Bacterial and firefly luciferases have different peak emission le

Bacterial and firefly luciferases have different peak emission length of 410 nm and 610 nm, respectively [30]. Importantly compared to the bacterial luciferase, the firefly

luciferase has stronger light emitting activity and can be separately measured in vivo by BLI after systemic administration of its substrate luciferin. BLI signals from the bacterial luciferase can then be subtracted from firefly BLI signals for solely quantification of Ifnb1 induction levels. One day after inoculation with Lmo-InlA-mur-lux or Lmo-EGD-lux we detected the first firefly luciferase Selleckchem Tucidinostat signals in the spleen and cervical lymph nodes (Figure 6B) as described previously for an intravenous Listeria infection model [24]. At this timepoint, light signals from replicating bacteria were not yet

visible (Figure 6A). Host bioluminescent signals had similar intensities in Lmo-InlA-mur-lux find more and Lmo-EGD-lux infected IFN-β-reporter mice at 24 h p.i., although two out of five Lmo-InlA-mur-lux infected animals showed a more intensive induction of the IFN-β-reporter compared to Lmo-EGD-lux infected animals (Figure 6B). At 2 d.p.i., IFN-β reporter signals in mice infected with either bacterial strain were further increased and then also detectable in the intestine and the liver. The intensities of the firefly luciferase signals increased further at days 3 and 4 p.i. and became more pronounced in Lmo-InlA-mur-lux infected mice as compared to Lmo-EGD-lux infected animals (Figure 6B and C). At 5 d.p.i., two Lmo-InlA-mur-lux and one Lmo-EGD-lux infected mice which had displayed high IFN-β reporter signals on earlier timepoints of the infection developed severe listeriosis (Figure 6B) and succumbed to the infection or had to be euthanized for ethical reasons. This demonstrated, in line with previous studies, that high levels of IFN-β production are associated with elevated mortality rates in listeriosis [31, 32]. Overall, in the Lmo-InlA-mur-lux infected experimental cohort, 3 out of 5 mice succumbed to the infection TEW-7197 mw whereas in the Lmo-EGD-lux experimental cohort only 1 animal out of 5 did not survive the infection. This demonstrated, in line HAS1 with previous

studies, that high levels of IFN-β production are associated with elevated mortality rates in listeriosis [31, 32]. Thus, taken together murinised Listeria induces higher levels of IFN-β in orally challenged mice compared to non-murinised Listeria. Figure 6 Oral infection challenge with murinised Lmo-InlA-mur-lux is associated with elevated IFN-β induction. Albino IFN-β-reporter (Ifnb1 tm2.2Lien ) mice on a C57BL/6J genetic background were infected intragastrically with 5 × 109 CFU Lmo-EGD-lux or Lmo-InlA-mur-lux (n = 5). At the indicated timepoints, mice were first analysed for dissemination of bioluminescent L. monocytogenes as described for Figure 1 (A) and then subsequently i.v. injected with luciferin and monitored for firefly luciferase activity as a reporter of IFN-β induction (B), see Methods.

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