The use of probiotics as antivirals

Probiotics are microorganisms known for their potential health benefits. In particular, several studies have demonstrated that the composition of intestinal microbiota has a considerable impact on health. Imbalances of the intestinal microbiome and beyond, or dysbiosis, have been associated with the development of various pathologies. To date, it is known that probiotics can be advantageous in numerous ways. For example, they can modulate the immune system, producing organic acids, enhancing barrier function, and releasing small molecules that affect the entire host system. Consequently, the study of probiotics and their potential health benefits represents a field of research of great interest and very promising for the future. In particular, recent studies are investigating the possibility of using probiotics as antivirals. Viral infections are a global concern, and the existing tools to prevent or treat infections primarily include vaccines and antiviral drugs. While there are several drugs available for the treatment of viral infections, viruses evolve and become resistant to these drugs. One mechanism behind this resistance is the selection of mutations during the replication process that can make them resistant to drugs. The emergence of resistant mutants is a rapidly increasing phenomenon and represents a serious issue in the healthcare field. Moreover, the use of antiviral drugs is associated with various adverse effects and cell cytotoxicity. Probiotics, on the other hand, have long been taken for their beneficial effects on human health, without any obvious side effect. For this reason, studying the mechanism of action of probiotics to contrast the pathogen’s invasion may show new approaches and therapies for the treatment of viral infections. This thesis presents three studies that showcase the efficacy of probiotics as antivirals. In particular, these research papers evaluate the efficacy of probiotics in counteracting infections (in vitro and in vivo) by herpes simplex virus type 1 (HSV-1), human papillomavirus (HPV), and human immunodeficiency virus (HIV).