See the detailed stories on these vaccines:
Mucosal Tissues Offer Tempting Targets,
Success of Edible Vaccine May Depend on Picking Right Fruit, and
Transcutaneous Methods Get Under the Skin
All trigger disease resistance in systems other than the blood. And examples of all approaches use cholera toxin to fortify that resistance. Genetically engineered fruits and vegetables use it to gird the gut against pathogens. Some nasal methods employ it to marshal sinus lining strength against infectious diseases. And some transdermal strategies apply it to steel the skin's immune responses against childhood ailments.
Some needle-free vaccines utilize multiple approaches. For example, Aviron Inc.'s nasal flu spray triggers a strong response in the mucosal linings of the respiratory system, but it also causes a weak blood serum response and a limited cytotoxic T cell response against invaders.
|Stanley Leary/Georgia Technology Research Corporation|
UNDER THE SKIN: One tiny patch contains 400 needles in an array designed by scientists at the Georgia Institute of Technology to deliver drugs. The needles poke beneath upper layers of skin, but above nerve endings.
William Langridge, professor of biochemistry, microbiology, and molecular genetics at Loma Linda University, and colleagues applied the mucosal approach to a cholera vaccine packaged in a transgenic potato. He notes that attenuated cholera can produce antibodies against cholera, carry other antigens to a target, and boost responses to other antigens.
Gregory M. Glenn, scientific director of IOMAI Inc., a biotech company in Washington, D.C., thinks that the delivery field will continue to sprout a number of needle-free approaches. Different diseases, each with specific antibody requirements--will likely call for diverse vaccines. "Some [vaccines] are going to require local mucosal immunity. Some won't," Glenn notes. He acknowledges that the transcutaneous vaccination approach IOMAI is developing competes against other needle-free methods--especially since it, like many of the other methods, relies on the cholera toxin for its efficacy. "But I'm glad to see these technologies rise up."
Nonscientific factors--consumer satisfaction, cost, and ease of use--will influence which approaches succeed. Still, the growing number of methods will each likely find specific applications, Glenn predicts. "From a commercial standpoint, I think there's a place in the sun for everyone."