Biomedical subjects

Blaise Corthésy

Publications and source records attributed to Blaise Corthésy.

At least 19 recordsLinked to original sources

PubMed2007

Roundtrip ticket for secretory IgA: role in mucosal homeostasis?

An important activity of mucosal surfaces is the production of Ab referred to as secretory IgA (SIgA). SIgA serves as the first line of defense against microorganisms through a mechanism called immune exclusion. In addition, SIgA adheres selectively to M cells in intestinal Peyer's patches, thus mediating the transepithelial transport of the Ab molecule from the intestinal lumen to underlying gut-associated organized lymphoid tissue. In Peyer's patches, SIgA binds and is internalized by dendritic cells in the subepithelial dome region. When used as carrier for Ags in oral immunization, SIgA induces mucosal and systemic responses associated with production of anti-inflammatory cytokines and limits activation of dendritic cells. In terms of humoral immunity at mucosal surfaces, SIgA appears thus to combine properties of a neutralizing agent (immune exclusion) and of a mucosal immunopotentiator inducing effector immune responses in a noninflammatory context favorable to preserve local homeostasis of the gastrointestinal tract.

Breast Feeding↗

PubMed2006

Rotavirus anti-VP6 secretory immunoglobulin A contributes to protection via intracellular neutralization but not via immune exclusion.

Immunoglobulin A (IgA) monoclonal antibodies (MAbs) directed at the conserved inner core protein VP6 of rotavirus, such as the IgA7D9 MAb, provide protective immunity in adult and suckling mice when delivered systemically. While these antibodies do not have traditional in vitro neutralizing activity, they could mediate their antiviral activity either by interfering with the viral replication cycle along the IgA secretory pathway or by acting at mucosal surfaces as secretory IgA and excluding virus from target enterocytes. We sought to determine the critical step at which antirotaviral activity was initiated by the IgA7D9 MAb. The IgA7D9 MAb appeared to directly interact with purified triple-layer viral particles, as shown by immunoprecipitation and immunoblotting. However, protection was not conferred by passively feeding mice with the secretory IgA7D9 MAb. This indicates that the secretory IgA7D9 MAb does not confer protection by supplying immune exclusion activity in vivo. We next evaluated the capacity of polymeric IgA7D9 MAb to neutralize rotavirus intracellularly during transcytosis. We found that when polymeric IgA7D9 MAb was applied to the basolateral pole of polarized Caco-2 intestinal cells, it significantly reduced viral replication and prevented the loss of barrier function induced by apical exposure of the cell monolayer to rotavirus, supporting the conclusion that the antibody carries out its antiviral activity intracellularly. These findings identify a mechanism whereby the well-conserved immunodominant VP6 protein can function as a target for heterotypic antibodies and protective immunity.

Animals↗

PubMed2006

Glycans on secretory component participate in innate protection against mucosal pathogens.

In mucosal secretions, secretory component (SC) is found either free or bound to polymeric IgA within the secretory IgA complex. SC displays numerous and various glycans, which are potential ligands for bacterial compounds. We first established that human SC (hSC) purified from colostrum (hSCcol) or produced in Chinese hamster ovary cells (hSCrec) exhibits the same lectin reactivity. Both forms bind to Clostridium difficile toxin A and functionally protect polarized Caco-2 cell monolayers from the cytopathic effect of the toxin. The interaction is mediated by glycans present on hSC and involves galactose and sialic acid residues. hSCcol and hSCrec were also shown to bind enteropathogenic Escherichia coli adhesin intimin and to inhibit its infectivity on HEp-2 cells in a glycan-dependent manner as well. SC remained operative in the context of the whole secretory IgA molecule and can therefore enhance its Fab-mediated neutralizing properties. On the contrary, hSC did not interact with three different strains of rotavirus (RF, RRV, and SA11). Accordingly, infection of target MA104 cells with these rotavirus strains was not reduced in the presence of either form of hSC tested. Although not a universal mechanism, these findings identify hSC as a microbial scavenger contributing to the antipathogenic arsenal that protects the body epithelial surfaces.

Animals↗

PubMed2006

Food products and allergy development, prevention and treatment.

In westernized countries allergic diseases have reached epidemic proportions. Food is frequently a perpetrator of allergy but, in turn, modified food and selected food ingredients can become valuable intervention tools in the fight against allergy. There are two basic approaches towards mitigation of food allergy through nutrition: to reduce the allergenicity of raw food materials by physical, chemical or genetic methods or to influence host immunity towards a non-allergic state using various food ingredients. Dietary intervention for the prevention and therapy of allergy is an emerging field where initial findings from animal studies are now being validated in human trials. Nevertheless, to consolidate the utility of such interventions, more pre-clinical and clinical studies remain necessary.

Animals↗

PubMed2005

Pyelonephritic Escherichia coli expressing P fimbriae decrease immune response of the mouse kidney.

P fimbriae are proteinaceous appendages on the surface of Escherichia coli bacteria that mediate adherence to uroepithelial cells. E. coli that express P fimbriae account for the majority of ascending urinary tract infections in women with normal urinary tracts. The hypothesis that P fimbriae on uropathic E. coli attach to renal epithelia and may regulate the immune response to establish infection was investigated. The polymeric Ig receptor (pIgR), produced by renal epithelia, transports IgA into the urinary space. Kidney pIgR and urine IgA levels were analyzed in a mouse model of ascending pyelonephritis, using E. coli with (P+) and without (P-) P fimbriae, to determine whether P(+) E. coli regulate epithelial pIgR expression and IgA transport into the urine. (P+) E. coli establish infection and persist to a greater amount than P(-) E. coli. P(+)-infected mice downregulate pIgR mRNA and protein levels compared with P(-)-infected or PBS controls at > or =48 h. The decrease in pIgR was associated with decreased urinary IgA levels in the P(+)-infected group at 48 h. pIgR mRNA and protein also decline in P(+) E. coli-infected LPS-hyporesponsive mice. These studies identify a novel virulence mechanism of E. coli that express P fimbriae. It is proposed that P fimbriae decrease pIgR expression in the kidney and consequently decrease IgA transport into the urinary space. This may explain, in part, how E. coli that bear P fimbriae exploit the immune system of human hosts to establish ascending pyelonephritis.

Animals↗

PubMed2005

Oral immunization of mice with lactic acid bacteria producing Helicobacter pylori urease B subunit partially protects against challenge with Helicobacter felis.

BACKGROUND: The development of an efficacious vaccine against infection with Helicobacter pylori, the causative agent of chronic gastritis, peptic ulcer disease, and gastric adenocarcinoma, remains a challenge. Since the use of mucosal adjuvants is limited in human application, we have evaluated the potential of recombinant Lactobacillus strains producing H. pylori urease B (UreB) subunit to deliver this antigen to the gastrointestinal tract. METHODS: Mice were injected orally 3 times with a triple dose of recombinant Lactobacillus plantarum NCIMB8826, the recombinant isogenic cell-wall mutant (alr(-) MD007 strain) expressing UreB, or a mixture of recombinant UreB and cholera toxin (rUreB/CT) as a control. Urease-specific seric immunoglobulin (Ig) G and IgA were measured by use of an enzyme-linked immunosorbent assay. After challenge with Helicobacter felis, stomach infection was examined by use of the rapid urease test and by polymerase chain reaction detection of Helicobacter genomic DNA. RESULTS: Intragastric immunization with both recombinant Lactobacillus strains and rUreB/CT elicited UreB-specific antibodies. After challenge, reduction of H. felis load in the stomachs of mice was observed only after immunization with the recombinant mutant strain MD007 or with rUreB/CT. CONCLUSIONS: This is the first report of successful induction of partial protection against H. felis with a mucosal prime-boost regimen in which recombinant Lactobacillus strains were used as antigen-delivery vehicles.

Adjuvants, Immunologic↗

PubMed2005

Secretory IgA possesses intrinsic modulatory properties stimulating mucosal and systemic immune responses.

Secretory IgA (SIgA) is essential in protecting mucosal surfaces by ensuring immune exclusion. In addition, SIgA binds selectively to M cells in Peyer's patches (PP), resulting in transport across the epithelium and targeting of dendritic cells (DC) in the dome region. The immunological consequences of such an interaction are unknown. In this study, we find that oral delivery of SIgA comprising human secretory component and mouse IgA induces human secretory component-specific Ab and cellular responses in mucosal and peripheral tissues in mice. This takes place in the absence of co-addition of cholera toxin, identifying so far unraveled properties in SIgA. Specific immune responses are accompanied by sustained IL-10 and TGF-beta expression in draining mesenteric lymph nodes and spleen. SIgA also triggers migration of DC to the T cell-rich regions of PP, and regulates expression of CD80 and CD86 on DC in PP, mesenteric lymph nodes, and spleen. These results provide evidence that mucosal SIgA re-entering the body exerts a function of Ag delivery that contributes to effector and/or regulatory pathways characteristic of the intestinal mucosal compartment.

Animals↗

PubMed2004

Targeting of secretory IgA to Peyer's patch dendritic and T cells after transport by intestinal M cells.

In addition to being instrumental to the protection of mucosal epithelia, secretory IgA (SIgA) adheres to and is transported by intestinal Peyer's patch (PP) M cells. The possible functional reason for this transport is unknown. We have thus examined in mice the outcome of SIgA delivered from the intestinal lumen to the cells present in the underlying organized mucosa-associated lymphoreticular tissue. We show selective association of SIgA with dendritic cells and CD4(+) T and B lymphocytes recovered from PP in vitro. In vivo, exogenously delivered SIgA is able to enter into multiple PP lining the intestine. In PP, SIgA associates with and is internalized by dendritic cells in the subepithelial dome region, whereas the interaction with CD4(+) T cells is limited to surface binding. Interaction between cells and SIgA is mediated by the IgA moiety and occurs for polymeric and monomeric molecular forms. Thus, although immune exclusion represents the main function of SIgA, transport of the Ab by M cells might promote Ag sampling under neutralizing conditions essential to the homeostasis of mucosal surfaces.

Animals↗

PubMed2004

Zwitterionic polysaccharides stimulate T cells with no preferential V beta usage and promote anergy, resulting in protection against experimental abscess formation.

Zwitterionic polysaccharides (Zps) from pathogenic bacteria, such as Bacteroides fragilis, are virulence factors responsible for abscess formation associated with intra-abdominal sepsis. The underlying cellular mechanism for abscess formation requires T cell activation. Conversely, abscess formation can be prevented by prophylactic s.c. injection of purified Zps alone, a process also dependent on T cells. Hence, the modulatory role of T cells in abscess formation was investigated. We show that Zps interact directly with T cells with fast association/dissociation kinetics. Vbeta repertoire analysis using RT-PCR demonstrates that Zps have broad Vbeta usage. Zps-specific hybridomas responded to a variety of other Zps, but not to a nonzwitterionic polysaccharide, indicating cross-reactivity between different Zps. Furthermore, Zps-reactive T cell hybridomas could effectively transfer protection against abscess formation. Analysis of the proliferative capacity of T cells recovered from Zps-treated animals revealed that these T cells are anergic to subsequent stimulation by the different Zps or to alloantigens in an MLR. This anergic response was relieved by addition of IL-2. Taken together, the data show that this class of polysaccharides interacts directly with T cells in a nonbiased manner to elicit an IL-2-dependent anergic response that confers protection against abscess formation.

Abscess↗

PubMed2004

Modulation of allergic responses in mice by using biodegradable poly(lactide-co-glycolide) microspheres.

BACKGROUND: Biodegradable poly(lactide- co -glycolide) (PLGA) microspheres are a promising carrier for vaccine delivery capable of maturing antigen-presenting cells to stimulate T-cell-mediated immune responses. However, the potential of microspheres to downregulate an allergic response in vivo is unknown. OBJECTIVE: The aim of this study was to determine whether microspheres could potentiate DNA vaccination against allergy and to evaluate the immunomodulatory properties of microspheres alone. METHODS: Mice were treated prophylactically with DNA-loaded plain PLGA microspheres before sensitization with phospholipase A2 (PLA2), the major allergen of bee venom. PLA2-specific IgG1, IgG2a, IgE in serum were measured for 8.5 months, and splenocyte proliferative responses and cytokine profiles were determined. Protection against anaphylaxis was evaluated after injection of an otherwise lethal dose of PLA2. RESULTS: Phospholipase A2-specific IgG1 and IgG2a production turned out to be 2 times higher using cationic microspheres compared with anionic microspheres, but was not influenced by the presence of DNA. In contrast, reduction in IgE production and T-cell hyporesponsiveness were observed with all microsphere formulations. Recall challenge with PLA2 triggered combined expression of both IL-4 and IFN-gamma, together with sustained expression of IL-10 that can explain the protective effect against anaphylaxis. CONCLUSION: Our data suggest a dual mechanism that does initially rely on a TH2 to TH1 immune deviation and then on IL-10-mediated suppression. This is the first physiological demonstration that plain PLGA microspheres can induce tolerance in mice for as long as 6 months postsensitization.

Absorbable Implants↗

PubMed2004

Human polymeric IgA is superior to IgG and single-chain Fv of the same monoclonal specificity to inhibit urease activity associated with Helicobacter pylori.

Helicobacter-induced gastritis is considered nowadays an epidemic, the prevalence of which is one of the highest world-wide (70%), with as much as 40% of the population in industrialized countries. Helicobacter pylori (H. pylori) antigens (Ag) capable to elicit a protective immune response in animal models have been identified, but these antigens have not been shown to be strongly immunogenic when administered to humans. Due to their stability in the gastric environment and avidity, passive administration of secretory immunoglobulin A (SIgA) antibodies (Ab) targeting protective Ag might be particularly relevant as a substitute or complement to current therapies. To this aim, we have designed expression vectors to convert a scFv polypeptide specific for H. pylori urease subunit A into human IgG, polymeric IgA (IgAp/d) and SIgA. Purified proteins show proper binding characteristics toward both the native and denatured forms of H. pylori urease. The direct comparison between different isotype and molecular forms, but of unique specificity, demonstrates that SIgA and IgAp/d are more efficient in blocking free and H. pylori-associated urease than IgG and scFv. We conclude that the expression system reported herein will represent a valuable tool to produce human SIgA Ab of multiple specificities against H. pylori antigens involved in colonization and persistence.

Animals↗

PubMed2003

Simplified procedure to recover recombinant antigenized secretory IgA to be used as a vaccine vector.

Induced protection mechanisms at mucosal surfaces involve secretory IgA (SIgA), a complex structure made of polymeric-dimeric IgA (IgA(p/d)) antibody associated with secretory component (SC). SIgA can adhere to M cells of the intestinal and nasal epithelia, are transported across these latter, and are thus available to the immune cells underlying the epithelia. This property makes SIgA suitable as potential mucosal vaccine delivery vector. It remains that production and purification of SIgA is a complex task since IgA(p/d) and SC are naturally synthesized by two different cell types. Furthermore, only IgA(p/d) are capable to associate with SC. Thus, we sought to separate IgA(p/d) and monomeric IgA (IgA(m)) antibodies secreted by hybridoma cells in CELLine bioreactors. To this aim, we connected together two 1-m long columns filled with Sephacryl S-300 beads and placed them under the control of a automatized chromatographic system. In parallel, we produced recombinant antigenized human SC (ra-hSC) in Chinese hamster ovary (CHO) cells adapted to suspension culture in CELLine bioreactors. To avoid intermediate purification of ra-hSC, culture supernatants (SN) containing this latter were combined with purified IgA(p/d), and the recombinant antigenized SIgA (raSIgA) complex was resolved on a 1-m long column filled with Superdex 200 beads. Biochemical characterization based on SDS-PAGE, silver staining, immunodetection and enzyme-linked immunosorbent assay (ELISA) indicates that highly purified raSIgA can be recovered using this simple two-step procedure. Such preparations are currently used to immunize mice to induce mucosal and systemic responses.

Cloning, Molecular↗

PubMed2003

Novel functions of the polymeric Ig receptor: well beyond transport of immunoglobulins.

The polymeric Ig receptor (pIgR) ensures efficient secretion of polymeric IgA (pIgA) at mucosal surfaces. On basal to apical transport across epithelial cells, the pIgR extracellular domain is cleaved, releasing secretory component (SC) in association with pIgA. This finds its raison d'être in the recent observation that SC is directly involved in the protective function of secretory IgA. In addition, free SC exhibits scavenger properties with respect to enteric pathogens. However, although pIgR dedicates its life to mucosal protection, it also seems to permit pathogen entrance through the epithelial barrier. The multiple mechanisms that they are involved in make pIgR and SC instrumental to mucosal immunity.

Animals↗

PubMed2003

Passive immunity in Helicobacter-challenged neonatal mice conferred by immunized dams lasts until weaning.

The objective of this study was to examine the effect of breast-feeding by immunized dams on Helicobacter colonization in newborns. Urease-based immunization regimens failed to protect nursing pups against H. felis, whereas H. felis lysate-cholera toxin resulted in protection. This observation correlated with a high recognition of cell surface-expressed bacterial antigens by milk antibodies. Protection lasted until weaning, indicating that infection is maintained at undetectable levels by passive immunity but then resumes when breast-feeding stops.

Animals↗

PubMed2003

Recombinant secretory immunoglobulin A in passive immunotherapy: linking immunology and biotechnology.

The use of monoclonal antibodies has become routine in the research and diagnostic laboratories, but the potential of antibody molecules in public health and medical applications is still far from its maximum. Most infections begin at mucosal surfaces, and this is certainly not only a stroke of good fortune if mother's milk serves as a natural delivery vehicle for antibodies protecting the gastrointestinal tract of nursing infants. Mammary gland or other mucous secretions containing numerous antibody specificities provide an efficient mean to immediately protect a mucosal surface against pathogens, which have never been encountered by the host. From a public health perspective, topical passive immunization of mucosal surfaces with monoclonal antibodies can block entry and transmission of bacteria, viruses, fungi and parasites that infect humans, and thus defeat some key immune evasion strategies designed by many pathogens. The chief antibody on most mucosal surfaces is secretory immunoglobulin A (SIgA), a polypeptide complex comprising dimeric IgA, the connecting J chain, and the secretory component. The molecular stability, tetravalency, and strong anti-inflammatory properties make SIgA particularly well suited to fulfill the function of passive protective immunity when applied exogenously to mucosal surfaces. The review will give an overview of the basic concepts underlying mucosal immunity, present the molecular mechanisms whereby SIgA prevents mucosal infections, cover the last advances in the topic of recombinant SIgA production, and examine how structure-function relationship in SIgA will help designing molecules with novel properties for passive immunotherapy.

Animals↗

PubMed2002

Selective adherence of IgA to murine Peyer's patch M cells: evidence for a novel IgA receptor.

M cells represent the primary route by which mucosal Ags are transported across the intestinal epithelium and delivered to underlying gut-associated lymphoid tissues. In rodents and rabbits, Peyer's patch M cells selectively bind and endocytose secretory IgA (SIgA) Abs. Neither the nature of the M cell IgR nor the domains of SIgA involved in this interaction are known. Using a mouse ligated ileal loop assay, we found that monoclonal IgA Abs with or without secretory component, but not IgG or IgM Abs, bound to the apical surfaces of Peyer's patch M cells, indicating that the receptor is specific for the IgA isotype. Human serum IgA and colostral SIgA also bound to mouse M cells. The asialoglycoprotein receptor or other lectin-like receptors were not detected on the apical surfaces of M cells. We used recombinant human IgA1 and human IgA2 Abs and domain swapped IgA/IgG chimeras to determine that both domains Calpha1 and Calpha2 are required for IgA adherence to mouse Peyer's patch M cells. This distinguishes the M cell IgA receptor from CD89 (FcalphaI), which binds domains Calpha2-Calpha3. Finally, we observed by immunofluorescence microscopy that some M cells in the human ileum are coated with IgA. Together these data suggest that mouse, and possibly human, M cells express an IgA-specific receptor on their apical surfaces that mediates the transepithelial transport of SIgA from the intestinal lumen to underlying gut-associated organized lymphoid tissues.

Animals↗

PubMed2002

Microaerophilic conditions permit to mimic in vitro events occurring during in vivo Helicobacter pylori infection and to identify Rho/Ras-associated proteins in cellular signaling.

Molecular dissection of the mechanisms underlying Helicobacter pylori infection suffers from the lack of in vitro systems mimicking in vivo observations. A system was developed whereby human epithelial cells (Caco-2) grown as polarized monolayers and bacteria can communicate with each other under culture conditions optimal for each partner. Caco-2 cells grown on filter supports were inserted in a vertical position into diffusion chambers equilibrated with air and 5% CO(2) at their basolateral surface (aerophilic conditions) and 5% CO(2), 5% O(2), 90% N(2) (microaerophilic conditions) in the apical compartment. Remarkably, the epithelial polarized layer was stable under these asymmetric culture conditions for at least 24 h, and the presence of Caco-2 cells was necessary to maintain H. pylori growth. In contrast to previous studies conducted with non-polarized Caco-2 cells and other cell lines kept under aerophilic conditions, we found H. pylori-dependent stimulation of cytokine secretion (MCP-1 (monocyte chemoattractant protein-1), GRO-alpha (growth-regulated oncogene-alpha), RANTES (regulated on activation normal T cell expressed and secreted)). This correlated with nuclear translocation of NF-kappaB p50 and p65 subunits. Tyrosine phosphorylation of nine cellular proteins was induced or enhanced; we identified p120(RasGAP), p190(RhoGAP), p62dok (downstream of tyrosine kinases), and cortactin as H. pylori-inducible targets. Moreover, reduction of H. pylori urease expression was observed in adherent bacteria as compared with bacteria in suspension. In addition to mimicking several observations seen in the inflamed gastric mucosa, the novel in vitro system was allowed to underscore complex cellular events not seen in classical in vitro analyses of microaerophilic bacteria-epithelial cell cross-talk.

Caco-2 Cells↗

PubMed2002

Recombinant immunoglobulin A: powerful tools for fundamental and applied research.

The use of monoclonal antibodies has become routine in research and diagnostic laboratories but the potential level of antibodies in use in public health and medical applications is still far from its maximum. From a clinical perspective, topical immunotherapy of mucosal surfaces with monoclonal antibodies can block entry and transmission of bacteria, viruses, fungi and parasites that infect humans, and defeat some key strategies, evolved by many pathogens, to evade the host immune system. The chief antibody at mucosal surfaces is secretory immunoglobulin A (SIgA), a multi-polypeptide complex originating from two cell types. The recent design of heterologous expression systems, coupled with modern biotechnology processes, should form a sound basis for studying the functional properties of SIgAs and evaluate their value as biotherapeutics. Here, we discuss the principles underlying mucosal immunity and review the application of recombinant SIgA to the dissection of mechanisms in passive and active protection at mucosal surfaces.

Animals↗