that it is possible to raise diverse neutralising antibody responses, even against coronavirus strains that were not represented on the injected nanoparticle.”

“So, we are hopeful that this technology could be used to protect against future animal coronaviruses that cross into humans. In addition, the nanoparticles elicit neutralising responses against SARS-CoV-2, so it could be possible to use them now to protect against Covid-19 as well as other coronaviruses with pandemic potential.”