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Norovirus: You may have misunderstood how a common intestinal virus spreads

Although norovirus lives in the intestine, studies in mice suggest that it may also survive in the salivary glands, and this finding suggests that there are additional steps that can be taken to limit infection. Suggests


June 29, 2022

3D graphic representation of norovirus particles – can grow in salivary glands and intestines

Tatiana Shepeleva / Shutterstock

Three intestinal viruses, including norovirus, can spread through the saliva of mice. This discovery, coupled with the discovery that norovirus can multiply in human salivary gland cells, facilitates new recommendations for minimizing infection and may ultimately lead to new antiviral treatments. ..

NorovirusRotavirus and astrovirus are known to infect the intestines, causing vomiting, diarrhea and abdominal discomfort in more than 1.5 billion people worldwide each year.We already knew these virus It can spread through the fecal-oral route. For example, without proper hand washing, small particles of fecal material from an infected person can invade the food of an uninfected person.

“These viruses were called intestinal viruses because they were thought to replicate in the intestine, flow into the stool, and then spread the stool to another individual via the oral route,” he said. Nihal Altan-Bonnet At the National Institutes of Health in Maryland.

As a result, hand washing and surface washing are considered the best way to prevent the spread of the intestinal virus.

“Now, when I examine the salivary glands, I see a lot of viral replication at the same level as the intestine. This was a real surprise to us. [because] People thought these viruses wouldn’t spread through saliva, “says Altan-Bonnet. “This suggests that measures such as wearing a mask to contain the outbreak of the intestinal virus should be taken, similar to the way we treated covid-19.”

In a series of experiments, Altan-Bonnet and her colleagues orally infected mouse puppies with mouse versions of the three intestinal viruses. This revealed that the salivary glands of rodents can function as a reservoir for virus growth.

The team also discovered that infected lactating puppies can infect the mammary glands of mother mice within 24 hours of breastfeeding. The resulting infection is confined to the mammary glands – the mother does not show symptoms of the disease, says Altan-Bonnet. However, uninfected puppies can catch the virus from the infected mammary glands while breastfeeding.

In addition, researchers detected a surge in antibodies in the mammary glands of adult mice 72 hours after infection with puppies. This is consistent with a decrease in the amount of virus in the intestines of infected puppies, suggesting that mammary gland infections may generate antibodies in the milk and help eliminate infections in lactating puppies. increase.

“Approximately three days after breastfeeding the puppy, the puppy’s infection begins to subside. This correlates with a surge in antibodies. This very rapid immune response by the mother is [pup] Helps to infect and clear the mother’s breasts [pup’s] It’s an infectious disease, “says Altan-Bonnet.

“The fact that mothers rapidly create protection [antibodies] For their puppies when their mammary glands are infected [may be] A wonderful evolutionary reaction to protect their youth. ” Sarah Caddy At Cornell University in New York, who was not involved in the study.

Later, researchers expanded their research and found that human strains of norovirus could grow easily and inexpensively in human salivary gland cells. This discovery is important because, until now, the virus has not been able to easily propagate in the laboratory. As a result, it is difficult to develop treatments, which is partly the reason why vaccines or antiviral therapies against norovirus do not currently exist.

“Having a better way to culture norovirus is a kind of holy grail,” says Altan-Bonnet. “Also, human saliva cell lines, which can grow relatively easily and cheaply, are excellent models for growing these viruses, and we have created a model system for testing antiviral agents and producing viruses to produce vaccines. We also showed that we can provide it.

“This work is really interesting and important,” says Caddy. “We have known for 20 years that norovirus carbohydrate receptors are present in saliva, but no one has ever convinced us that this is important for viral infections.”

Next, researchers want to investigate whether the virus can spread through human saliva.

“After all, mice are not humans. We can assume that the same salivation is caused by a human-specific intestinal virus, but no definitive evidence has yet been shown,” says Caddy.

Journal reference: Nature, DOI: 10.1038 / s41586-022-04895-8

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Norovirus: You may have misunderstood how a common intestinal virus spreads

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