CD11b+ Peyer's patch dendritic cells secrete IL-6 and induce IgA secretion from naive B cells

Tamibarotene-Loaded Nanoemulsion Incorporating Toll-like Receptor 2/6 Agonist as an Intramuscular Adjuvant System Enhances Gastrointestinal Mucosal Immunity

Parenteral subunit vaccines typically elicit systemic humoral immune responses but often struggle to induce mucosal immunity. Herein, we developed a promising adjuvant system, TB/P2C-NE, a tamibarotene-loaded nanoemulsion incorporating the TLR2/6 agonist Pam2CSK4. Upon intramuscular vaccination, TB/P2C-NE promoted antigen-specific mucosal immune responses in the gastrointestinal tract, accompanied by systemic humoral and cellular response. Mechanistically, tamibarotene upregulated the intestinal homing molecule CCR9 on lymphocytes through dendritic cell modulation, while Pam2CSK4 increased IL-6 secretion at the injection sites, further amplifying CCR9 expression and lymphocyte activation and leading to enhanced lymphocyte homing to the intestinal mucosa and a subsequent boost in mucosal immunity. Notably, TB/P2C-NE induced long-term gastrointestinal mucosal responses, maintaining elevated sIgA levels for up to three months post-immunization, and also induced gastrointestinal mucosal immunity in combination with a polysaccharide conjugate antigen. Immunization with recombinant intimin using TB/P2C-NE as the adjuvant resulted in a robust protective effect against the EHEC O157:H7 challenge. In summary, TB/P2C-NE offers an adjuvant strategy potentially accelerating the development of vaccines targeting gastrointestinal infections.

Use of a transgenic mouse model for in vivo monitoring of corneal pathologies following Sulfur Mustard Exposure

PURPOSE

The dynamic course of sulfur mustard (SM)-induced ocular insult involves an acute phase, which may progress to a chronic phase or a quiescent period, followed by late pathology. Visualizing pathological corneal changes in vivo could enhance understanding of this process and aid treatment development.

METHODS

SM burn was induced in the right eyes of three transgenic mouse strains-expressing RFP under the VE-Cadherin promoter (blood vessels and hematopoietic cells), GFP under the keratin 15 promoter (limbal stem cells), and YFP under the Thy-1 promoter (mid-stromal nerve fibers, MSNFs)-by vapor exposure. Cell infiltration, neovascularization (NV), innervation loss, and stem cell (SC) depletion were monitored in vivo by stereomicroscopy for up to 8 weeks. Corneal whole-mounts were used to assess 360° structures, infiltrating cells, and subbasal nerve plexus (SNP) loss. Histology included H&E, Masson-Trichrome, and periodic acid-Schiff staining.

RESULTS

A 35-s exposure caused minor ocular insult with moderate SNP changes, corneal cell infiltration, and reversible SC loss, mostly resolving by 4 weeks. A 120-s exposure caused severe insult with NV, extensive MSNF and SNP loss, marked CD45+ and Iba1+ infiltration, and irreversible SC depletion. NV, stromal inflammation, edema, epithelial changes, and goblet cells were seen in histology and correlated with fluorescence imaging.

CONCLUSIONS

This study demonstrates the utility of transgenic mice as powerful models for studying SM-induced ocular injury and for developing novel therapeutic strategies.

Nanoparticles encapsulating antigenic peptides induce tolerogenic dendritic cells in situ for treating systemic lupus erythematosus

Using Tetrahedral framework nucleic acids, we combined antigenic peptides to create the "DART" vaccine: DNA framework-Antigenic peptide-RNA modification-Targeting aptamer coupling. Generating antigen-specific tolerogenic dendritic cells (tolDCs), for systemic lupus erythematosus (SLE) is a potential therapeutic strategy for addressing compromised autoimmune tolerance. However, simple antigenic peptides degrade easily, lack specificity for delivery to dendritic cells (DCs), and cannot transform DCs to tolDCs. Therefore, this study aims to employ DART to generate tolDCs and compare DART-treated DCs to tolDCs. DART improved peptide stability, specifically targeted DCs, induced tolDCs in situ, and showed promising outcomes in mitigating SLE symptoms in the MRL/lpr mouse model. DART effectively normalized the plasma cytokine levels, glomerulonephritis, and joint lesions in MRL/lpr mice. These findings highlight the potential of the DART vaccine to induce transformation of DCs to tolDCs and address SLE symptoms, suggesting novel therapeutic utility. These findings may advance vaccine design for various autoimmune diseases.

Lactococcus lactis as an Effective Mucosal Vaccination Carrier: a Systematic Literature Review

Lactococcus lactis has potential as a mucosal vaccine delivery system. L. lactis can express antigens from bacteria or viruses, which are tightly controlled using nisin. Although L. lactis-based vaccine shows great promise, no product is ready for human use. Several studies have been conducted to develop L. lactis-based vaccine, and the efficacy of these vaccines has been evaluated in many scientific articles. This paper aims to review key aspects of current knowledge on the promising characteristics of L. lactis and to suggest its implications for vaccine design. Articles were obtained online using inclusion and exclusion criteria through Harzing's Publish or Perish. The article assessment used the Joanna Briggs Institute critical appraisal checklist for quasi-experimental studies. The efficacy evaluation of 24 articles showed that L. lactis-based vaccine can induce IgA and IgG as humoral immune responses; T CD4, T CD8, and B cells as cellular immune responses; and various proinflammatory cytokines such as IFN-γ, TNF-α, IL-2, IL-4, IL-8, IL-10, IL-12, IL-17. L. lactis is suitable as a vector carrier for oral or nasal mucosal vaccines targeting bacterial and viral infections. The development of L. lactis as a vaccine delivery system is promising.

Effects of intranasal administration with a symbiotic strain of Bacillus velezensis NSV2 on nasal cavity mucosal barrier in lambs

The nasal mucosa is composed of multiple layers of barrier structures and is the first line of defense against infection by respiratory pathogenic microorganisms. A large number of commensal microorganisms are present in the nasal mucosa that mediate and regulate nasal mucosal barrier function. The objective of this research was to investigate the effects of commensal microorganisms on the nasal mucosal barrier. The results revealed that the strain of Bacillus velezensis (B. velezensis) NSV2 from the nasal cavity has good probiotic abilities to resist Pasteurella multocida, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium. Lambs were subsequently administered intranasally with B. velezensis NSV2 at 3, 12, 21, and 26 days old, respectively. For the microbial barrier, although B. velezensis NSV2 reduces the diversity of nasal microbiota, it significantly increased the relative abundance of beneficial bacteria in the nasal cavity, and reduced the abundance of potential pathogenic bacteria. For the mucus barrier, the number of goblet cells in the nasal mucosa significantly increased after B. velezensis NSV2 treatment. For the immune barrier, B. velezensis NSV2 also significantly increased the number of IgA+ B cells, CD3+ T cells and dendritic cells in the nasal mucosa, as well as the mRNA expression of interleukin (IL) 6, IL11, CCL2, and CCL20 (P < 0.05). The protein level of CCL20 also significantly raised in nasal washings (P < 0.05). Moreover, the heat-inactivated and culture products of B. velezensis NSV2 also drastically induced the expression of CCL20 in nasal mucosa explants (P < 0.05), but lower than that of the live bacteria. This study demonstrated that a symbiotic strain of B. velezensis NSV2 could improve the nasal mucosal barrier, and emphasized the important role of nasal symbiotic microbiota.

Role of cellular effectors in the induction and maintenance of IgA responses leading to protective immunity against enteric bacterial pathogens

The mucosal immune system is a critical first line of defense to infectious diseases, as many pathogens enter the body through mucosal surfaces, disrupting the balanced interactions between mucosal cells, secretory molecules, and microbiota in this challenging microenvironment. The mucosal immune system comprises of a complex and integrated network that includes the gut-associated lymphoid tissues (GALT). One of its primary responses to microbes is the secretion of IgA, whose role in the mucosa is vital for preventing pathogen colonization, invasion and spread. The mechanisms involved in these key responses include neutralization of pathogens, immune exclusion, immune modulation, and cross-protection. The generation and maintenance of high affinity IgA responses require a delicate balance of multiple components, including B and T cell interactions, innate cells, the cytokine milieu (e.g., IL-21, IL-10, TGF-β), and other factors essential for intestinal homeostasis, including the gut microbiota. In this review, we will discuss the main cellular components (e.g., T cells, innate lymphoid cells, dendritic cells) in the gut microenvironment as mediators of important effector responses and as critical players in supporting B cells in eliciting and maintaining IgA production, particularly in the context of enteric infections and vaccination in humans. Understanding the mechanisms of humoral and cellular components in protection could guide and accelerate the development of more effective mucosal vaccines and therapeutic interventions to efficiently combat mucosal infections.

Leukocyte dysfunction and reduced CTLA-4 expression are associated with perianal Crohn's disease

Although perianal Crohn's disease (PCD) is highly associated with the exacerbated inflammation, the molecular basis and immunological signature that distinguish patients who present a history of perianal lesions are still unclear. This paper aims to define immunological characteristics related to PCD. In this cross-sectional observational study, we enrolled 20 healthy controls and 39 CD patients. Blood samples were obtained for the detection of plasma cytokines and lipopolysaccharides (LPS). Peripheral blood mononuclear cells (PBMCs) were phenotyped by flow cytometry. Leukocytes were stimulated with LPS or anti-CD3/anti-CD28 antibodies. Our results show that CD patients had augmented plasma interleukin (IL)-6 and LPS. However, their PBMC was characterized by decreased IL-6 production, while patients with a history of PCD produced higher IL-6, IL-8, and interferon-γ, along with decreased tumor necrosis factor alpha (TNF). CD patients had augmented FoxP3 and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) regulatory markers, though the PCD subjects presented a significant reduction in CTLA-4 expression. CTLA-4 as well as IL-6 and TNF responses were able to distinguish the PCD patients from those who did not present perianal complications. In conclusion, IL-6, TNF, and CTLA-4 exhibit a distinct expression pattern in CD patients with a history of PCD, regardless of disease activity. These findings clarify some mechanisms involved in the development of the perianal manifestations and may have a great impact on the disease management.

Feeding with 4,4'-diaponeurosporene-producing Bacillus subtilis enhances the lactogenic immunity of sow

Specific antibodies produced sow by oral porcine epidemic diarrhea virus (PEDV) vaccines would transfer to newborn piglets via colostrum, and it is an effective strategy to prevent porcine epidemic diarrhea (PED). However, there is a lag in the development of corresponding vaccines due to the rapid mutation of PEDV, which could increase the difficulty of PED prevention and control in pig farms. Hence, congenital lactogenic immunity was assessed by feeding 4,4'-diaponeurosporene-producing Bacillus subtilis (B.S-Dia) to sow on the 80th day of gestation in order to protect newborn piglets from PEDV infection. Firstly, we found that the quantities of T lymphocytes and monocytes in the blood and colostrum after oral administration of B.S-Dia were significantly increased as observed by flow cytometry, whereas the proliferative activity of T lymphocytes in colostrum was also markedly increased. Furthermore, enzyme-linked immunosorbent assay (ELISA) results revealed that levels of TGF (Transforming growth factor) -β, Interleukin (IL) -6, lysozyme and lactoferrin were significantly increased. Finally, it was found in the piglets' challenge protection test that offspring pigs of the sows feeding B.S-Dia during pregnancy did not develop diarrhea symptoms and intestinal pathological changes at 48 h after infection with PEDV, and PEDV load in the jejunum and ileum was significantly reduced, but offspring pigs of the sows taking orally PBS during pregnancy developed pronounced diarrhea symptoms and extensive PEDV colonization was noted both in the jejunum and ileum. In summary, sow by oral administration of B.S-Dia substantially increased congenital lactogenic immunity, thereby preventing newborn piglets from being infected with PEDV.

Salmonella delivers H9N2 influenza virus antigens via a prokaryotic and eukaryotic dual-expression vector and elicits bivalent protection against avian influenza and fowl typhoid

The H9N2 avian influenza virus significantly affects the health of poultry and humans. We identified a prokaryotic and eukaryotic dual-expression vector system, pJHL270, that can provide simultaneous MHC class I and II stimulation of the host immune system, and we designed vaccine antigens by selecting the consensus HA1 sequence and M2e antigens from H9N2 virus circulating in South Korea from 2000 to 2021. The genes were cloned into the pJHL270 vector, and the cloned plasmid was delivered by a live-attenuated Salmonella Gallinarum (SG) strain. The immunity and protective efficacy of the SG-based H9N2 vaccine construct, JOL2922, against avian influenza and fowl typhoid (FT) were evaluated. The Ptrc and CMV promoters conferred antigen expression in prokaryotic and eukaryotic cells to induce balanced Th-1/Th-2 immunity. Chickens immunized with JOL2922 yielded high antigen-specific humoral and mucosal immune responses. qRT-PCR revealed that the strain generated polyfunctional IFN-γ and IL-4 secretion in immunized chickens. Furthermore, a FACS analysis showed increased CD3CD4+ and CD3CD8+ T-cell subpopulations following immunization. Peripheral Blood Mononuclear Cells (PBMCs) harvested from the immunized chickens significantly increased MHC class I and II expression, 3.5-fold and 2.5-fold increases, respectively. Serum collected from the immunized groups had an evident hemagglutinin inhibition titer of ≥6 log2. Immunization reduced the lung viral titer by 3.8-fold within 5 days post-infection. The strain also generated SG-specific humoral and cellular immune responses. The immunized birds all survived a virulent SG wild-type challenge. In addition, the bacterial burden was reduced by 2.7-fold and 2.1-fold in spleen and liver tissue, respectively, collected from immunized chickens. Our data indicate that an attenuated SG strain successfully delivered the dual-expression vector system and co-stimulated MHC class I and II antigen presentation pathways via exogenous and endogenous antigen presentation, thereby triggering a balanced Th-1/Th-2-based immune response and conferring effective protection against avian influenza and FT.

IgA-producing B cells in lung homeostasis and disease

Immunoglobulin A (IgA) is the most abundant Ig in mucosae where it plays key roles in host defense against pathogens and in mucosal immunoregulation. Whereas intense research has established the different roles of secretory IgA in the gut, its function has been much less studied in the lung. This review will first summarize the state-of-the-art knowledge on the distribution and phenotype of IgA⁺ B cells in the human lung in both homeostasis and disease. Second, it will analyze the studies looking at cellular and molecular mechanisms of homing and priming of IgA⁺ B cells in the lung, notably following immunization. Lastly, published data on observations related to IgA and IgA⁺ B cells in lung and airway disease such as asthma, cystic fibrosis, idiopathic pulmonary fibrosis, or chronic rhinosinusitis, will be discussed. Collectively it provides the state-of-the-art of our current understanding of the biology of IgA-producing cells in the airways and identifies gaps that future research should address in order to improve mucosal protection against lung infections and chronic inflammatory diseases.

Enhancement of IgA production by membrane vesicles derived from Bifidobacterium longum subsp. infantis

Immunoglobulin A (IgA) is involved in the maintenance of gut homeostasis. Although the oral administration of bifidobacteria increases the amount of fecal IgA, the effects of bifidobacteria on intestinal immunity remain unclear. We found and characterized membrane vesicles (MVs) derived from Bifidobacterium longum subsp. infantis toward host immune cells. Bifidobacterium infantis MVs consisted of a cytoplasmic membrane, and extracellular solute-binding protein (ESBP) was specifically detected. In the presence of B. infantis MVs or recombinant ESBP, RAW264 cells produced the pro-inflammatory cytokine IL-6. IgA was produced by Peyer's patches cells following the addition of B. infantis MVs. Therefore, ESBP of B. infantis MVs is involved in the production of IgA by acquired immune cells via the production of IL-6 by innate immune cells.

B cell responses to the gut microbiota

Most antibody produced by humans originates from mucosal B cell responses. The rules, mechanisms, and outcomes of this process are distinct from B cell responses to infection. Within the context of the intestine, we discuss the induction of follicular B cell responses by microbiota, the development and maintenance of mucosal antibody-secreting cells, and the unusual impacts of mucosal antibody on commensal bacteria. Much remains to be learned about the interplay between B cells and the microbiota, but past and present work hints at a complex, nuanced relationship that may be critical to the way the mammalian gut fosters a beneficial microbial ecosystem.

Fcα Receptor-1-Activated Monocytes Promote B Lymphocyte Migration and IgA Isotype Switching

Patients with inflammatory bowel disease (IBD) produce enhanced immunoglobulin A (IgA) against the microbiota compared to healthy individuals, which has been correlated with disease severity. Since IgA complexes can potently activate myeloid cells via the IgA receptor FcαRI (CD89), excessive IgA production may contribute to IBD pathology. However, the cellular mechanisms that contribute to dysregulated IgA production in IBD are poorly understood. Here, we demonstrate that intestinal FcαRI-expressing myeloid cells (i.e., monocytes and neutrophils) are in close contact with B lymphocytes in the lamina propria of IBD patients. Furthermore, stimulation of FcαRI-on monocytes triggered production of cytokines and chemokines that regulate B-cell differentiation and migration, including interleukin-6 (IL6), interleukin-10 (IL10), tumour necrosis factor-α (TNFα), a proliferation-inducing ligand (APRIL), and chemokine ligand-20 (CCL20). In vitro, these cytokines promoted IgA isotype switching in human B cells. Moreover, when naïve B lymphocytes were cultured in vitro in the presence of FcαRI-stimulated monocytes, enhanced IgA isotype switching was observed compared to B cells that were cultured with non-stimulated monocytes. Taken together, FcαRI-activated monocytes produced a cocktail of cytokines, as well as chemokines, that stimulated IgA switching in B cells, and close contact between B cells and myeloid cells was observed in the colons of IBD patients. As such, we hypothesize that, in IBD, IgA complexes activate myeloid cells, which in turn can result in excessive IgA production, likely contributing to disease pathology. Interrupting this loop may, therefore, represent a novel therapeutic strategy.

Bacteria-enabled oral delivery of a replicon-based mRNA vaccine candidate protects against ancestral and delta variant SARS-CoV-2

The ongoing severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) evolution has resulted in many variants, contributing to the striking drop in vaccine efficacy and necessitating the development of next-generation vaccines to tackle antigenic diversity. Herein we developed a multivalent Semliki Forest virus replicon-based mRNA vaccine targeting the receptor binding domain (RBD), heptad repeat domain (HR), membrane protein (M), and epitopes of non-structural protein 13 (nsp13) of SARS-CoV-2. The bacteria-mediated gene delivery offers the rapid production of large quantities of vaccine at a highly economical scale and notably allows needle-free mass vaccination. Favorable T-helper (Th) 1-dominated potent antibody and cellular immune responses were detected in the immunized mice. Further, immunization induced strong cross-protective neutralizing antibodies (NAbs) against the B.1.617.2 delta variant (clade G). We recorded a difference in induction of immunoglobulin (Ig) A response by the immunization route, with the oral route eliciting a strong mucosal secretory IgA (sIgA) response, which possibly has contributed to the enhanced protection conferred by oral immunization. Hamsters immunized orally were completely protected against viral replication in the lungs and the nasal cavity. Importantly, the vaccine protected the hamsters against SARS-CoV-2-induced pneumonia. The study provides proof-of-principle findings for the development of a feasible and efficacious oral mRNA vaccine against SARS-CoV-2 and its variants.

Oral mRNA Vaccines Against Infectious Diseases- A Bacterial Perspective [Invited]

The mRNA vaccines from Pfizer/BioNTech and Moderna were granted emergency approval in record time in the history of vaccinology and played an instrumental role in limiting the pandemic caused by SARS-CoV-2. The success of these vaccines resulted from over 3 decades of research from many scientists. However, the development of orally administrable mRNA vaccine development is surprisingly underexplored. Our group specializing in Salmonella-based vaccines explored the possibility of oral mRNA vaccine development. Oral delivery was made possible by the exploitation of the Semliki Forest viral replicon and Salmonella vehicle for transgene amplification and gene delivery, respectively. Herein we highlight the prospect of developing oral replicon-based mRNA vaccines against infectious diseases based on our recent primary studies on SARS-CoV-2. Further, we discuss the potential advantages and limitations of bacterial gene delivery.

Role of Lipoteichoic Acid from the Genus Apilactobacillus in Inducing a Strong IgA Response

Lactic acid bacterium-containing fermentates provide beneficial health effects by regulating the immune response. A naturally fermented vegetable beverage, a traditional Japanese food, reportedly provides health benefits; however, the beneficial function of its bacteria has not been clarified. Apilactobacillus kosoi is the predominant lactic acid bacterium in the beverage. Using murine Peyer's patch cells, we compared the immunoglobulin A (IgA)-inducing activity of A. kosoi 10H^T to those of 29 other species of lactic acid bacteria and found that species belonging to the genus Apilactobacillus (A. kosoi 10H^T, A. apinorum JCM30765^T, and A. kunkeei JCM16173^T) possessed significantly higher activity than the others. Thereafter, lipoteichoic acids (LTAs), important immunostimulatory molecules of Gram-positive bacteria, were purified from the three Apilactobacillus species, and their IgA-inducing activity was compared to those of LTAs from Lactiplantibacillus plantarum JCM1149^T and a probiotic strain, Lacticaseibacillus rhamnosus GG. The results revealed that LTAs from Apilactobacillus species had significantly higher activity than others. We also compared the LTA structure of A. kosoi 10H^T with that of L. plantarum JCM1149^T and L. rhamnosus GG. Although d-alanine or both d-alanine and carbohydrate residues were substituents of free hydroxyl groups in the polyglycerol phosphate structure in LTAs from strains JCM1149^T and GG, d-alanine residues were not found in LTA from strain 10H^T by ¹H nuclear magnetic resonance (NMR) analysis. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis of the glycolipid structure of LTA revealed that LTA from strain 10H^T contained dihexosyl glycerol, whereas trihexosyl glycerol was detected in LTAs from other strains. These structural differences may be related to differences in IgA-inducing activity. IMPORTANCE The components of lactic acid bacteria that exert immunostimulatory effects are of increasing interest for therapeutic and prophylactic options, such as alternatives to antibiotics, cognitive enhancements, and vaccine adjuvants. LTAs act as immunostimulatory molecules in the host innate immune system by interacting with pattern recognition receptors. However, as LTA structures differ among species, detailed knowledge of the structure-function relationship for immunostimulatory effects is required. Comparisons of the IgA-inducing activity of LTAs have demonstrated that LTAs from the genus Apilactobacillus possess distinctive activities to stimulate mucosal immunity. The first analysis of the LTA structure from the genus Apilactobacillus suggests that it differs from structures of LTAs of related species of lactic acid bacteria. This knowledge is expected to aid in the development of functional foods containing lactic acid bacteria and pharmaceutical applications of immunostimulatory molecules from lactic acid bacteria.

The Microbiota-Gut-Brain Axis and Epilepsy

Honoured as the second genome in humans, the gut microbiota is involved in a constellation of physiological and pathological processes, including those related to the central nervous system. The communication between the gut microbiota and the brain is realized by a complex bidirectional connection, known as the "microbiota-gut-brain axis", via neuroendocrine, immunological, and direct neural mechanisms. Recent studies indicate that gut dysfunction/dysbiosis is presumably involved in the pathogenesis of and susceptibility to epilepsy. In addition, the reconstruction of the intestinal microbiome through, for example, faecal microbiota transplantation, probiotic intervention, and a ketogenic diet, has exhibited beneficial effects on drug-resistant epilepsy. The purposes of this review are to provide a brief overview of the microbiota-gut-brain axis and to synthesize what is known about the involvement of the gut microbiota in the pathogenesis and treatment of epilepsy, to bring new insight into the pathophysiology of epilepsy and to present a preliminary discussion of novel therapeutic options for epilepsy based on the gut microbiota.

Mechanisms underlying enhanced IgA production in Peyer's patch cells by membrane vesicles derived from Lactobacillus sakei

We analyzed the mechanisms underlying enhanced IgA production in the cells of Peyer's patch cells via membrane vesicles derived from Lactobacillus sakei subsp. sakei NBRC 15893. Depletion of CD11c+ cells from Peyer's patch cells suppressed the enhanced IgA production mediated by membrane vesicles. Meanwhile, the stimulation of bone-marrow-derived dendritic cells with membrane vesicles increased gene expression of inducible nitric oxide synthase, retinaldehyde dehydrogenase 2, and several inflammatory cytokines. The production of nitric oxide and interleukin (IL)-6 by membrane vesicle stimulation was induced via Toll-like receptor 2 on bone marrow-derived dendritic cells. Inhibition of inducible nitric oxide synthase and retinaldehyde dehydrogenase 2, as well as the neutralization of IL-6 in Peyer's patch cells, suppressed the enhanced IgA production by membrane vesicle stimulation. Hence, nitric oxide, retinoic acid, and IL-6 induced by membrane vesicles play crucial roles in the enhanced IgA production elicited by membrane vesicles in Peyer's patch cells.

Role of IL-6 in dendritic cell functions

Dendritic cells (DCs) are efficient antigen-presenting cells that serve as a link between the innate and adaptive immune systems. These cells are broadly involved in cellular and humoral immune responses by presenting antigens to initiate T cell reactions, cytokine and chemokine secretion, T cell differentiation and expansion, B cell activation and regulation, and the mediation of immune tolerance. The functions of DCs depend on their activation status, which is defined by the stages of maturation, phenotype differentiation, and migration ability, among other factors. IL-6 is a soluble mediator mainly produced by a variety of immune cells, including DCs, that exerts pleiotropic effects on immune and inflammatory responses through interaction with specific receptors expressed on the surface of target cells. Here, we review the role of IL-6, when generated in an inflammatory context or as derived from DCs, in modulating the biologic function and activation status of DCs and emphasize the importance of searching for novel strategies to target the IL-6/IL-6 signaling pathway as a means to diminish the inflammatory activity of DCs in immune response or to prime the immunogenic activity of DCs in immunosuppressive conditions.

Clostridium butyricum enhances colonization resistance against Clostridioides difficile by metabolic and immune modulation

Clostridioides difficile infection (CDI) represents the leading cause of nosocomial diarrhea worldwide and is associated with gut dysbiosis and intestinal damage. Clostridium butyricum MIYAIRI 588 (CBM 588) contributes significantly to reduce epithelial damage. However, the impacts of CBM 588 on antibacterial therapy for CDI are not clear. Here we show that CBM 588 enhanced the antibacterial activity of fidaxomicin against C. difficile and negatively modulated gut succinate levels to prevent C. difficile proliferation and downregulate tumor necrosis factor-α (TNF-α) producing macrophages in the colon lumina propria (cLP), resulting in a significant decrease in colon epithelial damage. Additionally, CBM 588 upregulated T cell-dependent pathogen specific immunoglobulin A (IgA) via interleukin (IL)-17A producing CD4⁺ cells and plasma B cells in the cLP, and Th17 cells in the cLP enhanced the gut epithelial barrier function. IL-17A and succinic acid modulations with CBM 588 enhance gut colonization resistance to C. difficile and protect the colon tissue from CDI.

HMGB1 promotes CXCL12-dependent egress of murine B cells from Peyer's patches in homeostasis

High mobility group box-1 protein (HMGB1) is an alarmin that, once released, promotes inflammatory responses, alone and as a complex with the chemokine CXCL12. Here, we report that the HMGB1-CXCL12 complex plays an essential role also in homeostasis by controlling the migration of B lymphocytes. We show that extracellular HMGB1 is critical for the CXCL12-dependent egress of B cells from the Peyer's patches (PP). This promigratory function of the complex was restricted to the PPs, since HMGB1 was not required for B-cell migratory processes in other locations. Accordingly, we detected higher constitutive levels of the HMGB1-CXCL12 complex in PPs than in other lymphoid organs. HMGB1-CXCL12 in vivo inhibition was associated with a reduced basal IgA production in the gut. Collectively, our results demonstrate a role for the HMGB1-CXCL12 complex in orchestrating B-cell trafficking in homeostasis, and provide a novel target to control lymphocyte migration in mucosal immunity.

In search of biomarkers for leprosy by unraveling the host immune response to Mycobacterium leprae

Mycobacterium leprae, the causative agent of leprosy, is still actively transmitted in endemic areas reflected by the fairly stable number of new cases detected each year. Recognizing the signs and symptoms of leprosy is challenging, especially at an early stage. Improved diagnostic tools, based on sensitive and specific biomarkers, that facilitate diagnosis of leprosy are therefore urgently needed. In this review, we address the challenges that leprosy biomarker research is facing by reviewing cell types reported to be involved in host immunity to M leprae. These cell types can be associated with different possible fates of M leprae infection being either protective immunity, or pathogenic immune responses inducing nerve damage. Unraveling these responses will facilitate the search for biomarkers. Implications for further studies to disentangle the complex interplay between host responses that lead to leprosy disease are discussed, providing leads for the identification of new biomarkers to improve leprosy diagnostics.

Increasing of SIgA serum levels may reflect subclinical intestinal involvement in non-radiographic axial and peripheral spondyloarthritis

OBJECTIVE

The evidence shows that previous infection with enteric pathogens is a requirement to develop pSpA. Based on our previous results, variances on regulation of SIgA might influence SpA activity; thus, the aim of this study was to correlate the levels of SIgA, IgA against some enteric bacteria, and IL-17, IL-21, and IL-6 with clinical features in a group of SpA patients.

METHODS

Twenty-six pSpA, 20 nr-axSpA, 60 healthy volunteers (HV), and 34 patients with inflammatory bowel diseases (IBD) were included. All subjects were assessed to measure SIgA, total and specific IgA for enteric bacteria, and IL-17, IL-21, and IL-6 levels and clinical variables. For SpA patients, the diagnosis was verified 5 years after first evaluation to assess the risk of developing r-axSpA.

RESULTS

SIgA levels were significantly higher in SpA patients than in HV and IBD (p < 0.0001 and p = 0.047, respectively). However, no differences for SIgA neither total IgA were found among the SpA subtypes (p = 0.624). Only IL-6 was higher in SpA than HV (p = 0.013). An inverse correlation was demonstrated for SIgA and BASFI (r: - 0.45; p = 0.003), BASDAI (r: - 0.39; p = 0.0123), ASDAS-CRP (r: - 0.37; p = 0.014), and ASDAS-ESR (r: - 0.45; p = 0.0021). There was no evidence of risk of developing r-axSpA in patients who previously showed high levels of serum antibodies.

CONCLUSION

The results show that pSpA as well as nr-axSpA share a similar SIgA-intestinal involvement independently of a previous infection. This suggests that serum SIgA increases are evidence of subclinical intestinal compromise which could have influence on disease activity but not in this progression. Key Point • The levels of SIgA, IgA against some enteric bacteria, and IL-17, IL-21, and IL-6 are correlated with clinical features in a group of SpA patients.

Probiotic Supplementation During the Perinatal and Infant Period: Effects on Gut Dysbiosis and Disease

The perinatal period is crucial to the establishment of lifelong gut microbiota. The abundance and composition of microbiota can be altered by several factors such as preterm delivery, formula feeding, infections, antibiotic treatment, and lifestyle during pregnancy. Gut dysbiosis affects the development of innate and adaptive immune responses and resistance to pathogens, promoting atopic diseases, food sensitization, and infections such as necrotizing enterocolitis (NEC). Recent studies have indicated that the gut microbiota imbalance can be restored after a single or multi-strain probiotic supplementation, especially mixtures of Lactobacillus and Bifidobacterium strains. Following the systematic search methodology, the current review addresses the importance of probiotics as a preventive or therapeutic tool for dysbiosis produced during the perinatal and infant period. We also discuss the safety of the use of probiotics in pregnant women, preterm neonates, or infants for the treatment of atopic diseases and infections.

Interleukin (IL)-21 Promotes the Differentiation of IgA-Producing Plasma Cells in Porcine Peyer's Patches via the JAK-STAT Signaling Pathway

Secretory IgA is critical to prevent the invasion of pathogens via mucosa. However, the key factors and the mechanisms of IgA generation in the porcine gut are not well-understood. In this study, a panel of factors, including BAFF, APRIL, CD40L, TGF-β1, IL-6, IL-10, IL-17A, and IL-21, were employed to stimulate IgM⁺ B lymphocytes from porcine ileum Peyer's patches. The results showed that IL-21 significantly upregulated IgA production of B cells and facilitated cell proliferation and differentiation of antibody-secreting cells. In addition, three transcripts in porcine IgA class switch recombination (CSR), germ-line transcript α, post-switch transcript α, and circle transcript α, were first amplified by (nest-)PCR and sequenced. All these key indicators of IgA CSR were upregulated by IL-21 treatment. Furthermore, we found that IL-21 predominantly activated JAK1, STAT1, and STAT3 proteins and confirmed that the JAK-STAT signaling pathway was involved in porcine IgA CSR. Thus, IL-21 plays an important role in the proliferation and differentiation of IgA-secreting cells in porcine Peyer's patches through the JAK-STAT signaling pathway. These findings provide insights into the mucosal vaccine design by regulation of IL-21 for the prevention and control of enteric pathogens in the pig industry.

Induction of Oral Tolerance by Pepsin-Digested Gliadin Retaining T Cell Reactivity in a Mouse Model of Wheat Allergy

BACKGROUND

Wheat is known as the most widely consumed food all over the world. Although many types of wheat allergy have been recognized, their treatment still has a long way to go due to the complex pathogenesis. Oral immunotherapy (OIT) is under investigation for the treatment of wheat allergies. Previous studies have demonstrated that OIT using intact wheat allergens can induce tolerance, but is accompanied by a high risk of anaphylactic reactions.

OBJECTIVES

Our objective was to prepare modified wheat allergens with hypoallergenic and tolerance-inducing properties to reduce adverse effects during immunotherapy.

METHODS

Wheat gliadin was degraded by hydrolysis with pepsin and trypsin, and then the hydrolysate was deamidated with hydrochloric acid. The IgE-binding capacity and T cell reactivity of the degraded gliadins were evaluated in vitro. Pepsin-digested gliadin (peptic-GLI) was applied in a mouse model to investigate whether it would induce oral tolerance.

RESULTS

Degradation with pepsin decreased IgE-binding capacity and maintained T cell reactivity. Oral administration of peptic-GLI to mice before sensitization and challenge with gliadin could significantly suppress the production of IgE, IgG1, and type 2 T helper cytokines. Moreover, the development of anaphylactic reactions and allergic responses of the small intestine induced by gliadin challenge were inhibited by oral administration of peptic-GLI.

CONCLUSIONS

The findings of this study indicate that peptic-GLI with low allergenicity and potential for tolerance induction may become useful in wheat immunotherapy with less adverse effects.

Distinct roles for Peyer's patch B cells for induction of antigen-specific IgA antibody responses in mice administered oral recombinant Salmonella

Our previous study demonstrated an indispensable role of Peyer's patches (PPs) for the induction of antigen-specific secretory (S)IgA antibody responses after oral immunization with recombinant Salmonella expressing fragment C of tetanus toxin (rSalmonella-Tox C). In this study, we defined the PP lymphoid structures and immune cells required for the induction of mucosal SIgA antibody responses. Adoptive transfer of mononuclear cells (MNCs) from PPs into PP-deficient (PP-null) mice failed to elicit tetanus toxoid (TT)-specific mucosal immunity. However, when the same PP MNCs were transferred into lethally irradiated PP-normal recipient mice, PP MNCs preferentially emigrated to recipient PPs, leading to PP lymphoid structures and TT-specific SIgA antibody responses. Significantly reduced numbers of TT-specific IgA antibody-forming cells were detected in the mesenteric lymph nodes (MLNs) and intestinal lamina propria of mice when surface expression of the sphingosine 1-phosphate receptor on lymphocytes was inhibited by its agonist FTY720. However, FTY720 treatment did not alter dendritic cell migration or Salmonella dissemination into these tissues. When rSalmonella-Tox C-stimulated CD4+ T cells isolated from PPs, MLNs and the spleen were co-cultured with B cells from these tissues, significantly increased levels of TT-specific IgA antibody responses were exclusively induced in cultures containing PP B cells. Furthermore, surface IgA+ PP B cells produced TT-specific IgA antibody responses in vitro. These findings suggest that PP lymphoid structures and surface IgA+ PP B cells are essential elements for the induction of antigen-specific intestinal SIgA antibody responses to oral Salmonella.

Specific microbiota enhances intestinal IgA levels by inducing TGF-β in T follicular helper cells of Peyer's patches in mice

In humans and mice, mucosal immune responses are dominated by IgA antibodies and the cytokine TGF-β, suppressing unwanted immune reactions but also targeting Ig class switching to IgA. It had been suggested that eosinophils promote the generation and maintenance of mucosal IgA-expressing plasma cells. Here, we demonstrate that not eosinophils, but specific bacteria determine mucosal IgA production. Co-housing of eosinophil-deficient mice with mice having high intestinal IgA levels, as well as the intentional microbiota transfer induces TGF-β expression in intestinal T follicular helper cells, thereby promoting IgA class switching in Peyer's patches, enhancing IgA⁺ plasma cell numbers in the small intestinal lamina propria and levels of mucosal IgA. We show that bacteria highly enriched for the genus Anaeroplasma are sufficient to induce these changes and enhance IgA levels when adoptively transferred. Thus, specific members of the intestinal microbiota and not the microbiota as such regulate gut homeostasis, by promoting the expression of immune-regulatory TGF-β and of mucosal IgA.

Regulation of IgA Production by Intestinal Dendritic Cells and Related Cells

The intestinal mucosa is a physiological barrier for most microbes, including both commensal bacteria and invading pathogens. Under homeostatic conditions, immunoglobulin A (IgA) is the major immunoglobulin isotype in the intestinal mucosa. Microbes stimulate the production of IgA, which controls bacterial translocation and neutralizes bacterial toxins at the intestinal mucosal surface. In the intestinal mucosa, dendritic cells (DCs), specialized antigen-presenting cells, regulate both T-cell-dependent (TD) and -independent (TI) immune responses. The intestinal DCs are a heterogeneous population that includes unique subsets that induce IgA synthesis in B cells. The characteristics of intestinal DCs are strongly influenced by the microenvironment, including the presence of commensal bacterial metabolites and epithelial cell-derived soluble factors. In this review, we summarize the ontogeny, classification, and function of intestinal DCs and how the intestinal microenvironment conditions DCs and their precursors to become the mucosal phenotype, in particular to regulate IgA production, after they arrive at the intestine. Understanding the mechanism of IgA synthesis could provide insights for designing effective mucosal vaccines.

Microbiota Sensing by Mincle-Syk Axis in Dendritic Cells Regulates Interleukin-17 and -22 Production and Promotes Intestinal Barrier Integrity

Production of interleukin-17 (IL-17) and IL-22 by T helper 17 (Th17) cells and group 3 innate lymphoid cells (ILC3s) in response to the gut microbiota ensures maintenance of intestinal barrier function. Here, we examined the mechanisms whereby the immune system detects microbiota in the steady state. A Syk-kinase-coupled signaling pathway in dendritic cells (DCs) was critical for commensal-dependent production of IL-17 and IL-22 by CD4+ T cells. The Syk-coupled C-type lectin receptor Mincle detected mucosal-resident commensals in the Peyer's patches (PPs), triggered IL-6 and IL-23p19 expression, and thereby regulated function of intestinal Th17- and IL-17-secreting ILCs. Mice deficient in Mincle or with selective depletion of Syk in CD11c+ cells had impaired production of intestinal RegIIIγ and IgA and increased systemic translocation of gut microbiota. Consequently, Mincle deficiency led to liver inflammation and deregulated lipid metabolism. Thus, sensing of commensals by Mincle and Syk signaling in CD11c+ cells reinforces intestinal immune barrier and promotes host-microbiota mutualism, preventing systemic inflammation.

A comprehensive understanding of the gut mucosal immune system in allergic inflammation

Despite its direct exposure to huge amounts of microorganisms and foreign and dietary antigens, the gut mucosa maintains intestinal homeostasis by utilizing the mucosal immune system. The gut mucosal immune system protects the host from the invasion of infectious pathogens and eliminates harmful non-self antigens, but it allows the cohabitation of commensal bacteria in the gut and the entry of dietary non-self antigens into the body via the mucosal surface. These physiological and immunological activities are regulated by the ingenious gut mucosal immune network, comprising such features as gut-associated lymphoid tissue, mucosal immune cells, cytokines, chemokines, antimicrobial peptides, secretory IgA, and commensal bacteria. The gut mucosal immune network keeps a fine tuned balance between active immunity (against pathogens and harmful non-self antigens) and immune tolerance (to commensal microbiota and dietary antigens), thus maintaining intestinal healthy homeostasis. Disruption of gut homeostasis results in persistent or severe gastrointestinal infection, inflammatory bowel disease, or allergic inflammation. In this review, we comprehensively introduce current knowledge of the gut mucosal immune system, focusing on its interaction with allergic inflammation.

Mesenteric CD103+DCs Initiate Switched Coxsackievirus B3 VP1-Specific IgA Response to Intranasal Chitosan-DNA Vaccine Through Secreting BAFF/IL-6 and Promoting Th17/Tfh Differentiation

Intranasal chitosan-formulated DNA vaccination promotes IgA secretion in the intestine. However, the mechanism whereby chitosan-DNA skews IgA class switch recombination (CSR) of B cells in the Gut-associated lymph tissue (GALT) is not fully resolved. In this study, we investigated the effects of nasally administered chitosan-DNA (pcDNA3.1-VP1 plasmid encoding VP1 capsid protein of Coxsackievirus B3) on IgA production, DC activation and Tfh/Th17 response in the intestine. Compared to DNA immunization, intranasal chitosan-DNA vaccination induced antigen-specific IgA production in feces, a pronounced switching of antigen-specific IgA⁺ plasmablast B cells in the mesenteric lymph nodes (MLNs) and an enhanced expression of post-recombination Iα-CH transcripts/IgA germline transcript (αGT) as well as activation-induced cytidine deaminase (AID) in MLN B cells. MLN Tfh frequency was markedly enhanced by chitosan-DNA, and was associated with VP1-specific IgA titer. 24 h after immunization, intranasal chitosan-DNA induced a recruitment of CD103⁺DCs into the MLN that paralleled a selective loss of CD103⁺DCs in the lamina propria (LP). In vivo activated MLN-derived CD103⁺DCs produced high levels of IL-6 and BAFF in response to chitosan-DNA, which up-regulated transmembrane activator and CAML interactor (TACI) expression on MLN B cells. Upon co-culture with IgM⁺B in the presence of chitosan-DNA, MLN CD103⁺DCs induced IgA production in a T-dependent manner; and this IgA-promoting effect of CD103⁺DC was blocked by targeting TACI and, to a lower extent, by blocking IL-6. MLN CD103⁺DCs displayed an enhanced capacity to induce an enhanced CD4⁺Th17 response in vivo and in vitro, and IL-17A deficient mice had a pronounced reduction of specific intestinal IgA following immunization. Taken together, mesenteric CD103⁺DCs are indispensable for the adjuvant activity of chitosan in enhancing DNA vaccine-specific IgA switching in gut through activating BAFF-TACI and IL-6-IL-6R signaling, and through inducing Th17/Tfh differentiation in the MLN.

Effect of feed supplementation with zinc glycine chelate and zinc sulfate on cytokine and immunoglobulin gene expression profiles in chicken intestinal tissue

The aim of the study was to evaluate the effect of inorganic and organic forms of Zn on the expression of cytokines (IL-2, TNF-α, IFN-γ, IL-12, IL-17, IL-4, IL-10, and TGF-β) and immunoglobulins (IgA and IgG) in the tissues of the small intestine (jejunum and ileum) of broiler chickens. In the experiment, 90 broiler chickens were divided into 4 experimental groups and a control group, with 18 birds each. The birds received Zn supplements in inorganic form with and without phytase (ZnSO4 and ZnSO4 + F), and in organic form with glycine, with and without phytase (Zn-Gly and Zn-Gly + F). The total rearing period was 42 days. Quantitative real-time (RT)-PCR was used to measure the expression of the cytokines and immunoglobulins. The differences between the results obtained for the control and experimental groups, between the groups receiving ZnSO4 and Zn-Gly, and between groups ZnSO4-F and Zn-Gly-F were analyzed statistically. High relative expression of IL-2 was observed for the chickens in the groups receiving ZnSO4-F, Zn-Gly, and Zn-Gly-F on d 42 in comparison to the control group. High relative expression of TNF-α, IL-12, and IL-17 was noted in the group that received ZnSO4 + F. High expression of IgG, IgA, IL-4, TGF-β, and IL-10 was noted in the groups of chickens that received feed supplemented with Zn-Gly and Zn-Gly + F chelates on d 42 of the study in comparison to the control group. In conclusion, supplementation with Zn-Gly chelates can ensure Th1 and Th2 balance during the immune response in the gut-associated lymphoid tissue (GALT), and, by increasing IgA and IgG expression, also can stimulate potentiation of the immune response involved in passive protection of the body from infection. In contrast, the use of inorganic forms of Zn, in the form of sulfates, can induce local inflammatory processes in the intestines, which, in the case of long-term supplementation, lead to the development of infections.

Orally administered heat-killed Lactobacillus paracasei MCC1849 enhances antigen-specific IgA secretion and induces follicular helper T cells in mice

Antigen-specific immunoglobulin (Ig) A plays a major role in host defense against infections in gut mucosal tissue. Follicular helper T (Tfh) cells are located in germinal centers and promote IgA production via interactions with germinal center B cells. Several studies have demonstrated that some lactic acid bacteria (LAB) strains activate the host’s acquired immune system, inducing IgA secretion in the intestine. However, the precise molecular mechanisms underlying the effects of LAB on IgA production and Tfh cells are not fully resolved. Lactobacillus paracasei MCC1849 is a probiotic strain isolated from the intestine of a healthy adult. In this study, we investigated the effects of orally administered heat-killed MCC1849 on IgA production in the intestine and on Tfh cell induction in vivo. We found that orally administered MCC1849 induced antigen-specific IgA production in the small intestine, serum and lungs. We also observed that MCC1849 increased the proportion of IgA⁺ B cells and Tfh cells in Peyer’s patches (PPs). In addition, MCC1849 increased the gene expression of IL-12p40, IL-10, IL-21, STAT4 and Bcl-6 associated with Tfh cell differentiation. These results suggest that orally administered MCC1849 enhances antigen-specific IgA production and likely affects Tfh cell differentiation in PPs.

Immunomodulation by food: impact on gut immunity and immune cell function

Recent studies have revealed that various food components affect the immune response. These components act on various immune cells, and their effects are mediated through the intestinal immune system and, in some cases, the intestinal microbiota. In this review, we describe the immunomodulating effects of various food components, including probiotics, prebiotics, polysaccharides, vitamins, minerals, fatty acids, peptides, amino acids and polyphenols. Some of these components enhance immune responses, leading to host defense against infection, whereas others inhibit immune responses, thus suppressing allergy and inflammation.

Oral administration of ovalbumin after sensitization attenuates symptoms in a mouse model of food allergic enteropathy

Oral immunotherapy (OIT) is a promising treatment of food allergy. To administer an appropriate oral dose of an allergenic component as OIT to individuals sensitized with a food allergen may prevent inducing food allergic inflammation in them. So we attempted to establish a mouse model to evaluate efficacy for oral administration of food allergen after sensitization. In BALB/c mice sensitized by injecting ovalbumin (OVA) with alum twice, OVA was administered before inducing inflammation by feeding the mice with egg white (EW) diet. Severe inflammatory responses, such as enteropathy, weight loss, IL-4 production, and increase of IgE antibody levels, were suppressed by administration with 4 mg of OVA 7 times before feeding EW diet. OVA administration alone induced a slight Th2 response, but no symptoms. The current study demonstrated that severe food allergic enteropathy could be prevented by pre-administration with appropriate dose of OVA to sensitized mice.

The Peyer's Patch Mononuclear Phagocyte System at Steady State and during Infection

The gut represents a potential entry site for a wide range of pathogens including protozoa, bacteria, viruses, or fungi. Consequently, it is protected by one of the largest and most diversified population of immune cells of the body. Its surveillance requires the constant sampling of its encounters by dedicated sentinels composed of follicles and their associated epithelium located in specialized area. In the small intestine, Peyer’s patches (PPs) are the most important of these mucosal immune response inductive sites. Through several mechanisms including transcytosis by specialized epithelial cells called M-cells, access to the gut lumen is facilitated in PPs. Although antigen sampling is critical to the initiation of the mucosal immune response, pathogens have evolved strategies to take advantage of this permissive gateway to enter the host and disseminate. It is, therefore, critical to decipher the mechanisms that underlie both host defense and pathogen subversive strategies in order to develop new mucosal-based therapeutic approaches. Whereas penetration of pathogens through M cells has been well described, their fate once they have reached the subepithelial dome (SED) remains less well understood. Nevertheless, it is clear that the mononuclear phagocyte system (MPS) plays a critical role in handling these pathogens. MPS members, including both dendritic cells and macrophages, are indeed strongly enriched in the SED, interact with M cells, and are necessary for antigen presentation to immune effector cells. This review focuses on recent advances, which have allowed distinguishing the different PP mononuclear phagocyte subsets. It gives an overview of their diversity, specificity, location, and functions. Interaction of PP phagocytes with the microbiota and the follicle-associated epithelium as well as PP infection studies are described in the light of these new criteria of PP phagocyte identification. Finally, known alterations affecting the different phagocyte subsets during PP stimulation or infection are discussed.

Citrus pectin attenuates endotoxin shock via suppression of Toll-like receptor signaling in Peyer's patch myeloid cells

Pectin, a water-soluble dietary fiber, has been found to improve survival in endotoxin shock. However, the underlying mechanism by which pectin exerts its protective effect against endotoxin shock remains unknown. Apart from its prebiotic effects, it has been suggested that pectin directly affects immune cells to regulate inflammatory responses. In this study, we investigated the direct effect of pectin in murine model of endotoxin shock. Citrus pectin solution was administered to male C57BL/6 mice for 10 days. Thereafter, hypothermia was induced in the mice with intraperitoneal injection of lipopolysaccharide (LPS). The pectin-treated mice showed attenuation of both the decrease in rectal temperature and increase in serum IL-6 level as compared to vehicle control mice. Simultaneously, the pectin-treated mice showed reduced levels of inflammatory cytokine mRNA in Peyer's patches and mesenteric lymph nodes, but not in the spleen. Peyer's patch cells from the pectin-treated mice were sorted and their levels of IL-6 production on LPS stimulation were measured. The results of ex vivo analysis indicated that IL-6 secretion from CD11c⁺ cells was suppressed by oral administration of pectin. Furthermore, IL-6 secretion from Toll-like receptor (TLR)-activated RAW264.7 cells was suppressed by pretreatment with pectin in vitro. This suppression was observed even with degraded pectin pretreatment but not with polygalacturonic acid, as the principal constituent of the pectin backbone. Taken together, these results suggest that pectin intake suppresses TLR-induced inflammatory cytokine expression in Peyer's patch myeloid cells, presumably through inhibition of TLR signaling by the pectin side chains.

CCR6 Deficiency Impairs IgA Production and Dysregulates Antimicrobial Peptide Production, Altering the Intestinal Flora

Intestinal immunity exists as a complex relationship among immune cells, epithelial cells, and microbiota. CCR6 and its ligand-CCL20 are highly expressed in intestinal mucosal tissues, such as Peyer's patches (PPs) and isolated lymphoid follicles (ILFs). In this study, we investigated the role of the CCR6-CCL20 axis in intestinal immunity under homeostatic conditions. CCR6 deficiency intrinsically affects germinal center reactions in PPs, leading to impairments in IgA class switching, IgA affinity, and IgA memory B cell production and positioning in PPs, suggesting an important role for CCR6 in T-cell-dependent IgA generation. CCR6 deficiency impairs the maturation of ILFs. In these follicles, group 3 innate lymphoid cells are important components and a major source of IL-22, which stimulates intestinal epithelial cells (IECs) to produce antimicrobial peptides (AMPs). We found that CCR6 deficiency reduces IL-22 production, likely due to diminished numbers of group 3 innate lymphoid cells within small-sized ILFs. The reduced IL-22 levels subsequently decrease the production of AMPs, suggesting a critical role for CCR6 in innate intestinal immunity. Finally, we found that CCR6 deficiency impairs the production of IgA and AMPs, leading to increased levels of Alcaligenes in PPs, and segmented filamentous bacteria in IECs. Thus, the CCR6-CCL20 axis plays a crucial role in maintaining intestinal symbiosis by limiting the overgrowth of mucosa-associated commensal bacteria.

Spirulina Protects against Hepatic Inflammation in Aging: An Effect Related to the Modulation of the Gut Microbiota?

Aging predisposes to hepatic dysfunction and inflammation that can contribute to the development of non-alcoholic fatty liver disease. Spirulina, a cyanobacterium used as a food additive or food supplement, has been shown to impact immune function. We have tested the potential hepatoprotective effect of a Spirulina in aged mice and to determine whether these effects can be related to a modulation of the gut microbiota. Old mice have been fed a standard diet supplemented with or without 5% Spirulina for six weeks. Among several changes of gut microbiota composition, an increase in Roseburia and Lactobacillus proportions occurs upon Spirulina treatment. Interestingly, parameters related to the innate immunity are upregulated in the small intestine of Spirulina-treated mice. Furthermore, the supplementation with Spirulina reduces several hepatic inflammatory and oxidative stress markers that are upregulated in old mice versus young mice. We conclude that the oral administration of a Spirulina is able to modulate the gut microbiota and to activate the immune system in the gut, a mechanism that may be involved in the improvement of the hepatic inflammation in aged mice. Those data open the way to new therapeutic tools in the management of immune alterations in aging, based on gut microbe-host interactions.

Variation and significance of secretory immunoglobulin A, interleukin 6 and dendritic cells in oral cancer

The present study aimed to determine changes in the concentration of secretory immunoglobulin A (SIgA) and interleukin 6 (IL-6) in the saliva of patients with oral cancer, to evaluate the abnormal expression of cluster of differentiation (CD) 1a, CD83, CD80 and CD86 on dendritic cells (DCs) of oral cancer tissues and to discuss the interaction between SIgA, IL-6 and DCs in oral cancer. A total of 40 patients between 27 and 70 years of age, median age 52 years, with primary oral cancer were enrolled in the present study, and a group of 20 healthy male and female volunteers was used as the control group. The concentration of SIgA and IL-6 in the saliva of the preoperative patients was determined by ELISA. The expression levels of CD1a, CD83, CD80 and CD86 were detected by immunohistochemistry and flow cytometry, which was performed on histopathological sections from paraffin-embedded tumor and corresponding adjacent control tissues. The specimens were assessed using the semi-quantitative immunoreactive score (IRS). The concentration of SIgA in the saliva from patients with oral cancer decreased, whereas the IL-6 level significantly increased compared with the control subjects (P<0.05). In addition, the decrease of SIgA level and increase of IL-6 level exhibited a negative correlation (r=−0.543, P<0.05). According to the IRS score, the expression levels of CD1a, CD83, CD80 and CD86 in the cancer tissue were lower than the expression levels of the control group (P<0.05). Furthermore, the expression of CD80 and CD86 exhibited no correlation with histological grade or pathological type (P>0.05), but exhibited a negative correlation with clinical stage and lymph node metastasis (P<0.05). The concentration of SIgA and IL-6 in saliva may be used as an auxiliary diagnostic indicator for oral cancer. The detection of CD80 and CD86 expressed on DCs in oral cancer tissue may be useful for the diagnosis and evaluation of the prognosis of tumors. The present study hypothesized that the use of SIgA vaccines or IL-6 inhibitors may be useful for reversing the immune deficiency associated with DCs in oral cancer.

An expanding stage for commensal microbes in host immune regulation

Gastrointestinal commensal microbiota is a concentrated mix of microbial life forms, including bacteria, fungi, archaea and viruses. These life forms are targets of host antimicrobial defense in order to establish a homeostatic symbiosis inside the host. However, they are also instrumental in shaping the functions of our immune system via a diverse set of communication mechanisms. In the gut, T helper 17, regulatory T and B cells are continuously tuned by specific microbial strains and metabolic processes. These cells in return help to establish a mutually beneficial exchange with the gut microbial contents. Imbalances in this symbiosis lead to dysregulations in the host's ability to control infections and the development of autoimmune diseases. In addition, the commensal microbiota has a significant and obligatory role in shaping both gut intrinsic and distal lymphoid organs, casting a large impact on the overall immune landscape in the host. This review discusses the major components of the microbial community in the gut and how its members collectively and individually exert regulatory roles in the host immune system and lymphoid structure development, as well as the functions of several major immune cell types.

Insight into the role of TSLP in inflammatory bowel diseases

Proinflammatory cytokines are thought to modulate pathogeneses of various inflammatory bowel diseases (IBDs). Thymic stromal lymphopoietin (TSLP), which has been studied in various allergic diseases such as asthma, atopic dermatitis (AD) and eosinophilic esophagitis (EoE), has been less considered to be involved in IBDs. However, mucosal dendritic cells (DCs) induced by various cytokines including TSLP were reported to cause polarization of T cell toward Th2 response, the differentiation of regulatory T-cell (Treg), and secretion of IgA by B cells. In this review, we discuss the concept that decreased TSLP has the potential to accelerate the development of Th1 response dominant diseases such as the Crohn's disease (CD) while increased TSLP has the potential to lead to a development of Th2 cell dominant diseases such the ulcerative colitis (UC). To examine TSLP's role as a potential determining factor for differentiating UC and CD, we analyzed the effects of other genes regulated by TSLP in regards to the UC and CD pathogeneses using data from online open access resources such as NetPath, GeneMania, and the String database. Our findings indicate that TSLP is a key mediator in the pathogenesis of IBDs and that further studies are needed to evaluate its role.

Intestinal immunostimulatory activity of neutral polysaccharide isolated from traditionally fermented Korean brown rice vinegar

In this study, diverse intestinal immunostimulatory activities were demonstrated for polysaccharides (KBV-CP) isolated from Korean brown rice vinegar. Monosaccharide composition analysis indicated that KBV-CP was composed mainly of neutral sugar units, primarily glucose and mannose. In vitro, KBV-CP significantly augmented the productions of immunoglobulin A (IgA) and IgA-related cytokines such as interleukin-6 (IL-6) and transforming growth factor-β (TGF-β) in a dose-dependent manner. Furthermore, results of an in vitro co-culture system of intestinal Caco-2 cells and RAW 264.7 macrophage cells suggested that KBV-CP is not only cytotoxic to Caco-2 cells but also capable of being transported across the small intestinal barrier. Oral administration of KBV-CP every other day for 20 days induced the IgA production by Peyer's patch cells as well as in intestinal fluid and fecal extract. In addition, the production of IgA-related cytokines such as TGF-β and IL-6, and granulocyte macrophage colony-stimulating factor was triggered.

Health effects of probiotics on the skin

Skin is the largest organ of the body and is constantly exposed to physical, chemical, bacterial, and fungal challenges. It is well known that probiotics are helpful for specific disorders and different clinical studies have indicated that probiotics have special effects in cutaneous apparatus directly or indirectly that can be considerable from versatile aspects. Probiotic bacteriotherapy can have great potential in preventing and treating the skin diseases including eczema, atopic dermatitis, acne, and allergic inflammation or in skin hypersensitivity, UV-induced skin damage, wound protection, and as a cosmetic product. The current paper comprehensively reviews the different health effects of probiotics on the skin.

Secretory IgA in complex with Lactobacillus rhamnosus potentiates mucosal dendritic cell-mediated Treg cell differentiation via TLR regulatory proteins, RALDH2 and secretion of IL-10 and TGF-β

The importance of secretory IgA in controlling the microbiota is well known, yet how the antibody affects the perception of the commensals by the local immune system is still poorly defined. We have previously shown that the transport of secretory IgA in complex with bacteria across intestinal microfold cells results in an association with dendritic cells in Peyer's patches. However, the consequences of such an interaction on dendritic cell conditioning have not been elucidated. In this study, we analyzed the impact of the commensal Lactobacillus rhamnosus, alone or associated with secretory IgA, on the responsiveness of dendritic cells freshly recovered from mouse Peyer's patches, mesenteric lymph nodes, and spleen. Lactobacillus rhamnosus-conditioned mucosal dendritic cells are characterized by increased expression of Toll-like receptor regulatory proteins [including single immunoglobulin interleukin-1 receptor-related molecule, suppressor of cytokine signaling 1, and Toll-interacting molecule] and retinaldehyde dehydrogenase 2, low surface expression of co-stimulatory markers, high anti- versus pro-inflammatory cytokine production ratios, and induction of T regulatory cells with suppressive function. Association with secretory IgA enhanced the anti-inflammatory/regulatory Lactobacillus rhamnosus-induced conditioning of mucosal dendritic cells, particularly in Peyer's patches. At the systemic level, activation of splenic dendritic cells exposed to Lactobacillus rhamnosus was partially dampened upon association with secretory IgA. These data suggest that secretory IgA, through coating of commensal bacteria, contributes to the conditioning of mucosal dendritic cells toward tolerogenic profiles essential for the maintenance of intestinal homeostasis.

Tissue-specific mRNA expression profiles of porcine Toll-like receptors at different ages in germ-free and conventional pigs

Toll-like receptors (TLRs), key initiators of innate immune responses, recognize antigens and are essential in linking innate and adaptive immune responses. Misrecognition and over-stimulation/expression of TLRs may contribute to the development of chronic inflammatory diseases and autoimmune diseases. However, appropriate and mature TLR responses are associated with the establishment of resistance against some infectious diseases. In this study, we assessed the mRNA expression profile of TLRs 1-10 in splenic and ileal mononuclear cells (MNCs) and dendritic cells (DCs) of germ-free (GF) and conventional pigs at different ages. We found that the TLR mRNA expression profiles were distinct between GF and conventional pigs. The expression profiles were also significantly different between splenic and ileal MNCs/DCs. Comparison of the TLR expression profiles in GF and conventional newborn and young pigs demonstrated that exposure to commensal microbiota may play a more important role than age in TLR mRNA expression profiles. To our knowledge, this is the first report that systematically assesses porcine TLRs 1-10 mRNA expression profiles in MNCs and DCs from GF and conventional pigs at different ages. These results further highlighted that the commensal microbiota of neonates play a critical role through TLR signaling in the development of systemic and mucosal immune systems.

Targeting Antigens to Dec-205 on Dendritic Cells Induces Immune Protection in Experimental Colitis in Mice

The endocytotic c-type lectin receptor DEC-205 is highly expressed on immature dendritic cells. In previous studies, it was shown that antigen-targeting to DEC-205 is a useful tool for the induction of antigen-specific Foxp3⁺ regulatory T cells and thereby can prevent inflammatory processes. However, whether this approach is sufficient to mediate tolerance in mucosal tissues like the gut is unknown. In this study, we established a new mouse model in which the adoptive transfer of naive hemagglutinin (HA)-specific CD4⁺Foxp3^– T cells into VILLIN-HA transgenic mice leads to severe colitis. To analyze if antigen-targeting to DEC-205 could protect against inflammation of the gut, VILLIN-HA transgenic mice were injected with an antibody–antigen complex consisting of the immunogenic HA_110–120 peptide coupled to an α-DEC-205 antibody (DEC-HA) before adoptive T cell transfer. DEC-HA-treated mice showed significantly less signs of intestinal inflammation as was demonstrated by reduced loss of body weight and histopathology in the gut. Strikingly, abrogated intestinal inflammation was mediated via the conversion of naive HA-specific CD4⁺Foxp3^– T cells into HA-specific CD4⁺Foxp3⁺ regulatory T cells. In this study, we provide evidence that antigen-targeting to DEC-205 can be utilized for the induction of tolerance in mucosal organs that are confronted with large numbers of exogenous antigens.