清野 宏

腸管は我々の体内に存在するが、体表面を覆う皮膚と同様、つねに外的環境に曝されている。そこには個体にとって「非自己」である腸内細菌叢も存在し、免疫担当細胞や抗菌ペプチドなどを産生する上皮細胞と協働しながら絶妙なバランスを保ち、腸内の恒常性を維持していると考えられている。何らかの原因でこのバランスが崩れると、一時的に、時には慢性的に、炎症反応が誘発され、炎症性腸疾患などのような自己免疫疾患の原因になり得ることがわかってきた。(著者抄録)

BACKGROUND: Maternal dietary exposures are considered to influence the development of infant allergies through changes in the composition of breast milk. Cohort studies have shown that ω3 PUFA in breast milk may have a beneficial effect on the preventing of allergies in infants; however, the underlying mechanisms remain to be investigated. We investigated how the maternal intake of dietary ω3 PUFAs affects fatty acid profiles in the breast milk and their pups and reduced the incidence of allergic diseases in the pups. METHODS: Contact hypersensitivity (CHS) induced by 2,4-dinitrofluorobenzene and fluorescein isothiocyanate was applied to the skin in pups reared by mother maintained with diets mainly containing ω3 or ω6 PUFAs. Skin inflammation, immune cell populations and expression levels of immunomodulatory molecules in pups and/or human cell line were investigated by using flow cytometric, immunohistologic, and quantitative RT-PCR analyses. ω3 PUFA metabolites in breast milk and infant's serum were evaluated by lipidomics analysis using LC-MS/MS. RESULTS: We show that maternal intake of linseed oil, containing abundant ω 3 α-linolenic acid, resulted in the increased levels of ω 3 docosapentaenoic acid (DPA) and its 14-lipoxygenation products in the breast milk of mouse dams; these metabolites increased the expression of TNF-related apoptosis-inducing ligand (TRAIL) on plasmacytoid dendritic cells (pDCs) in their pups and thus inhibited infant CHS. Indeed, the administration of DPA-derived 14-lipoxygenation products to mouse pups ameliorated their DNFB CHS. CONCLUSION: These findings suggest that an inhibitory mechanism in infant skin allergy is induced through maternal metabolism of dietary ω3 PUFAs in mice.

Secretory immunoglobulin A, the most abundant antibody isotype in the body, maintains a mutual relationship with commensal bacteria and acts as a primary barrier at the mucosal surface. Colonization by commensal bacteria induces an IgA response, at least partly through a T-cell-independent process. However, the mechanism underlying the commensal-bacteria-induced T-cell-independent IgA response has yet to be fully clarified. Here, we show that commensal-bacteria-derived butyrate promotes T-cell-independent IgA class switching recombination (CSR) in the mouse colon. Notably, the butyrate concentration in human stools correlated positively with the amount of IgA. Butyrate upregulated the production of transforming growth factor β1 and all-trans retinoic acid by CD103+CD11b+ dendritic cells, both of which are critical for T-cell-independent IgA CSR. This effect was mediated by G-protein-coupled receptor 41 (GPR41/FFA3) and GPR109a/HCA2, and the inhibition of histone deacetylase. The butyrate-induced IgA response reinforced the colonic barrier function, preventing systemic bacterial dissemination under inflammatory conditions. These observations demonstrate that commensal-bacteria-derived butyrate contributes to the maintenance of the gut immune homeostasis by facilitating the T-cell-independent IgA response in the colon.

Because the mucosa is the major entry route for most pathogens, the development of mucosal vaccines is a rational approach for protecting against these undesired agents. Mucosal administration of vaccine antigen is useful for non-infectious chronic diseases as well, because of its advantages over injection routes, including comparable efficacy in the induction of systemic immune responses, less pain, and no risk of adverse events at the injection site. However, because it is difficult to effectively induce and regulate antigen-specific mucosal and systemic immune responses when antigen alone is mucosally administered, an appropriate form of mucosal delivery vehicle must be used. Antigen delivery systems involving nanogels, which act as artificial chaperones and mucosal adhesives, are a promising approach to overcoming this problem. Here, we introduce current perspectives regarding the development of nanogel-based nasal vaccines for both infectious and lifestyle-related diseases.

Introduction: Nasal vaccination is one of the most effective immunization methods because it can induce effective antigen-specific immune responses not only at the mucosal site of administration but also at distant mucosal surfaces, as well as in the systemic compartment. Based on this advantage, many nasal vaccines are being developed and some have been licensed and marketed for clinical use. However, some have been withdrawn because of unacceptable adverse events such as inactivated influenza vaccine administrated with a heat-labile enterotoxin of Escherichia coli as an adjuvant. Thus, it is important to consider both the efficacy and safety of nasal vaccines.Areas covered: This review describes the benefits of cholesteryl group-bearing pullulan (CHP) nanogels for nasal vaccine delivery and vaccine development identified on Pubmed database with the term Nanogel-based nasal vaccine'.Expert commentary: CHP nanogels have been developed as novel drug delivery system, and a cationic CHP nanogels have been demonstrated to induce effective immunity as a nasal vaccine antigen carrier. Since vaccine antigens incorporated into CHP nanogels have exhibited no brain deposition after nasal administration in mice and nonhuman primates, the vaccine seems safe, and could be a promising new delivery system.

Intestinal epithelial cells apically express glycans, especially alpha 1,2-fucosyl linkages, which work as a biological interface for the host microbe interaction. Emerging studies have shown that epithelial alpha 1,2-fucosylation is regulated by microbes and by group 3 innate lymphoid cells (ILC3s). Dysregulation of the gene (FUT2) encoding fucosyltransferase 2, an enzyme governing epithelial alpha 1,2-fucosylation, is associated with various human disorders, including infection and chronic inflammatory diseases. This suggests a critical role for an interaction between microbes, epithelial cells and ILC3s mediated via glycan residues. In this Review, using alpha 1,2-fucose and Fut2 gene expression as an example, we describe how epithelial glycosylation is controlled by immune cells and luminal microbes. We also address the pathophysiological contribution of epithelial alpha 1,2-fucosylation to pathogenic and commensal microbes as well as the potential of alpha 1,2-fucose and its regulatory pathway as previously unexploited targets in the development of new therapeutic approaches for human diseases.

The oral cavity is the beginning of the aero-digestive tract, which is covered by mucosal epithelium continuously under the threat of invasion of pathogens, it is thus protected by the mucosal immune system. In the early phase of our scientific efforts for the demonstration of mucosal immune system, dental science was one of major driving forces due to their foreseeability to use oral immunity for the control of oral diseases. The mucosal immune system is divided functionally into, but interconnected inductive and effector sites. Intestinal Peyer's patches (PPs) are an inductive site containing antigen-sampling M cells and immunocompetent cells required to initiate antigen-specific immune responses. At effector sites, PP-originated antigen-specific IgA B cells become plasma cells to produce polymeric IgA and form secretory IgA by binding to poly-Ig receptor expressed on epithelial cells for protective immunity. The development of new-generation mucosal vaccines, including the rice-based oral vaccine MucoRice, on the basis of the coordinated mucosal immune system is a promising strategy for the control of mucosal infectious diseases.

Integrins mediate leukocyte accumulation to the sites of inflammation, thereby enhancing their potential as an important therapeutic target for inflammatory disorders. Integrin activation triggered by inflammatory mediators or signaling pathway is a key step to initiate leukocyte migration to inflamed tissues; however, an appropriately regulated integrin deactivation is indispensable for maintaining productive leukocyte migration. While typical integrin antagonists that block integrin activation target the initiation of leukocyte migration, a novel class of experimental compounds has been designed to block integrin deactivation, thereby perturbing the progression of cell migration. Current review discusses the mechanisms by which integrin is activated and subsequently deactivated by focusing on its structure-function relationship.

It has been about 30 years since the first plant engineering technology was established. Although the concept of plant-based pharmaceuticals or vaccines motivates us to develop practicable commercial products using plant engineering, there are some difficulties in reaching the final goal: to manufacture an approved product. At present, the only plantmade vaccine approved by the United States Department of Agriculture is a Newcastle disease vaccine for poultry that is produced in suspension-cultured tobacco cells. The progress toward commercialization of plant-based vaccines takes much effort and time, but several candidate vaccines for use in humans and animals are in clinical trials. This review discusses plant engineering technologies and regulations relevant to the development of plant-based vaccines and provides an overview of human and animal vaccines currently under clinical trials.

Nanogels, nanometer-sized hydrogels with three-dimensional networks, are useful biomaterials for delivery of bioactive molecules (e.g., drug, protein, and nucleic acid) into the targeted tissues. Pullulan, which is a polysaccharide long-chain polymer, forms self-assembled nanogels by introducing cholesterol groups. The cholesteryl group-bearing pullulan (CHP) nanogels are capable of incorporating vaccine antigen in the hydrogels in vitro, and releasing it while keeping its antigenicity and immunogenicity in vivo. One practical advantage of using the CHP nanogels is that the further beneficial properties can be freely added on their original characters. For example, cationic type CHP (cCHP) nanogels, which are bioengineered by adding amine groups to CHP nanogels, enables us to deliver vaccine antigen into the negatively charged nasal epithelium efficiently following nasal administration, resulting in effective uptaking of the antigen by nasal dendritic cells that possesses important roles in inducing the antigen-specific immune responses in nasal mucosa. In this chapter, we review the immunobiological characteristics of cCHP nanogels as potential antigen delivery vehicles for nasal vaccine.

&nbsp;&nbsp;Most pathogens invade body through the mucosal epithelium, which is a primary target to prevent the infectious diseases. Mucosal vaccine has been considered to be an effective strategy to establish immunosurveillance against pathogens by the induction of antigen-specific immune responses at both mucosal and systemic immune compartments. The development of antigen delivery system and mucosal adjuvants are required for the sufficient induction of protective immunity in the development of mucosal vaccine. In this review, we shed light on the recent advances in the development of antigen delivery system using microbial functions for mucosal vaccines.<br>

Mast cells are known effector cells in allergic and inflammatory diseases, but their precise roles in intestinal inflammation remain unknown. Here we show that activation of mast cells in intestinal inflammation is mediated by ATP-reactive P2X7 purinoceptors. We find an increase in the numbers of mast cells expressing P2X7 purinoceptors in the colons of mice with colitis and of patients with Crohn&#039;s disease. Treatment of mice with a P2X7 purinoceptor-specific antibody inhibits mast cell activation and subsequent intestinal inflammation. Similarly, intestinal inflammation is ameliorated in mast cell-deficient Kit W-sh/W-sh mice, and reconstitution with wild-type, but not P2x7-/-mast cells results in susceptibility to inflammation. ATP-P2X7 purinoceptor-mediated activation of mast cells not only induces inflammatory cytokines, but also chemokines and leukotrienes, to recruit neutrophils and subsequently exacerbate intestinal inflammation. These findings reveal the role of P2X7 purinoceptor-mediated mast cell activation in both the initiation and exacerbation of intestinal inflammation. © 2012 Macmillan Publishers Limited. All rights reserved.

Immune responses in the aerodigestive tract are characterized by production and transport of specific IgA antibodies across the epithelium to act as a first line of defense against pathogens in the external environment. To sample antigens on mucosal surfaces in the intestine and upper respiratory tract, the immune system relies on a close collaboration between specialized antigen-sampling epithelial M cells and lymphoid cells. Depending on various factors, local antigen presentation in the mucosal tissue leads to tolerance or initiation of an active immune response. Recently, molecules that could be used to target vaccine antigens to apical M cell surfaces have been identified. Here we review the M cell-targeted vaccine strategy, an approach that could be used to enhance uptake and efficacy of vaccines delivered in the nasal cavity or intestine. © 2011 Springer-Verlag Berlin Heidelberg.

免疫系は通常、生体にとって有害な異物を排除するための生体防御システムとして機能しているが、稀に生体にとって有益な異物に対する過剰な反応を示すことがある。その代表的な免疫反応が免疫毒性とも呼ばれるアレルギー反応である。我々はこうしたアレルギー疾患のうち食物アレルギーに焦点を絞り、その発症メカニズムの解析を通じた食物アレルギーの予防・治療法の確立を目指している。&lt;br&gt; 食物アレルギーの病態形成部位である腸管には粘膜免疫システムと呼ばれる精密な免疫システムが構築されており、食餌性成分や腸内細菌など生体にとって有益な異物に対しては抑制型の免疫システムを示すことで、恒常性を維持したまま有益な異物の摂取を可能にしている。腸管免疫システムの恒常性維持機構の破綻により引き起こされる食物アレルギーは近年、乳幼児を中心に患者数が増加しているが、現時点での対処法は原因アレルゲンを含む食物を摂取しないという方法であり、Quality of Lifeの観点からも予防・治療法の開発が待望されている。我々は卵白アルブミンをアレルゲンとして用いた食物アレルギーモデルマウスを樹立し、免疫学的解析を進めている。本アレルギーモデルにおいては、卵白アルブミンで感作したマウスに卵白アルブミンを頻回経口投与することでアレルギー性の下痢が観察される。この下痢症状は一過性の症状であり、感作に用いたアレルゲンと同一のアレルゲンの経口投与が必要なアレルゲン特異的反応であり、その反応には2型ヘルパーT細胞により誘導されるアレルゲン特異的IgEが必須である。さらにはアレルギー性下痢を呈したマウスの腸管組織、特に粘膜固有層には活性化したT細胞やマスト細胞の増加が観察され、その増加を抑制することによりアレルギー性下痢の発症が抑制出来ることも示している。これらの結果から、本アレルギーモデルはヒトの食物アレルギーと非常に近い１型アレルギー疾患モデルとして広く使用されている。&lt;br&gt; 本シンポジウムでは我々がこれまで蓄積してきた食物アレルギーを用いた免疫学的解析について、特にマスト細胞の役割について紹介すると共に、マスト細胞特異的な疾患治療の可能性について報告したい。

In the mucosal immune system, M cells are known as specialized epithelial cells that take up luminal antigens, although the receptors on M cells and the mechanism of antigen uptake into M cells are not well-understood. Here, we report the expression of the complement C5a receptor (C5aR) on the apical surface of M cells. C5ar mRNA expression in co-cultured Caco-2 human M-like cells was six-fold higher than in mono-cultured cells. C5aR expression was detected together with glycoprotein 2, an M-cell-specific protein, on the apical surface of M-like cells and mouse Peyer's patch M cells. Interestingly, after oral administration of Yersinia enterocolitica which expresses outer membrane protein H (OmpH) that is homologous to the Skp alpha 1 domain of Escherichia coli, a ligand of C5aR, dense clustering and phosphorylation of C5aR were detected in M cells. Finally, targeted antigen delivery to M cells using C5aR as a receptor was achieved using the OmpH alpha 1 of Y. enterocolitica such that the induction of ligand-conjugated antigen-specific immune responses was confirmed in mice after oral immunization of the OmpH beta 1 alpha 1-conjugated antigen. Collectively, we identified C5aR expression on M cells and suggest that C5aR could be used as a target receptor for mucosal antigen delivery.