Quorum Sensing

Chapter 25

Generation of High-Sensitivity Monoclonal Antibodies

Specific for Homoserine Lactones

Soumya Palliyil

Abstract

A number of bacteria use a class of chemical compounds called acyl-homoserine lactones (AHLs) as quorum
sensing (QS) signals to coordinate their behavior at the population level, including pathogens likePseudo-
monas aeruginosa. Blocking QS using antibodies is an attractive strategy for infection control as this process
takes a central role inP. aeruginosainfections. Here the methods involved in the generation of high
sensitivity anti-QS monoclonal antibodies from an immunized sheep phage display antibody library are
described. A panel of AHL compounds conjugated to carrier proteins are used for sheep immunization and
a phage display antibody library is constructed using the immune repertoire of sheep as a source of antibody
genes. High sensitivity single chain antibody fragments (scFv) are isolated from the library using “smart
selection strategies” and reformatted into single chain antibodies (scAbs). The resultant monoclonal
antibodies: (1) recognize HSL compounds at low nanomolar concentrations; (2) have the potential to
reduce virulence gene expression inP. aeruginosa; and (3) offer protection in a nematode model of
infection.

Key wordsPseudomonas aeruginosa, Quorum sensing, Acyl-homoserine lactones, Monoclonal anti-

bodies, Anti-infective antibodies

1 Introduction

Many Gram-negative bacteria rely on acyl-homoserine lactones

(AHLs) as QS signal molecules [1, 2]. The human pathogenPseu-

domonas aeruginosahas two AHL-dependent QS systems: thelas

and therhlsystems, relying onN-3-oxododecanoyl-homoserine

lactone (3OC 12 -HSL) and N-butyryl-homoserine lactone (C 4 -

HSL) as signal molecules, respectively [3]. These molecules posi-

tively control the expression of extracellular virulence factors asso-

ciated withP. aeruginosainfection and biofilm formation [3]. The

extracellular distribution of QS signals like AHLs make them ideal

targets for anti-infective therapy since the evolutionary pressure on

bacteria to develop resistance will be limited [2]. Monoclonal anti-

body mediated inhibition of the QS process may offer exquisite

Livia Leoni and Giordano Rampioni (eds.),Quorum Sensing: Methods and Protocols, Methods in Molecular Biology,
vol. 1673,https://doi.org/10.1007/978-1-4939-7309-5_25,©Springer Science+Business Media LLC 2018

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