Zonula occludens toxin acts as an adjuvant through different mucosal routes and induces protective immune responses

Phylogenetic Tracing of Evolutionarily Conserved Zonula Occludens Toxin Reveals a "High Value" Vaccine Candidate Specific for Treating Multi-Strain Pseudomonas aeruginosa Infections

Extensively drug-resistant Pseudomonas aeruginosa infections are emerging as a significant threat associated with adverse patient outcomes. Due to this organism's inherent properties of developing antibiotic resistance, we sought to investigate alternative strategies such as identifying "high value" antigens for immunotherapy-based purposes. Through extensive database mining, we discovered that numerous Gram-negative bacterial (GNB) genomes, many of which are known multidrug-resistant (MDR) pathogens, including P. aeruginosa, horizontally acquired the evolutionarily conserved gene encoding Zonula occludens toxin (Zot) with a substantial degree of homology. The toxin's genomic footprint among so many different GNB stresses its evolutionary importance. By employing in silico techniques such as proteomic-based phylogenetic tracing, in conjunction with comparative structural modeling, we discovered a highly conserved intermembrane associated stretch of 70 amino acids shared among all the GNB strains analyzed. The characterization of our newly identified antigen reveals it to be a "high value" vaccine candidate specific for P. aeruginosa. This newly identified antigen harbors multiple non-overlapping B- and T-cell epitopes exhibiting very high binding affinities and can adopt identical tertiary structures among the least genetically homologous P. aeruginosa strains. Taken together, using proteomic-driven reverse vaccinology techniques, we identified multiple "high value" vaccine candidates capable of eliciting a polarized immune response against all the P. aeruginosa genetic variants tested.

Zonulin — regulation of tight contacts in the brain and intestine — facts and hypotheses

In recent years, the interrelationship between the brain and the gut has become an area of high scientific interest. The intestine is responsible not only for digestion, as it contains millions of neurons, its own immune system, and affects the emotional and cognitive processes. The relationship between the gut and the brain suggests that the processes carried out by the gut microbiota play a significant role in the regulation of brain function, and vice versa. A special role here is played by intercellular tight junctions (TJ), where the zonulin protein holds an important place. Zonulin, an unprocessed precursor of mature haptoglobin, is the only physiological modulator of intercellular TJ that can reversibly regulate the permeability of the intestinal (IB) and blood-brain (BBB) barriers in the human body. BBB disruption and altered microbiota composition are associated with many diseases, including neurological disorders and neuroinflammation. That is, there is a gut-brain axis (GBA) — a communication system through which the brain modulates the functions of the gastrointestinal tract (GIT) and vice versa. GBA is based on neuronal, endocrine, and immunological mechanisms that are interconnected at the organismal, organ, cellular, and molecular levels.

Oral drug delivery for immunoengineering

The systemic pharmacotherapeutic efficacy of immunomodulatory drugs is heavily influenced by its route of administration. A few common routes for the systemic delivery of immunotherapeutics are intravenous, intraperitoneal, and intramuscular injections. However, the development of novel biomaterials, in adjunct to current progress in immunoengineering, is providing an exciting area of interest for oral drug delivery for systemic targeting. Oral immunotherapeutic delivery is a highly preferred route of administration due to its ease of administration, higher patient compliance, and increased ability to generate specialized immune responses. However, the harsh environment and slow systemic absorption, due to various biological barriers, reduces the immunotherapeutic bioavailability, and in turn prevents widespread use of oral delivery. Nonetheless, cutting edge biomaterials are being synthesized to combat these biological barriers within the gastrointestinal (GI) tract for the enhancement of drug bioavailability and targeting the immune system. For example, advancements in biomaterials and synthesized drug agents have provided distinctive methods to promote localized drug absorption for the modulation of local or systemic immune responses. Additionally, novel breakthroughs in the immunoengineering field show promise in the development of vaccine delivery systems for disease prevention as well as combating autoimmune diseases, inflammatory diseases, and cancer. This review will discuss current progress made within the field of biomaterials and drug delivery systems to enhance oral immunotherapeutic availability, and how these new delivery platforms can be utilized to deliver immunotherapeutics for resolution of immune-related diseases.

Application of red clover isoflavone extract as an adjuvant in mice

In the present study, the safety of red clover isoflavone extract (RCIE) and its potential adjuvant effects on the cellular and humoral immune responses to ovalbumin (OVA) were evaluated using an ICR mouse model. On day 1, the mice were first subcutaneously immunized with 100 µg OVA, 100 µg OVA + 200 µg aluminum hydroxide gel (alum) or OVA + 50, 100 or 200 µg RCIE (RCIE + OVA), following which booster immunization was performed on day 15. After 2 weeks, the stimulation of splenocyte proliferation and levels of serum antibodies were measured. No notable stress responses were observed after the initial and booster immunization. Splenocyte proliferation was significantly increased in mice immunized with OVA + 100 µg RCIE (P<0.01). The levels of IgG, IgG1 and IgG2a antibodies in serum were also significantly increased in OVA + RCIE groups compared with the OVA control group (P<0.05). In the OVA + RCIE groups, serum levels of interleukin (IL)-2, interferon-γ (IFN-γ) and IL-10 were increased, and the mRNA expression levels of IL-2, IFN-γ, IL-4, IL-10, T-bet and GATA-3 were also significantly increased compared with the OVA control group (P<0.05) in splenocytes. In addition, as an adjuvant, RCIE significantly increased the survival rates of mice inoculated with an E. coli vaccine and enhanced the early immune protection against pathogenic E. coli. In conclusion, these findings suggest that RCIE can be used as a safe vaccine adjuvant and supports its use in clinical applications.

Intranasal co-administration of recombinant active fragment of Zonula occludens toxin and truncated recombinant EspB triggers potent systemic, mucosal immune responses and reduces span of E. coli O157:H7 fecal shedding in BALB/c mice

Escherichia coli O157:H7 with its traits such as intestinal colonization and fecal-oral route of transmission demands mucosal vaccine development. E. coli secreted protein B (EspB) is one of the key type III secretory system (TTSS) targets for mucosal candidate vaccine due to its indispensable role in the pathogenesis of E. coli O157:H7. However, mucosally administered recombinant proteins have low immunogenicity which could be overcome by the use of mucosal adjuvants. The quest for safe, potent mucosal adjuvant has recognized ΔG fragment of Zonula occludens toxin of Vibrio cholerae with such properties. ΔG enhances mucosal permeability via the paracellular route by altering epithelial tight junction structure in a reversible, ephemeral and non-toxic manner. Therefore, we tested whether recombinant ΔG intranasally co-administered with truncated EspB (EspB + ΔG) could serve as an effective mucosal adjuvant. Results showed that EspB + ΔG group induced higher systemic IgG and mucosal IgA than EspB alone. Moreover, EspB alone developed Th2 type response with IgG1/IgG2a ratio (1.64) and IL-4, IL-10 cytokines whereas that of EspB + ΔG group generated mixed Th1/Th2 type immune response evident from IgG1/IgG2a ratio (1.17) as well as IL-4, IL-10 and IFN-γ cytokine levels compared to control. Sera of EspB + ΔG group inhibited TTSS mediated haemolysis of murine RBCs more effectively compared to EspB, control group and sera of both EspB + ΔG, EspB group resulted in similar levels of efficacious reduction in E. coli O157:H7 adherence to Caco-2 cells compared to control. Moreover, vaccination with EspB + ΔG resulted in significant reduction in E. coli O157:H7 fecal shedding compared to EspB and control group in experimentally challenged streptomycin-treated mice. These results demonstrate mucosal adjuvanticity of ΔG co-administered with EspB in enhancing overall immunogenicity to reduce E. coli O157:H7 shedding.

Intranasal immunization of cocktail/fusion protein containing Tir along with ΔG active fragment of Zot as mucosal adjuvant confers enhanced immunogenicity and reduces E. coli O157:H7 shedding in mice

Ruminants are the major reservoirs of Escherichia coli O157:H7 and its fecal shedding mainly act as a source of entry of this pathogen into the human food chain. In humans, E. coli O157:H7 infection causes diarrhea, hemorrhagic colitis and hemolytic uremic syndrome. Intimate adherence of E. coli O157:H7 is mediated by Translocated intimin receptor (Tir) to which intimin binds in the host cell. Since E. coli O157:H7 colonizes intestinal epithelium, the mucosal vaccine has a potential to prevent its colonization. Zonula occludens toxin (Zot) of Vibrio cholerae transiently, reversibly alters epithelial tight junction structure to increase mucosal permeability of macromolecules via paracellular route. The C-terminal region of Zot (ΔG) responsible for this function could be used for mucosal antigen delivery. Therefore, we employed individual (Tir), cocktail (ΔG + Tir), fusion protein (ΔG-Tir) and assessed the efficacy of its intranasal immunization on immunogenicity and fecal shedding of E. coli O157:H7 in streptomycin treated mouse model. Compared to control, ΔG + Tir, ΔG-Tir immunized mice elicited significant antigen specific antibody titers in serum (IgG, IgA) and feces (IgA), whereas Tir immunized mice induced only serum IgG titer. Cytokine analysis revealed mixed Th1/Th2 type immune response in case of ΔG + Tir, ΔG-Tir group while that of Tir group was solely Th2 type. Tir, ΔG + Tir and ΔG-Tir immunized mice showed reduction in shedding of E. coli O157:H7 compared to control group. However, ΔG-Tir immunized group performed better than ΔG + Tir, Tir group in reducing fecal shedding. Overall, our results demonstrate that intranasal immunization of ΔG-Tir induces effective systemic, mucosal, cellular immune responses and represents a promising mucosal subunit vaccine to prevent E. coli O157:H7 colonization.

Microbiota Composition and the Integration of Exogenous and Endogenous Signals in Reactive Nasal Inflammation

The prevalence of reactive nasal inflammatory conditions, for example, allergic rhinitis and chronic rhinosinusitis, is steadily increasing in parallel with significant environmental changes worldwide. Allergens and as yet undefined environmental agents may trigger these conditions via the involvement of host intrinsic factors, including the innate and adaptive immune system, the nasal epithelium, and the nasal nervous system. The critical role of the nasal microbiota in coordinating these components has emerged in recent studies documenting a significant association between microbial composition and the onset and progression of allergic or nonallergic inflammation. It is now clear that the local microbiota is a major player in the development of the mucosa-associated lymphoid tissue and in the regulation of such adaptive responses as IgA production and the function of effector and regulatory T cells. Microbial components also play a major role in the regulation of epithelial barrier functions, including mucus production and the control of paracellular transport across tight junctions. Bacterial components, including lipopolysaccharide, have also been shown to induce or amplify neuroinflammatory responses by engaging specific nociceptors. Finally, bacterial products may promote tissue remodeling processes, including nasal polyp formation, by interacting with formyl peptide receptors and inducing the expression of angiogenic factors and matrix-degrading enzymes.

Exploring the Genomic Traits of Non-toxigenic Vibrio parahaemolyticus Strains Isolated in Southern Chile

Vibrio parahaemolyticus is the leading cause of seafood-borne gastroenteritis worldwide. As reported in other countries, after the rise and fall of the pandemic strain in Chile, other post-pandemic strains have been associated with clinical cases, including strains lacking the major toxins TDH and TRH. Since the presence or absence of tdh and trh genes has been used for diagnostic purposes and as a proxy of the virulence of V. parahaemolyticus isolates, the understanding of virulence in V. parahaemolyticus strains lacking toxins is essential to detect these strains present in water and marine products to avoid possible food-borne infection. In this study, we characterized the genome of four environmental and two clinical non-toxigenic strains (tdh-, trh-, and T3SS2-). Using whole-genome sequencing, phylogenetic, and comparative genome analysis, we identified the core and pan-genome of V. parahaemolyticus of strains of southern Chile. The phylogenetic tree based on the core genome showed low genetic diversity but the analysis of the pan-genome revealed that all strains harbored genomic islands carrying diverse virulence and fitness factors or prophage-like elements that encode toxins like Zot and RTX. Interestingly, the three strains carrying Zot-like toxin have a different sequence, although the alignment showed some conserved areas with the zot sequence found in V. cholerae. In addition, we identified an unexpected diversity in the genetic architecture of the T3SS1 gene cluster and the presence of the T3SS2 gene cluster in a non-pandemic environmental strain. Our study sheds light on the diversity of V. parahaemolyticus strains from the southern Pacific which increases our current knowledge regarding the global diversity of this organism.

Comparative Genome Analyses of Vibrio anguillarum Strains Reveal a Link with Pathogenicity Traits

Comparative genome analysis of strains of a pathogenic bacterial species can be a powerful tool to discover acquisition of mobile genetic elements related to virulence. Here, we compared 28 V. anguillarum strains that differed in virulence in fish larval models. By pan-genome analyses, we found that six of nine highly virulent strains had a unique core and accessory genome. In contrast, V. anguillarum strains that were medium to nonvirulent had low genomic diversity. Integration of genomic and phenotypic features provides insights into the evolution of V. anguillarum and can also be important for survey and diagnostic purposes.

Vibrio anguillarum is a marine bacterium that can cause vibriosis in many fish and shellfish species, leading to high mortalities and economic losses in aquaculture. Although putative virulence factors have been identified, the mechanism of pathogenesis of V. anguillarum is not fully understood. Here, we analyzed whole-genome sequences of a collection of V. anguillarum strains and compared them to virulence of the strains as determined in larval challenge assays. Previously identified virulence factors were globally distributed among the strains, with some genetic diversity. However, the pan-genome revealed that six out of nine high-virulence strains possessed a unique accessory genome that was attributed to pathogenic genomic islands, prophage-like elements, virulence factors, and a new set of gene clusters involved in biosynthesis, modification, and transport of polysaccharides. In contrast, V. anguillarum strains that were medium to nonvirulent had a high degree of genomic homogeneity. Finally, we found that a phylogeny based on the core genomes clustered the strains with moderate to no virulence, while six out of nine high-virulence strains represented phylogenetically separate clusters. Hence, we suggest a link between genotype and virulence characteristics of Vibrio anguillarum, which can be used to unravel the molecular evolution of V. anguillarum and can also be important from survey and diagnostic perspectives.

IMPORTANCE Comparative genome analysis of strains of a pathogenic bacterial species can be a powerful tool to discover acquisition of mobile genetic elements related to virulence. Here, we compared 28 V. anguillarum strains that differed in virulence in fish larval models. By pan-genome analyses, we found that six of nine highly virulent strains had a unique core and accessory genome. In contrast, V. anguillarum strains that were medium to nonvirulent had low genomic diversity. Integration of genomic and phenotypic features provides insights into the evolution of V. anguillarum and can also be important for survey and diagnostic purposes.

Celiac disease: the search for adjunctive or alternative therapies

Celiac disease is a widespread disorder caused by intolerance to gluten, a common protein in food. Currently, a life-long gluten-free diet is the only available treatment for patients with celiac disease. However, adherence to gluten-free diet is difficult due to the widespread use of wheat-derived gluten in the food industry. Therefore, there is a pressing need for the development of novel non-dietary therapies. In this article, we will review several promising strategies focusing on reducing gluten immunogenicity or sequestering to gluten prevent its uptake by the intestinal epithelium. Other possible treatment strategies that will be reviewed include the suppression of the adaptive immune response, permeability modulation and the use of systemic T-cell or cytokine blockers.

Larazotide acetate promotes tight junction assembly in epithelial cells

Tight junctions (TJ) control paracellular permeability and apical-basolateral polarity of epithelial cells. Dysregulated permeability is associated with pathological conditions, such as celiac disease and inflammatory bowel disease. TJ formation is dependent on E-cadherin-mediated cell-cell adhesion and actin rearrangement, and is regulated by the Rho family GTPase and aPKC signaling pathways. Larazotide acetate, an 8-mer peptide and TJ modulator, inhibits TJ disassembly and dysfunction caused by endogenous and exogenous stimuli in intestinal epithelial cells. Here, we examined the effect of larazotide acetate on de novo TJ assembly using 2 different model systems. In MDCK cells, larazotide acetate promoted TJ assembly in a calcium switch assay. Larazotide acetate also promoted actin rearrangement, and junctional distribution of zonula occludens-1 (ZO-1), occludin, claudins, and E-cadherin. Larazotide acetate promoted TJ maturation and decreased paracellular permeability in "leaky" Caco-2 cells. Taken together, our data indicate that larazotide acetate enhances TJ assembly and barrier function by promoting actin rearrangement and redistribution of TJ and AJ proteins.

Larazotide acetate regulates epithelial tight junctions in vitro and in vivo

Tight junctions (TJs) control paracellular permeability and apical-basolateral polarity of epithelial cells, and can be regulated by exogenous and endogenous stimuli. Dysregulated permeability is associated with pathological conditions, such as celiac disease and inflammatory bowel disease. Herein we studied the mechanism by which larazotide acetate, an 8-mer peptide and TJ regulator, inhibits the cellular changes elicited by gliadin fragments, AT-1002, and cytokines. Previously, we demonstrated that AT-1002, a 6-mer peptide derived from the Vibrio cholerae zonula occludens toxin ZOT, caused several biochemical changes in IEC6 and Caco-2 cells resulting in decreased transepithelial electrical resistance (TEER) and increased TJ permeability. In this study, larazotide acetate inhibited the redistribution and rearrangement of zonula occludens-1 (ZO-1) and actin caused by AT-1002 and gliadin fragments in Caco-2 and IEC6 cells. Functionally, larazotide acetate inhibited the AT-1002-induced TEER reduction and TJ opening in Caco-2 cells. Additionally, larazotide acetate inhibited the translocation of a gliadin 13-mer peptide, which has been implicated in celiac disease, across Caco-2 cell monolayers. Further, apically applied larazotide acetate inhibited the increase in TJ permeability elicited by basolaterally applied cytokines. Finally, when tested in vivo in gliadin-sensitized HLA-HCD4/DQ8 double transgenic mice, larazotide acetate inhibited gliadin-induced macrophage accumulation in the intestine and preserved normal TJ structure. Taken together, our data suggest that larazotide acetate inhibits changes elicited by AT-1002, gliadin, and cytokines in epithelial cells and preserves TJ structure and function in vitro and in vivo.

Non-dietary therapeutic clinical trials in coeliac disease

Coeliac disease is a permanent immunological intolerance to gluten proteins in genetically predisposed individuals. The only management is life-long strict adherence to a gluten-free diet. Unfortunately, compliance with gluten-free diet is very difficult in practice due to the widespread presence of gluten in Western diets. For this reason, about 50% of coeliacs following a gluten-free diet continue to suffer from symptoms and present with autoantibodies and/or villous atrophy while on a gluten-free diet. It is therefore important to explore new therapies to improve the management of coeliac disease. To date, five experimental therapies have been tested in randomized and controlled clinical trials. Larazotide acetate reduces the para-cellular passage of gluten to the lamina propria by preventing the opening of intercellular tight junctions. The endopeptidases ALV003 and AN-PEP break down gluten to produce less or non-toxic peptide fragments. A therapeutic vaccine is being tested with the aim of developing gluten tolerance. Finally, infection with the nematode Necator americanus and treatment with the CCR9 antagonist Traficet-EN have also been reported. While substantial progress has been made in the last few years, it is important to remember that all these investigational therapies are in research stage and are generally being considered as "adjunctive" therapies to the gluten-free diet and not as substitutes of the gluten-free diet at this point in time.

The influence of AT1002 on the nasal absorption of molecular weight markers and therapeutic agents when co-administered with bioadhesive polymers and an AT1002 antagonist, AT1001

OBJECTIVES

The purpose of this study was to demonstrate the effects of the tight junction permeation enhancer, AT1002, on the nasal absorption of molecular weight markers and low bioavailable therapeutic agents co-administered with bioadhesive polymers or zonulin antagonist.

METHODS

The bioadhesive polymers, carrageenan and Na-CMC, were prepared with AT1002 to examine the permeation-enhancing effect of AT1002 on the nasal absorption of inulin, calcitonin and saquinavir after nasal administration to Sprague-Dawley rats. Blood samples were collected over a 6-hour period from a jugular cannula. In addition, we determined whether AT1002 exerts a permeation-enhancing effect via activation of PAR-2 specific binding to a putative receptor of zonulin. To examine this zonulin antagonist, AT1001, was administered 30 min prior to dosing with an AT1002/inulin solution and blood samples were collected over a 6-hour period.

KEY FINDINGS

The bioadhesive polymers did not directly increase the absorption of inulin, calcitonin and saquinavir, but promoted the permeation-enhancing effect of AT1002 when delivered nasally, thereby significantly increasing the absorption of each drug. Pre-treatment with AT1001 antagonized the zonulin receptor and significantly minimized the permeation-enhancing effect of AT1002.

CONCLUSION

These findings will assist in understanding the permeation-enhancing capability of and the receptor binding of AT1002. Further, combining AT1002 with carrageenan supports the development of the mucosal delivery of therapeutic agents that have low bioavailability even with bioadhesive agents.

Modulation of immunogenicity and immunoprotection of mucosal vaccine against coxsackievirus B3 by optimizing the coadministration mode of lymphotactin adjuvant

Induction of potent mucosal immune response is a goal of current vaccine strategies against mucus-infectious pathogens such as Coxsackievirus B3 type (CVB3). We previously showed that administration of lymphotactin (LTN) as an adjuvant could enhance the specific immune responses against a mucosal gene vaccine, chitosan-pVP1, against CVB3. To optimize the coadministration mode of the mucosal adjuvant, we compared the mucosal immune responses induced by chitosan-DNA vaccine with different combinations of the target VP1 antigen gene and the adjuvant LTN gene. The two genes were either cloned in separate vectors or coexpressed as a fusion or bicistron protein in the same vector before encapsulation in chitosan nanoparticles. Four doses of various adjuvant-combined chitosan-DNA were intranasally administrated to mice before challenge with CVB3. The results indicated that chitosan-formulated pVP1-LTN fusion plasmid exhibited very weak improvement of CVB3-specific immune responses. Although the bicistronic coexpression of LTN with VP1 was expected to be powerful, this combination had enhanced effects on serum IgG and systemic T cell immune responses, but not on mucosal T cell immunity. Coimmunization with VP1 and LTN as separate chitosan-DNA formulation remarkably enhanced antibody and T cell immune responses both in systemic and mucosal immune compartments, leading to the most desirable preventive effect on viral myocarditis. Taken together, how the adjuvant is combined with the target antigen has a strong influence on the mucosal immune responses induced by mucosal DNA vaccines.

Expression of Zonulin, c-kit, and Glial Fibrillary Acidic Protein in Human Gliomas

The hallmarks of human malignant gliomas are their marked invasiveness and vascularity. Because angiogenesis and tumor invasion have been associated with extracellular matrix degradation and intercellular tight junctions, the involvement of zonulin in glioma biology is in the focus. We selected for histological examination five cases of glioblastoma WHO IV (nomenclature of the World Health Organization) and one case each from astrocytoma WHO III, meningioma WHO III, and meningioma WHO I as control samples. The meningioma WHO I is regarded as benign, whereas the meningioma WHO III is recognized as the transition form of malignant tumors in humans. The visualization of a newly designed antibody against human zonulin was studied in triple-labeling studies using fluorescence immunocytochemistry and compared with the expression of c-kit and glial fibrillary acidic protein in differently developed human gliomas. We found that increasing the expression of c-kit is accompanied by an increase of zonulin expression. Both are correlated to the degree of malignancy of human brain tumors. The expression of zonulin is correlated to the degradation of the blood-brain barrier as revealed by Griffonia simplicifolia lectin. In differently graded tumors, we found differently graded involvement of blood vessels in the tumor development, explaining patients' survival.

Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer

The primary functions of the gastrointestinal tract have traditionally been perceived to be limited to the digestion and absorption of nutrients and to electrolytes and water homeostasis. A more attentive analysis of the anatomic and functional arrangement of the gastrointestinal tract, however, suggests that another extremely important function of this organ is its ability to regulate the trafficking of macromolecules between the environment and the host through a barrier mechanism. Together with the gut-associated lymphoid tissue and the neuroendocrine network, the intestinal epithelial barrier, with its intercellular tight junctions, controls the equilibrium between tolerance and immunity to non-self antigens. Zonulin is the only physiological modulator of intercellular tight junctions described so far that is involved in trafficking of macromolecules and, therefore, in tolerance/immune response balance. When the finely tuned zonulin pathway is deregulated in genetically susceptible individuals, both intestinal and extraintestinal autoimmune, inflammatory, and neoplastic disorders can occur. This new paradigm subverts traditional theories underlying the development of these diseases and suggests that these processes can be arrested if the interplay between genes and environmental triggers is prevented by reestablishing the zonulin-dependent intestinal barrier function. This review is timely given the increased interest in the role of a "leaky gut" in the pathogenesis of several pathological conditions targeting both the intestine and extraintestinal organs.

Subcutaneous and intranasal immunization with Stx2B-Tir-Stx1B-Zot reduces colonization and shedding of Escherichia coli O157:H7 in mice

The type III secretion system of Escherichia coli O157:H7 is involved in colonization of mammalian hosts by the organism. The translocated intimin receptor (Tir) is inserted into the mammalian host cell plasma membrane in a hairpin loop topology with the central loop of the molecule exposed to the host cell surface and accessible for interaction with an LEE-encoded bacterial outer membrane adhesin called intimin. Shiga toxin type 1 and 2 produced by E. coli O157:H7 are responsible for hemolytic uremic syndrome and able to promote intestinal colonization. Zonula occludens toxin (Zot) is a single polypeptide chain encoded by the filamentous bacteriophage CTXφ of Vibrio cholerae. Zot binds a receptor on intestinal epithelial cells and increases mucosal permeability by affecting the structure of epithelial tight junctions. Because of these properties, Zot is a promising tool for mucosal drug and antigen (Ag) delivery. In the current study, we constructed a novel fusion protein carrying both of the immunogenic B subunits derived from the two toxins, Tir and Zot, designated Stx2B-Tir-Stx1B-Zot, expressed in the E. coli BL21 and harvested the purified protein by a simple GST·Bind Resin chromatography method. We used a streptomycin-treated mouse model to evaluate the efficacy of subcutaneous vs. intranasal administration of the vaccine. Following immunization, mice were infected with E. coli O157:H7 and feces were monitored for shedding. Immune responses against Stx2B-Tir-Stx1B-Zot, Stx2B-Tir-Stx1B and control agent (GST/PBS) were also monitored. Subcutaneous immunization of mice with Stx2B-Tir-Stx1B-Zot induced significant Stx2B-Tir-Stx1B-Zot-specific serum IgG antibodies but did not significantly induce any antigen-specific IgA in feces, whereas intranasal immunization elicited significant Stx2B-Tir-Stx1B-Zot-specific serum IgG antibodies with some animals developing antigen-specific IgA in feces. Mice that were immunized intranasally with Stx2B-Tir-Stx1B-Zot showed dramatically decreased E. coli O157:H7 shedding compared to those of Stx2B-Tir-Stx1B and control agent following experimental infection. Mice immunized subcutaneously with Stx2B-Tir-Stx1B-Zot or Stx2B-Tir-Stx1B both showed reduced shedding in feces, moreover, Stx2B-Tir-Stx1B-Zot did better. These results demonstrate the perspective for the use of Stx2B-Tir-Stx1B-Zot to prevent colonization and shedding of E. coli O157:H7.

Rotavirus enterotoxin NSP4 has mucosal adjuvant properties

Rotavirus nonstructural protein 4 (NSP4) is a protein with pleiotropic properties. It functions in rotavirus morphogenesis, pathogenesis, and is the first described viral enterotoxin. Since many bacterial toxins function as potent mucosal adjuvants, we evaluated whether baculovirus-expressed recombinant simian rotavirus SA11 NSP4 possesses adjuvant activity by co-administering NSP4 with keyhole limpet hemocyanin (KLH), tetanus toxoid (TT) or ovalbumin (OVA) as model antigens in mice. Following intranasal immunization, NSP4 significantly enhanced both systemic and mucosal immune responses to model immunogens, as compared to the control group, in an antigen-specific manner. Both full-length and a cleavage product of SA11 NSP4 had adjuvant activity, localizing this activity to the C-terminus of the protein. NSP4 forms from virulent and avirulent porcine rotavirus OSU strain, and SA11 NSP4 localized within a 2/6-virus-like particle (VLP) also exhibited adjuvant effects. These studies suggest that the rotavirus enterotoxin NSP4 can function as an adjuvant to enhance immune responses for a co-administered antigen.

Novel mucosal vaccines generated by genetic conjugation of heterologous proteins to pneumolysin (PLY) from Streptococcus pneumoniae

Induction of immunity at mucosal surfaces is thought to be an essential feature in the protection of the host against the many pathogens that gain access through these surfaces. Here we describe how strong local and systemic immune responses can be generated when proteins are genetically conjugated to pneumolysin (PLY) from Streptococcus pneumoniae. Using green fluorescent protein (eGFP) and PsaA from S. pneumoniae, we have shown that genetic fusion (eGFPPLY and PsaAPLY) is essential to ensure high levels of antigen specific IgG and IgA in the serum and at mucosal surfaces. This form of vaccination is highly effective with antigen specific antibodies detected after a single dose of nanogram quantities of the conjugated proteins. In addition, generation of a non-toxic variant (eGFPDelta6PLY) indicated that while the toxic activity of PLY was not essential for adjuvanticity, it contributed to the magnitude of the response generated. Whilst vaccination with the PsaAPLY fusion proteins did not protect the animals from challenge, these studies confirm the utility of pneumolysin to act as a novel mucosal adjuvant to substantially increase the local and systemic humoral response to genetically fused protein antigens.

Physiological, pathological, and therapeutic implications of zonulin-mediated intestinal barrier modulation: living life on the edge of the wall

The anatomical and functional arrangement of the gastrointestinal tract suggests that this organ, beside its digestive and absorptive functions, regulates the trafficking of macromolecules between the environment and the host through a barrier mechanism. Under physiological circumstances, this trafficking is safeguarded by the competency of intercellular tight junctions, structures whose physiological modulation is mediated by, among others, the recently described protein zonulin. To prevent harm and minimize inflammation, the same paracellular pathway, in concert with the gut-associated lymphoid tissue and the neuroendocrine network, controls the equilibrium between tolerance and immunity to nonself antigens. The zonulin pathway has been exploited to deliver drugs, macromolecules, or vaccines that normally would not be absorbed through the gastrointestinal mucosal barrier. However, if the tightly regulated trafficking of macromolecules is jeopardized secondary to prolonged zonulin up-regulation, the excessive flow of nonself antigens in the intestinal submucosa can cause both intestinal and extraintestinal autoimmune disorders in genetically susceptible individuals. This new paradigm subverts traditional theories underlying the development of autoimmunity, which are based on molecular mimicry and/or the bystander effect, and suggests that the autoimmune process can be arrested if the interplay between genes and environmental triggers is prevented by re-establishing intestinal barrier competency. Understanding the role of zonulin-dependent intestinal barrier dysfunction in the pathogenesis of autoimmune diseases is an area of translational research that encompasses many fields.

Innate Immunity in the Female Reproductive Tract: Role of Sex Hormones in Regulating Uterine Epithelial Cell Protection Against Pathogens

The mucosal immune system in the upper female reproductive tract is uniquely prepared to maintain a balance between the presence of commensal bacteria, sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and an immunologically distinct fetus. At the center of this dynamic system are the epithelial cells that line the Fallopian tubes, uterus, cervix and vagina. Epithelial cells provide a first line of defense that confers continuous protection, by providing a physical barrier as well as secretions containing bactericidal and virucidal agents. In addition to maintaining a state of ongoing protection, these cells have evolved to respond to pathogens, in part through Toll-like receptors (TLRs), to enhance innate immune protection and, when necessary, to contribute to the initiation of an adaptive immune response. Against this backdrop, epithelial cell innate and adaptive immune function is modulated to meet the constraints of procreation. The overall goal of this review is to focus on the dynamic role of epithelial cells in the upper reproductive tract, with special emphasis on the uterus, to define the unique properties of these cells as they maintain homeostasis in preparation for successful fertilization and pregnancy while at the same time confer protection against sexually transmitted infections, which threaten to compromise women's reproductive health and survival. By understanding the nature of this protection and the ways in which innate and adaptive immunity are regulated by sex hormones, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

The safety, tolerance, pharmacokinetic and pharmacodynamic effects of single doses of AT-1001 in coeliac disease subjects: a proof of concept study

BACKGROUND

Lifelong adherence to a strict gluten-free diet is the cornerstone of coeliac disease treatment. Elucidation of disease pathogenesis has created opportunities for novel therapeutic approaches to coeliac disease. AT-1001 is an inhibitor of paracellular permeability whose structure is derived from a protein secreted by Vibrio cholerae.

AIM

To determine the safety and tolerability of 12 mg doses of AT-1001 in coeliac disease subjects challenged with gluten.

METHODS

An in-patient, double-blind, randomized placebo-controlled safety study utilizing intestinal permeability, measured via fractional excretions of lactulose and mannitol, as an exploratory measure of drug efficacy.

RESULTS

Compared to placebo, no increase in adverse events occurred in patients exposed to AT-1001. Following acute gluten exposure, a 70% increase in intestinal permeability was detected in the placebo group, while none was seen in the AT-1001 group. Interferon-gamma levels increased in four of seven patients (57%) of the placebo group, but only in four of 14 patients (29%) of the AT-1001 group. Gastrointestinal symptoms were more frequently detected in the placebo group when compared to the AT-1001 group (P = 0.018).

CONCLUSIONS

AT-1001 is well tolerated and appears to reduce intestinal barrier dysfunction, proinflammatory cytokine production, and gastrointestinal symptoms in coeliacs after gluten exposure.

Delivery systems and adjuvants for oral vaccines

The oral route is the ideal means of delivering prophylactic and therapeutic vaccines, offering significant advantages over systemic delivery. Most notably, oral delivery is associated with simple administration and improved safety. In addition, unlike systemic immunisation, oral delivery can induce mucosal immune responses. However, the oral route of vaccine delivery is the most difficult because of the numerous barriers posed by the gastrointestinal tract. To facilitate effective immunisation with peptide and protein vaccines, antigens must be protected, uptake enhanced and the innate immune response activated. Numerous delivery systems and adjuvants have been evaluated for oral vaccine delivery, including live vectors, inert particles and bacterial toxins. Although developments in oral vaccines have been disappointing so far, in terms of the generation of products, the availability of a range of novel delivery systems offers much greater hope for the future development of improved oral vaccines.

Zonula occludens toxin as a new promising adjuvant for mucosal vaccines

Cholera toxin (CT) and CT-related molecules have been known since a long time to act as powerful mucosal adjuvants. We have studied the stimulatory effects of CT on human dendritic cells and its inhibitory activity on T lymphocytes. We have also identified a third bacterial enterotoxin, Zonula occludens toxin (Zot) that acts as an effective mucosal adjuvant. Zonula occludens toxin is produced by Vibrio cholerae and has the property to increase intestinal mucosa permeability by reversibly affecting the structure of tight junctions. We found that recombinant ZOT induces long lasting and protective immunity to intranasally delivered antigens and is effective also through other mucosal routes. Furthermore, ZOT is highly efficacious when compared to the mucosal adjuvant LT (Escherichia coli heat-labile enterotoxin) but has a much lower immunogenicity. By using an octapeptide representing the putative binding site of Zot and of its endogenous analogue Zonulin, we provided evidence that Zot may bind a receptor on the nasal mucosa and may mimic an endogenous regulator of tight junctions to deliver antigens in the submucosa. Finally, we are testing recombinant fragments of ZOT for their mucosal adjuvant activity. In conclusion, Zot and its derivatives are very promising tools for the development of needle-free mucosal vaccines.

Celiac disease: a multisystem autoimmune disorder

Just a few years ago, celiac disease was thought to be relatively rare in the United States, but recent data suggest celiac disease may affect 3 million Americans of all ages, many of whom have no diagnosis of the disease. With increased awareness of this disease among adult and pediatric primary care providers, there undoubtedly will be an increase in the number of persons being evaluated for celiac disease in outpatient diagnostic centers and gastroenterology practices. Gastroenterology nurses, therefore, need to have a thorough understanding of celiac disease to fully participate as members of the multidisciplinary team required to manage this challenging disease. This article discusses the pathogenesis, prevalence, diagnosis, clinical manifestations, management, and complications of celiac disease.

Critical Role of Tight Junctions in Drug Delivery across Epithelial and Endothelial Cell Layers

Epithelia in multicellular organisms constitute the frontier that separates the individual from the environment. Epithelia are sites of exchange as well as barriers, for the transit of ions and molecules from and into the organism. Therapeutic agents, in order to reach their target, frequently need to cross epithelial and endothelial sheets. Two routes are available for such purpose: the transcellular and the paracellular pathways. The former is employed by lipophilic drugs and by molecules selectively transported by channels, pumps and carriers present in the plasma membrane. Hydrophilic molecules cannot cross biological membranes, therefore their transepithelial transport could be significantly enhanced if they moved through the paracellular pathway. Transit through this route is regulated by tight junctions (TJs). The discovery in recent years of the molecular mechanisms of the TJ has allowed the design of different procedures to open the paracellular route in a reversible manner. These strategies could be used to enhance drug delivery across epithelial and endothelial barriers. The procedures employed include the use of peptides homologous to external loops of integral TJ proteins, silencing the expression of TJ proteins with antisense oligonucleotides and siRNAs as well as the use of toxins and proteins derived from microorganisms that target TJ proteins.