Probiotics: Potent Immunomodulatory Tool Against Allergy

Probiotics are defined as live microbial food ingredients that produce several beneficial effects to human health. Probiotic bacteria have been mostly investigated in the prevention of and treatment for different gastrointestinal diseases and allergies. It is not fully clear how probiotics exert their beneficial effects on health, but one of the most probable mechanisms of action is the modulation of immune responses via the mucosal immune system of the gut. Commensal bacteria in the gastrointestinal tract play an integral role in both innate and humoral immunity. It is well established that this protective role can be maintained or modulated by the ingestion of probiotics. More recently, it has been shown that specific probiotic strains can influence the secretion of cytokines to help direct naïve T-helper cells toward either a Th1-dominant, cell-mediated immune response or toward a Th2-dominant, humoral immune response. This paper will review current knowledge of the Th1/Th2 model of humoral immunity as well as introduce how strain-specific probiotics can be used therapeutically to help balance this immune response and therefore help prevent allergy.     

Towards understanding molecular modes of probiotic action

The possibility that certain microorganisms might be beneficial to human health is highlighted by the numerous consumer products containing probiotic bacteria. Probiotics are typically administered in food that, following entry into the gastro-intestinal tract, results in measurable health-promoting effects. Although there is a growing list of health benefits provided by the consumption of probiotics, their precise mechanisms of action remain largely unknown. Recent molecular- and genomics-based studies are starting to provide insight into the ways probiotic bacteria sense and adapt to the gastro-intestinal tract environment. Complementary approaches using host cell in vitro systems together with animal models and human volunteers are revealing specific intestinal cell responses to probiotics. These studies should ultimately disclose the molecular mechanisms and pinpoint the bacterial and host effector molecules and pathways by which probiotics are able to modulate human health.     

Microbes versus microbes: immune signals generated by probiotic lactobacilli and their role in protection against microbial pathogens

Probiotic lactic acid bacteria can signal the immune system through innate cell surface pattern recognition receptors or via direct lymphoid cell activation. In some cases, this action has been shown to be sufficient to modulate local- and systemic-level in vivo immune responses. Practical applications of probiotics include their use in anti-tumour and anti-allergy immunotherapy, but there is also increasing evidence that some probiotics can stimulate a protective immune response sufficiently to enhance resistance to microbial pathogens. This review outlines the experimental and clinical evidence for enhanced anti-microbial immune protection by probiotic lactic acid bacteria, focussing on those studies where a correlative or suggestive link has been shown between immune modulation and enhanced protection.     

Bacterial biota of shrimp intestine is significantly modified by the use of a probiotic mixture: a high throughput sequencing approach

The use of probiotics is a common practice of current shrimp aquaculture. Despite the immunophysiological responses that have been measured in shrimp exposed to probiotics, no information is currently available on the effect of this practice on the intestinal microbiota. The objective of this work was to evaluate the effect of a probiotic mixture on the intestinal microbiota of shrimp cultured under farm conditions. A culture-independent method based on high-throughput-sequencing (16S rRNA) was used to examine intestinal bacterial communities. A traditional system (without probiotics) was used as the reference. Targeted metagenomics analysis revealed that the probiotic mixture was based on bacteria in the phyla Proteobacteria and Firmicutes. A total of 23 species of bacteria were detected in the probiotic mixture; of these, 11 were detected in the intestine of shrimp reared in both systems, and 12 were novel for the system. Eight of the novel species were detected in shrimp cultured with the probiotic mixture; however, none of these novel species were related to marine or inclusively aquacultural environments, and only one (Bacillus subtilis) was recognized as probiotic for shrimp. The use of the probiotic mixture modified the bacterial profile of the shrimp intestine; however, most of the bacteria incorporated into the intestine were nonindigenous to the marine environment with no previous evidence of probiotic effects on any marine organism. The use of this probiotic mixture may represent a risk of causing environmental imbalances, particularly because farms using these types of probiotic mixtures discharge their effluents directly into the ocean without prior treatment.     

Probiotic and other functional microbes: from markets to mechanisms

Insight into the diversity and function of the human intestinal microbiota has been stimulated by clinical studies with bacteria that exhibit specific functions and which are marketed as probiotics to positively affect our health. Initial efforts concentrated on establishing sound scientific support for the efficacy of these probiotic bacteria, which mainly include Lactobacillus and Bifidobacterium species. Following these evidence-based functional approaches, considerable research is now focused on the mechanisms of action of probiotic bacteria. The mechanisms identified to date mainly relate to the stimulation of host defence systems, immune modulation and the competitive exclusion of pathogens. Recent efficacy, molecular and genomics-based studies have also been reported for some probiotic strains that have found their position in the market place.     

The implication of probiotics in the prevention of dental caries

The current oral health crisis, whose causes are varied and complex, necessitates timely oral evaluation and early detection and treatment of oral health problems. Dramatic changes in eating habits and lifestyles are associated with the recent decline in oral health. Probiotics are “good” bacteria that support digestion and a healthy immune system and offer various health benefits to the host. Traditionally, probiotics have been used to improve gut health; the most common uses have historically been as a treatment or prevention of gastrointestinal infections and disease. During the last decade, studies have additionally suggested the intake of probiotics for oral health purposes. Probiotic use provides an effective strategy to combat oral disease, including the development of dental caries and periodontal infection. The aim of this review is to describe the beneficial roles of probiotic bacteria in the oral cavity and the potential mechanisms by which these bacteria exert their effects on oral health.

     

The immunomodulatory properties of probiotic microorganisms beyond their viability (ghost probiotics: proposal of paraprobiotic concept)

The probiotic approach represents a potentially effective and mild alternative strategy for the prevention and treatment of either inflammatory or allergic diseases. Several studies have shown that different bacterial strains can exert their probiotic abilities by influencing the host's immune system, thereby modulating immune responses. However, the emerging concern regarding safety problems arising from the extensive use of live microbial cells is enhancing the interest in non-viable microorganisms or microbial cell extracts, as they could eliminate shelf-life problems and reduce the risks of microbial translocation and infection. The purpose of this review is to provide an overview of the scientific literature concerning studies in which dead microbial cells or crude microbial cell fractions have been used as health-promoting agents. Particular attention will be given to the modulation of host immune responses. Possible mechanisms determining the effect on the immune system will also be discussed. Finally, in the light of the FAO/WHO definition of probiotics, indicating that the word 'probiotic' should be restricted to products that contain live microorganisms, and considering the scientific evidence indicating that inactivated microbes can positively affect human health, we propose the new term 'paraprobiotic' to indicate the use of inactivated microbial cells or cell fractions to confer a health benefit to the consumer.     

生物被膜：益生菌肠道定植的新策略

益生菌可改善机体微生态平衡,在促进营养吸收、控制肠道感染和调节免疫功能等方面具有特殊的功效,但存在胃肠道环境难定植、口服生物利用度低等问题。生物被膜是多个细菌黏附于非生物或生物表面,分泌胞外聚合物(extracellular polymeric substances),并将自身包裹其中形成的一种有组织的细菌集团,包含胞外多糖(exopolysaccharides,EPS)、蛋白质、胞外DNA(extracellular deoxyribonucleic acid, eDNA)和脂质等多种组成成分,是一个具有三维立体空间结构的聚集体。被膜状态的益生菌较浮游菌在抗逆性、对抗病原菌和调节免疫功能等方面具有明显优势,这些特点为新型益生菌的开发提供了新的研究思路。本文阐述了被膜状态益生菌的优势,重点介绍了促进益生菌生物被膜形成的活性物及其形成机制,简述了益生菌生物被膜的安全性问题。当前,益生菌生物被膜的研究尚处于起步阶段,希望本文能为该领域未来的研究提供参考。     

Recovery of Viable Bacteria from Probiotic Products that Target Oral Health

Probiotic therapy has predominantly been directed toward promoting and maintaining intestinal health. In recent years, however, probiotic regimens that target oral health have appeared on the market. These regimens are often delivered in the form of lozenges. Despite the oral health claims made by the manufacturers of these products, there is little independent evidence in the literature to support such claims. In theory, probiotic organisms can be beneficial by several different means including direct inhibition of pathogens and boosting of the host immune response, with the underlying assumption that these mechanisms require a critical number of viable organisms. In this study, five brands of probiotics marketed for oral health were tested for the recovery of viable bacteria. For only one brand could viable bacteria be recovered within one log of the manufacturer’s stated starting amount of bacteria. Nearly, a billion viable bacteria could be recovered from a lozenge of this brand. The other brands claimed similar starting amounts of bacteria at the time of manufacture but at least a three-log drop-off was observed in the amount of viable bacteria recovered from those products. Refrigeration of the probiotics significantly improved the recovery for one brand, but recoveries for all but one brand remained below the recommended daily dosage for probiotic regimens. It is concluded that probiotic brands differ significantly in the quantities of bacteria that remain viable with most failing to meet recommended dosage targets.     

Distinctive probiotic features share common TLR2‐dependent signalling in intestinal epithelial cells

The underlying mechanisms of probiotics and postbiotics are not well understood, but it is known that both affect the adaptive and innate immune responses. In addition, there is a growing concept that some probiotic strains have common core mechanisms that provide certain health benefits. Here, we aimed to elucidate the signalization of the probiotic bacterial strains Lactobacillus paragasseri K7, Limosilactobacillus fermentum L930BB, Bifidobacterium animalis subsp. animalis IM386 and Lactiplantibacillus plantarum WCFS1. We showed in in vitro experiments that the tested probiotics exhibit common TLR2‐ and TLR10‐dependent downstream signalling cascades involving inhibition of NF‐κB signal transduction. Under inflammatory conditions, the probiotics activated phosphatidylinositol 3‐kinase (PI3K)/Akt anti‐apoptotic pathways and protein kinase C (PKC)‐dependent pathways, which led to regulation of the actin cytoskeleton and tight junctions. These pathways contribute to the regeneration of the intestinal epithelium and modulation of the mucosal immune system, which, together with the inhibition of canonical TLR signalling, promote general immune tolerance. With this study we identified shared probiotic mechanisms and were the first to pinpoint the role of anti‐inflammatory probiotic signalling through TLR10.     

Enhancing the stress responses of probiotics for a lifestyle from gut to product and back again

Before a probiotic bacterium can even begin to fulfill its biological role, it must survive a battery of environmental stresses imposed during food processing and passage through the gastrointestinal tract (GIT). Food processing stresses include extremes in temperature, as well as osmotic, oxidative and food matrix stresses. Passage through the GIT is a hazardous journey for any bacteria with deleterious lows in pH encountered in the stomach to the detergent-like properties of bile in the duodenum. However, bacteria are equipped with an array of defense mechanisms to counteract intracellular damage or to enhance the robustness of the cell to withstand lethal external environments. Understanding these mechanisms in probiotic bacteria and indeed other bacterial groups has resulted in the development of a molecular toolbox to augment the technological and gastrointestinal performance of probiotics. This has been greatly aided by studies which examine the global cellular responses to stress highlighting distinct regulatory networks and which also identify novel mechanisms used by cells to cope with hazardous environments. This review highlights the latest studies which have exploited the bacterial stress response with a view to producing next-generation probiotic cultures and highlights the significance of studies which view the global bacterial stress response from an integrative systems biology perspective.     

Bioactives from probiotics for dermal health: functions and benefits

Probiotics have been extensively reviewed for decades, emphasizing on improving general gut health. Recently, more studies showed that probiotics may exert other health‐promoting effects beyond gut well‐being, attributed to the rise of the gut–brain axis correlations. Some of these new benefits include skin health such as improving atopic eczema, atopic dermatitis, healing of burn and scars, skin‐rejuvenating properties and improving skin innate immunity. Increasing evidence has also showed that bacterial compounds such as cell wall fragments, their metabolites and dead bacteria can elicit certain immune responses on the skin and improve skin barrier functions. This review aimed to underline the mechanisms or the exact compounds underlying the benefits of bacterial extract on the skin based on evidences from in vivo and in vitro studies. This review could be of help in screening of probiotic strains with potential dermal enhancing properties for topical applications.     

益生菌与口腔微生态调控的研究进展

口腔疾病的发生和发展与口腔微生物群落的失衡密切相关。益生菌是一类对人体健康有益的活的微生物,主要通过分泌抗菌物质、与致病菌竞争性定殖、调节毒力相关基因表达、调节宿主免疫反应、调节氧化应激反应、参与硝酸盐—亚硝酸盐—一氧化氮代谢循环通路、调整生物膜pH值等过程发挥其益生效能。研究发现,益生菌疗法能够降低龋齿的风险、改善牙周状况、提高口腔黏膜病的治疗效果,有望成为防治口腔疾病的潜在途径。本文就近年来益生菌与口腔微生态调控相关的研究情况做一综述。     

Modulating immune responses with probiotic bacteria

For many years, probiotic bacteria have been known to confer health benefits to the consumer. One possible mechanism for this may be the ability of probiotic bacteria to modulate immune responses. Oral administration of Lactobacillus casei strain Shirota (LcS) has been found to enhance innate immunity by stimulating the activity of splenic NK cells. Oral feeding with killed LcS was able to stimulate the production of Th1 cytokines, resulting in repressed production of IgE antibodies against Ovalbumin in experimental mice. The ability to switch mucosal immune responses towards Th1 with probiotic bacteria provides a strategy for treatment of allergic disorders. Growth of Meth A tumour cells in the lungs was also inhibited by intrapleural injection of LcS. Oral administration of other probiotic bacteria, such as Streptococcus thermophilus (St), Lactobacillus fermentum (Lf) and yeast (Y), elicited different immune responses. Mice that were prefed yeast or Lf followed by feeding with ovalbumin (OVA) responded better to vaccination with OVA than mice not given either probiotic or OVA or mice that had been prefed only OVA. However, antibody responses were significantly suppressed in response to vaccination with OVA in mice that had been prefed yeast followed by yeast and OVA as well as mice prefed Lf followed by Lf and OVA. Prefeeding St followed by OVA feeding enhanced cellular immune responses against ovalbumin. In contrast, mice prefed St followed by St + OVA were hyporesponsive against OVA. While antigen feeding alone appears to prime for an immune response, cofeeding antigen with probiotic bacteria can suppress both antibody and cellular immune responses and may provide an efficacious protocol to attenuate autoimmune diseases, such as experimental allergic encephalomyelitis, by jointly dosing with myelin basic protein and probiotic bacteria.     

Regulation of immune response at intestinal and peripheral sites by probiotics

The gut associated lymphoid tissue (GALT) should protect intestinal mucosa against pathogens, but also avoid hypersensitivity reactions to food proteins, normal bacterial flora and other environmental macromolecules. The interaction between epithelial cells and microflora is fundamental to establish gut mucosal barrier and GALT development. The normal colonization of intestine by commensal bacteria is thus crucial for a correct development of mucosal immune system. Probiotic bacteria are normal inhabitants of microflora and may confer health benefits to the host. The modification of the intestinal microflora towards a healthier probiotics enriched microflora may generate beneficial mucosal immunomodulatory effects and may represent a new strategy to cure intestinal and allergic diseases. The health benefits may be specific for different probiotic strains. Ongoing research is providing new insights into the probiotic beneficial effects and related mechanisms. This review represents an update of immunomodulatory activity of different probiotics and of the more accredited mechanisms underlying such activities. Presented at the Second Probiotic Conference, Košice, 15–19 September 2004, Slovakia.     

Bacterial probiotics induce an immune response in the honey bee (Hymenoptera: Apidae)

To explore immune system activation in the honey bee, Apis mellifera L., larvae of four ages were exposed through feeding to spores of a natural pathogen, Paenibacillus larvae larvae, to cells of a diverse set of related nonpathogenic bacteria, and to bacterial coat components. These larvae were then assayed for RNA levels of genes encoding two antibacterial peptides, abaecin and defensin. Larvae exposed to either P. l. larvae or a mix of nonpathogenic bacteria showed high RNA levels for the abaecin gene relative to controls. First instars responded significantly to the presence of the nonpathogenic mix within 12 h after exposure, a time when they remain highly susceptible to bacterial invasion. This response was sustained for two successive instars, eventually becoming 21-fold higher in larvae exposed to probiotic spores versus control larvae. The mixture of nonpathogenic bacteria is therefore presented as a potential surrogate for assaying the immune responses of different honey bee lineages. It also is proposed that nonpathogenic bacteria can be used as a probiotic to enhance honey bee immunity, helping bee larvae, and other life stages, survive attacks from pathogens in the field.     

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.     

A Review of the Advancements in Probiotic Delivery: Conventional vs. Non-conventional Formulations for Intestinal Flora Supplementation

Probiotic delivery systems are widely used nutraceutical products for the supplementation of natural intestinal flora. These delivery systems vary greatly in effectiveness to exert health benefits for a patient. Probiotic delivery systems can be categorized into conventional, pharmaceutical formulations, and non-conventional, mainly commercial food-based, products. The degree of health benefits provided by these probiotic formulations varies in their ability to deliver viable, functional bacteria in large enough numbers (effectiveness), to provide protection against the harsh effects of the gastric environment and intestinal bile (in vivo protection), and to survive formulation processes (viability). This review discusses the effectiveness of these probiotic delivery systems to deliver viable functional bacteria focusing on the ability to protect the encapsulated probiotics during formulation process as well as against harsh physiological conditions through formulation enhancements using coatings and polymer enhancements. A brief overview on the health benefits of probiotics, current formulation, patient and legal issues facing probiotic delivery, and possible recommendations for the enhanced delivery of probiotic bacteria are also provided. Newer advanced in vitro analyses that can accurately determine the effectiveness of a probiotic formulation are also discussed with an ideal probiotic delivery system hypothesized through a combination of the two probiotic delivery systems described.     

Using a Mathematical Model to Analyze the Role of Probiotics and Inflammation in Necrotizing Enterocolitis

Background

Necrotizing enterocolitis (NEC) is a severe disease of the gastrointestinal tract of pre-term babies and is thought to be related to the physiological immaturity of the intestine and altered levels of normal flora in the gut. Understanding the factors that contribute to the pathology of NEC may lead to the development of treatment strategies aimed at re-establishing the integrity of the epithelial wall and preventing the propagation of inflammation in NEC. Several studies have shown a reduced incidence and severity of NEC in neonates treated with probiotics (beneficial bacteria species).

Methodology/Principal Findings

The objective of this study is to use a mathematical model to predict the conditions under which probiotics may be successful in promoting the health of infants suffering from NEC. An ordinary differential equation model is developed that tracks the populations of pathogenic and probiotic bacteria in the intestinal lumen and in the blood/tissue region. The permeability of the intestinal epithelial layer is treated as a variable, and the role of the inflammatory response is included. The model predicts that in the presence of probiotics health is restored in many cases that would have been otherwise pathogenic. The timing of probiotic administration is also shown to determine whether or not health is restored. Finally, the model predicts that probiotics may be harmful to the NEC patient under very specific conditions, perhaps explaining the detrimental effects of probiotics observed in some clinical studies.

Conclusions/Significance

The reduced, experimentally motivated mathematical model that we have developed suggests how a certain general set of characteristics of probiotics can lead to beneficial or detrimental outcomes for infants suffering from NEC, depending on the influences of probiotics on defined features of the inflammatory response.     

Probiotic Formulations: Application and Status as Pharmaceuticals—A Review

The use of probiotics is a new way to control and treat infections in this modern era. Application of beneficial bacteria to protect against detrimental bacteria in the gastrointestinal tract and thus reap a positive health benefit is the basis of probiotic therapy. Probiotics have a long global history of traditional use. They are normally consumed through fermented foods and are currently sold mostly as ingredients in foods or nutritional supplements. They are also supplied as pharma products. Recent research has highlighted the probiotic potential in the treatment or prevention of disease conditions, maintenance of health, improving immunity and in the reduction in the risk of future diseases. But their position in the pharmaceutical industry is still not very clear. Clinical practitioners use probiotic pharma products mostly as supplements. Their status as drugs is still unclear. This review is aimed to analyze probiotics as pharmaceuticals, their current status as dietary supplements and drugs, existing probiotic preparations and future research needs.