By Samantha Chan Edinburgh

Australian researchers have engineered lettuce to express the measles virus H protein, bringing an edible measles vaccine one step closer to reality. The lettuce, which when freeze dried can be stored at room temperature for months at a time, contains viral protein that is heat stable up to 70°C.

Although a successful measles vaccine exists, like most injectable vaccines, it requires constant refrigeration and administration by trained personnel. This limits its usefulness in some of the countries worst affected by the disease.

"The strong point we are trying to make is that vaccines are needed that can be administered orally, without need for injection, are not too costly, and are heat stable," said Steve Wesselingh, director of the Macfarlane Burnet Institute for Medical Research and Public Health in Melbourne.

Lettuce: the healthy option

Wesselingh, who presented his latest findings at a joint meeting of the Australian and New Zealand Societies for Microbiology in Auckland, New Zealand, says the next step is to transfer the technology to primates, and then humans. "We have to keep highlighting the benefits of what we are doing, and reducing the risks, [for example] of contamination of wild crops by the transgenic plants," he said.

Obstacles to the production of a working vaccine range from stomach acid and intestinal enzymes digesting much of the antigen to negative public attitudes toward genetically modified food crops.

Nevertheless, Wesselingh remains optimistic: "Edible vaccines for any disease will answer a lot of the questions dogging vaccine researchers; how to deliver oral, heat stable vaccines, and allow new methods of vaccine delivery."

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