Enhanced and prolonged cross-presentation following endosomal escape of exogenous antigens encapsulated in biodegradable nanoparticles

CD8(+) T-cell responses are critical in the immunological control of tumours and infectious diseases. To prime CD8(+) T cells against these cell-associated antigens, exogenous antigens must be cross-presented by professional antigen-presenting cells (APCs). While cross-presentation of soluble antigens by dendritic cells is detectable in vivo, the efficiency is low, limiting the clinical utility of protein-based vaccinations. To enhance the efficiency of presentation, we generated nanoparticles from a biodegradable polymer, poly(D,L-lactide-co-glycolide) (PLGA), to deliver antigen into the major histocompatibility complex (MHC) class I antigen presentation pathway. In primary mouse bone marrow-derived dendritic cells (BMDCs), the MHC class I presentation of PLGA-encapsulated ovalbumin (OVA) stimulated T cell interleukin-2 secretion at 1000-fold lower concentration than soluble antigen and 10-fold lower than antigen-coated latex beads. The microparticles also served as an intracellular antigen reservoir, leading to sustained MHC class I presentation of OVA for 72 hr, decreasing by only 20% after 96 hr, a time at which the presentation of soluble and latex bead-associated antigens was undetectable. Cytosol extraction demonstrated that antigen delivery via PLGA particles increased the amount of protein that escaped from endosomes into the cytoplasm, thereby increasing the access of exogenous antigen to the classic MHC class I loading pathway. These data indicate that the unique properties of PLGA particle-mediated antigen delivery dramatically enhance and sustain exogenous antigen presentation by MHC class I, potentially facilitating the clinical use of these particles in vaccination.

An intravital and confocal microscopic study of the distribution of intracameral antigen in the aqueous outflow pathways and limbus of the rat eye

In a previous investigation into the fate of fluorescently labelled antigen (Ag) injected into the anterior chamber (AC) of the rat eye, a large number of Ag+ cells were noted in the conventional and non-conventional aqueous humour outflow pathways together with the external limbus. The aim of this study was to investigate the precise distribution and phenotype of these cells and compare their ability to capture fluorescent-labelled protein (bovine serum albumin, BSA, and ovalbumin, OVA) and polysaccharides (dextran, Dx) injected into the AC. The density of Ag+ cells in the iris and limbus was investigated using in vivo video fluorescence microscopy 24 hr post-injection. The distribution and phenotype of Ag+ cells in ocular tissues was analysed by confocal microscopy of frozen sections and in iris and corneoscleral/limbal wholemounts from animals sacrificed 24 hr post injection. The general distribution of labelled Ag was equivalent in OVA, BSA and Dx injected animals. Antigen-bearing cells were observed within the iris, iridocorneal angle, pre-equatorial choroid and around limbal/episcleral vessels. Localization of Ag+ cells and free Ag in the anterior segment suggests that substances of these molecular weights (40-70 kDa) leave the eye through the conventional and non-conventional aqueous outflow pathways. The cells that internalized BSA, OVA or Dx in ocular tissues were of a similar phenotype, namely, ED1+, ED2+, occasionally ED3+ and predominantly MHC class II-, thus suggesting that they are of the macrophage phenotype. However, a few Ag+ MHC class II+ dendriform cells (putative DC) were also observed in the iris, trabecular meshwork, choroid and episclera. In conclusion our data reveal that the majority of intracamerally injected soluble Ag retained in the eye is taken up by resident macrophages not only in the iris but in all tissues lining the AC of the eye.

Effect of enzymatic modification of dietary wheat flour for reducing its allergenicity on oral sensitization to and intestinal absorption of ovalbumin

Increase in plasma immunoglobulin G specific to orally administered ovalbumin in Brown Norway rats was retarded by feeding enzyme-treated wheat flour when compared with untreated flour. Because plasma ovalbumin concentrations after feeding ovalbumin tended to be lower in mice fed enzyme-treated flour than in those fed untreated flour, suppression of ovalbumin absorption may be relevant to retarded sensitization observed in rats.

Ultra-stable zeolites—a tool for in-cell chemistry

Ultrastable zeolite particles were used as vehicles to carry low molecular bio-active substances and macromolecules as proteins into viable cells. Zeolite particles that can be used for internalisation by phagocytosis were obtained from the non-sedimenting fraction of a commercially available zeolite preparation after 1 x g sedimentation. Protein adsorbed on the zeolite surface was shown to enter the endosomal pathway after phagocytosis and could be cleaved by the endosomal proteases. As a model of a low molecular weight bio-active molecule, the inhibitor of the cellular synthesis of nitrogen oxide, N-nitro-L-arginine methyl ester (L-NAME), was used. A partial inhibition of the cellular NO production was shown after utilizing zeolites as vehicles to introduce the inhibitor into the cells. A targeting of the intra-cellular enzymes that was at least 10 times more efficient was obtained by the use of zeolites as a carrier of the inhibitor, as opposed to addition of the inhibitor to the culture medium.

IL-2 intratumoral immunotherapy enhances CD8+ T cells that mediate destruction of tumor cells and tumor-associated vasculature: a novel mechanism for IL-2

Therapeutic use of IL-2 can generate antitumor immunity; however, a variety of different mechanisms have been reported. We injected IL-2 intratumorally (i.t.) at different stages of growth, using our unique murine model of mesothelioma (AE17; and AE17 transfected with secretory OVA (AE17-sOVA)), and systematically analyzed real-time events as they occurred in vivo. The majority of mice with small tumors when treatment commenced displayed complete tumor regression, remained tumor free for >2 mo, and survived rechallenge with AE17 tumor cells. However, mice with large tumors at the start of treatment failed to respond. Timing experiments showed that IL-2-mediated responses were dependent upon tumor size, not on the duration of disease. Although i.t. IL-2 did not alter tumor Ag presentation in draining lymph nodes, it did enhance a previously primed, endogenous, tumor-specific in vivo CTL response that coincided with regressing tumors. Both CD4(+) and CD8(+) cells were required for IL-2-mediated tumor eradication, because IL-2 therapy failed in CD4(+)-depleted, CD8(+)-depleted, and both CD4(+)- and CD8(+)-depleted C57BL/6J animals. Tumor-infiltrating CD8(+) T cells, but not CD4(+) T cells, increased in association with a marked reduction in tumor-associated vascularity. Destruction of blood vessels required CD8(+) T cells, because this did not occur in nude mice or in CD8(+)-depleted C57BL/6J mice. These results show that repeated doses of i.t. (but not systemic) IL-2 mediates tumor regression via an enhanced endogenous tumor-specific CTL response concomitant with reduced vasculature, thereby demonstrating a novel mechanism for IL-2 activity.

Polyphenols from some foodstuffs as inhibitors of ovalbumin permeation through caco-2 cell monolayers

Some spices showed high inhibitory activity against ovalbumin permeation through Caco-2 cell monolayers. Pimentol from allspice, rosmarinic acid and luteolin-7-O-beta-glucuronide from thyme, quercetin-3-O-beta-glucuronide from coriander and rutin from tarragon were identified as the active principles. A structure-activity relationship study among the active isolates and their related compounds indicated that the presence of a catechol structure played an important role in the inhibitory activity of each compound.

Application of polyethyleneglycol (PEG)-modified liposomes for oral vaccine: effect of lipid dose on systemic and mucosal immunity

To examine the systemic and mucosal immunity towards a liposomal antigen in an oral vaccine, we prepared ovalbumin (OVA)-encapsulating polyethyleneglycol (PEG)-modified liposomes and unmodified ones, and orally administered two different concentrations of them to mice. Unmodified liposomes tended to induce a stronger systemic immune response than the PEG-modified ones especially at the higher concentration of liposomes. Whereas at the lower liposome concentration the mucosal immune response was stronger for the PEG-modified liposomes than for the unmodified ones but nearly the same at the higher concentration. The relative amount of immunoglobulin G (IgG) against OVA in the plasma was 1.7-fold higher for a 12.5 micro mol phospholipid dose of PEG-liposomes encapsulating OVA than for a 5.0 micro mol one encapsulating the same amount of OVA. On the contrary, the relative amount of IgA in the intestinal wash was 2.6-fold higher for the 5.0 micro mol phospholipid dose than for the 12.5 micro mol one. These results indicate that OVA encapsulated in a small number of liposomes, especially the PEG-modified ones, is favorable for inducing a mucosal immune response and that the same amount of OVA in a large number of liposomes tends to improve the systemic immune response. A possible explanation for this tendency is the differential release rate of OVA from the liposomes at the intestinal mucosa. Our present study suggests that the dose of liposomes containing antigen is an important factor for controlling the response of systemic and mucosal immune systems.

Uptake of ovalbumin-conjugated starch microparticles by pig respiratory nasal mucosa in vitro

The uptake of ovalbumin-conjugated starch microparticles (OVA-MP) was studied after application to porcine respiratory nasal mucosa in vitro. Nasal mucosa from freshly slaughtered pigs was mounted in horizontal Ussing chambers, which permit monitoring of the viability of the tissue exposed to microparticles and ensure that the microparticles are deposited on the mucosa. The antigen-conjugated starch microparticles have previously been shown to produce strong mucosal, cellular and systemic immune responses to conjugated model antigens following oral administration. Intranasal administration of vaccines for mucosal immunisation is an interesting alternative to oral administration, since nasal delivery systems generally require lower doses of antigen and the site of application is better suited for protection against air-borne antigens. Most of a nasally administered dose is deposited on the surface of the respiratory area of the nasal mucosa. It is therefore important to examine whether the microparticles are taken up in this area and, if so, by which cell type. Confocal laser scanning microscopy and transmission electron microscopy (TEM) of the nasal tissue both showed intracellular OVA-MP in non-ciliated epithelial cells after 45 min' incubation. The morphology of the cells in the TEM preparations did not support the presence of either M cells (specialised antigen sampling cells) or adjacent lymphocytes. Anticytokeratin-18 (Ac18) was used as a potential M cell marker. However, there was no indication of Ac18 binding to M cells, but it did bind to mucus-producing cells in the respiratory nasal mucosa. In conclusion, OVA-MP were taken up intracellularly by non-ciliated epithelial cells in the nasal respiratory mucosa of pigs, in vitro.

Influence of chronic unpredictable stress on the allergic responses in rats

The effects of chronic unpredictable stress on airway leukocyte infiltration and plasma extravasation in female rats have been investigated. The chronic stress lasted for 14 days and consisted of transitory and variable changes in the living conditions of the animals. Concomitant to the stress procedure, the animals were sensitized (Day 0) and challenged with ovalbumin (OVA; 200 microg) at Day 14. Bronchoalveolar lavage (BAL) was performed 48 h after intratracheal challenge with OVA (0.4 ml of a 0.25% solution). The increase in plasma extravasation was assessed by the rat paw oedema induced by OVA (0.1 mg/paw) or the mast cell degranulator compound 48/80 (5 microg/paw). A significant increase (P < .05) in the total leukocyte influxes into the airways was observed in the stressed (sensitized) group compared to nonstressed (sensitized) animals, and this was associated with a marked recruitment of eosinophils and mononuclear cells in the BAL fluid. In OVA-sensitized rats, intraplantar injection of OVA induced a marked paw oedema that was significantly higher in stressed compared to nonstressed groups. In contrast to OVA, the compound 48/80 (5 microg/paw)-induced oedema did not significantly differ between nonstressed and stressed groups. Our results indicate that chronic unpredictable stress exacerbates the vascular and cellular inflammatory responses.

In vivo kinetics of the immunoglobulin E response to allergen: bystander effect of coimmunization and relationship with anaphylaxis

BACKGROUND

Murine models of hypersensitivity to allergens are useful tools for the evaluation of preclinical strategies to down-regulate the IgE response.

OBJECTIVE

To monitor the long-term kinetics of T and B cell responses to allergen as a function of allergen dosage and to investigate the effect of parallel immunization with a second antigen; to correlate B cell response with anaphylaxis.

METHODS

CBA/J mice were sensitized every other week by subcutaneous injections of phospholipase A2 (PLA2) and/or ovalbumin (OVA) adsorbed to alum. Specific antibody isotype responses, T cell proliferation, T cell cytokine production and anaphylaxis were assessed throughout the sensitization phase.

RESULTS

Low-dose immunization with PLA2 (0.1 microg) favoured a long-term, specific T helper (Th)2 response with high IgE and IL-4 production in contrast to high-dose PLA2 (10 microg) immunization, which biased the immune response towards a Th1 response with high IgG2a and low IL-4 production. Parallel immunization with an unrelated antigen (ovalbumin) had a significant bystander effect on the immunization with PLA2, which was also dose-dependent. Finally, although anaphylaxis as measured by rectal temperature drop was allergen-specific, it could be induced in the high- and low-dose immunization groups, and was not solely dependent on IgE levels.

CONCLUSION

Though low-dose allergen immunization appears to induce an efficient IgE response, the intensity and quality of this response may be modulated by bystander effects of parallel immunization and does not correlate strictly with anaphylaxis. This observation has relevance to the design of clinical immunotherapy protocols using murine model-based data.

In vivo uptake of chitosan microparticles by murine Peyer's patches: visualization studies using confocal laser scanning microscopy and immunohistochemistry

Although oral vaccination has numerous advantages over parenteral injection, degradation of the vaccine and low uptake by the gut associated lymphoid tissue (GALT) still complicate the development of efficient oral vaccines. However, previous studies in our laboratory demonstrated that chitosan microparticles can have suitable size, charge, loading and release characteristics for oral vaccination using ovalbumin as model vaccine. In this study, two different approaches were used to investigate the in vivo uptake of chitosan microparticles by murine Peyer's patches. Firstly, a confocal laser scanning microscopy (CLSM) study was performed to visualize the uptake of fluorescent-labeled chitosan microparticles in the Peyer's patches after intragastrical feeding. Subsequently, the intestinal epithelial uptake of ovalbumin loaded chitosan microparticles was visualized using immunohistochemical staining of ovalbumin. Because the microparticles are biodegradable, this entrapped ovalbumin will be released after intracellular digestion in the Peyer's patches. CLSM visualization demonstrated that chitosan microparticles enhance the uptake of fluorescent-labeled ovalbumin by the epithelium of the Peyer's patches. No ovalbumin uptake by the intestinal epithelium was observed when the protein was administered without microparticles. Moreover, immunohistochemical visualization studies revealed that ovalbumin could only be transported into the Peyer's patches after association to chitosan microparticles. Since uptake by Peyer's patches is an essential step in oral vaccination, these in vivo experiments demonstrate that chitosan microparticles are very promising vaccine delivery systems.

Wortmannin-sensitive trafficking steps in the endocytic pathway in rat liver endothelial cells

Liver endothelial cells (LECs) play an important homoeostatic role by removing potentially harmful macromolecules from blood. The extremely efficient endocytosis in LECs makes these cells an interesting model for the study of the involvement of phosphoinositides in the different steps of the endocytic process. In the present investigation we have studied the effect of wortmannin, an inhibitor of phosphatidylinositol kinases, on uptake, recycling and intracellular transport of (125)I-labelled ovalbumin, which is taken up in LECs via mannose-receptor-mediated endocytosis. Wortmannin was found to inhibit both uptake and degradation of ovalbumin. Further studies indicated that the reduced uptake via the mannose receptor was due both to a reduction of the number of surface receptors and a reduction in the rate of receptor-ligand internalization. Transport of ligand from endosomes to lysosomes was prevented, leading to increased recycling of internalized ligand. Wortmannin treatment released the Rab5 effector EEA1 from the endosomes and caused reduced size of early endosomes.

Correlation of in vitro and in vivo acetaminophen availability from albumin microaggregates oral modified release formulations

The aim of this study was to develop albumin microaggregated oral formulations for controlled drug release, and to reveal the possible influence of the release site on drug absorption. Acetaminophen was chosen as the model drug, which is included in the Class 1 group of the Biopharmaceutics Classification System (BCS). Albumin micro aggregates were formulated into tablets to obtain different drug release rates: Immediate Release (IR) tablets, multiparticulate systems with an intermediate release rate, and matrix systems showing slow release rate. The properties of the products were initially tested via dissolution studies, and then via bioavailability studies in healthy volunteers. Controlled release albumin microaggregated acetaminophen formulations for oral administration were obtained. The extent of drug absorption was comparable for all formulations, suggesting that the differences found in saliva concentration and urine cumulative profiles could be attributed merely to differences in drug release kinetics, as confirmed by the in vitro-in vivo correlation study. Therefore, it can be concluded that extended release of acetaminophen does not influence its absorption via intestinal heterogeneity.

A quantitative analysis of the glomerular charge barrier in the rat

Modifying the ionic strength (I) is a gentle way to alter charge interactions, but it cannot be done for studies of the glomerular sieving of proteins in vivo. We therefore perfused 18 isolated rat kidneys with albumin solutions of different ionic strengths at a low temperature (cIPK) to inhibit tubular uptake and protease activity. Four anionic proteins were studied, namely albumin (Alb), orosomucoid (Oro), ovalbumin (Ova), and anionic horseradish peroxidase (aHRP), together with the neutral polymer Ficoll. With normal ionic strength of the perfusate (152 mM), the fractional clearance (theta) was 0.0018 +/- 0.0003 for Alb, 0.0033 +/- 0.0003 for Oro, 0.090 +/- 0.008 for Ova, and 0.062 +/- 0.002 for aHRP. These theta values were all lower than for Ficoll of similar hydrodynamic size; e.g., theta(Ficoll 36 A) was >20 times higher than theta for albumin. Low ionic strength (34 mM) increased size selectivity as theta for anionic proteins and Ficoll fell, suggesting a reduction in small-pore radius from 44 +/- 0.4 to 41 +/- 0.5 A, P < 0.01. In contrast, low I reduced the charge density of the membrane, omega, to one-quarter of the 20--50 meq/l estimated at normal I. These dynamic changes in omega seem to be due to volume alterations of the charged gel, fluid shifts that easily are accounted for by the changes in electroosmotic pressures. The finding that low ionic strength induces inverse effects on size selectivity and charge density strongly suggests that separate structures of the glomerular wall are responsible for the two properties.

Chitosan microparticles for oral vaccination: preparation, characterization and preliminary in vivo uptake studies in murine Peyer's patches

Although oral vaccination has numerous advantages over parenteral injection, degradation of the vaccine in the gut and low uptake in the lymphoid tissue of the gastrointestinal tract still complicate the development of oral vaccines. In this study chitosan microparticles were prepared and characterized with respect to size, zeta potential, morphology and ovalbumin-loading and -release. Furthermore, the in vivo uptake of chitosan microparticles by murine Peyer's patches was studied using confocal laser scanning microscopy (CLSM). Chitosan microparticles were made according to a precipitation/coacervation method, which was found to be reproducible for different batches of chitosan. The chitosan microparticles were 4.3+/-0.7 microm in size and positively charged (20+/-1 mV). Since only microparticles smaller than 10 microm can be taken up by M-cells of Peyer's patches, these microparticles are suitable to serve as vaccination systems. CLSM visualization studies showed that the model antigen ovalbumin was entrapped within the chitosan microparticles and not only associated to their outer surface. These results were verified using field emission scanning electron microscopy, which demonstrated the porous structure of the chitosan microparticles, thus facilitating the entrapment of ovalbumin in the microparticles. Loading studies of the chitosan microparticles with the model compound ovalbumin resulted in loading capacities of about 40%. Subsequent release studies showed only a very low release of ovalbumin within 4 h and most of the ovalbumin (about 90%) remained entrapped in the microparticles. Because the prepared chitosan microparticles are biodegradable, this entrapped ovalbumin will be released after intracellular digestion in the Peyer's patches. Initial in vivo studies demonstrated that fluorescently labeled chitosan microparticles can be taken up by the epithelium of the murine Peyer's patches. Since uptake by Peyer's patches is an essential step in oral vaccination, these results show that the presently developed porous chitosan microparticles are a very promising vaccine delivery system.

Intestinal permeability in humans is increased after radiation therapy

PURPOSE

Irradiation inflicts acute injuries to the intestinal mucosa with rapid apoptosis induction and subsequent reduction in epithelial surface area. It may therefore be assumed that the intestinal barrier function is affected. The aim of this study was to compare the mucosal permeability in irradiated rectum and nonirradiated sigmoid colon from patients subjected to radiation therapy before surgical treatment for rectal cancer.

METHODS

Segments from sigmoid colon and rectum obtained from irradiated and nonirradiated patients were stripped from the serosa-muscle layer and mounted in Ussing diffusion chambers. The mucosa-to-serosa passage of the marker molecules 14C-mannitol, fluorescein isothiocyanate-dextran 4,400, and ovalbumin was followed for 120 minutes.

RESULTS

The permeability to the markers was size-dependent and increased linearly across time in all specimens. The passage of all markers was increased in irradiated rectum compared with nonirradiated sigmoid colon, whereas in specimens from nonirradiated patients there were no differences between rectum and sigmoid colon. Histologic signs of crypt and mucosal atrophy were found in the irradiated rectal specimens.

CONCLUSIONS

Early gastrointestinal complications after radiation therapy may be the result of mucosal atrophy in addition to mucosal damage, with a loss of barrier integrity.

Factors affecting antigen uptake by human intestinal epithelial cell lines

We assessed the role of size, solubility, and prophagocytic cytokines interferon-gamma (IFN-gamma), and granulocyte-macrophage colony stimulatory factor (GM-CSF) in antigen uptake and kinetics by intestinal epithelial cells using keyhole limpet hemocyanin and ovalbumin. Both fluoresceinated keyhole limpet hemocyanin (3000-7500 kDa) and fluoresceinated ovalbumin (45 kDa) were internalized by human colonic epithelial cell lines, with kinetics similar to those of fluoresceinated tetanus toxoid, and there was decreased uptake of insoluble immune complexes and no enhancement in the uptake of soluble immune complexes. In addition, neither IFN-gamma nor GM-CSF altered the kinetics of uptake nor enhanced antigen internalization by the intestinal epithelial cell lines. These data suggest that regardless of the size of the soluble antigen, the presence of prophagocytic cytokines, or the formation of soluble immune complexes, fluid phase endocytosis of antigen by intestinal epithelial cells appears to be a relatively stable process.

Substance P dependence of endosomal fusion during bladder inflammation

Urinary bladder instillation of ovalbumin into presensitized guinea pigs stimulates rapid development of local bladder inflammation. Substance P is an important mediator of this inflammatory response, as substance P antagonists largely reverse the process. Vacuolization of the subapical endosomal compartment of the transitional epithelial cells lining the bladder suggests that changes in endosomal trafficking and fusion are also part of the inflammatory response. To test directly for substance P mediation of changes in endosomal fusion, we reconstituted fusion of transitional cell endosomes in vitro using both cuvette-based and flow cytometry energy transfer assays. Bladders were loaded with fluorescent dyes by a hypotonic withdrawal protocol before endosomal isolation by gradient centrifugation. Endosomal fusion assayed by energy transfer during in vitro reconstitution was both cytosol and ATP dependent. Fusion was confirmed by the increase in vesicle size on electron micrographs of fused endosomal preparations compared with controls. In inflamed bladders, dye uptake was inhibited 20% and endosomal fusion was inhibited 50%. These changes are partly mediated by the neurokinin-1 (NK1) receptor (NK1R), as 4 mg/kg of CP-96,345, a highly selective NK1 antagonist, increased fusion in inflamed bladders but had no effect on control bladders. The receptor-mediated nature of this effect was demonstrated by the expression of substance P receptor mRNA in rat bladder lumen scrapings and by the detection of the NK1R message in guinea pig subapical endosomes by Western blot analysis. The NK1Rs were significantly upregulated following induction of an inflammatory response in the bladder. These results demonstrate that 1) in ovalbumin-induced inflammation in the guinea pig bladder, in vitro fusion of apical endosomes is inhibited, showing endocytotic processes are altered in inflammation; 2) pretreatment in vivo with an NK1R antagonist blocks this inhibition of in vitro fusion, demonstrating a role for NK1R in this process; and 3) the NK1R is present in higher amounts in apical endosomes of inflamed bladder, suggesting changes in translation or trafficking of the NK1R during the inflammatory process. This suggests that NK1R can change the fusion properties of membranes in which it resides.

[Permeability of intestinal barrier fo macromolecules in patients with Crohn's disease and ulcerative colitis]

Ovalbumin loading enzyme immunoassay was made in 44 patients with ulcerative colitis (UC) and 8 patients with Crohn's disease (CD). Enhanced intestinal permeability for macromolecules was found in 87.5 and 65.9% of patients with CD and UC, respectively. Blood serum of UC patients suffering from combination of food intolerance with dysbacteriosis contained ovalbumin in amounts exceeding those in patients without the above disorders 3.4 times (p < 0.05). No significant relationship existed between UC patients' high intestinal permeability and such indices as age, duration of the disease, intestinal lesion extension, administration of corticosteroids. It was found desirable to include ovalbumin intestinal permeability test in examination of UC and CD patients to differentiate treatment policy.

Stimulation of mouse macrophage antigen presentation by cocaine

Cocaine has been demonstrated to have multiple effects on the immune system. Here, we determined the effects of cocaine on macrophage antigen presentation, using an in vitro antigen presentation assay after macrophages were treated with cocaine both in vitro and in vivo. Our results showed that in vitro treatment of macrophages with cocaine significantly enhanced macrophage's ability to present ovalbumin (OVA) and the enhancement was also demonstrated in the macrophages of cocaine-injected mice. The presentation of an OVA-derived antigenic peptide (OVA323-339), however, was not affected. In vitro cocaine treatment neither affected antigen uptake nor major histocompatibility complex (MHC) II expression and the expression of co-stimulatory molecules B7. These results suggest that cocaine may act on an early event in the antigen handling by accessory cells.

Amount and fate of egg protein escaping assimilation in the small intestine of humans

Studies attempting to evaluate protein assimilation in humans have hitherto relied on either ileostomy subjects or intubation techniques. The availability of stable isotope-labeled protein allowed us to determine the amount and fate of dietary protein escaping digestion and absorption in the small intestine of healthy volunteers using noninvasive tracer techniques. Ten healthy volunteers were studied once after ingestion of a cooked test meal, consisting of 25 g of (13)C-, (15)N-, and (2)H-labeled egg protein, and once after ingestion of the same but raw meal. Amounts of 5.73% and 35.10% (P < 0.005) of cooked and raw test meal, respectively, escaped digestion and absorption in the small intestine. A significantly higher percentage of the malabsorbed raw egg protein was recovered in urine as fermentation metabolites. These results 1) confirm that substantial amounts of even easily digestible proteins may escape assimilation in healthy volunteers and 2) further support the hypothesis that the metabolic fate of protein in the colon is affected by the amount of protein made available.

Epithelial permeability to proteins in the noninflamed ileum of Crohn's disease?

BACKGROUND & AIMS

Crohn's disease (CD) is associated with a disturbed intestinal barrier. Permeability studies have focused on inert molecules, but little is known about transepithelial transport of macromolecules with antigenic potential in humans. The aim of this study was to quantify permeation and to characterize passage routes for macromolecules in ileal mucosa in CD.

METHODS

Noninflamed and inflamed ileal mucosa specimens from patients with CD (n = 12) and ileal specimens from patients with colon cancer (n = 7) were studied regarding transmucosal permeation of ovalbumin, dextran (mol wt, 40,000), and 51Cr-EDTA for 90 minutes in vitro in Ussing chambers. Transepithelial passage routes for fluorescent ovalbumin and dextran 40,000 were investigated by confocal microscopy.

RESULTS

Noninflamed ileum from CD patients showed increased permeation of ovalbumin compared with ileum from colon cancer patients (P < 0.05). Dextran permeation was equal in the three groups, whereas 51Cr-EDTA permeability was increased in inflamed ileum. Ovalbumin passed both transcellularly and paracellularly, but dextran followed a strictly paracellular route. Both markers were subsequently endocytosed by cells of the lamina propria.

CONCLUSIONS

Noninflamed ileal mucosa from patients with CD shows increased epithelial permeability to ovalbumin, probably by augmented transcytosis. This increase in antigen load to the lamina propria could be an initiating pathogenic event in CD.

Biodegradable lamellar particles of poly(lactide) induce sustained immune responses to a single dose of adsorbed protein

The adjuvanticity of lamellar particles of poly(L-lactide) (PLA) towards adsorbed ovalbumin (OVA) was investigated. The aim of vaccine formulation was to maximise the amount of antigen retained on the particles and the time of retention during incubation of the formulations in PBS at 37 degrees C. Unmodified PLA lamellae were capable of adsorbing large quantities of OVA (up to 12.5% w/w) but major and rapid desorption occurred in PBS at 37 degrees C (80% released in 24 h). Retention of OVA on PLA lamellae was improved (25% released in 24 h) by precipitating the particles using aqueous sodium deoxycholate solution (DOC-modified PLA lamellae and lyophilising the lamellae-protein preparation after adsorption. Sustained immune responses were elicited in mice to a single sub-cutaneous injection of OVA adsorbed onto DOC-modified PLA lamellae. The level of antibodies induced and the pattern of response was similar to that induced by an alum-adsorbed OVA formulation. Normally boosting is required to obtain high levels of antibody when OVA is adsorbed on poly(DL-lactide co-glycolide) (PLG) microspheres. The lamellar forms of PLA may function as an efficient immunomodulator by effectively retaining adsorbed antigen and by activating immune cells due to their irregular shape. PLA lamellae have potential to stimulate enhanced immune responses to a variety of adsorbed antigens.

Prediction of permeability-surface area product data by continuous-distribution pore models

OBJECTIVE

To investigate the ability of continuous-distribution pore models to accurately predict permeability-surface area product (PS) experimental data in skeletal muscle.

METHODS

Models having a water-only (WO) pathway and continuous distributions of microvascular transport-pathway sizes were fit to solute reflection-coefficient (sigma) experimental data (approximately 0.5-16 nm Stokes radii) obtained from skeletal muscle to determine optimal parameter values. Without further modification, these models were used to predict experimental PS values obtained from the literature for small solutes ranging in size from NaCl to inulin and for three proteins, alpha-lactalbumin, ovalbumin, and albumin (approximately 0.23-3.7 nm radii). The protein PSs were determined from fluorescent tracer-diffusion curves and a nonlinear model of tracer diffusion in the cat hindlimb preparation. The model's PS predictions were compared to those of a discrete-pore model previously developed and a fiber-matrix (FM) model.

RESULTS

A log-normal (LN) continuous pore-size distribution plus WO-pathway model (three free parameters) fit the sigma data to within the 95% confidence intervals of each of eight solutes spanning a 32-fold size range and was nearly as close to the data as was the two discrete-pore plus WO-pathway model (four free parameters). Both models closely described the PS data for nine solutes spanning a 14-fold size range. The fit of a fiber-matrix plus WO-pathway model (three free parameters) to the sigma data was much poorer than for the other models.

CONCLUSIONS

The LN and two-discrete-pore models accurately describe sigma and PS experimental data in cat and human skeletal muscle. Therefore, experimental data resulting from complex microvascular transport processes are well characterized by simple pore models.