As the public has seen during the testing of lifesaving COVID-19 vaccines, refrigeration is one key to their distribution. According to an article from the UMass News Office, Associate Professor Sarah Perry of the Chemical Engineering Department at UMass Amherst has teamed up with Caryn Heldt, director of the Health Research Institute at Michigan Technological University and professor of chemical engineering, to develop a method using proteins to keep vaccines stable without the need to refrigerate them.
When asked if their new method could be applied to address some of the refrigeration challenges associated with the COVID-19 vaccines, Perry explained that “While it is possible that our method might work for COVID-19, vaccines can come in very different forms. Some are inactivated viruses, some are particular proteins from the virus surface, while others (as highlighted by the work of Pfizer and Moderna) are RNA-based vaccines. Our recent work focused on viruses, so further study would be needed to understand how our approach could be applied to RNA-based vaccines.”
Statistics from the World Health Organization suggest that half of vaccines are wasted annually because they aren’t kept cold. Typical vaccine solutions contain a lot of salt or sugar, which serve as natural preservatives to help stabilize the vaccine, in addition to refrigeration.
The viruses in vaccines, which train cells to identify and fight viral invaders, must be kept cold to keep them from bursting apart. The typical shipping temperature for vaccines ranges from 2 to 8 degrees Celsius (35 to 47 degrees Fahrenheit). However, many potential COVID-19 vaccines require even colder temperatures, as was recently revealed during the rollout of potential COVID-19 vaccines in the late stages of testing by Pfizer and Moderna.
Perry and Heldt have developed a way to mimic the body’s environment in vaccines using a process called complex coacervation. Rather than relying on refrigeration, Perry and Heldt tap another method to keep viruses stable; a pioneering technique which they refer to as “crowding.”
With this “crowding” technique, Perry and Heldt use polypeptides — synthetic proteins — that have positive or negative charges. According to the News Office story, when these charged peptides are put in solution, “they stick together and form a separate liquid phase, a process called complex coacervation. The liquid wraps around virus capsids, holding the virus material together like a burrito’s tortilla.”
Perry said that “These coacervate materials are something that we actually see all of the time in our daily lives. Many shampoos undergo coacervation. When you put the shampoo onto your wet hair, the water that is present dilutes the shampoo, causing it to phase separate and facilitating the removal of dirt and oil from your hair.”
Complex coacervation works for nonenveloped viruses, which have no lipid, or fatty layer, around them. Nonenveloped viruses include polio, rhinovirus (which causes the common cold), and hepatitis A.
Perry and Heldt received a $400,000 developmental research grant in March of 2020 from the National Institutes of Health (NIH) to continue their research through early 2022, which includes exploring ways to reduce salt concentrations (used in the vaccine to break apart the coacervate phase when it is injected by altering peptide sequences).
Additionally, the two chemical engineers are working on ways to apply complex coacervation to enveloped viruses — like SARS-CoV-2 — which require a balance of tightness and compartmentalization in the lipid layer in a way nonenveloped viruses do not.
“Looking forward, we want to think more about the specific materials that we use in our coacervates,” Perry said. “Crowding alone isn’t a universal strategy to improve virus stability. We need to understand how different polymers interact with our viruses and how we can use this to create a toolbox that can be applied to future challenges.”
As the News Office story observed, “Solving the cold storage conundrum promises to improve access to vaccinations against viruses. Bypassing the cold chain with polypeptides and innovative chemical engineering stands to improve health care and reduce medical emergencies around the world.” (December 2020)