Researchers at KU Leuven have developed a new research model to grow and study the human variant of the norovirus. The virus could thus far only be studied through a variant that occurs in mice. The new model, that is described in the journal PLOS Pathogens, should allow researchers to develop a treatment for stomach flu.
"Massive outbreak of stomach flu on cruise ship", "Primary school hit by stomach flu", or even "Peter Sagan loses four kilos due to severe stomach flu". The news articles about stomach flu are aplenty, and the culprit is often the norovirus. This is a very contagious virus that is often transmitted from person to person, for instance through hand contact or contaminated food. Places with many people, such as schools, assisted-living centres or day-care centres, are therefore more prone to possible outbreaks.
"Even though they are both infectious diseases, flu and stomach flu have little in common", clarifies virologist Johan Neyts. "The former is primarily an infection of the airways, whereas the latter affects the intestines. The thing viruses such as influenza and the norovirus do have in common is that they mutate quickly. We see new variants every time and that makes it hard to protect yourself from it."
The team of Professor Neyts and Doctor Joana Rocha Pereira, in collaboration with the lab of Professor Peter de Witte (Molecular Biodiscovery), have now made significant progress in this research field. "For the first time, we’ve been able to develop an efficient model to study the human norovirus", says Professor Neyts. "It was extremely difficult to grow the virus in the lab until now. We were able to do this with the animal variant, the one that occurs in mice for instance, but that virus is still pretty different from the human variant."
"Our solution is zebrafish larvae, which are used frequently in other types of biomedical research as well", says Professor de Witte. "First, we isolate the norovirus from the stool of infected patients. Next, a minimal amount of the virus is injected into the larvae."
The research model has various benefits, says Professor Neyts. "We can inject hundreds of these minuscule larvae in one day, for instance. Moreover, the virus only needs a few days to start multiplying. The larvae are also nearly transparent, which allows us to closely monitor the infection using microscopes and other techniques."
Prevent an outbreak
The new method is key to studying the biology of the norovirus, but also plays an important role in the development of possible medicines. The first tests show that certain molecules slow down the multiplication of the virus in the larvae.
This could eventually lead to a treatment, and prevent an outbreak of the stomach flu, says Doctor Rocha Pereira. "It’s an important step, especially in places where you have a high number of debilitated people, such as hospitals or assisted-living centres. The purpose of an antiviral treatment is to limit an outbreak as efficiently as possible. The idea is that, once one or several patients contract stomach flu, we can protect the other residents by administering the medication before they fall ill. The development of a treatment will require a lot more research, but we’ve already taken an important step with this new model."
The study "A robust human norovirus replication model in zebrafish larvae" was published in the journal PLOS Pathogens.