Constitutive delivery of bovine beta-lactoglobulin to the digestive tracts of gnotobiotic mice by engineered Lactobacillus casei

The gut microbiota is critical for maturation of the immune system. Recent evidence suggests that early establishment of lactobacilli in the intestinal microbiota, during neonatal colonization or by probiotic supplementation, could prevent the development of allergic disorders. Postnatal maturation of the gut immune system with allergen-producing lactobacilli colonizing the digestive tract could then affect the development of further allergic sensitization. In this paper, we describe construction of a recombinant Lactobacillus casei strain that can constitutively deliver bovine beta-lactoglobulin (BLG), a major cow's milk allergen, to the guts of gnotobiotic mice. The blg gene was inserted into the L. casei chromosome downstream of an endogenous promoter. BLG production was improved by fusing the propeptide LEISSTCDA (LEISS) to the BLG mature moiety. This led to a 10-fold increase in LEISS-BLG production compared to the production obtained without the propeptide and also led to enhanced secretion corresponding to 5% of the total production. After inoculation into germfree C3H/HeN mice, the genetic stability of the recombinant strain and in vivo BLG production were confirmed for at least 10 weeks. BLG stimulation of spleen cells from mice monoassociated with the BLG-producing lactobacilli induced secretion of the Th1 cytokine gamma interferon and, to a lesser extent, the Th2 cytokine interleukin-5. No BLG-specific immunoglobulin G1 (IgG1), IgG2a, or IgA was detected in sera or in fecal samples. These results suggest that gut colonization with allergen-producing lactobacilli could provide a useful model for studying the modulation of allergic disorders.     

应用体内外实验筛选可降低牛乳β-乳球蛋白过敏的乳杆菌

【目的】通过体内外实验评估5种乳杆菌缓解牛乳β-乳球蛋白(BLG)过敏的作用,为今后筛选具有抗过敏活性的乳杆菌提供参考。【方法】首先体外分析5种活的/热致死的乳杆菌促进小鼠原代淋巴细胞分泌细胞因子(CK)IFN-γ和IL-4的水平,随后应用小鼠BLG过敏模型评估这5种乳杆菌抑制过敏的能力。将实验动物随机分为空白组、BLG致敏组和5种活的/热致死乳杆菌组。采用ELISA法检测各组小鼠淋巴细胞分泌Thl/Th2型CK的水平,并测定小鼠血清中总IgE和BLG特异性IgE的含量。【结果】在体外可促进淋巴细胞分泌IFN-γ、抑制IL-4,使其IFN-γ/IL-4比值(代表Thl/Th2细胞平衡)显著高于正常对照组(P<0.05)的乳杆菌,在体内实验中也能有效提高致敏小鼠淋巴细胞的IFN-γ/IL-4分泌率,并显著降低致敏小鼠血清中总IgE和BLG特异性IgE的水平(P<0.05)。相反,在体外的IFN-γ/IL-4比值较低的乳杆菌,不能缓解特异性IgE抗体介导的食物过敏反应。【结论】基于乳杆菌体外刺激小鼠原代淋巴细胞分泌Th1/Th2型CK的结果,可以预测菌株在体内具有可通过纠正Th2占优势的Th1/Th2细胞失衡,下调抗体分泌量,缓解小鼠BLG过敏症状的能力。     

Germ-free status and altered caecal subdominant microbiota are associated with a high susceptibility to cow's milk allergy in mice

Studies suggesting that the development of atopy is linked to gut microbiota composition are inconclusive on whether dysbiosis precedes or arises from allergic symptoms. Using a mouse model of cow's milk allergy, we aimed at investigating the link between the intestinal microbiota, allergic sensitization, and the severity of symptoms. Germ-free and conventional mice were orally sensitized with whey proteins and cholera toxin, and then orally challenged with β-lactoglobulin (BLG). Allergic responses were monitored with clinical symptoms, plasma markers of sensitization, and the T-helper Th1/Th2/regulatory-T-cell balance. Microbiota compositions were analysed using denaturing gradient gel electrophoresis and culture methods. Germ-free mice were found to be more responsive than conventional mice to sensitization, displaying a greater reduction of rectal temperature upon challenge, higher levels of blood mouse mast cell protease-1 (mMCP-1) and BLG-specific immunoglobulin G1 (IgG1), and a systemic Th2-skewed response. This may be explained by a high susceptibility to release mMCP-1 even in the presence of low levels of IgE. Sensitization did not alter the microbiota composition. However, the absence of or low Staphylococcus colonization in the caecum was associated with high allergic manifestations. This work demonstrates that intestinal colonization protects against oral sensitization and allergic response. This is the first study to show a relationship between alterations within the subdominant microbiota and severity of food allergy.     

乳杆菌对牛乳β-乳球蛋白致敏小鼠淋巴细胞分泌Th1/Th2型细胞因子和抗体的体外影响

为了分析乳杆菌对致敏小鼠脾淋巴细胞分泌Th1/Th2细胞因子及抗体的体外影响,用牛乳β-乳球蛋白腹腔注射BALB/c小鼠建立过敏症模型,造模成功后,分离致敏小鼠的脾淋巴细胞并与4种活/死乳杆菌(107 CFU/mL)体外共同孵育,ELISA法检测细胞上清液中细胞因子(IL-12、IFN-γ和IL-4)和抗体(总IgE、β-Lg特异性IgE和总IgG)含量。4种活/死乳杆菌均可体外调节致敏小鼠脾淋巴细胞分泌细胞因子和抗体的水平,特别是热致死的发酵乳杆菌和嗜酸乳杆菌可提高淋巴细胞IL-12和IFN-γ的分泌,抑制IL-4的分泌,使其IFN-γ/IL-4比值(代表Th1/Th2细胞平衡)高于活菌,与空白对照组比较差异显著(P<0.05)。同时,这两株热致死菌还可显著下调细胞上清液中总IgE、特异性IgE和总IgG抗体的浓度(P<0.05)。试验结果表明乳杆菌可提高牛乳β-乳球蛋白致敏小鼠脾淋巴细胞的IFN-γ/IL-4比值,进而纠正Th2占优势的Th1/Th2失衡,下调抗体分泌量,且具有菌株特异性。     

Induction of oral tolerance in mice by continuous feeding with beta-lactoglobulin and milk

We examined the immune response of mice to beta-lactoglobulin (BLG), a potent milk allergen, after continuous feeding of a BLG solution or milk instead of drinking-water. Strong suppression of the anti-BLG antibody response and antigen-specific T cell response were observed in mice fed BLG and milk. Although the profile of the antibody specificity to BLG peptides in mice fed BLG or milk was different from the control, the dominant determinants were still recognized and a limited number of new recognition sites appeared by BLG or milk feeding. These findings suggest that continuous feeding with BLG or milk not only induced tolerance in the periphery, but also priming. In terms of the antigen-specific IgG subclass response, the production of both IgG1 and IgG2a was significantly reduced. The cytokine secretion of interleukin (IL)-2, IFN-gamma and IL-10 was also reduced in the culture supernatants of lymph node cells from the mice fed BLG. The results indicate that the continuous feeding of BLG or milk induces suppression of both Th1- and Th2-dependent responses. This may reflect a state of oral tolerance induced by food ingestion.     

Enterococcus faecalis from Healthy Infants Modulates Inflammation through MAPK Signaling Pathways

Colonizing commensal bacteria after birth are required for the proper development of the gastrointestinal tract. It is believed that bacterial colonization pattern in neonatal gut affects gut barrier function and immune system maturation. Studies on the development of faecal microbiota in infants showed that the neonatal gut was first colonized with enterococci followed by other microbiota such as Bifidobacterium. Other studies showed that babies who developed allergy were less often colonized with Enterococcus during the first month of life as compared to healthy infants. Many studies have been conducted to elucidate how bifidobacteria or lactobacilli, some of which are considered probiotic, regulate infant gut immunity. However, fewer studies have been focused on enterococi. In our study, we demonstrate that E. faecalis, isolated from healthy newborns, suppress inflammatory responses activated in vivo and in vitro. We found E. faecalis attenuates proinflammatory cytokine secretions, especially IL-8, through JNK and p38 signaling pathways. This finding shed light on how the first colonizer, E.faecalis, regulates inflammatory responses in the host.     

Early-Life Gut Bacteria Associate with IL-4?, IL-10? and IFN-γ Production at Two Years of Age

Microbial exposure early in life influences immune maturation and potentially also the development of immune-mediated disease. Here we studied early-life gut colonization in relation to cytokine responses at two years of age. Fecal samples were collected from infants during the first two months of life. DNA was extracted from the fecal samples and Bifidobacterium (B.) adolescentis, B. breve, B. bifidum, a group of lactobacilli (L. casei, L. paracasei and L. rhamnosus) as well as Staphylococcus (S.) aureus were detected with real time PCR. Peripheral mononuclear cells were stimulated with phytohaemagglutinin (PHA) and numbers of IL-4−, IL-10− and IFN-γ secreting cells were evaluated using ELISpot. We further stimulated peripheral blood mononuclear cells with bacterial supernatants in vitro and assessed the IL-4−, IL-10− and IFN-γ inducing capacity by flow cytometry and ELISA. Early S. aureus colonization associated with higher numbers of IL-4− (p = 0.022) and IL-10 (p = 0.016) producing cells at two years of age. In contrast to colonization with S. aureus alone, co-colonization with lactobacilli associated with suppression of IL-4− (p = 0.004), IL-10− (p = 0.004) and IFN-γ (p = 0.034) secreting cells. In vitro stimulations of mononuclear cells with bacterial supernatants supported a suppressive role of L. rhamnosus GG on S. aureus-induced cytokine responses. We demonstrate that the early gut colonization pattern associates with the PHA-induced cytokine profile at two years of age and our in vitro findings support that specific bacterial species influence the T helper cell subsets. This suggests that dysbiosis in the early microbiota may modulate the risk of developing inflammatory conditions like allergy.     

Interaction with Intestinal Epithelial Cells Promotes an Immunosuppressive Phenotype in Lactobacillus casei

Maintenance of the immunological tolerance and homeostasis in the gut is associated with the composition of the intestinal microbiota. We here report that cultivation of Lactobacillus casei ATCC 334 in the presence of human intestinal epithelial cells promotes functional changes in bacteria. In particular, the interaction enhanced the immunosuppressive phenotype of L. casei as demonstrated by the ability of L. casei to generate functional regulatory T cells (CD4+CD25+FoxP3+) and production of the anti-inflammatory cytokine interleukin-10 by human peripheral blood mononuclear cells. The results indicate microbe-host cross-talk that changes features of microbes, and suggest that in vitro simulation of epithelial cell interaction can reveal functional properties of gut microbes more accurately than conventional cultivation.     

Dynamics of Gut Microbiota in Autoimmune Lupus

Gut microbiota has been recognized as an important environmental factor in health, as well as in metabolic and immunological diseases, in which perturbation of the host gut microbiota is often observed in the diseased state. However, little is known on the role of gut microbiota in systemic lupus erythematosus. We investigated the effects of host genetics, sex, age, and dietary intervention on the gut microbiome in a murine lupus model. In young, female lupus-prone mice resembling women at childbearing age, a population with the highest risk for lupus, we found marked depletion of lactobacilli, and increases in Lachnospiraceae and overall diversity compared to age-matched healthy controls. The predicted metagenomic profile in lupus-prone mice showed a significant enrichment of bacterial motility- and sporulation-related pathways. Retinoic acid as a dietary intervention restored lactobacilli that were downregulated in lupus-prone mice, and this correlated with improved symptoms. The predicted metagenomes also showed that retinoic acid reversed many lupus-associated changes in microbial functions that deviated from the control. In addition, gut microbiota of lupus-prone mice were different between sexes, and an overrepresentation of Lachnospiraceae in females was associated with an earlier onset of and/or more severe lupus symptoms. Clostridiaceae and Lachnospiraceae, both harboring butyrate-producing genera, were more abundant in the gut of lupus-prone mice at specific time points during lupus progression. Together, our results demonstrate the dynamics of gut microbiota in murine lupus and provide evidence to suggest the use of probiotic lactobacilli and retinoic acid as dietary supplements to relieve inflammatory flares in lupus patients.     

Patterns of early gut colonization shape future immune responses of the host

The most important trigger for immune system development is the exposure to microbial components immediately after birth. Moreover, targeted manipulation of the microbiota can be used to change host susceptibility to immune-mediated diseases. Our aim was to analyze how differences in early gut colonization patterns change the composition of the resident microbiota and future immune system reactivity. Germ-free (GF) mice were either inoculated by single oral gavage of caecal content or let colonized by co-housing with specific pathogen-free (SPF) mice at different time points in the postnatal period. The microbiota composition was analyzed by denaturing gradient gel electrophoresis for 16S rRNA gene followed by principal component analysis. Furthermore, immune functions and cytokine concentrations were analyzed using flow cytometry, ELISA or multiplex bead assay. We found that a single oral inoculation of GF mice at three weeks of age permanently changed the gut microbiota composition, which was not possible to achieve at one week of age. Interestingly, the ex-GF mice inoculated at three weeks of age were also the only mice with an increased pro-inflammatory immune response. In contrast, the composition of the gut microbiota of ex-GF mice that were co-housed with SPF mice at different time points was similar to the gut microbiota in the barrier maintained SPF mice. The existence of a short GF postnatal period permanently changed levels of systemic regulatory T cells, NK and NKT cells, and cytokine production. In conclusion, a time window exists that enables the artificial colonization of GF mice by a single oral dose of caecal content, which may modify the future immune phenotype of the host. Moreover, delayed microbial colonization of the gut causes permanent changes in the immune system.     

Early colonization with a group of Lactobacilli decreases the risk for allergy at five years of age despite allergic heredity

Background

Microbial deprivation early in life can potentially influence immune mediated disease development such as allergy. The aims of this study were to investigate the influence of parental allergy on the infant gut colonization and associations between infant gut microbiota and allergic disease at five years of age.

Methods and Findings

Fecal samples were collected from 58 infants, with allergic or non-allergic parents respectively, at one and two weeks as well as at one, two and twelve months of life. DNA was extracted from the fecal samples and Real time PCR, using species-specific primers, was used for detection of Bifidobacterium (B.) adolescentis, B. breve, B. bifidum, Clostridium (C.) difficile, a group of Lactobacilli (Lactobacillus (L.) casei, L. paracasei and L. rhamnosus) as well as Staphylococcus (S.) aureus. Infants with non-allergic parents were more frequently colonized by Lactobacilli compared to infants with allergic parents (p = 0.014). However, non-allergic five-year olds acquired Lactobacilli more frequently during their first weeks of life, than their allergic counterparts, irrespectively of parental allergy (p = 0.009, p = 0.028). Further the non-allergic children were colonized with Lactobacilli on more occasions during the first two months of life (p = 0.038). Also, significantly more non-allergic children were colonized with B. bifidum at one week of age than the children allergic at five years (p = 0.048).

Conclusion

In this study we show that heredity for allergy has an impact on the gut microbiota in infants but also that early Lactobacilli (L. casei, L. paracasei, L. rhamnosus) colonization seems to decrease the risk for allergy at five years of age despite allergic heredity.     

The Effect of Lactobacillus casei 32G on the Mouse Cecum Microbiota and Innate Immune Response Is Dose and Time Dependent

Lactobacilli have been associated with a variety of immunomodulatory effects and some of these effects have been related to changes in gastrointestinal microbiota. However, the relationship between probiotic dose, time since probiotic consumption, changes in the microbiota, and immune system requires further investigation. The objective of this study was to determine if the effect of Lactobacillus casei 32G on the murine gastrointestinal microbiota and immune function are dose and time dependent. Mice were fed L. casei 32G at doses of 10⁶, 10⁷, or 10⁸ CFU/day/mouse for seven days and were sacrificed 0.5h, 3.5h, 12h, or 24h after the last administration. The ileum tissue and the cecal content were collected for immune profiling by qPCR and microbiota analysis, respectively. The time required for L. casei 32G to reach the cecum was monitored by qPCR and the 32G bolus reaches the cecum 3.5h after the last administration. L. casei 32G altered the cecal microbiota with the predominance of Lachnospiraceae IS, and Oscillospira decreasing significantly (p < 0.05) in the mice receiving 10⁸ CFU/mouse 32G relative to the control mice, while a significant (p < 0.05) increase was observed in the prevalence of lactobacilli. The lactobacilli that increased were determined to be a commensal lactobacilli. Interestingly, no significant difference in the overall microbiota composition, regardless of 32G doses, was observed at the 12h time point. A likely explanation for this observation is the level of feed derived-nutrients resulting from the 12h light/dark cycle. 32G results in consistent increases in Clec2h expression and reductions in TLR-2, alpha-defensins, and lysozyme. Changes in expression of these components of the innate immune system are one possible explanation for the observed changes in the cecal microbiota. Additionally, 32G administration was observed to alter the expression of cytokines (IL-10rb and TNF-α) in a manner consistent with an anti-inflammatory response.     

Alterations of the gut microbiota in high-fat diet mice is strongly linked to oxidative stress

Alterations of the gut microbiota induced by diet exert a strong influence on the development of metabolic syndrome. In this study, we prove the hypothesis that the long-term high-fat diet (HFD) may influence gut microbiota directly and/or indirectly by changing the redox state. Lipoic acid (LA), as a universal antioxidant, was used to improve the redox state. Reactive oxygen species (ROS), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) were analyzed to profile oxidative stress states. PCR-denaturing gradient gel electrophoresis (DGGE) was used to describe gut flora structures, while plate count was employed for the quantitative analysis of Escherichia coli, lactobacilli, and enterococcus. The influence of redox state on the vitality of gut-derived bacteria was measured in vitro. ROS and MDA, which significantly decreased in LA mice compared with HFD mice, showed a strong positive association with E. coli and enterococcus (P?<?0.05) and a negative association with lactobacilli (P?<?0.05). Increased T-AOC in LA mice showed a high positive association with lactobacilli (P?<?0.05) and a negative correlation with E. coli and enterococcus. These correlations implied that the dietary effects on the gut microbiota were conferred, at least in part, through an effect on oxidative stress. This study provides evidence that modulation of the redox state by an antioxidant has the potential to improve gut microbiota, which has relevance for metabolic health.     

Probiotics importance and their immunomodulatory properties

Mammalian intestine contains a large diversity of commensal microbiota, which is far more than the number of host cells. Probiotics play an insecure and protective role against the colonization of intestinal pathogenic microbes and increase mucosal integrity by stimulating epithelial cells. Probiotics have innate capabilities in many ways, including receptor antagonism, receptor expression, binding and expression of adapter proteins, expression of negative regulatory signal molecules, induction of microRNAs, endotoxin tolerance, and ultimately secretion of immunomodulatory proteins, lipids, and metabolites to modulate the immune system. Probiotic bacteria can affect homeostasis, inflammation, and immunopathology through direct or indirect effects on signaling pathways as immunosuppressant or activators. Probiotics suppress inflammation by inhibiting various signaling pathways such as the nuclear factor-κB (NF-κβ) pathway, possibly related to alterations in mitogen-activated protein kinases and pattern recognition receptors pathways. Probiotics can also inhibit the binding of lipopolysaccharides to the CD14 receptor, thereby reducing the overall activation of NF-κβ and producing proinflammatory cytokines. Some effects of modulation by probiotics include cytokine production by epithelial cells, increased mucin secretion, increased activity of phagocytosis, and activation of T and natural killer T cells, stimulation of immunoglobulin A production and decreased T cell proliferation. Intestinal microbiota has a major impact on the systemic immune system. Specific microbiota controls the differentiation of cells in lamina propria, in which Th17 cells secrete interleukin 17. The presence of Th17 and Treg cells in the small intestine is associated with intestinal microbiota, with the preferential Treg differentiation and the absence of Th17 cells, possibly reflecting alterations in the lamina propria cytokines and the intestinal gut microbiota.     

Disentangling the effect of host genetics and gut microbiota on resistance to an intestinal parasite

Resistance to infection is a multifactorial trait, and recent work has suggested that the gut microbiota can also contribute to resistance. Here, we performed a fecal microbiota transplant to disentangle the contribution of the gut microbiota and host genetics as drivers of resistance to the intestinal nematode Heligmosomoides polygyrus. We transplanted the microbiota of a strain of mice (SJL), resistant to H. polygyrus, into a susceptible strain (CBA) and vice-versa. We predicted that if the microbiota shapes resistance to H. polygyrus, the FMT should reverse the pattern of resistance between the two host strains. The two host strains had different microbiota diversities and compositions before the start of the experiment, and the FMT altered the microbiota of recipient mice. One mouse strain (SJL) was more resistant to colonization by the heterologous microbiota, and it maintained its resistance profile to H. polygyrus (lower parasite burden) independently of the FMT. On the contrary, CBA mice harbored parasites with lower fecundity during the early stage of the infection, and had an up-regulated expression of the cytokine IL-4 (a marker of H. polygyrus resistance) after receiving the heterologous microbiota. Therefore, while host genetics remains the main factor shaping the pattern of resistance to H. polygyrus, the composition of the gut microbiota also seems to play a strain-specific role.     

In vitro Effects of Prebiotics and Synbiotics on Apis cerana Gut Microbiota

This study aimed to investigate in vitro effects of the selected prebiotics alone, and in combination with two potential probiotic Lactobacillus strains on the microbial composition of Apis cerana gut microbiota and acid production. Four prebiotics, inulin, fructo-oligosaccharides, xylo-oligosaccharides, and isomalto-oligosaccharides were chosen, and glucose served as the carbon source. Supplementation of this four prebiotics increased numbers of Bifidobacterium and lactic acid bacteria while decreasing the pH value of in vitro fermentation broth inoculated with A. cerana gut microbiota compared to glucose. Then, two potential probiotics derived from A. cerana gut at different dosages, Lactobacillus helveticus KM7 and Limosilactobacillus reuteri LP4 were added with isomalto-oligosaccharides in fermentation broth inoculated with A. cerana gut microbiota, respectively. The most pronounced impact was observed with isomalto-oligosaccharides. Compared to isomalto-oligosaccharides alone, the combination of isomalto-oligosaccharides with both lactobacilli strains induced the growth of Bifidobacterium, LAB, and total bacteria and reduced the proliferation of Enterococcus and fungi. Consistent with these results, the altered metabolic activity was observed as lowered pH in in vitro culture of gut microbiota supplemented with isomalto-oligosaccharides and lactobacilli strains. The symbiotic impact varied with the types and concentration of Lactobacillus strains and fermentation time. The more effective ability was observed with IMO combined with L. helveticus KM7. These results suggested that isomalto-oligosaccharides could be a potential prebiotic and symbiotic with certain lactobacilli strains on A. cerana gut microbiota.     

Neutrophil Elastase Alters the Murine Gut Microbiota Resulting in Enhanced Salmonella Colonization

The intestinal microbiota has been found to play a central role in the colonization of Salmonella enterica serovar Typhimurium in the gastrointestinal tract. In this study, we present a novel process through which Salmonella benefit from inflammatory induced changes in the microbiota in order to facilitate disease. We show that Salmonella infection in mice causes recruitment of neutrophils to the gut lumen, resulting in significant changes in the composition of the intestinal microbiota. This occurs through the production of the enzyme elastase by neutrophils. Administration of recombinant neutrophil elastase to infected animals under conditions that do not elicit neutrophil recruitment caused shifts in microbiota composition that favored Salmonella colonization, while inhibition of neutrophil elastase reduced colonization. This study reveals a new relationship between the microbiota and the host during infection.     

Comparative roles of IL-4, IL-13, and IL-4Ralpha in dendritic cell maturation and CD4+ Th2 cell function

IL-4 and IL-13 play key roles in Th2 immunity and asthma pathogenesis. Although the function of these cytokines is partially linked through their shared use of IL-4Ralpha for signaling, the interplay between these cytokines in the development of memory Th2 responses is not well delineated. In this investigation, we show that both IL-4 and IL-13 influence the maturation of dendritic cells (DC) in the lung and their ability to regulate secretion of IFN-gamma and Th2 cytokines by memory CD4(+) T cells. Cocultures of wild-type T cells with pulmonary DC from allergic, cytokine-deficient mice demonstrated that IL-4 enhanced the capacity of DC to stimulate T cell secretion of Th2 cytokines, whereas IL-13 enhanced the capacity of DC to suppress T cell secretion of IFN-gamma. Because IL-4Ralpha is critical for IL-4 and IL-13 signaling, we also determined how variants of IL-4Ralpha influenced immune cell function. T cells derived from allergic mice expressing a high-affinity IL-4Ralpha variant produced higher levels of IL-5 and IL-13 compared with T cells derived from allergic mice expressing a low-affinity IL-4Ralpha variant. Although DC expressing different IL-4Ralpha variants did not differ in their capacity to influence Th2 cytokine production, they varied in their capacity to inhibit IFN-gamma production by T cells. Thus, IL-4 and IL-13 differentially regulate DC function and the way these cells regulate T cells. The affinity of IL-4Ralpha also appears to be a determinant in the balance between Th2 and IFN-gamma responses and thus the severity of allergic disease.     

Western-style diet impedes colonization and clearance of Citrobacter rodentium

Western-style diet (WSD), which is high in fat and low in fiber, lacks nutrients to support gut microbiota. Consequently, WSD reduces microbiota density and promotes microbiota encroachment, potentially influencing colonization resistance, immune system readiness, and thus host defense against pathogenic bacteria. Here we examined the impact of WSD on infection and colitis in response to Citrobacter rodentium. We observed that, relative to mice consuming standard rodent grain-based chow (GBC), feeding WSD starkly altered the dynamics of Citrobacter infection, reducing initial colonization and inflammation but frequently resulting in persistent infection that associated with low-grade inflammation and insulin resistance. WSD’s reduction in initial Citrobacter virulence appeared to reflect that colons of GBC-fed mice contain microbiota metabolites, including short-chain fatty acids, especially acetate, that drive Citrobacter growth and virulence. Citrobacter persistence in WSD-fed mice reflected inability of resident microbiota to out-compete it from the gut lumen, likely reflecting the profound impacts of WSD on microbiota composition. These studies demonstrate potential of altering microbiota and their metabolites by diet to impact the course and consequence of infection following exposure to a gut pathogen.     

Fecal microbiota transplantation from young donor mice improves ovarian function in aged mice

Advanced maternal age is characterized by declines in the quantity and quality of oocytes in the ovaries, and the aging process is accompanied by changes in gut microbiota composition. However, little is known about the relationship between gut microbiota and ovarian aging. By using fecal microbiota transplantation (FMT) to transplant material from young (5-week-old) into aged (42-week-old) mice, we find that the composition of gut microbiota in FMT-treated mice presents a “younger-like phenotype” and an increase of commensal bacteria, such as Bifidobacterium and Ruminococcaceae. Moreover, the FMT-treated mice show increased anti-inflammatory cytokine IL-4 and decreased pro-inflammatory cytokine IFN-γ. Fertility tests for assessing ovarian function reveal that the first litter size of female FMT-treated mice is significantly higher than that of the non-FMT group. Morphology analysis demonstrates a dramatic decrease in follicle atresia and apoptosis as well as an increase in cellular proliferation in the ovaries of the FMT-treated mice. Our results also show that FMT improves the immune microenvironment in aged ovaries, with decreased macrophages and macrophage-derived multinucleated giant cells (MNGCs). These results suggest that FMT from young donors could be a good choice for delaying ovarian aging.