Alteration of the Binding Characteristics of a Recombinant scFv Anti-parathion Antibody - 1. Mutagenesis Targeted at the V H CDR 3 Domain

Abstract

A single-chain variable fragment (scFv) recombinant antibody against the organophosphorous insecticide parathion has been used to generate a set of mutants. Single point mutations were introduced into positions 97-100b of the third complementarity-determining region (CDR) of the heavy chain using oligonucleotide-directed mutagenesis. The mutant scFvs were characterised in an ELISA for parathion and related pesticides. Three groups of clones with altered properties were identified: those which lost all ability to bind to the solid-phase pesticide conjugate in the ELISA; those with reduced binding to the solid phase conjugate, and those with changed ELISA sensitivity to free pesticide. supstitutions into positions 100a and 100b were particularly represented in the first group, indicating that these are either important residues for binding of parathion or that they adversely affect folding of the scFv. The mutation tyrosine to histidine had very different effects depending on the position of the tyrosine in the CDR. The results presented are discussed in the context of the development of strategies for manipulation of antibody binding properties in order to improve ELISA performance.

Keywords:

• Recombinant Antibody
• Scfv
• Mutagenesis
• Pesticides