Vaccines and other biologic drugs quickly degenerate and lose their effectiveness if left out of the fridge for very long, creating a huge problem for healthcare delivery in less developed parts of the world. Fortunately, a new preservation technique could offer longer shelf lives. Reporting today in the Proceedings of the National Academy of Sciences (PNAS), researchers have discovered a silk protein capable of stabilizing heat-sensitive biologics for months at a time at room temperatures or even hotter.
“This work shows the high stability of silk and increases the chances of our ability to stabilize other drugs and bioactive molecules that are sensitive to heat,” says SU Kundu, who studies silk biomaterials at the Indian Institute of Technology in Kharapur and was not involved in the study.
A team led by David Kaplan, a chemical bioengineer at Tufts University in Medford, Massachusetts, purified the silk protein from silkworm cocoons and added the freeze-dried product to a commercial measles, mumps and rubella vaccine. They then exposed the silk-stabilized vaccine to the scorching temperatures common to many parts of the developing world — not to mention the US Northeast this past week — and showed the product retained the majority of its potency up to six months later. “This is the first study to successfully show how silk can be used in a commercially available vaccine,” he says.
According to Randy Lewis, a spider silk researcher at Utah State University in Logan, Utah, the secret to silk’s action as a vaccine preservative lies in its ability to encapsulate the attenuated viruses in the preparation and protect them from heat and moisture. “The silk is physically trapping the virus and preventing it from changing its structure,” he says.
Kaplan says the data are strong enough to merit testing of the silk-stabilized vaccine in the near future. “I would hope to see a clinical trial start within one year,” he says.
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