In vivo bioluminescence imaging and histopathopathologic analysis reveal distinct roles for resident and recruited immune effector cells in defense against invasive aspergillosis.
BACKGROUND
Invasive aspergillosis (IA) is a major cause of infectious morbidity and mortality in immune compromised patients. Studies on the pathogenesis of IA have been limited by the difficulty to monitor disease progression in real-time. For real-time monitoring of the infection, we recently engineered a bioluminescent A. fumigatus strain.


RESULTS
In this study, we demonstrate that bioluminescence imaging can track the progression of IA at different anatomic locations in a murine model of disease that recapitulates the natural route of infection. To define the temporal and functional requirements of distinct innate immune cellular subsets in host defense against respiratory A. fumigatus infection, we examined the development and progression of IA using bioluminescence imaging and histopathologic analysis in mice with four different types of pharmacologic or numeric defects in innate immune function that target resident and recruited phagocyte subsets. While bioluminescence imaging can track the progression and location of invasive disease in vivo, signals can be attenuated by severe inflammation and associated tissue hypoxia. However, especially under non-inflammatory conditions, such as cyclophosphamide treatment, an increasing bioluminescence signal reflects the increasing biomass of alive fungal cells.


CONCLUSIONS
Imaging studies allowed an in vivo correlation between the onset, peak, and kinetics of hyphal tissue invasion from the lung under conditions of functional or numeric inactivation of phagocytes and sheds light on the germination speed of conidia under the different immunosuppression regimens. Conditions of high inflammation -either mediated by neutrophil influx under corticosteroid treatment or by monocytes recruited during antibody-mediated depletion of neutrophils- were associated with rapid conidial germination and caused an early rise in bioluminescence post-infection. In contrast, 80% alveolar macrophage depletion failed to trigger a bioluminescent signal, consistent with the notion that neutrophil recruitment is essential for early host defense, while alveolar macrophage depletion can be functionally compensated.
Ibrahim-Granet
Oumaïma
O
Unité de Recherche Cytokines & Inflammation, Institut Pasteur Paris France. oumaima.granet@pasteur.fr
Jouvion
Grégory
G
Hohl
Tobias M
TM
Droin-Bergère
Sabrina
S
Philippart
François
F
Kim
Oh Yoen
OY
Adib-Conquy
Minou
M
Schwendener
Reto
R
Cavaillon
Jean-Marc
JM
Brock
Matthias
M
D000818:Animals; D001232:Aspergillus fumigatus / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D004002:Clodronic Acid / Q000494:pharmacology / Q000627:therapeutic use; D003520:Cyclophosphamide / Q000494:pharmacology; D004271:DNA, Fungal / Q000737:chemistry; D004195:Disease Models, Animal; D018450:Disease Progression; D006651:Histocytochemistry; D007165:Immunosuppression Therapy; D055744:Invasive Pulmonary Aspergillosis / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D008163:Luminescent Measurements / Q000379:methods; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics; D008168:Lung / Q000166:cytology / Q000382:microbiology; D016676:Macrophages, Alveolar / Q000276:immunology*; D051379:Mice; D009000:Monocytes / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D030781:Organisms, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051598:Whole Body Imaging / Q000379:methods
D004271:DNA, Fungal; D008164:Luminescent Proteins; D004002:Clodronic Acid; D003520:Cyclophosphamide