Further improvement of broad specificity hapten recognition with protein engineering

Sulfa-antibiotics (sulfonamides) are widely used in veterinarymedicine. Meat and milk from treated animals can be contaminatedwith sulfa residues. Current sulfonamide assays are unfit forscreening of food, because they are either too laborious, insensitiveor specific for a few sulfa compounds only. An immunoassay fordetection of all sulfas in a single reaction would be usefulfor screening. Previously we have improved the broad specificitysulfa binding of antibody 27G3 with random mutagenesis and phagedisplay. In order to improve the properties of this antibodyfurther, mutants from the previous study were recombined andmore mutations introduced. These new libraries were enrichedwith phage display and several different mutant antibodies wereisolated. The cross-reaction profile of the best mutant wasbetter than that of the wild-type antibody and the mutants ofthe previous study: it was capable of binding 10 of the tested13 sulfonamides within a narrow concentration range and alsobound the rest of the sulfas 5- to 11-fold better than the mutantsof the previous study.