Human Colostrum and Derived Extracellular Vesicles Prevent Infection by Human Rotavirus and Respiratory Syncytial Virus in Vitro

Background: It is known that breastfeeding protects the infant from enteric and respiratory infections; however, the antiviral properties of human milk against enteric and respiratory viruses are largely unexplored. Research aims: To explore the antiviral activity of human preterm colostrum against rotavirus and respiratory syncytial virus and to assess whether the derived extracellular vesicle contribute to this activity. Methods: We used a cross-sectional, prospective two-group non-experimental design. Colostra were collected from mothers of preterm newborns (N = 10) and extracellular vesicles were purified and characterized. The antiviral activity of colostra and derived extracellular vesicles were tested in vitro against rotavirus and respiratory syncytial virus and the step of viral replication inhibited by extracellular vesicles was investigated. Results: Each sample of colostrum and colostrum-derived extracellular vesicles had significant antiviral activity with a wide interpersonal variability. Mechanism of action studies demonstrated that extracellular vesicles acted by interfering with the early steps of the viral replicative cycle. Conclusion: We demonstrated the intrinsic antiviral activity of human colostrum against rotavirus and respiratory syncytial virus and we showed that extracellular vesicles substantially contribute to the overall protective effect. Our results contribute to unravelling novel mechanisms underlying the functional role of human milk as a protective and therapeutic agent in preterm infants.