Employing Experimental Gnotobiotic Models to Decipher the Host-Microbiota Cross-Talk in Health and Disease

Eukaryotic organisms evolved in the world dominated by bacteria and archaea. Instead of engaging in a daunting task of keeping their exposed surfaces germ-free they opted to interact and form diverse symbiotic relationships with the microbes that surrounded them. Nowadays, mucosal surfaces of animals and humans are associated with specific microbial communities that affect various aspects of their host physiology and, most notably, the development and fine-tuning of the immune system. In the last decade we have seen a significant advancement in the microbiome research and renewed interest in the critical role of the host-associated microbes in homeostasis and disease. Yet, there are still vast gaps in our understanding of the fundamental basis of this microbiota-host dialogue.

The most divers and most numerous microbial populations can be found in the gastrointestinal tract. Changes in the gut microbiome and/or breakdown in the host-microbiota cross-talk have been associated with immune-mediated diseases such as allergy, inflammatory bowel disease, rheumatoid arthritis multiple sclerosis, diabetes and obesity. However, descriptive reports predominate mechanistic studies and the complexity of the gut microbial ecosystem makes it difficult to understand the host-microbiota cross-talk that regulates the immune responses in health and disease.

The most powerful tool for studying host-microbe interactions has been the germ-free and gnotobiotic animal models. Though historically mostly rodents, in recent years new both invertebrate (e.g. Drosophila) and vertebrate (e.g. fish, piglet) models are being successfully implemented. The possibility to colonize germ-free animals with defined specific bacterial species or consortium of microbes creates the unique opportunity to evaluate their impact on the host physiology and immune system.

With this Research Topic we aim to gather a collection of articles that shed light on and deepen our current understanding of the interplay between specific bacterial strains, defined bacterial consortia, bacterial components or bacterial metabolic products with the multicellular host’s innate and/or adaptive immune system and how this cross-talk can be implemented for prophylactic and/or therapeutic strategies against diseases. The submission is opened to any article format accepted by Frontiers in Immunology.