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 like Pseudomonas aeruginosa. Blocking 
QS using antibodies is an attractive strategy for infection control as this 
process takes a central role in P. aeruginosa infections. 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 in P. 
aeruginosa; and (3) offer protection in a nematode model of infection.