Rows of bright-green, leafy tobacco plants grow in a humid greenhouse. They look identical, but one row is special. These are genetically altered tobacco plants, carrying the shell of the human papilloma virus, which causes cervical cancer in women.
Tobacco leaves dried, rolled and smoked cause lung cancer. But these genetically-modified leaves are little factories, producing a potentially inexpensive vaccine against cervical cancer, the leading cause of death from cancer among women in Southern Africa — and one that is particularly difficult to catch early as it is buried deep within the female reproductive system.
The tobacco plant is an ideal crop for genetic modification. For a start, the genetic alteration doesn’t confer any survival advantage over plants that have not been tweaked. In addition, tobacco and humans have been around together for so long that they have developed a reliance on each other: the plant can’t escape and grow wild. Just like maize, tobacco requires human intervention to survive in Africa.
“Tobacco is a really well-understood crop,” says Professor Ed Rybicki of the University of Cape Town. “All of the kinds of conditions that one needs
to grow it are very well understood indeed. It is relatively tolerant of
all sorts of conditions and you get an enormous volume of leaf out of each plant — one hectare of mature tobacco gives you 20 000kg or 20 tons of wet leaf. So that is an enormous volume of plant material that you can actually make something out of.”
What Rybicki and his team are trying to make out of tobacco is an affordable vaccine against the virus, which causes cancer in the cervix, the gateway between the vagina and the uterus. Men can transmit the virus. They can also develop cancer of the penis. However, the rate of penile cancer is far lower than that of cervical cancer, so it’s not quite the same public health issue.
South Africa used to have the capacity to generate its own polio-virus vaccine in the 1950s. Now it imports vaccines. From his office in the department of molecular and cell biology, Rybicki notes that simply working on a vaccine carries significant advantages for developing countries: “There are a lot of orphan diseases out there that nobody wants to make a vaccine for.
Vaccines cost about $100-million to take through from beginning to human testing, and this is enormous money for big pharmaceutical companies. Drug development can cost even more than vaccine development, but because the vaccine market is so much smaller than the drug market, the return is relatively low.”
The number of vaccines being made today has dropped to its lowest in a quarter of a century. Some vaccines have become a victim of their own success: a one-off dose of polio drops generates considerably less money than, say, anti-depressant pills like Prozac, which have to be taken every day for the rest of the patient’s life.
But there are major international efforts under way in countries such as India, Brazil, China and Argentina to make publicly-funded vaccines. “Diseases that don’t occur in Europe or the United States do not get vaccines made for them. Or they don’t get the right type of vaccine. In Africa, we won’t necessarily get the correct HIV sub-type vaccine made, for example.”
New vaccines made in Europe or the US are expensive.
“The Hepatitis B vaccine, when it first came out, was about $40 a dose and it is now about a dollar a dose, but it took 10 or 15 years to get to that point,” marvels Rybicki. The current push by big pharmaceutical companies for a vaccine for cervical cancer — already well advanced, with the first human trials accomplished — doesn’t worry him.
The vaccine will be too expensive for Third World health budgets, he predicts. His aim is to find something that attacks the virus, not the wallet.