Lactobacillus gasseri SBT2055 Stimulates Immunoglobulin Production and Innate Immunity after Influenza Vaccination in Healthy Adult Volunteers: a Randomized, Double-blind, Placebo-controlled, Parallel-group Study

Abstract

Background: Lactobacillus gasseri strain SBT2055 (LG2055) is a human intestine-originating probiotic bacterium and potent probiotic known to exert various health promotion effects, including prevention of abdominal adiposity in rats and humans. A recent finding in mice has suggested that oral administration of LG2055 induces a protective effect against influenza A virus infection. In this context, evidence for efficacy of LG2055 using a human clinical trial was imminently required.Methods: To confirm this in humans, a randomized, double-blind, placebo-controlled, parallel-group study in healthy adult volunteers was conducted to examine the effect of drinkable yogurt (DY) containing LG2055 on influenza vaccine-specific antibody responses as the primary objective and innate immune responses as the secondary objective. Subjects were asked to consume 100 g/day of DY with LG2055 (LG2055 group; n = 94) or without LG2055 (placebo group; n = 94) for 16 weeks. After 4 weeks, all subjects received a trivalent influenza vaccine. Results: We found that the intake of LG2055 DY increased hemagglutination inhibition titers against influenza viruses A/H1N1 and B and the rate of seroprotection against influenza B after vaccination as compared with the intake of placebo DY by healthy volunteers. In support of this result, we confirmed that total IgG and IgA levels in plasma and sIgA production in saliva were also higher in the LG2055 group than in the placebo group. Furthermore, the intake of LG2055 DY enhanced natural killer cell activity and myxovirus resistance A gene expression, which is one of the antiviral genes stimulated by type I or type III Interferons in peripheral blood mononuclear cells.Conclusions: These results strongly indicate that LG2055 activates both the innate and adaptive human immune responses, suggesting the potential to prevent influenza virus infections by providing specific probiotics as complementary foods.Keywords: human clinical trial, innate immunity, influenza virus, Lactobacillus gasseri, vaccine