In vitro investigation of host resistance to Toxoplasma gondii infection in microglia of BALB/c and CBA/Ca mice.
Toxoplasmic encephalitis (TE) is a life-threatening disease of immunocompromised individuals and has increased in prevalence as a consequence of AIDS. TE has been modeled in inbred mice, with CBA/Ca mice being susceptible and BALB/c mice resistant to the development of TE. To better understand the innate mechanisms in the brain that play a role in resistance to TE, nitric oxide (NO)-dependent and NO-independent mechanisms were examined in microglia from BALB/c and CBA/Ca mice and correlated with the ability of these cells to inhibit Toxoplasma gondii replication. These parameters were measured 48 h after stimulation with lipopolysaccharide (LPS) gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), or combinations of these inducers in T. gondii-infected microglia isolated from newborn mice. CBA/Ca microglia consistently produced less NO than did BALB/c microglia after stimulation with LPS or with IFN-gamma plus TNF-alpha, and they inhibited T. gondii replication significantly less than did BALB/c microglia. Cells of both strains treated with IFN-gamma alone significantly inhibited uracil incorporation by T. gondii, and N(G)-monomethyl-L-arginine (NMMA) treatment did not reverse this effect. In cells treated with IFN-gamma in combination with other inducers, NMMA treatment resulted in only partial recovery of T. gondii replication. This IFN-gamma-dependent inhibition of replication was not due to generation of reactive oxygen species or to increased tryptophan degradation. These data suggest that NO production and an IFN-gamma-dependent mechanism contribute to the inhibition of T. gondii replication after in vitro stimulation with IFN-gamma plus TNF-alpha or with LPS. Differences in NO production but not in IFN-gamma-dependent inhibition of T. gondii replication were observed between CBA/Ca and BALB/c microglia.
Freund
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YR
Immunology Program, Pharmaceutical Discovery Division, SRI International, Menlo Park, California 94025, USA. yvonne.freund@sri.com
Zaveri
N T
NT
Javitz
H S
HS
D000818:Animals; D002478:Cells, Cultured; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D017628:Microglia / Q000469:parasitology*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D013045:Species Specificity; D014122:Toxoplasma / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse