Phage Display-Derived Binders Able to Distinguish <i>Listeria monocytogenes</i> from Other <i>Listeria</i> Species

<div><p>The objective of this study was to produce phage display-derived binders with the ability to distinguish <i>Listeria monocytogenes</i> from other <i>Listeria</i> spp., which may have potential utility to enhance detection of <i>Listeria monocytogenes</i>. To obtain binders with the desired binding specificity a series of surface and solution phage-display biopannings were performed. Initially, three rounds of surface biopanning against gamma-irradiated <i>L. monocytogenes</i> serovar 4b cells were performed followed by an additional surface biopanning round against <i>L. monocytogenes</i> 4b which included prior subtraction biopanning against gamma-irradiated <i>L. innocua</i> cells. In an attempt to further enhance binder specificity for <i>L. monocytogenes</i> 4b two rounds of solution biopanning were performed, both rounds included initial subtraction solution biopanning against <i>L. innocua</i>. Subsequent evaluations were performed on the phage clones by phage binding ELISA. All phage clones tested from the second round of solution biopanning had higher specificity for <i>L. monocytogenes</i> 4b than for <i>L. innocua</i> and three other foodborne pathogens (<i>Salmonella</i> spp., <i>Escherichia coli</i> and <i>Campylobacter jejuni</i>). Further evaluation with five other <i>Listeria</i> spp. revealed that one phage clone in particular, expressing peptide GRIADLPPLKPN, was highly specific for <i>L. monocytogenes</i> with at least 43-fold more binding capability to <i>L. monocytogenes</i> 4b than to any other <i>Listeria</i> sp. This proof-of-principle study demonstrates how a combination of surface, solution and subtractive biopanning was used to maximise binder specificity. <i>L. monocytogenes</i>-specific binders were obtained which could have potential application in novel detection tests for <i>L. monocytogenes</i>, benefiting both the food and medical industries.</p>