Sequential role of MyD88 and CARD9 in neutrophil recruitment during respiratory fungal infection

Ref ID: 19517

Author:

A Jhingran1*, S Kasahara1, DK Kumasaka2, SE Knoblaugh3, TM Hohl1

Author address:

1Medicine, Memorial Sloan-Kettering Cancer Center, New York, US
2Human Biology, Fred Hutchinson Cancer Research Center, Seattle, US
3Comparative Medicine Shared Resources, Fred Hutchinson Cancer Research Center, Seattle, US

Full conference title:

6th Advances Against Aspergillosis 2014

Abstract:

Purpose:
Aspergillus fumigatus (Af), the most common agent of invasive aspergillosis (IA), is an environmental
fungus that forms airborne conidia. Humans inhale Af conidia daily and asymptomatic clearance
depends on the functional and numeric integrity of the respiratory innate immune system, with a
predominate role for neutrophils. In neutropenic patients, conidial germination into tissue-invasive
hyphae (filaments) is the central step in IA pathogenesis.
Although the Toll-like receptor adaptor protein MyD88 and the C-type lectin receptor signal
transducer CARD9 are implicated in conidial recognition and in mounting inflammatory response
following conidial challenge, their role in controlling neutrophil function during respiratory fungal
infection remains poorly understood. We have examined the coordination of MyD88 and CARD9 in
building a protective immune response against inhaled conidia in the lung.
Method:
We infected mice by intratracheal instillation of Af conidia. We assessed lung inflammation by
histology, and measured the levels of cytokines and chemokines released by in situ hybridization
and enzyme-linked immunosorbent assay. To investigate neutrophils function, we infected mice
with the fluorescent Aspergillus reporter (FLARE) strain that simultaneously report the phagocytic
and conidiacidal activity of leukocytes at a single encounter resolution. Conidial uptake and viability
in neutrophils of the FLARE infected mice were measured by flow cytometry.
Results:
Investigating neutrophil function post-infection, we found that MyD88 deficiency led to enhanced
murine susceptibility to respiratory fungal infection, delayed neutrophil recruitment and reduced
chemokine secretion in the lung of infected mice at 10 h post-infection. Our results further indicate
that MyD88 signalling in radioresistant cells is critical for generating this early neutrophil response.
However, using a fluorescent reporter of fungal viability, we found that MyD88 is dispensable for
neutrophil conidial uptake and killing in the lung.
In contrast, CARD9 signaling controls neutrophil recruitment to the lung at 36 h and 72 h post-infection.
Consistent with biphasic control of neutrophil recruitment by MyD88 and CARD9, we found that
the MyD88 and CARD9 double knockout mice have severely impaired neutrophil recruitment at
both phases of infection, and develop and succumb to IA rapidly following experimental infection.
Conclusion:
In sum, our data demonstrate that MyD88 and CARD9 act in a sequential manner to control neutrophil
recruitment to infected lungs, demonstrating coordinate regulation of neutrophil influx by TLR and
CLR signaling pathways that operate predominately in non-hematopoietic and hematopoietic cells,
respectively.

Abstract Number: 45

Conference Year: 2014

Link to conference website: http://www.AAA2014.org

New link: NULL

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