OCT 16, 2017 08:20 AM PDT

Norovirus Sneaks Around in the Gut to Avoid Detection

WRITTEN BY: Kara Marker

Norovirus is infamous for its invasion of cruise ships, daycares, and other places where a viral infection is particularly devastating. In a new study from the University of Pennsylvania School of Medicine, scientists strip away some of the mystery surrounding this virus, revealing how it manages to avoid the immune system and persist for months at a time.

A new mouse study shows that, even in immunized animals, noroviruses can escape the immune system and still spread by hiding out in an extremely rare type of cell in the gut. Credit: Center for Disease Control and Prevention

Norovirus is extremely contagious, and with so my strains of the virus in the world, you can become infected multiple times. Scientists say it is the “leading cause of nonbacterial gastroenteritis in the world,” a condition people often refer to as the “stomach flu.” Norovirus is responsible for 20,000 deaths and millions of infections each year across the globe.

In the new study, published in the journal Immunity, researchers used a mouse model of norovirus infection, watching how the virus slips through the cracks, avoiding the immune attack even when the mice had been immunized against the virus.

It turns out the norovirus takes cover in a rare gut cell that has virtually no contact with the immune system. Researchers say this may explain why current vaccines don’t work against norovirus, even when researchers see an antibody response after administration.

"Understanding the unique norovirus characteristic of hiding from the host immune system may explain its biology and present opportunities to improve vaccines and therapeutics,” explained senior author E. John Wherry, PhD.

Norovirus persists in some cases but not in others. Why? Some infected people continue to be contagious for weeks and months after initial infection. What happens to the immune system in these cases that prevents the body from eliminating 100 percent of the virus?

Wherry and other researchers thought that, perhaps, T cells become “exhausted” after fighting the virus for several days. However, when researchers tested this hypothesis in mice infected with a chronic norovirus strain versus an acute strain, T cells were just as effective after months of norovirus infection as they were in the days following the acute infection. It wasn’t T cell exhaustion promoting norovirus persistence.

After a closer look at the initial immune response to norovirus, researchers saw T cells elicit a strong reaction and take control of norovirus for about three days. After that, in some cases, T cells could not detect norovirus. The virus was there, but the T cells couldn’t “see” it.

This is where they discovered that norovirus hides in rare gut cells, a type of cell representing an extremely small minority of the billions of other cell types in the gut. These cells do not “talk” to T cells, so norovirus can replicate in peace.

"We found a novel escape mechanism where norovirus becomes essentially invisible to the immune system in the intestine while still producing large amounts of virus that is shed from the intestines," explained first author Vesselin T. Tomov, MD, PhD.

This finding means future vaccines would need to act fast, before norovirus moves to the gut to hide in cells.And now that researchers know where norovirus is hiding, they can develop drugs, potentially T cell-based, to go and find it.

Sources: CDC, University of Pennsylvania School of Medicine

About the Author
  • I am a scientific journalist and enthusiast, especially in the realm of biomedicine. I am passionate about conveying the truth in scientific phenomena and subsequently improving health and public awareness. Sometimes scientific research needs a translator to effectively communicate the scientific jargon present in significant findings. I plan to be that translating communicator, and I hope to decrease the spread of misrepresented scientific phenomena! Check out my science blog: ScienceKara.com.
You May Also Like
MAY 14, 2018
MAY 14, 2018
The Immune System's Antibodies Target Multiple Microbes
For the first time, scientists found that antibodies produced by the immune system can target multiple microbes, as opposed to just one type of microbe. Fr...
JUN 12, 2018
JUN 12, 2018
CD44 Insights & Cancer Influence
CD44 is a known cell surface protein involved in numerous interactions; it is overexpressed in cancerous tissue and its isoforms are being investigated as targets for cancer immunotherapy...
JUL 04, 2018
Drug Discovery
JUL 04, 2018
Discovery of New Properties of an Anti-Tuberculosis Drug
  Investigators at the University of Otago found novel properties of a new anti-tuberculosis drug which may inspire more new drugs to treat tuberculos...
JUL 05, 2018
Health & Medicine
JUL 05, 2018
Is Testing Everyone for Hep C Necessary?
Cases of Hepatitis C, known as Hep C or HCV, are on the rise. In the United States, the CDC reports that there were approximately 3,000 new cases of hepati...
AUG 27, 2018
Cell & Molecular Biology
AUG 27, 2018
Stopping Cell Suicide
Chronic inflammation has been linked to many diseases and can trigger cell death....
SEP 22, 2018
SEP 22, 2018
Could Diet Protect Against Brain Inflammation?
Immune brain cell inflammation due to aging can be mitigated through a high fiber diet...
Loading Comments...