Efficacy of Probiotics in Prevention of Influenza

Abstract

The human gut microbiota is critical for regulation of whole body metabolism and the immune system. Probiotics provide many benefits on human health by regulating this microbiota. In the prevention of infectious diseases, several probiotic Lactobacillus strains are shown to be effective to enhance the effects of influenza vaccine. These effects are mediated by increment of NK cell population, T-helper type 1 response, and production of virus-specific IgA, IgG, and IgM to inhibit the viral infection. Recently, we have shown that Lactobacillus gasseri LG2055 is effective to prevent influenza by induction of IFNβ production and expression of antiviral genes to inhibit the viral replication. In addition, the inflammatory response is inhibited, and cytokine production to stimulate B cells is induced by the administration of LG2055. Especially, IFNβ inhibits the replication of influenza virus and IFNβ production signal is mediated by IPS-1 through the activation of IRF3 and NF-κB. Therefore, in the future, the regulatory effects on the function or expression of these signaling molecules by the administration of probiotics should be studied. In addition, since the inhibition of FasL-induced apoptosis is effective to protect mice from death by the viral infection, the function of other death receptors, TNFR, DR4, and DR5, or signaling molecules, Siva-1, DAP3, and DELE, should be clarified in the viral replication and apoptosis induction. Further investigation for the regulatory effects of probiotics on the function of these molecules is required and might lead to the development of novel influenza drugs or vaccine adjuvants.