Intrapulmonary distribution of deposited particles

A roadmap to pulmonary delivery strategies for the treatment of infectious lung diseases

Pulmonary drug delivery is a highly attractive topic for the treatment of infectious lung diseases. Drug delivery via the pulmonary route offers unique advantages of no first-pass effect and high bioavailability, which provides an important means to deliver therapeutics directly to lung lesions. Starting from the structural characteristics of the lungs and the biological barriers for achieving efficient delivery, we aim to review literatures in the past decade regarding the pulmonary delivery strategies used to treat infectious lung diseases. Hopefully, this review article offers new insights into the future development of therapeutic strategies against pulmonary infectious diseases from a delivery point of view.

Aerosolized Exposure to H5N1 Influenza Virus Causes Less Severe Disease Than Infection via Combined Intrabronchial, Oral, and Nasal Inoculation in Cynomolgus Macaques

Infection with highly pathogenic avian H5N1 influenza virus in humans often leads to severe respiratory disease with high mortality. Experimental infection in non-human primates can provide additional insight into disease pathogenesis. However, such a model should recapitulate the disease symptoms observed in humans, such as pneumonia and inflammatory cytokine response. While previous studies in macaques have demonstrated the occurrence of typical lesions in the lungs early after infection and a high level of immune activation, progression to severe disease and lethality were rarely observed. Here, we evaluated a routinely used combined route of infection via intra-bronchial, oral, and intra-nasal virus inoculation with aerosolized H5N1 exposure, with or without the regular collection of bronchoalveolar lavages early after infection. Both combined route and aerosol exposure resulted in similar levels of virus replication in nose and throat and similar levels of immune activation, cytokine, and chemokine release in the blood. However, while animals exposed to H5N1 by combined-route inoculation developed severe disease with high lethality, aerosolized exposure resulted in less lesions, as measured by consecutive computed tomography and less fever and lethal disease. In conclusion, not virus levels or immune activation, but route of infection determines fatal outcome for highly pathogenic avian H5N1 influenza infection.

Regional Lung Deposition: In Vivo Data

The method section of this chapter on in vivo regional lung deposition highlights a nonradioactive method to measure regional deposition, which uses a photometer to quantify inhaled and exhaled particles and in that way is able to estimate the lung region from which the particles are exhaled and to what amount. The radioactive methods cover the measurement of clearance of the deposited particles as well as different imaging techniques to determine regional deposition. The result section reviews in vivo trials in human subjects. It also addresses different parameters that influence the regional deposition in the lungs: particle size, inhalation maneuver, carrier gas, disease, and inhalation device. All of these factors can affect regional deposition significantly. By choosing specific values of these parameters, it should be feasible to target different regions of the lungs for the therapy of different diseases.

Aerosolized pH1N1 influenza infection induces less systemic and local immune activation in the lung than combined intrabronchial, nasal and oral exposure in cynomolgus macaques

Non-human primates form an important animal model for the evaluation of immunogenicity and efficacy of novel 'universal' vaccine candidates against influenza virus. However, in most studies a combination of intra-tracheal or intra-bronchial, oral and nasal virus inoculation is used with a standard virus dose of between 1 and 10 million tissue culture infective doses, which differs from typical modes of virus exposure in humans. This paper studies the systemic and local inflammatory and immune effects of aerosolized versus combined-route exposure to pandemic H1N1 influenza virus. In agreement with a previous study, both combined-route and aerosol exposure resulted in similar levels of virus replication in nose, throat and lung lavages. However, the acute release of pro-inflammatory cytokines and chemokines, acute monocyte activation in peripheral blood as well as increased cytokine production and T-cell proliferation in the lungs were only observed after combined-route infection and not after aerosol exposure. Longitudinal evaluation by computed tomography demonstrated persistence of lung lesions after resolution of the infection and a tendency for more lesions in the lower lung lobes after combined-route exposure versus upper and middle lung lobes after aerosol exposure. Computed tomography scores were observed to correlate with fever. In conclusion, influenza virus infection by aerosol exposure is accompanied by less immune-activation and inflammation in comparison with direct virus installation, despite similar levels of virus replication and development of lesions in the lungs.

Optimizing the Entrainment Geometry of a Dry Powder Inhaler: Methodology and Preliminary Results

PURPOSE

For passive dry powder inhalers (DPIs) entrainment and emission of the aerosolized drug dose depends strongly on device geometry and the patient's inhalation manoeuvre. We propose a computational method for optimizing the entrainment part of a DPI. The approach assumes that the pulmonary delivery location of aerosol can be determined by the timing of dose emission into the tidal airstream.

METHODS

An optimization algorithm was used to iteratively perform computational fluid dynamic (CFD) simulations of the drug emission of a DPI. The algorithm seeks to improve performance by changing the device geometry. Objectives were to achieve drug emission that was: A) independent of inhalation manoeuvre; B) similar to a target profile. The simulations used complete inhalation flow-rate profiles generated dependent on the device resistance. The CFD solver was OpenFOAM with drug/air flow simulated by the Eulerian-Eulerian method.

RESULTS

To demonstrate the method, a 2D geometry was optimized for inhalation independence (comparing two breath profiles) and an early-bolus delivery. Entrainment was both shear-driven and gas-assisted. Optimization for a delay in the bolus delivery was not possible with the chosen geometry.

CONCLUSIONS

Computational optimization of a DPI geometry for most similar drug delivery has been accomplished for an example entrainment geometry.

Mucosal delivery of a vectored RSV vaccine is safe and elicits protective immunity in rodents and nonhuman primates

Respiratory Syncytial Virus (RSV) is a leading cause of severe respiratory disease in infants and the elderly. No vaccine is presently available to address this major unmet medical need. We generated a new genetic vaccine based on chimpanzee Adenovirus (PanAd3-RSV) and Modified Vaccinia Ankara RSV (MVA-RSV) encoding the F, N, and M2-1 proteins of RSV, for the induction of neutralizing antibodies and broad cellular immunity. Because RSV infection is restricted to the respiratory tract, we compared intranasal (IN) and intramuscular (M) administration for safety, immunogenicity, and efficacy in different species. A single IN or IM vaccination completely protected BALB/c mice and cotton rats against RSV replication in the lungs. However, only IN administration could prevent infection in the upper respiratory tract. IM vaccination with MVA-RSV also protected cotton rats from lower respiratory tract infection in the absence of detectable neutralizing antibodies. Heterologous prime boost with PanAd3-RSV and MVA-RSV elicited high neutralizing antibody titers and broad T-cell responses in nonhuman primates. In addition, animals primed in the nose developed mucosal IgA against the F protein. In conclusion, we have shown that our vectored RSV vaccine induces potent cellular and humoral responses in a primate model, providing strong support for clinical testing.

Carbon loading in airway macrophages as a biomarker for individual exposure to particulate matter air pollution - A critical review

Exposure to particulate matter (PM) is associated with adverse health effects, including chronic lung diseases, lung cancer and cardiovascular disease. Personal exposure varies depending on the generation of particles locally, background levels, activity patterns and meteorology. Carbon loading in airway macrophages (AM) is a novel marker to assess personal exposure to combustion-derived particles. This review summarizes the published evidence and describes the validity and reliability of this marker with a focus on the technical aspects. Carbon loading in AM is reported in nine published studies assessing personal exposure to particulate air pollution. The carbon content is quantified by image analysis and is suggested to be suited to assess cumulative exposures. While there is some variation in study technique, these studies each indicate that internal AM carbon reflects either external exposure or important health effects. However, some uncertainty remains regarding potentially confounding materials within particles, the time frame of exposures that this technique reflects, and the optimal strategy to accurately quantify AM carbon. These aspects need to be clarified or optimized before applying this technique in larger populations.

Size-dependent uptake of particles by pulmonary antigen-presenting cell populations and trafficking to regional lymph nodes

The respiratory tract is an attractive target organ for novel diagnostic and therapeutic applications with nano-sized carriers, but their immune effects and interactions with key resident antigen-presenting cells (APCs) such as dendritic cells (DCs) and alveolar macrophages (AMs) in different anatomical compartments remain poorly understood. Polystyrene particles ranging from 20 nm to 1,000 nm were instilled intranasally in BALB/c mice, and their interactions with APC populations in airways, lung parenchyma, and lung-draining lymph nodes (LDLNs) were examined after 2 and 24 hours by flow cytometry and confocal microscopy. In the main conducting airways and lung parenchyma, DC subpopulations preferentially captured 20-nm particles, compared with 1,000-nm particles that were transported to the LDLNs by migratory CD11blow DCs and that were observed in close proximity to CD3⁺ T cells. Generally, the uptake of particles increased the expression of CD40 and CD86 in all DC populations, independent of particle size, whereas 20-nm particles induced enhanced antigen presentation to CD4⁺ T cells in LDLNs in vivo. Despite measurable uptake by DCs, the majority of particles were taken up by AMs, irrespective of size. Confocal microscopy and FACS analysis showed few particles in the main conducting airways, but a homogeneous distribution of all particle sizes was evident in the lung parenchyma, mostly confined to AMs. Particulate size as a key parameter determining uptake and trafficking therefore determines the fate of inhaled particulates, and this may have important consequences in the development of novel carriers for pulmonary diagnostic or therapeutic applications.

Genetic immunization in the lung induces potent local and systemic immune responses

Successful vaccination against respiratory infections requires elicitation of high levels of potent and durable humoral and cellular responses in the lower airways. To accomplish this goal, we used a fine aerosol that targets the entire lung surface through normal respiration to deliver replication-incompetent recombinant adenoviral vectors expressing gene products from several infectious pathogens. We show that this regimen induced remarkably high and stable lung T-cell responses in nonhuman primates and that it also generated systemic and respiratory tract humoral responses of both IgA and IgG isotypes. Moreover, strong immunogenicity was achieved even in animals with preexisting antiadenoviral immunity, overcoming a critical hurdle to the use of these vectors in humans, who commonly are immune to adenoviruses. The immunogenicity profile elicited with this regimen, which is distinct from either intramuscular or intranasal delivery, has highly desirable properties for protection against respiratory pathogens. We show that it can be used repeatedly to generate mucosal humoral, CD4, and CD8 T-cell responses and as such may be applicable to other mucosally transmitted pathogens such as HIV. Indeed, in a lethal challenge model, we show that aerosolized recombinant adenoviral immunization completely protects ferrets against H5N1 highly pathogenic avian influenza virus. Thus, genetic immunization in the lung offers a powerful platform approach to generating protective immune responses against respiratory pathogens.

The pathogenesis of acute pulmonary viral and bacterial infections: investigations in animal models

Acute viral and bacterial infections in the lower respiratory tract are major causes of morbidity and mortality worldwide. The proper study of pulmonary infections requires interdisciplinary collaboration among physicians and biomedical scientists to develop rational hypotheses based on clinical studies and to test these hypotheses in relevant animal models. Animal models for common lung infections are essential to understand pathogenic mechanisms and to clarify general mechanisms for host protection in pulmonary infections, as well as to develop vaccines and therapeutics. Animal models for uncommon pulmonary infections, such as those that can be caused by category A biothreat agents, are also very important because the infrequency of these infections in humans limits in-depth clinical studies. This review summarizes our understanding of innate and adaptive immune mechanisms in the lower respiratory tract and discusses how animal models for selected pulmonary pathogens can contribute to our understanding of the pathogenesis of lung infections and to the search for new vaccines and therapies.

Enhanced delivery of nebulised salbutamol during non-invasive ventilation

Non-invasive ventilation (NIV) is used to treat acute respiratory failure. Nebulised drugs can be delivered concurrently with NIV or during breaks from ventilatory support. We hypothesised that the amount of nebulised salbutamol inhaled when delivered via bi-level ventilation would be no different to the amount available directly from the same nebuliser. A standard bi-level ventilation circuit was attached to a lung model simulating adult respiration. Drug delivery was compared when salbutamol (5 mg) was nebulised at different positions in the circuit and separately, with no ventilator. The amount of salbutamol contained in various particle size fractions was also determined. Nebuliser position within the NIV circuit was critically important for drug delivery. Optimal delivery of salbutamol occurred with the expiration port between the facemask and nebuliser (647 ± 67 μg). This was significantly better than nebulisation without the ventilator (424 ± 61 μg; P < 0.01). Delivery when the nebuliser was positioned between the facemask and expiration port was 544 ± 85 μg. The amount of salbutamol contained in particles < 5 μm was significantly increased when the nebuliser was used in conjunction with bi-level ventilation (576 ± 60 μg vs 300 ± 43 μg, P < 0.001). We conclude that nebulised bronchodilator therapy, using a Cirrus jet nebuliser, during bi-level ventilation increases respirable particles likely to be inhaled when the nebuliser is optimally positioned within the circuit.

Measles aerosol vaccination

Measles ranks fifth among the five major childhood conditions which are responsible for 21% of all deaths in low and middle-income countries. Measles immunization is considered the most cost-effective public health intervention in the world. In recent years, there has been a critical need to identify alternative routes of measles immunization, which are rapid, reliable, cost-effective, needle-free, and suitable for use in mass campaigns. Aerosol administration of measles vaccines in mass campaigns was first proposed by Dr. Albert Sabin. We review the different clinical trials that have been conducted using the classic Mexican device as well as issues regarding vaccine strain, presentation, and manufacturer. Results of clinical trials indicate that the method is safe and immunogenic in infants and school age children. The viral inoculum will probably need to be increased when administered to infants. From the logistical point of view, the use of the aerosol method has not been evaluated in routine immunization although feasibility of its routine implementation was proved in mass campaigns in Mexico. Cost savings will probably be demonstrated. As to licensure, its compliance with the appropriate international regulatory requirements for medical aerosol delivery devices is in process.

Airway nitric oxide release is reduced after PBS inhalation in asthma

Exhaled nitric oxide (NO) is elevated in asthma, but the underlying mechanisms remain poorly understood. Recent results in subjects with asthma have reported a decrease in exhaled breath pH and ammonia, as well as altered expression and activity of glutaminase in both alveolar and airway epithelial cells. This suggests that pH-dependent nitrite conversion to NO may be a source of exhaled NO in the asthmatic airway epithelium. However, the anatomic location (i.e., airway or alveolar region) of this pH-dependent NO release has not been investigated and could impact potential therapeutic strategies. We quantified airway (proximal) and alveolar (peripheral) contributions to exhaled NO at baseline and then after PBS inhalation in stable (mild-intermittent to severe) asthmatic subjects (20-44 yr old; n = 9) and healthy controls (22-41 yr old; n = 6). The mean (SD) maximum airway wall flux (pl/s) and alveolar concentration (ppb) at baseline in asthma subjects and healthy controls was 2,530 (2,572) and 5.42 (7.31) and 1,703 (1,567) and 1.88 (1.29), respectively. Compared with baseline, there is a significant decrease in the airway wall flux of NO in asthma as early as 15 min and continuing for up to 60 min (maximum -28% at 45 min) after PBS inhalation without alteration of alveolar concentration. Healthy control subjects did not display any changes in exhaled NO. We conclude that elevated airway NO at baseline in asthma is reduced by inhaled PBS. Thus airway NO may be, in part, due to nitrite conversion to NO and is consistent with airway pH dysregulation in asthma.

Optimum peripheral drug deposition in patients with cystic fibrosis

In order to identify the optimum particle size and breathing pattern for high peripheral deposition of inhaled drugs in patients with cystic fibrosis, regional deposition in these patients was studied systematically as a function of particle size, inhalation volume and flow rate. Regional deposition was assessed using the single-breath regional deposition technique in which the concentration profile of inhaled and exhaled non-radioactive, monodisperse test particles is analyzed. Using this technique particle deposition within the functional dead space volume and peripherally can be assessed. Regional deposition was measured in 12 patients with cystic fibrosis using 2, 3, 4, and 5.5 microm particles, inhalation volumes of 500, 1000, 1500, and 2000 cm(3), and inhalation flow rates of 100, 250, 500, and 750 cm(3)/sec. Peripheral deposition was highest when 2-3-microm particles were inhaled with air-flow rates of 250-500 cm(3)/sec. With these parameters peripheral deposition increased with increasing inhalation volume and reached values of about 60% of the total drug inhaled. It has been shown that high peripheral drug deposition can be achieved in patients with CF when inhalations are performed using an optimized combination of particle size and breathing pattern.

A simple method of bronchoprovocation using a valved holding chamber

This study was undertaken to ascertain whether the use of a valved holding chamber (VHC) during bronchial provocation testing might increase lung deposition and repeatability of the test relative to the tidal breathing method. The 2-min tidal breathing results were compared to five inhalations from a VHC device in patients using the Pari-provoII nebulizer (MMD = 2.1mkm). Lung and mouth deposition, losses though the exhaled air and losses before aerosol delivery to the patient's mouth were measured in patients using a radiolabeled 99Tc-DTPA solution and gamma camera. The study revealed that lung deposition was 67% with the VHC method, and losses with exhaled air were 29% of the inhaled amount. The tidal breathing method resulted in lung deposition of 20.9 +/- 3.4%, and losses with exhaled air were 77.5 +/-3.5%. Mouth deposition did not differ significantly between methods. Variability in lung deposition was 15.3% for the VHC and 32.0% for the tidal breathing method. In addition to greater lung deposition and reproducibility, the VHC method allows easier calculation of the inhaled dose.

Murine model of pulmonary anthrax: kinetics of dissemination, histopathology, and mouse strain susceptibility

Bioweapons are most often designed for delivery to the lung, although this route is not the usual portal of entry for many of the pathogens in the natural environment. Vaccines and therapeutics that are efficacious for natural routes of infection may not be effective against the pulmonary route. Pulmonary models are needed to investigate the importance of specific bacterial genes in virulence, to identify components of the host immune system that are important in providing innate and acquired protection, and for testing diagnostic and therapeutic strategies. This report describes the characteristics of host and Bacillus anthracis interactions in a murine pulmonary-infection model. The infective dose varied depending on the route and method of inoculation. The germination process in the lung began within 1 h of inoculation into the lung, although growth within the lung was limited. B. anthracis was found in the lung-associated lymph nodes approximately 5 h after infection. Minimal pneumonitis was associated with the lung infection, but significant systemic pathology was noted after dissemination. Infected mice typically succumbed to infection approximately 3 to 4 days after inoculation. The 50% lethal doses differed among inbred strains of mice, but within a given mouse strain, neither the age nor the sex of the mice influenced susceptibility to B. anthracis.

In vitro testing of two formoterol dry powder inhalers at different flow rates

The efficiency of two different dry powder inhaler systems for the application of the beta2-sympathomimetic drug Formoterol in the lungs has been tested in vitro. Particle size distributions for each device have been measured at four different flow rates (28.3, 40, 60, and 80 L/min) using an Andersen-Impactor. Mass median aerodynamic diameters (MMAD) of the dispersed powder and deposition of the drug in the respiratory tract was determined using a semiempirical lung deposition model. The optimum output for both devices determined by in vitro measurements is supposed to be achieved with flow rates of 40-60 L/min. The Oxis Turbuhaler delivers the smaller particles as the Foradil P Aerolizer and, thus, the Formoterol deeper into the lungs, but the high specific airflow resistance will influence the ability of patients with severe asthma and children to use the system.

Inhalation delivery of anticancer agents via HFA-based metered dose inhaler using methotrexate as a model drug

In the present study, the feasibility of delivering anticancer drugs via metered dose inhaler (MDI) was demonstrated using methotrexate (MTX) as a model anticancer drug. MDI formulations of MTX were prepared using hydrofluoroalkane-134a containing 0.67% MTX and 10% ethyl alcohol. The particle size of MTX was reduced by cryo milling with or without a surfactant (Pluronic F77) and the milled drug was employed for MDI formulations, which were subsequently evaluated for their medication delivery, mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD). Further, the efficacy of aerosolized MTX was evaluated by determining the in-vitro cytotoxicity of MTX against HL-60 cells using a six-stage viable impactor and the induction of apoptosis in HL-60 cells by acridine orange staining. Our results indicate that MTX aerosols having an MMAD varying between 2.2 and 3.2 microm (GSD 2.6-3.7) with a respirable fraction varying between 14.2 and 17.1% could be obtained by using MTX, which was cryo milled either alone or in combination with Pluronic F77. Exposure of HL-60 cells plated in third, fourth, fifth, and sixth stages of viable impactor to two actuations of MDI showed a cell kill of greater than 50%. Further, aerosolized MTX was found to induce apoptosis in HL-60 cells, as assessed by the morphological examination of the cells with fluorescent and confocal microscopy. Our results demonstrate that it is possible to deliver cytotoxic concentrations of MTX in an in vitro system simulating the lower respiratory tract (by using a six-stage viable impactor) via MDI and the cytotoxicity of the aerosolized MTX could be further improved by the optimization of the aerodynamic size.