Scientists have developed a new COVID-19 protein subunit vaccine using engineered yeast, proving an alternative to RNA vaccines.
Although more than 5 billion people across the world have received a COVID-19 vaccine, this only equals 65.9% of the world’s population. Due to the high cost and complex storage requirements, most of the vaccines have largely gone to high-income countries. As a result, only 15% of the population in low-income countries have received at least a single dose of a COVID-19 vaccine. Therefore, researchers at MIT and Beth Israel Deaconess Medical Center have developed a low-cost and easy-to-store COVID-19 vaccine using yeast. The new candidate is meant to provide an alternative to existing RNA vaccines.
There’s still a very large population that does not have access to Covid vaccines. Protein-based subunit vaccines are a low-cost, well-established technology that can provide a consistent supply and is accepted in many parts of the world.
Professor J. Christopher Love, study author
What Are Protein Subunit Vaccines?
Protein subunit vaccine is a type of vaccine that contains fragments of viral proteins to trigger an immune response. Unlike other vaccines, it is easy to manufacture and does not require ultracold storage temperatures. According to the study author Professor J. Christopher Love, subunit vaccines can help provide cost-effective options in countries where cost remains a challenge.
The team designed the vaccine using the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. Unlike the spike protein, RBD can elicit multiple effective neutralizing antibodies; however, the fragment alone is not enough to produce a strong immune response. Therefore, researchers coated the hepatitis B surface antigen with multiple RBD fragments.
Furthermore, they designed the protein subunit so the yeast Pichia pastoris can easily manufacture it. Thus, each of the new COVID-19 vaccine components, RBD protein and hepatitis B antigen, can be produced separately by the yeast. Moreover, bioreactors around the world already use Pichia pastoris for producing vaccines.
One of the key things that separates our vaccine from other vaccines is that the facilities to manufacture vaccines in these yeast organisms already exist in parts of the world where the vaccines are still most needed today.
Neil Dalvie, study author
According to the study published in Science Advances, the protein subunit vaccine fared well in an animal trial containing macaques. The researchers noted antibody levels similar to those produced by existing vaccines such as the Johnson & Johnson vaccine. Moreover, vaccinated animals exposed to SARS-CoV-2 had lower viral loads than the unvaccinated group.
The Serum Institute of India is currently producing the vaccine and plans to run a clinical trial in Africa.
Reference:
Dalvie, N.C., et al. (2022) SARS-CoV-2 receptor binding domain displayed on HBsAg virus–like particles elicits protective immunity in macaques. Science Advances. doi.org/10.1126/sciadv.abl6015.
