The findings were published in Science Advances on Dec. 1, 2021.

“At the time we started this project, the first COVID-19 vaccines were just getting rolled out, and there was a lot of news about how they needed ultra-cold storage, and how that was a huge logistical challenge. Especially in low- and middle-income countries, it may not always be feasible to have that type of refrigeration infrastructure,” says Jonathan F. Lovell, PhD, associate professor of biomedical engineering and senior author on the study. “So we started to look at whether we could make a thermostable COVID-19 vaccine using a liposome-based vaccine platform that we worked on previously.”

Freeze-drying is a method for removing water from a product. First, you freeze the item you’re trying to dehydrate, causing any water in it to become ice. Then, you remove the ice through a process called sublimation, in which ice turns directly into vapor under low pressure.

A vaccine that employs the freeze-dried liposomes is still a long way off. But if developed successfully, dehydrated doses could be shipped and stored at room temperature, eliminating logistical problems associated with some of the most popular existing vaccines for the disease.

The new study focuses on a liquid injection that consists of ingredients including water; specialized liposomes carrying a synthetically produced version of the spike protein of the COVID-19 virus; and a small amount of sugar, which helps to protect the formula during the freeze-drying process.

The freeze-dried product — which looks a bit like cotton candy — is mint green in color.

“Upon dehydration, the formula was stable at elevated temperatures, and we showed that it can withstand room temperatures and even higher temperatures for at least a week,” says Moustafa Mabrouk, a doctoral student in biomedical engineering and first author on the study. “After that, we reconstituted the formula by adding water. When we tested this in mice, it induced effective antibody responses and offered protection against the COVID-19 virus.”

“The COVID-19 pandemic stimulated interest in potent and thermostable SARS-CoV-2 vaccines — and Dr. Lovell’s research team was forward-thinking in their approach of using a liposome-based platform to work on this formula,” says Allison Brashear, MD, vice president for health sciences and dean of the Jacobs School of Medicine and Biomedical Sciences.

Co-authors from the Department of Biomedical Engineering are:

• Wei-Chiao Huang, PhD, postdoctoral associate of biomedical engineering
  
• Breandan Quinn, research technician

Other co-authors are from:

• Hospital for Sick Children (SickKids) Research Institute in Toronto
• McGill University
• Pennsylvania State University
• Texas Biomedical Research Institute
• University of the Basque Country in Spain
• University of Toronto

The research was supported by the U.S. National Institutes of Health; the European Union’s Horizon 2020 research and innovation program under a Marie Sklodowska-Curie grant; the CIFAR Azrieli Global Scholars Program; the Ontario Early Researcher Awards program; and the Canada Research Chairs program.

The specialized liposomes examined in the Science Advances study are being researched for potential use in vaccines against multiple diseases. The liposomes were originally developed in Lovell’s lab and have been licensed by the university to POP Biotechnologies Inc. (POP BIO), a startup company that Lovell co-founded. (Huang is also a POP BIO employee.)

A COVID-19 vaccine candidate that relies on POP BIO’s liposome-based vaccine delivery system is in human trials in South Korea. That vaccine candidate, called EuCorVac-19, is under development by POP BIO and South Korean biotech company EuBiologics. EuCorVac-19 has slightly different ingredients from the vaccine formula studied in the Science Advances paper.

“We have not tested freeze-drying on the EuCorVac-19 vaccine,” Lovell says. “However, I think the data in this new study suggest that, in theory, the EuCorVac-19 formula may be amenable to this type of treatment to make it very thermostable, which would benefit any global deployment.”