Selection of probiotic bacteria for prevention of allergic diseases: immunomodulation of neonatal dendritic cells

Bifidobacterium modulation of tumor immunotherapy and its mechanism

The advent of tumor immunotherapy in patients has revolutionized the treatment of tumors and significantly improved survival rates for a wide range of tumors. However, the full therapeutic potential of immune checkpoint inhibitors (ICIs) has yet to be realized, as not all patients have a lasting survival benefit from them, and a significant proportion of patients show primary or acquired resistance to immunotherapy. Bifidobacterium is one of the most common probiotics, and its antitumor and immunomodulatory effects have been demonstrated in recent years, but its immunomodulatory effects in tumors, especially on ICIs and in combination, have not been extensively studied in clinical practice, and its effects on the immune system and the mechanisms that modulate immunotherapy are largely unknown. Therefore, this review will focus on the immunomodulatory effects of Bifidobacteria in malignancies and the possible mechanisms of action of Bifidobacteria on immunotherapy in the hope of providing a basis for further research and better application of Bifidobacteria in clinical practice.

The gut-lung axis and asthma susceptibility in early life

Asthma is the most common chronic disease among children, with more than 300 million cases worldwide. Over the past several decades, asthma incidence has grown, and epidemiological studies identify the modernized lifestyle as playing a strong contributing role in this phenomenon. In particular, lifestyle factors that modify the maternal gut microbiome during pregnancy, or the infant microbiome in early life, can act as developmental programming events which determine health or disease susceptibility later in life. Microbial colonization of the gut begins at birth, and factors such as delivery mode, breastfeeding, diet, antibiotic use, and exposure to environmental bacteria influence the development of the infant microbiome. Colonization of the gut microbiome is crucial for proper immune system development and disruptions to this process can predispose a child to asthma development. Here, we describe the importance of early-life events for shaping immune responses along the gut-lung axis and why they may provide a window of opportunity for asthma prevention.

Assessment of a Multispecies Probiotic Supplement for Relief of Seasonal Allergic Rhinitis: A Randomized Double-Blind Placebo-Controlled Trial

Background: Early phase clinical research provided initial support for the use of a multispecies probiotic supplement to improve quality of life (QoL) in adults with seasonal allergic rhinitis (AR) and reduce the use of AR symptom relieving medication. This study aimed to confirm these early phase findings in a double-blind randomized placebo-controlled trial. Methods: Individuals, aged 18-65 years, with a minimum 2-year history of AR, moderate-to-severe AR symptoms, and a positive radio-allergosorbent test to Bermuda (Couch) Grass were randomized to receive either a multispecies probiotic supplement (total colony-forming units 4 × 10⁹/day) or placebo twice daily for 8 weeks. A mini-rhinoconjunctivitis quality of life questionnaire (mRQLQ) scale was administered at screening, days 0, 28, and 56. The proportion of participants with a >0.7 improvement in mRQLQ was the primary outcome. Participants also completed a daily symptom and medication diary during the supplementation period. Results: There were 165 participants randomized, with 142 included in the primary outcome analysis. The percentage of participants meeting the threshold for a clinically meaningful reduction in the mRQLQ from days 0 to 56 was not significantly different between groups (61% vs. 62%, p = 0.90). However, 76 participants had a clinically meaningful improvement in QoL (decrease in mRQLQ >0.7) prior to the start of supplementation (screening to day 0). Conclusion: Changes in self-reported QoL and other disease severity metrics between screening and the start of supplementation limited the ability to discern an effect of supplementation and highlight the need for adaptive clinical trial designs in allergy research. Clinical Trial Registration: The trial was registered with the Australia and New Zealand Clinical Trials Registry (ACTRN12619001319167).

Different probiotic strains alter human cord blood monocyte responses

BACKGROUND

Probiotics have a protective effect on various diseases. In neonatology, they are predominantly used to prevent necrotising enterocolitis (NEC), a severe inflammatory disease of the neonatal intestine. The mechanisms by which probiotics act are diverse; little is known about their direct effect on neonatal immune cells.

METHODS

In this study, we investigated the effect of probiotics on the functions of neonatal monocytes in an in vitro model using three different strains (Lactobacillus rhamnosus (LR), Lactobacillus acidophilus (LA) and Bifidobacterium bifidum (BB)) and mononuclear cells isolated from cord blood.

RESULTS

We show that stimulation with LR induces proinflammatory effects in neonatal monocytes, such as increased expression of surface molecules involved in monocyte activation, increased production of pro-inflammatory and regulatory cytokines and increased production of reactive oxygen species (ROS). Similar effects were observed when monocytes were stimulated simultaneously with LPS. Stimulation with LA and BB alone or in combination also induced cytokine production in monocytes, with BB showing the least effects.

CONCLUSIONS

Our results suggest that probiotics increase the defence functions of neonatal monocytes and thus possibly favourably influence the newborn's ability to fight infections.

IMPACT

Probiotics induce a proinflammatory response in neonatal monocytes in vitro. This is a previously unknown mechanism of how probiotics modulate the immune response of newborns. Probiotic application to neonates may increase their ability to fight off infections.

Anticandidal Activities by Lactobacillus Species: An Update on Mechanisms of Action

Lactobacilli are among the most studied bacteria in the microbiome of the orodigestive and genitourinary tracts. As probiotics, lactobacilli may provide various benefits to the host. These benefits include regulating the composition of the resident microbiota, preventing - or even potentially reverting- a dysbiotic state. Candida albicans is an opportunistic pathogen that can influence and be influenced by other members of the mucosal microbiota and, under immune-compromising conditions, can cause disease. Lactobacillus and Candida species can colonize the same mucosal sites; however, certain Lactobacillus species display antifungal activities that can contribute to low Candida burdens and prevent fungal infection. Lactobacilli can produce metabolites with direct anticandidal function or enhance the host defense mechanisms against fungi. Most of the Lactobacillus spp. anticandidal mechanisms of action remain underexplored. This work aims to comprehensively review and provide an update on the current knowledge regarding these anticandidal mechanisms.

Early life microbial exposures and allergy risks: opportunities for prevention

Allergies, including asthma, food allergy and atopic dermatitis, are increasing in prevalence, particularly in westernized countries. Although a detailed mechanistic explanation for this increase is lacking, recent evidence indicates that, in addition to genetic predisposition, lifestyle changes owing to modernization have an important role. Such changes include increased rates of birth by caesarean delivery, increased early use of antibiotics, a westernized diet and the associated development of obesity, and changes in indoor and outdoor lifestyle and activity patterns. Most of these factors directly and indirectly impact the formation of a diverse microbiota, which includes bacterial, viral and fungal components; the microbiota has a leading role in shaping (early) immune responses. This default programme is markedly disturbed under the influence of environmental and lifestyle risk factors. Here, we review the most important allergy risk factors associated with changes in our exposure to the microbial world and the application of this knowledge to allergy prevention strategies.

Bacterial Quorum Sensing Molecules Promote Allergic Airway Inflammation by Activating the Retinoic Acid Response

IgE and IgG1 production in the type 2 immune response is the characteristic feature of an allergic reaction. However, whether bacterial molecules modulate IgE and IgG1 production remains obscure. Here, we demonstrate that the bacterial quorum sensing molecules acyl homoserine lactones (AHLs) induce IgE and IgG1 production by activating the RARE (retinoic acid response element) response in dendritic cells (DCs) in vivo. DC-specific knockout of the retinoic acid transcriptional factor Rara diminished the AHL-stimulated type 2 immune response in vitro. AHLs altered DC phenotype, upregulated OX40L and IFN-I signature, and promoted T helper 2 cell differentiation in vitro. Finally, AHLs activated the RARE response by inhibiting AKT phosphorylation in vitro, as the AKT agonists IGF-1 and PDGF abolished the effect of AHLs on the RARE response. This study demonstrates a mechanism by which AHLs drive allergic airway inflammation through activating retinoic acid signaling in DCs.

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Acyl homoserine lactones (AHLs) exacerbate allergic airway inflammation

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AHLs induce IgE and IgG1 production

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AHLs activate the RARE response in dendritic cells

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AHLs inhibit AKT phosphorylation

The Role of Prebiotics and Probiotics in Prevention of Allergic Diseases in Infants

Allergic diseases have been linked to genetic and/or environmental factors, such as antibiotic use, westernized high fat and low fiber diet, which lead to early intestinal dysbiosis, and account for the rise in allergy prevalence, especially in western countries. Allergic diseases have shown reduced microbial diversity, including fewer lactobacilli and bifidobacteria, within the neonatal microbiota, before the onset of atopic diseases. Raised interest in microbiota manipulating strategies to restore the microbial balance for atopic disease prevention, through prebiotics, probiotics, or synbiotics supplementation, has been reported. We reviewed and discussed the role of prebiotics and/or probiotics supplementation for allergy prevention in infants. We searched PubMed and the Cochrane Database using keywords relating to "allergy" OR "allergic disorders," "prevention" AND "prebiotics" OR "probiotics" OR "synbiotics." We limited our evaluation to papers of English language including children aged 0-2 years old. Different products or strains used, different period of intervention, duration of supplementation, has hampered the draw of definitive conclusions on the clinical impact of probiotics and/or prebiotics for prevention of allergic diseases in infants, except for atopic dermatitis in infants at high-risk. This preventive effect on eczema in high-risk infants is supported by clear evidence for probiotics but only moderate evidence for prebiotic supplementation. However, the optimal prebiotic or strain of probiotic, dose, duration, and timing of intervention remains uncertain. Particularly, a combined pre- and post-natal intervention appeared of stronger benefit, although the definition of the optimal intervention starting time during gestation, the timing, and duration in the post-natal period, as well as the best target population, are still an unmet need.

The influence of apocynin, lipoic acid and probiotics on antioxidant enzyme levels in the pulmonary tissues of obese asthmatic mice

Bronchial asthma and obesity are common health problems. Obesity is already responsible for 300,000 deaths per year.

AIMS

The aim of the present study was to assess whether apocynin, alpha lipoic acid and probiotic administration in combination with low-fat diet supplementation influences the levels of antioxidant enzymes in the pulmonary tissues of obese asthmatic mice.

MAIN METHODS

The study was performed on male C57/BL6 mice divided into 10 groups: (I) control; (II) asthma; (III) obesity; (IV) asthma + obesity; (V) asthma + obesity + apocynin p.o. 15 mg/kg/day for 12 weeks; (VI) asthma + obesity + low-fat diet for 12 weeks; (VII) asthma + obesity + low-fat diet for 12 weeks with apocynin p.o. 15 mg/kg/day; (VIII) asthma + obesity + low-fat diet with probiotics for 12 weeks; (IX) asthma + obesity + low-fat diet for 12 weeks with lipoic acid p.o. 100 mg/kg/day for 12 weeks; (X) asthma + obesity + standard diet with probiotics for 12 weeks. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) activity were examined. The administration of apocynin alone and apocynin in combination with a low-fat diet resulted in a significant increase in SOD values (respectively p < 0.001; p = 0.010). Application of probiotics resulted in a decrease in CAT activity (p = 0.037) and an increase in GPx activity (p < 0.001) compared to obese asthmatic mice. The administration of lipoic acid resulted in an increase in GR activity (p = 0.024 vs. control).

KEY FINDINGS

Supplementation containing apocynin, lipoic acid and probiotics has a positive influence on the antioxidant capacity of the pulmonary tissues of obese asthmatic mice.

SIGNIFICANCE

These results may contribute to the development of new therapeutic approaches.

Different immune response of dendritic cells of newborns of allergic and healthy mothers to bacterial stimuli

Continuous increasing incidence of allergic diseases is calling for identifying early prognostic markers pointing to increased risk of allergy development and establishing protocols for preventive strategies limiting allergy development in predisposed individuals. It is important to better understand the critical events occurring in early postnatal life, especially the interaction of a newborn with microbial compounds important for the maturation of the neonatal immune system and setting immunoregulatory responses as well. Dendritic cells (DC) together with the cytokine microenvironment play an important role in priming of immune responses. The capacity of monocyte-derived DC (moDC) from cord blood of children of healthy and allergic mothers to respond to microbial antigens (Escherichia coli O86 (EcO86) and delipidated Bacillus firmus (DBF)) was tested by flow cytometry and quantitative real-time PCR. Both EcO86 and DBF were able to promote maturation of moDC, but moDC of children of allergic mothers expressed higher levels of activation markers CD80 and CD83. Increased gene expression of IL-6 and lower expression of indol-amine 2,3 dioxygenase were observed in moDC of neonates of allergic mothers, in comparison to healthy ones. A higher gene expression and an increased presence of activation markers on moDC of newborns of allergic mothers indicate a generally higher reactivity of these cells, possibly enabling easier development of inappropriate immune response after an allergen encounter.

Immunological Tolerance and Function: Associations Between Intestinal Bacteria, Probiotics, Prebiotics, and Phages

Post-birth there is a bacterial assault on all mucosal surfaces. The intestinal microbiome is an important participant in health and disease. The pattern of composition and concentration of the intestinal microbiome varies greatly. Therefore, achieving immunological tolerance in the first 3-4 years of life is critical for maintaining health throughout a lifetime. Probiotic bacteria are organisms that afford beneficial health effects to the host and in certain instances may protect against the development of disease. The potential benefits of modifying the composition of the intestinal microbial cohort for therapeutic benefit is evident in the use in high risks groups such as premature infants, children receiving antibiotics, rotavirus infections in non-vaccinated children and traveler's diarrhea in adults. Probiotics and prebiotics are postulated to have immunomodulating capabilities by influencing the intestinal microbial cohort and dampening the activity of pathobiont intestinal microbes, such as Klebsiella pneumonia and Clostridia perfringens. Lactobacilli and Bifidobacteria are examples of probiotics found in the large intestine and so far, the benefits afforded to probiotics have varied in efficacy. Most likely the efficacy of probiotic bacteria has a multifactorial dependency, namely on a number of factors that include agents used, the dose, the pattern of dosing, and the characteristics of the host and the underlying luminal microbial environment and the activity of bacteriophages. Bacteriophages, are small viruses that infect and lyse intestinal bacteria. As such it can be posited that these viruses display an effective local protective control mechanism for the intestinal barrier against commensal pathobionts that indirectly may assist the host in controlling bacterial concentrations in the gut. A co-operative activity may be envisaged between the intestinal epithelia, mucosal immunity and the activity of bacteriophages to eliminate pathobiots, highlighting the potential role of bacteriophages in assisting with maintaining intestinal homeostasis. Hence bacteriophage local control of inflammation and immune responses may be an additional immunological defense mechanism that exploits bacteriophage-mucin glycoprotein interactions that controls bacterial diversity and abundance in the mucin layers of the gut. Moreover, and importantly the efficacy of probiotics may be dependent on the symbiotic incorporation of prebiotics, and the abundance and diversity of the intestinal microbiome encountered. The virome may be an important factor that determines the efficacy of some probiotic formulations.

The immunomodulatory role of probiotics in allergy therapy

The increased incidence of allergic disorders may be the result of a relative fall in microbial induction in the intestinal immune system during infancy and early childhood. Probiotics have recently been proposed as viable microorganisms for the prevention and treatment of specific allergic diseases. Different mechanisms have been considered for this probiotic property, such as generation of cytokines from activated pro-T-helper type 1 after bacterial contact. However, the effects of its immunomodulatory potential require validation for clinical applications. This review will focus on the currently available data on the benefits of probiotics in allergy disease.

Synbiotic Effects of the Dietary Fiber Long-Chain Inulin and Probiotic Lactobacillus acidophilus W37 Can be Caused by Direct, Synergistic Stimulation of Immune Toll-Like Receptors and Dendritic Cells

SCOPE

Synbiotic effects of dietary fibers and lactobacilli are usually explained by synergistic modulation of gut microbiota. New insight, however, has demonstrated that both dietary fibers and lactobacilli can directly stimulate immune cells and benefit consumer immunity. Here, the synergistic effects of immune active long-chain inulin (lcITF) and Lactobacillus acidophilus W37 (LaW37) on dendritic cells (DCs) are investigated.

METHODS AND RESULTS

Effects of lcITF and LaW37 alone or combined were studied on Toll-like receptor (TLRs) signaling and cytokine secretion by DCs in the presence and absence of media of intestinal epithelial cell (IEC) exposed to the ingredients. Also, the effects of DC responses against Salmonella Typhimurium (STM) were investigated. Synergistic effects were observed on TLR2 and 3. Synergistic effects were not always pro-inflammatory. LaW37 was strongly pro-inflammatory, while cytokine responses were regulatory when combined with lcITF. Exposure of DCs to IECs medium changed the DCs' response, which revealed synergistic enhancing effects of lcITF/LaW37 on production of IL-6 and IL-8. DCs' response in the presence of STM and LaW37 were so strong that lcITF had no additional effect.

CONCLUSION

It is demonstrated that synbiotic effects of dietary fibers and bacteria are not limited to the effects on gut microbiota but can also occur by synergistically directly stimulating IECs and/or immune cells.

Different capacity of in vitro generated myeloid dendritic cells of newborns of healthy and allergic mothers to respond to probiotic strain E. coli O83:K24:H31

Allergic diseases belong to one of the most common diseases with steadily increasing incidence even among young children. There is an urgent need to identify a prognostic marker pointing to increased risk of allergy development enabling early preventive measures introduction. It has been shown that administration of selected probiotic strains or mixtures could prevent allergy development. In our study, we have tested the capacity of probiotic strain Escherichia coli O83:K24:H31 (E. coli O83) to promote dendritic cell (DC) maturation and polarisation of immune responses. Increased presence of activation marker CD83 was observed on DC stimulated by E. coli O83 and DC of newborns of allergic mothers have significantly more increased cell surface presence of CD83 in comparison to children of healthy mothers. Increased gene expression and secretion of IL-10 was detected in DC stimulated with E. coli O83 being higher in DC of newborns of healthy mothers in comparison to allergic ones. Generally, increased presence of intracellular cytokines (IL-4, IL-13, IFN-gamma, IL-17A, IL-22, IL-10) was detected in CD4+ T cells cocultured with DC of children of allergic mothers in comparison to healthy ones. E. coli O83 primed DC significantly increased IL-10 and IL-17A in CD4 T cells of newborns of healthy mothers in comparison to the levels detected in CD4 T cells cocultured with control non-stimulated DC. We can conclude E. coli O83 induces dendritic cell maturation and IL-10 production in DC. Newborns of allergic mothers have generally increased reactivity of both DC and CD4 T cells which together with decreased capacity of DC of newborns of allergic mothers to produce IL-10 could support inappropriate immune responses development after allergen encounter.

In silico analysis of protein toxin and bacteriocins from Lactobacillus paracasei SD1 genome and available online databases

Lactobacillus paracasei SD1 is a potential probiotic strain due to its ability to survive several conditions in human dental cavities. To ascertain its safety for human use, we therefore performed a comprehensive bioinformatics analysis and characterization of the bacterial protein toxins produced by this strain. We report the complete genome of Lactobacillus paracasei SD1 and its comparison to other Lactobacillus genomes. Additionally, we identify and analyze its protein toxins and antimicrobial proteins using reliable online database resources and establish its phylogenetic relationship with other bacterial genomes. Our investigation suggests that this strain is safe for human use and contains several bacteriocins that confer health benefits to the host. An in silico analysis of protein-protein interactions between the target bacteriocins and the microbial proteins gtfB and luxS of Streptococcus mutans was performed and is discussed here.

Probiotics in Asthma and Allergy Prevention

Interest in probiotic research and its potential benefits in infant foods are relatively recent but significantly increasing. The evolution of the knowledge in the last 20 years demonstrated that alterations in the microbiome may be a consequence of events occurring during infancy or childhood, including prematurity, cesarean section, and nosocomial infections. Several pieces of evidence prove that a "healthy" intestinal microbiota facilitates the development of immune tolerance. Interventional studies suggest that probiotics could be protective against the development of many diseases. Nevertheless, many factors complicate the analysis of dysbiosis in subjects with food allergy. Comparison in-between studies are difficult, because of considerable heterogeneity in study design, sample size, age at fecal collection, methods of analysis of gut microbiome, and geographic location. Currently, there is no positive recommendation from scientific societies to use pre- or probiotics for treatment of food allergy or other allergic manifestations, while their use in prevention is being custom-cleared. However, the recommendation is still based on little evidence. Although there is valid scientific evidence in vitro, there is no sufficient information to suggest the use of specific probiotics in allergy and asthma prevention.

Probiotics and Allergic Rhinitis: A Simon Two-Stage Design to Determine Effectiveness

BACKGROUND

Allergic rhinitis (AR) is a chronic upper respiratory disease affecting 10-30% of the population worldwide. It associated with significant economic and medical burden. Probiotics have received attention in recent years as a novel strategy to treat infectious/immune conditions, including AR. However, substantiation of these health claims by regulatory bodies has been rejected due, in part, to inadequate clinical trial design. While randomized controlled trials are considered the gold standard for assessing clinical efficacy, such trials require a priori preclinical data on effect size, which may be a reason for the conflicting results in the probiotic and AR literature. Progressive clinical trial designs, such as the Simon Two-Stage Design, are showing promise within the area of integrative and alternative medicine, particularly in relation to probiotic supplementation, to obtain empirical data for the design of clinical trials that meet regulatory requirements.

METHODS

This Phase II study uses a Simon Two-Stage Design to determine the response rate of patients with AR to a probiotic supplement. Patients will consume a multispecies probiotic twice daily for 8 weeks, and will attend an allergy clinic at the beginning and end of the intervention period for assessment. Symptom improvement following probiotic supplementation will be measured by the mini-Rhinoconjunctivitis Quality of Life Questionnaire. Secondary outcomes include twice-weekly symptom and medication diaries, objective determination of nasal congestion via Nasal Rhinomanometry, and change in frequency of medication usage.

DISCUSSION

This study provides an exemplar of the value of using a progressive study design in the complementary and alternative medicine setting. A Simon Two-Stage Design was adopted to investigate whether a multispecies probiotic supplement, not yet trialed in the context of AR, has promise as a therapeutic intervention and warrants the design of larger placebo-controlled studies.

The role of probiotics in prevention and treatment for patients with allergic rhinitis: A systematic review

BACKGROUND

Allergic rhinitis (AR) is a disease of respiratory allergy, and probiotics can provide a potential strategy for its management. The purpose of this study was to carry out a systematic review to investigate the role of probiotics in the prevention and treatment of AR.

METHODS

We searched for randomized controlled trials (RCTs) of the use of probiotics for the prevention and treatment of AR in the major electronic databases up to March 2014. The quality of the included RCTs was evaluated, and the data were independently extracted by two assessors. Meta-analyses were performed. Continuous data were expressed as the mean difference (MD) or standardized MD with 95% confidence interval (CI). Dichotomous data were expressed as odds ratio with the 95% CI. A p value <0.05 was considered significant.

RESULTS

A total of 11 RCTs were included in the analysis. Probiotic intake was associated with a significant overall improvement of the quality of life scores and nasal symptom scores of patients with AR (MD -2.97 [95% CI, -4.77 to -1.16)]; p = 0.001). No improvements with regard to prevention or immunologic parameters were noted in the patients with AR.

CONCLUSIONS

The current evidence is not sufficiently strong to verify a preventive role of probiotics in AR, but probiotics may improve the overall quality of life and nasal symptom scores. Because the available data were generated from only a few trials with a high degree of heterogeneity, routine use of probiotics for prevention and treatment in patients with AR cannot be recommended.

Induction of regulatory T cells: A role for probiotics and prebiotics to suppress autoimmunity

Regulatory T cells (Tregs) are comprised of a heterogeneous population of cells that play a vital role in suppressing inflammation and maintaining immune tolerance. Given the crucial role of Tregs in maintaining immune homeostasis, it is probably not surprising that many microbial species and their metabolites have the potential to induce Tregs. There is now great interest in the therapeutic potential of probiotics and prebiotics based strategies for a range of autoimmune disorders. This review will summarise recent findings concerning the role of probiotics and prebiotics in induction of Tregs to ameliorate the autoimmune conditions. In addition, the article is focused to explain the different mechanisms of Treg induction and function by these probiotics and prebiotics, based on the available studies till date. The article further proposes that induction of Tregs by probiotics and prebiotics could lead to the development of new therapeutic approach towards curbing the autoimmune response and as an alternative to detrimental immunosuppressive drugs.

Probiotics for allergy prevention

Probiotics, given either as a supplement or in infant foods, have been evaluated in randomised controlled trials for allergy prevention. Here, the aim is to give an overview of the results from these primary prevention studies and to discuss current strategies. In most studies, single strains or a mixture of strains of lactic acid bacteria and bifidobacteria have been used--prenatally, postnatally or perinatally. Several meta-analyses have reported a moderate benefit of probiotics for eczema prevention, and the most consistent effect has been observed with a combined perinatal intervention in infants at high risk of allergic disease due to familial predisposition. In a recent meta-analysis, the use of multi-strain probiotics appeared to be most effective for eczema prevention. No preventive effect has been shown for other allergic manifestations. As long-term follow-up data on later onset allergic conditions (asthma and allergic rhinitis) are available only from a few of the initiated studies, reports from ongoing follow-up studies that are adequately powered to examine long-term outcomes are anticipated to provide more insight. Arguably, the differences in many aspects of study design and the use of different probiotic strains and combinations have made direct comparison difficult. To date, expert bodies do not generally recommend probiotics for allergy prevention, although the World Allergy Organization (WAO) in their recently developed guidelines suggests considering using probiotics in pregnant women, during breastfeeding and/or to the infant if at high risk of developing allergic disease (based on heredity). However, in concordance with other expert bodies, the WAO guideline panel stressed the low level of evidence and the need for adequately powered randomised controlled trials and a more standardised approach before clinical recommendations on specific strains, dosages and timing can be given.

Probiotic supplementation influences faecal short chain fatty acids in infants at high risk for eczema

The composition of the gut microbiota plays a role in the development of allergies. Based on the immunomodulating capacities of bacteria, various studies have investigated the potential role for probiotics in the prevention of childhood eczema. In a previous study we have shown that significantly less children developed eczema after probiotic supplementation (Bifidobacterium bifidum W23, Bifidobacterium animalis subsp. lactis W52 and Lactococcus lactis W58, Ecologic®Panda) at three months of age as compared to controls. Here, metabolites in faecal samples of these 3-month old children were measured by 1H-nuclear magnetic resonance to investigate possible gut metabolic alterations. Lower amounts of short-chain fatty acids (SCFAs), succinate, phenylalanine and alanine were found in faecal samples of children later developing eczema, whereas the amounts of glucose, galactose, lactate and lactose were higher compared to the children not developing eczema. Although these differences were already present at the age of 3 months, eczema did not develop in the majority of children before the age of 1 year. Supplementation of multispecies probiotics seems to induce higher levels of lactate and SCFAs, and lower levels of lactose and succinate when compared with the placebo group. This might explain the temporary preventive effect of probiotics on the development of eczema. These results highlight the role bacterial metabolites may play in development of the immune system, even before clinical manifestations of allergic disease arise.

Effects of Fructans from Mexican Agave in Newborns Fed with Infant Formula: A Randomized Controlled Trial

BACKGROUND

The importance of prebiotics consumption is increasing all over the world due to their beneficial effects on health. Production of better prebiotics from endemic plants raises possibilities to enhance nutritional effects in vulnerable population groups. Fructans derived from Agave Plant have demonstrated their safety and efficacy as prebiotics in animal models. Recently, the safety in humans of two fructans obtained from Agave tequilana (Metlin(®) and Metlos(®)) was demonstrated.

METHODS

This study aimed to demonstrate the efficacy as prebiotics of Metlin(®) and Metlos(®) in newborns of a randomized, double blind, controlled trial with a pilot study design. Biological samples were taken at 20 ± 7 days, and three months of age from healthy babies. Outcomes of efficacy include impact on immune response, serum ferritin, C-reactive protein, bone metabolism, and gut bacteria changes.

RESULTS

There were differences statistically significant for the groups of infants fed only with infant formula and with formula enriched with Metlin(®) and Metlos(®).

CONCLUSIONS

Our results support the efficacy of Metlin(®) and Metlos(®) as prebiotics in humans, and stand the bases to recommend their consumption.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT 01251783.

Randomised double-blind placebo-controlled study of the effect of Lactobacillus paracasei NCC 2461 on skin reactivity

In recent decades, the prevalence of subjects with reactive skin has considerably increased in industrialised countries. 50% of women and 30% of men report cutaneous discomfort classified under reactive/sensitive skin. Several topical approaches have been proposed, in particular through improvement of galenic forms or protection of epidermal surface. We propose to act differently, deeply from inside the body via an innovative nutritional approach. To this purpose, Lactobacillus paracasei NCC 2461 (ST11) was selected because of its specific beneficial skin properties discovered in in vitro studies, i.e. diminution of neurogenic inflammation and promotion of the recovery of skin barrier function. We designed a randomised double-blind placebo-controlled clinical study with a two-month supplementation in two female treatment groups (n=32 per group). A capsaicin test was performed to monitor the time course of skin sensitivity. Moreover, transepidermal water loss was assessed to analyse the rate of skin barrier function recovery; dryness of the leg and roughness of the cheeks was investigated by a dermatologist as well as by self-assessment. The results of the present clinical trial show that oral supplementation with the probiotic decreases skin sensitivity and increases the rate of barrier function recovery. Thus, the data provide evidence that daily intake of ST11 could improve reactive skin condition.

Maternal short-chain fructooligosaccharide supplementation influences intestinal immune system maturation in piglets

Peripartum nutrition is crucial for developing the immune system of neonates. We hypothesized that maternal short-chain fructooligosaccharide (scFOS) supplementation could accelerate the development of intestinal immunity in offspring. Thirty-four sows received a standard or a scFOS supplemented diet (10 g scFOS/d) for the last 4 weeks of gestation and the 4 weeks of lactation. Colostrum and milk immunoglobulins (Ig) and TGFβ1 concentrations were evaluated on the day of delivery and at d 6 and d 21 postpartum. Piglet intestinal structure, the immunologic features of jejunal and ileal Peyer's patches, and mesenteric lymph node cells were analysed at postnatal d 21. Short-chain fatty acid concentrations were measured over time in the intestinal contents of suckling and weaned piglets. Colostral IgA (P<0.05) significantly increased because of scFOS and TGFβ1 concentrations tended to improve (P<0.1). IFNγ secretion by stimulated Peyer's patch and mesenteric lymph node cells, and secretory IgA production by unstimulated Peyer's patch cells were increased (P<0.05) in postnatal d 21 scFOS piglets. These differences were associated with a higher proportion of activated CD25+CD4α+ T cells among the CD4+ helper T lymphocytes (P<0.05) as assessed by flow cytometry. IFNγ secretion was positively correlated with the population of activated T lymphocytes (P<0.05). Total short-chain fatty acids were unchanged between groups during lactation but were higher in caecal contents of d 90 scFOS piglets (P<0.05); specifically propionate, butyrate and valerate. In conclusion, we demonstrated that maternal scFOS supplementation modified the intestinal immune functions in piglets in association with increased colostral immunity. Such results underline the key role of maternal nutrition in supporting the postnatal development of mucosal immunity.

Preventative and therapeutic probiotic use in allergic skin conditions: experimental and clinical findings

Probiotics are ingested live microbes that can modify intestinal microbial populations in a way that benefits the host. The interest in probiotic preventative/therapeutic potential in allergic diseases stemmed from the fact that probiotics have been shown to improve intestinal dysbiosis and permeability and to reduce inflammatory cytokines in human and murine experimental models. Enhanced presence of probiotic bacteria in the intestinal microbiota is found to correlate with protection against allergy. Therefore, many studies have been recently designed to examine the efficacy of probiotics, but the literature on the allergic skin disorders is still very scarce. Here, our objective is to summarize and evaluate the available knowledge from randomized or nonrandomized controlled trials of probiotic use in allergic skin conditions. Clinical improvement especially in IgE-sensitized eczema and experimental models such as atopic dermatitis-like lesions (trinitrochlorobenzene and picryl chloride sensitizations) and allergic contact dermatitis (dinitrofluorobenzene sensitization) has been reported. Although there is a very promising evidence to recommend the addition of probiotics into foods, probiotics do not have a proven role in the prevention or the therapy of allergic skin disorders. Thus, being aware of possible measures, such as probiotics use, to prevent/heal atopic diseases is essential for the practicing allergy specialist.

Transcriptional response of HT-29 intestinal epithelial cells to human and bovine milk oligosaccharides

Human milk oligosaccharides (HMO) have been shown to interact directly with immune cells. However, large quantities of HMO are required for intervention or clinical studies, but these are unavailable in most cases. In this respect, bovine milk is potentially an excellent source of commercially viable analogues of these unique molecules. In the present study, we compared the transcriptional response of colonic epithelial cells (HT-29) to the entire pool of HMO and bovine colostrum oligosaccharides (BCO) to determine whether the oligosaccharides from bovine milk had effects on gene expression that were similar to those of their human counterparts. Gene set enrichment analysis of the transcriptional data revealed that there were a number of similar biological processes that may be influenced by both treatments including a response to stimulus, signalling, locomotion, and multicellular, developmental and immune system processes. For a more detailed insight into the effects of milk oligosaccharides, the effect on the expression of immune system-associated glycogenes was chosen as a case study when performing validation studies. Glycogenes in the current context are genes that are directly or indirectly regulated in the presence of glycans and/or glycoconjugates. RT-PCR analysis revealed that HMO and BCO influenced the expression of cytokines (IL-1β, IL-8, colony-stimulating factor 2 (granulocyte–macrophage) (GM-CSF2), IL-17C and platelet factor 4 (PF4)), chemokines (chemokine (C–X–C motif) ligand 1 (CXCL1), chemokine (C–X–C motif) ligand 3 (CXCL3), chemokine (C–C motif) ligand 20 (CCL20), chemokine (C–X–C motif) ligand 2 (CXCL2), chemokine (C–X–C motif) ligand 6 (CXCL6), chemokine (C–C motif) ligand 5 (CCL5), chemokine (C–X3–C motif) ligand 1 (CX3CL1) and CXCL2) and cell surface receptors (interferon γ receptor 1 (IFNGR1), intercellular adhesion molecule-1 (ICAM-1), intercellular adhesion molecule-2 (ICAM-2) and IL-10 receptor α (IL10RA)). The present study suggests that milk oligosaccharides contribute to the development and maturation of the intestinal immune response and that bovine milk may be an attractive commercially viable source of oligosaccharides for such applications.

Can experimental pharmacology be always applied to human nutrition?

Randomized clinical trials are the gold standard of pharmacology and are the only way to provide solid and evidence-based data. However, they are difficult to apply to nutrition-based settings. This article outlines the major differences between pharmacology and nutrition research and indicates some potential pathways to follow during claim building.

Effect of probiotics on allergic rhinitis in Df, Dp or dust-sensitive children: a randomized double blind controlled trial

OBJECTIVE

To study, we examined the effect of Lactobacillus salivarius on the clinical symptoms and medication use among children with established allergic rhinitis (AR).

DESIGN

Double blind, randomized, controlled trial.

SETTING

Hualien Tzu-Chi General Hospital.

METHODS

Atopic children with current allergic rhinitis received 4x10(9) colony forming units/g of Lactobacillus salivarius (n=99) or placebo (n=100) daily as a powder mixed with food or water for 12 weeks. The SCORing Allergic rhinitis index (specific symptoms scores [SSS] and symptom medication scores [SMS]), which measures the extent and severity of AR, was assessed in each subject at each of the visits--2 weeks prior to treatment initiation (visit 0), at the beginning of the treatment (visit 1), then at 4 (visit 2), 8 (visit 3) and 12 weeks (visit 4) after starting treatment. The WBC, RBC, platelet and, eosinophil counts as well as the IgE antibody levels of the individuals were evaluated before and after 3 months of treatment.

RESULTS

The major outcome, indicating the efficacy of Lactobacillus salivarius treatment, was the reduction in rhinitis symptoms and drug scores. No significant statistical differences were found between baseline or 12 weeks in the probiotic and placebo groups for any immunological or blood cell variables.

CONCLUSIONS

Our study demonstrates that Lactobacillus salivarius treatment reduces rhinitis symptoms and drug usage in children with allergic rhinitis.

Probiotic modulation of dendritic cells co-cultured with intestinal epithelial cells

AIM: To investigate cytokine production and cell surface phenotypes of dendritic cells (DC) in the presence of epithelial cells stimulated by probiotics.

METHODS: Mouse DC were cultured alone or together with mouse epithelial cell monolayers in normal or inverted systems and were stimulated with heat-killed probiotic bacteria, Bifidobacterium lactis AD011 (BL), Bifidobacterium bifidum BGN4 (BB), Lactobacillus casei IBS041 (LC), and Lactobacillus acidophilus AD031 (LA), for 12 h. Cytokine levels in the culture supernatants were determined by enzyme-linked immunosorbent assay and phenotypic analysis of DC was investigated by flow cytometry.

RESULTS: BB and LC in single-cultured DC increased the expression of I-Ad, CD86 and CD40 (I-Ad, 18.51 vs 30.88, 46.11; CD86, 62.74 vs 92.7, 104.12; CD40, 0.67 vs 6.39, 3.37, P < 0.05). All of the experimental probiotics increased the production of inflammatory cytokines, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. However, in the normal co-culture systems, LC and LA decreased the expression of I-A^d (39.46 vs 30.32, 33.26, P < 0.05), and none of the experimental probiotics increased the levels of IL-6 or TNF-α. In the inverted co-culture systems, LC decreased the expression of CD40 (1.36 vs -2.27, P < 0.05), and all of the experimental probiotics decreased the levels of IL-6. In addition, BL increased the production of IL-10 (103.8 vs 166.0, P < 0.05) and LC and LA increased transforming growth factor-β secretion (235.9 vs 618.9, 607.6, P < 0.05).

CONCLUSION: These results suggest that specific probiotic strains exert differential immune modulation mediated by the interaction of dendritic cells and epithelial cells in the homeostasis of gastrointestinal tract.

Identification of Immunopotentiating Lactic Acid Bacteria that Induce Antibody Production by in vitro Stimulated Human Peripheral Blood Mononuclear Cells

L-leucyl-L-leucine methyl ester (LLME) is known to remove lysosome-rich cells from human peripheral blood mononuclear cells (PBMCs). To evaluate the immunopotentiating ability of lactic acid bacteria (LAB), we adopted the in vitro stimulation protocol of LLME-treated PBMCs as a model assay system and monitored the level of antibody produced by stimulated PBMCs. The results indicated that several LAB strains have immunopotentiating ability against PBMCs, as evidenced by the enhanced antibody production and increased number of antigen-specific B cells. Next, we identified T cells as the direct target cells of the immunopotentiating LAB strain L32, suggesting that L32 induced antibody production by PBMCs through T-cell activation. Finally, we tested the immunopotentiating ability of ligands for Toll-like receptor 2 (TLR2), which is known to mediate the LAB signal, and observed that both L32 and one of the TLR2 ligands, LTA-BS, induced antigen-specific antibody production by in vitro stimulated PBMC. This suggests that L32 and LTA-BS can be used as an adjuvant for stimulating immune reaction in PBMCs.

Late rather than early responses of human dendritic cells highlight selective induction of cytokines, chemokines and growth factors by probiotic bacteria

The probiotic properties of commensal bacteria including lactobacilli and bifidobacteria are likely to be determined at least in part by their effects on dendritic cells. Like traditional immune stimulants such as lipopolysaccharides (LPS), probiotic bacteria promote maturation of cultured human dendritic cells (DC) by inducing elevated expression of MHC-II and co-stimulatory molecules. Different effects have been reported on cytokine induction, especially of major regulatory cytokines such as TNF-α, IL-12 and IL-10. Yet, these previous analyses have failed to reveal consistent differences between such effects of probiotics on the one hand, and of LPS on the other. Selective response markers for probiotics, however, would be important for our understanding of their biological properties and for a rational selection of strains for in vivo studies. In this study, we compared in detail both early and late effects on cultured human DC of 4 different probiotics with those of LPS. At the early stages of stimulation, all stimuli induced qualitatively very similar responses in DC at the level of surface markers and secretion of cytokines and chemokines. A lower immune stimulatory effect was observed by Bifidobacterium animalis BB-12 as compared to lactobacilli. Late responses, on the other hand, tended to diverge. Microarray transcript profiling for 268 cytokines, chemokines, growth factors and their receptors after 2 days of culture revealed various transcripts to be selectively induced by certain probiotics but not LPS. Our data indicate that late rather than early DC responses may be helpful to clarify the divergent biological effects of probiotics on human innate immune responses.

Emerging molecular insights into the interaction between probiotics and the host intestinal mucosa

Probiotic bacteria can modulate immune responses in the host gastrointestinal tract to promote health. The genomics era has provided novel opportunities for the discovery and characterization of bacterial probiotic effector molecules that elicit specific responses in the intestinal system. Furthermore, nutrigenomic analyses of the response to probiotics have unravelled the signalling and immune response pathways which are modulated by probiotic bacteria. Together, these genomic approaches and nutrigenomic analyses have identified several bacterial factors that are involved in modulation of the immune system and the mucosal barrier, and have revealed that a molecular 'bandwidth of human health' could represent a key determinant in an individual's physiological responsiveness to probiotics. These approaches may lead to improved stratification of consumers and to subpopulation-level probiotic supplementation to maintain or improve health, or to reduce the risk of disease.

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.

Dose-dependent immunomodulation of human dendritic cells by the probiotic Lactobacillus rhamnosus Lcr35

The response of the immune system to probiotics remains controversial. Some strains modulate the cytokine production of dendritic cells (DCs) in vitro and induce a regulatory response, while others induce conversely a pro-inflammatory response. These strain-dependent effects are thought to be linked to specific interactions between bacteria and pattern recognition receptors. We investigated the effects of a well characterized probiotic strain, Lactobacillus rhamnosus Lcr35, on human monocyte-derived immature DCs, using a wide range of bacterial concentrations (multiplicity of infection, MOI, from 0.01 to 100). DNA microarray and qRT-PCR analysis showed that the probiotic induced a large-scale change in gene expression (nearly 1,700 modulated genes, with 3-fold changes), but only with high doses (MOI, 100). The upregulated genes were mainly involved in immune response and identified a molecular signature of inflammation according to the model of Torri. Flow cytometry analysis also revealed a dose-dependent maturation of the DC membrane phenotype, until DCs reached a semi-mature state, with an upregulation of the membrane expression of CD86, CD83, HLA-DR and TLR4, associated with a down-regulation of DC-SIGN, MR and CD14. Measurement of the DC-secreted cytokines showed that Lcr35 induced a strong dose-dependent increase of the pro-Th1/Th17 cytokine levels (TNFα, IL-1β, IL-12p70, IL-12p40 and IL-23), but only a low increase in IL-10 concentration. The probiotic L. rhamnosus Lcr35 therefore induce a dose-dependent immunomodulation of human DCs leading, at high doses, to the semi-maturation of the cells and to a strong pro-inflammatory effect. These results contribute to a fuller understanding of the mechanism of action of this probiotic, and thus of its potential clinical indications in the treatment of either infectious or IgE-dependent allergic diseases.

Probiotic modulation of dendritic cells and T cell responses in the intestine

Over the past decade it has become clear that probiotic and commensal interactions with mucosal dendritic cells in the lamina propria or epithelial cells lining the mucosa can modulate specific functions of the mucosal immune system. Innate pattern-recognition receptors such as TLRs, NLRs and CLRs play a crucial role in the host recognition of probiotics and other microorganism. Signalling via these receptors directly influences the chemokine and cytokine response of dendritic cells as well as the crosstalk between the epithelium and the immune cells in the lamina propria. This can influence the population of effector and regulatory T cell subsets in the mucosa. Immune assays with probiotics have shown that the in vitro immune response is both species and strain-specific. Such assays may be useful for the selection of probiotic strains that have beneficial effects on the regulation of intestinal inflammation but more comparative studies are needed to confirm recent findings. A better understanding of the molecular mechanisms of probiotics, the effect of dose, and frequency of administration on microbial sampling by mucosal APC will also help to clarify the value of immune assays as selection criteria for probiotics.

Well-controlled proinflammatory cytokine responses of Peyer's patch cells to probiotic Lactobacillus casei

SUMMARY

In order to clarify the probiotic features of immunomodulation, cytokine production by murine spleen and Peyer's patch (PP) cells was examined in response to probiotic and pathogenic bacteria. In spleen cells, probiotic Lactobacillus casei induced interleukin (IL)-12 production by CD11b(+) cells more strongly than pathogenic Gram-positive and Gram-negative bacteria and effectively promoted the development of T helper (Th) type 1 cells followed by high levels of secretion of interferon (IFN)-gamma. Although the levels of IL-12 secreted by PP cells in response to L. casei were lower in comparison with spleen cells, Th1 cells developed as a result of this low-level induction of IL-12. However, IFN-gamma secretion by the L. casei-induced Th1 cells stimulated with a specific antigen was down-regulated in PP cells. Development of IL-17-producing Th17 cells was efficiently induced in PP cells by antigen stimulation. Lactobacillus casei slightly, but significantly, inhibited the antigen-induced secretion of IL-17 without a decrease in the proportion of Th17 cells. No bacteria tested induced the development of IL-10-producing, transforming growth factor-beta-producing or Foxp3-expressing regulatory T cells, thus suggesting that certain probiotics might regulate proinflammatory responses through as yet unidentified mechanisms in PP cells. These data show probiotic L. casei to have considerable potential to induce IL-12 production and promote Th1 cell development, but the secretion of proinflammatory cytokines such as IL-12 and IL-17 may be well controlled in PP cells.

Identification of genetic loci in Lactobacillus plantarum that modulate the immune response of dendritic cells using comparative genome hybridization

Background

Probiotics can be used to stimulate or regulate epithelial and immune cells of the intestinal mucosa and generate beneficial mucosal immunomodulatory effects. Beneficial effects of specific strains of probiotics have been established in the treatment and prevention of various intestinal disorders, including allergic diseases and diarrhea. However, the precise molecular mechanisms and the strain-dependent factors involved are poorly understood.

Methodology/Principal Findings

In this study, we aimed to identify gene loci in the model probiotic organism Lactobacillus plantarum WCFS1 that modulate the immune response of host dendritic cells. The amounts of IL-10 and IL-12 secreted by dendritic cells (DCs) after stimulation with 42 individual L. plantarum strains were measured and correlated with the strain-specific genomic composition using comparative genome hybridisation and the Random Forest algorithm. This in silico “gene-trait matching” approach led to the identification of eight candidate genes in the L. plantarum genome that might modulate the DC cytokine response to L. plantarum. Six of these genes were involved in bacteriocin production or secretion, one encoded a bile salt hydrolase and one encoded a transcription regulator of which the exact function is unknown. Subsequently, gene deletions mutants were constructed in L. plantarum WCFS1 and compared to the wild-type strain in DC stimulation assays. All three bacteriocin mutants as well as the transcription regulator (lp_2991) had the predicted effect on cytokine production confirming their immunomodulatory effect on the DC response to L. plantarum. Transcriptome analysis and qPCR data showed that transcript level of gtcA3, which is predicted to be involved in glycosylation of cell wall teichoic acids, was substantially increased in the lp_2991 deletion mutant (44 and 29 fold respectively).

Conclusion

Comparative genome hybridization led to the identification of gene loci in L. plantarum WCFS1 that modulate the immune response of DCs.

Various effects of different probiotic strains in allergic disorders: an update from laboratory and clinical data

Epidemiological data show that allergic children have a different intestinal flora from healthy children with higher levels of Clostridia and lower levels of Bifidobacteria. Nonetheless, Bifidobacteria and Lactobacilli are found more commonly in the composition of the intestinal flora of non-allergic children. Probiotics are ingested live microbes that can modify intestinal microbial populations in a way that benefits the host and they are represented mainly by Lactobacilli. Enhanced presence of probiotic bacteria in the intestinal microbiota is found to correlate with protection against atopy. There is also very promising evidence to recommend the addition of probiotics to foods for the prevention and treatment of allergic diseases. Clinical improvement, especially in allergic rhinitis and immunoglobulin (Ig)E-sensitized (atopic) eczema, has been reported in most of the published studies. However, clinical benefit of probiotic therapy depends upon numerous factors, such as type of bacterium, dosing regimen, delivery method and other underlying host factors, e.g. the age and diet of the host. Selection of the most beneficial probiotic strain, the dose and the timing of supplementation still need to be determined. This review helps understanding of the role of probiotics in various allergic diseases, explaining laboratory and clinical data in light of recent literature.

Host interactions of probiotic bacterial surface molecules: comparison with commensals and pathogens

How can probiotic bacteria transduce their health benefits to the host? Bacterial cell surface macromolecules are key factors in this beneficial microorganism-host crosstalk, as they can interact with host pattern recognition receptors (PRRs) of the gastrointestinal mucosa. In this Review, we highlight the documented signalling interactions of the surface molecules of probiotic bacteria (such as long surface appendages, polysaccharides and lipoteichoic acids) with PRRs. Research on host-probiotic interactions can benefit from well-documented host-microorganism studies that span the spectrum from pathogenicity to mutualism. Distinctions and parallels are therefore drawn with the interactions of similar molecules that are presented by gastrointestinal commensals and pathogens.

Neonatal mucosal immunization with a non-living, non-genetically modified Lactococcus lactis vaccine carrier induces systemic and local Th1-type immunity and protects against lethal bacterial infection

Safe and effective immunization of newborns and infants can significantly reduce childhood mortality, yet conventional vaccines have been largely unsuccessful in stimulating the neonatal immune system. We explored the capacity of a novel mucosal antigen delivery system consisting of non-living, non-genetically modified Lactococcus lactis particles, designated as Gram-positive enhancer matrix (GEM), to induce immune responses in the neonatal setting. Yersinia pestis LcrV, used as model protective antigen, was displayed on the GEM particles. Newborn mice immunized intranasally with GEM-LcrV developed LcrV-specific antibodies, Th1-type cell-mediated immunity, and were protected against lethal Y. pestis (plague) infection. The GEM particles activated and enhanced the maturation of neonatal dendritic cells (DCs) both in vivo and in vitro. These DCs showed increased capacities for secretion of proinflammatory and Th1-cell polarizing cytokines, antigen presentation and stimulation of CD4(+) and CD8(+) T cells. These data show that mucosal immunization with L. lactis GEM particles carrying vaccine antigens represents a promising approach to prevent infectious diseases early in life.

Lactic acid bacteria as adjuvants for sublingual allergy vaccines

We compared immunomodulatory properties of 11 strains of lactic acid bacteria as well as their capacity to enhance sublingual immunotherapy efficacy in a murine asthma model. Two types of bacterial strains were identified, including: (i) potent inducers of IL-12p70 and IL-10 in dendritic cells, supporting IFN-gamma and IL-10 production in CD4+ T cells such as Lactobacillus helveticus; (ii) pure Th1 inducers such as L. casei. Sublingual administration in ovalbumin-sensitized mice of L. helveticus, but not L. casei, reduced airways hyperresponsiveness, bronchial inflammation and proliferation of specific T cells in cervical lymph nodes. Thus, probiotics acting as a Th1/possibly Treg, but not Th1 adjuvant, potentiate tolerance induction via the sublingual route.