HURDLES AHEAD
All the company had to go on was part of the virus’s genetic sequence. But while in egg-based production whole flu viruses are injected into the eggs, where they replicate and form the basis for the vaccine, all that’s really needed to trigger immunity are the proteins that stud the virus’s coat.
Those proteins, called hemagglutinins, are what the immune system attacks. They can be produced by splicing the hemagglutinin gene into almost any kind of cell; Medicago uses harmless bacteria to carry the hemagglutinin genes into the tobacco plant leaves.
Technicians at the greenhouses in North Carolina then soak 36-day-old Nicotiana benthamiana plants (cousins of those used for cigarettes) upside down in a liquid containing the Trojan Horse bacteria, explained chief scientist Marc-Andre D’Aoust. Through a process called vacuum infiltration, air is drawn out of the leaves and they suck up the bacteria.
After growing in special chambers for a week, the leaf cells are churning out hemagglutinins. Extracted, purified, and combined with other bits of the virus, they form the basis for a vaccine.
To succeed, the companies will have to persuade the U.S. Food and Drug Administration not only that the vaccine is safe and effective, as clinical trials are designed to show, but also that the hemagglutinin or other proteins can be extracted from the leaves cleanly and that the largely-untested manufacturing process yields a uniform, reliable product.
Major vaccine makers are cautious about the new technology. “We tend to avoid publicly speculating on what future technologies we might embrace,” said Robert Perry, a Glaxo spokesman said.
“Today, all of our flu-vaccine production is in (chicken) eggs,” said Rene Labutat, vice-president of manufacturing for Sanofi. “But we are looking at the recombinant approach, including in mammalian cells, algae, fungi and plants.” Reuters) [eap_ad_3]