Yet another study, this one out of Massachusetts General Hospital (one of Harvard’s teaching hospitals) associating inflammatory bowel diseases (IBD) with alteration in the virome. These scientists wanted to move beyond correlation and look for actual causation. Exactly how does the virome affect intestinal tissue?
To figure this out, they used something called “enriched virus-like particles” (VLP) from people with and without IBD, seeing how a part of the human immune system (macrophages) and how intestinal epithelial cells themselves respond to the presence of VLP. Viruses isolated from the colonic tissue of healthy people elicit an anti-inflammatory response and protected the gut cells. Viruses collected from those with IBD provoke an inflammatory response and damage intestinal cells: “IBD-associated enteric viromes promoted inflammation, spontaneously and after DSS-induced colitis, while viruses from non-IBD tissue were protective and also suppressed inflammatory properties of IBD enteric viromes.”[i]
Taking the research a step further, VLP were then introduced into the intestines of healthy mice. The same happened: if the mouse were given viruses from healthy human intestines, they were protected from inflammation as opposed to those given viruses from humans with IBD. They were, therefore, able to conclude that the virome is an autonomous driver of inflammatory bowel diseases: that is, it can cause disease on its own, without even the involvement of other parts of the human biome.
The researchers found a significant elevation of two kinds of viruses in those with IBD: Caudovirales, bacteriophages, and viruses from the Picornavirus family, which are eukaryotic viruses. These latter types of viruses have been associated with the development of diabetes. Thus, they are two potential culprits. But, they also found many, many viruses that are, as yet, unknown and thus, uncategorized. And considering that there are likely at least 100 million species of virus in the human virome, and thus far, about 10,000 of them have been sequenced, it will be awhile before all suspect species have been identified. As one of the lead researchers states, ““[Finding the individual culprits] would be a game-changer in the arena of complex immune and autoimmune diseases.”[ii]
Still, even the knowledge that the virome is a potential leading – or maybe even lead – cause of IBD is an important finding. Before you can come up with a cure, you need to know what you’re curing!
[i] Adiliaghdam, F, et. al. Human enteric viruses autonomously shape inflammatory bowel disease phenotype through divergent innate immunomodulation. Science Immunology. 2022;7(70). DOI: 10.1126/sciimmunol.abn6660