Disease-Specific Alterations in the Enteric Virome in Inflammatory Bowel Disease, Norman J, Handley S, et al, Cell 160, 1–14, 2015
http://www.cell.com/abstract/S0092-8674(15)00003-3 (It has a picture that describes its findings)
There has been a great deal of interest and research into the field of the microbiota in IBD in recent years, often discussed in this blog. However, this research has largely been about the bacteria that make up the contents of the gut in health and disease, and there has been little work on viruses. Viruses are extremely small compared to bacteria. Viruses in the intestine can broadly be divided as viruses in their own right (like classical viral infections that humans can get) or viral contents of bacteria (called “bacteriophages”). Like bacteria, the normal viral contents of individual guts (the “virome”) appear to differ greatly between people, but the significance of this in IBD is unknown.
This study looked at the virome of IBD patients, their household members (ie looking for whether who you lived with affected the viruses that you have), and other controls. This was done in 3 different populations; Chicago, Los Angeles, Boston (all USA) and Cambridge (UK). The initial results showed that the bacteriophages (the viruses that live inside bacteria) were the most abundant. This was previously known in healthy people, but there also appeared to be differences in IBD patients. Specifically, there was an increase in the richness of the Caudovirales species of virus (a bacteriophage) in IBD compared to household members without IBD; specific types of this virus were common depending on the diagnosis (UC or CD), and the physical location.
The authors speculate considerably on the significance of their findings. They suggest that viruses that affect the gut bacteria may have importance consequences for the interaction between the gut contents and the body’s immune system (especially in IBD). They also comment on the very large difficulties in studying this area, as it is extremely difficult to isolate these viruses, and many of them are very poorly understood. Therefore this study, and others, may be missing or wrongly characterising many of the viruses in the gut simply because they are still unknown.
Overall I think this is an interesting study that raises a new issue of complexity in understanding the microbiota. With new technologies to study these viruses in greater detail this may be an area to watch.