A recent review by Julie Pfeiffer and Herbert Virgin suggests that studying the interactions between the enteric virome, other microbes in the microbiota and host genes could be a useful tool with therapeutic benefits.
The mammalian gut microbiome is a complex community in which the virome plays an important role in regulating immunity and homeostasis. Nevertheless, recent data indicate that the enteric virome has been profoundly underestimated and researchers say enteric viruses (poliovirus, retrovirus, norovirus, reovirus) can interact with other microbial constituents that inhabit the intestine through both direct and indirect mechanisms. The coordinated interactions between these different microbial kingdoms – including viruses, bacteria, fungi, eukaryotes and helminths (termed “transkingdom interactions”) – have important effects on enteric and systemic immune responses. Genetic variations in the host also affect these interactions and can influence the occurrence of enteric viral diseases.
In the review, researchers highlight several ways in which gut microbes influence viral infection and transmission. By using germ-free and antibiotic-treated mice infected with human and murine viruses, particular focus has been placed on mechanisms by which bacteria and other components of the microbiome promote enteric virus replication and transmission. For instance, gut bacteria are required for efficient mouse mammary tumour virus (MMTV) transmission from mother to offspring. Interestingly, the effects of microbiota on enteric viruses depend on the virus’ route of transmission, with the natural oral route the most appropriate. In addition, several enteric viruses may induce host immune tolerance through attachment to bacterial constituents such as lipopolysaccharide, resulting in viral replication and transmission.
Furthermore, the authors note that bacterial microbiota has an essential role in maintaining antiviral intestinal immune responses. In this context, the presence of an innate immunity in the gut environment contributes to viral clearance. As a result, strategies that enhance these innate immune mechanisms may be useful in controlling viral infections.
In conclusion, all microbial communities and immune cells in the gut depend on each other for survival and may play an essential role in dictating responses to infectious agents. These interactions could be a target for further research concerning the effects of microbiota on human health and disease.
Pfeiffer JK, Virgin HW. Transkingdom control of viral infection and immunity in the mammalian intestine. Science. 2016;351(6270):aad58721-5.