Conclusions The research presented here generated random InlA variants with enhanced invasion into the CT-26 cell line most likely through an increased affinity for mCDH1. Novel mutations in InlA were readily identified from the random mutagenesis approach and a number (including the N259Y mutation) are worthy of find more further study. The approach used here indicates that other random or targeted mutagenesis strategies may uncover mutations that further enhance protein-ligand binding.

In particular we suggest that screening approaches such as biopanning [37] using the first extra cellular domain of mCDH1 as bait or a site-saturation mutagenesis approach (the analysis of all amino acid combinations at a single residue) [38] may uncover further potential interactions. We have demonstrated that the newly created strain, EGD-e InlA m * does not have an enhanced affinity for human cells (unlike the predecessor EGD-InlAm) while displaying highly reproducible oral infections in the mouse model. The use of this murinized L. monocytogenes strain will prove a useful tool in analysing the gastrointestinal phase of listeriosis. The SCH727965 cell line additional residues identified here as playing a role in InlA::CDH1 interactions will inform our ongoing efforts to create

safer ‘murinised’ versions of L. monocytogenes which will help us to combat this often fatal pathogen. Acknowledgements The authors would like to thank Richard O’Kennedy and Stephen Harty for generously supplying the InlA

monoclonal antibody. We would Metalloexopeptidase like to acknowledge the funding received from the Irish Government under the National Development Plan 2000-2006 and the funding of the Alimentary Pharmabiotic Centre by the Science Foundation of Ireland Centres for Science Engineering and Technology (CSET) programme. References 1. Gaillard JL, Berche P, Frehel C, Gouin E, Cossart P: Entry of L. monocytogenes into cells is mediated by internalin, a repeat protein reminiscent of surface antigens from gram-positive cocci. Cell 1991, 65:1127–1141.PubMedCrossRef 2. Bierne H, Sabet C, Personnic N, Cossart P: Internalins: a complex family of leucine-rich repeat-containing proteins in Listeria monocytogenes . Microbes Infect 2007, 9:1156–1166.PubMedCrossRef 3. Mengaud J, Lecuit M, Lebrun M, Nato F, Mazie JC, Cossart P: Antibodies to the leucine-rich repeat region of Vistusertib molecular weight internalin block entry of Listeria monocytogenes into cells expressing E-cadherin. Infect Immun 1996, 64:5430–5433.PubMed 4. Lecuit M, Ohayon H, Braun L, Mengaud J, Cossart P: Internalin of Listeria monocytogenes with an intact leucine-rich repeat region is sufficient to promote internalization. Infect Immun 1997, 65:5309–5319.PubMed 5. Mengaud J, Ohayon H, Gounon P, Mege R-M, Cossart P: E-cadherin is the receptor for internalin, a surface protein required for entry of L. monocytogenes into epithelial cells. Cell 1996, 84:923–932.PubMedCrossRef 6.