Tardigrade proteins may aid stability, duration of treatments

So-called water bears could help extend shelf life of replacement therapies

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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Proteins from tardigrades — microscopic animals known for their ability to survive in extreme conditions — could be used to stabilize replacement therapies for hemophilia A, allowing treatments to be stored for longer periods of time without refrigeration, a proof-of-concept study shows.

“Our work provides a proof of principle that we can stabilize Factor VIII, and likely many other pharmaceuticals, in a stable, dry state at room or even elevated temperatures using proteins from tardigrades — and, thus, provide critical live-saving medicine to everyone everywhere,” Thomas Boothby, PhD, said in a university press release. Boothby is an assistant professor at the University of Wyoming and co-author of the study.

The study, “Natural and engineered mediators of desiccation tolerance stabilize Human Blood Clotting Factor VIII in a dry state,” was published in the journal Scientific Reports.

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Hemophilia A is caused by mutations that disrupt the function of factor VIII (FVIII), an important clotting protein. Replacement therapies, which involve administering a functional version of this protein to restore blood clotting and prevent excessive bleeding, are considered a standard treatment for hemophilia A.

FVIII products are a type of biologic therapy — medications that contain or are made of components found in living organisms. Like other biologic therapies, FVIII products generally are not very stable at room temperature, so they usually have to be kept cold for long-term storage and transportation. That process is sometimes called cold-chain, and it poses a major barrier to the use of these therapies in many parts of the world.

“Under ideal circumstances, cold stabilization can be effective, however, in remote or developing parts of the world, purchasing and maintaining the necessary infrastructure such as freezers, electrical systems, and backup generators needed for the cold-chain to work seamlessly can be close to impossible,” the researchers wrote.

What are ‘water bears?’

Tardigrades, also known as water bears, are microscopic animals that are infamous for their ability to survive in extreme conditions. They have been documented to live after being subjected to high heat (more than 300 F) or cold temperatures of near absolute zero (about -458 F). They also can survive being almost completely dried out, and can even endure the vacuum of space.

One of the keys to tardigrades’ resilience is that, under stressful conditions, they can undergo a process called vitrification.

All molecules, from proteins in cells to the active ingredients in biologic therapies like FVIII products, are in constant motion. At elevated temperatures, molecules move faster and are more prone to falling apart, which is why cold storage can help keep many hemophilia treatments stable for longer periods of time.

Vitrification is a process that works to turn the inside of a tardigrades’ cells into a thicker, gel-like consistency that can hold molecules in place so they don’t fall apart. Notably, this process does not form ice crystals, which can damage cellular proteins and biologic therapies.

“Vitrification observed in nature accomplishes the two main tasks of the cold-chain, (1) reducing molecular motion and (2) minimizing crystallization, but without the need for cold-temperatures,” the researchers wrote.

Tardigrades achieve vitrification by producing certain specialized proteins and sugar molecules.

Researchers tested several vitrification-associated molecules to see whether they could improve the stability of FVIII under two types of stress that are common problems encountered in the long-term storage of medications: high temperatures, and changes in water content, which in storage conditions can occur due to variations in humidity.

Results showed that several of the tested molecules, particularly a tardigrade protein called CAHS D, could effectively preserve FVIII’s clotting activity under these stressful conditions.

Breaking dependence on refrigeration

“This study shows that dry preservation methods can be effective in protecting biologics, offering a convenient, logistically simple and economically viable means of stabilizing life-saving medicines,” Boothby said.

“This will be beneficial not only for global health initiatives in remote or developing parts of the world, but also for fostering a safe and productive space economy, which will be reliant on new technologies that break our dependence on refrigeration for the storage of medicine, food and other biomolecules,” Boothby added.

The team further showed that altering the structure of CAHS D so that it was better or worse at forming gel-like structures could alter its protective properties. Specifically, they found that a more gel-prone form of the protein was better for protecting FVIII products from high temperatures, whereas a less gel-prone form was better under conditions of varying water levels.

This suggests that CAHS D and other vitrification-associated proteins “can be tuned to serve specific functions with regard to biologic stabilization,” the researchers wrote.