Lactobacillus GG as an immune adjuvant for live-attenuated influenza vaccine in healthy adults: a randomized double-blind placebo-controlled trial

L. plantarum, L. salivarius, and L. lactis attenuate Th2 responses and increase Treg frequencies in healthy mice in a strain dependent manner

Many studies on probiotics are aimed at restoring immune homeostasis in patients to prevent disease recurrence or reduce immune-mediated pathology. Of equal interest is the use of probiotics in sub-clinical situations, which are characterized by reduced immune function or low-grade inflammation, with an increased risk of infection or disease as a consequence. Most mechanistic studies focus on the use of probiotics in experimental disease models, which may not be informative for these sub-clinical conditions. To gain better understanding of the effects in the healthy situation, we investigated the immunomodulatory effects of two Lactobacillus probiotic strains, i.e. L. plantarum WCFS1 and L. salivarius UCC118, and a non-probiotic lactococcus strain, i.e. L. lactis MG1363, in healthy mice. We studied the effect of these bacteria on the systemic adaptive immune system after 5 days of administration. Only L. plantarum induced an increase in regulatory CD103⁺ DC and regulatory T cell frequencies in the spleen. However, all three bacterial strains, including L. lactis, reduced specific splenic T helper cell cytokine responses after ex vivo restimulation. The effect on IFN-γ, IL5, IL10, and IL17 production by CD4⁺ and CD8⁺ T cells was dependent on the strain administered. A shared observation was that all three bacterial strains reduced T helper 2 cell frequencies. We demonstrate that systemic immunomodulation is not only observed after treatment with probiotic organisms, but also after treatment with non-probiotic bacteria. Our data demonstrate that in healthy mice, lactobacilli can balance T cell immunity in favor of a more regulatory status, via both regulatory T cell dependent and independent mechanisms in a strain dependent manner.

Randomized controlled trial of probiotics to reduce common cold in schoolchildren

BACKGROUND

The common cold is responsible for the largest proportion of school and work absenteeism and causes a huge economic burden. None of the current interventions is greatly effective for prevention. Our aim was to assess the efficacy of a two-strain combination probiotic for prevention of common cold symptoms in healthy schoolchildren.

METHODS

A double-blind randomized controlled trial was performed during the winter season in a public school of central Thailand. Children, aged 8-13 years, were randomized to receive either a two-strain combination probiotic (Lactobacillus acidophilus and Bifidobacterium bifidum) or placebo given twice a day for 3 months. The primary outcome was any symptom of cold during the 3-month study period while vomiting, diarrhea, use of antibiotics, school absence due to any cause, school absence due to cold and duration of all symptoms were secondary outcomes.

RESULTS

Of the 40 children in each group, 31 (77%) in the probiotic group, compared to 38 (95%) in the placebo group (P= 0.048), developed at least one symptom of cold. Children in the probiotics group had significantly lower risk of fever, cough, rhinorrhea, school absence and school absence related to common cold compared to children in the placebo group. There was no impact on diarrhea and vomiting.

CONCLUSION

A two-strain probiotic combination given twice a day for 3 months was able to reduce the symptoms of the common cold and school absenteeism in schoolchildren.

Probiotics and Immune Response to Exercise

Probiotics are live microorganisms present in several foods and nutritional supplements that may prevent or limit the effects of various illnesses and infections and elicit a range of health benefits in physically active individuals. The primary clinical areas of interest with probiotics include metabolism; gastrointestinal, inflammatory, and functional disorders; the respiratory system; and a range of infections and allergies. The gastrointestinal tract is a key element controlling and regulating adaptation to exercise and physical activity. Gut symptomatology such as nausea, bloating, cramping, pain, diarrhea, and bleeding occurs in some highly active individuals such as athletes, particularly in prolonged exhaustive events. A small number of studies examining probiotic supplementation in highly active individuals indicate modest clinical benefits in terms of reduced frequency, severity, and/or duration of respiratory and gastrointestinal illness. The purported mechanisms of action for probiotics include direct interaction with the gut microbiota, interaction with the gut epithelium and mucosal immune system, and via immune signaling to organs and systems including the liver, brain, and respiratory tract. Future research will identify additional biologically and clinically beneficial strains, validate multicomponent formulations, clarify dose–response issues, and inform the development of guidelines for clinicians, health care practitioners, and the general community.

Control of antiviral immunity by pattern recognition and the microbiome

Human skin and mucosal surfaces are in constant contact with resident and invasive microbes. Recognition of microbial products by receptors of the innate immune system triggers rapid innate defense and transduces signals necessary for initiating and maintaining the adaptive immune responses. Microbial sensing by innate pattern-recognition receptors is not restricted to pathogens. Rather, proper development, function, and maintenance of innate and adaptive immunity rely on continuous recognition of products derived from the microorganisms indigenous to the internal and external surfaces of mammalian host. Tonic immune activation by the resident microbiota governs host susceptibility to intestinal and extra-intestinal infections, including those caused by viruses. This review highlights recent developments in innate viral recognition leading to adaptive immunity, and discusses potential links between viruses, microbiota, and the host immune system. Furthermore, we discuss the possible roles of microbiome in chronic viral infection and pathogenesis of autoimmune disease and speculate on the benefit for probiotic therapies against such diseases.

Daily intake of heat-killed Lactobacillus plantarum L-137 enhances type I interferon production in healthy humans and pigs

We have previously reported that oral administration of heat-killed Lactobacillus plantarum L-137 (HK L-137) stimulates innate immunity for production of type I interferon (IFN) which subsequently augments host defense against influenza A virus infection in mice. We here examined the effect of HK L-137 intake on type I IFN in humans. Sixteen subjects were randomly assigned to receive a tablet containing 10 mg of HK L-137 or a matching tablet for 8 weeks and the serum levels of type I IFN were examined before and after the first or second dose of the trivalent inactivated influenza vaccine. There were no differences in the seroresponse rate, the seroprotection rate and the geometric mean Ab titers after either the first or second dose of vaccine between the HK L-137 group and the control group. On the other hand, the levels of IFN-β were significantly higher in the HK L-137 group than in the control group before vaccination although the vaccination conferred little additional induction of IFN-β. We further examined IFN-β gene expression in the whole blood cells of pigs fed on a diet containing HK L-137 and found that the IFN-β mRNA levels were significantly higher in the HK L-137 group than in the control group. The finding that daily intake of HK L-137 enhances type I IFN production and host defense against influenza A virus infection in mice may be applied to at least two additional species.

A review of the pharmacobiotic regulation of gastrointestinal inflammation by probiotics, commensal bacteria and prebiotics

The idea that microbes induce disease has steered medical research toward the discovery of antibacterial products for the prevention and treatment of microbial infections. The twentieth century saw increasing dependency on antimicrobials as mainline therapy accentuating the notion that bacterial interactions with humans were to be avoided or desirably controlled. The last two decades, though, have seen a refocusing of thinking and research effort directed towards elucidating the critical inter-relationships between the gut microbiome and its host that control health/wellness or disease. This research has redefined the interactions between gut microbes and vertebrates, now recognizing that the microbial active cohort and its mammalian host have shared co-evolutionary metabolic interactions that span millennia. Microbial interactions in the gastrointestinal tract provide the necessary cues for the development of regulated pro- and anti-inflammatory signals that promotes immunological tolerance, metabolic regulation and other factors which may then control local and extra-intestinal inflammation. Pharmacobiotics, using nutritional and functional food additives to regulate the gut microbiome, will be an exciting growth area of therapeutics, developing alongside an increased scientific understanding of gut-microbiome symbiosis in health and disease.

Multi-species biofilms: how to avoid unfriendly neighbors

Multi-species biofilm communities are environments in which complex but ill understood exchanges between bacteria occur. Although monospecies cultures are still widely used in the laboratory, new approaches have been undertaken to study interspecies interactions within mixed communities. This review describes our current understanding of competitive relationships involving nonbiocidal biosurfactants, enzymes, and metabolites produced by bacteria and other microorganisms. These molecules target all steps of biofilm formation, ranging from inhibition of initial adhesion to matrix degradation, jamming of cell-cell communications, and induction of biofilm dispersion. This review presents available data on nonbiocidal molecules and provides a new perspective on competitive interactions within biofilms that could lead to antibiofilm strategies of potential biomedical interest.

The role of nutrition in enhancing immunity in aging

Aging is associated with declined immune function, particularly T cell-mediated activity, which contributes to increased morbidity and mortality from infectious disease and cancer in the elderly. Studies have shown that nutritional intervention may be a promising approach to reversing impaired immune function and diminished resistance to infection with aging. However, controversy exists concerning every nutritional regimen tested to date. In this article, we will review the progress of research in this field with a focus on nutrition factor information that is relatively abundant in the literature. While vitamin E deficiency is rare, intake above recommended levels can enhance T cell function in aged animals and humans. This effect is believed to contribute toward increased resistance to influenza infection in animals and reduced incidence of upper respiratory infection in the elderly. Zinc deficiency, common in the elderly, is linked to impaired immune function and increased risk for acquiring infection, which can be rectified by zinc supplementation. However, higher than recommended upper limits of zinc may adversely affect immune function. Probiotics are increasingly being recognized as an effective, immune-modulating nutritional factor. However, to be effective, they require an adequate supplementation period; additionally, their effects are strain-specific and among certain strains, a synergistic effect is observed. Increased intake of fish or n-3 PUFA may be beneficial to inflammatory and autoimmune disorders as well as to several age-related diseases. Conversely, the immunosuppressive effect of fish oils on T cell-mediated function has raised concerns regarding their impact on resistance to infection. Caloric restriction (CR) is shown to delay immunosenescence in animals, but this effect needs to be verified in humans. Timing for CR initiation may be important to determine whether CR is effective or even beneficial at all. Recent studies have suggested that CR, which is effective at improving the immune response of unchallenged animals, might compromise the host's defense against pathogenic infection and result in higher morbidity and mortality. The studies published thus far describe a critical role for nutrition in maintaining the immune response of the aged, but they also indicate the need for a more in-depth, wholestic approach to determining the optimal nutritional strategies that would maintain a healthy immune system in the elderly and promote their resistance to infection and other immune-related diseases.

New insights into the impact of the intestinal microbiota on health and disease: a symposium report

The present report summarises key insights from a recent symposium focusing on the impact of the intestinal microbiota on health and disease. A more appropriate definition of health was proposed since health maintenance is a dynamic process better assessed in terms of ability to adapt to stress and maintain physiological homeostasis. Biomarkers specifically for health are needed; use of challenge models and subjects with suboptimal health or specific disease risk were advised. The complexity of interactions between external factors, the intestinal epithelium, intestinal microbiota, the immune system and health was exemplified by describing the effects of antibiotics, the Western diet and non-digestible carbohydrates on the microbiota. The association of certain bacteria with different states of health or disease was acknowledged but also that is not always clear whether this is a cause or effect. Recent identification of three robust faecal metagenome clusters may advance this understanding. It was speculated that knowledge of the intestinal microbiota profile may eventually help in the diagnosis of health risks and choice of therapy. It was agreed that beneficial manipulation of the commensal microbiota can improve health outcome. For this purpose, three areas were reviewed. Firstly, research into probiotics as vaccine adjuvants was considered useful for substantiation of immune function claims. Secondly, positive results with certain probiotics and synbiotics for colorectal cancer are emerging, mostly fromin vitroand animal studies. Finally, studies in endurance athletes have shown strain-specific probiotic benefit in terms of maintenance of immune function and, for certain strains, reduction of episodes of respiratory and/or gastrointestinal tract infections.

High-level mucosal and systemic immune responses induced by oral administration with Lactobacillus-expressed porcine epidemic diarrhea virus (PEDV) S1 region combined with Lactobacillus-expressed N protein

To develop effective mucosal vaccine formulation against porcine epidemic diarrhea virus (PEDV) infection, the DNA fragments encoding spike protein immunodominant region S1 and nucleocapsid N of PEDV were inserted into pPG1 (surface-displayed) or pPG2 (secretory) plasmids followed by electrotransformation into Lactobacillus casei (Lc) to yield four recombinant strains: PG1-S1, PG2-S1, PG1-N, and PG2-N. After intragastric administration, it was observed that live Lc-expressing S1 protein combined with Lc-expressing N protein could elicit much more potent mucosal and systemic immune responses than the former alone (P < 0.001), however slightly inferior to the latter alone (P > 0.05). Furthermore, the surface-displayed mixture (PG1-S1+ PG1-N) revealed stronger immunogenicity than the secretory mixture (PG2-S1+ PG2-N) as well as PEDV-neutralizing potency in vitro (P < 0.001). On 49th day after the last immunization, splenocytes were prepared from mice immunized with surface-displayed mixture, secretory mixture and negative control to be stimulated by purified N and S protein, respectively. The results of ELISA analysis showed that N protein was capable of inducing a higher level of IL-4 (P < 0.001) and IFN-γ (P < 0.001) than S1 protein in the immunized mice. Taken together, Lc-expressed N protein as molecular adjuvant or immunoenhancer was able to effectively facilitate the induction of mucosal and systemic immune responses by Lc-expressing S1 region.

Mucosal and systemic immune responses induced by recombinant Lactobacillus spp. expressing the hemagglutinin of the avian influenza virus H5N1

To develop a safe, effective, and convenient vaccine for the prevention of highly pathogenic avian influenza (HPAI), we have successfully constructed two recombinant lactobacillus strains (LA4356-pH and DLD17-pH) that express the foreign HPAI virus protein hemagglutinin 1 (HA(1)). The mucosal and systemic immune responses triggered by these two recombinant lactobacilli following oral administration to BALB/c mice were evaluated. The results showed that both LA4356-pH and DLD17-pH could significantly increase the specific anti-HA(1) IgA antibody level in the mucosa and the anti-HA(1) IgG level in serum, as well as stimulating the splenic lymphocyte proliferative reaction through increased expression of interleukin-4 (IL-4). Compared with LA4356-pH, DLD17-pH was more effective at inducing systemic and mucosal immune responses, with higher anti-HA(1)-specific IgA and IgG levels. Therefore, DLD17-pH could be a promising oral vaccine candidate against HPAI.

Diverse microbial exposure - consequences for vaccine development

Numerous epidemiological studies suggest that there is an inverse relationship between "immunologically mediated diseases of affluence", such as allergy, diabetes and inflammatory bowel disease on one hand and few infections encountered in early childhood, on the other hand. Careful analysis of the epidemiological, clinical and animal studies taken together, however, suggests that the protection is mediated by broad exposure to a wealth of commensal, non-pathogenic microorganisms early in life, rather than by infections. Microbial exposure has little relationship with "hygiene" in the usual meaning of the word and the term "hygiene hypothesis" is therefore misleading. A better term would be "microbial deprivation hypothesis". The suggestion that childhood infections would protect against allergic disease led to unfortunate speculations that vaccinations would increase the risk for allergies and diabetes. Numerous epidemiological studies have therefore been conducted, searching for a possible relationship between various childhood vaccinations on one hand and allergy on the other hand. It is reasonable from these studies to conclude that vaccinations against infectious agents neither significantly increase, nor reduce the likelihood of immunologically mediated diseases. It is established that the postnatal maturation of immune regulation is largely driven by exposure to microbes. Germ free animals manifest excessive immune responses when immunised and they do not develop normal immune regulatory function. The gut is by far the largest source of microbial exposure, as the human gut microbiome contains up to 1014 bacteria, i.e. ten times the number of cells in the human body. Several studies in recent years have shown differences in the composition of the gut microbiota between allergic and non-allergic individuals and between infants living in countries with a low and a high prevalence of immune mediated diseases. The administration of probiotic bacteria to pregnant mothers and postnatal to their infants has immune modulatory effects. So far, however, probiotic bacteria do not seem to significantly enhance immune responses to vaccines. The potential to improve vaccine responses by modifying the gut microbiota in infants and the possibility to employ probiotic bacteria as adjuvants and/or delivery vehicles, is currently explored in several laboratories. Although to date few clinical results have been reported, experimental studies have shown some encouraging results.

Probiotics and immune health

PURPOSE OF REVIEW

The beneficial effects of probiotics have been demonstrated in many diseases. One of the major mechanisms of probiotic action is through the regulation of host immune response. This review highlights the recent scientific research findings that advance our understanding of probiotic regulation of the host immune response with potential application for disease prevention and treatment.

RECENT FINDINGS

Probiotic genomic and proteomic studies have identified several genes and specific compounds derived from probiotics, which mediate immunoregulatory effects. Studies regarding the biological consequences of probiotics in host immunity suggested that they regulate the functions of systemic and mucosal immune cells and intestinal epithelial cells. Thus, probiotics showed therapeutic potential for diseases, including several immune response-related diseases, such as allergy, eczema, viral infection, and potentiating vaccination responses.

SUMMARY

Probiotics may provide novel approaches for both disease prevention and treatment. However, the results of clinical studies regarding probiotic application are preliminary and require further confirmation.

Immunomodulatory mechanisms of lactobacilli

Over the past decade it has become clear that lactobacilli and other probiotic and commensal organisms can interact with mucosal immune cells or epithelial cells lining the mucosa to modulate specific functions of the mucosal immune system. The most well understood signalling mechanisms involve the innate pattern recognition receptors such as Toll-like receptors, nucleotide oligomerization domain-like receptors and C-type lectin receptors. Binding of microbe-associated molecular patterns with these receptors can activate antigen presenting cells and modulate their function through the expression of surface receptors, secreted cytokines and chemokines. In vitro the cytokine response of human peripheral blood mononuclear cells and dendritic cells to lactobacilli can be strikingly different depending on both the bacterial species and the strain. Several factors have been identified in lactobacilli that influence the immune response in vitro and in vivo including cell surface carbohydrates, enzymes modifying the structure of lipoteichoic acids and metabolites. In mice mechanistic studies point to a role for the homeostatic control of inducible T regulatory cells in the mucosal tissues as one possible immunomodulatory mechanism. Increasing evidence also suggests that induction of epithelial signalling by intestinal lactobacilli can modulate barrier functions, defensin production and regulate inflammatory signalling. Other probiotic mechanisms include modulation of the T cell effector subsets, enhancement of humoral immunity and interactions with the epithelial-associated dendritic cells and macrophages. A major challenge for the future will be to gain more knowledge about the interactions occurring between lactobacilli and the host in vivo and to understand the molecular basis of innate signalling in response to whole bacteria which trigger multiple signalling pathways.