Activation of macrophages for destruction of Francisella tularensis: identification of cytokines, effector cells, and effector molecules

Abstract

Francisella tularensis live vaccine strain (LVS) was grown in culture with nonadherent resident, starchelicited, or Proteose Peptone-elicited peritoneal cells. Numbers of bacteria increased 4 logs over the input inoculum in 48 to 72 h. Growth rates were faster in inflammatory cells than in resident cells: generation times for the bacterium were 3 h in inflammatory cells and 6 h in resident macrophages. LVS-infected macrophage cultures treated with lymphokines did not support growth of the bacterium, although lymphokines alone had no inhibitory effects on replication of LVS in culture medium devoid of cells. Removal of gamma interferon (IFN-y) by immunoaffinity precipitation rendered lymphokines ineffective for induction of macrophage anti-LVS activity, and recombinant IFN-y stimulated both resident and inflammatory macrophage populations to inhibit LVS growth in vitro. Inflammatory macrophages were more sensitive to effects of IFN-y: half-maximal activity was achieved at 5 U/ml for inflammatory macrophages and 20 U/mI for resident macrophages. IFN-'y-induced anti-LVS activity correlated with the production of nitrite (NO2-), an oxidative end product of L-arginine-derived nitric oxide (NO). Anti-LVS activity and nitrite production were both completely inhibited by the addition of either the L-arginine analog NG-monomethyl-L-arginine or anti-tumor necrosis factor antibodies to activated macrophage cultures. Thus, macrophages can be activated by IFN-'y to suppress the growth of F. tularensis by generation of toxic levels of NO, and inflammatory macrophages are substantially more sensitive to activation activities of IFN-y for this effector reaction than are more differentiated resident cells.

Francisella tularensis inhibits Toll-like receptor-mediated activation of intracellular signalling and secretion of TNF-alpha and IL-1 from murine macrophages

“…Moreover, the F. tularensis LVS-infected cells were found incapable to respond to BLP or LPS with transcription of TNF-a, IL-1b, or IL-12 mRNA or secretion of TNF-a or IL-1b. In previous studies, the administration of anti-TNF-a antibody was shown to abrogate the host resistance in macrophages to F. tularensis in vitro (Fortier et al, 1992) and in vivo in mice (Sjöstedt et al, 1996). Obviously, the ability of F. tularensis to inhibit cytokine release from macrophages may be one reason why it is such a successful intracellular pathogen.…”

“…Francisella tularensis , the causative agent of tularaemia, is a highly virulent pathogen capable of infecting many mammalian species. Francisella tularensis infects and rapidly multiplies both in phagocytic and non-phagocytic cells (Tärnvik, 1989;Anthony et al ., 1991;Fortier et al ., 1992). The mechanisms behind this successful intracellular parasitism are not understood.…”

Modulation of biogenesis of the Francisella tularensis subsp. novicida-containing phagosome in quiescent human macrophages and its maturation into a phagolysosome upon activation by IFN-γ

“…High systemic levels of IFN-g are produced by mice within a day after primary sub lethal LVS infection, and typically peak within 7 days (Anthony et al, 1989;Leiby et al, 1992;Elkins et al, 1993;2003). The presence of IFN-g during the first 2 h of infection is critical for the host defence against infection (Anthony et al, 1989;1992a;Fortier et al, 1992.;Leiby et al, 1992), and depletion of IFN-g before primary infection renders mice highly susceptible to LVS infection (Anthony et al, 1989;1992a;Fortier et al, 1992). In addition, IFN-g knockout mice are exquisitely susceptible to LVS infection (Leiby et al, 1992;Elkins et al, 1996).…”

Induction of in vivo resistance to Mycobacterium avium infection by intramuscular injection with DNA encoding interleukin‐18

“…The supernatants were then harvested and assayed for NO by the Griess reaction. 30 Brie¯y, culture supernatants (50 ml) were mixed with 100 ml of 1% sulfanilamide (Sigma) and 100 ml of 0 . 1% N-1-naphthylethylenediamine dihydrochloride in 2 .…”