Neutrophil-Specific Knockdown of β2 Integrins Impairs Antifungal Effector Functions and Aggravates the Course of Invasive Pulmonal Aspergillosis

Maximilian Haist; Frederic Ries; Matthias Gunzer; Monika Bednarczyk; Ekkehard Siegel; Michael Kuske; Stephan Grabbe; Markus Radsak; Matthias Bros; Daniel Teschner

doi:10.3389/fimmu.2022.823121

Neutrophil-Specific Knockdown of β2 Integrins Impairs Antifungal Effector Functions and Aggravates the Course of Invasive Pulmonal Aspergillosis

Front Immunol. 2022 Jun 6:13:823121. doi: 10.3389/fimmu.2022.823121. eCollection 2022.

Authors

Affiliations

¹ Department of Dermatology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
² Department of Hematology, Medical Oncology and Pneumology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
³ Institute for Experimental Immunology and Imaging, University Hospital, University Duisburg-Essen, Essen, Germany.
⁴ Leibniz-Institut für Analytische Wissenschaften ISAS -e.V, Dortmund, Germany.
⁵ Institute for Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
⁶ Department of Internal Medicine II, University Hospital Würzburg, Würzburg, Germany.

Abstract

β2-integrins are heterodimeric surface receptors that are expressed specifically by leukocytes and consist of a variable α (CD11a-d) and a common β-subunit (CD18). Functional impairment of CD18, which causes leukocyte adhesion deficiency type-1 results in an immunocompromised state characterized by severe infections, such as invasive pulmonary aspergillosis (IPA). The underlying immune defects have largely been attributed to an impaired migratory and phagocytic activity of polymorphonuclear granulocytes (PMN). However, the exact contribution of β2-integrins for PMN functions in-vivo has not been elucidated yet, since the mouse models available so far display a constitutive CD18 knockout (CD18^-/- or CD18^hypo). To determine the PMN-specific role of β2-integrins for innate effector functions and pathogen control, we generated a mouse line with a Ly6G-specific knockdown of the common β-subunit (CD18^Ly6G cKO). We characterized CD18^Ly6G cKO mice in-vitro to confirm the PMN-specific knockdown of β2-integrins. Next, we investigated the clinical course of IPA in A. fumigatus infected CD18^Ly6G cKO mice with regard to the fungal burden, pulmonary inflammation and PMN response towards A. fumigatus. Our results revealed that the β2-integrin knockdown was restricted to PMN and that CD18^Ly6G cKO mice showed an aggravated course of IPA. In accordance, we observed a higher fungal burden and lower levels of proinflammatory innate cytokines, such as TNF-α, in lungs of IPA-infected CD18^Ly6G cKO mice. Bronchoalveolar lavage revealed higher levels of CXCL1, a stronger PMN-infiltration, but concomitantly elevated apoptosis of PMN in lungs of CD18^Ly6G cKO mice. Ex-vivo analysis further unveiled a strong impairment of PMN effector function, as reflected by an attenuated phagocytic activity, and a diminished generation of reactive oxygen species (ROS) and neutrophil-extracellular traps (NET) in CD18-deficient PMN. Overall, our study demonstrates that β2-integrins are required specifically for PMN effector functions and contribute to the clearance of A. fumigatus by infiltrating PMN, and the establishment of an inflammatory microenvironment in infected lungs.

Keywords: Aspergillus fumigatus; CD11b; CD18; complement receptor 3; phagocytosis; pneumonia; polymorphonuclear neutrophils; β2 integrins.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
CD18 Antigens*
Invasive Pulmonary Aspergillosis*
Lung / microbiology
Mice
Neutrophils

Substances

CD18 Antigens