Phagocytosis of Aspergillus fumigatus conidia by primary nasal epithelial cells in vitro

doi:10.1186/1471-2180-8-97

BMC Microbiology

Volume 8

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Botterel F
Gross K
Ibrahim-Granet O
Khoufache K
Escabasse V
Coste A
Cordonnier C
Escudier E
Bretagne S

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Gross K
Ibrahim-Granet O
Khoufache K
Escabasse V
Coste A
Cordonnier C
Escudier E
Bretagne S
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Research article

Phagocytosis of Aspergillus fumigatus conidia by primary nasal epithelial cells in vitro

Françoise Botterel¹^,7 , Karine Gross¹^,7 , Oumaïma Ibrahim-Granet² , Khaled Khoufache¹^,7 , Virginie Escabasse³^,4 , André Coste³^,4 , Catherine Cordonnier⁵ , Estelle Escudier³^,6 and Stéphane Bretagne¹^,7

¹Université Paris 12, Créteil, France

²Unité des Aspergillus, Institut Pasteur, 75724, Paris, France

³Inserm U 492, and Université Paris 12, Créteil, France

⁴Service d'ORL et de Chirurgie Cervico-Faciale, Hôpital Intercommunal de Créteil, France

⁵Service d'Hématologie Clinique, Hôpital Henri Mondor (AP-HP), Créteil, France

⁶Département de Génétique, Cytogénétique et Embryologie, Groupe Hospitalier Pitié-Salpêtrière (AP-HP), Paris, France

⁷Laboratoire de Parasitologie-Mycologie, Hôpital Henri Mondor, 51 avenue du Général De Lattre de Tassigny, 94010 Créteil, France

author email corresponding author email

BMC Microbiology 2008, 8:97doi:10.1186/1471-2180-8-97


Published:	18 June 2008

Abstract

Background

Invasive aspergillosis, which is mainly caused by the fungus Aspergillus fumigatus, is an increasing problem in immunocompromised patients. Infection occurs by inhalation of airborne conidia, which are first encountered by airway epithelial cells. Internalization of these conidia into the epithelial cells could serve as a portal of entry for this pathogenic fungus.

Results

We used an in vitro model of primary cultures of human nasal epithelial cells (HNEC) at an air-liquid interface. A. fumigatus conidia were compared to Penicillium chrysogenum conidia, a mould that is rarely responsible for invasive disease. Confocal microscopy, transmission electron microscopy, and anti-LAMP1 antibody labeling studies showed that conidia of both species were phagocytosed and trafficked into a late endosomal-lysosomal compartment as early as 4 h post-infection. In double immunolabeling experiments, the mean percentage of A. fumigatus conidia undergoing phagocytosis 4 h post-infection was 21.8 ± 4.5%. Using combined staining with a fluorescence brightener and propidium iodide, the mean rate of phagocytosis was 18.7 ± 9.3% and the killing rate 16.7 ± 7.5% for A. fumigatus after 8 h. The phagocytosis rate did not differ between the two fungal species for a given primary culture. No germination of the conidia was observed until 20 h of observation.

Conclusion

HNEC can phagocytose fungal conidia but killing of phagocytosed conidia is low, although the spores do not germinate. This phagocytosis does not seem to be specific to A. fumigatus. Other immune cells or mechanisms are required to kill A. fumigatus conidia and to avoid further invasion.