Ricerc@Sapienza

Most viruses first encounter host cells at mucosal surfaces, which are typically colonized by a complex a vast range of commensals and potential pathogenic bacteria, which form a complex microbial community. This community is assumed to be constantly subject to synergistic and competitive interspecies interactions. Disturbances in the equilibrium, for instance due to the acquisition of new bacteria or viruses, may lead to overgrowth and invasion. While evidence suggests potential antagonistic effects where the bacterial microbiome protects the host from viral infection, increasing evidences highlights the severe pathogenicity occurring as a consequence of virus-bacteria interactions in areas inhabited by normally benign members of the native microflora. The immune system may also be involved in this competition, as one viral species might have few escape strategies to evade the immune system and therefore may use co-inhabitants to survive, whereas the reverse phenomenon (i.e. one species may trigger the immune system to combat the other species) may also occur. A better understanding of the impact of virus-bacteria on the mucosal immune response may provide better insight into the pathogenesis of different acute or chronic disease settings.