Intestinal Immunity Research Articles

Effects of Rosa roxburghii & edible fungus fermentation broth on immune response and gut microbiota in immunosuppressed mice

With the rise of probiotics fermentation in food industry, fermented foods have attracted worldwide attention. In this study, protective effects of Rosa roxburghii & edible fungus fermentation broth (REFB) on immune function and gut health in Cyclophosphamide induced immunosuppressed mice were investigated. Results showed that REFB could improve the immune organ index, and promote the proliferation and differentiation of splenic T lymphocytes. In addition, it attenuated intestinal mucosal damage and improved intestinal cellular immunity. REFB administration also up-regulated the expression of IL-4, INF-γ, TNF-α, T-bet and GATA-3 mRNA in small intestine. Furthermore, administration of REFB modulated gut microbiota composition and increased the relative abundance of beneficial genus, such as Bacteroides. It also increased the production of fecal short-chain fatty acids. These indicate that REFB has the potential to improve immunity, alleviate intestinal injury and regulate gut microbiota in immunosuppressed mice.

Effects of dietary Clostridium butyricum on the growth performance, digestion, and intestinal health of spotted sea bass (Lateolabrax maculatus).

Clostridium butyricum (CB) is known to promote growth, enhance immunity, promote digestion, and improve intestinal health. In this study, we investigated the effects of CB in the feed on growth performance, digestion, and intestinal health of juvenile spotted sea bass. To provide a theoretical basis for the development and application of CB in the feed of spotted sea bass, a total of 450 spotted sea bass with an initial body weight of (9.58 ± 0.05) g were randomly divided into six groups. Gradient levels with 0, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of CB (1×109 cfu/g) were supplemented into diets, designated as CC, CB1, CB2, CB3, CB4, and CB5, respectively. Each group was fed for 54 days. Our results suggest that dietary 0.2% and 0.3% of CB can significantly increase the weight gain (WG) and specific growth rate (SGR) of spotted sea bass. The addition of CB significantly increased intestinal amylase activity, intestinal villus length, intestinal villus width, and intestinal muscle thickness. Similarly, CB supplementation increased the expression of tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8). Sequence analysis of the bacterial 16S rDNA region showed that dietary CB altered the intestinal microbiota profile of juvenile spotted sea bass, increasing the dominant bacteria in the intestine and decreasing the harmful bacteria. Overall, dietary addition of CB can improve growth performance, enhance intestinal immunity, improve intestinal flora structure, and comprehensively improve the health of spotted sea bass.

Effects of Replacing Soybean Meal Protein with Chlorella vulgaris Powder on the Growth and Intestinal Health of Grass Carp (Ctenopharyngodon idella).

Chlorella vulgaris (C. vulgaris) powder is a novel non-grain single-cell protein with enormous potential to be a protein source. However, it is poorly studied in aquatic animals. The purpose of the present study was to explore the optimum replacement ratio of C. vulgaris powder and the influence of the substitution of soybean meal with C. vulgaris on grass carp (Ctenopharyngodon idella) in terms of growth performance, intestinal integrity and the microbial community. Five isonitrogenous and isolipidic diets were formulated by replacing 0% (SM, containing 30% soybean meal), 25% (X25), 50% (X50), 75% (X75) and 100% (X100) soybean meal with C. vulgaris. The feeding trial period lasted 8 weeks. At the end of the experimental trial, the X50 group showed higher FW, WGR and PER than the SM group (p < 0.05). The feed conversion ratio (FCR) of the X50 group was significantly lower than that of the SM group (p < 0.05). The X50 group showed the highest value of the goblet cell number, intestinal amylase and trypsin activities when compared with the SM group (p < 0.05). Replacing 50% soybean meal with C. vulgaris improved the intestinal barrier integrity, as evidenced by upregulating zo-1, zo-2 and occluding transcript (p < 0.05), and alleviated oxidative stress by an increased SOD enzymatic activity and transcript level, probably mediated through the Nrf2-keap1 signaling pathway (p < 0.05). Meanwhile, the X50 group enhanced intestinal immunity, as manifested by increased ACP and LZM activities (p < 0.05), and downregulated the tlr-4, tlr-7, tlr-8 and il-6 through the tlr pathway (p < 0.05). The functionally predicting pathways related to the nitrate respiration and nitrogen respiration were observably activated in the X50 group (p < 0.05). The X50 group improved the biological barrier, as manifested by increased Firmicutes and Rhodobacter (p < 0.05). In conclusion, dietary C. vulgaris powder could promote the growth performance of grass carp by restoring intestinal morphology, increasing digestive enzyme activities, improving antioxidant properties and immunity and optimizing the microflora structure. A C. vulgaris powder replacement of 50% soybean meal was recommended as feed for grass carp.

Cxxc finger protein 1 maintains homeostasis and function of intestinal group 3 innate lymphoid cells with aging.

Aging is accompanied by homeostatic and functional dysregulation of multiple immune cell subsets. Group 3 innate lymphoid cells (ILC3s) constitute a heterogeneous cell population that plays pivotal roles in intestinal immunity. In this study, we found that ILC3s in aged mice exhibited dysregulated homeostasis and function, leading to bacterial and fungal infection susceptibility. Moreover, our data revealed that the enrichment of the H3K4me3 modification in effector genes of aged gut CCR6+ ILC3s was specifically decreased compared to young mice counterparts. Disruption of Cxxc finger protein 1 (Cxxc1) activity, a key subunit of H3K4 methyltransferase, in ILC3s led to similar aging-related phenotypes. An integrated analysis revealed Kruppel-like factor 4 (Klf4) as a potential Cxxc1 target. Klf4 overexpression partially restored the differentiation and functional defects seen in both aged and Cxxc1-deficient intestinal CCR6+ ILC3s. Therefore, these data suggest that targeting intestinal ILC3s may provide strategies to protect against age-related infections.

MTORC2 acts as a gatekeeper for mTORC1 deficiency-mediated impairments in ILC3 development.

Group 3 innate lymphoid cells (ILC3s) are mediators of intestinal immunity and barrier function. Recent studies have investigated the role of the mammalian target of rapamycin complex (mTOR) in ILC3s, whereas the mTORC1-related mechanisms and crosstalk between mTORC1 and mTORC2 involved in regulating ILC3 homeostasis remain unknown. In this study, we found that mTORC1 but not mTORC2 was critical in ILC3 development, IL-22 production, and ILC3-mediated intestinal homeostasis. Single-cell RNA sequencing revealed that mTORC1 deficiency led to disruption of ILC3 heterogeneity, showing an increase in differentiation into ILC1-like phenotypes. Mechanistically, mTORC1 deficiency decreased the expression of NFIL3, which is a critical transcription factor responsible for ILC3 development. The activities of both mTORC1 and mTORC2 were increased in wild-type ILC3s after activation by IL-23, whereas inhibition of mTORC1 by Raptor deletion or rapamycin treatment resulted in increased mTORC2 activity. Previous studies have demonstrated that S6K, the main downstream target of mTORC1, can directly phosphorylate Rictor to dampen mTORC2 activity. Our data found that inhibition of mTORC1 activity by rapamycin reduced Rictor phosphorylation in ILC3s. Reversing the increased mTORC2 activity via heterozygous or homozygous knockout of Rictor in Raptor-deleted ILC3s resulted in severe ILC3 loss and complete susceptibility to intestinal infection in mice with mTORC1 deficiency (100% mortality). Thus, mTORC1 acts as a rheostat of ILC3 heterogeneity, and mTORC2 protects ILC3s from severe loss of cellsand immune activity against intestinal infection when mTORC1 activity is diminished.

Iron-rich Candida utilis improves intestinal health in weanling piglets.

This study aimed to investigate the effects of substituting inorganic iron in the diet of weanling piglets with iron-rich Candida utilis on gut morphology, immunity, barrier, and microbiota. Seventy-two healthy 28-day-old Duroc×Landrace×Yorkshire desexed male weanling piglets were randomly assigned to 2 groups (n=6), with 6 pens per group and 6 piglets in each pen. The control group was fed a basal diet containing ferrous sulfate (104mg kg-1 iron), while the experimental group was fed a basal diet supplemented with iron-rich C. utilis (104mg kg-1 iron). The results show that the growth performance of weanling piglets showed no significantly differences (P>0.05). Iron-rich C. utilis significantly elevated villus height and decreased crypt depth in the duodenum and jejunum (P<0.05). Additionally, there was a significant increase in SIgA content, a down-regulated of pro-inflammatory factors expression, and an up-regulated of anti-inflammatory factors expression in the jejunum and ileum of piglets fed iron-rich C. utilis (P<0.05). The mRNA expression levels of ZO-1, Claudin-1, Occludin, and Mucin2 in the jejunum were significantly increased by iron-rich C. utilis, and were significantly increased ZO-1 and Claudin-1 in the ileum (P<0.05). The colonic microbiota, however, was not significantly affected by iron-rich C. utilis (P>0.05). Iron-rich C. utilis improved intestinal morphology and structure, as well as intestinal immunity and intestinal barrier function.

Effects of fermented soybean meal substitution for fish meal on intestinal flora and intestinal health in pearl gentian grouper.

This study explored the role of replacing fish meal protein with fermented soybean meal (FSBM) protein on the growth performance and intestinal morphology, immunity, and microbiota of the pearl gentian grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂). Three isonitrogenous and isolipidic diets with increasing levels of FSBM (0%, 20% and 40%; referred to as FM, FSBM20 and FSBM40 diets, respectively) as a replacement for fish meal were selected for this study. The pearl gentian grouper were fed these diets for 10 weeks. The findings revealed that the growth of fish fed the FSBM diets (FSBM20 and FSBM40) were remarkably lower than the fish fed the FM diet. Pathological manifestations of intestinal inflammation, such as shortened intestinal mucosal folds and thickened lamina propria, were observed in the fish fed the FSBM diets. Moreover, the gene expression levels of IL1β, IL12, IL17, and TNFα were remarkably upregulated in fish fed the FSBM40 diet, in contrast to the gene expression levels of IL4, IL5, IL10, and TGFβ1, which were remarkably downregulated (p < 0.05). The FSBM diets significantly affected the stability of the fish gut microbiota. Photobacterium was the dominant phylum in all experimental groups, and the proportion of these bacteria gradually decreased with increasing FSBM substitution. The composition of intestinal flora at the genus level was not the same in the three experimental groups, with a richer composition of intestinal bacteria detected in the FSBM20 and FSBM40 groups (p < 0.05). The correlation between intestinal flora balance and immune gene expression revealed that only Photobacterium was negatively correlated with the above upregulated genes, while other bacteria were positively correlated with these pro-inflammatory factors (p < 0.05). Photobacterium was positively correlated with the above downregulated genes, while other bacteria were negatively correlated with these anti-inflammatory factors (p < 0.05). In conclusion, high levels of substitution of FSBM for fish meal causes intestinal inflammation in pearl gentian grouper. This is likely associated with changes to the intestinal flora. More attention should be paid to the negative role of dietary FSBM on intestinal flora.

Organic acids, microbiota, gut health and productive response in broilers chickens

Since the middle of the last century, the use of antibiotic growth promoters in feed has improved the performance of several food-producing animal species. However, bacterial resistance to these drugs threatens public health and has led to their prohibition in animal feed. This has increased enteric problems in broilers and consequently the use of antibiotics for therapeutic purposes. In this context, several alternatives to antibiotic growth promoters have been proposed, among them organic acids, which, according to their physical and chemical properties, modify the composition of the intestinal microbiota, whose metabolites, such as short-chain fatty acids, favor the intestinal morphology, physiology, integrity, and immunity, aspects that contribute to maintain the health of this organ and increase the bioavailability of nutrients and, ultimately, to improve the productive response of birds. This review describes the main characteristics of the organic acids commonly used in the poultry industry, their mechanisms of action and their effects, individually, in combinations of organic acids or with bioactive, on the microbiota, their metabolites, and how this affects the intestinal health and productive performance of broilers under different sanitary and environmental conditions, as well as factors that potentially interfere with the activity of organics acids.&#x0D;

NAD+ Precursors and Intestinal Inflammation: Therapeutic Insights Involving Gut Microbiota.

The oxidized form of nicotinamide adenine dinucleotide (NAD+) is a critical metabolite for living cells. NAD+ may act either as a cofactor for many cellular reactions as well as a coenzyme for different NAD+-consuming enzymes involved in the physiological homeostasis of different organs and systems. In mammals, NAD+ is synthesized from either tryptophan or other vitamin B3 intermediates that act as NAD+ precursors. Recent research suggests that NAD+ precursors play a crucial role in maintaining the integrity of the gut barrier. Indeed, its deficiency has been associated with enhanced gut inflammation and leakage, and dysbiosis. Conversely, NAD+-increasing therapies may confer protection against intestinal inflammation in experimental conditions and human patients, with accumulating evidence indicating that such favorable effects could be, at least in part, mediated by concomitant changes in the composition of intestinal microbiota. However, the mechanisms by which NAD+-based treatments affect the microbiota are still poorly understood. In this context, we have focused specifically on the impact of NAD+ deficiency on intestinal inflammation and dysbiosis in animal and human models. We have further explored the relationship between NAD+ and improved host intestinal metabolism and immunity and the composition of microbiota in vivo. Overall, this comprehensive review aims to provide a new perspective on the effect of NAD+-increasing strategies on host intestinal physiology.

Mechanism of congenital lymphocytes and intestinal immunity regulated by gut microbial metabolites via metabolite-sensing receptor Ffar2

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;&lt;strong&gt;Objective: &lt;/strong&gt;&lt;/strong&gt;The DSS was utilized to construct colitis model of mouse. The colitis mice were colonized with gut microbiota. The effects of gut microbial metabolites on colitis were studied. The mechanisms of gut microbial metabolites to improve intestinal immunity were also further explored. &lt;strong&gt;&lt;strong&gt;Methods: &lt;/strong&gt;&lt;/strong&gt;The male BALB/c mice were selected to construct colitis mouse model with DSS and colonized with gut microbiota. The content of short-chain fatty acids in intestinal metabolites of mice during modeling were detected with GC-MS. After the mice were sacrificed, the colon tissue was stained to observe the colitis in different groups of mice. The contents of IL-22 and IL-17 in colon tissue was determined with ELISA method. To study the mechanism of relieving colitis, qRT-PCR and western blotting were used to study the horizontal of Ffar2 gene and pSTAT3 and pAKT in colon tissue, respectively. The congenital lymphocytes were isolated and purified, and the migration ability of the congenital lymphocytes was examined by cell scratch plane migration test.&lt;strong&gt;&lt;strong&gt;&amp;nbsp;Results:&lt;/strong&gt;&lt;/strong&gt;&amp;nbsp;The colonization of the gut microbiota had significant effects on the contents of short-chain fatty acids in the intestinal metabolites of colitis mice, of which the effect on the content of acetic acid and butyric acid was more significant. The colonization of gut microbiota could effectively relieve colitis in mice and effectively promote the secretion of IL-22 in colon tissue. Studying the remission mechanism indicated that colonization of gut microbiota with colitis could effectively promote the expression of Ffar2 gene in colon tissue and increase the expression of pSTAT3 and pAKT protein. The migration ability of the lymphocyte was significantly upregulated in the model group compared with the other groups, demonstrating that DSS can effectively activate the lymphocyte; The migration of congenital lymphocyte in the experimental group was significantly alleviated than that in the model group, but it was up-regulated than that in the positive control group, and the colonic tissue of the positive control group&amp;nbsp;was similar to that of the normal group. &lt;strong&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;&lt;/strong&gt;The short-chain fatty acids in the intestinal flora metabolites can promote the gene expression of the metabolite-sensitive receptor Ffar2. The effective combination of short-chain fatty acids and Ffar2 receptors can promote the phosphorylation of STAT3 and AKT proteins, effectively promote the secretion of IL-22 in intestinal ILC3 cells, alleviate colitis in mice, and thereby improve their intestinal immune function.&lt;/p&gt;

Mechanism of congenital lymphocytes and intestinal immunity regulated by gut microbial metabolites via metabolite-sensing receptor Ffar2

&lt;p&gt;&lt;strong&gt;&lt;strong&gt;Objective: &lt;/strong&gt;&lt;/strong&gt;The DSS was utilized to construct colitis model of mouse. The colitis mice were colonized with gut microbiota. The effects of gut microbial metabolites on colitis were studied. The mechanisms of gut microbial metabolites to improve intestinal immunity were also further explored. &lt;strong&gt;&lt;strong&gt;Methods: &lt;/strong&gt;&lt;/strong&gt;The male BALB/c mice were selected to construct colitis mouse model with DSS and colonized with gut microbiota. The content of short-chain fatty acids in intestinal metabolites of mice during modeling were detected with GC-MS. After the mice were sacrificed, the colon tissue was stained to observe the colitis in different groups of mice. The contents of IL-22 and IL-17 in colon tissue was determined with ELISA method. To study the mechanism of relieving colitis, qRT-PCR and western blotting were used to study the horizontal of Ffar2 gene and pSTAT3 and pAKT in colon tissue, respectively. The congenital lymphocytes were isolated and purified, and the migration ability of the congenital lymphocytes was examined by cell scratch plane migration test.&lt;strong&gt;&lt;strong&gt;&amp;nbsp;Results:&lt;/strong&gt;&lt;/strong&gt;&amp;nbsp;The colonization of the gut microbiota had significant effects on the contents of short-chain fatty acids in the intestinal metabolites of colitis mice, of which the effect on the content of acetic acid and butyric acid was more significant. The colonization of gut microbiota could effectively relieve colitis in mice and effectively promote the secretion of IL-22 in colon tissue. Studying the remission mechanism indicated that colonization of gut microbiota with colitis could effectively promote the expression of Ffar2 gene in colon tissue and increase the expression of pSTAT3 and pAKT protein. The migration ability of the lymphocyte was significantly upregulated in the model group compared with the other groups, demonstrating that DSS can effectively activate the lymphocyte; The migration of congenital lymphocyte in the experimental group was significantly alleviated than that in the model group, but it was up-regulated than that in the positive control group, and the colonic tissue of the positive control group&amp;nbsp;was similar to that of the normal group. &lt;strong&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;&lt;/strong&gt;The short-chain fatty acids in the intestinal flora metabolites can promote the gene expression of the metabolite-sensitive receptor Ffar2. The effective combination of short-chain fatty acids and Ffar2 receptors can promote the phosphorylation of STAT3 and AKT proteins, effectively promote the secretion of IL-22 in intestinal ILC3 cells, alleviate colitis in mice, and thereby improve their intestinal immune function.&lt;/p&gt;

Trans-Golgi protein TVP23B regulates host-microbe interactions via Paneth cell homeostasis and Goblet cell glycosylation

A key feature in intestinal immunity is the dynamic intestinal barrier, which separates the host from resident and pathogenic microbiota through a mucus gel impregnated with antimicrobial peptides. Using a forward genetic screen, we have found a mutation in Tvp23b, which conferred susceptibility to chemically induced and infectious colitis. Trans-Golgi apparatus membrane protein TVP23 homolog B (TVP23B) is a transmembrane protein conserved from yeast to humans. We found that TVP23B controls the homeostasis of Paneth cells and function of goblet cells, leading to a decrease in antimicrobial peptides and more penetrable mucus layer. TVP23B binds with another Golgi protein, YIPF6, which is similarly critical for intestinal homeostasis. The Golgi proteomes of YIPF6 and TVP23B-deficient colonocytes have a common deficiency of several critical glycosylation enzymes. TVP23B is necessary for the formation of the sterile mucin layer of the intestine and its absence disturbs the balance of host and microbe in vivo.

NAMPT inhibition relieves intestinal inflammation by regulating macrophage activation in experimental necrotizing enterocolitis

Nicotinamide phosphoribosyl transferase (NAMPT) is associated with various NAD+ -consuming enzymatic reactions. The precise role in intestinal mucosal immunity in necrotizing enterocolitis (NEC) is not well defined. Here, we examined whether NAMPT inhibition by the highly specific inhibitor FK866 could alleviate intestinal inflammation during the pathogenesis of NEC. In the present study, we showed that NAMPT expression was upregulated in the human terminal ileum of human infants with NEC. FK866 administration attenuated M1 macrophage polarization and relieved the symptoms of experimental NEC pups. FK866 inhibited intercellular NAD+ levels, macrophage M1 polarization, and the expression of NAD+ -dependent enzymes, such as poly (ADP ribose) polymerase 1 (PARP1) and Sirt6. Consistently, the capacity of macrophages to phagocytose zymosan particles, as well as antibacterial activity, were impaired by FK866, whereas NMN supplementation to restore NAD+ levels reversed the changes in phagocytosis and antibacterial activity. In conclusion, FK866 reduced intestinal macrophage infiltration and skewed macrophage polarization, which is implicated in intestinal mucosal immunity, thereby promoting the survival of NEC pups.

Probiotic lactic acid bacteria alleviate pediatric IBD and remodel gut microbiota by modulating macrophage polarization and suppressing epithelial apoptosis.

The incidence of pediatric inflammatory bowel disease (PIBD) continues to rise. It was reported that the probiotic lactic acid bacteria Pediococcus pentosaceus (P. pentosaceus) can interfere with intestinal immunity, but it is still unknown whether it can alleviate PIBD and the concrete mechanism of immune regulation is unclear. For this study, 3-week-old juvenile mice were selected for modeling the development of PIBD. The mice treated with 2% DSS were randomly divided into two groups, which were given P. pentosaceus CECT8330 and equal amounts of solvent, respectively. The feces and intestinal tissue were collected for the mechanism exploration in vivo. THP-1 and NCM460 cells were used to investigate the effects of P. pentosaceus CECT8330 on macrophage polarization, epithelial cell apoptosis, and their crosstalk in vitro. P. pentosaceus CECT8330 obviously alleviated colitis symptoms of juvenile mice, including weight loss, colon length shortening, spleen swelling, and intestinal barrier function. Mechanistically, P. pentosaceus CECT8330 could inhibit intestinal epithelial apoptosis by suppressing the NF-κB signaling pathway. Meanwhile, it reprogramed macrophages from a pro-inflammatory M1 phenotype to an anti-inflammatory M2 phenotype, leading to a decreased secretion of IL-1β which contributes to the reduction in ROS production and epithelial apoptosis. Additionally, the 16S rRNA sequence analysis revealed that P. pentosaceus CECT8330 could recover the balance of gut microbiota, and a significantly increased content of Akkermansia muciniphila was particularly observed. P. pentosaceus CECT8330 shifts macrophage polarization toward an anti-inflammatory M2 phenotype. The decreased production of IL-1β leads to a reduction in ROS, NF-κB activation, and apoptosis in the intestinal epithelium, all of which help to repair the intestinal barrier and adjust gut microbiota in juvenile colitis mice.

Gasdermin D licenses MHCII induction to maintain food tolerance in small intestine

The intestinal epithelial cells (IECs) constitute the primary barrier between host cells and numerous foreign antigens; it is unclear how IECs induce the protective immunity against pathogens while maintaining the immune tolerance to food. Here, we found IECs accumulate a less recognized 13-kD N-terminal fragment of GSDMD that is cleaved by caspase-3/7 in response to dietary antigens. Unlike the 30-kD GSDMD cleavage fragment that executes pyroptosis, the IEC-accumulated GSDMD cleavage fragment translocates to the nucleus and induces the transcription of CIITA and MHCII molecules, which in turn induces the Tr1 cells in upper small intestine. Mice treated with a caspase-3/7 inhibitor, mice with GSDMD mutation resistant to caspase-3/7 cleavage, mice with MHCII deficiency in IECs, and mice with Tr1 deficiency all displayed a disrupted food tolerance phenotype. Our study supports that differential cleavage of GSDMD can be understood as a regulatory hub controlling immunity versus tolerance in the small intestine.

Sodium Humate-Derived Gut Microbiota Ameliorates Intestinal Dysfunction Induced by Salmonella Typhimurium in Mice.

Salmonella is a foodborne pathogen that is one of the main causes of gastroenteric disease in humans and animals. As a natural organic substance, sodium humate (HNa) possesses antibacterial, antidiarrheal, and anti-inflammatory properties. However, it is unclear whether the HNa and HNa-derived microbiota exert alleviative effects on Salmonella enterica serovar Typhimurium-induced enteritis. We found that treatment with HNa disrupted the cell wall of S. Typhimurium and decreased the virulence gene expression. Next, we explored the effect of HNa presupplementation on S. Typhimurium-induced murine enteritis. The results revealed that HNa ameliorated intestinal pathological damage. In addition, we observed that presupplementation with HNa enhanced intestinal barrier function via modulating gut microbiota, downregulating toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) and NOD-like receptor protein 3 (NLRP3) signaling pathways, regulating intestinal mucosal immunity, and enhancing tight junction protein expression. To further validate the effect of HNa-derived microbiota on S. Typhimurium-induced enteritis, we performed fecal microbiota transplantation and found that HNa-derived microbiota also alleviated S. Typhimurium-induced intestinal damage. It is noteworthy that both HNa and HNa-derived microbiota improved the liver injury caused by S. Typhimurium infection. Collectively, this is the first study to confirm that HNa could alleviate S. Typhimurium-induced enteritis in a gut microbiota-dependent manner. This study provides a new perspective on HNa as a potential drug to prevent and treat salmonellosis. IMPORTANCE Salmonella Typhimurium is an important zoonotic pathogen, widely distributed in nature. S. Typhimurium is one of the leading causes of foodborne illnesses worldwide, and more than 350,000 people died from Salmonella infection each year, which poses a substantial risk to public health and causes a considerable economic loss. Here, we found that the S. Typhimurium infection caused severe intestinal and liver damage. In addition, we first found that sodium humate (HNa) and HNa-derived gut microbiota can alleviate S. Typhimurium infection-induced intestinal damage. These findings extend the knowledge about the public health risk and pathogenic mechanisms of S. Typhimurium.

Genetic stabilization of attenuated oral vaccines against poliovirus types 1 and 3

Vaccination with Sabin, a live attenuated oral polio vaccine (OPV), results in robust intestinal and humoral immunity and has been key to controlling poliomyelitis. As with any RNA virus, OPV evolves rapidly to lose attenuating determinants critical to the reacquisition of virulence1–3 resulting in vaccine-derived, virulent poliovirus variants. Circulation of these variants within underimmunized populations leads to further evolution of circulating, vaccine-derived poliovirus with higher transmission capacity, representing a significant risk of polio re-emergence. A new type 2 OPV (nOPV2), with promising clinical data on genetic stability and immunogenicity, recently received authorization from the World Health Organization for use in response to circulating, vaccine-derived poliovirus outbreaks. Here we report the development of two additional live attenuated vaccine candidates against type 1 and 3 polioviruses. The candidates were generated by replacing the capsid coding region of nOPV2 with that from Sabin 1 or 3. These chimeric viruses show growth phenotypes similar to nOPV2 and immunogenicity comparable to their parental Sabin strains, but are more attenuated. Our experiments in mice and deep sequencing analysis confirmed that the candidates remain attenuated and preserve all the documented nOPV2 characteristics concerning genetic stability following accelerated virus evolution. Importantly, these vaccine candidates are highly immunogenic in mice as monovalent and multivalent formulations and may contribute to poliovirus eradication.

The role of flagellin F in Vibrio Parahaemolyticus-induced intestinal immunity and functional domain identification

The marine pathogen Vibrio parahaemolyticus has caused huge economic losses to aquaculture. Flagellin is a key bacterial virulence factor that induces an inflammatory response via activation of Toll-like receptor 5 (TLR5) signaling. Herein, to explore the inflammatory activity of V. parahaemolyticus flagellins (flaA, flaB, flaC, flaD, flaE, and flaF), we investigated their ability to induce apoptosis in a fish cell line. All six flagellins induced severe apoptosis. Moreover, treatment with V. parahaemolyticus flagellins increased TLR5 and myeloid differentiation factor 88 (MyD88) expression and the production of TNF-α and IL-8 significantly. This indicated that flagellins might induce a TLR5-meditated immune response via an MyD88-dependent pathway. FlaF exhibited the strongest immunostimulatory effect; therefore, the interaction between TLR5 and flaF was screened using the yeast two-hybrid system. A significant interaction between the two proteins was observed, indicating that flaF binds directly to TLR5. Finally, the amino acids that participate in the TLR5-flaF interaction were identified using molecular simulation, which indicated three binding sites. These results deepen our understanding of the immunogenic properties of flagellins from V. parahaemolyticus, which could be used for vaccine development in the future.

Lactobacillus gasseri LG08 and Leuconostoc mesenteroides LM58 exert preventive effect on the development of hyperuricemia by repairing antioxidant system and intestinal flora balance.

Currently, hyperuricemia has shown a surprisingly rising trend, which attracts widespread attention due to potentially major health risks. Considering the inevitable side effects of long-term medicine, probiotics are emerging as potential therapeutics due to their ability to improve uric acid metabolism and superior safety. In our study, two strains of probiotics, Lactobacillus gasseri LG08 (LG08) and Leuconostoc mesenteroides LM58 (LM58) isolated from kimchi were evaluated for the prebiotic properties in vitro and uric-lowering effects in vivo. Here, hyperuricemia animal model and 16S rRNA gene amplicons analysis were further studied to investigate whether these probiotics exert different effects in prevention and treatment. In vivo indicators and intestinal flora immunity revealed that both LG08 and LM58 significantly prevent the development and progression of hyperuricemia, repair the antioxidant system and maintain intestinal flora balance in healthy rats, especially LM58. After hyperuricemia was formed, although the effect of LG08 and LM58 could decrease the level of uric acid, the effect to reverse and repair antioxidant levels in the body was limited. In our study, these findings have important implications for hyperuricemia prevention and therapy, and provided more mechanistic insights into the effect of probiotics in hyperuricemia.

Intestinal fungi and antifungal secretory immunoglobulin A in Crohn's disease.

The human gastrointestinal tract harbors trillions of commensal microorganisms. Emerging evidence points to a possible link between intestinal fungal dysbiosis and antifungal mucosal immunity in inflammatory bowel disease, especially in Crohn's disease (CD). As a protective factor for the gut mucosa, secretory immunoglobulin A (SIgA) prevents bacteria from invading the intestinal epithelium and maintains a healthy microbiota community. In recent years, the roles of antifungal SIgA antibodies in mucosal immunity, including the regulation of intestinal immunity binding to hyphae-associated virulence factors, are becoming increasingly recognized. Here we review the current knowledge on intestinal fungal dysbiosis and antifungal mucosal immunity in healthy individuals and in patients with CD, discuss the factors governing antifungal SIgA responses in the intestinal mucosa in the latter group, and highlight potential antifungal vaccines targeting SIgA to prevent CD.