BACTERIAL EXPRESSION AND CHARACTERIZATION OF AN ANTI-DESIPRAMINE SINGLE-CHAIN ANTIBODY FRAGMENT

Tricyclic antidepressant toxicity is a leading cause of death from int entional drug overdose. Monoclonal antibody Fab' fragments specific fo r the tricyclic antidepressant, desipramine, reverse acute drug toxici ty but may themselves have adverse effects at therapeutic doses. To ev aluate the characteristics of smaller antibody fragments, we cloned, e xpressed and characterized a 26 kD single chain Fv fragment (GS-sFv). A DNA sequence encoding V-H-linker-V-L was constructed from hybridoma mRNA encoding a high affinity monoclonal desipramine-specific IgG(1) a nd expressed in E. coli. G5-sFv was produced at high levels as insolub le inclusion bodies. Single chain Fv was solubilized, folded in a redo x buffer and affinity purified on desipramine-Sepharose. The affinity of G5-sFv for desipramine was similar to that of the corresponding mon oclonal Fab' as measured by surface plasmon resonance (Fab' 5.5 +/- 0. 5 x 10(8) M-1, sFv 2.3 +/- 0.5 x 10(8) M-1). G5-sFv administered to ra ts after a tracer dose of H-3-desipramine produced rapid and marked re distribution of drug from tissues into serum. GS-sFv was stable at 4 d egrees C for greater than 6 months but lost activity at higher tempera tures. We conclude that desipramine-specific-single chain Fv expressed in E. coli retains the affinity of the parent antibody for desipramin e. The pharmacokinetic effect of G5-sFv on desipramine distribution su ggests that ii may be useful as an antidote for desipramine overdose. (C) 1997 International Society for Immunopharmacology.