Effects of Intestinal Fungi and Viruses on Immune Responses and Inflammatory Bowel Diseases

The intestinal microbiota comprises diverse fungal and viral components, in addition to bacteria. These microbes interact with the immune system and affect human physiology. Advances in metagenomics have associated inflammatory and autoimmune diseases with alterations in fungal and viral species in the gut. Studies of animal models have found that commensal fungi and viruses can activate hostprotective immune pathways related to epithelial barrier integrity, but can also induce reactions that contribute to events associated with inflammatory bowel disease. Changes in our environment associated with modernization and the COVID-19 pandemic have exposed humans to new fungi and viruses, with unknown consequences. We review the lessons learned from studies of animal viruses and fungi commonly detected in the human gut and how these might affect health and intestinal disease.

Automated summary

The intestinal microbiota is composed of a variety of fungal and viral components in addition to bacteria, which interact with the immune system and impact human physiology. Studies have shown that alterations in fungal and viral species in the gut are associated with inflammatory and autoimmune diseases, with potential to activate host-protective immune pathways while also contributing to inflammatory bowel disease. Modernization and the COVID-19 pandemic have introduced humans to new fungi and viruses, the consequences of which remain unknown. Lessons learned from animal studies on common gut viruses and fungi shed light on their impacts on health and intestinal diseases.