strain displayed a slight reduction (not statistically significant) in invasion compared to EGD-e, while over expression of InlA resulted in a modest increase in invasion. We speculate that this is due to a reduced affinity of InlA for mCDH1, however we have not assayed for mCDH1 production by CT-26 cells. Figure 2 InlA dependent invasion of EGD-e derrived strains into human (Caco-2: grey bars) or murine (CT-26: white bars) monolayers. Exponential phase L. monocytogenes cells (OD = 0.8) were Luminespib invaded (MOI of 25:1) in triplicate for 1 h before overlaying with gentamicin. Invasion was expressed as the average cfu count per well (with standard deviation) or invasion relative to EGD-e (below graph) (n = 3). The graph is representative of the data from three independent experiments. Heterologous expression
was then employed to distinguish InlA from additional virulence determinants on the surface of the L. monocytogenes. We chose to use the well characterized nisin inducible expression system  (Figure 1) to produce full length InlA on the surface of L. lactis. The system was chosen because production of functional STI571 mw InlA on the cell surface of L. lactis had previously been documented . We compared the entry of L. lactis containing vector only (L. lactis-pNZB), producing wild type InlA (L. lactis InlAWT) or producing InlA containing the Ser192Asn and Tyr369Ser, but with different codon usage to the previously described murinized InlAm  (L. lactis InlA m *) into Caco-2 and CT-26 cells. The presence of InlA on the cell
surface was confirmed by Western blot analysis (Figure 1b). The level of Carbohydrate invasion for L. lactis-pNZB into Caco-2 cells is similar to that observed for EGD-eΔinlA (Figure 2 and 3). As L. lactis is non invasive, the surviving bacterial cells probably represent bacteria not killed by the gentamicin treatment rather than internalized cells, as documented previously . A similar level of entry into Caco-2 cells was observed for L. lactis InlAWT and L. lactis InlA m *, while entry into CT-26 cells was 27-30 fold greater for L. lactis InlA m * compared to L. lactis InlAWT (Figure 2). Figure 3 Invasion of L. lactis expressing wild type or murinized InlA into Caco-2 (grey bars) or CT-26 (white bars) monolayers. Nisin induced L. lactis cells were invaded (MOI of 25:1) for 1 h before overlaying with gentamicin. Invasion was expressed as average cfu count (with standard deviation) or invasion relative to L. lactis plasmid only (below graph) (n = 3). The graph is representative of the data from three independent experiments. In contrast to a previous report , we observed an increased invasion into a murine cell line by the L. monocytogenes strain over-expressing InlAWT in contrast to the plasmid only control (Figure 2).