As the world struggles with COVID vaccine production bottlenecks and scaling issues, a team from Northwestern University synthetic biologists have developed a high-yield vaccine technology, increasing production of protein-based vaccines by a factor of five.
Scaling up COVID vaccine production has proved extremely challenging. Adenovirus vaccines such as AstraZeneca’s need to be cultured in 2000 litre tanks containing human cells and then extracted, while mRNA vaccines like that produced by Pfizer requires very careful mixing, as well as components and only a few companies have the skills to produce them. The promising protein subunit vaccines such as Novavax’s offering may be easier to scale up, but also require specific adjuvant, which uses saponin from the bark of a Chilean tree, Quillaja saponaria, which is also used in other vaccines.
Earlier this year, the researchers introduced a new biomanufacturing platform that can quickly make shelf-stable vaccines at the point of care, ensuring they will not go to waste due to transportation or storage problems. In this new study, the team found that enriching cell-free extracts with cellular membranes—the components needed to made conjugate vaccines—massively boosted yields of its freeze-dried platform.
The new technology can produce 40 000 doses per litre per day of antibiotics or vaccines, costing about $1 per dose. At that rate, the team could use a 1000 litre reactor to generate 40 million doses per day, reaching 1 billion doses in less than a month.
“Certainly, in the time of COVID-19, we have all realized how important it is to be able to make medicines when and where we need them,” said study leader Michael Jewett, a professor of chemical and biological engineering at Northwestern. “This work will transform how vaccines are made, including for bio-readiness and pandemic response.”
The new manufacturing platform—called in vitro conjugate vaccine expression (iVAX)—is made possible by cell-free synthetic biology, a process where a cell’s outer wall (or membrane) is removed, and its internal machinery repurposed. This repurposed machinery is then placed in a test tube and freeze-dry it. The cell-free system is activated by the addition of water, turning it into a catalyst for making usable medicine when and where it’s needed. With a shelf-life of over six months, the platform eliminates the need for complicated supply chains and extreme refrigeration, making it extremely valuable for remote or low-resource settings.
In a prior study, Jewett’s team used the iVAX platform to produce conjugate vaccines to protect against bacterial infections, repurposing molecular machinery from Escherichia coli to make a single dose of vaccine in an hour, at $5 per dose.
“It was still too expensive, and the yields were not high enough,” Prof Jewett said. “We set a goal to reach $1 per dose and reached that goal here. By increasing yields and lowering costs, we thought we might be able to facilitate greater access to lifesaving medicines.”
Prof Jewett and his team found that the cell’s membrane, which is typically discarded in cell-free synthetic biology, was key to solving this. When broken apart, membranes naturally reassemble into vesicles, spherical structures that still carry important molecular information. Studying these vesicles, the researchers discovered that increasing vesicle concentration could be useful in making components for protein therapeutics such as conjugate vaccines, which work by attaching a sugar unit—that is unique to a pathogen—to a carrier protein.
Normally attaching the sugar unit to the protein is very complex, but the researchers found that the cell’s membrane contained machinery that enabled the sugar to more easily attach to the proteins. When they enriched vaccine extracts with this membrane-bound machinery, the researchers significantly boosted usable vaccine yields.
“For a variety of organisms, close to 30% of the genome is used to encode membrane proteins,” said study co-author Neha Kamat, who is an assistant professor of biomedical engineering at McCormick and an expert on cell membranes. “Membrane proteins are a really important part of life. By learning how to use membrane proteins effectively, we can really advance cell-free systems.”
Journal information: Improving cell-free glycoprotein synthesis by characterizing and enriching native membrane vesicles, Nature Communications (2021). DOI: 10.1038/s41467-021-22329-3