Immunological responses to nasal delivery of free and encapsulated tetanus toxoid: studies on the effect of vehicle volume

Surface Modification of Biodegradable Microparticles with the Novel Host-Derived Immunostimulant CPDI-02 Significantly Increases Short-Term and Long-Term Mucosal and Systemic Antibodies against Encapsulated Protein Antigen in Young Naïve Mice after Respiratory Immunization

Generating long-lived mucosal and systemic antibodies through respiratory immunization with protective antigens encapsulated in nanoscale biodegradable particles could potentially decrease or eliminate the incidence of many infectious diseases, but requires the incorporation of a suitable mucosal immunostimulant. We previously found that respiratory immunization with a model protein antigen (LPS-free OVA) encapsulated in PLGA 50:50 nanoparticles (~380 nm diameter) surface-modified with complement peptide-derived immunostimulant 02 (CPDI-02; formerly EP67) through 2 kDa PEG linkers increases mucosal and systemic OVA-specific memory T-cells with long-lived surface phenotypes in young, naïve female C57BL/6 mice. Here, we determined if respiratory immunization with LPS-free OVA encapsulated in similar PLGA 50:50 microparticles (~1 μm diameter) surface-modified with CPDI-02 (CPDI-02-MP) increases long-term OVA-specific mucosal and systemic antibodies. We found that, compared to MP surface-modified with inactive, scrambled scCPDI-02 (scCPDI-02-MP), intranasal administration of CPDI-02-MP in 50 μL sterile PBS greatly increased titers of short-term (14 days post-immunization) and long-term (90 days post-immunization) antibodies against encapsulated LPS-free OVA in nasal lavage fluids, bronchoalveolar lavage fluids, and sera of young, naïve female C57BL/6 mice with minimal lung inflammation. Thus, surface modification of ~1 μm biodegradable microparticles with CPDI-02 is likely to increase long-term mucosal and systemic antibodies against encapsulated protein antigen after respiratory and possibly other routes of mucosal immunization.

Development of experimental silicosis in inbred and outbred mice depends on instillation volume

There is considerable variation in methods to induce experimental silicosis with the effects of dose and route of exposure being well documented. However, to what extent the volume of silica suspension alters the dispersion and severity of silicosis has not been adequately investigated. In this study, the optimal volume of a crystalline silica suspension required to obtain uniform distribution and greatest incidence and severity of silicosis was determined in inbred and outbred mice. Silica dispersal, detected by co-inspiration with India ink and polarized light microscopy, was highly dependent upon volume. Furthermore, although peribronchitis, perivasculitis, and increases in bronchoalveolar lavage fluid cell numbers were detected a lower doses and volumes, significant alveolitis required exposure to 5 mg of silica in 50 μl. This dose and volume of transoral instillation led to a greater penetrance of silicosis in the genetically heterogeneous Diversity Outbred strain as well as greater alveolar inflammation typical of the silicosis in human disease. These findings underscore the critical importance of instillation volume on the induction, severity, and type of inflammatory pathology in experimental silicosis.

PvdQ Quorum Quenching Acylase Attenuates Pseudomonas aeruginosa Virulence in a Mouse Model of Pulmonary Infection

Pseudomonas aeruginosa is the predominant pathogen in pulmonary infections associated with cystic fibrosis. Quorum sensing (QS) systems regulate the production of virulence factors and play an important role in the establishment of successful P. aeruginosa infections. Inhibition of the QS system (termed quorum quenching) renders the bacteria avirulent thus serving as an alternative approach in the development of novel antibiotics. Quorum quenching in Gram negative bacteria can be achieved by preventing the accumulation of N-acyl homoserine lactone (AHL) signaling molecule via enzymatic degradation. Previous work by us has shown that PvdQ acylase hydrolyzes AHL signaling molecules irreversibly, thereby inhibiting QS in P. aeruginosa in vitro and in a Caenorhabditis elegans model of P. aeruginosa infection. The aim of the present study is to assess the therapeutic efficacy of intranasally instilled PvdQ acylase in a mouse model of pulmonary P. aeruginosa infection. First, we evaluated the deposition pattern of intranasally administered fluorochrome-tagged PvdQ (PvdQ-VT) in mice at different stages of pulmonary infection by in vivo imaging studies. Following intranasal instillation, PvdQ-VT could be traced in all lung lobes with 42 ± 7.5% of the delivered dose being deposited at 0 h post-bacterial-infection, and 34 ± 5.2% at 72 h post bacterial-infection. We then treated mice with PvdQ during lethal P. aeruginosa pulmonary infection and that resulted in a 5-fold reduction of lung bacterial load and a prolonged survival of the infected animals with the median survival time of 57 hin comparison to 42 h for the PBS-treated group. In a sublethal P. aeruginosa pulmonary infection, PvdQ treatment resulted in less lung inflammation as well as decrease of CXCL2 and TNF-α levels at 24 h post-bacterial-infection by 15 and 20%, respectively. In conclusion, our study has shown therapeutic efficacy of PvdQ acylase as a quorum quenching agent during P. aeruginosa infection.

Microneedle Vaccination Elicits Superior Protection and Antibody Response over Intranasal Vaccination against Swine-Origin Influenza A (H1N1) in Mice

Influenza is one of the critical infectious diseases globally and vaccination has been considered as the best way to prevent. In this study, immunogenicity and protection efficacy between intranasal (IN) and microneedle (MN) vaccination was compared using inactivated swine-origin influenza A/H1N1 virus vaccine. Mice were vaccinated by MN or IN administration with 1 μg of inactivated H1N1 virus vaccine. Antigen-specific antibody responses and hemagglutination-inhibition (HI) titers were measured in all immunized sera after immunization. Five weeks after an immunization, a lethal challenge was performed to evaluate the protective efficacy. Furthermore, mice were vaccinated by IN administration with higher dosages (> 1 μg), analyzed in the same manner, and compared with 1 μg-vaccine-coated MN. Significantly higher antigen-specific antibody responses and HI titer were measured in sera in MN group than those in IN group. While 100% protection, slight weight loss, and reduced viral replication were observed in MN group, 0% survival rate were observed in IN group. As vaccine dose for IN vaccination increased, MN-immunized sera showed much higher antigen-specific antibody responses and HI titer than other IN groups. In addition, protective immunity of 1 μg-MN group was similar to those of 20- and 40 μg-IN groups. We conclude that MN vaccination showed more potential immune response and protection than IN vaccination at the same vaccine dosage.

Biomaterials for nanoparticle vaccine delivery systems

Subunit vaccination benefits from improved safety over attenuated or inactivated vaccines, but their limited capability to elicit long-lasting, concerted cellular and humoral immune responses is a major challenge. Recent studies have demonstrated that antigen delivery via nanoparticle formulations can significantly improve immunogenicity of vaccines due to either intrinsic immunostimulatory properties of the materials or by co-entrapment of molecular adjuvants such as Toll-like receptor agonists. These studies have collectively shown that nanoparticles designed to mimic biophysical and biochemical cues of pathogens offer new exciting opportunities to enhance activation of innate immunity and elicit potent cellular and humoral immune responses with minimal cytotoxicity. In this review, we present key research advances that were made within the last 5 years in the field of nanoparticle vaccine delivery systems. In particular, we focus on the impact of biomaterials composition, size, and surface charge of nanoparticles on modulation of particle biodistribution, delivery of antigens and immunostimulatory molecules, trafficking and targeting of antigen presenting cells, and overall immune responses in systemic and mucosal tissues. This review describes recent progresses in the design of nanoparticle vaccine delivery carriers, including liposomes, lipid-based particles, micelles and nanostructures composed of natural or synthetic polymers, and lipid-polymer hybrid nanoparticles.

Mucosal vaccination against tuberculosis using inert bioparticles

Needle-free, mucosal immunization is a highly desirable strategy for vaccination against many pathogens, especially those entering through the respiratory mucosa, such as Mycobacterium tuberculosis. Unfortunately, mucosal vaccination against tuberculosis (TB) is impeded by a lack of suitable adjuvants and/or delivery platforms that could induce a protective immune response in humans. Here, we report on a novel biotechnological approach for mucosal vaccination against TB that overcomes some of the current limitations. This is achieved by coating protective TB antigens onto the surface of inert bacterial spores, which are then delivered to the respiratory tract. Our data showed that mice immunized nasally with coated spores developed humoral and cellular immune responses and multifunctional T cells and, most importantly, presented significantly reduced bacterial loads in their lungs and spleens following pathogenic challenge. We conclude that this new vaccine delivery platform merits further development as a mucosal vaccine for TB and possibly also other respiratory pathogens.

Allergen challenge during halothane compared to isoflurane anesthesia induces a more potent peripheral lung response

Allergen instillation in anaesthetized vs. awake animals results in increased distribution of allergen in the lung. Halothane is a more potent bronchodilator of the small airways than isoflurane. As small airways contribute to asthma pathogenesis, we questioned whether intranasal challenge under halothane vs. isoflurane anesthesia would lead to an increase in allergen deposition in the lung periphery and, consequently, an enhanced allergic response. C57Bl/6 mice were sensitized twice and repeatedly challenged with ovalbumin (OA) under halothane or isoflurane anesthesia. After OA-challenge, in vivo lung function was measured and BAL performed. Peribronchial and peripheral inflammation, cytokine mRNA production and collagen deposition were assessed. Airway hyperresponsiveness, BAL eosinophilia, peripheral lung inflammation, IL-5 mRNA production and collagen deposition were significantly increased in halothane OA-challenged compared to isoflurane OA-challenged mice. Airway challenge induced a higher level of airway hyperresponsiveness, inflammation and remodeling under halothane than isoflurane anesthesia in a murine model of asthma. These differences may be due to increased allergen deposition in the small airways.

Development and characterization of surface modified PLGA nanoparticles for nasal vaccine delivery: effect of mucoadhesive coating on antigen uptake and immune adjuvant activity

In this study, the efficacy of mucoadhesive polymers, i.e., chitosan and glycol chitosan as a mucoadhesive coating material in nasal vaccine delivery was investigated. The Hepatitis B surface Antigen (HBsAg) encapsulated PLGA, chitosan coated PLGA (C-PLGA), and Glycol chitosan coated PLGA (GC-PLGA) nanoparticles (NPs) were prepared. The formulations were characterized for particle size, shape, surface charge, and entrapment efficiency. The mucoadhesive ability of coated and non-coated NPs was determined using in vitro mucoadhesion and nasal clearance test. In addition, the systemic uptake and bio-distribution were also evaluated to understand the fate of NPs following nasal delivery. The immuno-adjuvant ability of various formulations was compared by measuring specific antibody titer in serum and secretory. The results indicated that PLGA NPs exhibit negative surface charge, whereas C-PLGA and GC-PLGA NPs exhibited positive surface charge. The GC-PLGA NPs demonstrated lower clearance and better local and systemic uptake compared to chitosan coated and uncoated PLGA NPs. In vivo immunogenicity studies indicated that GC-PLGA NPs could induce significantly higher systemic and mucosal immune response compared to PLGA and C-PLGA NPs. In conclusion, GC-PLGA NPs could be a promising carrier adjuvant for the nasal vaccine delivery for inducing a potent immune response at mucosal surface(s) and systemic circulation.

Formulation, characterization and release studies of alginate microspheres encapsulated with tetanus toxoid

Alginate is a safe, non-immunogenic and inexpensive natural polymer with high mucoadhesive properties. Alginate microspheres can be used as a delivery system for antigens to mucosal surfaces. In the present study alginate microspheres were prepared by an emulsification technique. The effects of sonication time, concentration of alginate, emulsifier and calcium chloride, and also the volume of calcium solution, were evaluated on mean size, size range, surface roughness and porosity, sphericity and clumping of microspheres using an optical microscope and particle size analyzer. The most desirable conditions were 90 s sonication, 3% alginate solution, 2% surfactant and 60 ml of 0.33% CaCl2 in octanol. The resulting microspheres had a mean size of 1.34 +/- 0.3 microm and size range of 0.3 +/- 2.0 microm, with no surface roughness and porosity, low clumping and high sphericity. The encapsulation efficiency was about 47.7%. All batches showed nearly the same release profiles with a low burst release. The stability of the model antigen (tetanus toxoid (TT)) extracted from microspheres was confirmed by SDS-PAGE; and the antigenicity of TT was studied by ELISA and found to be 91 +/- 5% of the original TT. It can be concluded that, with regard to the size and morphological characteristics of the prepared microspheres and their ability in preserving the antigenicity of the encapsulated TT, they could be used as a delivery system for mucosal delivery of TT.

Dry powder vaccines for mucosal administration: critical factors in manufacture and delivery

Dry powder vaccine formulations have proved effective for induction of systemic and mucosal immune responses. Here we review the use of dry vaccines for immunization in the respiratory tract. We discuss techniques for powder formulation, manufacture, characterization and delivery in addition to methods used for evaluation of stability and safety. We review the immunogenicity and protective efficacy of dry powder vaccines as compared to liquid vaccines delivered by mucosal or parenteral routes. Included is information on mucosal adjuvants and mucoadhesives that can be used to enhance nasal or pulmonary dry vaccines. Mucosal immunization with dry powder vaccines offers the potential to provide a needle-free and cold chain-independent vaccination strategy for the induction of protective immunity against either systemic or mucosal pathogens.

Preparation and in vivo study of dry powder microspheres for nasal immunization

The immunoadjuvant potential of alginate microspheres as delivery system, and cross-linked dextran microspheres (CDM) as absorption enhancer and excipient for powder of alginate microspheres, were evaluated. Alginate microspheres were prepared by emulsification method. Microspheres encapsulated with tetanus toxoid (TT) or Quillaja saponin (QS) were nasally administered to rabbits, three times in 2 weeks interval and serum IgG and nasal lavage sIgA titers were determined by ELISA. The mean diameter of microspheres was about 1.5 mum. Release of TT and QS was 13.1 +/- 1.4% and 31.8 +/- 4.3% after 4 h. The serum IgG titer induced with (TT)(ALG) microspheres was higher than TT solution (P<0.001). Addition of QS or CDM adjuvant, in separate, to (TT)(ALG) microspheres could not significantly increase the immune responses (P>0.05), but the highest systemic IgG titers induced with (TT+QS)(ALG)+CDM (P<0.01). The sIgA titer induced with (TT)(ALG) microspheres was higher than TT solution (P<0.05). The highest mucosal sIgA titers were seen in animals immunized with (TT)(ALG)+CDM (P<0.05). Co-encapsulation of QS and TT in microspheres did not increase the sIgA titers. When CDM was added to alginate microspheres encapsulated with TT or TT+QS, the highest mucosal and systemic responses were observed.

Tissue distribution of radioactivity following intranasal administration of radioactive microspheres

The aim of this study was to increase understanding of the kinetics of microparticle distribution and elimination following intranasal application. To do this we investigated the in-vivo distribution of radioactivity following intranasal instillation of scandium-46 labelled styrene-divinyl benzene 7-μm-diameter microspheres. Groups of BALB/c mice received 0.250 mg (47.5 kBq) particles suspended in either 50-μl or 10-μl volumes of phosphate buffered saline. The in-vivo distribution of radioactivity was influenced by the volume of liquid that was used to instil the microsphere suspension. Comparatively large (50 μl) administration vehicle volumes resulted in substantial bronchopulmonary deposition (∼ 50% of administered dose). Intranasal instillation of microspheres suspended in 10-μl volumes tended to restrict particle deposition initially to the nasal cavity. For both administration vehicle volumes tested, the radioactivity per unit mass of excised nasal-associated lymphoid tissue (NALT) was found to be consistently elevated relative to other tissues. This corroborates the findings of other workers who have previously identified NALT as an active site of microparticle accumulation following intranasal application. Elimination via the alimentary canal was the principal fate of intranasally applied radiolabeled material. No significant concentration of radioactivity within excised gut-associated lymphoid tissue (GALT) (Peyer's patches) was noted. At latter time points we observed, in mice that received the 50-μl volume particle suspension nasally, accumulation of potentially relevant quantities of radioactivity in the liver (0.3% after 576 h) and spleen (0.04% after 576 h). Thus, our data corroborate the notion that epithelial membranes in the lung are probably less exclusive to the entry of microparticulates into systemic compartments than are those mucosae in the gastrointestinal tract or nasopharynx. This effect may contribute to the effectiveness of pulmonary delivered antigen-loaded microparticles as humoral immunogens.

Dextran microspheres could enhance immune responses against PLGA nanospheres encapsulated with tetanus toxoid and Quillaja saponins after nasal immunization in rabbit

Potent immunoadjuvants are needed to elicit responses following mucosal delivery. PLGA (poly[D,L-lactic-co-glycolic acid]) nanospheres, Quillaja saponin (QS) and cross-linked dextran microspheres (CDM) as drug delivery and absorption enhancer adjuvants were evaluated. PLGA nanospheres were prepared by solvent evaporation method. Particulate characteristics of nanospheres were studied by optical and scanning electron microscopes and dynamic light scattering technique. The mean diameter of nanospheres encapsulated with TT and TT + QS determined as 425 and 390 nm. Loadings of TT and QS were 30 ± 1.9% and 23 ± 2.8%. Nanospheres encapsulated with TT or QS were intranasally administered to rabbits, three times in two-week intervals and the serum IgG and nasal lavage IgA titers were determined by ELISA. The serum IgG titer induced with (TT)(PLGA) nanospheres was higher than TT solution (P < 0.001). IgG titers induced with (TT + QS)(PLGA) was higher than (TT)(PLGA) (P < 0.0001). When (TT)(PLGA) and (TT + QS)(PLGA) nanospheres were mixed with CDM, higher IgG titers were induced (P < 0.001). The highest mucosal sIgA titers were seen in animals immunized with (TT + QS)(PLGA) + CDM. Co-encapsulation of QS and TT in PLGA nanospheres increased sIgA titers. In conclusion, the highest immune responses were observed by concomitant use of three adjuvants.

Impact of chitosan coating of anionic liposomes on clearance rate, mucosal and systemic immune responses following nasal administration in rabbits

Liposomes have been identified as effective immunological adjuvants and have potential for the intranasal and oral delivery of protein antigen. Anionic MLV liposomes were prepared by dehydration-rehydration method. For coating, liposomes were incubated in chitosan solution. Efficiency of coating was confirmed by the evaluation of FITC-labelled chitosan-coated liposomes using a fluorescent microscope. Liposomes morphology and size were studied by optical microscope and size analyzer. Mucoadhesion potential of liposomes was evaluated in human nose by gamma-scintigraphy using (99m)Tc-labelled liposomes. Rabbits (4 animals per group) were nasally immunized in weeks 0, 2 and 4 by liposomes encapsulated with 40 Lf TT. Bleedings and lavage collections were taken place in weeks 3 and 6, and IgG and sIgA titers were measured by ELISA method. Liposomes had a mean diameter of 2.38 microm. Loading of TT was 58.7+/-12.4%. The mucoadhesion (clearance rate from nose) of both coated and non-coated liposomes was similar (P>0.05). Among the immunized animals, the highest nasal lavage sIgA titers were seen in non-coated liposomes followed by coated ones. The serum IgG titers (2nd bleeding) in animals immunized by both kinds of liposome were similar (P>0.05), and were lower than the TT solution group (P<0.05). Immunization by i.m. injection of TT solution resulted in the lowest sIgA and highest IgG titers (P<0.05) compared with liposomal groups. The results were indicative of good potential of negatively charged liposomes in the induction of mucosal immunity. Coating of liposomes by chitosan, failed to increase both the residence time of liposomes in nasal cavity and systemic responses. Conversely, coated liposomes could not induce the mucosal responses as efficiently as non-coated liposomes. It seems that the coating of liposomes affected their interaction potential with nasal associated lymphoid tissue cells.

Effect of vitamin E TPGS on immune response to nasally delivered diphtheria toxoid loaded poly(caprolactone) microparticles

The nasal mucosa has many advantages as a potential site for drug and vaccine delivery. The present study has sought to exploit this route of delivery using microparticles composed of D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as a matrix material blended with poly(caprolactone) for nasal immunisation with diphtheria toxoid. Particles were prepared by a double emulsion method, followed by spray drying and the effect of TPGS on size, zeta potential, loading and release of antigen was assessed. Particles composed of TPGS-PCL blends were spherical, smooth and monodisperse, displaying increasing yields after spray drying with increasing concentrations of TPGS. The immune response to diphtheria toxoid loaded PCL-TPGS microspheres after nasal administration was shown to be higher than that achieved using PCL microspheres alone. We conclude that TPGS shows significant potential as a novel adjuvant either alone or in combination with an appropriate delivery system.

Mucosal delivery of microparticle encapsulated ESAT-6 induces robust cell-mediated responses in the lung milieu

ESAT-6 from Mycobacterium tuberculosis is an important T-cell antigen for cell-mediated immunity in the early phase of tuberculosis infection. Since the lung is the organ in which infection is initiated, immune responses in the lung play a significant role in restricting the initial infection with M. tuberculosis. The aim of the present study was to assess whether efficient cell-mediated immune responses in the lung and draining mediastinal lymph nodes could be stimulated by pulmonary administration of ESAT-6 encapsulated in poly(lactide) (PLA) microspheres. BALB/c mice were immunised intranasally on days 1, 28 and 56 with 2 microg microencapsulated ESAT-6. Cellular responses in the lungs, spleen and mediastinal lymph nodes (MLN) were characterised using ELISPOT and proliferation assays. Fluorescence activated cell sorting (FACS) was used to assess the expression of CD44 on CD4+ and CD8+ cells derived from the MLN of immunised animals. For comparison, groups of mice were immunised intranasally with soluble 'free' ESAT-6 or intramuscularly with ESAT-6 in Alhydrogel. Intranasal instillation of microencapsulated ESAT-6 induced greatest numbers of ESAT-6 specific IFN-gamma and IL-4 secreting cells in the lung and MLN (P<0.05). Similarly, ESAT-6 specific recall responses were strongest following intranasal immunisation of mice with microsphere encapsulated antigen (P<0.05). FACS demonstrated a higher proportion of T cells expressing CD44 in the MLN from mice immunised intranasally with microencapsulated ESAT-6. These data support the notion that the immune system is compartmentalised and responses are often strongest in compartments proximal to the site of vaccine application. Furthermore, our data indicate that, for efficient activation of cell-mediated responses, antigens must be presented to the immune system in an appropriate formulation.

CpG-DNA protects against a lethal orthopoxvirus infection in a murine model

CpG-DNA has been described as a potent activator of the innate immune system, with potential to protect against infection caused by a range of pathogens in a non-specific manner. Here two classes of CpG-DNA (CpG-A and CpG-B) have been investigated for their abilities to protect mice from infection with an orthopoxvirus (vaccinia virus). Dosing with either CpG-A or B by the intraperitonal or intranasal route protected mice against a subsequent intranasal challenge with vaccinia virus. To our knowledge, this is the first time CpG-mediated protection has been demonstrated at the lung surface. The level of protection was greater when CpG-DNA was administered intranasally demonstrating a clear relationship between the route of CpG dosing and infection route. Treatment with CpG-B reduced viral titer in the lung by 10,000-fold at day 3 post-infection. The CC chemokines RANTES and MIP-1beta were elevated in the broncho-alveolar lavage from animals treated intranasally with CpG-B compared to untreated and intraperitoneally dosed controls, and it is possible that these chemokines play a role in the clearance of intranasally delivered vaccinia virus.

Low molecular weight chitosan nanoparticles as new carriers for nasal vaccine delivery in mice

High molecular weight (Mw) chitosan (CS) solutions have already been proposed as vehicles for nasal immunization. The aim of the present work was to investigate the potential utility of low Mw CS in the form of nanoparticles as new long-term nasal vaccine delivery vehicles. For this purpose, CS of low Mws (23 and 38 kDa) was obtained previously by a depolymerization process of the commercially available CS (70 kDa). Tetanus toxoid (TT), used as a model antigen, was entrapped within CS nanoparticles by an ionic cross-linking technique. TT-loaded nanoparticles were first characterized for their size, electrical charge, loading efficiency and in vitro release of antigenically active toxoid. The nanoparticles were then administered intranasally to conscious mice in order to study their feasibility as vaccine carriers. CS nanoparticles were also labeled with FITC-BSA and their interaction with the rat nasal mucosa examined by confocal laser scanning microcopy (CLSM). Irrespective of the CS Mw, the nanoparticles were in the 350 nm size range, and exhibited a positive electrical charge (+40 mV) and associated TT quite efficiently (loading efficiency: 50-60%). In vitro release studies showed an initial burst followed by an extended release of antigenically active toxoid. Following intranasal administration, TT-loaded nanoparticles elicited an increasing and long-lasting humoral immune response (IgG concentrations) as compared to the fluid vaccine. Similarly, the mucosal response (IgA levels) at 6 months post-administration of TT-loaded CS nanoparticles was significantly higher than that obtained for the fluid vaccine. The CLSM images indicated that CS nanoparticles can cross the nasal epithelia and, hence, transport the associated antigen. Interestingly, the ability of these nanoparticles to provide improved access to the associated antigen to the immune system was not significantly affected by the CS Mw. Indeed, high and long-lasting responses could be obtained using low Mw CS molecules. Furthermore, the response was not influenced by the CS dose (70-200 microg), achieving a significant response for a very low CS dose. In conclusion, nanoparticles made of low Mw CS are promising carriers for nasal vaccine delivery.

Recombinant cholera toxin B subunit (rCTB) as a mucosal adjuvant enhances induction of diphtheria and tetanus antitoxin antibodies in mice by intranasal administration with diphtheria-pertussis-tetanus (DPT) combination vaccine

Recombinant cholera toxin B subunit (rCTB) which is produced by Bacillus brevis carrying pNU212-CTB acts as a mucosal adjuvant capable of enhancing host immune responses specific to unrelated, mucosally co-administered vaccine antigens. When mice were administered intranasally with diphtheria-pertussis-tetanus (DPT) combination vaccine consisting of diphtheria toxoid (DTd), tetanus toxoid (TTd), pertussis toxoid (PTd), and formalin-treated filamentous hemagglutinin (fFHA), the presence of rCTB elevated constantly high values of DTd- and TTd-specific serum ELISA IgG antibody titres, and protective levels of diphtheria and tetanus toxin-neutralizing antibodies but the absence of rCTB did not. Moreover, the addition of rCTB protected all mice against tetanic symptoms and deaths. DPT combination vaccine raised high levels of serum anti-PT IgG antibody titres regardless of rCTB and protected mice from Bordetella pertussis challenge. These results suggest that co-administration of rCTB as an adjuvant is necessary for induction of diphtheria and tetanus antitoxin antibodies on the occasion of intranasal administration of DPT combination vaccine.

PEG-PLA nanoparticles as carriers for nasal vaccine delivery

This report presents an overview of the potential of nanoparticles as nasal carriers for drug/vaccine administration. In addition, this report shows, for the first time, the efficacy of polylactic acid nanoparticles coated with a hydrophilic polyethyleneglycol coating (PEG-PLA nanoparticles) as carriers for the nasal transport of bioactive compounds. For this purpose, tetanus toxoid (TT), a high molecular weight protein (Mw 150,000 Da), was chosen as a model antigen and encapsulated in the PEG-PLA nano- and microparticles (200 nm and 1.5 microm respectively). These nanosystems were first characterized for their stability in the presence of lysozyme and also for their size, electrical charge, loading efficiency, in vitro release of antigenically active toxoid and afterwards, these formulations were administered intranasally to mice and the systemic and mucosal anti-tetanus responses were evaluated for up to 24 weeks. Additionally, PEG-PLA particles labeled with rhodamine 6G were administered intranasally to rats in order to visualize their interaction with the nasal mucosae by fluorescence microscopy. Their behavior was compared with that of the well known PLA nanoparticles (200 nm). The results showed that PLA nanoparticles suffered an immediate aggregation upon incubation with lysozyme, whereas the PEG-coated nanoparticles remained totally stable. The antibody levels elicited following i.n. administration of PEG-coated nanoparticles were significantly higher than those corresponding to PLA nanoparticles. Furthermore, PEG-PLA nanoparticles generated an increasing and a long lasting response. The qualitative fluorescence microscopy studies revealed that PEG-PLA particles are able to cross the rat nasal epithelium. These studies indicate that the PEG coating around the particles has a role in stabilizing PLA particles in mucosal fluids and that it facilitates the transport of the nanoencapsulated antigen, hence eliciting a high and long lasting immune response.

In vivo uptake of an experimental microencapsulated diphtheria vaccine following sub-cutaneous immunisation

Previous studies demonstrated in vitro phagocytosis of poly(lactide-co-glycolide) (PLGA) microspheres (MS) by macrophages and dendritic cells and the biodistribution of fluorescent PLGA particles following oral or intranasal administration. In this study, we report the uptake and biodistribution of sub-cutaneously administered fluorescent labelled PLGA MS loaded with diphtheria toxoid (DT). The cell type and percentage of fluorescent positive cells were determined by flow cytometry and confirmed by fluorescent microscopy. Fluorescent particles were detected inside cells of the peritoneal flush as early as 10 min post-inoculation, predominantly in cells of macrophage morphology. In vivo trafficking of PLGA particles following a sub-cutaneous immunisation of mice appeared to be governed by macrophages. However, in the first week after inoculation, dendritic cells played a significant role in the uptake and digestion of the microspheres, thereby triggering the immune response against the antigen. Fluorescent PLGA MS were also observed in cells of lymphoid tissues such as mesenteric lymph nodes (MLN) and spleen (S). However, microsphere fluorescence in lymphoid tissues decreased rapidly, as they were degraded inside the cells, thereby enabling the presentation of the antigen to specific cells of the immune system. To our knowledge, this is the first time the fate of immunogenic PLGA microspheres was studied in vivo following a sub-cutaneous injection route.

Mutants of plasminogen activator inhibitor-1 designed to inhibit neutrophil elastase and cathepsin G are more effective in vivo than their endogenous inhibitors

Neutrophil elastase and cathepsin G are abundant intracellular neutrophil proteinases that have an important role in destroying ingested particles. However, when neutrophils degranulate, these proteinases are released and can cause irreparable damage by degrading host connective tissue proteins. Despite abundant endogenous inhibitors, these proteinases are protected from inhibition because of their ability to bind to anionic surfaces. Plasminogen activator inhibitor type-1 (PAI-1), which is not an inhibitor of these proteinases, possesses properties that could make it an effective inhibitor of neutrophil proteinases if its specificity could be redirected. PAI-1 efficiently inhibits surface-sequestered proteinases, and it efficiently mediates rapid cellular clearance of PAI-1-proteinase complexes. Therefore, we examined whether PAI-1 could be engineered to inhibit and clear neutrophil elastase and cathepsin G. By introducing specific mutations in the reactive center loop of wild-type PAI-1, we generated PAI-1 mutants that are effective inhibitors of both proteinases. Kinetic analysis shows that the inhibition of neutrophil proteinases by these PAI-1 mutants is not affected by the sequestration of neutrophil elastase and cathepsin G onto surfaces. In addition, complexes of these proteinases and PAI-1 mutants are endocytosed and degraded by lung epithelial cells more efficiently than either the neutrophil proteinases alone or in complex with their physiological inhibitors, alpha1-proteinase inhibitor and alpha1-antichymotrypsin. Finally, the PAI-1 mutants were more effective in reducing the neutrophil elastase and cathepsin G activities in an in vivo model of lung inflammation than were their physiological inhibitors.

Potent, long lasting systemic antibody levels and mixed Th1/Th2 immune response after nasal immunization with malaria antigen loaded PLGA microparticles

The immunogenicity of the synthetic malaria vaccine SPf66 has been recently improved by the application of new adjuvants as QS-21 saponin or poly-D,L-lactide-co-glycolide (PLGA) polymers. The search for less invasive administration routes made us test the immunogenicity of SPf66-loaded microparticles by the nasal route in Balb/c mice. We report here that the intranasal administration of the adequate PLGA vaccine formulations greatly improves and maintains higher antibody levels compared to the conventional alum adjuvant and to the administration of the particles by other routes (subcutaneous, oral). Systemic immune responses were characterized as mixed Th1/Th2-type: IFN-gamma and IgG2a isotype were found as signs of Th1 activation, whilst IgE and IgG1 secretions indicate Th2 response. Since both types of response have been associated to protective immunity in malaria, we postulate that this new approach supposes an advantage over the traditional adjuvants and routes.

Size dependent immune response after subcutaneous, oral and intranasal administration of BSA loaded nanospheres

BSA was entrapped in particles of different sizes (200, 500 and 1000 nm) prepared from poly(D,L-lactic-co-glycolic) acid by a double emulsion method. The particles were given, either intranasally, orally or subcutaneously, to Balb/c mice and the serum IgG, IgG1 and IgG2a response elicited was compared to that obtained by the subcutaneous administration of either free antigen, free antigen emulsified 1:1 with Freund's Complete Adjuvant (FCA), or free antigen administered with Al(OH)(3). The administration of 1000 nm particles generally elicited a higher serum IgG response than that obtained with the administration of 500 or 200 nm sized nanospheres, the immune response for 500 nm particles being similar than that obtained with 200 nm by the subcutaneous and the oral route, and higher by the intranasal route. PLGA nanoparticles can elicit serum IgG2a responses by the three routes studied. No significant differences on the serum IgG2a/IgG1 ratios were found after the subcutaneous, the oral and the intranasal administration of the different spheres but those were in general higher compared to the administration of either free antigen or free antigen adsorbed to alum. The route of administration influences the serum IgG2a/IgG1 ratio after the administration of free antigen, but not after the administration of the particles. Therefore, differences on the total serum IgG response induced by particles of different sizes do not result in differences on the IgG1 or IgG2a-type immune responses, suggesting that the antigen processing and presentation is similar in all cases tested for PLGA particles.

The effects of intranasal budesonide on allergen-induced production of interleukin-5 and eotaxin, airways, blood, and bone marrow eosinophilia, and eosinophil progenitor expansion in sensitized mice

We have previously demonstrated that allergen inhalation induces expansion of bone marrow eosinophil progenitors in sensitized mice and subjects with asthma and that the inhaled corticosteroid, budesonide, reduced baseline but not allergen-induced increase in bone marrow eosinophil/basophil progenitors (EoB-CFU) in subjects with asthma. Here, we evaluated the effects of intranasal budesonide on allergen-induced increases in interleukin (IL)-5 and eotaxin in the airway and peripheral blood, expansion of bone marrow Eo-CFU and eosinophilia in bone marrow, peripheral blood and airway, as well as airway hyperresponsiveness, in ovalbumin (OVA)-sensitized mice. Budesonide treatment attenuated allergen-induced eosinophilia in bone marrow, peripheral blood, and airways as well as allergen-induced increases in bone marrow eosinophil progenitors but not allergen-induced increases in IL-5 or eotaxin 12 h following the second of two daily exposures to allergen; at later time points treatment was associated with attenuation of IL-5, eosinophilia, Eo-CFU, and airway hyperresponsiveness. These results suggest that a component of the mechanism by which corticosteroid treatment attenuates allergen-induced airway inflammation is through suppression of bone marrow eosinophilopoiesis, and that this is likely not mediated simply through the blocking of IL-5 production at the airway.

Influence of dose and immunization route on the serum Ig G antibody response to BSA loaded PLGA microspheres

BSA was entrapped into PLGA 50:50 microspheres and the in vitro release study was performed. Then 1 microg of microencapsulated antigen was subcutaneously administered to Balb/c mice and the serum Ig G response was compared to that obtained after the subcutaneous administration of the same amount of only free antigen or of free antigen emulsified 1:1 with Freund's complete adjuvant (FCA). The specific serum Ig G responses obtained from the microencapsulated antigen were higher than those obtained from the free antigen and similar to those obtained from the antigen emulsified with FCA. Therefore, the immune response obtained with the subcutaneous administration of 1 microg of microencapsulated antigen was used as a positive control to compare the immune response elicited by the administration of the spheres either by the oral or the intranasal route. There is a dose/response relationship in the serum Ig G response elicited after three consecutive oral administrations of microencapsulated antigen at a dosing range from 200 to 50 microg. However, this relationship does not seem to be clear for the intranasal administration of the spheres at the same dosing range. When comparing the serum Ig G responses at each dosing level for the different routes of administration, it can be observed that the intranasal route is a more powerful inducer of the production of specific Ig G antibody than the oral, which could be due to a greater permeability of the nasal epithelium and to qualitative differences between the mechanisms of induction of the immune response by each route. The serum Ig G2a versus Ig G1 ratio is not significantly different among all the groups that received antigen in microspheres.

Distribution of intranasal instillations in mice: effects of volume, time, body position, and anesthesia

Intranasal instillation techniques are used to deliver various substances to the upper and lower respiratory tract (URT and LRT) in mice. Here, we quantify the relative distribution achieved with intranasal delivery of a nonabsorbable tracer, (99m)Tc-labeled sulfide-colloid. Relative distribution was determined by killing mice after instillation and quantifying the radioactivity in dissected tissues using gamma scintigraphy. A significant effect of delivery volume on relative distribution was observed when animals were killed 5 min after instillation delivered under gas anesthesia. With a delivery volume of 5 microl, no radiation was detected in the LRT; this increased to a maximum of 55.7 +/- 2.5% distribution to the LRT when 50 microl were delivered. The majority of radiation not detected in the LRT was found in the URT. Over the course of the following 1 h, radiation in the LRT remained constant, while that in the URT decreased and appeared in the gastrointestinal tract. Instillation of 25 microl into anesthetized mice resulted in 30.1 +/- 6.9% distribution to the LRT, while only 5.3 +/- 1.5% (P < 0.05) of the same volume was detected in the LRT of awake mice. Varying the body position of mice did not affect relative distribution. When using intranasal instillation, the relative distribution between the URT and LRT and the gastrointestinal tract is heavily influenced by delivery volume and level of anesthesia.

Microparticles for intranasal immunization

Of the several routes available for mucosal immunization, the nasal route is particularly attractive because of ease of administration and the induction of potent immune responses, particularly in the respiratory and genitourinary tracts. However, adjuvants and delivery systems are required to enhance immune responses following nasal immunization. This review focuses on the use of microparticles as adjuvants and delivery systems for protein and DNA vaccines for nasal immunization. In particular we discuss our own work on poly(lactide co-glycolide) (PLG) microparticles with entrapped protein or adsorbed DNA as a vaccine delivery system. The possible mechanisms involved in the enhancement of immune responses through the use of DNA adsorbed onto PLG microparticles are also discussed.

Nasal vaccines

The nasal route for vaccination offers some important opportunities, especially for the prophylaxis of respiratory diseases. Vaccination via the respiratory tract is reviewed and the deposition and clearance of antigens in the deep lung and nose are described and contrasted. Lymphoid structures in the respiratory tract differ according to species; the rat and mouse have a well developed nose-associated lymphoid tissue, while in man, the structure known as Waldeyer's ring (that includes the tonsils), is important as an induction site. The immune response following intranasal administration can provide protection at the administration site and at various effector sites as part of the common mucosal immune system. A number of formulation considerations are important when designing novel systems for nasal administration as are physiological factors such as mucociliary clearance.

Synthetic biomimetic supra molecular Biovector (SMBV) particles for nasal vaccine delivery

For the optimal delivery of antigens to mucosal tissues, especially as nasal sprays, protein antigen alone is often not sufficient. A clear need for nasal delivery systems has therefore evolved, especially for Influenza A vaccines. Such technologies will be even more essential for new modern vaccines based on recombinant antigens. Here we describe synthetic biomimetic supra molecular Biovector (SMBV) which have proven in preclinical and clinical evaluation to be suitable candidates for the delivery of nasal vaccines. They also demonstrate the potential to work with multiple antigens and furthermore allow combination with adjuvants. These Biovectors can associate with internal or lipid layer membrane proteins and peptides due to their charged polysaccharide core. The mimicry with viruses is also provided through their size of 60-80 nm, which allows sterilization by filtration. This makes them an ideal tool for the development of modern nasal vaccines, as they have shown to be able to induce the desired types of humoral immunity (serosal and mucosal immunity, IgA and IgG antibodies) as well as cellular immunity (CD4 and CD8 responses).

Microsphere translocation and immunopotentiation in systemic tissues following intranasal administration

With a view to developing improved mucosal immunisation strategies, we have quantitatively investigated the uptake of fluorescent polystyrene carboxylate microspheres (1.1 microm diameter), using histology and fluorescence-activated cell sorting, following intranasal delivery to BALB/c mice. To qualify these biodistribution data, antigen specific memory and effector responses in the spleens of mice immunised nasally with Yersinia pestis V antigen loaded poly(lactide) (PLA) microspheres (1.5 microm diameter) were assessed at 4, 7 and 11 days. Irrespective of administration vehicle volume (10 or 50 microl), appreciable numbers of fluorescent microspheres were detected within nasal associated lymphoid tissues (NALT) and draining cervical lymph nodes. Nasal administration of the particles suspended in 50 microl volumes of phosphate-buffered saline (PBS) served to deposit the fluorescent microspheres throughout the respiratory tract (P<0.05). In these animals, appreciable particle uptake into the mediastinal lymph node was noted (P<0.05). Also, spleens removed from mice 10 days after fluorescent particle application contained significantly more microspheres if the suspension had been nasally instilled using a 50 microl volume (P<0.05). Appreciable memory (and effector from day 7) responses were detected in mediastinal lymph nodes removed from mice immunised nasally with 50 microl volumes of microparticulated or soluble V antigen. Immunological responses in splenic tissue removed 7 days after intranasal immunisation corroborated the thesis that the spleen can act as an inductive site following bronchopulmonary deposition of particulated antigen: upon exposure to V in vitro, splenic T-cells from mice nasally immunised with 50 microl volumes of microspheres incorporated statistically greater (P<0.05) quantities of [3H]thymidine into newly synthesised DNA than did T-cells from cohorts nasally immunised with 50 microl volumes of V in solution. Similarly, significant numbers of anti-V IgG secreting cells were only detected in spleens from mice immunised intramuscularly or nasally with microparticles. These immunological and biodistribution data support the tenet that, following an appropriate method of mucosal delivery, microparticles can translocate to tissues in the systemic compartment of the immune system and thence provoke immunological reactions therein.

Pharmacokinetics study of a novel chimeric single-chain variable fragment antibody against western equine encephalitis virus

A novel recombinant single-chain fragment variable (scFv) antibody against western equine encephalitis (WEE) virus has been previously constructed and partially characterized. The RS10B5huFc antibody was made by fusing an anti-WEE scFv to a human heavy-chain IgG1 constant region. The RS10B5huFc antibody was functional in binding to WEE virus in enzyme-linked immunosorbent assays (ELISAs), and the Fc domain of the antibody was capable of effector functions, such as binding to protein G and human complement. In this study, the RS10B5huFc antibody was further characterized by BIAcore analyses and was found to possess a binding affinity to a WEE virus epitope (K[D] = 9.14 x 10(-6) M), 4.5-fold lower than its parental mouse monoclonal antibody (MAb) 10B5 E7E2 (K[D] = 2 x 10(-6) M). No cross-reactivity was found between the RS10B5huFc antibody and three other alphaviruses (Sindbis virus [SIN], Venezuelan equine encephalitis [VEE] virus, and eastern equine encephalitis [EEE] virus). Pharmacokinetics studies showed that the RS10B5huFc antibody (free and encapsulated) was found to be retained in the lungs of mice for greater than 48 h when administered intranasally. In contrast, when administered intramuscularly to mice, the RS10B5huFc antibody was not detected in the lungs and only found in the liver and kidneys.

Immunopotentiating of mucosal and systemic antibody responses in mice by intranasal immunization with HLT-combined influenza virosomal vaccine

The mucosal vaccination strategy against influenza has been investigated by using influenza virosomal vaccine (IRIV) combined with two different adjuvants: the procholeragenoid (PCG) and the Escherichia coli heat labile toxin (HLT). A comparative study has been carried out on mice administered intranasally with these different formulations of influenza vaccine. PCG appears less effective than HLT in inducing an IgG response, but both the adjuvants elicit mucosal adjuvant activity inducing s-IgA in the upper respiratory tract. On the contrary, only HLT when administered intranasally to mice with influenza virosomes stimulates the production of s-IgA in the lower respiratory tract thereby providing a better protection against primary infection of the respiratory system. Both HLT and PCG enhance the production of IFN-gamma in the respiratory tract, nevertheless HLT appears more efficacious as a mucosal adjuvant.

Generation of protective immune responses to plague by mucosal administration of microsphere coencapsulated recombinant subunits

We have investigated noninvasive immunization to plague. Recombinant subunit antigens, F1 and V from Yersinia pestis, were coencapsulated in biodegradable poly(L100 LD(50's) inhalational challenge with virulent Y. pestis. These data expand on previous findings from our laboratories, providing further insight into the mechanics of safeguarding mice from plague through nasal immunization. Further, these results demonstrate that in a murine model, solid protection from pneumonic plague can be engendered by two intranasal administrations of appropriately formulated recombinant proteins.