Germination of Aspergillus fumigatus inside avian respiratory macrophages is associated with cytotoxicity
1 The Department of Pathology, Bacteriology and Avian diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium
2 The Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, B-9000, Ghent, Belgium
3 The Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820, Merelbeke, Belgium
Veterinary Research 2012, 43:32 doi:10.1186/1297-9716-43-32Published: 19 April 2012
Although aspergillosis is one of the most common diseases in captive birds, the pathogenesis of avian aspergillosis is poorly known. We studied the role of avian respiratory macrophages as a first line of defense against avian aspergillosis. The phagocytic and killing capacities of avian respiratory macrophages were evaluated using pigeon respiratory macrophages that were inoculated with Aspergillus fumigatus conidia. On average, 25% of macrophage-associated conidia were phagocytosed after one hour. Sixteen percents of these cell-associated conidia were killed after 4 h and conidial germination was inhibited in more than 95% of the conidia. A. fumigatus conidia were shown to be cytotoxic to the macrophages. Intracellularly germinating conidia were located free in the cytoplasm of necrotic cells, as shown using transmission electron microscopy. These results suggest that avian respiratory macrophages may prevent early establishment of infection, unless the number of A. fumigatus conidia exceeds the macrophage killing capacity, leading to intracellular germination and colonization of the respiratory tract.