Ebola, influenza and cold viruses have given a bad name. But there may be a bright side to these small packages of genetic material. Researchers studying mice have shown that the virus can help to maintain and restore a healthy gut in much the same way that friendly bacteria are.
The work "shows for the first time a virus can functionally substitute for bacteria and provide beneficial effects," says Julie Pfeiffer, a virologist at the University of Texas Southwestern Medical Center in Dallas, who was not involved in the study. "It is shocking."
our bodies are mostly microbes, with each to welcome us trillions of bacteria that our so-called microbiome. These bacteria appear to play a role in all of our weight to our allergies. But the virus also hiding in and around these bacteria and they far exceed the microbes.
as the microbiome, this "virome" may be important to human health. a recent study, for example, found that viruses that are abundant in saliva can eliminate harmful bacteria. Kenneth Cadwell, a virologist at New York University School of Medicine in New York, wanted to know what virus in the intestine could be done. In particular, he was interested in a group called norovirus. Although they are known to cause diarrhea outbreaks on cruise ships and diseases in laboratory mouse colonies, norovirus infect mice without adverse effects.
Indeed, he and his postdoc Elizabeth Kernbauer have now found that certain norovirus have a good side. In the laboratory, the researchers were breeding mice in sterile environments, such as rodents and young people lack the typical portfolio of microbes and viruses than other mice. Germ-free mice are abnormal. They are not quite certain T cells, which are important for immune function, and they are too many other immune cells involved in allergic reactions. They also abnormally thin villi, fingerlike microscopic projections on the intestinal wall that help absorb nutrients. Other researchers have shown that bacteria to mice without giving germs can rebalance the numbers of immune cells and fertilize the villi. Adding a mouse norovirus germ-free has the same beneficial effect, compared Kernbauer, Cadwell and Ding Yi, a pathologist at New York-Presbyterian Hospital in New York online today in Nature . Two other types of norovirus similar help make the healthy gut again, they found.
In a follow-up experiment, the researchers treated normal laboratory mice with antibiotics for 2 weeks, then gave them a norovirus. Antibiotics have upset the balance of immune cells and damage the intestinal mucosa, narrowing of the villi, but as with germ-free mice, the guts of the mice recovered with the help of norovirus. Kernbauer and colleagues then conducted the same experiment, but instead of adding the virus they replaced stunned various bacteria by antibiotics. Each bacterium has helped restore some aspect of the health of the gut, but not the same full range of the virus.
In a final experiment, the team infected mice treated with antibiotics with a pathogen that causes weight loss, diarrhea, and damage to the intestinal wall. Treatment with attenuated these effects. The virus has also helped protect mice against tissue damage from a toxic chemical.
Cadwell, Kernbauer and Ding began to track how the virus gives a hand. They found that stimulates an immune response which comprises a signaling molecule called interferon. "We interferon as a starting point, and now we want to know how interferon is conferred these benefits," said Cadwell
. "The idea that this virus can be beneficial in some way will be very controversial, "since most people think of general virus and norovirus in particular as harmful, says Juris Grasis, an immunologist at the State University of San Diego in California who was not involved in the work. Nevertheless, the study "could give us clues about human health as to what might be important in the immune system to fight or use norovirus."
the work has implications beyond norovirus, Pfeiffer added. investigations of human virome are many viruses that do not cause the disease. "Maybe in some situations, they may be beneficial."
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