Beyond the gut bacterial microbiota: The gut virome

The gastrointestinal tract is colonized with a highly different population of bacterial, viral, ad fungal species; viruses are reported to be dominant. The composition of gut virome is closely related to dietary habits and surrounding environment. Host and their intestinal microbes live in a dynamic equilibrium and viruses stimulate a low degree of immune responses without causing symptoms (host tolerance). However, intestinal phages could lead to a rupture of eubiosis and may contribute to the shift from health to disease in humans and animals. Viral nucleic acids and other products of lysis of bacteria serve as pathogen-associated molecular patterns (PAMPs) and could trigger specific inflammatory modulations. At the same time, phages could elicit innate antiviral immune responses. Toll-like receptors (TLRs) operated as innate antiviral immune sensors and their activation triggers signaling cascades that lead to inflammatory response. J. Med. Virol. 88:1467–1472, 2016. © 2016 Wiley Periodicals, Inc.