Viruses living in the gut

February 8th, 2015 by Marta Wegorzewska, PhD

This is a story of a dear friend, ulcerative colitis and viruses.

First year of graduate school taught me that ulcerative colitis is a very complex disease involving the colon and rectum, bacteria, an immune system and a lot of questions to which we don’t have any answers to yet. For years that is all I knew about colitis. At that point in my education, colitis was nothing more than a devastating disease and a lot of fascinating questions.

A few years later, I met a student and we naturally became friends. We went to Zumba together, spent our weekends shopping downtown and enjoyed many delicious meals. As we grew closer, I got to sample her life as she sampled mine. I met her significant other, her family, her pet. I also met colitis.

The gut houses diverse populations of bacterial communities. When certain communities are disrupted while others become more prevalent, disease can occur. This is the scientific basis for ulcerative colitis.

It was Thursday at 6pm. We wrapped up our research for the day and headed to our favorite Zumba class. It was just another regular day. We were two happy twenty-something year olds looking forward to our favorite exercise class. We joked about the small things that annoyed us that day while we changed into our Zumba shoes.

Anyone that saw the two of us together would have never guessed that my friend was going to have a flare-up during this class. She left early and I found her sitting in the locker room in the fetal position. Bloody diarrhea was her primary symptom. She was experiencing inflammation in the colon.

The next few days we spent our lunch breaks discussing what could have caused her colon to get inflamed. We are scientists after all; we should be able to figure it out. But we couldn’t. Her life was no different from mine. At times her life was full of euphoria and excitement and other times full of stress. But we are different. She suffers from ulcerative colitis.

Those who suffer from ulcerative colitis have disruptions in the bacterial communities that house the gut. How that translates to disease we still do not know but it is an interesting question in itself as to why those changes occur. In other words, what causes lose of certain populations of bacteria living in the gut?

A group of scientists at Washington University in St Louis have an interesting idea as to why populations of bacterial in the gut may have gone missing. They wondered whether viruses that also reside in the gut may be causing changes in the bacterial communities in the gut. A specific type of viruses called bacteriophages can infect bacteria and eliminate them. These scientists made the interesting observation that people suffering from ulcerative colitis have different and more numerous populations of bacteriophages in their gut that coincided with a loss of certain populations of bacteria. They published their findings last month in Cell, Host and Microbe.

Before we continue this story, I caution you that although these scientists think that viruses may be affecting the community of bacteria that live in the gut, they have not yet proven that it exactly what is happening. They found a connection between the presence of certain viruses that coincide with the absence of certain bacteria. The next question is, are these viruses killing the bacteria that have gone missing? And is this causing colitis? They do not know yet. Nevertheless, it is an interesting observation that may hint at what is going on. It is very well possible that next month you will hear the story of how bacteriophages present in the gut are killing bacteria that are needed to protect against colitis.

Let’s pretend that indeed viruses are causing colitis! If ulcerative colitis can be triggered by a virus, is it contagious? We all have experienced the flu virus and know that if someone at work has the flu, there is a good chance you will get it too. But we also know some viruses, like the flu, are more contagious than others, like Ebola. Depending on how they are transmitted, some viruses are more contagious (airborne viruses) than others (spread through bodily fluids). As far as I can tell, nobody knows. People with ulcerative colitis live with family members that do not have the disease so perhaps it is not transmittable. Whatever the role of these viruses is, I wonder how the viruses getting there and why are only certain people susceptible to their infection?

What do you think? What do you know about viruses and colitis?


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