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Or in other words, they are a natural part of our immune defense! New science suggests that mucus in our body is full of viruses that attack bacteria! Those viruses don't hurt us, in fact, they protect us. Commensal viruses....

Viruses and mucus team up to ward off bacteria | Life
Phages may play unforeseen role in immune protection
By Tina Hesman Saey
Web edition: May 20, 2013

The last thing most people would want in their bodies is mucus laden with viruses. But a new study suggests that viruses called bacteriophages, or phages, grab onto mucus and then infect and kill invasive bacteria. The finding, reported May 20 in the Proceedings of the National Academy of Sciences by Forest Rohwer of San Diego State University and colleagues, could mean that some viruses partner with animals and humans to stave off bacterial infections and control the composition of friendly microbes in the body.

Bacteriophages are viruses that break open bacteria, killing them. Researchers have studied bacteriophages for decades, and some disease therapies take advantage of the viruses' bacteria-slaying abilities, says microbiologist Frederic Bushman of the University of Pennsylvania medical school. But the study provides what Bushman says is a revelation that should have been obvious; phage may be a natural part of the immune system. "It's new in a way that is sort of common-sensey," he says.

Previously, researchers thought of mucus mainly as a physical barrier to keep invading organisms from entering the body. The slimy substance made by our noses, intestines and other organs also fights invaders with antimicrobial molecules. Some researchers had found bacteriophages stuck in mucus, but they figured that the mucus had stopped or slowed the viruses. No one realized that the viruses are part of the body's defense, says study coauthor Jeremy Barr, who works in Rohwer's lab. "This is a natural use of phage therapy that has probably been around since mucosal surfaces evolved," Barr says.

Rohwer, who studies corals, had noticed that phages tend to concentrate in mucus. To find out why, the researchers collected mucus from human gums, sea anemones, fish, corals and mouse intestines. Mucus layers had more phages and fewer bacteria than the surrounding environment, suggesting that the viruses helped to limit the number of bacteria allowed into the mucus.

Phages are coated in proteins that latch onto sugars called glycans, anchoring the viruses in the mucus, the team discovered. From there the phages can ambush encroaching bacteria.

So far, the researchers have demonstrated that mucus and phages can work together to protect cells in a dish. The next step, Bushman says, would be determining what happens inside an organism, an experiment the researchers are already planning.


May. 22nd, 2013 12:54 pm (UTC)
Very fascinating! Definitely incorporating this into the Microbiology class next fall. :-)
Also wondering if this could be the key to "auto-immunity"-- maybe our body is mis-recognizing the helpful virus as bad and attacking our own cells which contain the virus?
May. 22nd, 2013 05:22 pm (UTC)
Wellllllll actually the triggers for AI dz are pretty well known and viruses are not at the top of our worries list. More commonly it occurs because of "leaky gut" which activates the immune system to recognize (and attack) epitopes which should be considered "food" or "self". Some people have HLA markers on their cells that are very much like food, esp gluten, and they are highly susceptible to a failure of immune tolerance.

The phages in our mucus are there because there is a constant stream of food for them. Phages tend to be very specific: one particular type of bacteriophage will infect one particular type of bacterium. Phage therapy involves finding the right one to attack the bacteria involved...and nature does this for us. The lovely thing is that when the bacterium isn't available, phage populations specific to it naturally reduce.
May. 23rd, 2013 02:08 am (UTC)
Hm, that's interesting! I knew leaky gut could lead to food sensitivity, particularly gluten and casein, but hadn't heard about the mimicry with components of our own system. It's a wonderfully interesting world!
May. 28th, 2013 07:56 pm (UTC)
HLA-DQ2 and HLA-DQ8 seem to be the two cell markers that tangle with gluten. The glutein protein getting to the immune system via failing tight junctions in the intestinal wall is what seems to trigger an assortment of AI disease.



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