A number of studies this week at the 104th General Meeting of the American Society for Microbiology suggest that the search for a vaccine which could prevent foodborne diseases may be nearing its end.
"Vaccines have been proven to be an effective means of prevention for many infectious diseases, but there are no effective vaccines for most common foodborne diseases," said John Gunn of the Ohio State University, who presented research on a new vaccine against multiple bacteria.
"The development of a single vaccine that provides protection against the most common foodborne pathogens would greatly enhance human health," he added.
Gunn and his colleagues have developed a strategy using a live, crippled strain of Salmonella bacteria that do not cause disease to which are added 'pieces' of other bacterial pathogens to stimulate immunity to multiple pathogens.
"We have already developed a highly attenuated Salmonella typhimurium strain which functions as an effective live, oral vaccine against S. typhimurium," he said.
The researchers modified the vaccine strain so that it also contained a gene from another foodborne pathogen, Listeria monocytogenes. When they administered the modified oral vaccine to mice, it protected them 100 per cent against lethal doses of both foodborne bacteria.
Another group of researchers at the meeting announced they were one step closer toward the development of an edible vaccine against the most virulent forms of the Escherichia coli bacteria, known as shiga toxin-producing E. coli, which include the destructive E. coli O157:H7.
These bacteria, because of the shiga toxin they produce, can cause mild to bloody diarrhoea and in some cases are responsible for a complication known as hemolytic uremic syndrome, which is characterised by kidney failure, brain damage and sometimes death.
Sharon Wen and her colleagues at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, successfully transferred a modified version of one of the shiga toxin genes into tobacco plants. This plant-derived vaccine was effective in producing antibodies against the toxin when administered to mice.
"Next the immunised mice will be challenged with the toxin or toxin-producing bacteria to determine if the plant vaccine is protective," said Wen. "Once the protective efficacy of these plant-based vaccines is established, the bacterial genes can then be moved into other plants such as bananas or corn for delivery to humans or animals."