Modulation of intestinal tight junctions by Zonula occludens toxin permits enteral administration of insulin and other macromolecules in an animal model

Zonula occludens toxin increases the permeability of molecular weight markers and chemotherapeutic agents across the bovine brain microvessel endothelial cells

The purpose of this study was to examine the ability of Zonula occludens toxin (Zot) to reversibly open tight junctions in bovine brain microvessel endothelial cells (BBMECs) to enhance drug delivery via the paracellular pathway. Transport across BBMEC monolayers was examined for molecular weight markers and chemotherapeutic agents ([(14)C]sucrose, [(14)C]inulin, [(3)H]propranolol, [(3)H]doxorubicin, and [(14)C]paclitaxel) with Zot (0.0-4.0 microg/mL). TEER of monolayers was measured to assess effect and reversibility of Zot. Cell viability of BBMEC in the presence of Zot was assessed by trypan blue exclusion staining. Apparent permeability (P(app)), enhancement ratio (R), and percent increase in transport determined were statistically compared by ANOVA. A significant increase (p < 0.05) in P(app) was observed for the transport of [(14)C]sucrose, [(14)C]inulin, [(3)H]doxorubicin, and [(14)C]paclitaxel at a 4.0 microg/mL concentration of Zot. A significant concentration-dependent decrease in TEER was observed on treatment with Zot with rapid reversal to baseline after removal. Zot (4 micro/ml) was found to be nontoxic to the BBMECs after 2 hours incubation. In conclusion, Zot increased paracellular transport across the BBMEC in a reversible, concentration-dependent manner. Modulation of paracellular transport with Zot may be used to increase the brain permeability of potent central nervous system-active drugs, including anticancer agents.

Effect of the biologically active fragment of zonula occludens toxin, delta G, on the intestinal paracellular transport and oral absorption of mannitol

OBJECTIVE

Many therapeutically active agents experience low bioavailability upon oral administration due to low permeability, low solubility, interaction with efflux transporters or first pass metabolism. In general, absorption enhancers are agents that can modulate the paracellular permeability of drugs, thus, potentially increasing oral bioavailability. The objective of this study was to examine the effect of the active fragment of Zonula occludens toxin (Zot), deltaG, on the transport of a paracellular marker, mannitol, using in vitro (Caco-2 cell monolayers) and in vivo (intraduodenal administration in rats) experimental methods.

METHODS

The transport of [14C]mannitol with deltaG (0, 50, 80, or 100 microg/ml) was determined across Caco-2 cells. Male Sprague-Dawley rats were assigned to receive one of the following treatments: [14C] mannitol (40 microCi/kg), [14C]mannitol/deltaG (417 microg/kg), or [14C] mannitol/deltaG/Protease inhibitors (PI).

RESULTS

The mean (+/-S.E.M.) apparent mannitol permeability coefficients (P(app)) observed after incubation with 0, 50, 80, and 100 microg/ml deltaG were 3.5 (+/-0.4), 4.17 (+/-0.27), 4.33 (+/-0.61), and 9.94 (+/-0.24)x10(-6) cm/s. After oral administration, C(max) (3.8 x 10(-4) vs. 4.4 x 10(-4) mM) and AUC(0-6 h) (0.096 vs. 0.088 mM min), obtained for [14C]mannitol and [14C]mannitol/deltaG, respectively, were not statistically different. However, both C(max) (7.6 x 10(-4) mM) and AUC(0-6 h) (0.25 mM min) were significantly higher for the [14C]mannitol/deltaG/PI treatment.

CONCLUSIONS

The 12 kDa fragment of Zot, deltaG, enhanced the in vitro transport and oral absorption of the paracellular marker, mannitol, in the presence of protease inhibitors (PI).

Enhanced permeability of molecular weight markers and poorly bioavailable compounds across Caco-2 cell monolayers using the absorption enhancer, zonula occludens toxin

PURPOSE

Zonula occludens toxin (Zot), a protein elaborated from Vibrio cholerae, has been shown to be capable of reversibly opening tight junctions. The objective of this work was to determine the stability of Zot and to examine the permeability of a series of molecular weight hydrophilic markers and therapeutic agents in the presence of Zot.

METHOD

The transport of molecular weight markers (i.e., PEG 4000, FITC-dextran 10.000 and inulin) and therapeutic agents (i.e., acyclcovir, cyclopsorin, paclitaxel. doxorubicin) was evaluated with Zot (0, 2, and 4 microg/mL) using Caco-2 cell monolayers.

RESULTS

Zot was found to be stable over a 10-day period. Significantly higher (p < 0.05) permeability of the molecular weight markers, in lin, and PEG4000 were observed with Zot (4 microg/mL). The transport of each therapeutic marker was significantly increased with paclitaxel displaying a >3-fold enhancement in Papp values with Zot (4 microg/mL). A 30% decrease in transepithelial electrical resistance values wa observed, which returned to baseline 30 min after Zot was removed.

CONCLUSIONS

Considering the problems of poor oral bioavailability, it is concluded that Zot is a promising drug delivery technology to be used to enhance drug transport across the intestinal mucosa. Future applications are targeted at assessing its usefulness in oral drug delivery using in vivo systems.

A membrane-permeant peptide that inhibits MLC kinase restores barrier function in in vitro models of intestinal disease

BACKGROUND & AIMS

Maintenance of the mucosal barrier is a critical function of intestinal epithelia. Myosin regulatory light chain (MLC) phosphorylation is a common intermediate in the pathophysiologic regulation of this barrier. The aim of this study was to determine whether a membrane permeant inhibitor of MLC kinase (PIK) could inhibit intracellular MLC kinase and regulate paracellular permeability.

METHODS

Recombinant MLC and Caco-2 MLC kinase were used for kinase assays. T84 and Caco-2 monolayers were treated with enteropathogenic Escherichia coli (EPEC) or tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma to induce barrier dysfunction.

RESULTS

PIK inhibited MLC kinase in vitro and was able to cross cell membranes and concentrate at the perijunctional actomyosin ring. Consistent with these properties, apical addition of PIK reduced intracellular MLC phosphorylation by 22% +/- 2%, increased transepithelial resistance (TER) by 50% +/- 1%, and decreased paracellular mannitol flux rates by 5.2 +/- 0.2-fold. EPEC infection induced TER decreases of 37% +/- 6% that were limited to 16% +/- 5% by PIK. TNF-alpha and IFN-gamma induced TER decreases of 22% +/- 3% that were associated with a 172% +/- 1% increase in MLC phosphorylation. Subsequent PIK addition caused MLC phosphorylation to decrease by 25% +/- 4% while TER increased to 97% +/- 6% of control.

CONCLUSIONS

PIK can prevent TER defects induced by EPEC and reverse MLC phosphorylation increases and TER decreases induced by TNF-alpha and IFN-gamma. The data also suggest that TNF-alpha and IFN-gamma regulate TER, at least in part, via the perijunctional cytoskeleton. Thus, PIK may be the prototype for a new class of targeted therapeutic agents that can restore barrier function in intestinal disease states.

Bioadhesive microdevices with multiple reservoirs: a new platform for oral drug delivery

A variety of delivery systems have been devised, in recent years, to improve the oral bioavailability of drugs including enterically coated tablets, capsules, particles, and liposomes. Microfabrication technology may offer some potential advantages over conventional drug delivery technologies. This technology, combined with appropriate surface chemistry, may permit the highly localized and unidirectional release of drugs, permeation enhancers, and/or promoters. In this study, we demonstrate the fabrication of prototype reservoir-containing microdevices and a surface chemistry protocol that can be used to bind lectin via avidin-biotin interactions to these micromachined drug delivery vehicles. The use of microfabrication allows one to tailor the size, shape, reservoir volume, and surface characteristics of the drug delivery vehicle. In vitro studies show enhanced bioadhesion of these lectin conjugated silicon microdevices. This approach may be used to improve the absorption of pharmacologically active biopolymers such as peptides, proteins and oligonucleotides into circulation at targeted sites in the GI system via the creation of a robust hybrid organic/inorganic delivery system. This paper describes one of the first applications of microfabrication to oral drug delivery.

Zonula occludens toxin (Zot) interferes with the induction of nasal tolerance to gliadin

Both nasal and oral administration of soluble protein antigens (Ags) induce tolerance, a phenomenon that has hampered mucosal vaccine design. To produce active immunity the use of adjuvants co-administered with soluble Ags is required. Cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) were found to be powerful mucosal adjuvants, but they are not suitable for clinical use because of their associated toxicity. Therefore, there is the need to develop alternative strategies to deliver Ag in order to induce immunoprotection. Among these innovative tools, a new toxin, Zonula occludens toxin (Zot), produced by phages in toxigenic strains of Vibrio cholerae, has been recently exploited for its adjuvant activity at the mucosal level. The present study was undertaken to further highlight the adjuvant properties of Zot. The ability of Zot to induce a mucosal response to gliadin was demonstrated per serum antibody production. In our established model of systemic tolerance to gliadin, induced by its nasal administration, we found a reduced production of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) upon administration of gliadin alone. This immune suppression was reverted in mice receiving gliadin together with Zot. As previously shown, the down-regulation of Th1-like cytokines was found to be associated to a suppression of the T-cell proliferation, while such a suppression was completely reverted by Zot co-administration. In conclusion, these data confirm Zot as a good mucosal adjuvant, considering its ability to interfere with the suppression of specific cell mediated immunity, probably as a result of the increased dose and/or altered processing of Ag at mucosal level.

Enhancement of paracellular transport of heparin disaccharide across Caco-2 cell monolayers

The enhancement of paracellular transport of heparin disaccharide using several absorption enhancers across Caco-2 cell monolayers was tested. The cytotoxicity of these enhancers was also examined. The enhancing effects by Quillaja saponin, dipotassium glycyrrhizinate, 18beta-glycyrrhetinic acid, sodium caprate and taurine were determined by changes in transepithelial electrical resistance (TEER) and the amount of heparin disaccharide transported across Caco-2 cell monolayers. Among the absorption enhancers, 18beta-glycyrrhetinic acid and taurine decreased TEER and increased the permeability of heparin disaccharide in a dose-dependent and time-dependent manner with little or negligible cytotoxicity. Our results indicate that these absorption enhancers can widen the tight junction, which is a dominant paracellular absorption route of hydrophilic compounds. It is highly possible that these absorption enhancers can be applied as pharmaceutical excipients to improve the transport of macromolecules and hydrophilic drugs having difficulty in permeability across the intestinal epithelium.

Electrolyte transport in the mammalian colon: mechanisms and implications for disease

The colonic epithelium has both absorptive and secretory functions. The transport is characterized by a net absorption of NaCl, short-chain fatty acids (SCFA), and water, allowing extrusion of a feces with very little water and salt content. In addition, the epithelium does secret mucus, bicarbonate, and KCl. Polarized distribution of transport proteins in both luminal and basolateral membranes enables efficient salt transport in both directions, probably even within an individual cell. Meanwhile, most of the participating transport proteins have been identified, and their function has been studied in detail. Absorption of NaCl is a rather steady process that is controlled by steroid hormones regulating the expression of epithelial Na(+) channels (ENaC), the Na(+)-K(+)-ATPase, and additional modulating factors such as the serum- and glucocorticoid-regulated kinase SGK. Acute regulation of absorption may occur by a Na(+) feedback mechanism and the cystic fibrosis transmembrane conductance regulator (CFTR). Cl(-) secretion in the adult colon relies on luminal CFTR, which is a cAMP-regulated Cl(-) channel and a regulator of other transport proteins. As a consequence, mutations in CFTR result in both impaired Cl(-) secretion and enhanced Na(+) absorption in the colon of cystic fibrosis (CF) patients. Ca(2+)- and cAMP-activated basolateral K(+) channels support both secretion and absorption of electrolytes and work in concert with additional regulatory proteins, which determine their functional and pharmacological profile. Knowledge of the mechanisms of electrolyte transport in the colon enables the development of new strategies for the treatment of CF and secretory diarrhea. It will also lead to a better understanding of the pathophysiological events during inflammatory bowel disease and development of colonic carcinoma.

The toxins of Bacteroides fragilis

Bacteroides fragilis are both key commensals and important human pathogens. Particular strains of B. fragilis, termed enterotoxigenic B. fragilis (ETBF), are recently identified enteric pathogens of children and adults. These strains are distinguished by secretion of a 20kDa metalloprotease toxin (B. fragilis toxin or BFT), the first recognized and only established toxin to date for B. fragilis. Three isotypes of BFT are encoded by distinct bft loci contained within a 6kb chromosomal region unique to ETBF strains termed the B. fragilis pathogenicity island (BfPAI). Experimental studies have suggested that the cellular target for BFT is E-cadherin, the primary protein of the zonula adherens. It is postulated that BFT cleavage of E-cadherin is critical in precipitating the intracellular events culminating in the two established activities for BFT; namely, stimulation of secretion in ligated intestinal segments in several animal species and alteration of cellular morphology only in epithelial cells that retain the ability to polarize and form a tight junctional complex. Future studies will be directed to characterizing in greater detail both the molecular genetics of the BFT toxin and the precise steps in its cellular mechanism of action.

The roles of claudin superfamily proteins in paracellular transport

The claudin superfamily consists of at least 18 homologous proteins in humans. These proteins are important structural and functional components of tight junctions in paracellular transport. Complexed with two other integral transmembrane proteins, occludin and junctional adhesion molecule, claudins are located in both epithelial and endothelial cells in all tight junction-bearing tissues. Claudins interact directly with tight junction-specific, membrane-associated guanylate kinase homologues, ZO-1, ZO-2, and ZO-3, and indirectly with AF-6 and the myosin-binding molecule cingulin. These protein-protein interactions promote scaffolding of the tight junction transmembrane proteins and provide a link to the actin cytoskeleton for transducing regulatory signals to and from tight junctions. The distinct permeability properties observed in different epithelia and endothelia seemingly result from the restricted tissue expression, variability of the homopolymer and heteropolymer assembly, regulated transcription and translation, and the subcellular localization of claudin family proteins. Defects in claudins are causatively associated with a variety of human diseases, demonstrating that claudins play important roles in human physiology. In conditions where the cell adhesion function contributed by tight junctions is essential, such as in altered paracellular transport, in proliferative diseases, and during morphogenesis, the claudin superfamily of homologous proteins provides the molecular basis for the uniqueness of tight junctions and emerges as a new target for intervention.

Molecular physiology and pathophysiology of tight junctions V. assault of the tight junction by enteric pathogens

Studies of the impact of enteric pathogens and their virulence factors on the proteins comprising the tight junction and zonula adherens offer a novel approach to dissection of tight junctional complex regulation. Most studies to date provide only tantalizing clues that select pathogens may indeed assault the tight junctional complex. Information on critical human pathogens such as Campylobacter jejuni and Shigella and Salmonella subspecies is lacking. Mechanistic studies are currently sparse, but available results on pathogenic Escherichia coli and specific virulence factors such as the Rho-modifying and protease bacterial toxins indicate four major mechanisms by which these pathogens may act: 1) direct cleavage of tight junctional structural proteins; 2) modification of the actin cytoskeleton; 3) activation of cellular signal transduction; and 4) triggering transmigration of polymorphonuclear cells across the epithelial cell barrier. New therapeutics may evolve from detailed studies of these pathogens and the cellular processes and proteins they disrupt.

Vibrio cholerae ACE stimulates Ca(2+)-dependent Cl(-)/HCO(3)(-) secretion in T84 cells in vitro

ACE, accessory cholera enterotoxin, the third enterotoxin in Vibrio cholerae, has been reported to increase short-circuit current (I(sc)) in rabbit ileum and to cause fluid secretion in ligated rabbit ileal loops. We studied the ACE-induced change in I(sc) and potential difference (PD) in T84 monolayers mounted in modified Ussing chambers, an in vitro model of a Cl(-) secretory cell. ACE added to the apical surface alone stimulated a rapid increase in I(sc) and PD that was concentration dependent and immediately reversed when the toxin was removed. Ion replacement studies established that the current was dependent on Cl(-) and HCO(3)(-). ACE acted synergistically with the Ca(2+)-dependent acetylcholine analog, carbachol, to stimulate secretion in T84 monolayers. In contrast, the secretory response to cAMP or cGMP agonists was not enhanced by ACE. The ACE-stimulated secretion was dependent on extracellular and intracellular Ca(2+) but was not associated with an increase in intracellular cyclic nucleotides. We conclude that the mechanism of secretion by ACE involves Ca(2+) as a second messenger and that this toxin stimulates a novel Ca(2+)-dependent synergy.

Zonula occludin toxin, a microtubule binding protein

AIM: To investigate the interaction of Zot with microtubule.

METHODS: Zot affinity column was applied to purify Zot-binding protein(s) from crude intestinal cell lysates. After incubation at room temperature, the column was washed and the proteins bound to the Zot affinity column we re eluted by step gradient with NaCl (0.3-0.5 mol·L^-1). The fractions were subjected to 6.0%-15.0% (w/v) gradient SDS-PAGE and then transferred to PVDF membrane for N-terminal sequencing. Purified Zot and tau protein were blotted by using anti-Zot or anti-tau antibodies. Finally, purified Zot was tested in an in vitro tubulin binding assay.

RESULTS: Fractions from Zot affinity column yielded two protein bands with a M_r of 60 kU and 45 kU respectively. The N-terminal sequence of the 60 kU band resulted identical to β-tubulin. Zot also cross-reacts with anti-tau antibodies. In the in vitro tubulin binding assay, Zot co-precipitate with Mt, further suggesting that Zot possesses tubulin-b inding properties.

CONCLUSION: Taken together, these results suggest that Zot regulates the permeability of intestinal tight junctions by binding to intracellular Mt, with the subsequent activation of the intracellular signaling leading to the permeabilization of intercellular tight junctions.

Cross-talk between enteric pathogens and the intestine

Enteric pathogens finely regulate the expression of virulence genes in reply to stimuli generated by the intestinal environment. This minireview focuses on recently discovered strategies developed by enteric bacteria to cause intestinal secretion through the elaboration of factors that share structure and function with specific host counterparts. Such bacterial antigens appear to interfere largely with the epithelial cell signalling that physiologically regulates the numerous and, as yet not fully elucidated, mechanisms controlling both the transcellular and the paracellular secretion pathways. Heat-stable enterotoxins (STs) elaborated by enterotoxigenic Escherichia coli and the enteroaggregative E. coli enterotoxin (EAST1) are both typical examples of enteric toxins that activate the transcellular secretion pathway by mimicking guanylin, the endogenous modulator of cGMP signalling. Alternative strategies have been developed by Salmonella to induce intestinal secretion through the elaboration of a factor (SopB) that resembles at least two of the host cell 4-phosphatases, enzymes that activate the Ca-dependent transcellular secretion pathway. Finally, Vibrio cholerae has developed innovative tactics to activate the paracellular secretion pathway through the elaboration of Zonula occludens toxin (Zot), a factor that mimics a recently described physiological modulator of intercellular tight junctions.

Nanosphere based oral insulin delivery

Zinc insulin is successfully encapsulated in various polyester and polyanhydride nanosphere formulations using Phase Inversion Nanoencapsulation (PIN). The encapsulated insulin maintains its biological activity and is released from the nanospheres over a span of approximately 6 h. A specific formulation, 1.6% zinc insulin in poly(lactide-co-glycolide) (PLGA) with fumaric anhydride oligimer and iron oxide additives has been shown to be active orally. This formulation is shown to have 11.4% of the efficacy of intraperitoneally delivered zinc insulin and is able to control plasma glucose levels when faced with a simultaneously administered glucose challenge. A number of properties of this formulation, including size, release kinetics, bioadhesiveness and ability to traverse the gastrointestinal epithelium, are likely to contribute to its oral efficacy.

Characterization of a putative virulence island in the chromosome of uropathogenic Escherichia coli possessing a gene encoding a uropathogenic-specific protein

This study was initiated to search for a homologue of the Vibrio cholerae zot gene in uropathogenic Escherichia coli (UPEC) using a specific DNA probe. The faint signal obtained at low stringency with some UPEC strains associated with prostatitis cases prompted us to examine UPEC strains by PCR using primers designed from the conserved regions of the proteins of the Zot group of putative NTPases containing the classical NTP binding motif. This led to the discovery of a DNA fragment in UPEC strains which hybridized with a probe designed from the PCR. Further analysis of this DNA fragment revealed an ORF which was designated as uropathogenic specific protein (Usp). The gene encoding Usp was 1038 bp long and codes for 346 amino acids with an appropriate SD sequence. Upstream and downstream analysis of usp revealed motifs of prokaryotic consensus promoters and three small ORFs with SDs and ribosome binding sites transcribed in the same direction of usp. The proximity of these set of genes in a specific area of the bacterial chromosome resembling a block of genes preferentially associated with UPEC coupled with the presence of a motif matching that of a Tn3 transposon family lead us to believe that this could be an hitherto unknown pathogenicity island.

Intestinal permeability, leaky gut, and intestinal disorders

A major task of the intestine is to form a defensive barrier to prevent absorption of damaging substances from the external environment. This protective function of the intestinal mucosa is called permeability. Clinicians can use inert, nonmetabolized sugars such as mannitol, rhamnose, or lactulose to measure the permeability barrier or the degree of leakiness of the intestinal mucosa. Ample evidence indicates that permeability is increased in most patients with Crohn's disease and in 10% to 20% of their clinically healthy relatives. The abnormal leakiness of the mucosa in Crohn's patients and their relatives can be greatly amplified by aspirin preadministration. Permeability measurements in Crohn's patients reflect the activity, extent, and distribution of the disease and may allow us to predict the likelihood of recurrence after surgery or medically induced remission. Permeability is also increased in celiac disease and by trauma, burns, and nonsteroidal anti-inflammatory drugs. The major determinant of the rate of intestinal permeability is the opening or closure of the tight junctions between enterocytes in the paracellular space. As we broaden our understanding of the mechanisms and agents that control the degree of leakiness of the tight junctions, we will be increasingly able to use permeability measurements to study the etiology and pathogenesis of various disorders and to design or monitor therapies for their management.

Regulation of the intestinal epithelial paracellular barrier

Paracellular transport of orally-administered drugs, the passage of molecules between adjacent intestinal epithelial cells, is impeded by a range of structural and functional features found in the intestine. An increased knowledge of the mechanisms that govern the paracellular barrier will enable the pharmaceutical scientist to design novel and rational formulations and delivery platforms that will improve the oral bioavailability of therapeutic molecules, particularly proteins and peptides, which would be taken-up by the paracellular pathway.

Cellular microbiology: can we learn cell physiology from microorganisms?

Cellular microbiology is a new discipline that is emerging at the interface between cell biology and microbiology. The application of molecular techniques to the study of bacterial pathogenesis has made possible discoveries that are changing the way scientists view the bacterium-host interaction. Today, research on the molecular basis of the pathogenesis of infective diarrheal diseases of necessity transcends established boundaries between cell biology, bacteriology, intestinal pathophysiology, and immunology. The use of microbial pathogens to address questions in cell physiology is just now yielding promising applications and striking results.

Increased gastrointestinal permeability is an early lesion in the spontaneously diabetic BB rat

The BB rat spontaneously develops autoimmune diabetes. Feeding these animals a hydrolyzed casein diet significantly reduces the incidence of this disease, suggesting that a dietary antigen is involved in the pathogenesis of this disease. In other syndromes associated with luminal antigens, including celiac and Crohn's disease, increased intestinal permeability has been suggested to play an etiological role. Therefore, the objective of this study was to evaluate whether increased permeability was also present in BB rats before disease development. By measuring gastrointestinal permeability, in animals on a regular or hydrolyzed casein diet, we were able to demonstrate that increased gastric and small intestinal permeability appeared before the development of both insulitis and clinical diabetes. Although hydrolysis of dietary protein significantly reduced the incidence of diabetes, it did not alter the small intestinal permeability abnormality, suggesting that this is an early event. Increased permeability appears to have an early role in the genesis of several immunological diseases and may represent a common event in these diseases.

Zonula occludens toxin is a powerful mucosal adjuvant for intranasally delivered antigens

Zonula occludens toxin (Zot) is produced by toxigenic strains of Vibrio cholerae and has the ability to reversibly alter intestinal epithelial tight junctions, allowing the passage of macromolecules through the mucosal barrier. In the present study, we investigated whether Zot could be exploited to deliver soluble antigens through the nasal mucosa for the induction of antigen-specific systemic and mucosal immune responses. Intranasal immunization of mice with ovalbumin (Ova) and recombinant Zot, either fused to the maltose-binding protein (MBP-Zot) or with a hexahistidine tag (His-Zot), induced anti-Ova serum immunoglobulin G (IgG) titers that were approximately 40-fold higher than those induced by immunization with antigen alone. Interestingly, Zot also stimulated high anti-Ova IgA titers in serum, as well as in vaginal and intestinal secretions. A comparison with Escherichia coli heat-labile enterotoxin (LT) revealed that the adjuvant activity of Zot was only sevenfold lower than that of LT. Moreover, Zot and LT induced similar patterns of Ova-specific IgG subclasses. The subtypes IgG1, IgG2a, and IgG2b were all stimulated, with a predominance of IgG1 and IgG2b. In conclusion, our results highlight Zot as a novel potent mucosal adjuvant of microbial origin.

Oral insulin delivery

An oral form of insulin has been the elusive goal for many investigators since the protein's initial discovery by Banting and Best in 1922. This paper will attempt to answer why this is the case by describing the substantial barriers to the development of oral insulin formulations. Following this description, specific strategies to overcome the barriers to oral insulin administration will be discussed. Most notably, the use of permeation enhancers, protease inhibitors, enteric coatings and polymer microsphere formulations will be covered, including commentary on which methods hold more promise towards the successful development of oral insulin.

Stimulation of mucosal and systemic antibody responses against Bordetella pertussis filamentous haemagglutinin and recombinant pertussis toxin after nasal administration with chitosan in mice

Mice were intranasally immunised with a mixture of Bordetella pertussis filamentous haemagglutinin (FHA) and recombinant pertussis toxin, PT-9K/129G (rPT) in combination with chitosan. For both antigens, this formulation induced systemic responses as measured by serum IgG and also mucosal responses as measured by secretory IgA in lung lavage and nasal washes. Immunosorbant assays were used to measure these responses. Both the systemic and mucosal responses were considerably higher than those produced when a mixture of rPT and FHA was administered nasally without chitosan. In comparison, intraperitoneally administered rPT/FHA adsorbed to Alhydrogel elicited only a systemic response, and nasal chitosan solution produced neither systemic nor mucosal response. This study clearly demonstrated that chitosan potentiated the serum and mucosal immune responses to nasally administered FHA and rPT in mice. Hence, this nasal chitosan delivery system has potential as a new non-injectable vaccine for the prophylaxis of whooping cough.

Novel approaches for oral delivery of macromolecules

Traditional forms of administrations of nonabsorbable drugs and peptides often rely on their parenteral injection, since the intestinal epithelium is poorly permeable to these therapeutical agents. A number of innovative drug delivery approaches have been recently developed, including the drug entrapment within small vesicles or their passage through the intestinal paracellular pathway. Zonula occludens toxin, a recently discovered protein elaborated by Vibrio cholerae, provided tools to gain more insights on the pathophysiology of the regulation of intestinal permeability through the paracellular pathway and to develop alternative approaches for the oral delivery of drugs and macromolecules normally not absorbed through the intestine.

Modulation of intestinal permeability: an innovative method of oral drug delivery for the treatment of inherited and acquired human diseases

Conventional forms of administrations of nonabsorbable drugs and peptides rely on their parenteral injection. The intestinal epithelium represents the major barrier to the oral absorption of these therapeutical agents into the systemic circulation. Recently, a number of innovative drug delivery approaches have been developed, including the drug entrapment within small vesicles or their passage through the intestinal paracellular pathway. Zonula occludens toxin, a recently discovered protein elaborated by Vibrio cholerae, provided tools for gaining more insights on the pathophysiology of the regulation of intestinal permeability and to developing alternative approaches for the oral delivery of drugs and macromolecules normally not absorbed through the intestine.

Innovative strategies for the oral delivery of drugs and peptides

Conventional forms of administration for nonabsorbable drugs and peptides often rely on parenteral injection, because the intestinal epithelium represents a major barrier to the oral absorption of these therapeutic agents. Recently, a number of innovative drug-delivery approaches have been developed, including entrapment within small vesicles and passage through the space between adjacent intestinal cells. This article reviews some of the most promising techniques currently available for oral delivery and their possible practical applications for the delivery of vaccines and drugs for the treatment of clinical conditions that require frequent, chronic parenteral administration.