Protein D expression promotes the adherence and internalization of non-typeable Haemophilus influenzae into human monocytic cells.
Protein D, having a glycerol-3-phosphodiester phosphodiesterase activity, is found at the surface of all Haemophilus influenzae strains and is a possible virulence factor. In the present study, the involvement of protein D in the entry of NTHi into human monocytic cells is reported. Primary monocytes and the monocytic cell lines U-937 and THP-1 were infected with NTHi strain 772 and the mutant 772 Delta hpd 1 (lacking the gene for protein D). NTHi 772 adhered to and entered monocytic cells up to four-fold more efficiently compared to 772 Delta hpd 1. When an Escherichia coli transformant expressing protein D was incubated with monocytic cells, the number of intracellular bacteria increased 1.6-fold compared to protein D-deficient controls. Any correlation between internalization and phosphorylcholine expression was not detected. In conclusion, our data suggest that surface-expressed protein D promotes the adherence of NTHi to human monocytes leading to a higher number of internalized bacteria.
Ahrén
I L
IL
Department of Medical Microbiology, Malmö University Hospital, Lund University, S-205 02 Malmö, Sweden.
Janson
H
H
Forsgren
A
A
Riesbeck
K
K
D001422:Bacterial Adhesion; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006193:Haemophilus influenzae / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D006801:Humans; D007072:Immunoglobulin D; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism* / Q000382:microbiology*; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism; D014169:Transformation, Bacterial; D014407:Tumor Cells, Cultured; D020298:U937 Cells; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D007072:Immunoglobulin D; D008074:Lipoproteins; D010727:Phosphoric Diester Hydrolases; C067989:glpQ protein, Haemophilus influenzae; C038133:glycerophosphodiester phosphodiesterase