L. pneumophila inhibits translation of host-defense genes in alveolar macrophages during lung infection.
KLATT A. 1, MILEK M. 2, KIRCHNER M. 3, RÖWEKAMP I. 1, FIOCCA VERNENGO F. 1, CAESAR S. 1, MERTINS P. 3, BEULE D. 2, OPITZ B. 1
1 Department of Infectious Diseases, Respiratory Medicine and Critical Care, Charité – Universitätsmedizin Berlin, Berlin, Germany; 2 Core Unit Bioinformatics, Berlin Institute of Health, Charité – Universitätsmedizin Berlin, Berlin, Germany; 3 Max Delbrück Center for Molecular Medicine in the Helmholtz Society and Berlin Institute of Health, Berlin, Germany; 4 Deutsches Rheuma-Forschungszentrum Berlin (DRFZ), a Leibniz Institute, Berlin, Germany
Various clinically important pathogens including Legionella pneumophila use tissue-resident macrophages as their replication niche. By using bone marrow macrophages (BMMs) as cell culture models, previous studies have shown that L. pneumophila inhibits translation of a large variety of host proteins as a virulence strategy. In contrast, little is known about how tissue-resident alveolar macrophages (AMs), the primary host cells of Legionella, react in response to infection.
Mice were intranasally infected with GFP-expressing virulent (JR32 ΔflaA) or avirulent (JR32 ΔdotA) strains of L. pneumophila to subsequently isolate infected and non-infected AMs by FACS sorting. We used bulk RNA sequencing, proteomics and single cell RNA sequencing to characterize the responses of AM's to the infection.
Expression of inflammatory- and metabolism-associated genes and proteins differs considerably between ΔflaA- and ΔdotA-infected and non-infected AMs. In line with observations made in BMMs, we found that in virulently infected AMs various genes (e.g. Il1b or Ccl9) showed increased mRNA but not protein levels, while other molecules, e.g. Il1a, A20 and Atf3 were upregulated on both levels. By defining classes of proteins based on their regulation on mRNA and protein level, we further identified candidate molecules that might play critical roles in regulating innate antibacterial defense during pulmonary infection with L. pneumophila.
Ongoing studies aim to further explore the role of candidate molecules in AM´s response to L. pneumophila during lung infection.