Dual vaccine protects against two common food poisoning viruses
If you’ve ever eaten something questionable and then paid for it from both ends for a few days, chances are you’ve had a norovirus. But this common pathogen is surprisingly tricky to treat or prevent. Now, scientists have made progress on a vaccine by piggybacking on a different foodborne virus.
Noroviruses are the leading cause of gastroenteritis or food poisoning, and they’re incredibly contagious. For most people that just means a few days out of commission, but this stomach bug can potentially lead to complications like Crohn’s disease or, for some people, an increased risk of death.
“Pretty much everyone has had norovirus at some point,” said Siyuan Ding, senior author of the study. “You go out to eat, and the next thing you know you’re vomiting and having diarrhea. You will recover, but it’s going to be a rough three days or so. For kids in the developing world who don’t have access to clean water, though, it can be deadly.”
Part of the problem is that we don’t have any good treatments for noroviruses. That’s because human norovirus doesn’t infect common lab animals, so it’s hard to develop drugs through conventional means. But for the new study, researchers at Washington University in St. Louis came up with a creative solution.
Rotaviruses are similar but unrelated microbes that also cause foodborne illnesses – and we’ve had vaccines against them for almost 20 years. So the team used rotavirus as a base to develop a vaccine against norovirus.
The scientists inserted a key norovirus gene into the genome of a harmless rotavirus, so that the latter would form proteins that make up the outer surface of norovirus. This live vaccine was then administered to 11 baby mice with compromised immune systems.
To test how well the vaccine was working, the researchers took samples of blood and feces from each mouse after four, six and eight weeks, followed by a booster at nine weeks and more samples taken at 10 weeks.
Sure enough, the team detected strong antibody responses against both norovirus and rotavirus in the intestines of all mice, and the blood of nine out of 11. Next, the antibodies were taken and administered to mini human intestines grown in lab dishes, and were found to neutralize both viruses there.
Of course, there’s still plenty of work left to do before this could be used in humans, but it’s an intriguing breakthrough. The team says that this technique of using a similar virus as a base could lead to new treatments for other illnesses that are hard to develop drugs for.
“There are a lot of intestinal pathogens out there for which we don’t have good treatments or vaccines,” said Ding. “In principle, we could put a gene from any organism that infects the intestinal tract into the rotavirus vaccine to create a bivalent vaccine. We’d have to find the right targets to produce a good immune response, of course, but the principle is simple.”
The research was published in the journal PNAS.
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And it's not just a semantic issue for non-scientists. I have encountered dozens of people over the years who attributed sudden illness to "food poisoning," by which they meant something they ate that had gone bad, but then they go on to infect others (including me and my family), showing that it was likely norovirus. It's really important than people not confuse the two: one is contagious, the other is not! And for whatever reason, people really want to believe their brief violent illness was "food poisoning" rather than a virus -- I guess because the latter suggests a more dangerous world, and/or they have to worry about infecting others? In any case, I'd say that 90% of the cases of "food poisoning" I encounter in the wild are clearly norovirus, and people really need to learn the difference and assume the precautionary principle when they feel better a couple days later but may well still be contagious.