Micropolyspora faeni causes airway inflammation but not hyperresponsiveness in sensitized ponies

Abstract

We assessed the effect of aerosol Micropolyspora faeni challenge in two groups of ponies by measuring lung function, airway reactivity to aerosol histamine, and bronchoalveolar lavage fluid cytology. One group of ponies was sensitized by subcutaneous injection of M. faeni in complete Freund's adjuvant, and the other group served as control. In both groups of ponies, measurements were made at base line and 5 h after aerosol administration of 30 ml of saline or 30 ml of 1% wt/vol particulate M. faeni antigen in saline. Saline challenge had no effect on any of the measured variables. M. faeni challenge had no effect on pulmonary mechanics or gas exchange in the control group but significantly increased respiratory frequency and minute ventilation and decreased arterial CO2 tension in the sensitized ponies. In both groups of ponies, aerosol M. faeni challenge significantly increased total white blood cell count and neutrophil numbers in bronchoalveolar lavage fluid while large mononuclear cell numbers decreased. Airway responsiveness was unaltered by saline or M. faeni challenge in both pony groups. We conclude that aerosol M. faeni challenge induces pulmonary neutrophilia and abnormalities of ventilation but is not accompanied by airway hyperresponsiveness in sensitized ponies.

Clinical signs, evaluation of bronchoalveolar lavage fluid, and assessment of pulmonary function in horses with inflammatory respiratory disease

“…Results of the study also revealed that neutrophilic inflammation of the respiratory tract' s smaller airways may be observed in horses that do not have COPD and that airway inflammation is not necessarily associated with lung dysfunction. These findings are in agreement with studies in which investigators observed an influx of neutrophils in airways of equids exposed to molds 4,37,45 ; however, only equids with COPD had changes in lung function. We speculate that when the inflammatory process is sufficient in duration or severity, changes in morphologic characteristics of the airways will develop, leading to impairment of lung function, such as has been proposed in humans with asthma.…”

Evaluation of local endobronchial antigen challenges in the investigation of equine chronic obstructive pulmonary disease

“…The extent of pulmonary neutrophilia observed in these previous studies varied, being either diffuse or localised to the lavaged segment. In contrast to these findings, Derksen et al (1987) demonstrated that three repeated BALs, performed in different segments within a 29-h period, did not significantly affect BALF cytology of 3 ponies.…”

Idiopathic Chronic Eosinophilic Pneumonia in 7 Horses

“…Peripheral eosinophilia and eosinophilic respiratory secretions associated with positive intradermal and serum precipitin tests to Saccharopolyspora rectivirgula (formerly Micropolyspora faeni ) have been reported 13 . However, experimental aerosol challenge of sensitized ponies with S. rectivirgula induced increased neutrophils but not eosinophils in respiratory secretions, and no clinically relevant changes in peripheral eosinophil count, 14 perhaps supporting the role of S. rectivirgula in recurrent airway obstruction but not in eosinophilic pulmonary disease. Other allergens, however, could possibly contribute to the development of eosinophilic disease in horses.…”