Researchers said today they had taken a step closer to making an edible vaccine against hepatitis B, a virus that infects billions of people and that can lead to liver disease, cancer and even death.
They said they had genetically engineered a potato that produces the vaccine in its flesh.
“The hepatitis B vaccine currently in use is ... based on an antigen produced in yeast. We have shown we can produce the same antigen in plants,” said Hugh Mason, who led the research at Cornell University’s Boyce Thompson Institute for Plant Research, said in a telephone interview.
Antigens are proteins on a virus or bacteria that stimulate the body to produce antibodies, which in turn flag an invader for destruction by immune cells.
For years scientists have known that a protein known as HBsAg can produce this response, and they can take the gene for this viral protein, insert it into yeast, which then grow and produce a protein that can be used to make vaccine.
But it is not cheap and it has to be refrigerated, making distribution in remote areas difficult. “Most developing countries just can’t afford it,” Mason said.
Tremendous Need for Vaccine
With an estimated two billion people infected with hepatitis B, the need for a vaccine is tremendous.
“What we want to try to do is produce this material in plants and show there potential for delivery by just eating the plant material. Our study with mice suggested this could be a feasible strategy.”
Mason’s team genetically engineered potatoes to produce the protein and then fed the raw potatoes to mice. The mice produced antibodies against hepatitis B, the researchers wrote in the journal Nature Biotechnology.
Mason said further, as-yet unpublished studies in mice show they can increase the power of the vaccine, and it might be used as a booster for the injected vaccine. “Obviously there is going to be a difference between humans and mice,” Mason said.
A More Robust Response
“We do think it’s likely that we will need a more robust response.”
The Cornell researchers have also done a small study in human volunteers, but the British-based company they were working with, Axis Genetics Plc, went out of business a year ago amid European fears about genetic work. He also thinks that fresh vegetables will not be used, but perhaps a processed version — maybe even a candy bar that would be stable and easy to distribute.
One big hurdle will be getting a commercial partner, Dr. Julian Ma of Guy’s Hospital in London said in a published commentary.
“Apart from a handful of small biotechnology companies, industry has been slow to invest in this field for a variety of reasons,” Ma wrote in Nature Biotechnology.
“For certain, the commercialization of plant vaccines will require an unusual and imaginative collaboration between the agricultural and pharmaceutical industries. Another concern is the potential for commercial profit.”
Ma noted that the current, injected hepatitis B vaccine had generated profits of $1 billion a year. “It is extremely unlikely that a plant-derived alternative could come even close to matching this commercial success,” Ma wrote.
The only current oral vaccine is for polio.