Functional alteration of macrophages by a slime-forming Lactococcus lactis ssp. cremoris

In vitro comparison of the effects of probiotic, commensal and pathogenic strains on macrophage polarization

Macrophages are important with respect to both innate and adaptive immune responses and are known to differentiate into pro-inflammatory M1- or anti-inflammatory M2-phenotypes following activation. In order to study how different bacteria affect macrophage polarization, we exposed murine RAW 264.7 macrophages to sixteen different strains representing probiotic strains, pathogens, commensals and strains of food origin. Increased inducible nitric oxide synthase (iNOS) or arginase-1 gene expression indicates M1 or M2 polarization, respectively, and was quantified by qRT-PCR. Strains of Escherichia and Salmonella elevated iNOS expression more so than strains of Enterococcus, Lactobacillus and Lactococcus, indicating that Gram-negative strains are more potent M1 inducers. However, strain-specific responses were observed. For instance, Escherichia coli Nissle 1917 was a poor inducer of iNOS gene expression compared to the other E. coli strains, while Enterococcus faecalis Symbioflor-1 was more potent in this respect compared to all the eleven Gram-positive strains tested. Macrophage polarization was further characterized by quantifying secreted pro- and anti-inflammatory cytokines. Exposure to the pathogen E. coli 042 produced a cytokine profile indicating M1 differentiation, which is in accordance with the PCR data. However, exposure to most strains resulted in either high or low secretion levels of all cytokines tested, rather than a clear M1 or M2 profile. In general, the Gram-negative strains induced high levels of cytokine secretion compared to the Gram-positive strains. Interestingly, strains of human origin had a higher impact on macrophages compared to strains of food origin.

Exopolysaccharides of Lactobacillus reuteri: Their influence on adherence of E. coli to epithelial cells and inflammatory response

The aim of the study was to characterize exopolysaccharides (EPS) originated from Lactobacillus reuteri strain DSM 17938 (EPS-DSM17938) and L. reuteri strain L26 Biocenol™ (EPS-L26) and evaluate their influence on adherence of enterotoxigenic Escherichia coli (ETEC) to IPEC-1 cells and proinflammatory gene expression. Both EPS were d-glucan polysaccharides with higher molecular weight (Mw), but differing in spatial conformation and elicited variable cytokine profile. EPS-DSM17938, relatively linear polysaccharide with (1→4) and (1→6) glycosidic linkages, increased IL-1β gene expression (0.1mg/mL; P<0.05), while EPS-L26, more branched polysaccharide with (1→3) and (1→6) glycosidic linkages, exerted slight but statistically significant up-regulation of NF-κB, TNF-α and IL-6 mRNA (P<0.05). The most significant finding is that preincubation of IPEC-1 cells with both EPS followed by ETEC infection inhibit ETEC adhesion on IPEC-1 cells (P<0.01) and ETEC-induced gene expression of proinflammatory cytokine IL-1β and IL-6 (P<0.01).

Novel exopolysaccharides produced by Lactococcus lactis subsp. lactis, and the diversity of epsE genes in the exopolysaccharide biosynthesis gene clusters

To characterize novel variations of exopolysaccharides (EPSs) produced by dairy strains of Lactococcus lactis subsp. lactis and subsp. cremoris, the EPSs of five dairy strains of L. lactis were purified. Sugar composition analysis showed two novel EPSs produced by strains of L. lactis subsp. lactis. One strain produced EPS lacking galactose, and the other produced EPS containing fucose. Among the eps gene clusters of these strains, the highly conserved epsD and its neighboring epsE were sequenced. Sequence and PCR analysis revealed that epsE genes were strain-specific. By Southern blot analysis using epsD, the eps gene cluster in each strain was found to locate to the chromosome or a very large plasmid. This is the first report on the identification of two novel EPSs in L. lactis subsp. lactis. The strains can be detected among other strains by using epsE genes specific to them.

Exopolysaccharides production in Lactobacillus bulgaricus and Lactobacillus casei exploiting microfiltration

The physiology of Lactobacillus delbrueckii ssp. bulgaricus and Lactobacillus casei, extensively used in the dairy industry, was studied in order to evaluate key parameters in the synthesis of exopolysaccharides and to improve their production through novel fermentation processes. Selected strains were studied in shake flasks and in fermentor experiments using glucose and lactose as main carbon sources and bacto casitone as the only complex component, in a temperature range between 35 and 42 degrees C. The production of exopolysaccharides was monitored and correlated to the growth conditions using both a colorimetric assay and chromatographic methods. Fermentor experiments in batch mode yielded 100 mg l(-1) of EPS from L. bulgaricus and 350 mg l(-1) from L. casei. Moreover, the use of a microfiltration (MF) bioreactor resulted in exopolysaccharides (EPS) concentrations threefold and sixfold those of batch experiments, respectively. The monosaccharidic composition of the two analyzed polymers differed from those previously reported. The optimization of the production of EPSs using the MF fermentation strategy could permit the use of these molecules produced by generally recognised as safe (GRAS) microorganisms in the place of other polysaccharides in the food industry.

A novel immunostimulating aspect of Lactobacillus gasseri: induction of "Gasserokine" as chemoattractants for macrophages

The chemotactic activity of the culture supernatants from 14 strains of Lactobacillus acidophilus and L. gasseri was examined for murine macrophages. Significant macrophage chemotactic activity was observed in three strains of L. acidophilus and all strains of L. gasseri. The highest activity was observed in the supernatant (1131-sup) from 24-h cultures of L. gasseri JCM1131T. The chemotactic factor from 1131-sup, designated as "Gasserokine", was purified by the C18 reverse phase and ion-exchange chromatography. The purity of Gasserokine was checked by HPLC with the reverse-phase mode. The chemotactic activity of Gasserokine was also observed for human monocytes. The macrophage chemotaxis induced by L. gasseri JCM1131T culture supernatants was discovered to be a new biological function exerted by probiotic lactic acid bacteria. Therefore, the activity is expected to be used for one of the functional parameters in the immunomodulating properties of probiotic lactic acid bacteria.

Exopolysaccharide (EPS) biosynthesis by Lactobacillus sakei 0-1: production kinetics, enzyme activities and EPS yields

AIMS

To determine optimal exopolysaccharide (EPS) production conditions of the mesophilic lactic acid bacterium strain Lactobacillus sakei 0-1 and to detect possible links between EPS yields and the activity of relevant enzymes.

METHODS AND RESULTS

Fermentation experiments at different temperatures using either glucose or lactose were carried out. EPS production took place during the exponential growth phase. Low temperatures, applying glucose as carbohydrate source, resulted in the best bacterial growth, the highest amounts of EPS and the highest specific EPS production. Activities of 10 important enzymes involved in the EPS biosynthesis and the energy formation of Lact. sakei 0-1 were measured. The obtained results revealed that there is a clear link for some enzymes with EPS biosynthesis. It was also demonstrated clearly that the presence of rhamnose in the EPS building blocks is due to high activities of the enzymes involved in the rhamnose synthetic branch.

CONCLUSION

EPS production in Lact. sakei 0-1 is growth-associated and displays primary metabolite kinetics. Glucose as carbohydrate source and low temperatures enhance the EPS production. The enzymes involved in the biosynthesis of the activated sugar nucleotides play a major role in determining the monomeric composition of the synthesized EPS.

SIGNIFICANCE AND IMPACT OF THE STUDY

The proposed results contribute to a better understanding of the physiological factors influencing EPS production and the key enzymes involved in EPS biosynthesis by Lact. sakei.

Protection against influenza virus infection of mice fed Bifidobacterium breve YIT4064

Mice fed Bifidobacterium breve YIT4064 and immunized orally with influenza virus were more strongly protected against influenza virus infection of the lower respiratory tract than ones immunized with influenza virus only. The number of mice with enhanced anti-influenza virus immunoglobulin G (IgG) in serum upon oral administration of B. breve YIT4064 and oral immunization with influenza virus was significantly greater than that upon oral immunization with influenza virus only. These findings demonstrated that the oral administration of B. breve YIT4064 increased anti-influenza virus IgG antibodies in serum and protected against influenza virus infection. The oral administration of B. breve YIT4064 may enhance antigen-specific IgG against various pathogenic antigens taken orally and induce protection against various virus infections.

Induction of IFN-gamma and IL-1 alpha production in macrophages stimulated with phosphopolysaccharide produced by Lactococcus lactis ssp. cremoris

The induction of interferon (IFN) and interleukin-1 (IL-1) production in murine macrophages by a phosphopolysaccharide, produced by a dairy lactic acid bacteria, Lactococcus lactis ssp. cremoris, was investigated. When the phosphopolysaccharide was added into macrophage cultures at concentrations from 1 to 200 micrograms/ml, substantial IFN titers (6.2-79.2 IU/ml) were detected. Using the reverse transcription-polymerase chain reaction (RT-PCR), the expression of mRNA encoding IFN-gamma was verified in spleen macrophage cultures. Macrophages stimulated with the phosphopolysaccharide also produced IL-1 alpha at a concentration of 50 micrograms/ml. This study showed for the first time that phosphopolysaccharide derived from a dairy lactic acid bacterium can induce IFN-gamma and IL-1 alpha production in macrophages. These findings strongly suggest that the phosphopolysaccharide is a type of 'biological response modifier' and the fermented dairy foods containing Lactococcus lactis ssp. cremoris can be designated as a physiologically functional food.

Expression of mRNA encoding IFN alpha in macrophages stimulated with Lactobacillus gasseri

The ability of Lactobacillus gasseri, a dairy lactic acid bacterium, to induce interferon (IFN) was investigated in murine macrophage cultures. IFN alpha was substantially induced by some strains of L. gasseri and the titers were the highest at a concentration of 100 micrograms ml-1 of L. gasseri DSM20243T. The expression of mRNA encoding IFN alpha was detected in spleen-macrophages (SP-M phi) and Peyer's patch-adherent cells stimulated with L. gasseri DSM20243T. Actinomycin D and cycloheximide added to SP-M phi cultures showed that the mRNA was synthesized by 0.5 h, and that IFN alpha was produced within 3 to 6 h after the stimulation with L. gasseri DSM20243T. The results support the notion that dairy products containing L. gasseri can be 'physiologically functional foods'.

B-cell mitogen produced by slime-forming, encapsulated Lactococcus lactis ssp. cremoris isolated from ropy sour milk, viili

A substance, active as a B-cell mitogen, was isolated from the slime products produced by Lactococcus lactis ssp. cremoris KVS20. The mitogenic substance was prepared by anion-exchange chromatography and gel filtration chromatography and then purified by proteinase digestion and HPLC. Chemical analysis determined that the mitogenic substance was a phosphopolysaccharide and consisted of rhamnose, glucose, galactose, and phosphorus. The activity of the mitogenic substance was higher than that of the slime products. The optimal concentration for the activity was approximately 120 micrograms/ml. The mitogenic substance also had substantial mitogenic activity to spleen cells from C3H/HeJ mice, which are resistant to lipopolysaccharide. The findings indicated that a B-cell mitogen different from lipopolysaccharide is produced from L. lactis ssp. cremoris KVS20.

B-cell mitogenic activity of slime products produced from slime-forming, encapsulated Lactococcus lactis ssp. cremoris

The mitogenic activities of whole cell lyophylized preparations, cell-wall components, and slime products obtained from Lactococcus lactis ssp. cremoris KVS20 were examined on murine spleen cells. Whole cell lyophylized preparations and slime products significantly (P < .05) stimulated mitogenic responses of the cells. The highest activity was induced by slime products in which the optimal concentration was 116 microg/ml. The significant (P < .05) increase of mitogenic activity induced by slime products occurred at 24 h, and the peak response was obtained 48 h after the stimulation. The activity was much higher in the fraction enriched with B cells than in the fraction enriched with T cells. In addition, slime products induced mitogenic activity to spleen cells of athymic nu/nu mice. The chemical analysis of lipopolysaccharide and the minimal concentration for mitogenic response eliminated the possibility that the activity of slime products may be due to the contamination of lipopolysaccharide. The data demonstrate that slime products are a potent B-cell-dependent mitogen.

Passive immunizations of suckling mice and infants with bovine colostrum containing antibodies to human rotavirus

After immunizing 8-month pregnant Holstein cows with the human rotavirus MO strain, cow colostrum containing neutralizing antibody to four different serotypes of human rotavirus, designated Rota colostrum, was obtained. Oral inoculation of human rotavirus MO strain into 5-day-old BALB/c mice causes gastroenteritis characterized by diarrhea. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of Rota colostrum. Rota colostrum completely protected against rotavirus infection, but purified IgG and IgA obtained from Rota colostrum were unable to protect against infection. After grouping randomly 20 infants from a baby care center, 10 infants received 20 ml of Rota colostrum per day for 2 weeks and 10 control infants did not. Rotavirus-associated diarrhea developed in 7 of 10 infants in the control group. None of the three infants in the every day recipient group of Rota colostrum had such symptoms, and one of three infants in the every other day recipient group developed rotavirus-induced diarrhea. All four infants who received Rota colostrum after symptoms appeared developed diarrhea. Oral administration of Rota colostrum seems to be an effective and safe means of preventing diarrhea caused by human rotavirus infection.

Interferon induction in murine peritoneal macrophage by stimulation with Lactobacillus acidophilus

Induction of interferon for a kind of dairy lactic acid bacteria, Lactobacillus acidophilus (L. acidophilus), was investigated in murine peritoneal macrophage (M phi) cultures. Lactobacillus acidophilus JCM 1034, 1132T, 1229 and 2125 induced IFN (12-34 I.U./ml) in M phi cultures in vitro. Strain 1132T- and 2125-induced IFNs were characterized as IFN alpha/beta by treatment with anti-IFNs serum. The results indicate that the inducing activity of IFNs may be one of the available biological parameters for designating the dairy products containing L. acidophilus as "physiologically functional foods."