The gut virome in inflammatory bowel diseases

Dysbiosis of the microbiome has been extensively studied in inflammatory bowel diseases (IBD). The roles of bacteria and fungi have been studied in detail, but viral communities, an important component of the microbiome, have been less thoroughly investigated. Metagenomics provided a way to fill this gap by using DNA sequencing to enumerate all viruses in a sample, termed the 'virome'. Such methods have now been employed in several studies to assess associations between viral communities and IBD, yielding several commonly seen properties, including an increase in tailed bacteriophage (Caudovirales) and a decrease in the spherical Microviridae. Numerous studies of single human viruses have been carried out, but no one virus has emerged as tightly associated, focusing attention on whole virome communities and further factors. This review provides an overview of research on the human virome in IBD, with emphasis on (1) dynamics of the gut virome, (2) candidate mechanisms of virome alterations with disease, (3) methods for studying the virome, and (4) potentially actionable implications of virome data.