Murine Macrophages Kill the Vegetative Form of Bacillus anthracis

Abstract

Anti-protective antigen antibody was reported to enhance macrophage killing of ingested Bacillus anthracis spores, but it was unclear whether the antibody-mediated macrophage killing mechanism was directed against the spore itself or the vegetative form emerging from the ingested and germinating spore. To address this question, we compared the killing of germination-proficient (gp) and germination-deficient (⌬gerH) Sterne 34F2 strain spores by murine peritoneal macrophages. While macrophages similarly ingested both spores, only gp Sterne was killed at 5 h (0.37 log kill). Pretreatment of macrophages with gamma interferon (IFN-␥) or opsonization with immunoglobulin G (IgG) isolated from a subject immunized with an anthrax vaccine enhanced the killing of Sterne to 0.49 and 0.73 log, respectively, but the combination of IFN-␥ and IgG was no better than either treatment alone. Under no condition was there killing of ⌬gerH spores. To examine the ability of the exosporium to protect spores from macrophages, we compared the macrophage-mediated killing of nonsonicated (exosporium ؉ ) and sonicated (exosporium ؊ ) Sterne 34F2 spores. More sonicated spores than nonsonicated spores were killed at 5 h (0.98 versus 0.37 log kill, respectively). Pretreatment with IFN-␥ increased the sonicated spore killing to 1.39 log. However, the opsonization with IgG was no better than no treatment or pretreatment with IFN-␥. We conclude that macrophages appear unable to kill the spore form of B. anthracis and that the exosporium may play a role in the protection of spores from macrophages.

Treatment of Experimental Anthrax with Recombinant Capsule Depolymerase

“…We report here that treatment targeting B. anthracis bacilli to phagocytes by enzymatically removing the capsule can protect animals from infection, further supporting the role of capsule in evading host innate immunity. Although dormant spores may not be susceptible to phagocytic killing until they germinate (17,20,32), the vegetative form of the organism is susceptible to phagocytic killing, particularly when devoid of capsule (20,28,39,42). As mentioned above, enzyme treatment to remove microbial capsules has been successfully used to treat existing infections with pneumococci, Cryptococcus, and E. coli (2,15,31) in mouse models of infection.…”

The Ger Receptor Family from Sporulating Bacteria

“…Previous reports had suggested that the GerX, GerH, and to a lesser extent the GerS receptors, are important for the establishment of anthrax infection and disease progression (Guidi-Rontani et al, 1999;Ireland and Hanna, 2002b;Kang et al, 2005;. However, recent data shows that as long as one of the genomically encoded receptors (GerH, GerK, GerL, or GerS) is present, B. anthracis spores remain fully virulent in an inhalational anthrax murine model (Carr et al, 2010).…”

The Wound Healing Effect of Hydnocarpi Semen Extract on Ulcer in Diabetic Mice

“…Peritoneal fluid was drawn through the abdominal wall with a 23-gauge needle. Fluid from mice was pooled, washed, total cell counts determined using a hemacytometer, and the remaining fluid was centrifuged at 380×g for 10 min at 4 o C (Kang et al, 2005). Washed cell suspensions were adjusted to 10 6 macrophages per ml in culture medium containing RPMI-1640 with fetal bovine serum (FBS) 10% and 50 μg/ml gentamicin, and incubated in 24-well cell culture plate in 5% CO2 at 37 o C overnight before exposure to HS.…”