The intestinal microbiota and viral susceptibility

Abstract

Many infections start with microbial invasion of mucosal surfaces, which are typically colonized by a community of resident microbes. A growing body of literature demonstrates that the resident microbiota plays a significant role in host susceptibility to pathogens. Recent work has largely focused on the considerable effect that the intestinal microbiota can have upon bacterial pathogenesis. These studies reveal many significant gaps in our knowledge about the mechanisms by which the resident community impacts pathogen invasion and the nature of the ensuing host immune response. It is likely that as viral pathogens become the focus of studies that examine microbiota-host interaction, substantial effects of resident communities exerted via diverse mechanisms will be elucidated. Here we provide a perspective of the exciting emerging field that examines how the intestinal microbiota influences host susceptibility to viruses.

Keywords: infection; intestinal microbiota; mucosal immune system; pathogen; virus.

Figure 1

Potential roles that commensal microbes within the intestine may play in host susceptibility to virus. (A) A commensal may inhibit a virus (top left panel) directly (a), or indirectly at a local site (b), or at a peripheral site such as the lung (c). Conversely, this same commensal may promote viral infectivity (lower left panel) via these same mechanisms, such as directly activating the virus (a), recruiting leukocytes that promote/permit viral replication (b), or setting systemic immune parameters that are permissive for viral replication at a distant site (c). (B) Other commensals may have opposite effects on the same viruses, and alterations in microbiota composition or functional state may shift the balance in favor of the first or second scenario.