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Date of publication:2021/8/2 17:10:04
Recently, a research paper titled A yeast expressed RBD-based SARS-CoV-2 vaccine formulated with 3M-052-alum adjuvant promotes protective efficacy in non-human primates published in Science Immunology, a multidisciplinary research team brought a new candidate SARS-CoV-2 vaccine. This vaccine draws on the successful experience of the hepatitis B vaccine platform, uses yeast to express the receptor binding domain (RBD) protein of the new coronavirus, and is supplemented with a new adjuvant to promote the immune response. The current experimental results of inoculating monkeys have shown good preventive effects.
The researchers emphasized in the paper that the SARS-CoV-2 vaccine being developed is suitable for large-scale production and will help meet the demand for vaccination around the world, so that more people have the opportunity to be protected. On the other hand, candidate vaccines may be very effective against emerging variants, which is essential to reduce the spread of the disease on a global scale.

In the history of humans using vaccines to prevent viral infections, the hepatitis B vaccine developed using yeast cells is an important milestone, saving countless lives. This hepatitis B vaccine, in simple terms, uses recombinant DNA technology to allow yeast to express virus-specific surface antigens, which are purified and made with adjuvants. The advantages of this technology platform include simple operation of the production system, high expression, and can be used for large-scale industrial production.
Using this experience, researchers from Emory University, Infectious Disease Research Institute (IDRI), 3M and Baylor College of Medicine collaborated to develop this SARS-CoV-2 vaccine.
The novel coronavirus-specific surface protein, the receptor-binding domain of the spike protein, was cloned and expressed in the yeast expression system as an immune antigen.  At the same time, the researchers a new adjuvant called 3M-052-alum to further boost the immune response and achieve a better immune effect. 
In monkey experiments, the SARS-CoV-2 vaccine produced with yeast has achieved significant protective effects. Compared with animals that were not vaccinated, monkeys injected with the 3-shot vaccine had a significant reduction in the amount of virus shedding from the respiratory tract when they were attacked by SARS-CoV-2, indicating that the vaccine can slow or prevent the spread of the virus, and the symptoms of pneumonia were also significantly reduced.
In addition, the researchers also compared the difference between using 3M-052-alum adjuvant and traditional alum adjuvant. This new adjuvant can stimulate the Toll-like receptor (TLR-7/8) of the innate immune system, enhance the response of CD8+ T cells, and improve the ability of T cells to kill infected cells. Experimental results show that animals vaccinated with RBD recombinant protein + new adjuvants have obtained stronger antibody response, neutralizing activity and effectiveness.
recombinant protein vaccine
▲The animal received 3 doses of recombinant protein vaccine. Compared with the alum adjuvant (blue), the vaccine (red) with the 3M-052-alum adjuvant induced a stronger antibody response and neutralizing activity (Picture source: reference [1])
Researchers believe that the enhanced T cell response seen in animal experiments also means that this vaccine is likely to provide a wide range of protection for humans, especially against the new emerging virus variation.
Professor Maria Elena Bottazzi, one of the co-corresponding authors of the study and a vaccine development expert at Baylor College of Medicine, concluded: “Our results show that the use of yeast expression platforms to produce RBD recombinant proteins is expected to meet the vaccination needs around the world. We are very pleased to see the advantage of this vaccine candidate in balancing the antibody and CD8+ T cell responses, which has not been achieved with other previous protein-based vaccine methods before."
As a reliable worldwide supplier of API intermediates, PEG derivatives and high-end biochemical reagent, Huateng Pharma supplies a variety of high purity pharmaceutical intermediates and PEG derivatives to empower drug research & development. We are able to provide the some PEG products used in COVID-19 vaccines. For more information, please read COVID-19 Vaccine Excipients.
[1] Maria Pino et al., (2021) A yeast expressed RBD-based SARS-CoV-2 vaccine formulated with 3M-052-alum adjuvantpromotes protective efficacy in non-human primates. Science Immunology
[2] New COVID-19 vaccine candidate provideseffective option for low- to mid-income countries. Retrieved July 19, 2021

Related articles:
[1] Nature: Vaccine Development Timeline - 20 Major Milestones   
[2] COVID-19 Vaccine Success Accelarates R&D of mRNA-based Cancer Vaccines