title: Activation of brain endothelium by pneumococcal neuraminidase NanA promotes bacterial internalization.
abstract: Streptococcus pneumoniae (SPN), the leading cause of meningitis in children and adults worldwide, is associated with an overwhelming host inflammatory response and subsequent brain injury. Here we examine the global response of the blood-brain barrier to SPN infection and the role of neuraminidase A (NanA), an SPN surface anchored protein recently described to promote central nervous system tropism. Microarray analysis of human brain microvascular endothelial cells (hBMEC) during infection with SPN or an isogenic NanA-deficient (ΔnanA) mutant revealed differentially activated genes, including neutrophil chemoattractants IL-8, CXCL-1, CXCL-2. Studies using bacterial mutants, purified recombinant NanA proteins and in vivo neutrophil chemotaxis assays indicated that pneumococcal NanA is necessary and sufficient to activate host chemokine expression and neutrophil recruitment during infection. Chemokine induction was mapped to the NanA N-terminal lectin-binding domain with a limited contribution of the sialidase catalytic activity, and was not dependent on the invasive capability of the organism. Furthermore, pretreatment of hBMEC with recombinant NanA protein significantly increased bacterial invasion, suggesting that NanA-mediated activation of hBMEC is a prerequisite for efficient SPN invasion. These findings were corroborated in an acute murine infection model where we observed less inflammatory infiltrate and decreased chemokine expression following infection with the ΔnanA mutant.
authors.affiliation: Department of Biology, Center for Microbial Sciences, San Diego State University, San Diego, CA, USA.
authors.forename: Anirban
authors.initials: A
authors.lastname: Banerjee
authors.forename: Nina M
authors.initials: NM
authors.lastname: Van Sorge
authors.forename: Tamsin R
authors.initials: TR
authors.lastname: Sheen
authors.forename: Satoshi
authors.initials: S
authors.lastname: Uchiyama
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Mitchell
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Doran
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000276:immunology / Q000378:metabolism*; D001921:Brain / Q000098:blood supply* / Q000382:microbiology; D054418:Chemokine CCL20 / Q000378:metabolism; D054360:Chemokine CXCL1 / Q000378:metabolism; D054426:Chemokine CXCL2 / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism* / Q000382:microbiology; D004730:Endothelium, Vascular / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D037102:Lectins; D008586:Meningitis, Pneumococcal / Q000276:immunology / Q000382:microbiology*; D051379:Mice; D009154:Mutation; D009439:Neuraminidase / Q000378:metabolism*; D020556:Neutrophil Infiltration; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D015398:Signal Transduction; D013296:Streptococcus pneumoniae / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D054418:Chemokine CCL20; D054360:Chemokine CXCL1; D054426:Chemokine CXCL2; D016209:Interleukin-8; D037102:Lectins; D009439:Neuraminidase