Freedom from the cold chain? British team develops heat-stabilized vaccines

A new method of stabilizing viral vaccine vectors in sugar glass could lead to easier transportation of vaccines, and potentially help veterinarians working in the field.

The so-called “cold chain,” where vaccines must be transferred from one refrigerated environment to the next until they are used, can sometimes be difficult to maintain, especially in remote, tropical or resource-poor areas.

But now, a team of British researchers has developed a method of immobilizing viral vaccine vectors in sugar glass on a membrane. The resulting product can be stored at up to 45 degrees C (113 F) for six months with minimal losses in titer or immunogenicity, according to the study. The research team also devised a way to quickly reconstitute the vaccine with an attachment that fits between the syringe and the needle.

The sugar glass is formed from a mixture of trehalose and sucrose. For their study, the team suspended vaccines in solutions of these sugars and dried them onto a support membrane at room temperature.

“The sugar has two roles,” said lead researcher Matt Cottingham, DPhil, of Oxford University. “It enables solidification (into a glass, not a crystal), stopping chemical degradation; and it can also stick to the proteins on the virus surface, preserving them in their normal shapes.”

Cottingham said the technique is more effective than other methods of trying to preserve vaccines because it is less aggressive than spray drying or freeze drying.

“Our technology achieves drying (and glass formation at the same time) without any aggressive treatments - actually just at room temperature in a dry environment,” he said. “The membrane is what makes this work - it provides a high surface area to volume ratio for drying, and supplies a matrix on which the glass can form as the syrup coats the fibers of the membrane.”

In the study, the scientists tested their thermostabilization method on an adenovirus and a poxvirus, but Cottingham said the method could be used for other types of virus vaccines including veterinary use vaccines.

Richard Bowen, DVM, PhD, is a professor in the Animal Reproduction and Biotechnology Laboratory at Colorado State University. He said researchers have been working on ways to stabilize vaccines for a long time.

“They’re either trying to modify the vaccine itself to make it less susceptible to heat damage, or to come up with better ways to maintain the cold chain,” Bowen said. “It’s a demand , not just in these underdeveloped countries, but even for veterinarians running around in their trucks.”

Bowen said if it works, the technique described in the study could provide great benefits to veterinarians and their patients.

“It might really turn out to be good,” he said. “If you just didn’t have to worry about keeping the vaccines cold, it could potentially be useful for lots of situations.”

Cottingham said it would be at least five years before his team’s vaccine product would hit the market. The group is working with a company to scale-up their production and to ensure that the thermostabilzation process conforms to current good manufacturing practices. However, the five-year time frame referred to the human medicine side of things, Cottingham said.

“A veterinary product would actually be quite attractive, since the legislation on the manufacturing would be much less restrictive, so could potentially be quicker than this,” he said.

The study, “Long-Term Thermostabilization of Live Poxviral and Adenoviral Vaccine Vectors at Supraphysiological Temperatures in Carbohydrate Glass,” was published in the journal Science Translational Medicine.

NEWStat Advancements & research News