Researchers discover primary sensor that detects stomach viruses

Jul 18, 2008

Scientists at Washington University School of Medicine in St. Louis have identified the primary immune sensor that detects the presence of stomach viruses in the body. They show that the sensor – a protein called MDA-5 – triggers an immune response that revs up the body's defenses to fight off the infection. This knowledge may help develop a treatment that prevents or reduces infection, the researchers suggest in their study, published July 18th in the open-access journal PLoS Pathogens.

The stomach flu is technically not the flu at all: the flu virus only affects the respiratory tract. The stomach flu is known scientifically as a norovirus. Norovirus outbreaks are common in locations where people live close together, such as cruise ships, nursing homes, military bases and schools. Antibiotics are ineffective, because they fight bacteria, not viruses. Only recently have scientists been able to grow noroviruses in the laboratory and study them.

"Our research strongly indicates that MDA-5 is the primary sensor for norovirus infection, but the body's ability to detect the virus is so important that it doesn't just rely on one sensor," says senior investigator Marco Colonna, M.D., professor of pathology and immunology. "We found that another protein sensor – TLR3 – serves as a back-up and there may be others that have not yet been discovered."

The team demonstrated their work in mice but says the same proteins are likely responsible for detecting norovirus infection in humans. MDA-5, and to a lesser extent, TLR3, respond by causing other cells to release interferon, which shuts down production of the virus and initiates a full-scale immune attack. MDA-5 and TLR3 are both intracellular proteins. The researchers suspected that these two proteins may be important in detecting noroviruses because they are known to be important in recognizing similar types of viral infections.

Lead author Stephen McCartney, a graduate student in Colonna's lab, first found that cells in the test tube that lack the MDA-5 protein don't mount an appropriate immune response against norovirus infection.

The team then investigated two groups of mice – one group was bred without the ability to produce MDA-5 and the other was bred to lack TLR3. Again, both groups of mice had a defective immune response against noroviruses. In particular, mice without MDA-5 had higher levels of norovirus in their bodies and a defect in the ability to signal other immune cells to respond. Mice that lacked TLR3 also had a decreased response to norvirus infection, the researchers noted.

Interestingly, some people have common variations of the MDA-5 gene that could make them more susceptible to norovirus infection, the researchers say. A norovirus treatment could be especially helpful to people who are more prone to the infection.

Citation: McCartney SA, Thackray LB, Gitlin L, Gilfillan S, Virgin IV HW, et al. (2008) MDA-5 Recognition of a Murine Norovirus. PLoS Pathog 4(7): e1000108. doi:10.1371/journal.ppat.1000108

Source: Public Library of Science

Explore further: US orders farms to report pig virus infections

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

US orders farms to report pig virus infections

6 hours ago

The U.S. government is starting a new program to help monitor and possibly control the spread of a virus that has killed millions of pigs since showing up in the country last year.

Foreigner dies of MERS in Saudi

7 hours ago

A foreigner has died after she contracted MERS in the Saudi capital, the health ministry said on announced Friday, bringing the nationwide death toll to 73.

Vietnam battles fatal measles outbreak

10 hours ago

Vietnam is scrambling to contain a deadly outbreak of measles that has killed more than 100 people, mostly young children, and infected thousands more this year, the government said Friday.

New clues on tissue scarring in scleroderma

11 hours ago

A discovery by Northwestern Medicine scientists could lead to potential new treatments for breaking the cycle of tissue scarring in people with scleroderma.

User comments : 0

More news stories

Treating depression in Parkinson's patients

A group of scientists from the University of Kentucky College of Medicine and the Sanders-Brown Center on Aging has found interesting new information in a study on depression and neuropsychological function in Parkinson's ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...