The pathologic features of cerebral infection strongly suggest that besides hematogenous spread bacteria might also spread via a neural route. a protecting part in neuroinvasion; inducible nitric oxide synthase (iNOS) accounts only partially for the safety as shown by a comparison of the susceptibilities of IFN-γ receptor (IFN-γR)-deficient iNOS-deficient and wild-type mice to snout illness with is definitely a gram-positive facultative intracellular bacterium which can cause severe infections in the nervous system of humans as well as domestic animals. can cause meningitis in immunocompromised humans but after the first description by Eck (13) a number of cases of mind stem encephalitis (rhombencephalitis) also were reported. illness of trigeminal ganglia (TG) and nerves MK-2894 and swelling in the brain stem that is most severe on the side of the affected trigeminal nerve in sheep have been explained (10). The pathways by which reaches the brain stem to cause rhombencephalitis have not been clarified. In general hematogenous spread of to the nervous system via crossing of the mucosal barrier Cd8a in the intestines is the approved theory. The opinion that can pass through the blood-brain barrier is definitely supported by experimental studies in vivo (7) and by the ability of to penetrate human being endothelial cells in vitro (17 37 However the asymmetric bacterial weight and pathology in the TG of infected sheep goats rabbits and mice have indicated the bacteria may spread along cranial nerves (5). Moreover human patients have shown signs of progressive unilateral cranial nerve palsies followed by swelling and the appearance of abscesses in the brain stem (2 34 The hypothesis of a neural route of neuroinvasion was supported from the ultrastructural getting of in myelinated axons in naturally infected sheep (26) and by our earlier observations of infections of neurons of dorsal root ganglia (DRG) in vitro (11). We statement here that spreads along the trigeminal nerve to the brain stem in genetically immunodeficient mice. We hypothesized the immune responses controlling the neuronal dissemination of listerial illness might be qualitatively different from those active in the control of hematogenous illness with the bacteria. By using different knockout mice we found that both innate and T- and/or B-cell-dependent immune mechanisms control the neural spread of bacteria. Innate gamma interferon (IFN-γ) apparently released by NK cells but not NK-cell cytotoxicity inhibited the spread of bacteria along this cranial nerve route. Inducible nitric MK-2894 oxide synthase (iNOS) activity accounted only partially for the IFN-γ-dependent protection. A direct bacteriostatic effect of IFN-γ-triggered neural tissue within the protecting effect of the cytokine is definitely suggested. MATERIALS AND METHODS Mice. C57BL/6 mice were bred under specific-pathogen-free conditions. Mutant mouse strains without MK-2894 recombination activating gene 1 (and IFN-γR or and perforin were generated in our laboratory as recently explained (28). wild-type (WT) strain EGD (BUG600 serotype 1/2a) and EGD Δ(having a defective lecithinase) were grown in mind heart infusion (BHI) broth and on BHI agar (both from Difco Laboratories Detroit Mich.) at 37°C. For illness bacteria were cultivated at 37°C in BHI broth to MK-2894 late exponential phase (optical denseness at 600 nm 0.8 washed once with phosphate-buffered saline (PBS) suspended in 0.9% NaCl and MK-2894 quantified on BHI agar plates. Bacterial suspensions were then fractioned and freezing at ?70°C until used. (106 CFU) in 100 μl of PBS was injected into the snout (ideal part) of 6- to 8-week-old mice under methoxyflurane (Schering-Plough Union N.J.) anesthesia. Quantification of weight in organs of infected mice. MK-2894 Mice were sacrificed and their brains (including the brain stems) right snouts and right TG were dissected. The cells were floor and lysed with sterile 0.6% Triton X-100 in PBS. The cells lysates were diluted in sterile 0.9% NaCl and 100 μl was plated on duplicate BHI agar plates. CFU from organs of individual mice were counted after over night incubation at 37°C. Immunostaining of cells.