Department of Biochemistry
February 26, 1998
Efficacy of a Food Plant-Based Oral Cholera Toxin B Subunit Vaccine
Scientists in the Center for Molecular Biology and Gene Therapy at Loma Linda University in Southern California have managed to turn potatoes into factories for cholera proteins that effectively stimulate the immune system in mice to protect the mice from cholera toxin. This work will appear on the 27th of February in the March issue of the journal Nature Biotechnology and will bring scientists closer to commercially available edible vaccines that can make vaccination painless, cheap, and simple to administer.
William Langridge, PhD, discusses the development during
the February 27 press conference.
William Langridge, PhD, professor of biochemistry and microbiology and molecular genetics, Center for Molecular Biology & Gene Therapy, and his associates took a 372 base-pair segment of the cholera B toxin gene encoding a nonpathogenic toxin subunit called CTB and placed it into plasmids (DNA rings) that were transferred into potatoes. The potato tubers, now making CTB, were fed to mice, whose mucosal immune system produced cholera-specific antibodies. When the "immunized" rodents were challenged with the whole cholera toxin, those on the potato diet had a 60 percent reduction in diarrhea as compared to those unaided by the vaccine. Additional feeding of the potato acted as a "booster" for the mice, rapidly increasing blood and intestinal levels of the antibody.
In addition, the scientists were able to generate surprisingly high levels of vaccine protein (0.3 percent of the total soluble protein) by getting the potatoes to amplify the amount of protein they produced. Up to now, the problem has been that plants don't make much of the proteins wanted, on the average of about .01 percent of total plant protein. Dr. Langridge is currently working on ways to further increase protein amounts. Cooking the potatoes leaves 50 percent of the protein intact. One advantage of using the digestive system as a immune pathway is that it induces a strong response to pathogen proteins from the body's lymphocytes. Further, lymphocytes sensitized in the gut-associated lymphoid tissues migrate throughout the body leading to protection at other mucosal surfaces.
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Press Conference in Randall Visitors Center
Corner of
Anderson and University Streets, Loma Linda, California
Friday, February 27,
at 11:00 a.m.
Contact:
Dick Weismeyer, director, University relations (909)
558-4526
Kimberley Kuzma, director, community relations (909) 558-4419