Oral tolerance elicited in mice by beta-lactoglobulin entrapped in biodegradable microspheres

Allergen immunotherapy: progress and future outlook

INTRODUCTION

Allergy, the immunological hypersensitivity to innocuous environmental compounds, is a global health problem. The disease triggers, allergens, are mostly proteins contained in various natural sources such as plant pollen, animal dander, dust mites, foods, fungi and insect venoms. Allergies can manifest with a wide range of symptoms in various organs, and be anything from just tedious to life-threatening. A majority of all allergy patients are self-treated with symptom-relieving medicines, while allergen immunotherapy (AIT) is the only causative treatment option.

AREAS COVERED

This review will aim to give an overview of the state-of-the-art allergy management, including the use of new biologics and the application of biomarkers, and a special emphasis and discussion on current research trends in the field of AIT.

EXPERT OPINION

Conventional AIT has proven effective, but the years-long treatment compromises patient compliance. Moreover, AIT is typically not offered in food allergy. Hence, there is a need for new, effective and safe AIT methods. Novel routes of administration (e.g. oral and intralymphatic), hypoallergenic AIT products and more effective adjuvants holds great promise. Most recently, the development of allergen-specific monoclonal antibodies for passive immunotherapy may also allow treatment of patients currently not treated or treatable.

PLGA Particles in Immunotherapy

Poly(lactic-co-glycolic acid) (PLGA) particles are a widely used and extensively studied drug delivery system. The favorable properties of PLGA such as good bioavailability, controlled release, and an excellent safety profile due to the biodegradable polymer backbone qualified PLGA particles for approval by the authorities for the application as a drug delivery platform in humas. In recent years, immunotherapy has been established as a potent treatment option for a variety of diseases. However, immunomodulating drugs rely on targeted delivery to specific immune cell subsets and are often rapidly eliminated from the system. Loading of PLGA particles with drugs for immunotherapy can protect the therapeutic compounds from premature degradation, direct the drug delivery to specific tissues or cells, and ensure sustained and controlled drug release. These properties present PLGA particles as an ideal platform for immunotherapy. Here, we review recent advances of particulate PLGA delivery systems in the application for immunotherapy in the fields of allergy, autoimmunity, infectious diseases, and cancer.

Resistance of parvalbumin to gastrointestinal digestion is required for profound and long-lasting prophylactic oral tolerance

Background

Early introduction of food allergens into children's diet is considered as a strategy for the prevention of food allergy. The major fish allergen parvalbumin exhibits high stability against gastrointestinal digestion. We investigated whether resistance of carp parvalbumin to digestion affects oral tolerance induction.

Methods

Natural Cyp c 1, nCyp c 1, and a gastrointestinal digestion‐sensitive recombinant Cyp c 1 mutant, mCyp c 1, were analyzed for their ability to induce oral tolerance in a murine model. Both antigens were compared by gel filtration, circular dichroism measurement, in vitro digestion, and splenocyte proliferation assays using synthetic Cyp c 1‐derived peptides. BALB/c mice were fed once with high doses of nCyp c 1 or mCyp c 1, before sensitization to nCyp c 1. Immunological tolerance was studied by measuring Cyp c 1‐specific antibodies and cellular responses by ELISA, basophil activation, splenocyte proliferations, and intragastric allergen challenge.

Results

Wild‐type and mCyp c 1 showed the same physicochemical properties and shared the same major T‐cell epitope. However, mCyp c 1 was more sensitive to enzymatic digestion in vitro than nCyp c 1. A single high‐dose oral administration of nCyp c 1 but not of mCyp c 1 induced long‐term oral tolerance, characterized by lack of parvalbumin‐specific antibody and cellular responses. Moreover, mCyp c 1‐fed mice, but not nCyp c 1‐fed mice developed allergic symptoms upon challenge with nCyp c 1.

Conclusion

Sensitivity to digestion in the gastrointestinal tract influences the capacity of an allergen to induce prophylactic oral tolerance.

Adjuvants for allergy immunotherapeutics

Allergic diseases are reaching epidemic proportions in developed countries. In particular, food allergy is increasing in prevalence and severity, thus becoming an important socioeconomic burden. Numerous cell types and cell populations, which form an intricate and balanced network, are involved in an immune response. This balance is occasionally disturbed, leading to the onset of different diseases, such as allergic diseases. Antihistamines and corticosteroids provide some degree of relief from the symptoms of allergic conditions. However, the only treatment that can revert the disease is immunotherapy. Nevertheless, specific immunotherapy has at least 2 major drawbacks: it is time-consuming, and it can produce local and even systemic allergic side effects. Immunotherapy's potential goes beyond our current knowledge of the immune response; nevertheless, we can still design strategies to reach a safer immune modulation for treating allergies. This review deals with the use of adjuvants to reduce the undesirable side effects associated with specific allergen immunotherapy. For example, nanoparticles used as immunoadjuvants are offering promising results in preclinical assays.

Probing the modulated formation of gold nanoparticles-beta-lactoglobulin corona complexes and their applications

Understanding the interactions between proteins and nanoparticles (NPs) along with the underlying structural and dynamic information is of utmost importance to exploit nanotechnology for biomedical applications. Upon adsorption onto a NP surface, proteins form a well-organized layer, termed the corona, that dictates the identity of the NP-protein complex and governs its biological pathways. Given its high biological relevance, in-depth molecular investigations and applications of NPs-protein corona complexes are still scarce, especially since different proteins form unique corona patterns, making identification of the biomolecular motifs at the interface critical. In this work, we provide molecular insights and structural characterizations of the bio-nano interface of a popular food-based protein, namely bovine beta-lactoglobulin (β-LG), with gold nanoparticles (AuNPs) and report on our investigations of the formation of corona complexes by combined molecular simulations and complementary experiments. Two major binding sites in β-LG were identified as being driven by citrate-mediated electrostatic interactions, while the associated binding kinetics and conformational changes in the secondary structures were also characterized. More importantly, the superior stability of the corona led us to further explore its biomedical applications, such as in the smartphone-based point-of-care biosensing of Escherichia coli (E. coli) and in the computed tomography (CT) of the gastrointestinal (GI) tract through oral administration to probe GI tolerance and functions. Considering their biocompatibility, edible nature, and efficient excretion through defecation, AuNPs-β-LG corona complexes have shown promising perspectives for future in vitro and in vivo clinical settings.

PLGA nanoparticles loaded with beta-lactoglobulin-derived peptides modulate mucosal immunity and may facilitate cow's milk allergy prevention

Beta-lactoglobulin (BLG)-derived peptides may facilitate oral tolerance to whey and prevent cow's milk allergy (CMA). Loading of BLG-peptides in poly(lactic-co-glycolic acid) (PLGA) nanoparticles (Pep-NP) may improve this. Here we studied the uptake of NP and the capacity of NP and Pep-NP to activate bone marrow dendritic cells (BMDC). Furthermore, CMA prevention was evaluated by orally exposing three-week-old female C3H/HeOuJ mice to Pep-NP, NP or free peptides (PepMix) for 6 days before oral sensitization with whole whey protein and effects on the spleen and small intestine lamina propria (SI-LP) were studied. In BMDC, NP and Pep-NP enhanced CD40 expression and IL-6 and TNF-α secretion, while tended to decrease CD80 expression and prevented PepMix-induced IL-12 secretion. In vivo, oral exposure to Pep-NP, but not NP or PepMix, prior to whey sensitization tended to partially prevent the acute allergic skin response to whole whey protein. Splenocytes of NP-pre-exposed mice secreted increased levels of whey-specific IL-6, but this was silenced in Pep-NP-pre-exposed mice which also showed reduced TNF-α and IFN-γ secretion. In the SI-LP, Pep-NP pre-exposure reduced the CD4⁺ T cell frequency in CMA mice compared to PBS pre-exposure. In addition, while NP increased whey-specific IL-6 secretion in the SI-LP, Pep-NP did not and maintained regulatory TGF-β secretion. This study presents a proof-of-concept that PLGA nanoparticles facilitate the capacity of BLG peptides to suppress the allergic response to whole whey protein. Hence, PLGA nanoparticles may be further developed as an adjunct strategy for BLG-peptide-based oral tolerance induction and CMA prevention.

Recent advances in the use of nanoparticles for allergen-specific immunotherapy

The number of patients suffering from allergic asthma and rhinoconjunctivitis has increased dramatically within the last decades. Allergen-specific immunotherapy (AIT) is the only available cause-oriented therapy so far. AIT reduces symptoms, but has also a disease-modifying effect. Disadvantages are a long-lasting procedure, and in a few cases potential systemic adverse reactions. Encapsulation of allergens or DNA vaccines into nanostructures may provide advantages compared to the conventional AIT with noncapsulated allergen extracts: The protein/DNA molecule can be protected from degradation, higher local concentrations and targeted delivery to the site of action appear possible, and most importantly, recognition of encapsulated allergen by the immune system, especially by IgE antibodies, is prevented. AIT with nanoparticles (NPs) may offer a safer and potentially more efficient way of treatment for allergic diseases. In this review, we summarize the use of biodegradable NPs consisting of synthetic or natural polymers, liposomes, and virus-like particles as well as nonbiodegradable NPs like dendrimers, and carbon- or metal-based NPs for AIT. More or less successful applications of these NPs in prophylactic as well as therapeutic vaccination approaches in rodents or other animals as well as first human clinical trials are discussed in detail.

New pharmaceutical approaches for the treatment of food allergies

INTRODUCTION

Allergic diseases constitute one of the most common causes of chronic illness in developed countries. The main mechanism determining allergy is an imbalance between Th1 and Th2 response towards Th2.

AREAS COVERED

This review describes the mechanisms underlying the natural tolerance to food components and the development of an allergic response in sensitized individuals. Furthermore, therapeutic approaches proposed to manage these abnormal immunologic responses food are also presented and discussed.

EXPERT OPINION

In the past, management of food allergies has consisted of the education of patients to avoid the ingestion of the culprit food and to initiate the therapy (e.g. self-injectable epinephrine) in case of accidental ingestion. In recent years, sublingual/oral immunotherapies based on the continuous administration of small amounts of the allergen have been developed. However, the long periods of time needed to obtain significant desensitization and the generation of adverse effects, limit their use. In order to solve these drawbacks, strategies to induce tolerance are being studied, such as the use of either adjuvant immunotherapy in order to facilitate the reversion of the Th2 response towards Th1 or the use of monoclonal antibodies to block the main immunogenic elements.

Evaluation of the immune response following a short oral vaccination schedule with hepatitis B antigen encapsulated into alginate-coated chitosan nanoparticles

The purpose of this work was to assess the ability of recombinant hepatitis B vaccine, encapsulated in alginate-coated chitosan nanoparticles, to induce local and systemic immune responses following oral vaccination. The antigen was administered either alone or in combination with the immunopotentiator, synthetic oligodeoxynucleotide containing immunostimulatory CpG motif (CpG ODN) as adjuvant, and associated or not with the alginate-coated chitosan nanoparticles. After two immunizations the group I (HBsAg associated with nanoparticles) and the group VI (HBsAg and CpG, both associated with nanoparticles) showed enhanced immune responses. Both groups showed significant higher values of the CD69 expression in CD4+ and CD8+ T-lymphocytes and lower values of this marker in B lymphocytes. Moreover, a strongest proliferative response of the splenocytes, ex vivo stimulated with concanavalin A, was observed in the same groups. Although with a presence of non-responder mice within the groups, only mice of the groups I and VI elicited the generation of anti-HBsAg antibodies detected in serum (IgG) and in the intestinal washings (sIgA). The results demonstrated that coated chitosan nanoparticles might have potential for being used as a deliver system for oral vaccination with the recombinant hepatitis B surface antigen.

Development of hepatitis B oral vaccine using B-cell epitope loaded PLG microparticles

Oral hepatitis B vaccine formulation was prepared by successful encapsulation of immunogenic peptide representing residues 127-145 of the immunodominant B-cell epitope of hepatitis B surface antigen (HBsAg) in poly(D,L-lactide co-glycolide) (PLG) microparticles. The smooth, spherical PLG microparticles with a diameter of around 10 microm was prepared by using W/O/W double emulsion solvent evaporation method. The entrapment efficiency of B-cell epitope peptide (BCEP) into PLG microparticles was 64%. In vitro studies showed B-cell epitope loaded PLG microparticles (BCEM) released the peptide in sustained profile and reached 64.9% efficiency by Day 25. Single oral immunization of mice with BCEM led to the significant induction of specific serum IgG and IgM anti-HB antibodies. After the termination of antibody induction, the orally immunized mice were infected with HBsAg, which resulted in the rapid production of antibodies against HBsAg as a result of secondary immune response. PLG microparticles formulation approach may have potential in increasing the efficacy of microparticulate systems for the oral administration of hepatitis B vaccine.

Biodegradable PLGA Particles for Improved Systemic and Mucosal Treatment of Type I Allergy

Although allergen immunotherapy is basically a story of success, it still needs improvement. The goal of this study was to optimize parenteral and oral allergen formulations through using the biocompatible polymer of lactic and glycolic acid (PLGA). Subcutaneous application of birch pollen allergen Bet v 1 encapsulated in nanoparticles biased the immune response toward Th1 in allergic mice and did not elicit granuloma formation in mice and in human volunteers. When oral immunotherapy of mice was tried with birch pollen-filled PLGA microparticles, mucosal targeting was indispensable for achieving any immune response, and targeting of M-cells was necessary for modulating an ongoing allergic response toward Th1. The authors suggest that biocompatible PLGA nano- or microparticles can be useful tools for upgrading therapy of type I allergy.

Cow's milk allergy: a complex disorder

Cow's milk allergy (CMA) is a complex disorder. Numerous milk proteins have been implicated in allergic responses and most of these have been shown to contain multiple allergenic epitopes. There is considerable heterogeneity amongst allergic individuals for the particular proteins and epitopes to which they react, and to further complicate matters, allergic reactions to cow's milk are driven by more than one immunological mechanism. Finally, the incidence and dominant allergic mechanisms change with age, with IgE-mediated reactions common in infancy and non-IgE-mediated reactions dominating in adults. The complexity of CMA has lead to many public misconceptions about this disorder, including confusion with lactose intolerance and frequent self-misdiagnosis. Indeed, the prevalence of self-diagnosed CMA in the community is 10-fold higher than the clinically proven incidence, suggesting a sizable population is unnecessarily eschewing dairy products. Avoidance of dairy foods, whether for true or perceived CMA, carries with it nutritional consequences and the provision of appropriate nutritional advice is important. In this review, the epidemiology and natural course of CMA is discussed along with our current understanding of its triggers and immunological mechanisms. We examine current strategies for the primary and secondary prevention of allergic sensitization and the ongoing search for effective therapies to ultimately cure CMA.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.

Microparticles for oral delivery of vaccines

Nonreplicating antigens are poorly immunogenic when given orally, either due to their degradation in the gastrointestinal tract or because they are not efficiently taken up in the gut. Studies in laboratory animals have clearly demonstrated that microparticles can significantly improve the immunogenicity of orally administered antigens. However, the oral delivery of vaccines using microparticles has not been explored extensively in humans and large animals. In this article the progress in oral microparticle antigen delivery will be reviewed and, where possible, studies in humans and large animals will be highlighted. In addition, possible approaches that have the potential to significantly improve microparticle delivery of oral vaccines will be suggested.

Is there a role for plant‐made vaccines in the prevention of HIV/AIDS?

Although educational programs have had some impact, immunization against HIV will be necessary to control the AIDS pandemic. To be effective, vaccination will need to be accessible and affordable, directed against multiple antigens, and delivered in multiple doses. Plant-based vaccines that are heat-stable and easy to produce and administer are suited to this type of strategy. Pilot studies by a number of groups have demonstrated that plant viral expression systems can produce HIV antigens in quantities that are appropriate for use in vaccines. In addition, these plant-made HIV antigens have been shown to be immunogenic. However, given the need for potent cross-clade humoral and T-cell immunity for protection against HIV, and the uncertainty surrounding the efficacy of protein subunit vaccines, it is most likely that plant-made HIV vaccines will find their niche as booster immunizations in prime-boost vaccination schedules.

M cell targeting with Aleuria aurantia lectin as a novel approach for oral allergen immunotherapy

BACKGROUND

The extent and quality of the immune response to orally applied allergens may critically depend on the precise site of uptake at the intestinal mucosa.

OBJECTIVE

The aim of this study was to construct allergen vehicles optimized for oral allergen immunotherapy.

METHODS

By using a murine model, we examined the immunomodulatory effect of birch pollen proteins entrapped in poly(D,L-lactide-co-glycolide) microspheres, which were specifically targeted to enterocytes or to M cells, in an ongoing T h 2 response. BALB/c mice express different carbohydrates on these 2 cell types. To target the sialylic residues on murine enterocytes, we functionalized microspheres with wheat germ agglutinin (WGA) and, to target alpha-L-fucose on M cells, with a lectin from Aleuria aurantia (AAL), the orange peel mushroom.

RESULTS

Both WGA and AAL functionalization enhanced binding to human Caco2 cells substantially, which express sialylic and, as carcinoma cells, also alpha-L-fucose residues. Different groups of BALB/c mice were first sensitized to birch pollen and subsequently fed with birch pollen-loaded functionalized (WGA microspheres, AAL microspheres) or nonfunctionalized, birch pollen extract-loaded particles. When mice were fed with AAL microspheres, birch pollen-specific IgG2a, but not IgG1 or IgE, increased significantly. As expected, in a 3 H-thymidin assay, their splenocytes proliferated specifically on birch pollen stimulation. Both targeting strategies, using WGA or AAL, induced IL-10 as well as IL-4 production. However, in AAL microsphere-treated mice, IFN-gamma synthesis was significantly increased, which may be responsible for the significant IgG2a production in this group.

CONCLUSION

Our data indicate that targeting M cells by using AAL-coated allergen vehicles may be a promising strategy for oral allergen immunotherapy.

Functionalisation of allergen-loaded microspheres with wheat germ agglutinin for targeting enterocytes

In this study, we constructed particles applicable for oral immunotherapy of type I allergy by protecting allergens from digestion and supporting intestinal antigen uptake. Therefore, birch-pollen allergens were entrapped in poly(d,l-lactic-co-glycolic acid) microspheres by spray-drying rendering microspheres with a main population of 1-3microm. Microspheres were further coated with wheat germ agglutinin (WGA) to target enterocytes. Coating with WGA did not alter the surface characteristics of the microspheres as demonstrated in scanning electron microscopy. Binding of WGA was specific and could be inhibited by chitotriose to 14.7+/-6.9%. Comparable amounts of allergen were released from both particle-types with 46.3+/-1.7% and 44.5+/-2.6% during 21 days. Simulating gastric digestion in vitro, antigenicity of allergens entrapped in WGA-microspheres was preserved to 59.8+/-1.5% even after 2h. Feedings of BALB/c mice with WGA-microspheres induced higher levels of allergen-specific IgG-levels than gavages of uncoated microparticles or naked protein. Thus, we conclude that WGA-microspheres are suitable vehicles for oral delivery and mucosal targeting due to lectin-mediated bioadhesion.

Immune response after oral administration of the encapsulated malaria synthetic peptide SPf66

The synthetic peptide SPf66 adsorbed on alum is one of the few Plasmodium falciparum vaccines which have been tested in field trials. We previously reported that subcutaneous administration of SPf66 loaded PLGA microparticles (MP) enhances the antibody response to this antigen compared to the conventional alum formulation. We now evaluate the suitability of polymeric formulations to obtain systemic immune responses by gastric intubation of Balb/c mice. Formulations composed of 1:1 mixtures of PLGA 50:50 and 75:25 (lactic:glycolic) microparticles were administered by the oral route, and when animals were boosted 3 weeks later significant systemic IgG antibody responses were elicited, comparable to alum triple shot and superior to the aqueous vaccine given by the oral route. The finding of IgG2a isotype for PLGA-vaccinated mice compared to the absent levels of this isotype for the alum-vaccinated group could be interpreted as a sign of Th1-like immune response and cellular immune response activation. Our results confirm that using the appropriate schedule the oral administration of PLGA particles is suitable to obtain systemic immune responses to the carried antigen.

Tissue compatibility of two biodegradable tubular scaffolds implanted adjacent to skin or buccal mucosa in mice

Radiation therapy for cancer in the head and neck region leads to a marked loss of salivary gland parenchyma, resulting in a severe reduction of salivary secretions. Currently, there is no satisfactory treatment for these patients. To address this problem, we are using both tissue engineering and gene transfer principles to develop an orally implantable, artificial fluid-secreting device. In the present study, we examined the tissue compatibility of two biodegradable substrata potentially useful in fabricating such a device. We implanted in Balb/c mice tubular scaffolds of poly-L-lactic acid (PLLA), poly-glycolic acid coated with PLLA (PGA/PLLA), or nothing (sham-operated controls) either beneath the skin on the back, a site widely used in earlier toxicity and biocompatibility studies, or adjacent to the buccal mucosa, a site quite different functionally and immunologically. At 1, 3, 7, 14, and 28 days postimplantation, implant sites were examined histologically, and systemic responses were assessed by conventional clinical chemistry and hematology analyses. Inflammatory responses in the connective tissue were similar regardless of site or type of polymer implant used. However, inflammatory reactions were shorter and without epithelioid and giant cells in sham-operated controls. Also, biodegradation proceeded more slowly with the PLLA tubules than with the PGA/PLLA tubules. No significant changes in clinical chemistry and hematology were seen due to the implantation of tubular scaffolds. These results indicate that the tissue responses to PLLA and PGA/PLLA scaffolds are generally similar in areas subjacent to skin in the back and oral cavity. However, these studies also identified several potentially significant concerns that must be addressed prior to initiating any clinical applications of this device.

Suppression of collagen-induced arthritis by single administration of poly(lactic-co-glycolic acid) nanoparticles entrapping type II collagen: a novel treatment strategy for induction of oral tolerance

OBJECTIVE

Poly(lactic-co-glycolic acid) (PLGA), a biodegradable polymer, is a carrier for drug delivery systems. This study was undertaken to investigate the tolerogenic effect of single administration of PLGA entrapping type II collagen (CII) on the development of collagen-induced arthritis (CIA).

METHODS

The biophysical properties of PLGA nanoparticles entrapping CII (PLGA-CII) were investigated by in vitro release testing of CII, immunohistochemistry analysis, and electron microscopy. PLGA-CII was fed singly to animals 14 days before immunization, and the effect on joint inflammation was assessed. Circulating IgG anti-CII antibodies and T cell responses to CII in draining lymph nodes were assayed by enzyme-linked immunosorbent assay and (3)H-thymidine incorporation assay, respectively. The expression of messenger RNA (mRNA) for transforming growth factor beta (TGFbeta) and tumor necrosis factor alpha (TNFalpha) was determined by reverse transcriptase-polymerase chain reaction.

RESULTS

The in vitro release test showed that CII was slowly discharged from PLGA-CII over a period of a month. After single administration of PLGA-CII, numerous particles approximately 300 nm in size were detectable in Peyer's patches, by electron microscopy and immunohistochemical staining for CII, 14 days after the original feeding. Mice fed a single dose of PLGA containing 40 microg of CII had significantly reduced values for incidence and severity of arthritis, serum IgG anti-CII antibodies, and CII-specific T cell proliferation as compared with mice fed solvent alone, those fed 6 doses of 20 microg CII alone, and those fed a single dose of PLGA alone. PLGA-CII was also able to suppress CIA after disease onset. Moreover, PLGA-CII-fed mice showed a higher level of TGFbeta mRNA expression in Peyer's patches, but a lower level of TNFalpha mRNA expression in draining lymph nodes, compared with the other groups of mice.

CONCLUSION

Our data show that PLGA may serve as a powerful vehicle to promote the tolerance effect of oral CII and that single administration of PLGA-CII may hold promise as a new treatment strategy in rheumatoid arthritis.

Biodegradable poly (DL-lactide glycolide) microparticles as a vehicle for allergen-specific vaccines: a study performed with Ole e 1, the main allergen of olive pollen

Ole e 1, the main allergen of the olive pollen, was entrapped in poly (DL-lactide glycolide) microparticles by a solvent evaporation double emulsion technique. The physical properties of the microparticles, such as particle size, surface morphology, allergen entrapment rate and antigen release pattern were investigated. Microparticles with a spherical morphology displayed a size range of less than 2 microm in diameter and antigen loading up to 60-70% (w/w). SDS-PAGE and immunoblotting of the released Ole e 1 confirmed that the molecular integrity and the antigenic properties of Ole e 1 remained unaltered by the encapsulation process or polymer degradation. This finding suggests that microparticles displaying small particle sizes, rapid antigen release and a high allergen/polymer ratio may be a suitable delivery system for antigen in hyposensitization therapy against allergy.

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.