Adenosine-dependent airway inflammation and hyperresponsiveness in partially adenosine deaminase-deficient mice.

Adenosine is a signaling nucleoside that is elevated in the lungs of asthmatics. We have engineered a mouse model that has elevated levels of adenosine as a result of the partial expression of the enzyme that metabolizes adenosine, adenosine deaminase (ADA). Mice with lowered levels of ADA enzymatic activity were generated by the ectopic expression of an ADA minigene in the gastrointestinal tract of otherwise ADA-deficient mice. These mice developed progressive lung inflammation and damage and died at 4-5 mo of age from respiratory distress. Associated with this phenotype was a progressive increase in lung adenosine levels. Examination of airway physiology at 6 wk of age revealed alterations in airway hyperresponsiveness. This was reversed following the lowering of adenosine levels using ADA enzyme therapy and also through the use of the adenosine receptor antagonist theophylline, implicating both the nucleoside and its receptors in airway physiological alterations. All four adenosine receptors were expressed in the lungs of both control and partially ADA-deficient mice. However, transcript levels for the A(1), A(2B), and A(3) adenosine receptors were significantly elevated in partially ADA-deficient lungs. There was a significant increase in alveolar macrophages, and monocyte chemoattractant protein-3 was found to be elevated in the bronchial epithelium of these mice, which may have important implications in the regulation of pulmonary inflammation and airway hyperresponsiveness. Collectively, these findings suggest that elevations in adenosine can directly impact lung inflammation and physiology.

Nose-only versus whole-body aerosol exposure for induction of upper respiratory infections of laboratory mice.

The effectiveness of two aerosol delivery systems, nose-only and whole-body, were compared using Swiss-Webster mice and two pathogens, Klebsiella pneumoniae and Venezuelan equine encephalitis (VEE) virus. With K. pneumoniae the median lethal dose (LD50) and the mean time to death correlated with the inhaled dose. An LD50 value of 335 colony forming units (cfu) for nose-only exposure was significantly less than the LD50 value of 3741 cfu obtained for whole-body exposure. The LD50 values obtained with VEE virus for nose-only exposure [8 plaque forming units (pfu)] and whole-body exposure (11 pfu) were similar to each other. Following a 10-min nose-only exposure, concentrations of K. pneumoniae approximating 10(4)/g were present after 24 hr in the upper respiratory tract (URT) and lungs. The numbers of bacteria reached a peak at 72 hr, when resolution of the infection began. Detectable levels of bacteria in the blood and tissues were delayed in mice given whole-body exposure, plus there was a decreased concentration of bacteria per gram of tissue. Major pathological lesions induced by K. pneumoniae were mild suppurative rhinitis and minimal suppurative bronchopneumonia. Viremia was greatest at 96 hr following aerosol exposure to VEE. Virus concentrations in the URT, lungs, cerebrum, spleen and mesenteric lymph nodes reached maximum titers earlier for mice exposed by nose-only than for mice exposed to whole-body aerosols.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response of guinea pigs experimentally infected with aerosols of Legionella pneumophila.

Experiments were carried out to determine the infectivity, clinical course of disease, and lethality of aerosols of Legionella pneumophila for guinea pigs. The median infectious dose was less than 129 organisms; the 50% lethal dose was 1.4 x 10(5) organisms. In addition, the intraperitoneal 50% lethal dose was 3.0 x 10(6) cells, a value indicating that the organisms were less virulent by the intraperitoneal route than by aerosol. Nonfatal disease always included fever and weight loss. These signs were accompanied by sporadic bacteremia and dyspnea. Leukocyte counts were uninformative. In general, the severity of fever and extent of serologic (microagglutination titer) response were dose-related. The guinea pig may be used as a model for Legionnaires' disease, but the only dependable clinical criteria of infection after airborne challenge are weight loss, fever, and seroconversion.

Protection against Klebsiella pneumoniae respiratory tract infection of mice and squirrel monkeys given kanamycin by aerosol and injection.

The methods of aerosol administration of kanamycin and IM injection of the antibiotic were compared for their protection of mice and squirrel monkeys against Klebsiella pneumoniae respiratory tract infection. Mice exposed to LD90 of K pneumoniae at 0.5, 4, 24, 48 and 72 hours after they were treated with aerosol of kanamycin (27 mg/kg of body weight) were significantly better protected at all exposure times than were mice given the antibiotic (450 mg/kg) by IM injection. Squirrel monkeys given the aerosol at dose level of 11.25 mg/kg were completely protected against K pneumoniae exposure at 6 and 24 hours, whereas only one of eight monkeys treated with the same dose given IM survived the exposure at 6 hours and none survived at 24 hours. Antibiotic clearance curves indicated that kanamycin remained in the lungs at higher concentrations and for longer periods after aerosol treatment than after IM treatment.

Aerosol therapy of influenza infections of mice and primates with rimantadine, ribavirin, and related compounds.

Ribavirin administered as small-article aerosols had significant therapeutic effect in the treatment of viral respiratory infections induced by influenza virus. The preliminary experiment using ribavirin to treat influenza infection in the squirrel monkey is encouraging. We expect to extend these experiments by initiating therapy at a later time to investigate the potential value of ribavirin in a clinical situation. Several derivatives of ribavirin are effective antiviral compounds. The tri-O-acetyl derivative appears to offer a potential advantage over ribavirin, although this cannot be stated with certainty since the data were obtained from separate experiments. Radiolabeling has been used as a means of measuring tissue concentration and clearance rates of various drugs. It is hoped that the use of labeled ribavirin and the tri-O-acetyl derivative will assist us in determining whether a depot of antiviral drug is created in pulmonary tissues after administration as a small-particle aerosol. These experiments are now in progress.

Continuous aerosol therapy system using a modified Collison nebulizer.

A Collison nebulizer was incorporated into an exposure system for administering antiviral compounds as continuous aerosols to mice infected with influenza virus. The nebulizer was modified to control aerosol output by varying the liquid feed rate. A multiple regression equation was developed from data obtained with uranine dye to define the aerosol concentration of the dye in the system as a function of the concentration of the dye in the spray fluid and the rate at which it was aerosolized. The rate of change of the concentration of the test solution due to evaporative losses was also ascertained for a 1-ml/min feed rate over a 23.5-h period of operation. Procedures are outlined for using these relationships to determine the concentration of a given drug that will result in a given dose. Performance data for the drug ribavirin are presented.

Aerosol evaluations of the DeVilbiss No. 40 and Vaponefrin nebulizers.

De Vilbiss no. 40 and Vaponefrin standard nebulizers produced aerosols of small particles suitable for deep pulmonary vaccination and therapy of respiratory infections in man and animals.

Modified spinning top homogeneous spray apparatus for use in experimental respiratory disease studies.

The May spinning top generator was adapted to a modified Henderson tube for producing large aerosol particles (>4 mum) to obtain almost exclusive upper respiratory tract deposition of infectious aerosols in exposed mice. The system was installed in a biological safety cabinet to permit experimentation with pathogens. A novel mechanism utilizing parts from a machinists micrometer and the mechanical stage from a light microscope was developed for the spinning top generator as a means for precisely positioning the liquid feed needle. Aerosol light-scatter properties were continuously analyzed to provide relative measures of particle size distribution and aerosol concentration. When mice were exposed to influenza virus aerosols in which none of the virus was contained in particles with aerodynamic diameters <4 mum, essentially all of the virus was deposited in the upper respiratory tract tissues.