Chlamydia pneumoniae hides inside apoptotic neutrophils to silently infect and propagate in macrophages.
BACKGROUND
Intracellular pathogens have developed elaborate strategies for silent infection of preferred host cells. Chlamydia pneumoniae is a common pathogen in acute infections of the respiratory tract (e.g. pneumonia) and associated with chronic lung sequelae in adults and children. Within the lung, alveolar macrophages and polymorph nuclear neutrophils (PMN) are the first line of defense against bacteria, but also preferred host phagocytes of chlamydiae.


RESULTS
We could show that C. pneumoniae easily infect and hide inside neutrophil granulocytes until these cells become apoptotic and are subsequently taken up by macrophages. C. pneumoniae infection of macrophages via apoptotic PMN results in enhanced replicative activity of chlamydiae when compared to direct infection of macrophages, which results in persistence of the pathogen. Inhibition of the apoptotic recognition of C. pneumoniae infected PMN using PS- masking Annexin A5 significantly lowered the transmission of chlamydial infection to macrophages. Transfer of apoptotic C. pneumoniae infected PMN to macrophages resulted in an increased TGF-ss production, whereas direct infection of macrophages with chlamydiae was characterized by an enhanced TNF-alpha response.


CONCLUSIONS
Taken together, our data suggest that C. pneumoniae uses neutrophil granulocytes to be silently taken up by long-lived macrophages, which allows for efficient propagation and immune protection within the human host.
Rupp
Jan
J
Institute of Medical Microbiology and Hygiene, University of Luebeck, Luebeck, Germany. jan.rupp@uk-sh.de
Pfleiderer
Lisa
L
Jugert
Christiane
C
Moeller
Sonja
S
Klinger
Matthias
M
Dalhoff
Klaus
K
Solbach
Werner
W
Stenger
Steffen
S
Laskay
Tamas
T
van Zandbergen
Ger
G
D017209:Apoptosis; D002460:Cell Line / Q000382:microbiology; D002469:Cell Separation; D016993:Chlamydophila pneumoniae / Q000472:pathogenicity* / Q000502:physiology*; D016207:Cytokines / Q000096:biosynthesis; D005434:Flow Cytometry; D006098:Granulocytes / Q000382:microbiology; D006801:Humans; D008264:Macrophages / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology*; D008954:Models, Biological; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016207:Cytokines