LOS ANGELES, May 29 (Reuters Health) - Potatoes engineered with Norwalk
virus, which along with related viruses causes most cases of diarrhea in the US,
can induce an immune response in humans, according to the results of a study.
The work builds on earlier work by Dr. Charles Arntzen of the Boyce Thompson
Institute for Plant Research in Ithaca, New York, and colleagues. His group had
shown in 1998 that bioengineered potatoes could induce antibodies against a
toxin produced by E. coli bacteria, another common cause of diarrhea.
In an interview with Reuters Health at the recent annual meeting of the
American Society for Microbiology, Arntzen said that Norwalk virus will probably
require an oral vaccine to induce protective immunity in the gut. As he reported
at the meeting, 19 of 20 volunteers who ate the genetically engineered potatoes
developed serum and mucosal antibodies against Norwalk virus.
However, he said it is unclear whether this is enough of an immune response
to fight off an infection. "We have no way of determining how strong--what is a
correlate of protection--because the correlate of protection has never been
established for Norwalk virus," he said. "We don't know if we elicited enough
antibody or not. We'll only get that as we begin testing people."
His group is planning another trial in the US, which he said could lead to a
trial where the volunteers would be challenged with the virus. Arntzen said they
are also interested in testing this vaccine in developing countries,
particularly Mexico, since the virus strains and the intestinal microflora will
be different from the US.
Although the vaccine is still in the early stages of development, he is
optimistic about its prospects. "We do anticipate that Norwalk virus is very
probably going to be our first vaccine that hits the licensure stage and could
go into commercial development," he said.
