Significance of the Gut Microbiome for Viral Diarrheal and Extra-Intestinal Diseases.

Ulrich Desselberger

doi:10.3390/v13081601

Abstract

The composition of the mammalian gut microbiome is very important for the health and disease of the host. Significant correlations of particular gut microbiota with host immune responsiveness and various infectious and noninfectious host conditions, such as chronic enteric infections, type 2 diabetes, obesity, asthma, and neurological diseases, have been uncovered. Recently, research has moved on to exploring the causalities of such relationships. The metabolites of gut microbiota and those of the host are considered in a ‘holobiontic’ way. It turns out that the host’s diet is a major determinant of the composition of the gut microbiome and its metabolites. Animal models of bacterial and viral intestinal infections have been developed to explore the interrelationships of diet, gut microbiome, and health/disease phenotypes of the host. Dietary fibers can act as prebiotics, and certain bacterial species support the host’s wellbeing as probiotics. In cases of Clostridioides difficile-associated antibiotic-resistant chronic diarrhea, transplantation of fecal microbiomes has sometimes cured the disease. Future research will concentrate on the definition of microbial/host/diet interrelationships which will inform rationales for improving host conditions, in particular in relation to optimization of immune responses to childhood vaccines.

Highlights

The human gut microbiota, comprising bacteria, viruses, fungi, protozoa, and parasites and comprehensively termed the gut microbiome, have received increased attention for about a decade, when it was recognized that their commensal or symbiotic relationship is of great importance for human health, including immune responses correlated with protection from infection or disease [1,2,3,4]
Gnotobiotic piglets transplanted with ‘healthy’ human gut microbiota from children (HHGM: Proteobacteria, Bacteriodetes) or with microbiota from children with weak (‘unhealthy’) immune responses (UHGM: Proteobacteria and Firmicutes) differed in their reaction to challenge with human rotavirus: the HHGM-transplanted animals expanded Bacteriodetes and had less severe diarrhea and virus shedding than UHGM-transplanted animals, which maintained the high prevalence of Firmicutes spp
The interplay between diet, gut microbiota fermentation, and host cellular pathways leads to a complex microbe–host-produced spectrum of metabolites, strongly suggesting that the gut microbiome affects the host’s health in a much more general way than just by its influence on immune responses

Summary

Introduction

The human gut microbiota, comprising bacteria, viruses, fungi, protozoa, and parasites and comprehensively termed the gut microbiome, have received increased attention for about a decade, when it was recognized that their commensal or symbiotic relationship is of great importance for human health, including immune responses correlated with protection from infection or disease [1,2,3,4]. Observational studies initially reported on cotemporal correlations of the composition of the gut microbiome with immune responses or disease outcome [5,6]. More recent studies aimed at identifying causal relationships between metabolic products of the gut microbiome and the host in health and disease [7,8,9]. This review emphasizes the importance of the transition from observational correlation studies to studies exploring causal microbiome–host relationships, which will provide data for rational developments of microbiota as probiotic agents

The Intestinal Microbiome

In Animals

Intestinal Microbiome–Host Interaction via Metabolites

Intestinal Microbiome and Diet

Intestinal Microbiome and Infectious and Non-Infectious Diseases