Lactobacillus pentosus (L. pentosus) strain S-PT84, isolated from Kyoto pickles, enhances splenic natural killer (NK) cell activity, and has high T-helper1 (Th1) cytokine and type 1-IFN (IFN-α) inducing activity. In the present study, we investigated the influence of S-PT84 ingestion on the mucosal immunity of healthy and Salmonella Typhimurium (S. Typhimurium)-infected mice. In the S. Typhimurium infection model, numbers of S. Typhimurium in feces and the spleen were significantly decreased, and body weight loss and deterioration in the general health score of S. Typhimurium-infected mice were improved by S-PT84 ingestion. Oral administration of S-PT84 enhanced IL-5 and IL-6 production from Peyer’s patch cells in vitro, with a concomitant significant increase in IgA production from Peyer’s patch cells, which may explain the mechanism of enhanced IgA production in the small intestine in vivo. These results suggest that S-PT84 ingestion is useful for the maintenance of health or the improvement of certain symptoms during pathogen infection.

Environmental factors during early infancy could theoretically affect immune system development and subsequent risk of allergic disease. One potentially helpful exposure is early infant supplementation with specific probiotic strains. Unlike other exposures, probiotic supplementation is feasible and has a good safety profile. A review of recent randomized, controlled trials suggests that the effect of supplementation with probiotics on preventing the development of allergic disease is mixed. Further studies are needed to define potential mechanisms of action, such as effects on infant microbiota, as well as potential subgroups of patients that may benefit from these interventions.

Much attention has been focused on the biological effects of equol, a metabolite of daidzein produced by intestinal microbiota. However, little is known about the role of isoflavone metabolizing bacteria in the intestinal microbiota. Recently, we isolated a dihydrodaidzein (DHD)-producing Clostridium-like bacterium, strain TM-40, from human feces. We investigated the effects of strain TM-40 on in vitro daidzein metabolism by human fecal microbiota from a male equol producer and two male equol non-producers. In the fecal suspension from the male equol non-producer and DHD producer, DHD was detected in the in vitro fecal incubation of daidzein after addition of TM-40. The DHD concentration increased as the concentration of strain TM-40 increased. In the fecal suspension from the equol producer, the fecal equol production was increased by the addition of strain TM-40. The occupation ratios of Bifidobacterium and Lactobacillales were higher in the equol non-producers than in the equol producer. Adding isoflavone-metabolizing bacteria to the fecal microbiota should facilitate the estimation of the metabolism of isoflavonoids by fecal microbiota. Studies on the interactions among equol-producing microbiota and DHD-producing bacteria might lead to clarification of some of the mechanisms regulating the production of equol by fecal microbiota.

Many Lactobacillus and Lactococcus strains are generally regarded as safe for consumption because they are utilized for food fermentation or inhabit the intestinal mucosa as commensals. Recently, vaccine delivery systems using lactic acid bacteria (LAB) have been under development. Our research group has been investigating the development of oral mucosal vaccines against Salmonella enterica serovar Enteritidis (SE) using Lactobacillus casei IGM393 as an antigen delivery vehicle. Recombinant lactobacilli expressing SE antigens, FliC, SipC, and OmpC, have been constructed and orally administered to mice. Antigen specific immune responses and protective immunity were elicited after the immunization. For adjuvant-delivery, IL-1β-secreting L. casei was also engineered and its effects evaluated in vitro and in vivo. This article reviews a novel approach to the elimination of Salmonella via the development of a vaccine in lactobacilli.

In vitro M cell models, consisting of co-cultures of Caco-2 cells and lymphoid cells, were developed and examined to observe bacterial transport. However, under our experimental conditions, the differentiation of Caco-2 cells into M cell-like cells could not be induced efficiently. To obtain a functionally stable M cell model based on human cells, C2BBe1 cells were screened and co-cultured with human Raji cells. In our co-cultures, increased sialyl Lewis A antigen expression and decreased Ulex europeaus agglutinin 1 binding were observed. Regarding the functional properties of the model, microsphere and lactic acid bacteria transport across the C2BBe1 co-cultures were increased compared with the levels seen in monocultures. The C2BBe1 monolayers that were co-cultured with Raji cells exhibited some M cell features; therefore, we consider our M cell model to be useful for investigating the interactions of bacteria with M cells.

Autonomic nerves, consisting of both sympathetic and parasympathetic nerves, regulate various bodily functions such as blood pressure, body temperature, glucose metabolism, energy metabolism, and digestion. Our studies in rats and mice have demonstrated that food, flavor, and music affect physiological phenomena via changes in autonomic neurotransmissions. Intestinal injection of Lactobacillus johnsonii La1 (NCC533) suppressed sympathetic nerves that innervate the adrenal gland and kidney of urethane-anesthetized rats, lowering blood glucose and blood pressure levels, and excited the gastric parasympathetic nerve, elevating appetite and body weight. In contrast, intestinal injection of Lactobacillus paracasei ST11 (NCC2461) excited sympathetic nerves that innervate white and brown fat and the adrenal gland, increasing lipolysis and body temperature, and suppressed the gastric parasympathetic nerve, reducing appetite and body weight. Interestingly, we found that the hypothalamic suprachiasmatic nucleus (SCN), a master circadian clock, and histamine receptors in histaminergic neurons play important roles in peripheral autonomic control. To investigate the possible role of SCN and histamine receptors in lactobacilli-mediated pathology, we created an SCN-lesion model and experimented with histaminergic blocker injections. SCN lesion or injection of thioperamide, a histamine H3-receptor antagonist, eliminated the suppression of renal sympathetic nerve activity by NCC533, preventing blood pressure decline, and inhibited the enhancement of the gastric parasympathetic nerve induced by NCC533. In addition, diphenhydramine, a histamine H1-receptor antagonist, abolished the increases in renal sympathetic nerve activity and blood pressure caused by NCC2461. Infradiaphragmatic vagotomy eliminated the suppression of renal sympathetic nerve activity by NCC533, but did not affect the excitation of the renal sympathetic nerve by NCC2461. Collectively, these findings strongly suggest that SCN and histamine neurons are involved in the lactobacilli-mediated pathology of autonomic nerves and related physiological changes through abdominal afferent vagal pathway input to the central nervous system.

Isoflavones contained in the root and flower of Kudzu (Pueraria lobata and related species) are suggested to be the critical component for its effects. Although metabolism of soy isoflavones has been well studied, the composition of isoflavones found in Kudzu is completely different from that of soy isoflavones. In the present study, we investigated whether isoflavones found in the flower of Pueraria thomsonii, a species of Kudzu, were metabolized by human fecal microbiota and murine small intestinal enzymes. Among 5 glycosidic isoflavones of the Pueraria thomsonii flower, tectorigenin 7-O-xylosylglucoside, tectoridin, genistin and glycitin were completely hydrolyzed by a homogenate of germfree mouse small intestine without contribution of bacteria. Released aglycones were not further metabolized, except that up to half of glycitein disappeared. Mouse small intestinal enzymes did not metabolize 6-hydroxygenistein 6,7-di-O-glucoside. Isoflavone aglycones as well as 6-hydroxygenistein 6,7-di-O-glucoside were highly metabolized by most of the human fecal suspensions. Metabolites were not detected with the present analytical methods in most cases. Although further investigations of the pharmacokinetics of Pueraria thomsonii flower isoflavones are needed, the results of the present study indicate active metabolism of Pueraria thomsonii flower isoflavones in the human intestine.

Several studies on the pathogenesis of allergy both in man and experimental animals continue to show the importance of commensal bacteria in the gastrointestinal tract in stimulating and directing the immune system. The interest in modulating commensal bacteria flora with pre- and probiotics to prevent and treat food allergy has multiplied in recent years. We recently studied 230 infants with atopic dermatitis and suspected cow’s milk allergy. The infants were randomly allocated to groups which received Lactobacillus GG (LGG), a mixture of four probiotic strains (MIX) or placebo for 4 weeks. We inferred that probiotics induce systemically detectable low-grade inflammation, which may explain the clinical effects and the secretion pattern of cytokines induced by PBMC. To study the ability of probiotics to prevent allergy in children, we recruited 1223 pregnant women carrying fetuses at increased risk of allergy for a double-blind placebo-controlled trial. Mothers used a mixture of four probiotic bacteria or a placebo from the 36th week of gestation. Their infants received the same probiotics plus prebiotic galacto-oligosaccharides for 6 months. At the 2-year follow-up, a total of 925 infants participated. The cumulative incidence of allergic disease did not differ significantly between the synbiotic and the placebo group. However, synbiotics significantly reduced eczema. The preventive effect of synbiotics was more pronounced against IgE-associated diseases. At the 5 year follow-up, 891(88%) of the 1018 intention-to-treat infants attended. In the probiotic and placebo groups, frequencies of allergic symptoms and IgE-associated allergic disease and sensitization were similar, and the frequencies of eczema did not differ between the groups. Atopic eczema, allergic rhinitis and asthma appeared equal frequency in the groups. However, less IgE-associated allergic disease occurred in the cesarean-delivered infants given probiotics. In cesarean-delivered childen, we noticed a delayed rise in bifidobacteria recovery in placebo-treated children which was corrected by pro- and prebiotic supplementation. Indications from studies of feces and blood at the age 6 months suggest that probiotics may enhance both inflammation and immune defence of the gut. The probiotic treatment further stimulated maturation of the immune system since the infants given probiotics showed increased resistance to respiratory infections and improved vaccine antibody responses.

Western medicine has only recently discovered that the intestinal microbiota is a major determinant of the well-being of the host. Although it would be oversimplifying to limit the benefits of breastfeeding compared to cow milk based infant formula to differences in gastrointestinal flora, the impact of the latter has been demonstrated beyond doubt. As a consequence, gastro intestinal flora manipulation with pre- and probiotics added to infant formula or food (mainly milk based products) and/or with food supplements have become a priority area of high quality research. The composition of intestinal microbiota can be manipulated with “biotics”: antibiotics, prebiotics and probiotics. Commercialised pre- and probiotic products differ in composition and dose. Major threats to the concept of developing a major role for intestinal microbiota manipulation on health are the commercialisation of products claiming health benefits that have not been validated. Legislation of food supplements and medication differs substantially and allows commercialisation of poor quality food supplements, what will result in negative experiences. Medicinal products can only be advertised for which there is scientific proof of benefit that has been demonstrated with “the same product with the same dose in the same indication”. Specificity of prebiotics and probiotics strains and product specificity are of importance, although high quality evidence for this assertion is missing. Dose-efficacy studies are urgently needed. Probiotics are “generally regarded as safe”, but side effects such as septicemia and fungemia have sometimes been reported in high-risk situations.

Recent studies of several animal models have shown beneficial effects of probiotics against allergic responses. However, few reports have examined the effects of probiotics on allergic nasal symptoms such as sneezing and nasal obstruction in animal models of allergic rhinitis. This study evaluated the efficacy of Bifidobacterium bifidum G9-1 (BBG9-1) on antigen-induced nasal symptoms using guinea pig models of allergic rhinitis. Oral administration of BBG9-1 significantly inhibited antigen-induced allergic nasal reactions such as sneezing and nasal obstruction. Our results suggest that BBG9-1 may be useful for alleviating nasal symptoms in patients with allergic rhinitis.