New yeast-derived COVID vaccine could improve global access

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A new protein-based vaccine could help give the world’s less affluent countries access to COVID-19 vaccines. Animal experiments have shown that the new vaccine stimulates a strong immune response and protects against viral infections.

Although the speed at which safe and effective vaccines for COVID-19 have been developed, tested, and rolled out in many countries is a significant achievement, many people around the world still do not have access to COVID vaccines.

Vaccine equity remains a key challenge in ending the COVID-19 pandemic. Just as the most vulnerable members of the community within countries often lack access to vaccines, wealthy nations around the world tend to be the most vaccinated.

Researchers at Massachusetts Institute of Technology (MIT) and Beth Israel Deaconess Medical Center in the US have developed a new protein subunit vaccine against COVID that they hope will help close this gap in vaccine equity.

It contains fragments of the SARS-CoV-2 spike protein found on the virus surface – the same protein that most existing vaccines target.

The subunits of the spike protein are arranged on a “virus-like particle” made up of surface antigens from another virus, hepatitis B. Adding the hepatitis B antigen makes the vaccine more immunogenic, meaning it elicits a stronger immune response.

“Protein-based vaccines are a low-cost, established technology that can provide a steady supply and are accepted in many parts of the world,” says J. Christopher Love, a professor of chemical engineering at MIT and one of the study’s senior authors.

The research team that began work on the COVID vaccine in early 2020 aimed to optimize both the ease of vaccine manufacture and the protection against disease.

Your vaccine can be made using yeast cells, which are easier to grow and work with than the cultured mammalian cells typically used to make protein subunit vaccines. The yeast can produce both the SARS-CoV-2 spike protein fragment and the hepatitis B particle.

“One of the key things that differentiates our vaccine from other vaccines is that the facilities to produce vaccines in these yeast organisms already exist in parts of the world where the vaccines are needed most today,” explains Neil Dalvie, a PhD student at MIT who was one of the paper’s lead authors.

If proven safe and effective in humans, the vaccine should be relatively cheap and easy to produce. It can also be stored in an ordinary refrigerator compared to mRNA vaccines which require extremely low storage temperatures. Both features should help make COVID vaccination more accessible to countries that currently don’t have access.

Another advantage of the vaccine design is that it is easy to incorporate spike protein mutations or new antigens into the virus-like particle. That means the researchers’ vaccine framework could be useful in efficiently developing vaccines that target new strains or viruses.

The team has already updated its vaccine candidates to include, for example, mutations found in the delta and lambda variants of SARS-CoV-2.

“We could make mutations that were seen in some of the new variants, add them to the RBD but keep the overall framework and develop new vaccine candidates,” says Sergio Rodriguez-Aponte, another lead author and also an MIT graduate student.

“This shows the modularity of the process and how efficiently you can edit and create new candidates.”

“Basically, this modularity makes it possible to consider adapting to new variants or providing a pan-coronavirus protection booster,” adds Love.

The vaccine is currently being mass-produced by the Serum Institute of India and is in human clinical trials.

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