Vaccination for tuberculosis may become as easy as inhaling. A team of researchers from the University of North Carolina at Chapel Hill and Harvard University have developed the tuberculosis vaccine bacillus Calmette–Guérin into an easy-to-administer, highly portable aerosol.
“Rising rates of tuberculosis and drug-resistant disease in developing countries have amply illustrated the need for more effective vaccines,” says David Edwards, a biomedical engineering professor at Harvard University and a researcher involved with the inhalable vaccine’s design. “While most new TB vaccines continue to call for needle injection, our vaccine could provide safer, more consistent protection by eliminating these injections and the need for refrigerated storage. We see great promise for this new treatment.”
Appropriately, the team used guinea pigs, known to be susceptible to TB, were used to test the vaccine. Some of the guinea pigs were vaccinated with BCG while others were given the aerosol version. All of the guinea pigs were exposed to TB in an aerosol exchange chamber. Four weeks after exposure, the researchers analyzed the animal’s lungs and spleens. They found symptoms of TB in five per cent of the lungs and 10 per cent of the spleens of BCG-vaccinated guinea pigs. However, in the guinea pigs that received the aerosol, they found symptoms in just one per cent of spleen and lung tissue.
“Tuberculosis is one of the most resistant and challenging diseases to protect against, and the successful results of aerosol delivery using nanoparticle technology potentially offers a new platform for immunization,” says Barry R. Bloom, study contributor and dean of the Harvard School of Public Health. “Were the animal results confirmed in human studies, this technology could be used not only for TB vaccines, but those protecting against other infectious diseases as well.”
Currently, the BCG vaccine is freeze-dried, which requires refrigeration until it is used. The freezedried vaccine must be mixed with medical-grade water before it can be injected. This method makes immunization complicated in certain geographic areas, especially developing countries with limited or no access to electricity and medical supplies. Administering the aerosol vaccine to humans would be much easier than the present method. Using a drinking straw-shaped inhaler, adults would simply hold the tube to their mouth and breathe in. For infants, a pacifier-shaped inhaler is in development. According to study contributor Anthony Hickey, “You can have the baby essentially blow the powder into the back of the throat.”
The powder used in the inhaled vaccine is spray dried. Spray drying allows the researchers to take advantage of the dried vaccine bacteria’s tendency to form as elongated particles, highly effective when inhaled. This method avoids certain requirements associated with freeze drying, such as refrigeration and the need for water.
“Spray-drying is lower-cost than BCG, easily scalable for manufacturing, and ideal for needle-free use, such as via inhalation,” says Edwards. “Its greater stability at room temperature could ultimately provide a better means of creating and delivering vaccine throughout the world.”
Currently, bacillus Calmette– Guérin is used worldwide to immunize infants and adults against TB. It is estimated that over one billion people have received the vaccine since it was first used in 1921. BCG is most effective in preventing TB in children, and is the world’s most widely used childhood vaccine, as each year approximately 100 million babies are injected.
