Donata Medaglini , Microbiome and Immunology, University of Siena, Italy

Microbiome and Immunology
The microbiome plays a fundamental role on the function and modulation of the host immune system. In return, the immune system has largely evolved as a mean to maintain the symbiotic relationship of the host with the highly diverse and evolving microbes. The immune system/microbiome alliance allows the maintenance of regulatory pathways involved in the immune homeostasis. Severity of some viral and bacterial infections is influenced by modulation of the host immune response by the local bacterial ecosystem. Commensals can directly and dynamically interact with pathogens and immune cells and the results of this interaction can define the outcome and pathogenesis of a given disease. Recent findings suggest novel complex mechanisms by which the microbiome impacts immune cell development and differentiation, showing that the composition of microbiota may ultimately affect vaccine efficacy. System biology applied to vaccinology (systems vaccinology), has recently demonstrated that the intestinal microbiome contributes to the enhancement of immunity to both a trivalent inactivated influenza vaccine and the inactivated polio vaccine. A clear influence of the intestinal microbiome on immune responses to oral vaccines has been demonstrated with live-attenuated typhoid Ty21a and Shigella dysenteriae 1 vaccines. The status of the host microbiome therefore represents a critical determinant of vaccine efficacy and its alteration, due to genetic or environmental factors, may influence the capacity of vaccines to elicit effective immune responses.