Several bacterial species recruit the complement regulators C4b-binding protein, factor H, and vitronectin, resulting in resistance against the bactericidal activity of human serum. It was recently demonstrated that bacteria also bind plasminogen, which is converted to plasmin that degrades C3b and C5. In this study, we found that a series of clinical isolates (n = 58) of the respiratory pathogen Moraxella catarrhalis, which is commonly isolated from preschool children and adults with chronic obstructive pulmonary disease (COPD), significantly binds human plasminogen. Ubiquitous surface protein A2 (UspA2) and hybrid UspA2 (UspA2H) were identified as the plasminogen-binding factors in the outer membrane proteome of Moraxella. Furthermore, expression of a series of truncated recombinant UspA2 and UspA2H proteins followed by a detailed analysis of protein-protein interactions suggested that the N-terminal head domains bound to the kringle domains of plasminogen. The binding affinity constant (KD) values of full-length UspA2(30-539) (amino acids 30 to 539 of UspA2) and full-length UspA2H(50-720) for immobilized plasminogen were 4.8 × 10(-8) M and 3.13 × 10(-8) M, respectively, as measured by biolayer interferometry. Plasminogen bound to intact M. catarrhalis or to recombinant UspA2/UspA2H was readily accessible for a urokinase plasminogen activator that converted the zymogen into active plasmin, as verified by the specific substrate S-2251 and a degradation assay with fibrinogen. Importantly, plasmin bound at the bacterial surface also degraded C3b and C5, which consequently may contribute to reduced bacterial killing. Our findings suggest that binding of plasminogen to M. catarrhalis may lead to increased virulence and, hence, more efficient colonization of the host.

Emphysema is a common feature of chronic obstructive pulmonary disease (COPD). Current diagnostic methods with high specificity for emphysema are computed tomography (CT) and magnetic resonance imaging (MRI) using hyperpolarised gases. CT is relatively expensive and carries a radiation dose. MRI is inaccessible and very expensive. We describe a single-breath technique for measurement of the dimensions of distal airspaces, potentially suitable for diagnosing emphysema. An aerosol containing nanoparticles is inhaled with a vital capacity manoeuvre and the subject holds his breath at maximum inspiration for 10 s. Particle concentration is measured in the inspired gas and in an alveolar sample obtained from the ensuing exhalation. Since nanoparticles are deposited in the lungs purely by diffusion and the time available for diffusion is controlled, the deposited fraction of aerosol (DF) will reflect the diffusion distances in the distal airspaces. We studied 23 normal subjects and 45 patients suffering from a variety of lung diseases and referred for pulmonary function tests. The most common diagnosis was COPD. As a group, the patients showed airflow obstruction. The range of DF found in normal subjects was very narrow. The ADF was lower in the patients than in normal subjects, compatible with increased diffusion distances in distal airspaces. This preliminary study shows promise for the Airspace Dimension Test as a diagnostic test. Further studies are required to elucidate its relation to emphysema.

Emphysema, i.e. breakdown of lung tissue, is a common manifestation of COPD. Emphysema leads to enlargements of the peripheral airspaces that are difficult to observe with conventional spirometry. The deposition probability of inhaled airborne nanoparticles is essentially determined by the dimensions of the peripheral airspaces. This work describes a novel technique, Airspace Dimension Test (ADT), for diagnosis of emphysema with aerosolized nanoparticles. The instrument, shown in the Figure, consists of three main parts: 1) aerosol generation and conditioning, 2) inhalation system and 3) particle detection and analysis. The deposition of nanoparticles in the peripheral lung is measured by comparison of the inhaled and exhaled particle concentrations. A pre-defined breathing pattern was used. ![Figure][1] The instrument was characterized and tested for sensitivity regarding changes in particle size, diffusion time and inter-subject variability on a group of seven young, healthy volunteers. The results were compared with values calculated from an in silico lung deposition model. The deposition fraction increased with increased breath-hold time and decreased particle size as is expected according to diffusion theory. The inter-subject variability was significantly larger than the measurement uncertainty. The measured values were in accordance with theory and could thus be expected to correlate with the dimensions of the peripheral airspaces. [1]: pending:yes

Introduction The Airspace Dimension Test (ADT) is a novel technique to examine the lungs by measurement of deposition of nanoparticles in distal airspaces under controlled conditions (Jakobsson et al., in manuscript). Nanoparticles in the size range <300 nm are known to deposit in the airways almost exclusively by diffusion, a process depending on time and distances. By measuring the deposition of inhaled nano particles during a well-controlled residence time in the lungs of a human subject, information about the average diffusion lengths and thus the state of the lungs can be obtained. The primary aim of the technique is to be able to detect pulmonary emphysema at an early stage, a much demanded technology for battling the rising global threat of chronic obstructive pulmonary disease (COPD).