title: Contribution of lethal toxin and edema toxin to the pathogenesis of anthrax meningitis.
abstract: Bacillus anthracis is a Gram-positive spore-forming bacterium that causes anthrax disease in humans and animals. Systemic infection is characterized by septicemia, toxemia, and meningitis, the main neurological complication associated with high mortality. We have shown previously that B. anthracis Sterne is capable of blood-brain barrier (BBB) penetration, establishing the classic signs of meningitis, and that infection is dependent on the expression of both major anthrax toxins, lethal toxin (LT) and edema toxin (ET). Here we further investigate the contribution of the individual toxins to BBB disruption using isogenic toxin mutants deficient in lethal factor, ΔLF, and edema factor, ΔEF. Acute infection with B. anthracis Sterne and the ΔLF mutant resulted in disruption of human brain microvascular endothelial cell (hBMEC) monolayer integrity and tight junction protein zona occludens-1, while the result for cells infected with the ΔEF mutant was similar to that for the noninfected control. A significant decrease in bacterial invasion of BBB endothelium in vitro was observed during infection with the ΔLF strain, suggesting a prominent role for LT in promoting BBB interaction. Further, treatment of hBMECs with purified LT or chemicals that mimic LT action on host signaling pathways rescued the hypoinvasive phenotype of the ΔLF mutant and resulted in increased bacterial uptake. We also observed that toxin expression reduced bacterial intracellular survival by inducing the bulk degradative autophagy pathway in host cells. Finally, in a murine model of anthrax meningitis, mice infected with the ΔLF mutant exhibited no mortality, brain bacterial load, or evidence of meningitis compared to mice infected with the parental or ΔEF strains.
authors.affiliation: Department of Biology and Center for Microbial Sciences, San Diego State University, 5500 Campanile Dr, San Diego, California 92182-4614, USA.
authors.forename: Celia M
authors.initials: CM
authors.lastname: Ebrahimi
authors.forename: Tamsin R
authors.initials: TR
authors.lastname: Sheen
authors.forename: Christian W
authors.initials: CW
authors.lastname: Renken
authors.forename: Roberta A
authors.initials: RA
authors.lastname: Gottlieb
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Doran
mesh_terms: D000818:Animals; D000881:Anthrax / Q000382:microbiology* / Q000401:mortality / Q000473:pathology; D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D001343:Autophagy; D001408:Bacillus anthracis / Q000235:genetics / Q000472:pathogenicity*; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D001812:Blood-Brain Barrier / Q000382:microbiology* / Q000473:pathology; D001921:Brain / Q000098:blood supply / Q000473:pathology; D042783:Endothelial Cells / Q000473:pathology; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D016920:Meningitis, Bacterial / Q000382:microbiology* / Q000401:mortality / Q000473:pathology; D051379:Mice; D055806:Microvessels / Q000473:pathology; D009154:Mutation; D010750:Phosphoproteins / Q000378:metabolism; D019108:Tight Junctions / Q000648:ultrastructure; D062826:Zonula Occludens-1 Protein
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D008565:Membrane Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; C030325:anthrax toxin