Transgenic Potato Confers Immunity: Vegetables Or Fruit Could Replace Vaccine And Needles

In the May issue of the journal Nature Medicine, Carol Tacket, MD, professor at the University of Maryland School of Medicine, and colleagues report successful results of their first human clinical trial of the transgenic vegetables developed at the Boyce Thompson Institute for Plant Research, affiliated with Cornell University in Ithaca, NY. Fed to healthy human volunteers at the University of Maryland Center for Vaccine Development, potatoes genetically engineered to contain a gene from the E.coli bacteria produced antibodies in the blood and in the mucosal lining of the intestines. Volunteers who ate garden-variety potatoes in the randomized, double-blind trial showed no immune response.

"It is truly remarkable to think that you could eat a potato that has an extra protein and produce antibodies against a bacterial pathogen," Tacket remarks, "but that is exactly what happened." She calls transgenic plants "a new strategy for development of safe and inexpensive vaccines against diseases such as tetanus, diphtheria and hepatitis B. Oral vaccines in edible plants offer hope of a more practical means of implementing universal vaccination programs for the developing world."

The volunteers consumed three doses of 100 or 50 grams of raw, peeled, cubed potato over 21 days. Blood and stool samples were collected before the first dose, after one, two, three and four weeks, and after 59 days.

Volunteers kept journals, recording any symptoms for three days after each dose. The potatoes were generally well tolerated, the researchers report. The study was conducted as a proof of principle. Tacket’s collaborators had already tested the transgenic potatoes and generated a strong immune response in mice. "We knew that we had an immunogenic protein in a plant that is eaten by human beings," she explains. "We wanted to determine if human beings would develop a serum and/or mucosal response to an antigen delivered in an uncooked food."

Tacket says the next step will be to try an antigen that does not generate an immune response as readily, possibly one from hepatitis. Studies also are needed to determine how long immunity lasts and to develop other transgenic plants that could carry safe and inexpensive vaccines to the populations of countries where they are grown and are part of the normal diet.

The research was supported by the National Institute of Allergy and Infectious Diseases’ Division of Microbiology and Infectious Diseases, National Institutes of Health.