Microbiological and immunological strategies for treatment of inflammatory bowel disease

Bioinspired and biomimetic strategies for inflammatory bowel disease therapy

Inflammatory bowel disease (IBD) is an idiopathic chronic inflammatory bowel disease with high morbidity and an increased risk of cancer or death, resulting in a heavy societal medical burden. While current treatment modalities have been successful in achieving long-term remission and reducing the risk of complications, IBD remains incurable. Nanomedicine has the potential to address the high toxic side effects and low efficacy in IBD treatment. However, synthesized nanomedicines typically exhibit some degree of immune rejection, off-target effects, and a poor ability to cross biological barriers, limiting the development of clinical applications. The emergence of bionic materials and bionic technologies has reshaped the landscape in novel pharmaceutical fields. Biomimetic drug-delivery systems can effectively improve biocompatibility and reduce immunogenicity. Some bioinspired strategies can mimic specific components, targets or immune mechanisms in pathological processes to produce targeting effects for precise disease control. This article highlights recent research on bioinspired and biomimetic strategies for the treatment of IBD and discusses the challenges and future directions in the field to advance the treatment of IBD.

Novel drug delivery systems for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic illness characterized by relapsing inflammation of the intestines. The disorder is stratified according to the severity and is marked by its two main phenotypical representations: Ulcerative colitis and Crohn's disease. Pathogenesis of the disease is ambiguous and is expected to have interactivity between genetic disposition, environmental factors such as bacterial agents, and dysregulated immune response. Treatment for IBD aims to reduce symptom extent and severity and halt disease progression. The mainstay drugs have been 5-aminosalicylates (5-ASAs), corticosteroids, and immunosuppressive agents. Parenteral, oral and rectal routes are the conventional methods of drug delivery, and among all, oral administration is most widely adopted. However, problems of systematic drug reactions and low specificity in delivering drugs to the inflamed sites have emerged with these regular routes of delivery. Novel drug delivery systems have been introduced to overcome several therapeutic obstacles and for localized drug delivery to target tissues. Enteric-coated microneedle pills, various nano-drug delivery techniques, prodrug systems, lipid-based vesicular systems, hybrid drug delivery systems, and biologic drug delivery systems constitute some of these novel methods. Microneedles are painless, they dislodge their content at the affected site, and their release can be prolonged. Recombinant bacteria such as genetically engineered Lactococcus Lactis and eukaryotic cells, including GM immune cells and red blood cells as nanoparticle carriers, can be plausible delivery methods when evaluating biologic systems. Nano-particle drug delivery systems consisting of various techniques are also employed as nanoparticles can penetrate through inflamed regions and adhere to the thick mucus of the diseased site. Prodrug systems such as 5-ASAs formulations or their derivatives are effective in reducing colonic damage. Liposomes can be modified with both hydrophilic and lipophilic particles and act as lipid-based vesicular systems, while hybrid drug delivery systems containing an internal nanoparticle section for loading drugs are potential routes too. Leukosomes are also considered as possible carrier systems, and results from mouse models have revealed that they control anti- and pro-inflammatory molecules.

Evaluation of the Intestinal Colonizing Potential and Immunomodulating Capacity of Lactobacilli Microspheres

Lactobacilli species get degraded by acidic conditions in the stomach. Thus, the objective of this study was to (1) formulate and characterize gastro-resistant Lactobacilli microspheres and (2) evaluate the ability of Lactobacilli microspheres to colonize the intestine and their capacity to have an immunomodulating effect in vivo. The product yield and the encapsulation efficiency were 45% and 100%, respectively. The average microsphere particle size was 5 μm. Lactobacilli microspheres were most stable at 4°C and showed a better suspendibility in distilled water. Without encapsulation, the viability of bacteria decreased within 30 min. In the case of Lactobacilli microspheres, no Lactobacilli were released in the first 3 h, and highest release was observed at 4 h, thus, suggesting the significance of encapsulation of Lactobacilli. Lactobacilli microspheres maintained intestinal colonization only during the dosing period, and the serum IgG, serum IgA, fecal, intestinal, nasal IgA, and the serum interleukin-1β levels were higher in the Lactobacilli microsphere group compared with the blank microsphere and the lactobacilli solution group, suggesting that the Lactobacilli microspheres were more gastro-resistant and, hence, showed positive effects compared with the Lactobacilli solution. However, the Lactobacilli microspheres did not have a significant effect on the tumor necrosis factor-α levels.

Regenerative medicine: prospects for the treatment of inflammatory bowel disease

This article reviews the current understanding of the processes driving the development and progression of inflammatory bowel disease (IBD), discusses how the dynamic crosstalk between resident microorganisms, host cells and the immune system is required in order to maintain immune homeostasis, and considers innovative strategies that allow the modification or modulation of the intestinal microorganismal community as a potential approach for treating IBD. This article next rationalizes the use of cell-based regenerative medicine as treatment for IBD, discusses the obstacles hindering its success, summarizes some of the results of recent clinical trials employing these therapies, and discusses ongoing work to enhance mesenchymal stem/stromal cells, making them better suited to the task of repairing the damage within the IBD gut.

Protective effect of p-methoxycinnamic acid, an active phenolic acid against 1,2-dimethylhydrazine-induced colon carcinogenesis: modulating biotransforming bacterial enzymes and xenobiotic metabolizing enzymes

Objective of the study is to evaluate the modifying potential of p-methoxycinnamic acid (p-MCA), an active rice bran phenolic acid on biotransforming bacterial enzymes and xenobiotic metabolizing enzymes in 1,2-dimethylhydrazine-induced rat colon carcinogenesis. 48 male albino wistar rats were divided into six groups. Group1 (control) received modified pellet diet and 0.1 % carboxymethylcellulose; group2 received modified pellet diet along with p-MCA (80 mg/kg b.wt. p.o.) everyday for 16 weeks; groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) subcutaneous injection once a week for the first 4 weeks, while groups 4-6 received p-MCA at three different doses of 20, 40 and 80 mg/kg b.wt. p.o. everyday for 16 weeks. A significant increase in carcinogen-activating enzymes (cytochrome P450, cytochrome b5, cytochrome P4502E1, NADH-cytochrome-b5-reductase and NADPH-cytochrome-P450 reductase) with concomitant decrease in phaseII enzymes, DT-Diaphorase, glutathione S-transferase, UDP-glucuronyl-transferase and gamma glutamyltransferase were observed in group3 compared to control. DMH treatment significantly increased the activities of feacal and colonic bacterial enzymes (β-glucosidase, β-galactosidase, β-glucuronidase, nitroreductase, sulphatase and mucinase). p-MCA supplementation (40 mg/kg b.wt) to carcinogen exposed rats inhibited these enzymes, which were near those of control rats. The formation of dysplastic aberrant crypt foci in the colon and the histopathological observations of the liver also supports our biochemical findings. p-MCA (40 mg/kg b.wt.) offers remarkable modulating efficacy of biotransforming bacterial and xenobiotic metabolizing enzymes in colon carcinogenesis.

Anti-inflammatory effect of yoghurt in an experimental inflammatory bowel disease in mouse

Inflammatory bowel disease (IBD; Crohn′s disease and ulcerative colitis) is the clinical outcome of three interactive pathogenic factors: genetic susceptibility, environmental triggers and immune dis-regulation. At present, only the immune response is targeted by most therapeutic or preventive strategies. The beneficial effect of yoghurt on health as well as its immunomodulator effect on the gut immune system is well documented. The aim of this work was to study the possible beneficial effects of yoghurt consumption on an experimental model of IBD in mice. Balb/c mice were fed with yoghurt for 10 consecutive days. At the end of the feeding period the mice received three inoculations of 2, 4, 6-trinitrobenzene sulphonic acid (TNBS) solutions once a week for 3 consecutive weeks. After TNBS instillation the mice received yoghurt again for 10 consecutive days. IBD control received only TNBS. After treatments we analysed the number of IgA–secreting cells, CD4+, CD8+ T cells population and the number of apoptotic cells in the large intestine. The number of erythrocytes and leucocytes in peripheral blood mononuclear cells (PBMCs) was also determined. We demonstrated the antinflammatory effect of yoghurt in an experimental model of IBD induced by TNBS. The effect was mediated by an increase in the number of the IgA+cells, a decrease in CD8+ population and by the induction of apoptosis of the infiltrative cells in the large intestine.

Perioperative administration of probiotics: effects on immune response, anastomotic resistance and colonic mucosal trophism

PURPOSE

To investigate the effects of perioperative administration of diet containing probiotics on the immune response, anastomotic resistance, and colonic mucosal trophism in rats underwent left-sided colonic anastomosis.

METHODS

Sixty adults Wistar rats were randomized to two groups (A and B) with 30 animals each to receive or not a diet supplemented with probiotics (Streptococcus thermophilus e Lactobacillus helveticus) during pre- and postoperative period. They underwent laparotomy followed by left colon section and immediate anastomosis. Groups of 15 animals were killed either on the 4th (groups A1 and B1) or 7th PO (groups A2 and B2) days. The outcome variables were serum proteins, albumin, globulins and IgA, length and weight of the colon, mucosal weight, DNA content and anastomotic bursting pressure.

RESULTS

Colonic weight was greater in probiotic group compared to controls (1.69+/-0.34 g vs 1.48+/-0.26 g; p<0.05). Total serum proteins and globulin were higher in probiotic animals (proteins = 7.05+/-0.97 g/dl vs 6.57+/-0.66 g/dl e globulins = 5.1+/-0.62 g/dl vs 4.68+/-1.1 g/dl; p<0.05). Serum IgA increased from basal to post-operative days only in the probiotic group (p<0.01).

CONCLUSIONS

Perioperative probiotics enhanced the immune response and colonic weight. Probiotics failed to increase anastomotic resistance.

Colonization and impact of disease and other factors on intestinal microbiota

The aim of this study was to review the process of microbial colonization and the environmental and host factors that influence colonization and microbial succession. The impact of some diseases on intestinal microbiota composition is also described. Microbial colonization of the gut by maternal vaginal and fecal bacteria begins during and after birth. During the first 2 years of life, specific microbes become established in a process designated microbial succession. Microbial succession in the gastrointestinal tract is influenced by numerous external and internal host-related factors, and by the second year of life, the intestinal microbiota composition is considered identical to that of adults. Nevertheless, intestinal microbiota in both infants and adults remain incompletely characterized and their diversity poorly defined. The main explanation is that many intestinal bacteria that live in an anaerobic environment are difficult or impossible to culture outside the intestine. However, recent advances in molecular biology techniques have initiated the description of new bacteria species. The composition of gut microbiota can be modulated by host, environmental, and bacterial factors, and strong evidence has emerged of substantial modifications during illness or exposure to threatening experiences. It has been postulated that improvements in hygienic measures have led to an increase in allergic diseases ("hygiene hypothesis"). Alterations in gut microbiota and their functions have been widely associated with many chronic and degenerative diseases, including inflammatory bowel disease, colon cancer, and rheumatoid arthritis.

Oral feeding of Bifidobacterium bifidum (BGN4) prevents CD4(+) CD45RB(high) T cell-mediated inflammatory bowel disease by inhibition of disordered T cell activation

Probiotics have been considered as preventive agents for the control of inflammatory bowel disease (IBD). In this study, we assessed the immunomodulatory effect of Bifidobacterium bifidum BGN4 on the control of IBD using the CD4(+) CD45RB(high) T cell transfer disease model. The mice were fed for 4 weeks with either a conventional diet containing only skim milk or a diet containing skim milk with 0.3% (w/w) BGN4. The BGN4-fed mice showed normal weight growth, fewer clinical symptoms such as thickened wall and inflammatory cell infiltration, and lower levels of CD4(+) T lymphocyte infiltration and inflammatory cytokine productions than the skim milk-fed mice with IBD in the large intestine. Suppression of these cytokine productions, particularly IFN-gamma and MCP-1, through BGN4 treatment was also observed in the in vitro co-culture between intestinal epithelial cells and T cells. These findings suggested that a BGN4 supplemented diet could be helpful for the control of aberrant immune responses in the intestinal tissue.

Synbiotic therapy: a promising new adjunctive therapy for ulcerative colitis

Prebiotic and probiotic therapies are new strategies being used to treat gastrointestinal diseases. Recent evidence suggests that the administration of select prebiotics and probiotics, alone or in combination (the latter called "synbiotic" therapy) may improve the clinical outcome of patients with ulcerative colitis. We report a case of a pediatric ulcerative colitis patient who showed increased length of remission, resolution of symptoms, and improved quality of life following the administration of synbiotic therapy. The literature supporting the use of prebiotic, probiotic, and synbiotic therapies in adult ulcerative colitis is also reviewed.

Antibody repertoire development in fetal and neonatal piglets. IX. Three pathogen-associated molecular patterns act synergistically to allow germfree piglets to respond to type 2 thymus-independent and thymus-dependent antigens

Newborn piglets maintained germfree (GF) cannot respond to either thymus-dependent (TD) or type 2 thymus-independent Ags (TI-2) unless colonized with bacteria. We show here that pathogen-associated molecular patterns (PAMPs), including muramyl dipeptide (MDP), LPS, and a B-class CpG oligonucleotide (CpG-B), can substitute for gut flora in the induction of neonatal immunoresponsiveness. These PAMPs alone or in combination had little effect on serum IgG and IgA levels, but CpG-B and CpG-B + MDP elevated total IgM levels 3- to 7-fold above that seen in colonized controls after booster immunization. Although only CpG-B could alone stimulate immunoresponsiveness, co-administration of LPS or MDP resulted in a 5-fold increase in the IgG response to both immunogens. Co-administered MDP did not promote secondary IgG responses to either Ag but instead pronounced secondary IgM responses to the epitopes of both immunogens. LPS co-administered with CpG-B may promote class switch recombination or cause differentiation of previously switched cells that become responsive after exposure to CpG-B. Primary and secondary IgG responses equally recognized the epitopes of the TI-2 and TD immunogens, whereas IgM responses favored the TI-2 epitope. Because PAMPs alone can result in Abs to 2,4,6-triitrophenyl and FLU without immunization, it suggests they alone cause differentiation of B cells of the preimmune repertoire. The finding that both bacterial PAMPs and colonization are capable of stimulating Ab responses in both immunized and nonimmunized piglets suggests that PAMPs derived from host flora may play a major role in awakening adaptive immunity in neonates.

Mechanisms for the environmental regulation of gene expression: ecological aspects of animal development

The environment can play a significant role in the production of phenotypes. However, the developmental mechanisms by which the environmental agents effect normal development are just becoming known. At least three paths have been found through which the environment can modify gene activity. The first is the neuroendocrine route. Here, the nervous system monitors the environment and transfers signals to the endocrine system. The endocrine hormones can then alter gene expression. The second route involves environmental factors that change the methylation pattern of genes, thereby altering their transcriptional capabilities. The third route involves the direct induction of gene expression in the host by microbial symbionts. The normal regulation of phenotype production by the environment should be considered a normal component of development and developmental biology.

Engineering of the gut commensal bacterium Bacteroides ovatus to produce and secrete biologically active murine interleukin-2 in response to xylan

AIMS

The aim of this work was to engineer a gut commensal bacterium, Bacteroidesovatus, to produce and secrete a biologically active cytokine in a regulated manner as a basis for novel immunotherapies for chronic gut disorders.

METHODS AND RESULTS

Bacteroides ovatus was engineered to produce murine interleukin-2 (MuIL2) intracellularly in response to xylan in culture media by inserting the MuIL2 gene into the xylanase operon of the organism. A second strain was engineered to secrete MuIL2 by adding Bacteroides fragilis enterotoxin secretion signal sequence to the protein. The recombinant strains produced MuIL2 only in the presence of xylan as determined by ELISA of cell lysates and culture supernatants. The IL2-dependent cell line CTLL-2 was used to demonstrate that MuIL2 produced by both B. ovatus strains was biologically active. This activity could be blocked by an anti-IL2 neutralizing antibody. The xylan-inducible nature of this system was demonstrated by RT-PCR.

CONCLUSIONS

Bacteroides ovatus was successfully engineered to produce and secrete biologically active MuIL2 in a xylan-inducible manner.

SIGNIFICANCE AND IMPACT OF THE STUDY

The production and secretion of a biologically active mammalian protein by a member of the gut microflora could lead to the development of new long-term immunotherapies for inflammatory gut diseases.

Aetiology of inflammatory bowel disease (IBD): role of intestinal microbiota and gut-associated lymphoid tissue immune response

The aetiology of inflammatory bowel disease (IBD) probably involves a combination of genetic predisposition and environmental factors that may be channelled through an abnormality in gut-barrier function, with a loss of antigen tolerance. Some genetic markers that predispose to inflammatory disease have been identified (alleles DR2, DRB1*0103, DRB1*12 and mutations in the NOD2/CARD15 gene on chromosome 16). Alterations in the pattern of cytokine production by T cell subclasses leading to loss of tolerance to oral antigens have been documented. Moreover, a number of environmental factors (cigarette smoking, use of non-steroid anti-inflammatory drugs, psychological stress and the presence of the caecal appendix) have been postulated as a trigger of IBD. It has also been suggested that the gut microbiota plays a major role in the development and persistence of IBD, and numerous modifications of intestinal microbiota composition have been identified. As a result, manipulation of the microbiota with antibiotics is a current therapeutic strategy; more recently, however, a number of studies have reported promising results when using probiotic organisms to manipulate gut microbiota composition in order to restore tolerance to microbial antigens of the host's own microbiota.

Living recombinant Saccharomyces cerevisiae secreting proteins or peptides as a new drug delivery system in the gut

New strategies to prevent or treat diseases have been focusing on innovative approaches, such as the oral administration of living recombinant micro-organisms delivering active compounds in the digestive environment. The survival rate and the ability of two recombinant Saccharomyces cerevisiae strains (WppV(5)H(6) and WppGSTV(5)H(6)) to initiate the synthesis and secrete either a model peptide (peptide-V(5)H(6), MW: 5.6 kDa) or a model protein (glutathione-S-transferase-V(5)H(6), MW: 31.5 kDa) were studied in a gastric-small intestinal system simulating human digestive conditions. The WppV(5)H(6) and WppGSTV(5)H(6) strains respectively showed 83.1%+/-9.6 (n=3) and 95.3%+/-22.7 (n=4) survival rates in the model upper digestive tract after 270 min of digestion. The secretion products were detected as early as 90 min after the yeast intake/gene induction in each compartment of the in vitro system, but mostly in the jejunum and ileum. The GST-V(5)H(6) concentrations in the digestive medium reached 15 ng ml(-1), close to values measured in batch cultures. These results open up new opportunities for the set up of drug delivery systems based on engineered yeasts secreting compounds directly in the digestive tract. The main potential medical applications include the development of oral vaccines, the correction of metabolic disorders and the in situ production of biological mediators.

Mechanisms for the environmental regulation of gene expression

The environment can play a significant role in the production of phenotypes. However, the developmental mechanisms by which the environment can affect normal development are only now being elucidated. At least three paths have been found through which the environment can modify gene expression. The first is the neuroendocrine route, wherein the nervous system transmits signals from the environment to the endocrine system and the hormones alter gene expression. The second pathway involves environmental agents that change the methylation pattern of genes, thereby altering their transcriptional capacities. The third route involves the direct induction of gene expression in the host by its microbial symbionts. The normal environmental regulation of phenotype production should be considered a normal component of development and developmental biology.

Effects of probiotic on intestinal mucosa of patients with ulcerative colitis

AIM: To investigate the effects of probiotic on intestinal mucosae of patients with ulcerative colitis (UC), and to evaluate the role of probiotic in preventing the relapse of UC.

METHODS: Thirty patients received treatment with sulphasalazine (SASP) and glucocorticoid and then were randomly administered bifid triple viable capsule (BIFICO) (1.26 g/d), or an identical placebo (starch) for 8 wk. Fecal samples were collected for stool culture 2 wk before and after the randomized treatments. The patients were evaluated clinically, endoscopically and histologically after 2 mo of treatment or in case of relapse of UC. p65 and IκB expressions were determined by Western blot analysis. DNA-binding activity of NF-κB in colonic nuclear extracts was detected by electrophoretic mobility shift assay (EMSA). mRNA expressions of cytokines were identified by semi-quantitative assay, reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS: Three patients (20%) in the BIFICO group had relapses during 2-mo follow-up period, compared with 14 (93.3%) in placebo group (P < 0.01). The concentration of fecal lactobacilli, bifidobacteria was significantly increased in BIFICO-treated group only (P < 0.01).The expressions of NF-κB p65 and DNA binding activity of NF-κB were significantly attenuated in the treatment group than that in control (P < 0.05). The mRNA expression of anti-inflammatory cytokines was elevated in comparison with the control group.

CONCLUSION: The probiotic could impede the activation of NF-κB, decrease the expressions of TNF-α and IL-1β and elevate the expression of IL-10. These results suggest that oral administration of this new probiotic preparation is effective in preventing flare-ups of chronic UC. It may become a prophylactic drug to decrease the relapse of UC.

Role of commensal bacteria in development of gut-associated lymphoid tissues and preimmune antibody repertoire

Intestinal bacteria are required for development of gut-associated lymphoid tissues (GALT), which mediate a variety of host immune functions, such as mucosal immunity and oral tolerance. In rabbits, the intestinal microflora are also required for developing the preimmune Ab repertoire by promoting somatic diversification of Ig genes in B cells that have migrated to GALT. We studied the mechanism of bacteria-induced GALT development. Bacteria were introduced into rabbits in which the appendix had been rendered germfree by microsurgery (we refer to these rabbits as germfree-appendix rabbits). We then identified specific members of the intestinal flora that promote GALT development. The combination of Bacteroides fragilis and Bacillus subtilis consistently promoted GALT development and led to development of the preimmune Ab repertoire, as shown by an increase in somatic diversification of VDJ-C micro genes in appendix B cells. Neither species alone consistently induced GALT development, nor did Clostridium subterminale, Escherichia coli, or Staphylococcus epidermidis. B. fragilis, which by itself is immunogenic, did not promote GALT development; hence, GALT development in rabbits does not appear to be the result of an Ag-specific immune response. To identify bacterial pathways required for GALT development, we introduced B. fragilis along with stress-response mutants of B. subtilis into germfree-appendix rabbits. We identified two Spo0A-controlled stress responses, sporulation and secretion of the protein YqxM, which are required for GALT development. We conclude that specific members of the commensal, intestinal flora drive GALT development through a specific subset of stress responses.

Functional modulation of enterocytes by gram-positive and gram-negative microorganisms

Clinical studies have suggested that so-called probiotic bacteria may be effective as therapy in inflammatory bowel disease. However, the molecular mechanisms of their interaction with the intestinal surface remain undefined. The influence of whole probiotic bacteria [Escherichia coli Nissle 1917 (EcN); probiotic mixture VSL#3 (PM)], bacterial cell lysates, and conditioned media on transepithelial resistance (TER), IL-8 secretion, mucin gene expression, and tight junction proteins were determined in T84 and HT-29 intestinal epithelial cells (IEC). In addition, effects on pathogen (Salmonella dublin)-induced alterations were analyzed. EcN as well as debris and cell extracts induced IL-8 secretion from IEC, whereas no such effect was observed following incubation with the PM. The PM and soluble protein(s) released from the PM increased TER, prevented pathogen-induced decrease in TER, and were shown to stabilize tight junctions. The PM induced expression of mucins in IEC, and these organisms as well as EcN diminished S. dublin-induced cell death. Inhibition of MAPKs with PD-98059 or SB-203580 significantly decreased alterations in IL-8 synthesis and mucin expression and affected the regulation of TER. Probiotics and protein(s) released by these organisms may functionally modulate the intestinal epithelium of the host by different mechanisms, including the competition of whole organisms for contact with the epithelial surface as well as stabilization of the cytoskeleton and barrier function and the induction of mucin expression. Gram-negative and gram-positive organisms differ in the mechanisms activated, and a combination of organisms might be more effective than the application of a single strain.

Identification of Lactobacillus reuteri genes specifically induced in the mouse gastrointestinal tract

Lactobacilli are common inhabitants of the gastrointestinal tracts of mammals and have received considerable attention due to their putative health-promoting properties. Little is known about the traits that enhance the ability of these bacteria to inhabit the gastrointestinal tract. In this paper we describe the development and application of a strategy based on in vivo expression technology (IVET) that enables detection of Lactobacillus reuteri genes specifically induced in the murine gut. A plasmid-based system was constructed containing 'ermGT (which confers lincomycin resistance) as the primary reporter gene for selection of promoters active in the gastrointestinal tract of mice treated with lincomycin. A second reporter gene, 'bglM (beta-glucanase), allowed differentiation between constitutive and in vivo inducible promoters. The system was successfully tested in vitro and in vivo by using a constitutive promoter. Application of the IVET system with chromosomal DNA of L. reuteri 100-23 and reconstituted lactobacillus-free mice revealed three genes induced specifically during colonization. Two of the sequences showed homology to genes encoding xylose isomerase (xylA) and peptide methionine sulfoxide reductase (msrB), which are involved in nutrient acquisition and stress responses, respectively. The third locus showed homology to the gene encoding a protein whose function is not known. Our IVET system has the potential to identify genes of lactobacilli that have not previously been functionally characterized but which may be essential for growth of these bacteria in the gastrointestinal ecosystem.

Genetically modified lactic acid bacteria: applications to food or health and risk assessment

Lactic acid bacteria have a long history of use in fermented food products. Progress in gene technology allows their modification by introducing new genes or by modifying their metabolic functions. These modifications may lead to improvements in food technology (bacteria better fitted to technological processes, leading to improved organoleptic properties em leader ), or to new applications including bacteria producing therapeutic molecules that could be delivered by mouth. Examples in these two fields will be discussed, at the same time evaluating their potential benefit to society and the possible risks associated with their use. Risk assessment and expected benefits will determine the future use of modified bacteria in the domains of food technology and health.