No Smoke: Tobacco Used in Vaccine
For many people, tobacco represents a death sentence -- inflicting nicotine addiction, lung cancer and other ills. But for millions of women in the developing world at risk for cervical cancer, tobacco could eventually be a lifesaver.
University researchers are working on genetically engineering tobacco plants to produce an experimental vaccine against the human papillomavirus, or HPV, which can lead to cervical cancer.
Georgetown University pathologist C. Richard Schlegel has developed an experimental vaccine, now in human trials in Costa Rica, against HPV. A sexually transmitted disease that causes genital warts, HPV is the origin of virtually all cases of cervical cancer -- though a relatively small number of HPV sufferers develop cancer.
If HPV infection could be prevented, however, it would slash the incidence of cervical cancer, Schlegel said. But the high cost of production for the HPV vaccine in development could make it unavailable to many women in poor countries.
"The extraction and the purification of the protein is fairly complicated," Schlegel said, referring to the active compound in HPV vaccine. "The protein itself is fairly unstable; they have to keep it frozen (in liquid nitrogen)."
Schlegel believes the vaccine might be approved for clinical use in five to seven years, but it's projected to cost about $100 per dose. Three doses of the vaccine are required to confer HPV immunity.
That $300 cost would make it too expensive for use in poor nations, where cervical cancer kills an estimated 250,000 women a year.
Enter the tobacco plant. Researchers at North Carolina State University are developing a transgenic tobacco plant they hope will produce the protein needed for the HPV vaccine. If it works, the cost per dose of the vaccine could drop to just pennies.
Tobacco is particularly well suited to the task of producing vaccines and other specialized compounds, said Arthur K. Weissinger, the N.C. State researcher leading the effort to engineer tobacco plants for the HPV vaccine.
It's relatively easy and cheap to genetically alter tobacco, Weissinger said. The plant also produces large amounts of biomass -- about 180,000 pounds per acre per year. This raw leaf and other material would be crushed and processed so the protein could be extracted.
Weissinger estimates it will take five years to develop the transgenic tobacco and the extraction methods necessary to produce the HPV vaccine in substantial quantities.
Weissinger sees the vaccine, and other potential applications of genetically engineered tobacco, as a savior not only for women at risk for HPV, but also for tens of thousands of tobacco farmers in rural southern U.S. communities that have long depended on the plant as an economic mainstay.
"What we're trying to do now is take that crop and reinvent it," he said. "We can produce some proteins in abundance for the cost of growing the crop."
Weissinger added that the transgenic tobacco would be grown in controlled conditions -- isolated from other strains of the plant and not allowed to flower -- so the altered genes wouldn't escape the field.