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
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