EXPRESSION AND CHARACTERIZATION OF SINGLE-CHAIN ANTIBODY FRAGMENTS PRODUCED IN TRANSGENIC PLANTS AGAINST THE ORGANIC HERBICIDES ATRAZINE AND PARAQUAT

Single-chain antibody fragments (scAbs), which have a human C-kappa co nstant domain and a hexa-histidine tail attached to the carboxy termin us of the single-chain Fv (ScFv) fragments to facilitate purification, have been raised against the herbicides paraquat and atrazine and exp ressed in transgenic Nicotiana tabacum cv, Samsun NN, Prior to purific ation, the anti-atrazine scAb is expressed as up to 0.014% of soluble leaf protein and has a binding profile in ELISA, against an atrazine-b ovine serum albumin (BSA) conjugate, similar to that of the scAb produ ced in Escherichia coli, Competition ELISA has shown that the plant-de rived scAb also recognises free atrazine. Following antibody affinity purification to isolate dimers, the affinity for immobilised antigen a pproaches that of the parental monoclonal antibody. This was confirmed by surface plasmon resonance analysis. The purified scAb also recogni ses related triazine herbicides. When isolated from cell-suspension cu ltures, the anti-paraquat scAb binds to a paraquat conjugate in a conc entration-dependent manner, with a profile similar to the parental mon oclonal antibody. This is the first demonstration that functional scAb s against organic pollutants can be produced in transgenic plants and that the scAbs may be appropriate for the development of immunoassay-b ased detection systems. (C) 1998 Elsevier Science B.V. All rights rese rved.